fuel pump/relay issue's not rewired

[Quadsportz]

My dsm's fuel pump will kick on twice in 5 mins when I turn my car off. I would think that it shouldn't turn on because the car is off. The pump is not rewired as I can tell,I don't see a line going from the battery to the pump. Also when my car idles I can hear the pump cycle on and off. Shouldn't the pump be always running when the car is started? My 97 gst has a 95 head so it has a 95 cas. I have the firing order swapped for the car to run with the inverted cas. Could this affect this because the cas send signals to turn the pump on. I'm having problems with fuel cut with the t25 at 16lbs and I only have a small boost leak at the intake manifold were they used the same gasket doing the head swap. Could this be because off the pump not running all the time when the car is started? Could the relay be causing the fuel pump to kick on twice when the car is off,and make is cycle on and off when idling.

 

[Quadsportz]

Anyone? Someone has to know about this!!

 

[Paul@RTM]

You're right that the fuel pump should not turn on without at least ignition power, so something is wrong there. CAS has nothing to do with the pump (well, unless some goofy wiring is causing the weird things to happen to the pump's power/ground). The pump is only ever on or off, it never "slows down" or "speeds up" or "pumps less" or "pumps more" in response to anything. The CAS "signal" doesn't tell the pump to turn on. The ECU tells it to turn on at some point, then never concerns itself with the pump again. I don't think it even ever tells it to turn off, I believe power is simply lost with ignition power.

 

[miguelmcv]

Check voltage at the pump connector when the car is running, if the power is constant, then you know your electrical is good, but if power is intermittent, then you have to check the wiring or in this case could be your fuel pump relay.

 

[Quadsportz]

My car has a 95/96 cas so there is a custom wire extension going from passenger side of engine to the driver side because the car has the cas behind the timing gear maybe this causing it? car came like this when I bought it. When idling the pump doesn't speed up or anything. It's like it turns on when the fuel pressure gets low. Would the relay even be able to turn the pump on with the car off? It kicks on more often with the car off when its hot outside. It will only do it twice or so within 5-10 minutes of me shutting the car off. I've never heard it turning on hour's after It's been shut off. Is the fuel pump relay the mfi?

 

[Quadsportz]

Is it possible that with my mods I already maxed out my injectors with the t25?

 

[vicore]

the car has the cas behind the timing gear

MFI relais, MPI relais, sensor relais - all the same small golden box with 9 pins

Two relais in that box: one for energy supply of the sensors, ecu etc and one for the fuel pump.

 

[Quadsportz]

am I maxing out my injectors with my modifications?

 

[steve]

You're right that the fuel pump should not turn on without at least ignition power, so something is wrong there.

The pump is only ever on or off, it never "slows down" or "speeds up" or "pumps less" or "pumps more" in response to anything.

These two are correct. The fuel pump is powered from the ignition circuit and DSM's don't come with any fuel pump resistor or PWM for the pump power to reduce the output under low loads. That's why a good fuel pressure regulator is required to maintain the base fuel pressure with bigger pumps.

CAS has nothing to do with the pump (well, unless some goofy wiring is causing the weird things to happen to the pump's power/ground).

The CAS "signal" doesn't tell the pump to turn on. The ECU tells it to turn on at some point, then never concerns itself with the pump again. I don't think it even ever tells it to turn off, I believe power is simply lost with ignition power.

While your correct that the CAS isn't directly power the pump, the CAS signal is used by the ECU to know when the engine it rotating. The ECU is always looking at the CAS and if it doesn't see a pulse in 2 seconds it turns the fuel pump off, otherwise if it does see a CAS pulse, it turns the pump on. (and if the pump is already on it doesn't hurt to keep turning it on.) This is a safety feature so you don't burn up in your car after a crash.

 

[steve]

I'm having problems with fuel cut with the t25 at 16lbs and I only have a small boost leak at the intake manifold were they used the same gasket doing the head swap.

Fix all boost leaks. They cause fuel cut.

 

[Turboturd]

am I maxing out my injectors with my modifications?

I doubt you are maxing the injectors out at this point.

Concerning your idea that the pump is turning on and off at idle, this isn't really possible, or the car would die. If you are hearing the pump, and the noise level varies at idle, it can be normal. I heard it all the time with my walbro when it was warming up, just like its cycling, which I think is caused by inconsistent voltage. When I rewired the pump it went away and just made a constant buzz.

 

[Paul@RTM]

The ECU is always looking at the CAS and if it doesn't see a pulse in 2 seconds it turns the fuel pump off otherwise then it does see a CAS pulse it turns the pump on. (and if the pump is on it doesn't hurt to keep turning it on.) This is a safety feature so you don't burn up in your car.

I didn't know that. I guess that makes sense. Thanks.