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Anyone bounce their DS4 off the governor like a gas engine?

WarWagon

WarWagon

Well it hits on 7 of 8...
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Not sure what I have going on. During the fun snap emissions test the engine acts like it cuts fuel and then puts full fuel back on. Just like a gas engine held on the RPM governor. Smokes bad and sounds like cr@p when this happens. Maybe could be said as 'the engine is breaking up' with random misfire at high RPM. Just during the snap test. Runs fine under load.

I get fishbite now and then and was bad the other morning esp with the cruise on.

Grey PMD about 3 years old on the bumper. Prime suspect. So is the tune as the cut out RPM appears to affect this. Cat on it from a 2008 Duramax is also failing by rattling - must be coming apart. But did this some last year without cat issues.
 
I have never done it unloaded but have held a gear too long (just accelerating not towing) and it runs out of fuel and spews black smoke. Its like it can't fuel enough for boost and chokes. It then kinda bounces on like a governor, smoke clears a little, but feels weak on power and maybe surges a bit. I haven't held it that long to really describe it or try and see what its doing but yeah I guess it does feel like its missing.

I wonder if the IP plungers just can't fill or IP internal pressure drops and things get screwy. I don't think its valve float its fuel related.
 
I was wondering if it is a sign of IP failure. Maybe wear causing the plungers to not fill (like said above) or a similar issue.

Is LP pressure staying up?
 
It's like a fuel cut off. I did a light run up a bit ago didn't hold pedal to floor and its different. Its not as smooth as a rev limiter. Had a friend with a 6.0 Ford that could hold a gear with foot on floor and it would run up and hold 4000? RPM steady. Its like poor programing fuel cut off or defuel.

The worst I have experienced it was a down shift going too fast and almost as bad another time accelerating going down hill held gear and the fuel ran out sort of.

Of course my IP is old 220K plus and does weird things sometimes. I have a supply fuel pressure guage and it shows a bit of fuel pressure (doesn't peg 0) if I floor it up through 3200RPM but sometimes if I roll up into fuel and accelerate with boost it can drop to 0 fuel pressure. So some internal IP pressure regulation is suspect.

One day I'll install the Walbro :rolleyes: and see if a bit of extra supply pressure helps.
 
It is 3600 RPM where you hold it steady for the stupid snap smoke test. I have a Mallory 250 GPH fuel pump on it. The accelerator on 6.5 diesels is really more of an RPM request. So it doesn't hit a cut off rather it gets to the top RPM and tapers fuel off to hold the max RPM.

I'll try the factory tune and narrow it down.
 
I tried this earlier today. My truck sits at about 3900rpm in park with foot to the floor and makes no rev limiter noises. It just sounds like an engine turning 3900rpm... as if it were a gas motor just holding 3900rpm neutral free revving at part throttle.
 
SuperSport01 said:
I tried this earlier today. My truck sits at about 3900rpm in park with foot to the floor and makes no rev limiter noises. It just sounds like an engine turning 3900rpm... as if it were a gas motor just holding 3900rpm neutral free revving at part throttle.
Click to expand...

This is what is is supposed to do. Has to for the snap emissions testing.
 
So far and no change:
PMD swapped with known good.
Factory tune.
APP swapped out with spare.
Fuel Pressure 10+ PSI - doesn't change with the overkill lift pump I have.

Press throttle to get red line - fine. Press throttle more and it starts to miss/cut fuel/surge.
 
Bump. I guess when I run into something it is a real mystery. :scratchchin: I have noted others with this issue and no solutions.

Is there any feedback on timing that will set a code if the stepper motor is unable to move enough? I'll do a TDCO learn and timing set and see if that makes a difference. It was suggested to me the stepper motor may be having trouble and this acts just like a DB2 with inop advance. I may have to move the pump advanced...

Useful info that didn't answer the code set question:
http://www.thetruckstop.us/forum/showthread.php?11754-FYI-TDCO-Timing-the-DS4-Injection-Pump
 
Idk, my stepper motor is off and makes timing sketchy but I still haven't had this issue. My truck likes to pulse going down the highway if that helps. Light 100-200 rpm fluctuations up and down but not constantly.



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