xw383

I currently use a holley black pump with half inch line from a fuel cell. This goes to a mallory by-pass reg, half inch line back to cell. From reg to carb half inch line as well. Carb is a 850 ad mighty demon.

The problem is it runs well till half track high 7.2 secs but then about 1000ft mark it runs out of fuel. I have to feather the throttle to get fuel back to the carb.

Its very disappointing when your speed at half track is higher than at full track. I am hoping someone may shed some light on this problem.

brenx

Very hard to diagnose with too little info. More info needed please

Do you have a breather in the cell? A 1/2" one.

Where is the fuel pickup located? At the back I gather?

Where is the pump mounted? At the back under the car? It should be as close to the fuel pick up as possible.

Do you have a filter between the cell and pump? If so what type? Normal filters aren't designed to work as prefilters. Normal filters are designed to work under pressure. If you have a normal filter? You'll need to buy a good prefilter.

What fuel pressure are you running? 5 3/4psi should be plenty if set at idle.

I had the same issue as you when I used a factory tank with the pickup at the front. Fuel was moving away from the pickup and I was getting a line full of air. Hence me moving to a cell and now I've got a modified stock tank which works very well.

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XB Fairmont (street car) 11.07@123.02mph.

xw383

G'day brenden, fuel pick-up at back, breather 1/2 inch, fuel filter similar to A1 performance filter ( can't remember brand ), fuel pressure has been tried anywhere from 6-9 psi, fuel pump is mounted in the arch just behind diff. We have done a free flow test with this pump and a holley blue no problems there. I am thinking possible voltage drop at full power, maybe renew wiring and fit relay. If you want to go fast the money tree better keep growing.

brenx

If you don't have a relay fit one. Otherwise you'll be running lower voltage than you should be. Your pump may need repositioning. Keep the pump as close to the pickup as possible. Holley pumps fullstop aren't all that good in my experience. You get some good ones that'll suck fuel from anywhere without any issues yet others won't suck fuel from 12" away from the tank.

Best one I've seen to date was mounted in the engine bay! This was in a torana.

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XB Fairmont (street car) 11.07@123.02mph.

TruBlu351

Old crappy fuel filters on the pressure side can also block fuel flow.

Does you cell gravity feed into the pump or does it have to suck it up first?

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XE Falcon
393 Tremec TKO 9"

northey

That pump sounds a bit too high? Too far above the tank. I have no experience with the black pump but I would mount it low enough for fuel to gravity feed into it. Remember when the car is accelerating fuel is going to the back and bottom of the tank as well. Even if the pickup is there the pump has to siphon from the back/bottom of the tank up to the pump first. It's a difficult task for it.

Do Holleys have special needle/seat that allow you to run 9 psi?

xw383

Thanks for the replies everyone. I have a cell thats sits in the boot area and it does gravity feed to the pump. In the arch the pump is mounted approx 1/4 way up the cell. ( height wise).
Northey not sure what you mean (needle/seat 9 psi). The holley black is basically designed for methanol. Which i am definately not running or going too. Looks like i will be doing a rewire. Bugger !!!!

northey

My bad. I incorrectly assumed your cell was lower than that.

Like my answer to above this has nothing to do with your problem either; it's just a question. I thought that Holley's could only cope with 7 psi max pressure before the float spring couldn't overcome the fuel pressure. Hence the quiz about 9 psi fuel pressure?

cheers

xw383

In the carby i also run methanol needle and seats.( .150) We had this problem with a holley blue, then went to the black. Fixed that, then found out camshaft stuffed, put a new one in from John at CHI , Fixed convertor now problem has reappeared. I'm yet to have a full power pass yet.

northey

do those pumps have a relief/bypass valve in them? They can jam or be sticky at times. I only know blue pumps, never owned a black one.