MSefi.com read only forum (Jan.15,2018)

When my MSII first powers up the fuel pump primes the system and the fuel pressure goes immediately up to 43 psi. After the fuel pump stops the pressure drops back down to ~0. I don't have any leaks in the line, I pressurized the system up to 70 psi with no leaks anywhere for 4 or 5 minutes. Shouldn't the pressure stay at approx. 43 while cranking? I'm not expecting the pump to run, but, doesn't the system need to be pressurized to send fuel into the injectors?
thoughts?
I should mention that I am still troubleshooting and have not started the engine yet.

thanks,
Rod H

If your fuel pump outlet does not have a check valve or the check valve is bad, the sytem will not maintain pressure. With my Bosch pump which has a check valve in the discharge fitting, my pressure is maintained with a gradual decay to zero after about 3 hours or so. The fuel pump should run again during cranking once MS detects tach pulses.

-Dennis

this is normal, i use Walbro 255, when you prime, fuel pump loads up fuel into lines and that builds pressure within 2-3 sec in for cranking, but than it stops and pressure will lower in time as fuel pump stops to work, in my car form 51psi to 0psi goes within about 3 min if i won't start an engine. but when you start to crank and then run engine fuel press will be build again and kept, just remember that pressure on running engine is being compensated by vacume connected from intake manifold to fuel pressure regulator. so if you'r worried about pressure just start engine just after primeing and your problem is "solved"
so don't worry every is fine from whot you wrote

best regards

Depends on how quickly the fuel pressure drops off - it's possible your regulator may be leaking.

I have two regulators that are new; one is a holley the other ebay no-name, same result which ever is installed. The fuel is not exiting through the regulator side of the line.

The pressure goes down quickly, so I'm guessing their is no check valve or it is not working in the fuel pump.

Thanks guys,
Rod

what do you mean by quick ?? how does it takes from 41 to 0psi

best regards

2-5 seconds. I'm going to add a check valve inline and seeif this solves the situation. It appears that either there is no check valve in the fuel pump or it is not working.

Thanks for the help,
Rod

so it is a bit to fast it should take abour20 sec. to drop down to 0

best regards