Truck misses/stutters when hot
 

Background- 1999 24v Cummins. Mechanical fuel pump, Blue Chip Diesel VP44

Truck seems to have constant nagging fuel problems. Replaced the mechanical fuel pump today after noticing it dripping fuel on the ground and the truck felt like it was shaking/missfiring.

After installation, the truck ran fine. It made good power and all was well. After driving 3-4 miles, the truck started bucking and kicking like it was missing on random cylinders. Let it cool down for an hour, and it started running fine again. Another mile or two of driving and the symptoms came back...... but worse. Pulled into a parking lot and shut the truck off for 10 minutes to cool down. Started it back up to make the last trek home and it ran fine again for a few more minutes.

The truck starts fine, both hot and cold. It stays around 19psi of fuel pressure, and runs fine when the engine is still fairly cold. In the gasser world, it has the same symptoms as an O2 sensor or CPS going south.

Any ideas? Ditch the VP44 and all the electronics in favor of a 160 P-pump?

my boss owns a 99 24valve an it had the same problems, turn out the wire harness that plugs in the injection pump are loose an worn out so it would act stupid just like that then run fine sum times.... hope this helps maybe wiggle the plug while lettin it idle an see if it the problem!!!

I'll give it a shot tomorrow

Not on your life.:dang:

I could also mention the lack of black smoke. It was nice to see it not smoking, but now it has me worried.

APPS symptoms include surging? It has no dead pedal, and tach works fine. Tomorrow maybe we'll try cruise control to bypass the APPS

Check codes

I'll check them in the AM as long as a standard OBDII scanner can check all of them.

It should be able to give you basic codes some may not be given a full definition in the scanner but should give you the code numbers. Also go over your ground wires all that you can find very carefully inculding battery terminals clean and tighten if neccicary. And if you have trouble with the scan tool you can pull the codes manually by cycling the key on and off 3 times on the 3rd cycle leave it in the on position and the codes will be displayed in the odometer area.

The on board scanner (the odometer scan) isn't a part of life on the 99's and even on the later years that have it's next to useless because it only shows very few codes. Just don;t want somebody readin this thinkin that because their on board system doesn't show any that they are in good shape, you really need a reader.

Yeah doesnt work at all on a 99 and I wouldnt waste my time with the key on/off on any other year either. A scanner (or Smarty) is what you need.