help!!!! fuel pressure problem 71, 1.7 FI

[rolandz]

HELP VERY MUCH APPRECIATED.
I have a 71, 1.7 with original FI. the car starts fine but sometimes with pumping the pedal and turning the ignition on and off a few time to increase fuel pressure and once it starts it is ok for about 5 minutes or so. I take it for a spin even when cold and when rpm reaches 3000 or more it starts back firing and coughing as if it is not getting enough gas. To make a long story short I have placed an air pressure gage to check gas pressure (the only gage I have....better then nothing) and I have noticed that when the car starts acting up is when the gas pressure drops to almost zero. when it is high I have no problem. at hard start up....pressure is low then slowly as it builds up car runs better and better till it stabilizes, then after a few revs, pressure drops gradually till it reaches almost zero psi and motor cuts off.
what controls gas pressure in the lines? gas pump alone? do I have a bad gas pump or a bad gas regulator? or is it something else? I am removing the gas tank to make sure it is clean. but after that..what is my next step.
did anyone had that problem?

[JP Noonan]

Try pinching off the return hose after the fuel pressure regulator when you notice the pressure drop. If it increases pressure I'd say the regulator is shot, if it dosen't help then the pump may be dying. Watch the gauge, you don't want to pinch it off so much that fuel pressure spikes past 35+ psi. Above 35 or so you may repture a fuel line or blow off a hose clamp.

The problem with using a gauge not made for gas is the internal parts and seals may desinagrate from the fuel and then rupture spraying gas all over. Where safty goggles.

[Scottgib]

Had the same problem. It turned out to be scale in the gas tank that was clogging the screen covering the tank out line connector. If this is your problem, take the tank out, go to a radiator shop, have them clean and coat it.