need advice before rebuild my IPR, truck running rough!

[eyyu]

1. 95 PSD, manual tran, 140k miles, no check engine light
2. 2nd new CPS sensors tested, >5v to one of the 3 wires, 12v to the other, good rpm reading while cranking.
3. All glow plugs tested well at the valve cover plugs (<1 ohm), 12v to the plugs, WTS light does go on


I already got the IPR rebuild kit ($57 from the dealership for 2 O-rings and a couple pieces of small metal). I'll go ahead get this done anyway just as a PM activity if it does not solve my problems. I'll give all the background I know of concerning the symptoms my truck has and would really appreciate any advices you may have to offer. Thanks in advance.

It all started a few months ago when the engine started to cut out while driving (any speed) randomly. Since it’s a clutch truck, the engine does not actually die most of the times. It just keeps cutting out and come back. Sometimes every few seconds. Whenever it dies, it always starts right up with a turn of the key. That’s why I got the old (not so much, only 3 years old) CPS out and replaced with a new one and it did not help (tried 2 new ones).

I just kept driving the truck for the last 3 months as it keeps doing this and fortunately, it never stranded me. A few days ago, I read about the IPR and decided the poke around it. After I did that (not knowing if it’s coincident or not), the truck started to run perfectly throughout the day and will start up right away. I thought that I found the root cause of the problem being the IPR connector until the next day when the symptom changed somehow. Now, it will not easily start (“cold” at 60 degree). Once it started, it will run almost perfectly most of the times and it’s easier to restart. I say “most of the times”, because once a while it will have the old symptom again (keeps cutting out). While it’s running, if I poke the wires and connector (IPR, ICP, valve cover connectors) I see of hear no difference.

While the truck is running, if I unplug even both of the valve cover plugs, it will run horribly, but it will stay running. So, I don’t think that the valve cover plugs are bad, unless all 3 or 4 of them are having bad connection the same time which is unlikely. Very likely, it’s something which controls fuel supply to all the injectors (no diesel smell or smoke when it’s not starting).

Again, please help me to find out what it is going wrong with my truck so I can use it without fearing being stranded. I have a load of debris which I need to haul it to the dump. My senses tell me not to get it out of my driveway this time before I figure out what it is going on in there. Thanks all for taking time to read this and offer help. Erwin

[JSchuricht]

Do you have access to a scanner. Would take a lot of the guess work out of the equation if you could pull codes and check values. Just a guess, but try pulling the plug off the ICP sensor and see if it runs any smoother. Also check for any oil getting into the connection, as it may be going bad.

[Patrick Feeley]

Also do a real good inspection of the IPR wiring and the fuel bowl wiring harness (IPR wiring is part of that harness). Diesel fuel does some nasty things to the wiring insulation and can cause all kinds of problems (inside the loom too). Cheers!

[eyyu]

JSchuricht, while it's runing well and I pull the ICP plug, it gets bad (as it supposed to be). I did not test this when it keeps cutting off. I'll do it when I get the opportunity.

Patrick, When I pull the IPR to do the rebuild, I'll check all the connectors carefully.

I do not have a scanner and I'm scared to drive her anyway once I get her started. I'll just buy a cheap one from Autozone. Thanks a lot.

It's kind of cold this week in st. louis, 40s in the Bush statium. I'll rebuild the IPR once it warms up outside. Hopefully someone can give me more insights. Erwin

[greasyF250]

A cheap autozone code reader won't read the codes on our trucks .you will need autoenginuity or another high quality scanner.