98 D1 V8 bad fuel economy - 43.2L per 100km - vacuum advance?

[twr7cx]

My father recently purchased a stock standard 98 D1 SE V8 with 115,000km on it. He has a work car for Monday to Friday so it doesn’t get used much but we’ve found the fuel economy to be ridiculously high and testing confirmed it at around 43.2L for 100km. This is an issue both expense wise but also as the tanks range is so limited.

So far I have changed all fluids (engine oil and filter, automatic transmission filter and fluid, transfer box, front and rear diff oils), changed the spark plugs (NGK standards gapped according to Rave), the air filter and replaced two ignition leads which had damaged plug boots.

While there I found the vacuum line to the distributors vacuum advance to have perished at the boots and the suck test indicated that the diaphragm had an issue.

A new vacuum advance unit is on its way, would this be the sole cause for such poor fuel economy? Or is there other areas that I should check? We are aiming to get it to a more reasonable 20L per 100km range which I think is reasonable...

[loanrangie]

Possibly the amplifier as well, there is a good guide here on how to replace with a bosch item.

[AK83]

When you're self diagnosing like this(which many of us do) it's best to do change things one at a time and test.

Everything you've done so far seems well thought out too.

The other thing to check for once the vac advance is fitted, will be the air flow meter/sensor.

On all the injected Rover(SD1) vehicles I've had they were all playing up. Damned expensive things to change back then too!
Other thing to be mindful of are the injectors themselves, they get dirty/worn and the spray pattern is fubar.

[twr7cx]

The other thing to check for once the vac advance is fitted, will be the air flow meter/sensor.

On all the injected Rover(SD1) vehicles I've had they were all playing up. Damned expensive things to change back then too!

Is there a way to test them or matter of fitting another to see if there’s an improvement? Can they be cleaned first?

Is there oxygen sensors on these?

[AK83]

Is there a way to test them or matter of fitting another to see if there’s an improvement? Can they be cleaned first?

Is there oxygen sensors on these?

Unfortunately my only experience with injected RV8's has been with SD1's.
(although soon will have my D2 V8 on the road too).

As for injectors, I had a few piled up over the years, and bought some more.
My mechanic had the tester cleaner doodad tool and due to the difficult installation(for me), I got him to test/clean them all and install the good ones.

Do plenty of research on the topic, as I think I remember reading recently(not back then when I had my RV8s!!) that some fords used the same injector types .. so could be an alternative if prices are lower.

Also have you checked if your dads D1 has O2 sensor(s) too?

[twr7cx]

Possibly the amplifier as well, there is a good guide here on how to replace with a bosch item.

Thanks. I assume this is what you refer to Lucas ignition amplifier replacement by Bosch 024 (https://www.aulro.com/afvb/technical-chatter/96950-lucas-ignition-amplifier-replacement-bosch-024-a.html) ?

Is there any way to test the current one? We don’t seem to be having the back firing etc issues that others mention in that thread.

[Old Farang]

Could be the cold start sensor is stuffed. ETC8496. There are 2 similar sensors that are screwed into the intake manifold, so you need to check the correct one. Depending how it may have failed, it will cause high fuel consumption as the engine will be running rich all the time.

[justinc]

Is it getting hot quickly? Sounds like it is still in warm up program... thermostat needs to open quickly. At least 82degree one.

Set timing to 10deg or even 12 if vac advance iffy. Also check that the fpr is not perforated this will draw extra fuel in to the inlet manifold.

Jc

[twr7cx]

Cheers JC.


Is it getting hot quickly? Sounds like it is still in warm up program... thermostat needs to open quickly. At least 82degree one.

Will check. What sort of time frame should it be taking to get to normal operating temperature? Is he factory dash guage sufficient for judging this?


Set timing to 10deg or even 12 if vac advance iffy.

is that advance BTDC?


Also check that the fpr is not perforated this will draw extra fuel in to the inlet manifold.

Is it the same method as checking the condition of the diaphragm for the distributors vacuum advance module - ie connect a vacuum hose up and suck on it?

EDIT: found V8 Fuel Pressure Regulator symptoms? (https://www.aulro.com/afvb/discovery-1-a/187303-v8-fuel-pressure-regulator-symptoms.html) which provides some related information.

[twr7cx]

From another thread:


Remember to check your vacuum and mechanical advances are working properly, loss of either will ruin your economy.

As mentioned above I’ve checked and found the fault with the vacuum advance but how does one check the mechanical advance?

[twr7cx]

Could be the cold start sensor is stuffed. ETC8496. There are 2 similar sensors that are screwed into the intake manifold, so you need to check the correct one. Depending how it may have failed, it will cause high fuel consumption as the engine will be running rich all the time.

Thanks. Any guidance on how to check that sensor?

[Old Farang]

Thanks. Any guidance on how to check that sensor?
I posted about it previously, just can't find it at the moment.

[Old Farang]

I posted about it previously, just can't find it at the moment.
Here tis:

1993 Discovery High fuel consumption (https://www.aulro.com/afvb/technical-chatter/255121-1993-discovery-high-fuel-consumption.html)

[twr7cx]

Here tis:

1993 Discovery High fuel consumption (https://www.aulro.com/afvb/technical-chatter/255121-1993-discovery-high-fuel-consumption.html)

Thank you, will read now.

[bee utey]

As mentioned above I’ve checked and found the fault with the vacuum advance but how does one check the mechanical advance?

Get yourself a cheap timing light, you'll need it for the idle timing in any case. Timing should advance with revs. Also remove the distributor cap and see that the rotor freely moves against the advance springs. Don't pull on the rotor button without reading this thread first:

Lucas V8 dissy nylon clip repair method. (https://www.aulro.com/afvb/technical-chatter/116123-lucas-v8-dissy-nylon-clip-repair-method.html)

[twr7cx]

Thanks. Any guidance on how to check that sensor?

The answer for testing the temperature sensor for cold start from 1993 Discovery High fuel consumption (https://www.aulro.com/afvb/technical-chatter/255121-1993-discovery-high-fuel-consumption.html) is:


Also check the 2 wire plug on the temp sender at the front of the inlet manifold, this should read around 300 ohms with a warm engine. Note that this isn't the 1 wire sender for the dash gauge, that's next to the 2 wire one.




The Coolant Temperature Sensor should change resistance with heat, per the following specs:

- 10 c ....................9,100 - 9,300 ohms



0 c.........................5,700 - 5,900 0hms
20 c.......................2,400 - 2,600 ohms
40 c.......................1,100 - 1,300 ohms
60 c........................500 - 700 ohms
80 c........................300 - 400 ohms
100 c.......................150 - 200 ohms


The Coolant Temperature sensor is used to enrich the fuel mixture whenthe engine is cold. These devices almost always fail open-circuit, which makesthe injection system believe that the engine is at somewhere around–40 degrees Centigrade. The system will always detect this as a faultcondition, and use a substitute value of 30 degrees Centigrade whilstsetting a fault code in the ECU. In practice, thismeans that the car will be difficult to start when cold (too lean), andwill be too rich when warmed up. However, it will usually get home!
.................................................. .....................................
These sensors are still available and not expensive. p/n: ETC8496. If a faulty sensor is replaced it will be necessary to clear the fault in the ECU either by unplugging it, or disconnecting the battery for a few seconds.

[twr7cx]

Also check that the fpr is not perforated this will draw extra fuel in to the inlet manifold.

I pulled the vacuum hose off the FPR. No signs of fuel in the hose. Put a known good hose on and sucked and it holds the vacuum so I assume that he diaphragm is not perforated. The hose looked a bit old with some cracks in the rubber so I have replaced it.


Is it getting hot quickly? Sounds like it is still in warm up program... thermostat needs to open quickly. At least 82degree one.

Spoke to the old man and he tells me that it’s not heating up. It sits on the very bottom of the ‘normal’ temperature range indication just above the C.

https://www.aulro.com/afvb/

He towed the boat (5.2m fibreglass half cab with 115HP) up the Southern Outlet. The vehicle was very underpowered and he had to drop it back gears and give it gas. He was worried about the temperature with it reving so high towing a load up such a steep incline but the temperature gauge on the dash didn’t get off the bottom of the ‘normal’ temperature range mark.

So how do I get the car to get hot?

[bee utey]

So how do I get the car to get hot?

New thermostat.

[justinc]

Yup. Thermostat is stuck open . I think i have the right one at work. I can drop it outside the gate for you in the morning i have to drop in quickly. Ill txt you when ive been down there.


Jc

[Young Angus]

Wow...don't suppose you've checked for leaks in the fuel tank or lines have you? Had to ask [emoji16]

[justinc]

Wow...don't suppose you've checked for leaks in the fuel tank or lines have you? Had to ask [emoji16]

😅😅 you diesel boys have no idea how bad it can get😎😅

[twr7cx]

Wow...don't suppose you've checked for leaks in the fuel tank or lines have you? Had to ask [emoji16]

That probably would have been a simpler to find issue!

I put the fuel economy in the title as otherwise I figured the first reply I would receive would be "of course it is, it's a V8" or something to that effect.


On a side related note - do these things benefit from the MAF being cleaned?

I read that there is a idle mixture adjustment screw on the MAF, out of interest, whats the process for tuning this?

[chillman]

On a side related note - do these things benefit from the MAF being cleaned?


I found it made a difference on mine. Only get "MAF Cleaner" nothing else.

If you're towing, I also recommend the Tornado chip if you can afford it. Chip, service (plugs, leads, dizzy cap, rotor, vacuum advance unit, air filter) and 10-12 degrees of advance, it now tows way better. I'm getting 22l per hundred, down from 35 per hundred around town.

[justinc]

That probably would have been a simpler to find issue!

I put the fuel economy in the title as otherwise I figured the first reply I would receive would be "of course it is, it's a V8" or something to that effect.


On a side related note - do these things benefit from the MAF being cleaned?

I read that there is a idle mixture adjustment screw on the MAF, out of interest, whats the process for tuning this?

At operating temp and idling, stick multimeter probes one in each wire at the furtgest outer ports left and right of the maf plug. Dc volt setting you need to see about 1 to 1.1v. Turning the screw clockwise increases the voltage, decrease antixlockwise. Higher the number tge richer it is

[Young Angus]

😅😅 you diesel boys have no idea how bad it can get😎😅

Haha it was a genuine suggestion...well, I was having a bit of a chuckle while I wrote it but before I owned my Tdi I owned a '98 V8 Disco and for the life of me I can't remember it being anywhere near that thirsty.

[John R]

Assuming you Disco 98 has fuel injection - May I suggest you look at the performance of the O2 sensors and the MAF. I've recently had issues on my 2001 V8 with performance and fuel consumption. Both fixed when I dealt with these components. BTW I've never had a consumption figure at 42l/100K. The worst I've had is 22l/100K

Are you sure the hand brake is fully released or that you don't have binding calipers - all obvious I guess.

All the best.

[trout1105]

Just out of curiosity what is the MAF reading supposed to be on a 4l V8 at idle?

[twr7cx]

Assuming you Disco 98 has fuel injection - May I suggest you look at the performance of the O2 sensors and the MAF. I've recently had issues on my 2001 V8 with performance and fuel consumption. Both fixed when I dealt with these components.

I believe that the D2 and D1 V8 fuel systems are significantly different. I don't recall noticing oxygen sensors on the D1 and a quick Google search seems to indicate that they didn't have them.


Are you sure the hand brake is fully released or that you don't have binding calipers - all obvious I guess.

No signs of excess heat on any of the components to indicate seized items.

[Tomnahurich]

Is the engine down on power? Have you had any signs that the engine may have cooked at some stage?

After checking the obvious (MAF, VA, Rad/coolant/ fuel/oil filter etc) and if no improvement then generally this begins to point at some blow by in the system and fingers crossed not, but could be an issue with losing compression via worn rings, valve guides / valve stems or even a blown or near blown head gasket.......which means getting down there re-building.

The Buick is a very simple engine on these V8's with no Lambda (Oxygen) so it wont be that either.

It's not uncommon for these engines to run very rich and are susceptible to a heavy right foot too, around 20-25/100 is achievable on the open road with a tail wind, more like 25-30 or worse more around town.

A wise man once quoted a proverb on this forum "V8 go past everything except petrol station". Consider getting LPG conversion off a wreck if you're trying to save cash...

[Staffy]

Engine timing is important on these. Not advanced enough and you’ll suck a ton of fuel. Sounds like time for the strobe.

[Rick1970]

Worth checking/replacing coolant temp sensor for the efi. Usually very low on power and black smoke when they fail. But if it’s not getting up to operating temp, will chew some fuel. I have half radiator covered in winter to get temps up, even after replacing thermostat. Also worth checking that tdc on balancer is true, mine is out.

[James NZ]

Hi guys,
the fuel consumption figures that have been mentioned seem rather high to me. We have owned our '95 D1 V8 since 2012 and have averaged 18.9l/100km over the time we have owned it. Best figure was 13.8l/100 and worse was 31.5l/100. Does the OP have Rovergauge, its a useful bit of software for the D1. Also our car does have oxy sensors and did have cats as well. Cats are long gone. Unfortunately I've just been told to hurry up (we are going out) but google search and you may find some intering info from Mark (cant remember his last name) he's written a fairly good guide. Plus the good info here should sort it. I also think you should check the mechanical soundness as well.

Cheers, James NZ

[LRT]

I got 52L/100km when the coil packs died on the D2 V8 so I'd say an ignition issue as others have said.

Edit: Since changing the packs and leads it now varies between 13L/100km on long distance trips to 19L/100km towing a 2 ton trailer.

[Redfoxie]

Remove the line from the manifold to the vac advance. Suck on it and hold the vacuum with your tongue. If it the suction holds it's fine and time a timing light tune.
if not it's buggered and most the fuel in your tank will pour out the exhaust. Low power and rubbish sounding engine.
careful of cheap eBay jobs when buying the new unit. I had 2 fail instantly.
check all other vacuum leaks and ensure the manifold is connected perfectly to the MAF.
clean the MAF with cleaner as suggested.
economy should be down around the 16-18 litres per 100km.

then ****fart around with all the other bits and bobs. (O2 sensors temp sense etc.)

[Redfoxie]

Remove the line from the manifold to the vac advance. Suck on it and hold the vacuum with your tongue. If it the suction holds it's fine and time a timing light tune.
if not it's buggered and most the fuel in your tank will pour out the exhaust. Low power and rubbish sounding engine.
careful of cheap eBay jobs when buying the new unit. I had 2 fail instantly.
check all other vacuum leaks and ensure the manifold is connected perfectly to the MAF.
clean the MAF with cleaner as suggested.
economy should be down around the 16-18 litres per 100km.

then ****fart around with all the other bits and bobs. (O2 sensors temp sense etc.)


How is P I S S a swear word but not fart?

[twr7cx]

Also worth checking that tdc on balancer is true, mine is out.

What's the method for this?

[Rick1970]

What's the method for this?

Dial indicator with extension to reach piston crown is the nice way.....

I made up a dummy spark plug with a rod welded into it, just long enough to reach piston crown before TDC. Remove all plugs (just to make it easier to turn over), dummy plug in No1, gentlyeturn over with socket and extension bar, mark balancer when you feel piston touch, rotate opposite direction and mark again. Mid point between marks is TDC.

[twr7cx]

Replaced the thermostat and gasket this afternoon. The temperature gauge now gets up to the half way mark.

As a bonus I found the disconnected vacuum hose for the vacuum operated cruise control, reconnected it and the cruise control works.

Next up when I get some time is to replace the vacuum advance unit on the side of the distributor < https://www.aulro.com/afvb/discovery-1-a/259254-98-d1-v8-distributor-vacuum-advance-replacement.html#post2777308 > and check/set the timing, idle and MAF.

[DiscoTwoV8]

My father recently purchased a stock standard 98 D1 SE V8 with 115,000km on it. He has a work car for Monday to Friday so it doesn’t get used much but we’ve found the fuel economy to be ridiculously high and testing confirmed it at around 43.2L for 100km. This is an issue both expense wise but also as the tanks range is so limited.

So far I have changed all fluids (engine oil and filter, automatic transmission filter and fluid, transfer box, front and rear diff oils), changed the spark plugs (NGK standards gapped according to Rave), the air filter and replaced two ignition leads which had damaged plug boots.

While there I found the vacuum line to the distributors vacuum advance to have perished at the boots and the suck test indicated that the diaphragm had an issue.

A new vacuum advance unit is on its way, would this be the sole cause for such poor fuel economy? Or is there other areas that I should check? We are aiming to get it to a more reasonable 20L per 100km range which I think is reasonable...

I'm running a bog standard Disco Two V8 4L automatic, cruise control, standard tyres. I run it on 98 RON, and get between 600 and 700 km's to the tank, this is driving at speed limits (including 110 zones) with a half roof rack, bullbar, load etc. 20l per 100kms seems a lot of fuel, I get around 15l/100km, and better if I'm just crawling around at lower speeds (say 80 km/h). I don't stand on the load pedal too much, unless I put it in sport to overtake a road train or something.
It sounds like I have the same spark plugs etc, but I replaced all the leads a while back (pain in the ...., but you can do it by loosening a few bolts, having a diagram, and leaning over the motor - don't need to take everything apart).
Good luck.
I

[DiscoTwoV8]

Replaced the thermostat and gasket this afternoon. The temperature gauge now gets up to the half way mark.

As a bonus I found the disconnected vacuum hose for the vacuum operated cruise control, reconnected it and the cruise control works.

Next up when I get some time is to replace the vacuum advance unit on the side of the distributor < https://www.aulro.com/afvb/discovery-1-a/259254-98-d1-v8-distributor-vacuum-advance-replacement.html#post2777308 > and check/set the timing, idle and MAF.

Just out of curiosity is the cruise control the same on the Disco 1 & 2 V8 auto? Mines a pain in the ... to set, have to hold it a while, at the speed, to get it to take at that speed. If I just click it on it sets itself about 7km/h lower ... any idea?

[twr7cx]

Vacuum advance unit replaced on the distributor today. Two of the ignition leads seem to have been in the wrong place on the distributor cap originally... Timing set to 10* BTDC. Confirmed that both the mechanical and vacuum advances work while had the timing light out.

Fuel tank refilled to test what the economy is now like. Initial test drive has the vehicle with more response and poke.

Next up will be to check the MAF voltage and adjust if required an the coolant temperature sensor resistance test.

[Bundy]

What happened can you let us know.

Paul

[twr7cx]

Some significant improvements:
21L per 100km driving around
24L per 100km towing a 1.5t boat and passengers on the highway.

Vehicle gets up to operating temperature now.

Of note is that the exhaust pipe to the main muffler have seperated so might be having an effect until repaired.

Havnt checked the temperature sensor resistance (Ohms) yet, still need to figure out where it is located on the engine.

Also haven’t checked out the MAF voltage or adjust the screw adjustment on it. Wasn’t sure how to get the voltage reading from it - need to break the insulation on the wiring to get a multimeter probe I guess?

So maybe some further gains to be had?

[bee utey]

Some significant improvements:
21L per 100km driving around
24L per 100km towing a 1.5t boat and passengers on the highway.

Vehicle gets up to operating temperature now.

Of note is that the exhaust pipe to the main muffler have seperated so might be having an effect until repaired.

Havnt checked the temperature sensor resistance (Ohms) yet, still need to figure out where it is located on the engine.

Also haven’t checked out the MAF voltage or adjust the screw adjustment on it. Wasn’t sure how to get the voltage reading from it - need to break the insulation on the wiring to get a multimeter probe I guess?

So maybe some further gains to be had?

ECU temp sender is really easy to find, look at the inlet manifold just behind the top radiator hose, there will be a vertical two wire plug on a sender that's screwed into the front water passage between the passenger side head and the back of the thermostat.

MAF readings require you to pull back the rubber boot off the connector plug, terminals are then easy to access with a pointed probe.

[twr7cx]

Thanks. I'll try and get onto both this weekend. Have had only very limit short opportunities to look at it so far.

[twr7cx]

JC checked the MAF reading for me the other day all good. Advised that the temp sensor should be fine too as he checked it previously and the temperature gauge is working fine.

Car doesn't love short trips - drinks a lot for these. But longer journeys and towing it's reasonable.

I will say that the Rover V8 is one of the nicest sounding V8's. I've had a few Ford Windsors and Clevelands previously but the Rover V8 seems to even sound great with the stock standard tiny straw of an exhaust.

[bee utey]

They do drink when cold, the cold enrichment is one of the issues and you can't really avoid that. Having a new thermostat helps the engine warm up quickly though. I'm currently doing a few jobs on a D1 V8 to get it to run better on petrol (and LPG) and the number of small things I've found definitely add up. TPS was buggered, the fuel pressure reg had been hooked up to the wrong port, the plugs and leads were stuffed, the vacuum advance was stuffed, timing was wrong etc. The previous "technician" had just replaced the MAF at vast expense, the old one turned out to be perfectly fine and went back on. In the end though there is a price to be paid for the sound of a low compression LRV8 being stoked into song and that's expected.

[PhilipA]

JC checked the MAF reading for me the other day all good. Advised that the temp sensor should be fine too as he checked it previously and the temperature gauge is working fine.
The temperature gauge has a different sender to the ECU sensor.
The ECU sensor tells the ECU what it thinks the engine temperature is.
If too much resistance then cold enrichment.
Regards Philip A

[Rick1970]

As Philip said, check the sensor, the gauge means nothing to the ecu. Check the actual running temp with a known good gauge if you can, not the gauge on the dash. Economy can change dramatically between 70 and 85 deg running temps....

[Old Farang]

I will say that the Rover V8 is one of the nicest sounding V8's. I've had a few Ford Windsors and Clevelands previously but the Rover V8 seems to even sound great with the stock standard tiny straw of an exhaust.
Exhaust note depends on the V8 firing order, and hence the gas pulses through the system.

Rover: 1-8-4-3-6-5-7-2 (and the old Ford flat head!)

Ford 302: 1-5-4-2-6-3-7-8
Ford 351: 1-3-7-2-6-5-4-8

Holden(not all): 1-2-7-8-4-5-6-3

There are many more to trap young players. Some distributors of old also rotate in different directions.

[bee utey]

Exhaust note depends on the V8 firing order, and hence the gas pulses through the system.

Rover: 1-8-4-3-6-5-7-2 (and the old Ford flat head!)



And small block Chev...

[justinc]

[/I]The temperature gauge has a different sender to the ECU sensor.
The ECU sensor tells the ECU what it thinks the engine temperature is.
If too much resistance then cold enrichment.
Regards Philip A



Did both Phillip , i have a touchscreen rovacom tablet with 14CUX capabilities. Real time screen gives me everything even lambda outputs however not req as you know in Aus.

Jc

[ggrupea]

So far I have changed all fluids (engine oil and filter, automatic transmission filter and fluid, transfer box, front and rear diff oils), changed the spark plugs (NGK standards gapped according to Rave), the air filter and replaced two ignition leads which had damaged plug boots.


DId you try changind O2 sensors. I had the same problem and I change O2 Sensors and MAF. That resolve my issue.

[bee utey]

DId you try changind O2 sensors. I had the same problem and I change O2 Sensors and MAF. That resolve my issue.

No O2 sensors on a D1 sold new in Australia.

[twr7cx]

The economy is better than when I started the thread - for my old man it's about 25L per 100km on short trips - 4 to 8km type length. Towing the boat on the highway achieved 21L per 100km. I borrowed the vehicle for a week to commute to and front work (trips of 15km to 25km in length) and achieved 19.84L per 100km which is an effective tank range of around 360km. Not great but better than 43.2L per 100km where we started!

This is on normal unleaded 91 from United Petroleum. Might be interesting to see if Premium or E10 makes a difference?

What we did to improve it is in the posts previously, but in summary:
Replaced all spark plugs
Replaced two ignition leads
Replaced fuel filter
Cleaned MAF sensor with CRC MAF Cleaner
Checked MAF sensor voltage reading
Replaced thermostate
Adjusted timing
Replaced vacuum advance unit
Replaced vacuum advance vacuum hoses
JC had previously checked the temperature sensor readings

[DAMINK]

The economy is better than when I started the thread - for my old man it's about 25L per 100km on short trips - 4 to 8km type length. Towing the boat on the highway achieved 21L per 100km. I borrowed the vehicle for a week to commute to and front work (trips of 15km to 25km in length) and achieved 19.84L per 100km which is an effective tank range of around 360km. Not great but better than 43.2L per 100km where we started!

This is on normal unleaded 91 from United Petroleum. Might be interesting to see if Premium or E10 makes a difference?

What we did to improve it is in the posts previously, but in summary:
Replaced all spark plugs
Replaced two ignition leads
Replaced fuel filter
Cleaned MAF sensor with CRC MAF Cleaner
Checked MAF sensor voltage reading
Replaced thermostate
Adjusted timing
Replaced vacuum advance unit
Replaced vacuum advance vacuum hoses
JC had previously checked the temperature sensor readings

Under 20 and your doing well if you ask me.
I have tried all of the above and more on my d1 v8 and still get bad numbers. Something i decided just is.

[PhilipA]

I can only suggest a couple of other checks.
1 Check that the TPS reads less than AFAIR .49 volts at idle. It has to be under that for override injector cutoff to work over 1500RPM.
2 Check the centrifugal advance by turning the rotor a bit and seeing that it springs back.
3 Check the OHMS of the fuel temperature sensor on the rail.
4 Check that the Fuel pressure regulator diaphragm is intact by sucking on it. Check that the little housing on the back of the manifold is tight, and that there are no splits in the hose to the fuel pressure regulator. It might be worthwhile to fit a new FPR.

Although you say the temperature sensor has been checked ,was it the correct one? The temp sensor for the ECU is a two terminal one near the RH front injector. Sometimes the injector for that cylinder and the temp sensor terminals can be mixed up. They are different colours AFAIR. You would have a miss but with 8 cylinders you sometimes don't notice a miss. The single terminal sensor is only for the gauge.

Also check that all injector plugs have continuity as the wires can break inside the loom. If one is broken you can just tee off the next one along as they batch fire.
From my 91 RRC you should get about 20Lper100km around town and 17 or better on the highway .
Regards Philip A

[twr7cx]

A quick update, almost nine months after this thread started. Borrowed the old mans D1 V8 again for the past few weeks and have been achieving around 17.61L per 100km commuting to and from work which is about 28km away from home each way. Brother used it to travel up the coast (around 600km round trip) and claims he got as low as 16L per 100km. So were a long way better than where it started! A little bit sad that achieving this still horrendous economy gets me excited but the noise of it does sometimes make me consider owning my own Rover V8...

[twr7cx]

+
Vacuum advance unit replaced on the distributor today.

Got less than 19 months and only around 6,000km out of new replacement vacuum advance unit I fitted back on 25 February 2018. Fuel economy has pushed back out to 19.6L/100km as a result. It was a Powerspark unit from the UK that came recommended. It seems that I’m not the first to have this issue:


Ok it's been a mission but I solved it.

The silver bullet was the vacuum advance unit. It just took me a few shots:

3 faulty vacuum advance units later... the one on the dizzy was busted so replaced with recommended eBay job. Seemed to run better at first but after 80 kms of driving it proved no better so went hunting again, nothing obvious so I sucked on the vacuum advance line and it had failed!!
got it replaced free of charge from the UK supplier, new unit went on. Ran better, fuel gauge dropped slower first 30 litres took me 160kms better but not the best fix. Next 30litres got me only 130 kms again, went straight to the vacuum advance unit... failed!!!!

I took to the spare first failure with a tin opener and discovered that in the process of making these items, the diaphragm was crimped too tight on one side and made the joint too thin... so the vacuum just tore it....
out with the silicone, clamped it up installed it and hey presto my little 30litre tank gets me 200kms... even towing a trailer.

So if you have fuel consumption of 20l per 100 kms, check the Vacuum advance unit. An instant fix (if you buy a good replacement) down to 15l per 100kms.

talk about a simple thing made hard.
1993 Discovery High fuel consumption (https://www.aulro.com/afvb/technical-chatter/255121-1993-discovery-high-fuel-consumption-2.html)


I’m now seeking a suitable good quality replacement of diaphragm for rebuilding < RTC3201 VACUUM ADVANCE UNIT 2 PIN DISTRIBUTOR 3.5/3.9 EFI - a reliable brand? Replace (https://www.aulro.com/afvb/technical-chatter/274107-rtc3201-vacuum-advance-unit-2-pin-distributor-3-5-3-9-efi-reliable-brand-replace.html) >.


In the interim I might advance the timing out to 12* as per JC’s earlier advice:


Set timing to 10deg or even 12 if vac advance iffy.

[Bundy]

Have you tried these guys Advance Diaphragm Options - Home | Facebook (https://www.facebook.com/AdvanceDiaphragmOptions/)

They rebuild the genuine Lucas which is better made than the aftermaket available.

[twr7cx]

Have you tried these guys Advance Diaphragm Options - Home | Facebook (https://www.facebook.com/AdvanceDiaphragmOptions/)

They rebuild the genuine Lucas which is better made than the aftermaket available.

Thanks, will check them out. Hopefully I retained the original unit that I pulled off somewhere in the garage.