direct injection diesel engine help

[mowgli]

yesterday we refitted the injection pump to a 4 cylinder non turbo isuzu engine fitted in a jcb 8t excavator...

we had taken it out in the first place because it was running rough & we found it was not pumping diesel into no.3 cylinder & sent it for a rebuild

when it was restarted, it ran really rough, and was only running on 3 cylinders, no.3 being the culprit again.

after an hours fiddling, i deduced that no.3 injector was ok, but whatever fuel that was going into no.3 was not getting burnt & was causing the thickest blue smoke out the exhaust, which stopped if i undid the injector pipe..

so we start thinking cracked valve or similar, so off came the head to find that it the head & gasket were fine....

so here is my final deduction & I want all help & advice on this

the injector pump must be pumping fuel to no.3 cyl too late to combust, but it is firing enough fuel.

on 8am tomorrow morning, i plan to be knocking on the door of the diesel shop demanding a free second rebuild & I don't want to look stupid (well, any more than normal anyway).

thanks

Mike

[Jon_nova1]

I really don't get why you did mosty of the above lol

have you checked the glow plug is right? and connection to the glow plug it sounds stupid, but i don't see it in the above

also if it had a rebuild, why would the head and gasket be at fault? if it had the problem before and after the rebuild, have you ever considered it may not have been a part that wasn't rebuilt?

[mowgli]

jon, the engine showed no signs of mechanical failure, the fluids were all in the right place & there were no external signs of any leakage

the digger had been run for a couple of weeks with the misfire, and we found that no.3 cylinder had not been receiving fuel for a long time. now a diesel engine relies on the fuel as a bore & valve train lubricant & coolant, so if it had not been getting any fuel, then the valvetrain was getting undue stress, and also when you have just spent £450 on a pump rebuild, you expect it to be right. and diesel engine exhaust valves have been known to fail causing loss of compression, and thus power, so a head off was a simple check of that.

the glow plugs are the least of my worries. they are all fine

all of what we did was a simple process of eliminating potential causes. if a cylinder is not firing, then you check the pump, injector & the cylinder, its logical really

[deanwilko]

hi did you swap the injectors around? take it you cracked all the injector pipes open one by one and they was all the same to determine number 3 injector was ok

[Jon_nova1]

we had taken it out in the first place because it was running rough & we found it was not pumping diesel into no.3 cylinder & sent it for a rebuild



Apologies, the above gave the impression you sent the engine for a rebuild and not the fuel pump

[mowgli]

hi did you swap the injectors around? take it you cracked all the injector pipes open one by one and they was all the same to determine number 3 injector was ok

yup, we checked the pipes, cracked off the nuts one by one & swapped the no.3 injector with another one and it still ran crap.

for my sins, i've been playing with big diesels for about 20 years & this one is foxing me, i've never had a recon pump that didn't run right which is why I'm confused.com

[deanwilko]

is it all back together?

[Adam]

Hmmm, if youve still got the same problem now that you had Pre-pump rebuild then surely its not the pump at fault no......?

[mowgli]

Hmmm, if youve still got the same problem now that you had Pre-pump rebuild then surely its not the pump at fault no......?

adam, if only.. it has a different problem in the same place. pre recon, the pump was not delivering diesel at all into no.3, now it is delivering diesel, but the diesel is not causing a bang at all, which is why i think the pump's internal timing is the problem.

we even turned the pipes round & ran it up with both no.3 & no.4 injectors pointing out the side to see if they had spray patterns & both did..

[mowgli]

is it all back together?

we have already removed the pump to take it back to the engineers

[General Baxter]

mechanical or electric mike ?

how long did it take to start ? did it pop and bang when starting ?

[deanwilko]

i have spoken to a lad at work who nows a lot about this sort of thing he said if it stops smoking when you undone the iinjector pipe on number 3 it has to be a problem to do with compression. he said eassyiest way to find out is to squirt some brake/clutch cleaner up the intake (small amount as you probly no) and if it runs on 4 theres your answer. like you said it had a missfire for a couple of weeks and diesel also acts as a lubricant hope this helps if you need any more info or anything let us no and i will ring him

[mowgli]

mechanical or electric mike ?

how long did it take to start ? did it pop and bang when starting ?

old school mechanical pump.. it struck up immediately, no popping or banging, it simply ran on 3 cylinders & not all 4.

[mowgli]

i have spoken to a lad at work who nows a lot about this sort of thing he said if it stops smoking when you undone the iinjector pipe on number 3 it has to be a problem to do with compression. he said eassyiest way to find out is to squirt some brake/clutch cleaner up the intake (small amount as you probly no) and if it runs on 4 theres your answer. like you said it had a missfire for a couple of weeks and diesel also acts as a lubricant hope this helps if you need any more info or anything let us no and i will ring him

there are no signs of anything mechanical wrong with the engine, no.3 has compression, the valves are fine, the valve seats are clean, the piston is fine, the rings appear to be fine, as the bore is smooth as anything, with no wear visible. the unburnt diesel is getting pushed out the exhaust..

my view on no.3 is still that the diesel is getting there too late to be burnt, it is only down to a few degrees on timing at most..

[General Baxter]

got the be the pump, the timings out on the 3rd, simples

[mowgli]

got the be the pump, the timings out on the 3rd, simples

I truly hope so, nick, or i will be made to look like a right cock tomorrow

[General Baxter]

who did the pump ?

[mowgli]

welham in leicester... we've had good results there before

[mowgli]

right, we found out what it was finally.....

the conrod in no.3 cylinder is bent, causing the piston to be 5mm down at tdc. it now needs the engine out to get at the sump......

wet & dry comp test found it...

popular concensus is that it should have stuck the rod out the side or seized it solid, so a £67+vat conrod is cheap by comparison