dynobo

Hi guys. After changing the LP and the fuel filter I have now driven the truck for about 5 consecutive days with no problems. The truck seems to run fine. Though, I have never owned a diesel so I have nothing to compare it to. Well tonight on the way home I start up a pretty long hill ( not steep just long) and I press the pedal and it does nothing. I lift completely off the pedal and go, back down and it runs fine. This happened about 4 different times tonight. I stopped by Autozone after it did this and NO CODES. What's up?????

bridinwild

Have somone check the fuel pressure coming out of the injection pump!

dynobo

How do you do this. And why would the pressure be sufficient one second and then gone a second later?

jrs_dodge_diesel

You cannot check output pressure of the VP44 (injection pump), however you can check the lift pump pressure. The lift pump is the pump that sucks fuel from the tank to feed the VP44. Ideal output of the LP is 14 PSI. Since you did change the fuel filter and were able to prime and restart the system, this indicates that you have adequate pressure (or just enough). But, you still could have a failing lift pump (these pump are notorious for dying slowly, losing pressure and output over time, and eventually taking out the VP44 too from fuel starvation). I strongly reccomend getting a fuel pressure guage to be absolutely sure on this though.

Your problem may not even be fuel related. What you described sounds a lot like the infamous "dead pedal". Your APPS (accelerator pedal position sensor) may have a dead spot, or just need to be ce calibrated/reset.

APPS reset procedure here.

Be forewarned though, this could also be a sign of impending injection pump failure. Several people have had that happen before thier injection pump failed. Normally a code will come up though, P0216 (injection pump timing control failure, aka "VP44 death code")

Let us know what you find out.

jrs_dodge_diesel

You cannot check the VP44 output pressure. The fuel injection pressure is really high, around 4,000 PSI or so. The pressure isn't simply lost, rather the VP44 returns to idle condition, either from a dead pedal (APPS sensor), or a failing control circuit on the VP44.

dynobo

Mine is a 98.5 24v. Will it still have the APPS. Also, fuel pressure is about 13psi (idle) and 10psi (WOT). I just replaced the LP a week or so ago.

JPR Ram

I agree. Try to reset the APPS first.......

budsmission

My problem is a bit different -- trouble starting when hot and sometimes when cold too. I recently installed a fuel pressure gauge and usual reading is 15 psi when I bump before start, 13 psi at idle, 10 psi at regular driving and 5 psi wot. Ny mistery is when I start cranking, the psi drops from about 15 to nearly nothing and the gauge justs flutters a bit near the botttom. Is it normal for the pressure to drop like that when cranking or is that my starting problem? Yesterday when it was not starting, I put a jumper on it and it took right off even though both of my batteries are at about 13.8 v when I turn the key on. If I crank long, the in dash voltmeter drops to about 9.

Thanks for any help you can give me. Bud

Dr. Evil

Bud, when it does start...do you get white smoke? Hard starts when warm and white smoke are classic signs of a dead Injector Pump (VP-44).

You might want to have the truck scanned for codes and measure fuel pressure at the test port on the VP-44.

Barry St John

Yep that's what mine did on a new vp44 fresh from dodge. No codes or white smoke, just occasional hard start when hot. I finally convinced Dodge to try a new injection pump and that took care of it. Good Luck!

dynobo

Bud, sounds like you have a voltage drop while cranking that temporarily pulls from the lift pump supply. You could have 1) bad batteries 2) loose connection 3) worn contact tips in your starter that is causing a high AMP draw. Check all the above and you should have ample voltage supply to the pump. Not saying it will cause the truck to start any easier it will just keep your LP voltage (fuel pressure ) from falling off so much.

Barry St John

Good advice. I built a little pigtail that plugs into to fuel pump connector for just such a test. You can moniter it with a multimeter while driving and starting and tell what is going on. Many times it's something relatively simple and with us all being gunshy about the injection pumps I at least usually assume the worst.

budsmission

Thanks guys! I have no codes and i don't think I have white smoke. In fact, when it is going it runs like a charm, no dead pedal etc. I'll try to find the contact tips in the starter and I will see if I can figure out how to measure the voltage with a pigtail while running-my vom has pretty short leads. Thanks again! Bud

budsmission

I was also wondering if installing a relay and running heavier wires to the pump (s) would help if there is a voltage drop.

Thanks, Bud

cLAYH

There already is a relay running the stock LP. If you have a voltage drop to the LP then you have some bad wiring some where.