I am running into frusterating fuel system problems that I can't seem to work out. If some of you who know more than I do about this could help me out I would really appreciate it.

The vehicle is an 89 f-150 long bed single cab that is lifted on 33s

The engine is a 349w stroker with 190cc TFS FAC heads, 750 quick fuel street strip carb (double pumper) with a electric choke, .598 lift HR cam, air gap intake, msd dissy and digital 6 box, 125 shot of nitrous...just your basic mild stroker motor.

The fuel system is a stock tank (15 gal) stock pick up that has been modified for a external pump (cut out the intank pump and used 3/8ths rubber hose to extend 3/8ths hardline to where the factory fuel sock sits). Off of the top of the tank I have a -6an line going to a trick flow fuel filter with -6an line going to the aeromotive ss (140 or 150gph) pump that is mounted below the tank so it is gravity fed. If you take the supply line off of the pump fuel will siphon out. The pump is being powered with the factory wiring harness that uses the same size wires that the pump has coming off of it. Out of the pump I am running -6an line all the way down the frame to a aeromotive fuel filter. Then it goes into a Mallory fuel presure regulator that has 2 -6an lines going to the carb and one going into a 3/8ths return line. I beleive the tank has a 1/4in vent on the tank it might be 5/16ths but the hose is ran to where the factory charcol canister was.

The truck was fuel injected from the factory and for years I ran a carb and used the stock intank electric fuel pump on a toggle switch which worked great.

The problem I am having is the truck runs great for 20mins or so street driving and then loses fuel pressure and the engine shuts off. If I get on the throttle fuel pressure falls. Once the truck shuts off if you come back half an hour later it'll start right up and run like it did before it shut off. I have put a full tank of gas in it (to be absolutely sure the pick up is covered) and left the gas cap loose and it still does the same thing so I do not think it is a vent problem. I've been noticing recently that the fuel pump will sort of surge when acting up you can hear the whining change pitch. On the dyno the fuel pressure kept dropping 2psi as soon as the wheels cought up to the 4,000 converter and rpms started going above 4k

This is driving me absolutely nuts because I can't drive my truck and can't even spray it. If someone could give me some ideas on what to look at i would really appreciate it.
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Safe assume you mounted the pump according to the manufactures instructions? Gotta believe ya did.

And that you did not disassemble the pump at any point and did not attempt to adjust the outlet pressure screw?

According to the instructions you can run the pump configured for "dead head" or "by pass" arrangement, either setup utilizing pressure regulator.

Have you blocked off the return line, test it see if its a problem in the return system as in a regulator issue?

Something in the system causing the pressure head of the pump itself to cycle "off"? when should remain on all the time in the fuel return arrangement you installed it in.

 

That's not a bad idea of blocking off the return line and seeing what happens

I have never taken the pump apart or adjusted the pressure screw

When the truck dies the fuel pump is still making noise so I assume it is still running.

It sucks because in order to duplicate the problem I have to drive for 20mins or so or stand on it in town (35mph speed limit) and coast into my driveway.

 

I was thinking that I could take a factory in tank pump and put it in the tank to feed the aeromotive pump, would that create a restriction?

 

decided to quit *ucking around with it and just put in a walbro 255 pump and sell my shiny aeromotive pump to someone who has a sumped tank with a fitting on the bottom so it is truely gravity fed not just siphioning (butchered that word) into the pump