This car has had a intermittent fuel starvation problem I have not been able to solve for about a year now. It is ok when the weather is cool. The problem begins to occur when the ambient temperature goes above 70 and I have driven it awhile. When in wide open throttle the fuel pressure drops and the engine falls off. It is a 68 dart with a 505, cammed so mild it sounds like a stocker when it idles and I drive it daily. I make about one trip a month to the track where it runs 7,70s. Its not that quick so it doesn't seem the fuel demand would be that high.

The entire fuel system is new including the fuel tank and a 1/2 inch pickup. It currently has a holley 110 gph electric fuel pump with regulator set to 7 psi. The fuel line is 1/2 inch from tank to pump and 3/8 from pump to carbutetor. I only run at the track with fuel tank full. I have also tried it with a carter 120 gph mechanical but it has the same problem. I have tried both in series and still have the same problem. The fuel line is routed in the stock location and has to cross over the exhaust system on the right side before it gets to the engine. I cannot find a way to overcome this without running the fuel line inside the car but I do not want to do this. I have the fuel line insulated where it crosses over the exhaust just in front of where the tailpipe arch is located.

This problem has me frustrated that I cannot solve it. This fuel system is the same as I have used on other cars that worked well with no problem. Any suggestions would be appreciated and also I would like to hear how some of you have routed your fuel lines and where you have your electric fuel pumps located.

Thanks for any suggestions.

Roger

do you have a fuel pressure gauge in the cockpit?

Yes I do and I have the fuel pressure set to 7 psi. When the engine lays down the the fuel pressure will drop to about 1 psi or less. However this problem goes away when the weather is cool, about 65 degrees or less.

Since this type of setup has worked for me before (20 plus years ago) and since it seems to be so temperature sensitive I am wandering if the fuels blends available today may vapor lock much easier than before. Does anyone know about the fuels we get today? It seems it might blended different (vaporize much easier) since everything is fuel injected today.

Roger

110 fuel pump seems small to me. how old is it?

that's correct about fuel volatility nowadays. i have a similar combo- 496 in an a body, street/strip. it runs 7.0 at 3500 feet in blazing desert heat. stock fuel tank, carter mechanical pump, 3/8 line, and no fuel delivery problems at all. as a matter of fact, it had no problems with the 5/16 line either! i suspect you've got a problem possibly with your pickup, or with your system configuration. have you tried running both pumps? what kind of filter arrangement do you have?

The fuel pump is about 2 months old with maybe 500 mile on it.

Guys with stock tanks, where do you have your electric pumps mounted?

Thanks,

Roger

Joe Ewing has a 63 Dodge NSS car stock gas tank with a holley blue pump. He runs 10.30's all day no fuel issues. One thing that may help is the 2 carburators on the crossram, twice the fuel already in the carbs vs single 4bbl.

i have mechanical only. i may add an electric if i make more power. what type of filter do you have? where is it located?

How far back into the tank does the 1/2" pickup go - enough to insure it doesn't get uncovered on acceleration? Where is the fuel filter in relation to the pump, and how close is the pump mounted to the tank?

Personally, I do not trust any in-car mounted fuel pressure gauge. The positioning of those isolators can be tricky, and have heard guys say they get flaky readings from them (assuming you are using an isolator, since the gauge is inside the drivers compartment.)

You might also check your needle and seats to make sure nothing is stuck in there. I had that happen before where a little piece of rubber from a braided hose got lodged in there.

What kind of vent is on the tank? If just a vented cap make sure that it is in fact a vented cap. You could be pulling a vacumn on the tank. Jim

todays pump gas is junk and does vaporize at lower temp with 10% Alch.

run a return line and it will keep from vapor locking

Thanks for the posts I have seen so far.

The fuel filter is an inline type between the fuel pressure regulator and carb. It has 3/8 inch connections.

This car does not have a vented cap. The vent is a 1/4 inch tube that runs from the top of the filler neck and terminates inside the frame rail with about a 1/8 inch orfice in the end. I have removed the vent tube and checked to make sure it is open. Also drilled it out to the max opening possible with a 1/4 inch tube.

The pickup is located in the lowermost portion of the tank and I also run the tank full when at the track to make sure the pickup is never uncovered.

Since it seems to be temperature sensitive I am thinking it is vapor locking.

I am considering running the fuel line inside the car it get it away from any heat.

Thanks,

Aeromotive makes a in tank sump and pump now if you want to use a stock tank ..

Looks decent to me

if it was vapor lock i would think it would happen sooner but i will tell you that the mallory 140 pump with return style reg (4309) was one of the best things i have done to my car. i had bad vapor lock issues with original six pack setup i had and that took care of it

also, i dont think fuel line inside the car is a good idea

Unhook your fuel line from the carb and stick it in a 5-gal bucket. Run pump and use a stopwatch to time how long it takes to fill the bucket.

Post results back here tomorrow before 4:00 PM Eastern, I have something to do after that.

"The fuel filter is an inline type between the fuel pressure regulator and carb." Without a filter between the tank and pump the inlet screen in the pump may be plugged.