Fuel pump pumps and pumps and pumps!

[loxley]

Hi all,

When i switch my ignition on the fuel pump kicks in but never stops pumping, is this normal?? surely it should build pressure and then stop!

Thanks in advance...

[keith]

is there fuel in the tank? - what car is it?

[loxley]

it's a 94 spi, yep lots of juice in there...

[mgb1978]

Doesn't the SPi have a return pipe to the tank ? So the pump runs constantly and all unused fuel is returned to the tank.
To be honest Carbs are more my thing.

[woody]

Pump runs all the time pushing fuel through the regulator

[keith]

on my SPi when you turn on the ignition, without starting the engine, the pump runs for a few seconds then stops. presumably once the fuel pressure exceeds a value the thing switches off?
i've not seen wiring from regulator to fuel pump relay so perhaps that happens internally in the pump? I haven't taken an SPi fuel pump apart either so cant tell.

[woody]

I run an MPi pump on my turbo feeding a fuel regulator ,for safety the pump is controled by the oil pressure switch but the SPi has no connection between the oil pressure switch and the ecu. Unless it just times out from the ecu if the starter is not engagued.

[keith]

I run an MPi pump on my turbo feeding a fuel regulator ,for safety the pump is controled by the oil pressure switch

brilliant!

- Unless it just times out from the ecu if the starter is not engagued.

yea, must be that.
Loxley, has this just started happening or are you just wondering?

[loxley]

Thanks to all for the replies, I havn't had the Spi for that long, but the pump always ran, I have done alot of work on the car and have only recently started driving the car regularly, the engine idles perfectly however under hard acceleration the engine seems fuel starved and hesitates slightly, I have checked and replaced the vacuum hoses.... I called into a mate with a Spi today and when his ignition is switched on the pump runs, builds pressure and then stops...... I swapped the pump from my Mpi into the Spi and it does the exact same, ie. runs constantly... hmmmmm ideas/suggestions welcomed!

[keith]

as long as the fuel pressure is within specification then it shouldn't really matter.
*but* (reading on!) if your MPi pump mimics the SPi pump when fitted to the SPi, then the "problem" is with the car, not the pump. As Woody mentioned, perhaps theres a relay sticking *on* - the relay pack in these cars can be troublesome.

[woody]

Just took apart a spare SPi injector I have , the regulotor is spring based so once the pump is running all excess fuel returns to tank, no pressure switches anywhere.The wiring diagram shows no start signal to the ECU.

[kona]

I think Spi is designed to run at 1 Bar, Mpi runs at 3 Bar. So I think you may have a issue there if your using a higher pressure, it would cause overfuelling as the injector will flow more fuel at a higher pressure.

If the fuel pump is staying on, you may have a Issue with the fuel pump relay, I remember reading this relay box in Spi is notorious for giving trouble.

[daniel garry]

is there a chance some1 has wired the pump to a live feed from the ignition?? i know my cut off switch went kaput so i bypassed that, maybe some1 had a problem with the relay or switch and just bodged it??