Fuel Pressure Problems...Again.

[B-Co Kid]

87 B-Co; 351w; mechanical fuel pump; fuel pressure regulator; fuel pressure gauge, edelbrock performer; c6 trans; no eec/computer;

Guys,

Im having fuel pressure issues that I cant seem to figure out.  I may have mentioned it in other posts, but haven't had luck correcting.  After cruising around, the fuel pressure drops from 6 psi to around 2 or 3 psi.  There is a noticeable hesitation, and drop in rpms (almost like it wants to stall) that happens each time the fuel pressure drops like that.  There is a aftermarket fuel pressure regulator installed, that didnt help.  I installed a one-way fuel valve thinking that would help, it didnt.  I did a fuel pump check, there is a healthy stream of fuel into the bowls.  Ive also check the bowls after running the engine, and I didnt see any fuel vapors or leftover fuel lingering.  Could it possibly be the fuel pump, even though the it doesnt appear to be??  I'd like to avoid switching to an electric fuel pump if possible.  Any suggestions?

 

[Bully Bob]

The regulator is meant to prevent too much pressure.., not to keep it up.

Fuel starvation would eventually lead to the pump trying to pump air.

Tank, line or switch-over valve blockage...?

 

[B-Co Kid]

I replaced all of the the fuel lines from the pump forward, with stainless steel fuel line.  The tank is new.  Ive visually inspected the fuel lines from the pump back, and it looks to be intact and not collapsing. I am not sure what/where the switch-over valve is..

If all fuel lines, and switch-over valve, are ok, should I look to the pump??

 

[Bully Bob]

Switch over valve would be for dual tanks.

Pump could be the culprit.., if it wasn't already replaced recently.. 

What about "heat"..?   Heated lines can cause vapor loc.

 

[B-Co Kid]

I do have headers so heat could be the issue. I had issues with rising temp previously. Replaced hoses and thermostat, which didn't help. I did the electric fan upgrade and that solved the problem.

Also, I do have the heat spacer for the carb installed.

Not sure how to solve vapor lock in the hoses, other than completely rerouting. If that doesn't work I will try replacing the pump. Pump replacement looks complicated since there's not much space to work with.

 

[Bully Bob]

There's header wrap that helps send the heat out the exhaust.

Fuel lines shouldn't be near any type of exhaust.

No clue on the fuel pump.., however, it sounds like it's working fine.

W/O eyes on the situation..., I'm just guessing here,  for the most part. :-B

 

[Seabronc]

87 B-Co; 351w; mechanical fuel pump; fuel pressure regulator; fuel pressure gauge, edelbrock performer; c6 trans; no eec/computer;

Guys,

 Ive also check the bowls after running the engine, and I didnt see any fuel vapors or leftover fuel lingering. 

This indicates to me that the float valve is sticking or the floats are bad.  The bowls should never be empty.  As long as there is any pressure at all they should fill especially when the engine is ideling.  Fuel pressure looks pretty low and could indicate the pump is bad. you could go with a higher pressure fuel pump, but if you are not drg racing, that shouldn't be necessary.  So it could be a combination of fuel pump and float valve problems.  Like Bob said, the regulator should not be there.  In fact it could be causing the low pressure if it were defective.

>-

 

[B-Co Kid]

The fuel pressure drop has always been an issue, even before I installed the regulator. At one point, I had a problem with the pressure being too high and that is why I installed the regulator. Even when I had the problem of the pressure being too high, with no regulator, after driving around for a while, i would still have the fuel pressure drop symptoms.

Thanks for the input guys. I will probably try replacing the pump.