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Replaced leaking lift pump - dying engine
Thanks in advance for any assistance.   With the great advice of all of you on this forum I replaced my leaking mechanical fuel pump on the 8.3.  I am now experiencing issues with keeping the engine prime and the engine running at idle.  In order...

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Re: Replaced leaking lift pump - dying engine
Reply #1
Since you are having to prime to start repeatedly, sounds like to me, you have air entering the supply line, causing fuel to run back into the tank.  Did you open anything else in the fuel line that could maybe be leaking air, injector, hose,...

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Re: Replaced leaking lift pump - dying engine
Reply #2
Jack,

I will inspect the connections and lines when I get home off of night shift. They looked good to me and did not see anything obvious while working on them.  I keep reading reference to air getting in the lines?  I would have assumed if I...

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Re: Replaced leaking lift pump - dying engine
Reply #3
David,

A leak on the SUCTION SIDE will rarely show a fuel leak, as it is under zero pressure when at rest and negative pressure when the engine is running.  Yes, if level of fuel in tank is above the level when the leak is occurring, there will be...

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Re: Replaced leaking lift pump - dying engine
Reply #4
If you see a similar crack you might get away with splicing in a new piece to pump as a temporary fix, soon you will need to replace the entire line.

It's possible that reinserting the barb...

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Re: Replaced leaking lift pump - dying engine
Reply #5
The link in Jack's post (above) is not working for me, so I can't see where he found the cracked fuel line.  ?

If David's hand prime pump works, and builds pressure so the overflow valve "squeaks", then they both appear to be functioning properly.

...

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Re: Replaced leaking lift pump - dying engine
Reply #6
OK, I found the fuel line replacement thread with excellent instructions by Chris and Jack.  A very good primer on doing a difficult job!  ^.^d

Fuel Line replacement

More to the point of this thread, photo below shows the old hose connected to Jack's...

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Re: Replaced leaking lift pump - dying engine
Reply #7
If you fill the tank and then park the coach where the tank is uphill and the engine restarts perfectly the fuel lines are suspect

Re: Replaced leaking lift pump - dying engine
Reply #8
A good way to test for a suspect fuel line is to replace the suction side with a fuel container just outside the engine compartment. Run a new, short fuel line to the primary filter. Once it runs and then you shut it off, you can check to see if...

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  • John44
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Re: Replaced leaking lift pump - dying engine
Reply #9
Chuck,A plus for cleanliness.

Re: Replaced leaking lift pump - dying engine
Reply #10
David,

A leak on the SUCTION SIDE will rarely show a fuel leak, as it is under zero pressure when at rest and negative pressure when the engine is running.  Yes, if level of fuel in tank is above...


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Re: Replaced leaking lift pump - dying engine
Reply #11
Suction lines with cracks will often be damp, especially the generator's as it has a slight constant pressure on it. Engine supply lines may not as they are a little higher than the fuel tank.

Nothing wrong with a splice as the heat and or...

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  • John44
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Re: Replaced leaking lift pump - dying engine
Reply #12
Talked to another mechanic,some of the lift pumps have a built in check valve some don't,try putting the old one back on if the
leak is not that bad,if the problem stops it's the pump.You can still find then few and far between made in USA,I got a...

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Re: Replaced leaking lift pump - dying engine
Reply #13
I suppose the OP's problem here could be the new replacement lift pump.  Don't know where David bought the pump.

When I went shopping 5 years ago to replace my OEM pump, I took the recommendation of one of the online diesel "experts" who told me...

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Re: Replaced leaking lift pump - dying engine
Reply #14
There is no "barbed fitting" and no "rubber hose" used on the C8.3 mechanical lift pump.  The OEM braided line from the frame mounted fuel filter to the lift pump has crimped JIC swivel...


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Re: Replaced leaking lift pump - dying engine
Reply #15
Sorry,  mine has the Push Lok fittings with the barbs same as Jack's in the picture.
Yes, after seeing Jack's photo (which I posted in the next reply #6) I realized there must have been a...

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  • John44
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Re: Replaced leaking lift pump - dying engine
Reply #16
Have the JIC fittings on mine,some of the hoses are blue.

Re: Replaced leaking lift pump - dying engine
Reply #17




So, are all "made-In-China" lift pumps the same quality?  I don't know.  Is a pricey "Made-In-China" pump better than a cheap "Made-In-China" pump?  I don't know.  Is a GENUINE CUMMINS...


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Re: Replaced leaking lift pump - dying engine
Reply #18
Thank you for all that have replied and appreciate the input.  I was called back in for a double shift at work today.....  will take a look at it tomorrow and report back with my findings. 

Chuck,  I did purchase the pump you linked previously...

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Re: Replaced leaking lift pump - dying engine
Reply #19
When you say "hand priming slowly produces diesel fuel to the overflow", where is your overflow, are you loosening one of the injector lines and then re tightening?

  • John44
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Re: Replaced leaking lift pump - dying engine
Reply #20
Unless he means going back to the fuel tank.

Re: Replaced leaking lift pump - dying engine
Reply #21
When you say "hand priming slowly produces diesel fuel to the overflow", where is your overflow, are you loosening one of the injector lines and then re tightening?
Most all diesels except...

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Re: Replaced leaking lift pump - dying engine
Reply #22
This is what a Bosch overflow valve looks like on a Bosch "P" pump: Amazon.com: 1417413047 Disel Pump Overflow Valve for Dodge Cummins 5.9L...
Thanks, Pierce, for the excellent...

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  • John44
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Re: Replaced leaking lift pump - dying engine
Reply #23
While your at it get the gauge adaptor they have,easy to check fuel pressure.

Re: Replaced leaking lift pump - dying engine
Reply #24
Chuck,

When we would install a turbo on a non-turbo Mercedes 240D or 300D, we would have to recalibrate the injector pump to add more fuel. This was before the electronic machines did it and the machine would spin the pump at different RPMs while...

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