I keep killing fuel pumps

kwijmbo · Post by **kwijmbo** » Fri Dec 22, 2006 12:58 am

As you know I'm running a rotary in my car, but still got a weird problem you might be able to help me with?

The fuel system in my car is as follows.

Tank to standard MY subaru fuel pump to 1.3 litre surge tank. Volvo pump from surge tank to engine.

I wouldn't think the actual labour on the subaru fuel pump would be that increased considering the size of the surge tank yet they keep overheating and dying on me.

Any suggestions or ideas? anyone recommend a fuel pump perhaps that I could use in it's place?

cheers in advance
Paul

fredsub · Post by **fredsub** » Fri Dec 22, 2006 7:24 am

Is fuel return back to surge tank or fuel tank?
Even tho that fuel pump is running into low pressure, I expect its running at its max rate all the time hence the overheating. I might suggest maybe a carby pump from a bigger engine, v8 or something?

waggaclint · Post by **waggaclint** » Fri Dec 22, 2006 7:58 am

i wouldnt run acarby pump on a rotary....if a rotary runs lean it will kill it real quick...its a defanet no no on a rotary if anything you want it a bit rich they are very expensive to fix when they let go ive worked on a lot of rotarys hey...we used to fit bosch 040 pumps to em hey.....

MY_STI · Post by **MY_STI** » Fri Dec 22, 2006 8:21 am

If the return line from the engine goes straight to the fuel tank, then there is no way the subaru low pressure pump could keep up with the flow rate of the high pressure pump, surge tank or not. The higher pressure would be trying to drawn more fuel through the low pressure pump, which would overspeed it considerably, nor would it be good for the high pressure pump. High chance of leaning out as well.

If the return line is plumed back to the surge tank and then to the tank, the low pressure pump may not be pumping against enough pressure, so it will tick over a little quicker than its meant to.

My fuel system is like the latter, I added a restriction to the surge tank to fuel tank return line to create some pressure in the surge tank, this slowed the pump down a little when the surge tank was full, although the main reason was to make it a little quieter.

I would not reccomend doing that on a high performance engine though, as fuel temperatures will be higher than if the return line plumbed straight back to the fuel tank.

A low pressure pump that exceeds the flow rate of the high pressure pump would probably do the trick, with the return line taken straight to the tank. Holley make an assortment of suitable pumps.

Hope you sort it out.

tim_81coupe · Post by **tim_81coupe** » Fri Dec 22, 2006 8:23 am

Looks like he's using a Volvo EFI pump for the engine supply Clint. The Subaru pump is for filling the surge tank.

I never bothered with a Subaru pump to tell the truth. I bought a brand new carby fuel pump and used that in my coupe. It was a Facet Red pump (aka a "boat pump".. lol.

The stock Subaru pump has very low pressure and flow ratings, and I had heard somewhere before (USMB?) that if run at full speed for a long time they'll cark it....

kwijmbo · Post by **kwijmbo** » Fri Dec 22, 2006 5:50 pm

thanks for all your help guys

yes tim is spot on. volvo pump supplies the engine. The return does go back to the surge tank.

I think like tim described the subaru fuel pump is just going nuts with the full time running and just overheating and dying. If i let the car sit and fuel pump cools down, it works again.

Paul

Suby Wan Kenobi · Post by **Suby Wan Kenobi** » Fri Dec 22, 2006 11:51 pm

You could either run another EFI pump as a primer pump or get a holley ora Facet fuel pump, i have used either of those on engines years ago and found the facet a bit of a suprise performer although the holley was still great.

YouTube · Post by **El_Freddo** » Tue Dec 26, 2006 7:39 pm

MY_STI wrote:A low pressure pump that exceeds the flow rate of the high pressure pump would probably do the trick, with the return line taken straight to the tank. Holley make an assortment of suitable pumps.

I second this... so long as the return line straight to the tank is from the surge tank and NOT from the engine return line...

my two bobs worth.

SuBaRiNo · Post by **SuBaRiNo** » Tue Dec 26, 2006 8:25 pm

I blew my MY fuel pump that was feeding my surge tank also... not long after doing my conversion... changed it for an L series carb pump and it has been fine ever since.

Dave