fuel consumption revisited

**Ronski** · 7th February 2020, 03:23 PM

Hi all, new here and first time owner of V8 discovery 1, 1999. Vehicle was cheap and in really good condition, drives like a dream, love it.
Having owned a rover 3.5 sedan years ago, I double checked before buying the usual, signs of overheating etc.etc. Previous owner seemed to have taken good care but no service records. after a month, running great, no problems, I seemed to be putting fuel in constantly so decided to test. Filled 20 liter jerry and put in back, when fuel light came on I stopped and filled from can, reset trip meter, drove until light came on again. ****** 53 kilometers..Ouch!

So, following all the great advice here, a week of reading and searching, I started testing.
1. got under vehicle expecting to find massive fuel leak, none?.
2. plugs looked a bit old, replaced, checked compression on each cylinder as I went, all above 130, not bad.
3. Leads were already 8mm high performance, all checked ok. correct position, checked also in the dark for flashes...none.
4. checked fuel pressure regulator for leaks, fuel in hose, all good.
5. *vacuum advance...NOT working. in fact, timing checked with strobe close to '0' until revs to over 2000 then stable at 10deg.btdc Not good. same at 2500 not enough advance I'm sure.
6. temp sender reading 330 when hot...seems ok.
7. Ignition module has been changed to Bosch one, next to coil near radiator.

before going any further, one thing at a time I'm thinking, I have ordered new vacuum advance (oem) and will strip dissy to clean/service. Yes, read up on this and prepared.

My question: Is it possible the advance alone is causing this outrageous fuel consumption?, I owned 351 Ford V8's in my youth and they were never this bad.

After fitting new vacuum, I will test again before continuing.
Have made a list, including MAF, idle control valve cleaning etc. I have read that 15-20 per 100k's is normal, just seems like a huge difference if it's only the advance, Have a 3.5 V6 Pajero that gets around 13 per 100. and seems to have more power than the disco.

What else other than above could cause this, I feel like I'm driving down the road throwing money out the window.

Thanks in advance for any pointers to check next,
Cheers from Perth,
Ron.

**Red90** · 7th February 2020, 10:27 PM

That is not vacuum advance. That is centrifugal advance not working.

**Ronski** · 8th February 2020, 10:10 AM

Originally Posted by Red90

That is not vacuum advance. That is centrifugal advance not working.

You are right, but tested vacuum with hand pump, does nothing, suck on hose, just free flowing. no change to strobe timing.
Centrifugal is moving, but not moving much,(vacuum disconnected), 0-10deg is not right at full advance.
Parts from local dealer arrive on Monday, so it's out with the dissy and rebuild.
will update when done,

As a comparison, when the low fuel warning light comes on in the Pajero, I can drive 48 klm on the reserve, about 7-8 litres. Disco, 53 only with 20 liters ????
cheers,

**Red90** · 8th February 2020, 12:06 PM

Vacuum advance is just to make for a nicer idle. It has nothing to do with performance or fuel consumption.

Anyway. To get 2 km/l means something is seriously wrong with the fuel injection. It is not the fault of the broken distributor.

**Ronski** · 8th February 2020, 02:14 PM

Thank you, that answered my question, I wasn't sure how the distributor could cause it. After doing it anyway and setting it right, I will get the injectors looked at. will keep you posted.
cheers from down under;
Ron.

**Old Farang** · 8th February 2020, 07:01 PM

Originally Posted by Ronski

Thank you, that answered my question, I wasn't sure how the distributor could cause it. After doing it anyway and setting it right, I will get the injectors looked at. will keep you posted.
cheers from down under;
Ron.

temp sender reading 330 when hot...seems ok.

Are you sure you checked the correct sensor. There are two, one for the temperature gauge and the other for the engine ECU. If the ECU sensor is faulty it will cause the injection system to run rich all the time.

**Ronski** · 9th February 2020, 11:13 AM

Yes, there are 2, one for sender has 2 wires, gauge only single wire. studied lots of posts on this, when cold and hot, ohms on 2 wire one reduce to 330 when hot, getting dissy parts tomorrow, will rebuild that and set timing correctly before moving on. Plugs were black, but not oily or sooty when replaced, so definitely running rich.
Thanks for reply,

**Ronski** · 13th February 2020, 09:44 AM

Some new info, previous owner came over, he had lost some keys and thought they may be in the disco.
He then told me the vehicle had been sitting and not driven for about a year. Put in new battery and driven for a week before selling to me.
Before that it was getting reasonable economy. But, who knows??

This to me points to fuel system, or injectors need cleaning. is it worth using a bottle of so-called injector cleaner in fuel tank? do they actually work at all, or is it best to remove completely and have tested.

**Finnius** · 13th February 2020, 04:55 PM

Originally Posted by Ronski

Some new info, previous owner came over, he had lost some keys and thought they may be in the disco.
He then told me the vehicle had been sitting and not driven for about a year. Put in new battery and driven for a week before selling to me.
Before that it was getting reasonable economy. But, who knows??

This to me points to fuel system, or injectors need cleaning. is it worth using a bottle of so-called injector cleaner in fuel tank? do they actually work at all, or is it best to remove completely and have tested.

In case you were going to replace the injectors, i bought a set of replacements from the US for my 3.9V8. They were for a Mustang V8 and had the same specs as the ones in the disco but they were a much newer Bosch design. I think they had more and smaller outlet holes than the factory land rover ones which should mean better atomization, burn, power, economy etc...

My fuel economy was never as bad as yours, so i cant comment on that, but the power gain from the new injectors was massive.

**Bundy** · 13th February 2020, 06:10 PM

Originally Posted by Red90

Vacuum advance is just to make for a nicer idle. It has nothing to do with performance or fuel consumption.

Anyway. To get 2 km/l means something is seriously wrong with the fuel injection. It is not the fault of the broken distributor.

No Vac advance usually has no effect at idle it gives better economy at cruise speed under light load as the timing advances more.

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