Modified 6.4 - Air in Fuel - 7 wks without truck - please help

MT_Diesel · May 28, 2015

Great, thanks Jared! Good to know as the seller didn't disclose that when I asked about previous service/maintenance. That's a plus that the pump is new. Oasis report said factory pump was also replaced under warranty at 66k miles.

Have you had a chance to look at the fuel diagram I posted? I'm definitely interested in your thoughts on it. Also, would a cracked injector cup just pressurize the return and not the high pressure part of the system?

I think I'm going to trailer it to a more competent shop 2 hrs away, but want to be sure if the dealer cracked one of the cups installing the injectors they fix it on their dime.

MT_Diesel · May 29, 2015

78f100 said:
If it's putting air/compression back into the pump, though it is technically a low pressure issue.

The quote above is why I said a cracked cup could cause the issue, plus I had it happen to me as well.
if the problem is limited to one bank I doubt that is the problem though.

So I take it the cracked cup pressurized the return and affected both banks on your truck. Do you have a single or dual pumps? Did you test for aerated fuel at the fuel cooler and if so what Did you find?

78f100 · May 30, 2015

MT_Diesel said:
So I take it the cracked cup pressurized the return and affected both banks on your truck. Do you have a single or dual pumps? Did you test for aerated fuel at the fuel cooler and if so what Did you find?

I have the same diesel dr kit you have. I never isolated it to one side. I knew I was running out of fuel, but never could figure out why until I removed my elite regulated return and bowl delete. I always monitor rail pressure and could tell when it was going to act up, rp would fluctuate then gradually fall off. So I sent the fuel back to the tank instead of back into the feed to the pumps. This solved my running out of fuel problem but I knew it was not the solution. I then tested supply to both pumps thinking a line was restricted, all tested good. I then separated the returns from the 2 pumps, with the truck running and the returns in clear containers it was obvious my valley pump was where the issue was. It would return fuel for a few seconds then foam, I thought the pump was bad. I did a relative compression test and cylinder 2 was down a little so I pulled the injector and found the bottom of the cup looked like a star.
My truck ran fine until it got to temp then it was hit and miss, sometimes it ran great other times it would just die and not restart for a few minutes.

I wonld have them isolate the returns from both pumps and look for air there. It's gonna be hard to tell much coming from the valve on the cooler.

MT_Diesel · May 30, 2015

Great, thanks for elaborating. I think we'll give that a try.

Were you getting air from the pump return or the return off the front of the head from the side with injector #2?

78f100 · May 30, 2015

MT_Diesel said:
Great, thanks for elaborating. I think we'll give that a try.

Were you getting air from the pump return or the return off the front of the head from the side with injector #2?

Pump return. On your dd kit both returns should be hooked to a banjo bolt on the fuel cooler. Remove them there.

MT_Diesel · May 31, 2015

78f100 said:
Pump return. On your dd kit both returns should be hooked to a banjo bolt on the fuel cooler. Remove them there.

Mine uses factory piping that combines return from factory pump and both returns from head banjo bolts. Return from second pump is stacked on the fuel cooler inlet banjo bolt. I'll look at isolating returns to pinpoint where aeration is coming from.