hi, I started to have an issue with my fuel pressure decreasing after a few minutes after startup. I've heard of fuel pressure creap due to too small of return line. I have the fast fuel injection, with a return fuel system. 1/2" aluminum lines run front to back. I have replaced the fuel pump twice and two different regulators. the same issue. checked the fuel filters and they are spotless. do I have too small of a fuel pump? electric efi, walbro type is installed now. thanks arlan
Too small of a return line should increase pressure... Too small pressure line would cause a pressure drop but AFAIK it's going to be a instantaneous problem, not something that develops after a few minutes... A engine uses more fuel cold, so if that were the case it should increase as engine warms... Assuming you have enough fuel supply for full power at WOT, the regulator just about has to be the problem... Are the regulators fixed pressure or adjustable??? How does the pump receive it's voltage??? Direct connection from battery/relay or is the pump powered from the ECM???
had a similar problem with my regulator. tried 3 and still had fluxuation. this is what I have for a return on my Atomic EFI...with no regulator...now. WIX 33737 Fuel Filter Will work with fuel injection without having to use a return line from the fuel rail to the tank. This filter has a built in regulator with return line. Simplifies fuel injection swaps & saves money.
it sounds like voltage drop to me. as the electrical components heat up from the high amperage draw of the big fuel pump, resistance will increase and drop voltage to the pump which will drop fuel flow and pressure. put a volt meter at the pump positive post and monitor it as the motor is running and compare the voltage to the fuel pressure.
im going to check the relay tomorrow. along with voltage at the relay after about 5 minutes of idling. its an adjustable regulator. I will also pull the gas cap and see if that helps.
