Loosing prime overnight

[Diesel_Junkie]

Does anyone have any ideas? 92 cummins... looses prime overnight now. I have to manually pump the lift pump about 30 times to get it to fire these days..

I was told this could be an air leak in the return line? Does his make sence?
Is the return line submerged in the tank?

I was thinking it could also be a problem if the lift pump isnt sealing really well, put it would also have to be a non submerged return line.... i havent really checked it out yet, I am thinking of pressurizing the tank tonight and looking for leaks.

 

[steved]

I don't know if this applies to your year or not, but there is a TSB about the steel/rubber line cracking and allowing it to suck air...

steved

 

[Diesel_Junkie]

I pressurozed the tank a little, and could not find any leaks yet.

Wondering if it could be a bad injector too.

Ive got 175k mi on the origional injectores... do they wear out? I know the spyay pattern can be checked, but can an injector develop a leak to the return line? and leak in air?

Are aftermarket injectors worth it?

 

[Diesel_Junkie]

so the problem is getting worse, but i am no closer to finding root cause.

i have not been able to find any leaks yet. with this warmer weather it seems to be making the problem more frequent.

The fuel tank seems to be getting pressurized quite a bit, seems to trend with the warmer weather, and makes sence that the problem is also more frequent with lower tank levels. if its a closed loop system with a sumberged return line this would not be associated with a leak though.

Time to read the manuals more ....

any input would be appriciated.

 

[Doggy Daddy]

DJ,
I'd check the connector on the fuel heater at the top of the filter (points toward the back), disconnect it and see if it has fuel on the connector. If so then replace it and see what happens. you don't mention if the lift pump has ever been replaced; at that mileage it would be cheap insurance since if it leaks fuel can enter the crankcase. I'd start with those and I'd bet that the problem goes away. Don't forget to check the water drain when you are looking for leaks.

 

[diesel dawg 27]

man its your lift pump!!! the diaphram is leaking the fuel back into the tank

 

[PackRat]

Sounds a lot like what happened with The Crossbreed awhile back. Started really hard in the morning, but normally all day long. That did turn out to be the lift pump.

It would certainly be a cheaper place to start, than injector work.

 

[rebel_horseman]

Here are my suggestions.

The first thing I'd check is all of your fuel lines. Start at the lift pump and work your way to the injectors. Unscrew and visually inspect every connection for cracking. It's possible that the cracks may be under the compression nut.

Second, you may want to call around to some of the diesel shops that work on Bosch equipment and tell them that you have a set of injectors that you want to get checked out for leaks. While they're doing that, you can get them to clean them up real good to make sure they're up to par.

While you're at it, you can replace the lift pump. It's an inexpensive part. Piers has them for $58 and I'm sure they're probably about the same or maybe a little less at the local parts house.

Lastly, you may have a bad connection to the tank, so I'd also suggest visual inspection of everything at the tank. While you're under the truck you can check the lines in the frame rails to see if the culprit is in there somewhere.

Luck with it.