Weird HPOP pressure problem

[CurtisF]

This isn't a question about my truck, it's someone else's.

Take two almost identical trucks running stock HPOP's, and slap the exact same tunes on them.

One truck will maintain ICP at 3000 psi at WOT regardless, no matter what.

The other truck will hit 3000 psi if you gently roll into the throttle, but will peak at a max of 2200 psi in any tune if you stab the throttle suddenly (from a cruising speed or from a dead stop, doesn't matter). Even tunes that strictly limit fuel injection pulsewidth still sees 2200 psi of ICP when stabbing the pedal.

Of course when this happens the truck smokes, falls on it's face, keeps smoking and smoking and smoking, etc.

Any ideas? Is this an IPR problem, or some kind of pump issue (HPOP or LPOP)?

 

[Big Bore]

Sensor causing defueling? Same PCM?

 

[Talyn]

Check map sensor.

Are you sure injector O-rings are good as well?

Mileage relatively the same on both trucks?

 

[CurtisF]

Sensor causing defueling? Same PCM?

Check map sensor.

No defueling, no codes. Map sensor reading as it should.

Are you sure injector O-rings are good as well?

Yep, injector o-rings are good, truck doesn't use oil.

Mileage relatively the same on both trucks?

I can't remember the mileage.




Frank, it's your tuning on Kevin's truck. Never had an ICP problem on your truck. But on his, it absolutely freaks out when you stab the pedal. And you're a crazy driver anyway who hits the throttle as if it raped your dog.

 

[Big Bore]

Frank, it's your tuning on Kevin's truck. Never had an ICP problem on your truck. But on his, it absolutely freaks out when you stab the pedal. And you're a crazy driver anyway who hits the throttle as if it raped your dog.

He has the same injectors as I? And I deny all accusations.

 

[Talyn]

No defueling, no codes. Map sensor reading as it should.

Yeah, I thought that too when my Map sensor was bad.
No codes and the scangauge was reading right on.

Unplugged the map sensor, and the scangauge was still reading right on.

I was a smokey pig with the bad MAP plugged in, and it cleared up a bit with it unplugged. New sensor and all the problems went away.

It was just a thought and a simple suggestion from experience. Cause in stock tune with bad map sensor, my truck didn't smoke at all.

 

[CurtisF]

He has the same injectors as I? And I deny all accusations.

Same injectors, nozzles are only slightly larger. Nothing drastic.


And you might deny all accusations, but you know it to be true. :hammer:

 

[CurtisF]

Yeah, I thought that too when my Map sensor was bad.
No codes and the scangauge was reading right on.

Unplugged the map sensor, and the scangauge was still reading right on.

I was a smokey pig with the bad MAP plugged in, and it cleared up a bit with it unplugged. New sensor and all the problems went away.

It was just a thought and a simple suggestion from experience. Cause in stock tune with bad map sensor, my truck didn't smoke at all.

What's strange with this one is that as long as he rolls into the throttle, ICP comes up normally and there's very little smoke. It's only when he stabs the throttle that the ICP refuses to crest over 2200 psi. And this is regardless of boost, speed, RPM's, gear, etc.

 

[Talyn]

What's strange with this one is that as long as he rolls into the throttle, ICP comes up normally and there's very little smoke. It's only when he stabs the throttle that the ICP refuses to crest over 2200 psi. And this is regardless of boost, speed, RPM's, gear, etc.

Alright.

Kinda weird really.

 

[Chvyrkr]

What's strange with this one is that as long as he rolls into the throttle, ICP comes up normally and there's very little smoke. It's only when he stabs the throttle that the ICP refuses to crest over 2200 psi. And this is regardless of boost, speed, RPM's, gear, etc.

Poppet stuck open?

 

[bigwheel]

The truck is not using oil. Maybe a .5 qt 3000 miles.

The 2 trucks dont have a different PCM do they?

 

[Bean]

Gear Slip?

 

[bigwheel]

So some food for thought. I started the truck and moved it 10 feet then shut it down. After about 10 min I checked the oil level and there were bubbles on the dip stick. The level was good but seemed like maybe a little thin. It doesn't have a strong fuel smell, I am sending in a oil sample to see how that looks. Maybe injector orings? The truck does have a good amount of gray to a tint of blue smoke at start up, with raw fuel smell all day long. Thanks

 

[Tom S]

Does the duty cycle match up or is the oil pressure being bled off elsewhere?

 

[Wackerjr]

check for oil in the icp sensor... 2200 is the default off the top of my head....on edit... swap sensors from truck to truck... see if it changes.

Then next thought is weak spring, or broken spring internally in the pump.... happens more than you would realize..... truck will still run fine.

 

[Tom S]

2465 is the false reading number I seem to recall

 

[Wackerjr]

I think your right tom... also remember a nozzle increase no matter how small will make some difference in pressure....or... just a weak pump...

 

[BigAlsPSD]

Just going to throw this out there, but was about a weaker LPOP?

 

[TARM]

Did this just happen one day or was it part of a upgrade or did it come on gradually? You get what I am asking.


I am with Talyn on the fact of you can not always rely on readings looking ok as certainty the sensor MAP, ICP etc are not the actual issue. Sucks as it sure makes it harder to diagnose.

To recap,

Both trucks are running the same tunes and same injectors and hpops. As long as you roll into it the truck in questions will build to the tunes ICP requested 3K psi. If you stomp on it no matter what the starting gear, rpm, speed it will only hit 2200 and basically falls on its face with all the smoke etc that comes with it?

You noticed aeration bubbles in the oil on the dip stick after less than a min of running with 10 min rest.

What about your other truck doing the same thing?

What oils are you using? Are they both running the same oil? How many miles and time does the oil have on it currently?

Any noticeable changes with a oil change?

Can you post up some logs of the the HPOP ICP PSI Duty cycle and % along with PW and note when its stomped vs rolling into



Maybe a faulty pop off valve on the HPOP. It sees pressure spike and it causes it to maybe be partially opened/leaking but if brought up slowly it holds. Not typical but figured I would throw that out there.

 

[CurtisF]

Does the duty cycle match up or is the oil pressure being bled off elsewhere?

The duty cycle climbs and will reach 90%+