p38 4.0 popping.

wammers · Jul 26, 2009

Beast o Bodmin said:
thats a brave statement for a 4.0

You think so. Classic burned exhaust symptoms. Hope it's not for his sake, but Missing, raw fuel igniting in exhaust, popping in inlet. Sounds like it to me. Lets wait and see. I know these electroniclly controlled engines can throw up many symptoms that hide the actual fault, but if this was a normally asperated engine with points and a coil, that is the first thing you would suspect.

mattfletcher · Jul 26, 2009

Big Vee, already changed the air flow sensor. Exhaust valve? Don't know, it runs mint for the first ten minutes then starts playing up. Like it is a sensor down. My mate plugged into it using his Snap On scanner and it did come up with air flow sensor, coolant temp sensor and camshaft sensor. He wiped the codes and cam shaft sensor was the only one to reappear. Which was understandable because I had already tried to unplug the other two while it was running. Changed the cam shaft sensor but to no avail. It's got to be a mechanical fault more than an elelctrical. Still havent had chance to do a compression test, but it looks like if it is a valve or piston rings or cracked block the heads are coming off. Does any one know what pressures I should get from a compression test?
Beast of Bodmin pm heading your way.

wammers · Jul 26, 2009

mattfletcher said:
Big Vee, already changed the air flow sensor. Exhaust valve? Don't know, it runs mint for the first ten minutes then starts playing up. Like it is a sensor down. My mate plugged into it using his Snap On scanner and it did come up with air flow sensor, coolant temp sensor and camshaft sensor. He wiped the codes and cam shaft sensor was the only one to reappear. Which was understandable because I had already tried to unplug the other two while it was running. Changed the cam shaft sensor but to no avail. It's got to be a mechanical fault more than an elelctrical. Still havent had chance to do a compression test, but it looks like if it is a valve or piston rings or cracked block the heads are coming off. Does any one know what pressures I should get from a compression test?
Beast of Bodmin pm heading your way.

Anything around 120+ should be ok. But main thing is they must all be same within a small amount. Do test with ignition disabled, throttle fully open and crank for same amount of time for each cylinder.

mattfletcher · Jul 27, 2009

Thanks Wammers, hopefully have a look tonight.

mattfletcher · Jul 27, 2009

Right, I've compression tested the cylinders and all read 160psi or there abouts, apart from number 1 (I think) left hand side front, that read 140psi and stopped dead. So judging by that the valves and pistons seem ok. Just spotted one of the HT leads was damaged number 2.

Beast o Bodmin · Jul 28, 2009

When running on gas its a good point to have the leads clipped with no cross over nice and clean with good quality leads.Ive a second hand set for £20 if you want.The drop in compression in just one cylinder is alarming.
Personally i would get it running nice and consider that the piston may be on the way out.
The leads may just fix the problem as they can be a sensative issue...

wammers · Jul 28, 2009

mattfletcher said:
Right, I've compression tested the cylinders and all read 160psi or there abouts, apart from number 1 (I think) left hand side front, that read 140psi and stopped dead. So judging by that the valves and pistons seem ok. Just spotted one of the HT leads was damaged number 2.

Did you put some oil in No 1 cylinder the one that was down to see if you get a different reading. If not do so, if compression increases it's rings if not it's a valve.

mattfletcher · Jul 28, 2009

No Wammers didnt get chance to it was pitch black, hopefully I'll get round to doing it Thursday, and hopefully I'll be closer to fixing the blasted thing. It's only took 4 months to get to this stage.

wammers · Jul 29, 2009

mattfletcher said:
No Wammers didnt get chance to it was pitch black, hopefully I'll get round to doing it Thursday, and hopefully I'll be closer to fixing the blasted thing. It's only took 4 months to get to this stage.

Do it then, does sound like you may have an exhaust valve on the way out. 20 psi is a big difference. They should all be ideally within + or - 5 psi of each other.

mattfletcher · Jul 29, 2009

How much oil shall I pour into the spark plug?

p38 4.0 popping.

wammers

No longer with us, RIP

mattfletcher

New Member

wammers

No longer with us, RIP

mattfletcher

New Member

mattfletcher

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Beast o Bodmin

Banned

wammers

No longer with us, RIP

mattfletcher

New Member

wammers

No longer with us, RIP

mattfletcher

New Member

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