Fuel pressure problems

[toysnyder]

I have a 1973 Dart Swinger with a 440 Over the winter I up graded the fuel system starting with a new fuel tank,3/8 sending unit,3/8 aluminum fuel lines,all an fittings,performance mechanical fuel pump,fuel regulater with gauage.But the problem is when the motor compartment gets hot my fuel pressure drops from 6.5 to around 2 to 3 pounds at idle and idle is rough and when I shut it off it pops from the tail pipe,but when cold it seems fine! scratching my head any help would be great! Thanks Toy Snyder

 

[67Dart273]

What brand/ model of regulator is this?

Most mechanical pumps I'm aware of should not NEED a regulator

This sounds like vapor lock. I'm a HUGE fan of "vapor return" systems.

Your car is new enough that unless you've removed it, you probably have a return line for the carbon canister system. If you can go back to an open vented system, free up the cannister tube, you could use it for a vapor return.

Wix makes two inline metal filters with a return port, one 3/8", the other 5/16

First one of these systems I ever saw was factory on my old 70 RR, 440 sixpack. IT WORKED!!

 

[mullinax95]

I had the same exact problem.
I had good fuel pressure at start up.
As the motor reached running temp my fuel pressure would drop to 4.5
I did everything to protect line from getting hot to avoid line lock.
I covered all bases far as insulating line from heat as well as phenolic carb spacer.
I finally broke down and installed a Griffin radiator and used a fan shroud.
Fan shroud is a must to direct the air directly on the motor.
I did not change anything else and have not had that problem since.
The entire car runs much cooler inside the interior car and a big difference under the hood.

 

[demon seed]

First off where is your regulator, it should be as close to the carb as possible and it sounds like it's crapping out, bad spring. Start off by replacing it. IMO

I'M running 3/8" lines, a high volume mechanical fuel pump, filter just before the reg., reg. about a foot from carb, on a big block and no problems, press. holds at 6.5#'s hot/cold it don't care..

 

[toysnyder]

To mullinax95 I have a Bcool rad and all of things you have named did'nt have this prob last year before up gradeing all of the fuel system so I'm very puzzeled even covered the fuel lines in the engine compartment with thermotech fuel line wrap! at a loss here. thanks

 

[toysnyder]

First off where is your regulator, it should be as close to the carb as possible and it sounds like it's crapping out, bad spring. Start off by replacing it. IMO

I'M running 3/8" lines, a high volume mechanical fuel pump, filter just before the reg., reg. about a foot from carb, on a big block and no problems, press. holds at 6.5#'s hot/cold it don't care..

Im running the regulater on a carb bracket next to the carb with hard lines and an fittings

 

[Johnny Dart]

Not sure why your running a regulator with a mechanical pump ?

Ever checked your fuel pressure without it ?

 

[mullinax95]

To mullinax95 I have a Bcool rad and all of things you have named did'nt have this prob last year before up gradeing all of the fuel system so I'm very puzzeled even covered the fuel lines in the engine compartment with thermotech fuel line wrap! at a loss here. thanks

Ok
I remember now.
I had a brand new Carter fuel pump on mine and (out of frustration) replaced it with just a plain stock unit. The stock unit had more pressure than the Carter. I didn't know if it was the pump getting hot or just a bad fuel pump but the stock unit is still on the car now and the Carter is in the junk pile.

Your situation sounds more baffling than mine. I just know that one of the two... new pump/Griffin radiator fixed my problem. I know that I needed that radiator because at hwy speeds my temp would get 200 or higher. It would just keep climbing.