Cummins 24v won't hold prime.

Dustball8504 · May 14, 2013

Trying to help a guy I know. He has a 99 24v Cummins with 140k on the clock. The truck is done stock but he says it won't hold prime. He says that even if he shuts the truck off for 30 seconds that it sometimes takes a minute or so to build prime back up. What would cause this to leak down? Thanks for your help!

Demon · May 14, 2013

Overflow valve. It's the banjo bolt.that holds the return line on the pump. There's a spring and check ball in it. Common for the spring to break or be so weak it doesn't seat the ball anymore. There's 2 styles. Adjustable and non adjustable. Either one can loose the spring.

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Dustball8504 · May 14, 2013

Demon said:
Overflow valve. It's the banjo bolt.that holds the return line on the pump. There's a spring and check ball in it. Common for the spring to break or be so weak it doesn't seat the ball anymore. There's 2 styles. Adjustable and non adjustable. Either one can loose the spring.

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Sounds easy enough, is this what he needs then?

http://www.ebay.com/itm/Dodge-Cummi...ure-Banjo-Bolt-Adapter-GS-BANJO-/350575981518

Demon · May 14, 2013

No. That's replaces the inlet banjo, and tap for transfer pressure through the adapter body.

What youre looking for is called an overflow valve.

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Demon · May 14, 2013

$35 bucks at Geno's garage site. This is it.

http://www.genosgarage.com/BOSCH-VP44-FUEL-OVERFLOW-VALVE-985-02-24V/productinfo/1467445003/

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Demon · May 14, 2013

Now he's got to confirm that his transfer pump is working correctly for starters as well. He must have a fuel pressure gauge? If he has a vp44 in his truck, you'd be foolish to not have a fuel pressure gauge.

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Dustball8504 · May 14, 2013

I would assume his transfer pump is working correctly, he said it starts and runs fine but it loses prime when you shut it off.

Demon · May 14, 2013

not nessissarilly. But assuming the transfer pump is working then, and there's no fuel leaks internally or externally. I'd pull the overflow and check it out. cheap to replace. easy to do.