Diesel Mechanic

[MassCJ5]

Does anybody know of a good diesel mechanic around here?

[Chadnutz]

What is the problem?

[MassCJ5]

It's missing real bad. I just put a fuel filter on it a couple months ago so I don't think that's the problem. But since I don't know much about diesels I have no idea what the problem could be.

[Chadnutz]

Do you have access to a scanner so you could run a cylinder contribution test? Does it miss non stop or periodically? Try to be more specific and I will see what I can come up with from my Powerstroke buddies.

[MassCJ5]

No, I don't have access to a scanner. I took it to my diesel guy at home when I was up there last week and he put his on it and it showed to be a problem with the fuel pressure regulator and some sort of problem (I don't remember exactly what the computer said) in the #3 cylinder. He replaced the regulator and it has run fine up until a couple days ago. Most of the time when I crank it up for the first time, it runs just fine. It doesn't start missing until it gets warm, then it's pretty much a constant thing. It's at its worst when taking off and if it goes into overdrive under 50 mph (which would be expected since that's when it has the most load on the engine) and it seems to level out at about 1800 rpm. The only sort of mod I have is a 75hp chip, just in case you needed to know anything like that. That's pretty much the best way I can explain it.

[MassCJ5]

Just to let you know, I put another fuel filter on it today and I unhooked the batteries to reset the computer and neither one of those worked...

[Chadnutz]

Injection Pressure Regulator Valve Removal
To remove the IPR you can remove the fuel filter housing or at least loosen it to allow room for the wrench and to maneuver the valve in and out. The 98.5/99 IPR is accessed easily from behind the fuel filter. Remove the air intake Y pipe and plug openings. Remove the fuel return hoses from the pressure regulator block, remove the filter housing bolts and lean the housing back. Unplug the EOT sensor and IPR valve. Use a 3/4" wrench to remove the solenoid nut, spacer and solenoid coil. Using an 1 1/8" wrench (or a very deep socket--the filter housing will have to be removed for this) remove the IPR valve. Make sure that the replacement IPR is the same level part as the old one. Engines built up to serial number 187099 in early 95 use P/N F4TZ-9C968-C; engine number 187100 and up use F5TZ-9C968-A. Do not use sealer on the IPR threads, it could plug the orifice in the threaded area. Torque the IPR to 35 ft/lbs and the solenoid retaining nut to 53 in/lbs. You'll have to drive the truck to purge any air from the HP oil system and clear any codes set during the replacement.

Injection Pressure Regulator Removal and Replacement


by Coach Davis
I've been having a slight problem with my truck not wanting to idle very smooth especially when hot and the more miles the oil gets on it, the worse it would idle. With the engine cold it would idle pretty smooth, but hot, it had somewhat of a shake to it. When I purchased this truck, the oil had been in a little too long on this ONE and only ONE oil change and because the HEUI system is so sensitive to clean oil that I probably was going to have to change some of the components to remedy the idle/flutter problem.

I purchased a new IPR a few months ago and was trying to get enough miles on the oil before I changed it so I could ensure some of the characteristics that changed were not because of "NEW" oil. New oil will always make a Powerstroke run a little better than oil that has 3000 miles on it. I wanted to make sure I installed the IPR with the 3000 mile oil.

The Procedure:

I removed the plug on the top of the high pressure oil reservoir and took my tried and true turkey baister (equipped with a rubber fuel line and then steel brake line attached to the rubber fuel line so I could get through the small hole and go to the bottom of the reservoir to extract ALL the oil), and proceeded to extract all the oil out of the reservoir which took some time, but ended up getting a full quart out of it. Draining this HP reservoir really saved a big time mess!!

Next I drained my fuel filter bowl and loosened the lid to ensure all the diesel would be able to drain, then removed my intake "Y", stuffed shop rags in the ports and proceeded to loosen all the hoses and wiring harness associated with the fuel filter housing/IPR. I then removed the two bolts holding the fuel filter housing on the engine and lifted the housing up and out of the valley of the engine.

I then removed the cheap nut holding the IPR solenoid on and slid the solenoid off. I then took a deep socket and slowly removed the IPR.

I then cleaned around where the IPR was with a lint free cloth to ensure the new o-ring wouldn't be damaged by dirt/trash upon seating. I then coated the NEW IPR o-rings etc. with new engine oil and replaced it back into its respected provision. I then reinstalled the IPR solenoid and tightened the cheap nut ensuring I had the wiring harness connector turned in the correct direction.

I then took carburetor cleaner and sprayed the valley where a little diesel and a small amount of oil had spilled. I cleaned the entire valley and then reinstalled everything previously removed.

I then took a small funnel and poured exactly 1 quart of new oil back into the HP oil reservoir and re-installed the plug.

After the engine turned over a few more times than usual it cranked. After warming the engine up, I then proceeded to the highway where I ran locked out of OD for about 5 miles at 3200 rpm's to eliminate all the air from the HP oil system.

After returning home I immediately noticed the idle was more stable and after putting 100 or so miles on since the change, I can definitely tell a difference in the performance and idle characteristics of the engine. I used to have what I call a missing cylinder flutter sound and that has for the most part been eliminated so far. The truck also runs somewhat easier going down the highway and the cranking time which was actually normal before, is very quick now, even on initial startup in the morning. I was surprised by this because the truck actually cranked normally with no long cranking time hot or cold. I'm also interested to see if fuel mileage will fluctuate some and I'll post when and if it does indeed increase.

I wanted to post this information for some of you that are experiencing some of the characteristics my truck has been having. I'm also going to replace the ICP when I find a good price on one, but I do my truck as I do my race car and change ONE thing at a time so I'll know what the part actually did and IF it actually changed anything. Then I can go to the next step and change something else.

[MassCJ5]

Ah yeah that doesn't sound too difficult. But like I said at the diesel stop, since I just had that replaced I'm gonna go ahead and run it over to Varsity and let them at least hook their scanner up to it. If that IPR shows to be the problem, I'm just gonna take it back home and make my guy up there fix it. I mean I did pay him $540 so I think he should make it right.

[Chadnutz]

If you are forced to do the stuff yourself let me know. I changed my high pressure oil pump gasktet so I had to remove all that crap.