How steady are the fuel pressure readings when viewing a play back of a data log? I have a transducer installed and I see variations of 26 psi to 43 psi from one line of data to the next, whatever the rate of recording is, milli seconds? But this only happens occasionally, mostly I am seeing fuel readings from 30 to 40 under light load. This is with the regulator set to 45 psi with engine off.

 

The regulator responds to manifold vacuum, so compare the fuel pressure data to the manifold vacuum data. As manifold vacuum rises, fuel pressure will drop. You want a constant 43.5 psi pressure differential across the injector.

GD

 

My manifold vacuum readings are the same from one millisecond recording to the next, but I see at times a difference of 10 psi in fuel pressure. With the electric pump are there not pulses in pressure due to the nature of the design? I have a .032 restriction installed in the fitting to the transducer to try and limit these pulses. So on your installation you see no fluctuations in fuel pressure during playback of recorded data? Only smooth pressure changes related to manifold pressure?

 

I believe the original factory pumps did create pressure pulses as you are describing. They were roller-vane pumps I believe. There were damper chambers installed downstream of the pump to mitigate these pulses.

Many of us have had to change out the factory pumps and the new replacements are often (almost always) turbine style pumps. These don't exhibit this type of pulsation because instead of 4 or 5 roller vanes they have about 100 tiny turbine vanes resulting in very smooth delivery.

I don't have a transducer in my car. I've watched the fuel pressure plenty with my Snap-On mechanical gauge and I can't perceive any needle vibration, etc. But again - running a turbine pump as most modern cars and replacement third gen pumps usually are these days.

GD