Fuel pressure

[Pomorza]

Hey guys

For the past couple of months I've had a problem with the car idling very poorly when warm after restarting. Upon investigation I found that leaky injectors could be the culprit. This afternoon I installed an inline fuel pressure gauge right past the fuel filter (see pic). I got everything nice and tight and started the car. To my dismay the gauge read 30. When I revved it it goes up to about 33 or so but when I release the throttle it drops to ~27 and then goes back up to 30. When the car is off the pressure will drop to 25 and then slowly creep back up to 35.

I understand that this readings isn't exactly what the injectors are seeing but unless there is an increase of 5psi from the gauge to the injectors there seems to be a problem to me. Any ideas? Pump, regulator?

Jan

Edited February 27, 2010 by Pomorza

[Zed Head]

The fuel pressure regulator (FPR) has a vacuum line attached to regulate fuel pressure according to manifold vacuum. Yours looks like it is probably working correctly.

If you want to check the FPR, you can pull the small wire from the starter (it comes off by hand, no tools needed), then turn the key to Start to run the fuel pump. The fuel pump will run (you'll hear it), but the engine will not turn over. Without the vacuum from the motor, the FPR will give a higher pressure. 36.5 psi is normal for 1976 and most years, I believe.

A lot of people have the problem with rough idle after starting a warm engine. I have seen one proposal for vapor lock but no followup. Have not seen a good remedy yet.