Engine/Transmission (1994 - 1998) Keep losing engine prime

[LittleSmoker]

During the middle of a trip to Alaska, had the truck repaired at Anchorage Dodge for a diesel fuel leak. From that point on, I have had loss of prime problems. Two mechanics on the way south, found what they thought was the problem, tightened things up, but it didn't fix the problem. Prior to the trip, replaced the "notorious" return line, so that is new. But we're stumped now. There are no visible leaks in the fuel system. I have the Prime Loc system, which was temporarily removed, but the problem persists, though it improved briefly, but got worse again. There were no starting or prime problems prior to the replacement of the metal fuel line in Anchorage. Only a diesel leak dripping on the ground. The mechanic at home here who removed the Prime Loc to try to isolate the problem, checked the check valve in the lift pump, and it appeared to be okay. Would really appreciate any pointers or suggestions.

 

[Joe G.]

It's most likely an air leak in the supply line hose. You should have replaced both hoses when you did the return hose. An air leak in the hose will not be visable. How did you check the check valve? There are three of them. Where was the fuel leak? How did the mechanics fix the fuel leak?



If the problem persists then read this:



http://dieselram.com/ubb/ultimatebb.php?ubb=get_topic;f=45;t=000007

 

[crabman]

Did you replace both fuel lines using marine grade hose? 1 is 3/8" and the other is 5/16".

There is formed one(curved) near the fuel heater also that can suck air.

Hope you find the problem.

crabman

 

[crabman]

Joe G has the fix for the fuel heater leak @ electrical connector.

Thanks Joe!

crabman

 

[LittleSmoker]

Thanks, Joe G for coming back so quickly. I'm going to take my truck back to the mechanic today to try to narrow the problem down further, and this info you are giving me will really help. To answer your questions, first, you're right I should have replaced both hoses (20-20 hindsight). The check valve(s) was checked by the mechanic. To my understanding, he did a pressure test. But he didn't mention what the pressure was. He just said that the check valve was working fine. I will ask him if that included all three check valves. As far as the location of the fuel leak, the initial leak that I had repaired at Anchorage Dodge was the metal fuel line from the transfer pump to the filter. That is what was replaced. Other small leaks were encountered at later dates. One was one of the fuel lines for my Prime Loc system, and the other was down low at the original fuel filter location. They were taken care of by tightening the hoses, and there have been no visible leaks since. I replaced the "infamous" 12-valve return fuel line that was mentioned in TDR Issue 35, page 17, before my trip, but that was the only fuel line that I had replaced then.

 

[LittleSmoker]

Thank-you, Crabman, for helping me out. To answer your question, just the short, elbow-shaped, hose was replaced prior to my trip. I did not replace the longer hose. I believe they were 5/16. And I doubt it was marine-grade hose as it was purchased at the local Dodge dealer. You mentioned that there was a formed, curved, hose near the fuel heater. Is that one of the two hoses you mentioned, or in addition to them? Thanks again for any help you can give me.

 

[Joe G.]

The curved hose is this one:



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[Extreme1]

Look close for any signs of seepage, they might have not gotten another fitting tight enough or you might have a bad sealing washer. If it didn't have a problem before and does now, it is probably something they touched when working on it.



Another fun item on these older trucks is the quick connects on top of the fuel tank. I had the return quick connect rust through. I wasted some time looking for new quick connects and just hose clamped the hose to the nipples on the module on top of the tank.

 

[LittleSmoker]

Thanks

I want to thank everybody for all their help, especially Joe G. and Crabman, for their suggestions regarding the fuel supply hoses. It turned out that it was the longer line that was cracked and evidently leaking air, allowing the loss of prime. The mechanic said, after a lot of swearing and a diesel bath, he was finally able to get that line replaced, and the problem is gone. He said that because of your input, they were able to narrow down the problem. He said it was a great resource. Thanks again for all your help.