ICP unplugged - Motor Dies Instantly
 

Hello,

I have a 95 PSD that developed a rough running/miss condition that gets way worse as the motor gets warmer. However, it still seems to run quite well under WOT. At an idle or any throttle position less than accelerating, it runs very erratically and has a very substantial random miss that seems to affect all eight cylinders.

This problem occurred immediately following me installing a new fuel pump, but I suspect it is coincidental. After having a buzz and a contribution test done, it was discovered that when the ICP sensor gets unplugged, the motor dies instantly. From everything I have read on this forum and others, this appears to be an indication of a problem with the high-pressure oil system, correct? It should not actually die when the ICP is unplugged, in other words.

I replaced the UVC harnesses and the IPR O-rings, however the IPR valve in my truck has an edge filter which makes it impossible to verify that the spring-loaded components within the valve body of the IPR valve are not jammed up, possibly with remnants of the old O-rings, which were obviously bad.

Does anyone know of any way to figure out where, or how the high-pressure oil is bleeding off? I gather that injector O-rings can be a problem as well, and I bought a set of them. However, without specifically knowing that they are the problem, I am very leery of replacing them.

If the injector O-rings are bad, would it be visually obvious?

If anyone can shed some light on this one for me, I would be grateful!

WA Dog
Dave

That's my understanding, but don't take my word on it. I would go ahead and do the injector o rings just to be safe. Of course if it were me, I'd just do injectors and a new HPOP and be done with it.

Yup! That's what I pretty much figured was the next step. Wish there was a way to know for sure, though.
Wonder if it is possible in some fashion to isolate the high pressure rail in each head and apply pressure externally to diagnose. Replicating that amount of pressure could be a trick, but maybe the full amount wouldn't be needed.
Anyway, thanks for the response.
WA Dog
Dave

There are several tools that allow you to do just this. I dont have the part numbers handy but I'll dig them up. The truck should run with the ICP connector disconnected, the PCM will default to a set map.

I would hook it up to a scanner and check the ICP pressures, cranking, running and at WOT and compare them to the Duty cycle at the same.

Thanks! It looks like I'll be doing just that.
When I mentioned my truck dies instantly when the IPC sensor is unplugged, I never thought about trying to restart it while it was still unplugged. I figured that if it died, that was that. Apparently, though, I should have tried restarting it while still unplugged.
I am thinking I will put new o-rings on the injectors, reinstall them and go back to testing the IPR a little more completely. I may have gone right passed a chance to spot something by not trying to restart it after unplugging the IPR sensor.
I'll keep posting if I happen on to something.
Thanks for the pointers and tips!

WA Dog
Dave

Well, I finally got my truck running quite well, thanks in no small part to all of the help and info from everyone on this, and other forums!
A formal 'Thank You Very Much' is in order!
I thought I would post this as a follow-up to how things turned out as it may be useful for some others.
Anyway, I replaced the IPR o-rings first, to no avail even though they were obviously bad. Then, I replaced the o-rings on my injectors, even though they looked good. Quite obviously, how things look to an eyeball as compared to how they look to 2 or 3,00 psi may be different! A surprising number of glowplugs were actually fairly loose and I am sure that didn't help it any, either.
With new 0-rings on the injectors after checking armature clearances (I guess that is what it is called), all of which were right at .003" and new UVCH, it started up and has run well ever since!

Once again,
Thanks to everyone who helped me with this!
WA Dog
Dave