Air in EFI, loosing prime.

I have an 89 7.4L, with an aftermarket MarinePower EFI kit. Once and a while I will loose prime in the pump and die, or just a backfire/miss. I can normally pull the Rancor filter/separator and find that it has 1/2 the volume of air in the filter.

This was an intermittent problem in the past, including PO. This year, I re-plumbed the system to return the fuel into the tank, where it was going into the Rancor filter, hoping that would "blow out" the air, but I had it happen again.n and it is very annoying having a dead boat on the water

My next step is to re-hose the system to lower the EFI pump as low as I can go, and replace all "suction" side hoses, to ensure no air leaks.

I have a feeling I get a 'gulp' of air out of the tank, it flows into the Rancor, and then the fuel pump gets starved and looses prime. The fuel pump was replaced this year. They appear to pump well, but may not create as good suction when no liquid is present.

By lowering the pump, I hope to give it as much liquid as possible to re-prime and blow out the gulp of air. new hoses in case of any slight leaks.

Any other ideas?

==> I found a Don S post about a 2 pump system for volvo and was wondering if that might be an option, a low pressure, high volume pump between the tank and reservoir, and then a high pressure pump between going to the rails
My thought was use use the Rancor in place of the reservoir.

==> another thought was some form of "fuel bulb" that I could re-fill the Rancor, plumbed in parallel.

Current Plumbing:

Tank --> Rancor 3232 (18" distance), Rancor base is about 6" higher than top of tank.
Rancor --> Holley pump (18" distance), pump is lower than Rancor and about 1/2 way up tank
Pump --> EFI Rail (4 ft)
EFI --> fuel cooler (3 ft)
Fuel cooler --> tank (2 ft)

Re: Air in EFI, loosing prime.

Eagh... you don't have to go to crazy relocating this and that. Just start with the tank fittings and take everything apart 1 by 1 and put it all back together with pipe dope with teflon.... not teflon tape. Obviously all suspect hoses should be replaced as well.

Re: Air in EFI, loosing prime.

First of all, it Racor, not Rancor. Here is their Logo


Before you start throwing a lot of money at it, start doing some testing.
Something as simple as using the wrong kind of fuel line, or the wrong kind of clamps could cause your air problem.
Here is a start for testing your boats fuel system.
http://forums.iboats.com/showthread.php?t=283269

==> another thought was some form of "fuel bulb" that I could re-fill the Rancor, plumbed in parallel

Click to expand...

Don't build your self a monster. You need to cure your problem, not cover it up with bandaids.

Re: Air in EFI, loosing prime.

Thanks for the input. In the EFI manual troubleshooting tip #1 is "fuel pump below fuel tank" can't do that (I would think that would be really hard in a boat...), but I can get it as close as possible... I will replace the old lines and use the testing rules on your link Don S.

Yea, I don't want to create a monster. It is a PITA to get the boat running without a little extra fuel to fill up the Racor (thanks for the correction)


Thanks