2002 Disco not starting, have fuel and spark

[Giz11]

I have an issue with my 2002 Discovery V8. The other day it started to missfire at idle but went away when the engine was reved. The misfire got progressively worse over the next few days and with some back firing on starting. After stopping at the shops it refused to start. It turns over ok . I towed it home and started to try to work out the issue. In repeatedly turning it over it seriously backfired to the point that it completely peeled open the muffler.
With the muffler now off, I changed the crankshaft position sensor, still wont start. I checked the fuel pump and that is working. There is only one code coming up on the Nanocom t "P1668 = Anti-theft Alarm Serial Link Fault Drive Cycle A, Occurred 8 times,Signal too low, Fault is not currently present, Fault determined as intermittent, Fault does not cause the MIL lamp activation" I can clear the code and the car still does not start. The code does not appear until I lock and unlock the car. I tested the spark on each cylinder via a timing light. No spark on 1,4,6. One spark at the end of the starting cycle when the key was turned back to position 2 on 3,5. Sparked 4 times then nothing on 2. Spark appeared ok on 7 and 8. I have checked the resistance on pins 32 and 46 at the ECU (connecting to the CPS) and that is fine it is same resistance at the sensor so the cabling should be good.
I have ordered new coil packs so will try them next but I am at a loss as to what may be the problem. Hope someone can help
Giz

[Pedro_The_Swift]

Good call with the coil packs,, they usually let you know they are about to fail,,
If you worked in the same position as they do,, You'd be happy with 20 years service,,

[Giz11]

Thanks Pedro,
The only thing is that having 2 coil packs fail at the same time would be rare. Anyway if its not the coil packs then I assume its the ECU.
Giz

[101RRS]

A blown out muffler is normally caused by an intermittent or no ignition source. Cylinder is still getting fuel injected but due to no ignition it is passed into the exhaust and when the amount and mixture is right - bang. - ask me how I know [bigsad]

142506

I think you are on the right track - these engine do have a bit of history with coil packs. So as you are doing - replace, if not check wiring and ECU ignition signal - then the only other thing would be cam sensor and crank sensor. There is not much else.

Garry

[ballbag]

If tacho is working and showing sensible cranking revs (1000rpm?) then crank sensor can be assumed to be ok.

Alarm fault might be a red herring. Think immobiliser works by not supplying power to fuel pump. There is a schrader valve (I think) on fuel rail behind/below coil packs. Open valve while assistant cranks engine to check fuel pump operation.

Think cam senor controls injection sequence but ECM will revert to default if sensor fails so engine should still run.

Seems spark issue mostly relates to LHS (passenger) coil. Think coils are the likely culprit.

I soldered extentions into the coil signal wires and relocated packs to the firewall on my vehicle. Will never be traumatised by failed coils again.

[Roverlord off road spares]

I soldered extentions into the coil signal wires and relocated packs to the firewall on my vehicle. Will never be traumatised by failed coils again.
Good idea, thought about that when i owned a v8 D2.
Do you have pics, and did you need to get non standard leads to use this?

[ballbag]

Correction: immobiliser disables starter motor relay, not fuel pump. So alarm fault certainly unrelated.

[ballbag]

No pics at hand sorry but from memory I cut and welded existing coil bracket and bolted it to an existing, unused threaded hole infront of the passenger.

Yes, I had leads made up by local auto parts joint. They were ready overnight and cost about the same as a standard set off the shelf.

[Giz11]

Hi Ballbag,
The tacho does not move when cranking and that is with a new cps installed.
Could it be an earth fault at the ecu side ?
Regards
Giz

[ballbag]

Hmmm...

There are spacers for the crank sensor so the pickup is the correct distance from the flywheel. Did they go back in?

[Giz11]

There were spacers but they went after the sensor. So I put it in as sensor, spacers, nuts. If the spacers went in first then the sensor would be sitting up off the body of the engine 10mm or so. Are there other spacers

[ballbag]

I just checked my spare engine in the shed and you’re right with the spacers.

So it’s gotta be coils I suppose.

If I get a chance over the weekend I’ll disconnect my coils from the harness and check the tacho on cranking.

[Giz11]

Thanks Ballbag,
Hopefully the coil packs I purchased will arrive today and I will put them in tomorrow.Ill also work out how best to relocate the coil packs but the actual relocation will be for another time. I have a prospecting trip planned departing Saturday week hence some urgency to get the Disco working. I assume if its not coil packs then its ECU as that's about all that's left.

[Giz11]

Ok I have now changed the coil packs and HT leads but still wont start. It has regular spark, I tool spark plug 2 out and used it to test the rest of the bank. It looks a bit weak as I can only see the spark at night time. Im at a bit of a loss now.

[ballbag]

Have not yet had chance to test tacho without coils connected, sorry.

With new oils I can’t think of any reason why spark would be weak. But there is spark nonetheless.

Did you check for fuel at vavlve on fuel rail behind coils?

Easy things to rule out:
1. Disconnect MAF, try to start.
2. Disconnect cam sensor, try to start.
3. Disconnect idle air control valve, try to start.

[Giz11]

Unplugged the MAF still did not start
Unplugged the Cam Sensor , still did not start.
Could not find the schraeder valve. It it under the green cap at the rear of the motor on the left side ?
However the engine smells of petrol and I did check the fuel pump at it works at the tank.
Tomorrow as the front of the engine is exposed I will change out the cam sensor and water pump (I found that it was leaking)
I think I have found a second hand ECU so I can try that as well.
This car is becoming a frustration

[101RRS]

Will that ECU work as it will be looking for the Body Control Unit of the car it came out off and may not recognise your BCU?

[ballbag]

Yes, green cap on fuel rail valve.

Not sure what needs to be done for ECU to work. Suggest messaging forum member sierraferry if you have difficulty.

Other than ECU and ensuring all earths are making good contact, I’m not sure what else to do here.

[Pedro_The_Swift]

Not many things actually stop these things,, (lots of things though contribute to a decline in performance, coil packs normally fall into this catergory).
Crank angle sensor will stop them.
Fuel pump will stop them.
Security will stop them.

[Giz11]

The saga continues.
I checked the fuel pump and it is working. I then had some one turn the motor over whilst I held in the schraeder valve and no fuel come out. I thought it was meant to . So does that mean a blockage in the fuel pipe ?

[Pedro_The_Swift]

afaik its just there to attach a pressure valve to,, turn the key to POS2 and the pump should pressurize (audable) the system,,

[bee utey]

The saga continues.
I checked the fuel pump and it is working. I then had some one turn the motor over whilst I held in the schraeder valve and no fuel come out. I thought it was meant to . So does that mean a blockage in the fuel pipe ?

If there's no pressure the pump assembly may have burst a high pressure hose connection after the pump. It shouldn't take too long to lift the load space carpet and extract the pump assembly to look at it.

[Giz11]

Took the pump out, seemed ok visually. When I took of the fuel pipe it was pressurised but not much fuel came out, about an egg cup full. Th pump motor works and with the pump back in and the fuel pipe still disconnected petrol does come out of the pump outlet.

[bee utey]

Took the pump out, seemed ok visually. When I took of the fuel pipe it was pressurised but not much fuel came out, about an egg cup full. Th pump motor works and with the pump back in and the fuel pipe still disconnected petrol does come out of the pump outlet.

Rig a pressure gauge at the pump then give it a whirl. Or just plug the outlet and listen for the pump loading up.

[ballbag]

It should **** out of that schrader valve.....

[Giz11]

New cam sensor in today and still no joy. So it has to be fuel. There is a smell of fuel which I assumed was just the unburnt fuel coming out of the exhaust but maybe there is a leak somewhere. I plug the fuel pump and listen to it load up.
Ill also see if I can get a pressure guage for the schraeder valve.
At least I changed the water pump today and all the hoses so that was positive.

[ballbag]

Have known fuel pumps and fuel pump relays that worked well enough to prime or switch on but failed under sustained load.

[Giz11]

Found the Schrader valve after taking off the intake manifold.Getting fuel at that point. Tested the pressure and the pump holds pressure. So I have regular spark, although doesnt look that strong, fuel, air. Tomorrow I will check timing. Put in a replacement ECM and did not even get spark, went back to the old ECM. Probably need to code it and all I have is a Nanocom so I need to work out how to do this. Any ideas given that the crank and cam sensors have been replaced and so have the coil packs and the HT leads.

[ballbag]

Ah you poor bugger, must be exasperated.

Timing is all that’s left but nothing that you’ve said gives any reason for it to be out. Almost impossible. [emoji848]

[V8Ian]

I had a similar problem with my 3.9, it turned out to be a blocked muffler.

[Roverlord off road spares]

Ah you poor bugger, must be exasperated.

Timing is all that’s left but nothing that you’ve said gives any reason for it to be out. Almost impossible. [emoji848]
The timing is controlled by the ECU so no manual adjustment,
You say you replaced the Cam sensor, and it's wire continues up into the injector loom via the left front of the engine, it might be damaged as it is a tight squeeze. did you check its wiring as well?
It'll stop starting. see pic
regards, Mario,
142916

[Roverlord off road spares]

Will that ECU work as it will be looking for the Body Control Unit of the car it came out off and may not recognise your BCU?

Easy to get it to be recognised with a Hawkeye or Nanocom, via learn security function and it will be ok.

[Roverlord off road spares]

Not many things actually stop these things,, (lots of things though contribute to a decline in performance, coil packs normally fall into this catergory).
Crank angle sensor will stop them.
Fuel pump will stop them.
Security will stop them.
A tripped inertia switch will stop them.

[Giz11]

Because I am getting spark and fuel I dont think its the inertia switch. In my mind there are only 3 things left. ECM, wiring and timing chain.
So I am going to map the old ECM and copy it to the new ECM via Nanocom. When I plugged in the new ECM without mapping I didnt even get a spark.
Timing chain will be last.
It is probably something really simple like a earth wire has broken. Very frustrating!

[101RRS]

Given what you said in your very first post it is not timing chain.

Will the engine fire up on starting fluid? If yes not a timing issue and most likely an injection/fuel issue - if still no firing then you are back to square one.

[Giz11]

I will try with Aerostart and see. At the moment the intake manifold is off so I could put it back on with the old gasket just to check. I came down with the Lurgi last week so was unable work on it but will do this week. Thanks to everyone for their help. I will also check all the wiring to make sure there is nothing wrong there.

[Giz11]

Just an update of the prolonged saga with my Disco 2 V8. I had the injectors all cleaned, checked to see if they were getting voltage and they were. Put the intake manifold back on, connected everything up again. The coil pack relocation kit came so I also installed that. Then with the help of my neighbour started to test each HT cable for spark and it started. I had a cam sensor fault but that was due to the plug not seated properly. After that all faults had cleared. I drove the car for a week and starting was becoming more difficult. Then it wouldn't start at all and kaboom the muffler blew up again. So I towed the car back home and went to google again. I found a post from someone who had the exact exploding muffler symptoms that I had and he also went down the same road of replacing crank sensor, cam sensor etc. He found out the internal fuse box was the culprit or specifically the circuit board within the fuse box. I purchased another one from ebay but before it arrived I replaced all the spark plugs and again it started. I started to check all the wiring I would have touched when putting in the spark plugs. but it was still starting although not running well. I then replaced the fuse box and thought I had better clean the IACV, MAF sensor and Throttle Body, as well as adjust the throttle and cruise control cable. The IACV was full of gunk and did not rattle until half a can or throttle body cleaner was sprayed into it. After all of that it idled fine. I gathered enough courage to drive it and it drove like a dream, starts fine and no faults.
So with the risk of being premature the prognosis is the IACV was getting stuck and possibly the 'Intelligent Driver Module' (IDM) in the internal fuse box was faulty. It may be the cable from the IACV as well but I rattled that that to see if the fault returned and its hasn't. What a 8 month saga and hopefully the problem has been solved although there is a small element of doubt.
Thanks to all those who provided advise, it helped considerably.

[ballbag]

Glad you appear to have it sorted and thanks for posting the conclusion

PS - just quietly, I suggested you check the IACV back in July🤪

[Giz11]

Yep thanks ballbag, If I had looked at that first I may not have had all those months of an unusable vehicle and the expense of another muffler. I think with a disco 2 its just one long continuous learning curve.

[101RRS]

OK - the ICAV just helps the engine idle by allowing air into the intake manifold when the throttle butterfly is closed - given the problems you had of no spark and fuel and not running well I cannot see the ICAV being the issue. For sure I understand it could not idle but once the throttle was opened it should have ran. The ICAV can be bypassed and the engine will run at a high idle by tightening up the throttle linkage so the butterfly is cracked open letting some air in.

I am glad it is running now but I doubt the ICAV was the cause by itself and your other tinkerings have fixed the real cause.

I hope it continues to run well.

Garry

[ballbag]

Possible explanation....

Sticky IACV would have mucked up air:fuel ratio. Under throttle in closed loop fuelling ECM was chasing its tail - got it well wrong and boom goes the muffler....