7.3 only starts when cold

6.4 Stroker · Jul 9, 2015

My brother has a 02 7.3 that's only starting when cold.
I plugged in my Auto Enginuiety so see what I could find. Came up with the typical p1280 and p121 codes.
When the truck is cold, it cranks longer than normal, but still starts ICP duty cycle starts around 20% and climbs up to 80% just before it finley starts.
When engine is hot ICP won't past 260psi even with 80% duty cycle.
Tried unplugging ICP sensor and no change. Threw a new ICP sensor And CPS sensor no change. Cleaned the IPR valve, and tried a known good IPR valve and no change. When the truck is running ICP is around 530 psi with duty cycle of 9-10%. Spliced new pig tails for ICP and IPR and nothing. Checked the fuel bowl and doesn't seem to be any oil contamination from bad O-rings.
I'm starting to run out of ideas.
Any thoughts or suggestions are appreciated!

97f350stroker · Jul 9, 2015

I just ran through the same issues with mine and it turned out 6 out of 8 of my injectors had torn o rings. No evidence of fuel contamination either and almost the exact DC and icp readings you are experiencing

NC714 · Jul 9, 2015

Sounds like a high pressure oil leak, if you have already eliminated the IPR then I would suspect as mentioned above the Injector O rings, or injector itself (stuck poppet or something).

I would remove valve covers and run the engine, inspect the oil spouts to see if all injectors are firing properly and if any visible leaks are present.

6.4 Stroker · Jul 9, 2015

That does make sense. He installed some single shot 175/30s I wanna say around 40-50k miles ago. Maybe he cut an O-ring during installation.

NC714 · Jul 9, 2015

That would have probably showed up immediately after install. Seems like I did read about a "bad batch" of injector O-rings that were causing issues later down the road for people.

lincolnlocker · Jul 9, 2015

this just happen all of a sudden or has it been slowly getting worse then finaly wont start?

live life full throttle

6.4 Stroker · Jul 9, 2015

I'd say off and on for a few months slowly getting worse.

Layson · Jul 9, 2015

Had a coil on the IPR go bad that would only let the truck start when it was cold. That is the big washer deal that slides over the IPR.

6.4 Stroker · Jul 9, 2015

Tried another IPR from dad's truck starts every time!
Wide open 80% duty cycle pressure drops to 1600psi.
So a bad IPR and weak HPOP sound about right?

444getsitdone · Jul 9, 2015

How many miles on this thing? Unless he neglected his oil changes (never happens!) I'd not guess the HPOP, possibly IPR, unlikely.... pull the VC's and check the injectors, are they spraying oil everywhere? The cold thick oil does not leak as much and the HPOP can keep up with the loss, once it warms up the thin oil leaks a lot faster, faster than the HPOP can keep up. I work on the Caterpillar HEUI's quite often and the HPOP do go out on them quite a bit but the things have a lot of hours on them, and the owners dont always know about oil changes... Dead head the HPOP if you think its that, then you know for sure if it is (or is not) the HPOP. 1600 PSI is not bad for the pump, 80% duty is high but its trying desperately to make more pressure. I think youre losing it somewhere else

lincolnlocker · Jul 9, 2015

stock tuning, wot should hold 2600-2800 psi all day long.. now either the hpop did in fact say *** you im out or the injectors are way bad.. could be both. how many miles are on it?

live life full throttle

6.4 Stroker · Jul 9, 2015

Truck had 435,000 miles. Been stone cold reliable!
Oil changes range between 3500-4500 miles

lincolnlocker · Jul 9, 2015

6.4 Stroker said:
Truck had 435,000 miles. Been stone cold reliable!
Oil changes range between 3500-4500 miles

holy ***in chitballz... just replace hpop and injectors.. if thats all thats happened so far then the ole girl could use some fresh high pressure parts!

live life full throttle

lincolnlocker · Jul 9, 2015

it deserves it..

live life full throttle

lincolnlocker · Jul 9, 2015

ih designed it to be a half million mile motor then be rebuilt or freshened up..

live life full throttle

Arisley · Jul 9, 2015

444getsitdone said:
How many miles on this thing? Unless he neglected his oil changes (never happens!) I'd not guess the HPOP, possibly IPR, unlikely.... pull the VC's and check the injectors, are they spraying oil everywhere? The cold thick oil does not leak as much and the HPOP can keep up with the loss, once it warms up the thin oil leaks a lot faster, faster than the HPOP can keep up. I work on the Caterpillar HEUI's quite often and the HPOP do go out on them quite a bit but the things have a lot of hours on them, and the owners dont always know about oil changes... Dead head the HPOP if you think its that, then you know for sure if it is (or is not) the HPOP. 1600 PSI is not bad for the pump, 80% duty is high but its trying desperately to make more pressure. I think youre losing it somewhere else

You know, as bass akwards as you came at this, it still was pretty much spot on.

lincolnlocker said:
stock tuning, wot should hold 2600-2800 psi all day long.. now either the hpop did in fact say *** you im out or the injectors are way bad.. could be both. how many miles are on it?

live life full throttle

Yep, abso***inlutly. all day every day.

6.4 Stroker said:
Truck had 435,000 miles. Been stone cold reliable!
Oil changes range between 3500-4500 miles

lincolnlocker said:
holy ***in chitballz... just replace hpop and injectors.. if thats all thats happened so far then the ole girl could use some fresh high pressure parts!

live life full throttle

I will also add my holy ***in chitballz to this.

lincolnlocker said:
it deserves it..

live life full throttle

lincolnlocker said:
ih designed it to be a half million mile motor then be rebuilt or freshened up..

live life full throttle

Time to make a decision. Myself, I would throw some injectors and a HPOP at it and ride it to the end. Would not even throw a compression test at it. Ride that old girl for all she has. When she is done, clear a place in the pasture for her and let her live there, Never sell a part off of her and let her rust away like God meant her to.

Second choice, jerk the motor out, throw some rings and bearings at it, put it back together with a rebuilt oil cooler, new LPOP, new HPOP, new turbo, new injectors, and go for another half million.

lincolnlocker · Jul 9, 2015

Arisley said:
You know, as bass akwards as you came at this, it still was pretty much spot on.

Yep, abso***inlutly. all day every day.

I will also add my holy ***in chitballz to this.

Time to make a decision. Myself, I would throw some injectors and a HPOP at it and ride it to the end. Would not even throw a compression test at it. Ride that old girl for all she has. When she is done, clear a place in the pasture for her and let her live there, Never sell a part off of her and let her rust away like God meant her to.

Second choice, jerk the motor out, throw some rings and bearings at it, put it back together with a rebuilt oil cooler, new LPOP, new HPOP, new turbo, new injectors, and go for another half million.