Engine troubles (1 Viewer)

topman

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Jan 24, 2010
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Hi all, I have been having problems with a misfire on my 1988 2.5 diesel Ducato following a head replacement, as soon as the glow plug timer cuts off it has a permanent misfire on cylinder 2, I removed the head again today but i can find no signs of valve problems or cracks. Has anyone had a similar problem or any advice:Sad:
 

pappajohn

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Aug 26, 2007
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welcome to the fun topman.....

sounds like a dirty/faulty injector to me.
may be worth having them all overhauled.

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Jaws

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Could well be the pump its self.
By the sound of it you know your way round an engine but do you know how to ( quick and dirty method ! ) check the spray pattern from an injector ? I know you have swapped em and eliminated the injector its self but if the pump is misbehaving it will still show up..

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Jul 29, 2007
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Hi you need to do a compression test, all cylinders should read similar, you can hire one from the hire shops.

Olley
 

pappajohn

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what was the reason for the head change ?

did you have the replacement head skimmed and high pressure crack/leak tested ?
how have you accertained its No 2 cylinder ?
 
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topman

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Jan 24, 2010
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The head was changed following an exhaust stud snapping, I managed to purchase a head that had been completely reconditioned with new valves/shims skimmed and tested for cracks but following the transplant I have had nothing but problems. I have changed the injectors, changed the fuel filter, bled the fuel system checking each pipe for supply to individual cylinders. I have exhaust gases blowing back through the inlet manifold and a distinct misfire. When I dismantled last time to investigate I found soot around the inlet manifold to no2 cylinder.

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John H

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Sep 2, 2009
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The head was changed following an exhaust stud snapping, I managed to purchase a head that had been completely reconditioned with new valves/shims skimmed and tested for cracks but following the transplant I have had nothing but problems. I have changed the injectors, changed the fuel filter, bled the fuel system checking each pipe for supply to individual cylinders. I have exhaust gases blowing back through the inlet manifold and a distinct misfire. When I dismantled last time to investigate I found soot around the inlet manifold to no2 cylinder.


It sounds like a sticky or bent inlet valve to me.the valve must be staying open when the engine fires to make the inlet manifold sooty, have you tested the valve opening/closing with the head on? it could be a cam timing problem.
 

Jaws

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Now then !!!

This is a real shot in the dark and I aint seen it since.. well for a LOOOONG time

When you fitted the inlet and exhaust manifolds are you 100% certain the gaskets were lined up spot on ? In other words, if the old head had locator spacers and the new one didn't, it is possible the gasket to drop a little.

We struggled for a week or more with a Princess ( an old Hearse actually ! ) and in the end called in an Austin man

Told the story and he jumped on it straight away

What i STILL do not understand is that if it was out of line ( and we are talking about only an 1/8" or so ) on cylinder number 3, it MUST have been out of line for the rest as well, yet it was only the third pot that constantly failed to fire !


But !!! Yes,, more likely to be a bent or sticky inlet valve ..

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topman

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Jan 24, 2010
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Would a bent or sticky valve run ok when starting from cold, the misfire starts as soon as the glowplugs stop. I have removed the head once already to investigate this but ruled it out, I tried altering the cam timing slightly and the pump timing slightly but both made no difference.
 

pappajohn

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ifn you end up taking the head off again try this.....

ensure the valve heads and seats are dry and No 2 valves are fully closed, support the head, right way up, off the bench and squirt WD40 into the inlet and exhaust ports.....put plenty in so covering the valve heads fully.
leave for an hour or two then check around the valve heads for damp/wetness.
if there is you have a bent valve but to such a small degree you wouldnt normally see it.
dont forget the cylinder pressure is enormous....upwards of 20 to 1 compression ratio so the smallest of gaps will allow loss of compression.
 
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topman

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I took the head off again this afternoon, I have tried it the other way around spraying wd40 around the valves with the head upside down and all seemed fine but I will give it a go to see what happens. I think there will soon be a shortage of head gaskets in Essex if I dont get it sorted.:Doh:

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pappajohn

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I took the head off again this afternoon, I have tried it the other way around spraying wd40 around the valves with the head upside down and all seemed fine but I will give it a go to see what happens. I think there will soon be a shortage of head gaskets in Essex if I dont get it sorted.:Doh:

just had a thought on head gaskets.

are you using the 'conversion' gasket.

if the heads been skimmed it will need a slightly thicker gasket, which corresponds to the amount of metal removed while skimming.

the valve heads run so close to the piston crown, using a standard gasket it could allow the valves to just touch the pistons and bend them.

you obviously know your engines so i dont really doubt you know this already but worth a mention anyway.
 

John H

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Would a bent or sticky valve run ok when starting from cold, the misfire starts as soon as the glowplugs stop. I have removed the head once already to investigate this but ruled it out, I tried altering the cam timing slightly and the pump timing slightly but both made no difference.

It may run ok when cold, then as the engine warms up the additional heat may be enough to alter the bent valve and cause your misfire. as mentioned before a compression tester is the easy test and you dont have to take the head off.

John
 
Feb 22, 2008
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Heat from the glowplugs aid combustion so no misfire, as soon as the heat is gone only compression is left to fire, sounds like inlet valve problem, bent or not seating clean. Compression test will find it.

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topman

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When the valves are closed to each cylinder you can rotate the cam followers freely underneath the shaft
 

John H

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When the valves are closed to each cylinder you can rotate the cam followers freely underneath the shaft

I would put my money on a bent inlet valve then, as mentioned earlier it may not be visible to the naked eye, a compresion test is the way to go. if the heads already off, swap the inlet valve over from the old head, lap it in , check the valve clearance and see if it runs ok, good luck

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Francuccio

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misfire

Hi all, I have been having problems with a misfire on my 1988 2.5 diesel Ducato following a head replacement, as soon as the glow plug timer cuts off it has a permanent misfire on cylinder 2, I removed the head again today but i can find no signs of valve problems or cracks. Has anyone had a similar problem or any advice:Sad:/QUOTE] Hi mate, did you check for air bubbles???? in the feed line?? some times that can make the engine run as though you have a misfire, i would check that before you do anything else.:Doh:
 

chesterfield hooligan

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When the valves are closed to each cylinder you can rotate the cam followers freely underneath the shaft
Hi Topman is there valve clearance ie the followers when the engine is hot check there clearance when hot as it would cause firing up the inlet manifold on number two I have always found when rebuilding engines to look for the simple things as always overlooked ie pump working before not very likly same with the fuel side of it is the head the same as the one removed check with head gasket also when the head gets worm a crack might appear you appear to be to far away for me to check it that is a shame (sorry about the grammer woops not on facts now:ROFLMAO:)
Brian and Marion
 
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pudseykeith

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Nov 5, 2007
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Hi . If you have the head off, slip the inlet and exhaust valves out . lay the stems on a smooth surface and roll them. If the valves are bent the head of the valve will woble [even very slightly]. Don't tuch the seats but examine to see if there is any sign of blow back . When you put them back, lap them in then check the seat integrity [engineers blue] Be careful not to mix up the valve clearance shims. When refitting the camshaft check that there is the proper valve clearance when the cam is on its back over each valve
A cracked head would not normally cause a misfire, but you would find evidence of this, oil in the rad top and a discharge of water via the rad over flow when the engine is running. You could also find water in the engine oil, sump or cam box. [If a crack is evident, use a BARS LEAK. It will also seal the head gasket joint if its integrity is in question.

If the head is on and running, remove the air cleaner and listen in the inlet manifold, you could hear the blow back [popping] if it were the inlet valve not seated.
Injectors. Swop the injector in the misfiring cyl for a one from a firing cyl. If the misfire changes to the swapped cyl, chances are that the injector is naff.
Put the timing ,pump and cam, back to manufactures setting :thumb:

Hope this helps.
PK

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imprint

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I've read every word on this thread, and it's still nowhere near as funny as the tank engine story on the next thread up. I like Thomas much better....
 
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topman

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Jan 24, 2010
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A huge THANKS to everyone for the help, the WD40 trick worked, a leaky valve it was.:thumb: all replaced , back together and working a dream. Now all we need is some sunshine :Cool:
 
Feb 22, 2008
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Good stuff, but sunshine ??????????

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