Engine Oil Pressure Switch/Fuel Pump Wiring Question - Mystery Wires?

[Justa6MB]

Hello, I realized my fuel pump is running all the time and it shouldn't be. So I also realized I have some mystery wires that were cut and taped up in the engine harness by the drivers side valve cover. About 16 years ago I installed a oil pressure guage and removed the factory switch. Could one or more of these mystery wires be causing my fuel pump to run constantly? I purchased a backup CD manual but I can't seem to figure this out. I have checked the hotwire relay and original fuel pump relay and they are working. It seems that the fuel pump trigger wire from the ECM is powering up the relay. Can you please help me with this problem and perhaps identify these wires?

 

[williamsGN]

http://turbobuick.com/forums/threads/fuel-pump-stays-on.326318/#post-2568197

 

[fastblackracing]

I prefer my fuel pump to run with the ignition on, it makes fuel pressure adjustments easier as you can do it key on engine off. just my prefernce.

 

[johnl455]

Except in a crash, street or track, the pump could stay on feeding fuel on a fire being the end of you and the car. Computer is supposed to open FP relay with no crank pulse counts or no oil pressure. That stuff was there for a reason.

 

[Justa6MB]

Ok so yes I have no idiot light, I would have cut the wires going to and from the sensor which will be the pink/black and the grey. But by the looks at the diagram the switch was open until oil pressure comes on. So in theory should the fuel pump not come on after the initial 2 second pulse? The oil pressure gauge is a VDO gauge bought from Jay Frick in like 97 or 98. Would there have been instructions telling me to somehow short something out to cause the pump to run all the time? I don't remember doing anything but it was a long time ago, and I doubt I would've just jumped something on my own. I'd like it to shut off.

 

[Justa6MB]

Well I think I found out that a couple more of those wires likely went to the canister purge - which has been removed. So they are:
Pink/Black = Oil psi switch
Grey = Oil psi switch
Pink/Black = Canister purge
Dark Green = Canister purge
Purple/White = Waste-gate solenoid
But still looking for answers as to why the fuel pump is running all the time. Again, shouldn't the fact that the wires that went to the sensor are open be ok?

 

[tonka]

Does the pump shut off when the key is off, or run all the time? If you pull the FP/INJ fuse does the pump stop running? If you unplug the stock fuel pump relay on drive fender does the pump stop?

 

[Justa6MB]

Thanks for the reply. The pump only runs when the key is on. The pump shuts off when I pull the fues on the fuel pump hot wire kit. The pump also shuts off when I pull the factory fuel pump relay. It appears that the fuel pump relay trigger wire (I think it is green) has power when the key is on and does not shut off after 2 seconds. If that side of the factory oil psi switch was normally closed then opened when oil pressure could that explain it? So if I hooked the pink/black wire up to the grey wire and turned the key on - and the fuel pump runs for 2 seconds and stops - that should mean I need to "T" a factory oil pressure switch back in. Because the fuel pump wouldn't come back on after the engine starts. Make sense?

 

[tonka]

If disconnecting the factory relay kills the pump, the wiring for the oil pressure switch is not the issue. You need to grab your meter or test light and actually check for the presence of a constant 12 volts on that dark green/white wire, appearances and assumptions will lead you on wild goose chases more often than not. If, after checking, you do not have a constant 12 volts on this wire, your factory relay is probably stuck/welded shut. If there is a constant 12 volts there, try checking again after disconnecting the "A" connector at the ECM. If it is still there, you need to sort out your wiring. If the 12 volts disappears after disconnecting the "A" connector, that would point to a bad ECM.

 

[Justa6MB]

Well I checked the relay and confirmed there was constant power on the green wire with the key on all the time. So I then disconnected the “A” connector from the ECM and the power went away on the green wire at the relay. So that points to the ECM. I don’t suppose it could have been programmed into the chip? It is a Turbotweak chip?

 

[Drewster]

Under your hand in the pic there should be 2 wires not connected to anything. They are the factory fuel pump prime connector and a tach output connector. Possibility you have connected a keyed power source to the pump prime connector. I don't know the wire color off hand. I can check it later.
I use this connector to pump out race gas when connected to the battery. The pump will run continuous anytime power is on it.
Andrew

 

[Drewster]

I should have read all the prior posts. The pump prime connector will bypass the relay and will make no difference when relay changes state or is unplugged.
I'll have to look at the drawing to see what wires associated with the oil switch can do this.

 

[RmvBfrFlght]

Well I checked the relay and confirmed there was constant power on the green wire with the key on all the time. So I then disconnected the “A” connector from the ECM and the power went away on the green wire at the relay. So that points to the ECM. I don’t suppose it could have been programmed into the chip? It is a Turbotweak chip?

Best to pop pin/terminal A1 out of the ECM harness connector. That is the FP relay feed. If it then stops the fuel pump, the ECM is bad, BUT, don't toss it...

There is a small transistor that provides power to the fuel pump relay (nothing to do with the chip). These transistors fail often, usually open, but from time to time they fail closed. Can replace it with a PN2907, takes a few minutes to open the case and fold back the top board to get to it.

If you or someone you know is handy with a soldering iron I can post a pic of which transistor it is. Or, for now don't worry about it, or get another ECM if you do.

But don't toss the current one, easy to fix, even if down the road.

RemoveBeforeFlight.

 

[Justa6MB]

Well thanks guys, I'll probably live with it for now. Is there any problem with it other than perhaps losing a few amps on the starter? If I ever have to do anything with the key on I just pull the hot wire pump fuse anyway. But is there any other reason?

 

[tonka]

As Johnl455 pointed out, if your ever unlucky enough to be in an accident on the street or track that ruptures the fuel line, could be a very bad outcome for you and yours.

 

[Justa6MB]

Yeah that's a good point. I suppose I should pick up an ECM for that reason alone.

 

[Justa6MB]

Oh I suppose I'd also need to reinstall the factory oil pressure switch too.

 

[RmvBfrFlght]

Oh I suppose I'd also need to reinstall the factory oil pressure switch too.

You don't have too, it is just a backup for the fuel pump relay. Which is likely why GM got away with that dinky transistor operating the relay.

RemoveBeforeFlight

 

[Justa6MB]

Oh right, the signal to the ECM is from the crank sensor right? So I haven't looked yet - but where's the best place to get a ECM?

 

[Drewster]

the fuel pump drawing can be found at
http://www.vortexbuicks-etc.com/fuel_pump.htm
Andrew
ps i think there are some ECMs for sale in the "parts for sale" section.