P38, 4.0 petrol, 2002, Bosch - no start

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Jock85

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Evening all, my P38 broke down on me the other week and I'm having an awful bother getting it running again. Nothing catastrophic happened, it just stalled out on me on a dry day when I was driving near my house, probably less than 10mph. The engine turns freely on the key and it sometimes starts but it will only just idle but it won't rev up and if it does start it misfires very badly before dying. The vehicles done 170k miles with LR fitting a replacement new engine at 80k and it has full LR service history. Fluids and levels are good and so far, I've replaced the crank sensor (new & Bosch), confirmed by putting a spare spark plug on each HT lead that they all spark and I get fuel pressure of 45psi on ignition with over 50psi on cranking. My Bearmach shows no stored fault codes other than ABS ones and the EML isn't on. If anyone has any clues or diagnostic tips they'd be greatly appreciated. It ran very well before this episode.Thanks

P.S. MAF was also replaced about 4 months ago and unplugging it doesn't affect it.
 
No symptoms or noises at all. I remember I was just rolling to stop when the ignition lights came on, almost like the key had been turned off. I suspected something had come loose but I can't find anything and it's still sparking and fuelling.
 
any cough/pop/bang/misfire when you turn the key, or nothing at all? you say fuel and sparks OK, have you had the plugs out? what do they look like? While they're out, be good to give them a good clean. A compression check wouldn't be a bad thing while you're at it.
 
kermit_rr said:
any cough/pop/bang/misfire when you turn the key, or nothing at all? you say fuel and sparks OK, have you had the plugs out? what do they look like? While they're out, be good to give them a good clean. A compression check wouldn't be a bad thing while you're at it.
Click to expand...
No noises when you turn the key, the only time it misfires is if it actually runs but it then misfires quite badly - it's almost as if the timing is out but there is no reason for that I can see - well maintained vehicle that ran really well up . I whipped the plugs out too and although they aren't damaged in any way, the first four closest to the front were black/showing signs of running rich and the back four closest to the cabin were a healthier colour but i had spent the previous hour or two running around fields at low revs. I think I will do a compression test and physically check the timing is still correct.

Out of curiosity, if both of these checks come back okay, can anything cause the ignition timing to skew? Is the ECU a possibility?
 
Jock85 said:
No noises when you turn the key, the only time it misfires is if it actually runs but it then misfires quite badly - it's almost as if the timing is out but there is no reason for that I can see - well maintained vehicle that ran really well up . I whipped the plugs out too and although they aren't damaged in any way, the first four closest to the front were black/showing signs of running rich and the back four closest to the cabin were a healthier colour but i had spent the previous hour or two running around fields at low revs. I think I will do a compression test and physically check the timing is still correct.

Out of curiosity, if both of these checks come back okay, can anything cause the ignition timing to skew? Is the ECU a possibility?
Click to expand...
I don't know if you have checked, but the MAF might be a possibility.
 
I was thinking.. Unlikely to be coil.. I can't see they would both fail at the same time.
When I first posted, I's just been reading the series forum and was thinking about a single, oil-filled coil :confused:
 
The replacement crank sensor fitted a couple days ago was a Bosch one too, same part number as the one that was removed. I'm not that familiar with the engine so I'm not up to speed with all its workings. From what I've read, the cam sensor normally throws a code but even if it was iffy apparently it wouldn't cause the car to just come to a stop?


kermit_rr said:
I was thinking.. Unlikely to be coil.. I can't see they would both fail at the same time.
When I first posted, I's just been reading the series forum and was thinking about a single, oil-filled coil :confused:
Click to expand...

If the coil was suspect, would it stop sparking? So far, all HT leads seem to be creating a nice spark. It the fuel pressure, about 50psi on crank, within acceptable range?
 
Had that on my 4.0L...bought as a project started ran fine ...couple of months later hard to start then no start...good fuel pressure changed temp sensor and cleaned plugs fired up straight away...sold it on with the old sensor put back in wouldnt start again till new one put back...
 
Shippers said:
Had that on my 4.0L...bought as a project started ran fine ...couple of months later hard to start then no start...good fuel pressure changed temp sensor and cleaned plugs fired up straight away...sold it on with the old sensor put back in wouldnt start again till new one put back...
Click to expand...

A temp sensor? That's a weird one. To be honest, I may just give that a go! Why did you suspect that in the first place?
 
Jock85 said:
A temp sensor? That's a weird one. To be honest, I may just give that a go! Why did you suspect that in the first place?
Click to expand...

I have a small share in a garage down here with a mate who is an autotech...it was his diag...main dealer wanted 60€ for the sensor not in stock got one from island 4x4 sent here think it was about £8...it was the RH looking at front of engine...LH goes to guage...
 
I had this once on a VX cavalier. I had done the head gasket and forgot to reconnect the temp sensor. On that engine the open circuit reading is effectively - 273 degrees so the ecu dumps gallons of fuel in as it is way off the scale on the fuelling map.
I found it would start and rev its nuts off if you held throttle wide open when cranking but would bog down almost instantly and die.
That all said, I would exoect that these days, the ecu would use a substitute value.
Just a thought, what about injector wiring, could it be grounding out and pulling the ecu injector voltage down?
 
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