scorpion sensor

[montecarlo]

??? fuel pump question again
have fitted another fuel pump but still no fuel is getting through the pump on my scorpion i seem to have a sensor on the gearbox two actually when looking into the engine bay from the back the first sensor has no wires connected to it and no visible wires or wires cut off i am wondering if this is the sensor that cuts the fuel pump off and is the reason why my car will not start if any one knows what wires go on this sensor would be gratefull if someone could let me know the coulors and or location they go to as there seems to be no place for the wires to go

[DJ]

I'm assuming that when you say "another pump" that you either mean a new pump or a known good one from a running engine.

Those switches on top of the gear box have nothing to do with the fuel pump. They are emissions-related. The fuel pump cutoff is operated off the oil pressure sensor. The purpose is to prevent the fuel pump from running if the engine is not, as in an accident. The idea is to keep from pumping fuel out onto the engine in an accident.

If the oil pressure sensor is bad, it's likely keeping the fuel pump from running. Have you replaced it yet? If not, you might as well because it's probably leaking past the diaphragm and going to fail soon anyway. This is VERY common.

Do you have any voltage going to the pump? Have you tried hooking the pump to a direct circuit? At least for testing, hook it to the hot side of the coil. That way it will be switched, you will know you have voltage to the pump, and youcan control it with the ignition switch.

If you:

1. have known voltage to the pump, and

2. the pump is running, and

3. you still have no fuel...

you have to have a blockage in your fuel line.

If you have known voltage to the pump and the pump doesn't run, there is something wrong with the pump.

[montecarlo]

???hi there
thanks for the reply it seems that looking on the circuit diagram on your site the two wires joined together are ment to be on the sensor so i will try to find where the sensor is the wire lengh puts the sensor somewhere around the carb so i am guessing that having it not connected the pump will not work anyway . i have a new one from the monte hospital to fit and maybe just maybe it will go
thanks

[DJ]

Well, as I said, the "sensor" is the oil pressure sender which is located below the carb next to the oil filter. There is NO other special sensor that controls the fuel pump so I suggest you just perform the simple troubleshooting previously suggested.

You didn't answer any of my questions. Do you have known voltage to the pump? Have you tried hooking the pump up to a direct voltage source to make sure it works?

If you put direct voltage to the pump (I suggest from the + side of the coil) and it doesn't work, the PUMP IS BAD.

If the pump works with a direct connection but doesn't work with the normal connection, REPLACE THE OIL PRESSURE SENDER.

If the pump works with a direct connection but doesn't pump any fuel, YOU HAVE A BLOCKAGE IN THE FUEL LINE.

This should be REALLY simple to troubleshoot. Does the engine start when you put fuel directly into the carb?

[ecohen2]

Correct me if I am wrong, but doesn't this sensor also send the signal for the pressure gauge on the dash?

[DJ]

That's correct.

[montecarlo]

;D hi there all is now working on the scorpion i used the wiring diagram on this sit and it now is working fuel is getting to the carbs finnally found the sensor hidden away so it now starts so i am well on the way to getting the car back on the road
thanks

[DJ]

Excellent!!!

[Will]

With all due respect to DJ, I believe the fuel pump relays are powered by the oil pressure SWITCH, not the oil pressure SENDER (completely different device).

The trick solution IMO is to use the Holley oil pressure safety switch (SPDT pressure switch) which completely eliminates the clusterhump of wiring and two craptastic relays located behind the bracket/ plate that is over the right rear wheel well (and also holds the coil on many 76
's, not all)

The Holley switch is under $20. It requires 1/8" NPT, but that's easy enough to make by tapping out a metric plug.

[DJ]

Hey, Will

I'm sure you know better than me about the specifics of the wiring. I just tend to call both of them "sensors" or "senders" because that essentially what they do, right? They "sense" the pressure and "send" a signal. One "sends" to the gauge and one "sends" to the dash light if I'm remembering the spagetti correctly.

Anyway, just to be clear to everyone here, Will can certainly provide better specific details than I can. He's studied the diagrams in much better detail than I have and has a better memory for such things. I was hoping he'd jump in here to help but it sounds like the trouble has been rectified anyway.

[Will]

DJ *almost* had it right, and doubtless has more to worry about at this juncture than I do- the important differentiation in the two devices is that the SENDER (canister shaped device) is failure prone and $40 to replace (just like DJ said, it has a diaphragm that gets oil on the "dry" side).

However, the SWITCH (small device) is a $15 item and I have yet to see one go bad (In my limited experience). The switch goes to the fuel pump relay mess.

Even iif yours works fine *at the monment* , bear in mind the Holley part for an upgrade to the OEM system.