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losing prime

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My '60 B model loose prime after a day or so.  Checked all the lines for leaks but can't find any.  Could I install a fuel pump in-line or maybe a check valve.  If a check valve where should it be located?

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Coupla ideas. I had a truck that had a problem, it turned out the Strato-flex line from the tank to the pump had leaks, wouldn't leak fuel but would suck air into the fuel. When it finely got bad enough the truck would start to run like a clogged fuel filter. So if your suction line hasn't been changed in years, that is something to try.

 I also added a check valve at the tank. It is important not to increase the restriction in the suction line, I used a "swinging disk" style check as they have very low restriction in the forward direction.

 God, I miss Glenn Akers, he was a wiz on stuff like this.

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If it is Detroit powered, it need the return to the tank submerged in fuel. Tanks for other engine may just have the return dump in the top, a Detroit needs in under the fuel (it will back siphon air when not running if return is above fuel level.)

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You need to understand how the fuel system works


But as a general rule, if you loose prime when its running the the leak is on the supply line

If you loose prime when its sitting the leak is on the return to tank side 

Try putting the fuel system under some slight pressure using your work shop air compressor 

A piece of rubber inner tube with a tyre valve fitted over the filler cap hole held on with a hose clamp works well

Make sure you wind the air pressure down as low as it goes, the vent on the tank should stop to much pressure building 

Remember every little hose between the in injectors is a place to leak

And also remember you wont see any leaks on the return to tank side as they are all under vacuum not pressure so there won't be a wet spot 

Good luck 




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It doesn't really matter. The local hose shop switched to Gates, I'm not a great fan of, but had no trouble with the hose, it was more the range of fittings, that were a problem after the switch. Just want something rated for diesel, with a wire braid so it can't collapse.

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  • 2 weeks later...

Checked all fuel lines to and from the pump but still found no leaks.  Truck will start and run briefly after sitting a day or so, then dies.  Could there be a leak inside the pump itself?  I tried forcing compressed air from the tank but found no leaks.  Would a check valve be needed?

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