p1690 Can't find what's wrong

[Mopar1973Man]

I went the extra step and relocated the pressure sensor to fender adding 5 feet of 1/8" air brake line to allow for more fade time for the pulse to reach the sender. 

[David454]

Alright, so @Mopar1973Man I can tell you are real proud of your knowledge on snubber fittings and everything, but that was not my issue. The fuel pressure sensor is right on my Fass and now reads rock solid pressure. Thank you @Dieselfuture for the tip on the check ball, that ended up being the cause. The truck sat for a long time before I bought it and the ball had a nice grove worn in it all the way around and was sticking. I turned the check ball 90 degrees and haven't had a fuel pressure blip since. (I still plan to get a replacement ball/spring)

 

After looking at everything I had going on back to the beginning, I think that the jumping fuel pressure was the root cause. The truck would run fine for a few minutes and then start having issues. I think the pump was heating up due to lack of consistent fuel, the timing piston was starting to lock up and burning up the wires going to it. I fixed the check ball issue and the truck ran fine with the two bare wires going to the timing piston basically in the open, only enough electric tape to keep them from grounding out on the pump. So I know the sheathing wasn't part of it either. Before the fuel pressure would jump from maybe 12 to 18 on my edge monitor,  and you could hear the pump pulsing clearly while the issues were happening. 

 

Now FP is rock solid between 15-16.5 psi depending on throttle position and fuel temp. Pump sounds smooth and consistent.  I know that during this mess (I probly put 800 miles on the truck with the fuel pressure jumping like that, solid 200 of that towing 9k+) the injection pump had to have taken some permanent damage, and it was original with 160K on the clock so I put a reman pump in from DAP and it has been doing great for the ~500 miles since then. 

 

Thanks again for all the help gents! I hope people can use this to solve some of their problems down the line, as I know I have 100's of old threads before it. 

 

 

 

[Dieselfuture]

Glad you figured that out, hey needle valve before the gauge is a good idea to dampen the pulses from the vp44 so you don't destroy your gauge. And you don't really need a new spring, you can modify your old one to look like this, then get a new check ball from fass it is white plastic. And this is my T with needle valve, then another T to mechanical fuel gauge and then electric one for the quad.

 

 

[Mopar1973Man]

My gauge senders are not even on the engine, but the driver side fender for easier testing and diagnostics. 

 

This is all I've got at my tap point. A shut off valve, then the sinstered metal snubber, and the the Push To Connector fitting. (PTC).