My car spuddered a little on the way to the store, I came back outside from the store and it wouldn't start. I verified the relays all click when the ignition it turned on, I swapped them just in case is was only one clicking, I checked the fuses and you can actually hear the relays click off when you pull the fuse.
I then pulled the car home and replaced the Fuel pump. It wasn't a bad choice, it still would have needed it soon.

So I hot wired it through the Diagnostic plug and built the pressure up and then it started and ran perfectly until it ran out of gas again.
The fuel pump won't come on with all the correct elements working.

There has got to be something else that will stop the fuel pump from working. What am I missing. I have replaced or checked EVERYTHING I know of. I need someone smarter than me.

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86 Fiero 2M4 Silver, and 86 GT

Recently did some learning about fuel pump issues. The fuel pump gets power from 2 places,

1 from the ignition
2 from the oil pressure sensor

When the ignition is turned to the on position, the fuel system will pressurize itself, I can hear my fuel pump when it is somewhat quiet out. Should also keep a constant flow while the car is running, i don't know for sure, but I assume there may be a sensor which tells it this.

Also, there is a "backup" power supply from the oil pressure sensor when there is oil pressure. From my experiences, it is not as strong as the power from the ignition.

My thoughts would be that you are only getting power from the oil pressure sensor, which is not enough to maintain the pressure needed to properly feed the system. and as it slowly falls behind with the pressure is when it starts dying.

Based on what you've said above, the problem must be between the relay and the fuel pump connector where you hot wired it earlier. You obviously have power to the relay because its clicking, therefore the ign switch is also doing its job, and the fuse is obviously good, and the wiring betwen the connector and the pump is obviously good.

Id start peeling back the wire loom between the relay and pump connector and inspect all the wires...

Ok, update. I got the wiring diagram from another thread. I saw where the oil pressure sensor is in the middle. I know it's bad, it stays pegged.
I pulled the relays from my 84 so I have checked it with 5 relays now. All nothing. The 84' runs perfectly on them.
I pulled the relay and arched the blk/org wire to the tan one and the pump came on. So now I am seeing that the signal wire to the relay is actually not turning the relay on. What ever I am hearing click isn't the fuel relay.

So basically I am down to what ever signals the relay to come on.
Is there a way to jump the oil switch - is it connecting the two outer parts of the plug together? I'm gonna try that. Can't hurt.


Phonedawgs said- "The oil pressure sending unit/switch is a combo device that has a switch to supply power to the fuel pump AND has the gauge sending unit in the same housing. The two outside contacts of the connector are the switch portion The middle contact provides a variable resistance path to ground to control the oil pressure gauge.

The oil pressure switch is a redundant switch parallel with the ECM/Relay 'switch'. The fuel pump can be powered by either of these soruces. In a proper operating Fiero both would be 'on' during normal engine operation.

Usually when the sending unit of the oil pressure sender/switch goes bad the oil pressure gauge will peg full at a low oil pressure. (just like yours is doing)

Many replacement switch/sending units are miswired internally.

The oil pressure switch has no 'short to ground' function to kill the engine under low oil pressure situations.

IF someone's fiero's ECM/relay portion of the redundant fuel pump power circuit isn't working, AND the oil pressure drops below the switch's threshold, the switch will turn off and of course with the resulting lack of fuel pressure, the engine will die. The way this 'mystery' trouble is reported is the engine dies when oil pressure is lost, and can't be restarted till the engine cools down. After the engine cools down enough the oil thickens and after some cranking, the oil pressure switch will again turn on and restart the car. This isn't a design feature of GM's. The ECM/relay IS suppose to be working, and as a redundant supply line for fuel pump power, would prevent the stalling that occurs.

The pin you should be checking on the ALDL isn't pin B but pin G - The previous poster was talking about jumpering from pin D(he said E) to pin B - ON THE RELAY SOCKET, not the ALDL.

On the relay socket you should always have power on pin D. When the relay is energized by the ECM the relay connects that power from pin D (Orange Black) to pin B (Tan White) and thus sends power to the fuel pump. You could insert a wire from pin D to pin B to bypass the relay as a test to see if it makes the fuel pump run.

Note this drawing is orientated 180 deg from the previous picture. Use the center plastic lug to figure out how your's is orientated. The two side plastic lugs are deceptively drawn on this picture which could make you think it is upside down from what your's is like. Again use the CENTER lug to determine your orientation. Study it and you will understand what I mean"

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86 Fiero 2M4 Silver, and 86 GT

[This message has been edited by jwrape (edited 06-22-2011).]

quote Originally posted by jwrape: Is there a way to jump the oil switch - is it connecting the two outer parts of the plug together? I'm gonna try that. Can't hurt.

If you do connect the two outer wires of the oil pressure sender together, the pump should start, but it will run continuously even with the key out of the ignition.

A common problem which causes your symptoms is a broken ground G504. With everything hooked up normally, turn the igition to RUN (engine stopped). Then scrape a little insulation off the black wire coming from the fuel pump relay. Using a spare wire, touch one end to the scraped off bare black wire, and the other to a known good ground like your top strut tower nuts. If the fuel pump turns on for two seconds and shuts off, then the problem is that the black wire from the relay isn't making contact to ground, probably because G504 is broken. G504 is a huge eyelet with two wires attached to a transmission bellhousing stud. Don't forget to tape up the insulation you scraped off.

OH WOW! Do I feel stupid. It was a quart low on oil.
After replacing the fuel pump and pulling my hair out, it was low on oil.

This 25 year old car is smarter than me.
I never had a car that would cut off for just a quart.

Sorry for the mis-alarm

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86 Fiero 2M4 Silver, and 86 GT

So it sounds like your fuel pump is only getting power via the oil pressure switch, not the relay.

You don't hear the fuel pump run for the first two seconds that you turn the key on I am guessing. But you said you hear the relay clicking, and maybe clicking off after the two seconds are finished.

The fuel pump relay has the following colors of wires

Orange/Black
Tan/White
Green or Green/White
Black or Black/White

The Green/White is the wire the relay gets it's power on. The Black is the ground. So if you hear the relay clicking on, and then off in two seconds those two are working. The Orange/Black is always on power from the fuse box. The Tan/White goes to the pump.

If your relay is clicking but the fuel pump isn't coming on, try swapping the relays and see if that fixes it. If it does buy a new relay for the AC or that will have stopped working.

You can also try to insert a wire between the Orange/Black and the Tan/White and the fuel pump should come on.

Many times what happens is the relays are left off of their hangers and the connectors and the relays fill with water and go bad. If your relay connector is all corroded it should be replaced.

Having the relay working will make the car start up MUCH faster especially when the engine (oil) is warm.

quote Originally posted by phonedawgz: So it sounds like your fuel pump is only getting power via the oil pressure switch, not the relay. You don't hear the fuel pump run for the first two seconds that you turn the key on I am guessing. But you said you hear the relay clicking, and maybe clicking off after the two seconds are finished. The fuel pump relay has the following colors of wires Orange/Black Tan/White Green or Green/White Black or Black/White The Green/White is the wire the relay gets it's power on. The Black is the ground. So if you hear the relay clicking on, and then off in two seconds those two are working. The Orange/Black is always on power from the fuse box. The Tan/White goes to the pump. If your relay is clicking but the fuel pump isn't coming on, try swapping the relays and see if that fixes it. If it does buy a new relay for the AC or that will have stopped working. You can also try to insert a wire between the Orange/Black and the Tan/White and the fuel pump should come on. Many times what happens is the relays are left off of their hangers and the connectors and the relays fill with water and go bad. If your relay connector is all corroded it should be replaced. Having the relay working will make the car start up MUCH faster especially when the engine (oil) is warm.

I actually did all that. Connected the Org/blk to the tan and it clicked on. I swapped out 5 relays and none of them worked until I put another quart of oil in it and then it worked. 3 relays came out of my 86' 2m4.

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86 Fiero 2M4 Silver, and 86 GT