EFI fuel losing fuel pressure.

DaveEFI · Post by **DaveEFI** » Thu Jan 20, 2011 9:36 am

For some time now, my SD1 EFI hasn't maintained any pressure in the fuel rail after the pump stops. It drops to zero in seconds according to my gauge.

There are no signs of leaks anywhere in the pipework.

The tank was repaired after a leak and has a lifetime warranty.

The pump is new - bought from Ebay and slightly different from the Bosch one. Can't remember the make - it has a blue plastic case.

The regulator is a Malpasi (sp?) non rising rate adjustable.

Last year I removed the injectors and reassembled them to the fuel rail outside the engine, and saw no leaks from them.

The same fault was present with the original Bosch pump and FSE regulator. And before I fitted the MS and EDIS.

The MegaSquirt runs the pump for a few seconds at switch on - but this isn't long enough to achieve full pressure. When I made up the loom for the MS I modified the MS circuit so the pump runs when you operate the starter - as per original Rover flapper. Operating the starter switch with the car in drive runs the pump. Do this for about 15 secs then slip in into neutral, the starter operates and the car starts promptly. If you try and start it in the normal way, it churns and churns before starting.

SuperV8 · Post by **SuperV8** » Thu Jan 20, 2011 12:38 pm

My MS also primes the fuel pump on start up and you can hear the sound of the pump change in litteraly 1-2seconds showing its upto pressure. Also have a gauge plumbed into the fuel rail and that reads a high pressure for ages after fuel pump turn off, drops initialy a couple PSI i guess due to the pressure reg closing.

Are you 100% sure the feed and return are correct? Don't know if it would run if they weren't?
The feed from the pump should go to the open end of the fuel rail and the regulator on the other end of the fuel rail, then the return from the reg to the tank.

I would also check the pressure reg is plumbed in the right direction, should be able to hold 30 odd psi.

Tom.

spend · Post by **spend** » Thu Jan 20, 2011 12:48 pm

Failed/missing non-return valve on the fuel pump or more likely a leaky injector (failing to seat & seal)? If all the pipes are ok and not leaking...