XM 2.1 TD.Fueling??

Post by **geoff_old** » 05 Oct 2002, 16:02

Hello all.Having frightened u all with the word XM will proceed with problem.Performance is variable, sometimes it will go very well with little throttle but will sometimes feel flat and require more throttle for less performance!Pump,injectors,fuel lines are new the only symtom being that when started it is rough running as if on 3 cylinders @ low revs. but this is not always, if it starts & runs on 4 then it will continue to do so.A blast up the motorway will sometimes inprove it for a couple of days.Help if u can please its driving me nuts.Its 1992 2.1 td.
G Gould

Dave Burns · Post by **Dave Burns** » 05 Oct 2002, 17:58

Possible injector fault, when it starts on 3 again, crack each pipe union in turn to identify the faulty one, if there is a lame injector the faulty one will make no difference to the lumpy running when its fuel is cut off as the union is loosened.
On finding such an injector, change its position with another, if missfire then goes to the other cylinder the culprit is nailed, if it stays on same cylinder this confirms a pump fault.
Applies if the system is purely mechanical.
Keep Hands clear of any high pressure spray and wrap wrag round injector.
If the missfire is random on all cylinders the fault is either in the pump or may even be a simple case of air getting in somewhere.
Dave

Post by **geoff_old** » 06 Oct 2002, 00:47

Hi thankyou for the reply.Will try the info. Sunday.A little more information, injection system Bosch, pump and injectors (and filter head )are NEW not recon.Head recon.inc. new precombustion chambers.The only thoughts I have are these,the above have made the problem a little better but thats all.Could it be a hydraulic tappet problem??If so how do you check them? Thankyou.
T T F N.
Geoff.
G Gould

Dave Burns · Post by **Dave Burns** » 06 Oct 2002, 15:20

Hmmm, wasn't aware the problem existed before all the fueling components were replaced, but don't assume they will be faultless because they are new, rare yes, unheard of no.
When did it all start, before or after head replacement.
Is the cold start timing advance lever being operated correctly on the pump, either waxtat or vacuum operation.
If the hydraulic tappet's were at fault, might you expect to hear a rather loud rattle, though over the noise a diesel makes probably not.
Don't know any way of identifying faults in such components without stripping it down and looking at at them.
Cracking the injector union's should still show up which cylinder is lame, if you can narrow it down to one cylinder it eliminates a heap of other likely causes, plus if you do go in you will know which cylinder to concentrate on.
Dave

wabbitwibble · Post by **wabbitwibble** » 09 Oct 2002, 16:37

Also check for air leaks in the fuel system,
The top of the fuel tank sender/pickup develops hairline cracks, this is under a big rubber plug beneath the rear seat.
Also the fuel preheater on the side of the block is a very weak point for air leaks, just bypass it with a long piece of hose from the fuel filter to the bulkhead metal pipes

Post by **geoff_old** » 12 Oct 2002, 05:33

Thankou for the info Dave.The series of events were as follows- Inj. pump replaced because the old one was leaking from the drive shaft seal and it had a degree of play.The same time the filter head was checked and found to have a air leak. (very small, but did'nt want to chance it.) A couple of months later the head gasket started to leak. Looked like the original judging by the material. Failed between 2 cylinders. Cam found to have some very 'funny' wear marks, (hardening breaking up.)Was replaced by known good one. Four tappets were found to be easilly compressible and were replaced also with known good ones. Head rebuilt.1000 mls and the 'Miss' started.Thinking about it it does seem likely to be a tappet jacking up.The reason I say this is because I had heard the sound that a bad tappet caused when listening to the inlet manifold with the turbo pipe removed.Like a cylinder was firing back into the manifold. The other day I heard almost the same sound from the exhaust.I don't know if that makes sence but that is what it sound like.The inlet was silent. As soon as time permits I will investigate further.Many thanks for your help. cheers.
Geoff.
PS. When going properly it goes very very well from 1000 rpm. onwards.
G Gould

Post by **geoff_old** » 01 Nov 2002, 00:00

Hello everyone.At longlast can report that the intermitant miss has been found and cured. It was a hydraulic tappet holding a exhaust valve open, when it felt like it!!!
Cheers all.
Geoff.
G Gould