Hey everyone,

The sending unit was bad in the 91 that I recently purchased and after months of just guessing how much fuel was left in it, I decided to swap it out. The fuel pump itself was looking quite haggard, so I decided to swap the whole unit while I had the bed off. I replaced it with an Airtex E7046M that I got on ebay for $50.

(side note) The new pump did not come with the cap/vent thing that plugs the half dollar sized hole on top of the pump, so I swapped it over from the old unit. No clue what that is for, or if I needed it.

Put everything back together, turned the key, after about 10 seconds of cranking the engine turned over, ran for about 45 seconds and died. I assumed air in the system was my culprit, so I browsed various youtube vids and threads on how to bleed the system but could really only find procedures for the 24x, so here's what I tried.

A) Cracked the bleed screw above the manual pumping lever on the side of the engine and cycled the lever 50 or so times, tightened the screw back down, motor cranked for about 10 seconds, turned over, ran for 30, died again wouldn't restart. Repeated this procedure a couple times, no dice on the motor staying running.

B) Cracked each fuel injector line (one at a time) while cranking for 30 seconds or so. Each time, the motor would kick over after about 10-15 secs of cranking and spraying fuel everywhere, but would eventually kick back off. After doing this on all 6 lines, I performed procedure (A) again, and it ran for about 30 seconds before dying.

C) Cracked all of the injector lines a bit, cranked for 30 seconds and sprayed lots of fuel everywhere. Tightened lines, performed step (A) again. Motor turned right over, ran for about a minute, I had a feeling of relief, until it died, and would not turn over again.

I decided to throw some more fuel in the tank, as I was not sure how much was wasted in my attempt at bleeding. Added 5 gallons, watched the gauge go up to 1/2 tank, yet there is still a "LOW FUEL" light coming up on the dash.

Before I go any further, and get any more stressed out, I figured I'd pick your guys brains in here. I apologize in advance for any noobness, this is the first diesel truck I've owned. and really haven't messed with diesel motors since high school.

Any input would be greatly appreciated.
Thanks,
-Shawn-

 

Upon further troubleshooting I'm pretty sure I got a faulty pump from ebay, but just want to clarify that I do not have something installed wrong. I pulled the low pressure line from the lift pump and cranked the engine, no fuel came out. Obviously the in tank pump isnt sending anything, so I assume the reason I was getting it to kick over on occasion was because I was manually pumping the lift pump to draw fuel into the system.

I came across this image of the top of the fuel pump. Item number 6 is what I was referring to not coming with the new pump. When I was pushing the old one out from the previous pump to switch it over, I heard a click that very well could have been the internals cracking. It looks as if a line could possibly be connected to the tip, but there wasnt one on the old pump at all... Could this valve be affecting the function of the fuel pump, or the so called "new pump" just a faulty part? Does anyone happen to know the part number for a mopar in tank pump, or an equivalent brand that is reliable.

 

Im confused when did 91 cummins come with a in tank fuel pump I never heard of that

 

Check all of your OLD rubber hoses! They may look great on the outside, but they might have Collapsed on the Inside! It is a real common problem with Diesel Fuel and Old fuel hoses !