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

i have a walbro 255 lph inline fuel pump and a universal (autoteq) fuel pressure regulator (the kind you see on ebay). when ms primes the pump, the pressure goes up, but as soon as it stops, pressure drops back to 0 immediately. if there something wrong with my fuel pressure regulator? fuel pump? basically, when i talk to other people, it shouldn't drop down that fast and should hold some pressure. i don't have any leaks (that i can tell).

anybody else have this same thing happen to them and is it normal?

i don't think it should bother any thing as long as your pump is mounted low so it stays primed i have an aeromotive a-1000 pump and a expensive mallory regulator and it drops down too and they are brand new doesn't cause any cranking issues as the pump hits forty pounds as soon as power is applied if it does cause you problems there's a priming pulse delay under other fuel settings in megatune that might help can't say for sure as i don't have any issues but if you do you could try it zane

Sure sounds like a bad regulator to me - the only other thing that'll do this is a leaky injector. I could not get my own project car running with a bad regulator and had to replace it. In my case, the faulty regulator had come off a junkyard car - I was trying to cheap out and use a Datsun 280ZX regulator.

could be you have a bad check valve or a pump that requires an external check valve, only way I know to check if it the regulator or pump, is to put a shutoff valve after the pump, pressurise the system then shut off the valve & see which side looses pressure first...

One issue that can come up is that the prime pulse occurs with no pressure, and no fuel is injected.

Priming pulse isnt designed to inject fuel, its designed to purge air from the system?

My dad's Walbro pump does this also. It does take a little longer to start since the system has to build pressure first.

thanks for all the replies. it seems like everyone's setup acts a little differently depending on what you have installed.

i ended up changing the following on my fuel setup:

- changed the fuel pressure regulator from an ebay special to the MSD-2222 (vacuum boost sensitive. basically re branded bosch unit) from amazon. it had the 5/16" barb connections i needed. works even on n/a cars (mine is) but in the event i go turbo, it's all set already.

- changed the fuel injectors from stock junkyard 19lbs and bought new delphi 30 lbs high impedance injectors from DIYAutoTune.

after i did the above, my fuel pressure held a lot better and does not go to 0 psi immediately after the power is off. so in my case, it could've been either leaky injectors of the pressure regulators. since i changed out both at the same time, i'll never know.

i found out about the msd fuel pressure regulator from these guys. then even have an extremely good write up on installation and setup of the regulator among other things.
http://www.bitzracing.com/docs/index.html