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Hi there,
I bought a project car, with a swapped-in 350 and manual trans. It has a EBL engine computer, and it is not turning on the fuel pump at startup. Once the engine cranks enough to see oil pressure, then the pump comes on. So that circuit works. But when I tried looking for the fuel pump test socket, I can't find it. I looked at the ALDL socket for the wire in outlet G, and there is no wire there. Looks like it never had one. I tried unplugging the FP relay in the pic, and plugging in a test probe, but none of the wires turned on the fuel pump.
I think the actual wire that goes to fuel pump (+12V) is the TAN/WHT wire. At least it is inside the interior of the car. Not sure if it changes color in engine bay across the C100 connector. GM wiring schematics will tell you all the wire colors so you can identify which is which.
I think the actual wire that goes to fuel pump (+12V) is the TAN/WHT wire. At least it is inside the interior of the car. Not sure if it changes color in engine bay across the C100 connector. GM wiring schematics will tell you all the wire colors so you can identify which is which.
Thanks for the reply. Can you tell me how to test the relay to turn on the pump? I tried connecting the power from the battery to the tan wire in the pic, but it did not turn on the pump. Am I doing it wrong?
The wires for the relay field coil (controls the relay on/off) are,
GRN/WHT (+12V switched control on high side of field coil)
BLK/WHT (ground path on low side of field coil)
The wires for the fuel pump are,
ORG (+12V constant from a 20A inline fuse in engine bay)
TAN/WHT (switched +12V to fuel pump)
Putting +12V on the TAN/WHT wire completely bypasses the relay and the pump should turn on. The TAN/WHT wire might also be powering the MAF sensor and burn-off relay too if it's a V8 multi-port injection car.
I tried putting power to the ctan/white wire, but I got nothing. The previous owner said he put together two harnesses to make one work. I looks like a speed-density setup, because there is no MAF sensor, just a MAP sensor. Could it be the MAF wiring was cut, and therefore the FP relay gets no power now?
In that case you probably want to trace the wires to see if there is a lack of continuity somewhere. No need for power to do that test. You can do it by checking electrical resistance with a multimeter.
The TAN/WHT wire passes through the C100 connector into the interior, then runs under the driver side sill cover to the C313 connector between the rear seats. Once outside the car it changes to just a TAN color and routes to the top of the fuel tank to the pump.
The fuel pump ground comes out of the fuel tank as a BLK color, goes to the C313 connector again behind rear seat, passes into the interior of the car and has a ring terminal connector to the G304 ground location inside the car. I'm not sure, but I think that's under the front seat where the little wire for the seat belt latch grounds.
Getting to the C100 connector is a pain in the ****. I would skip that at first and get under the car and unplug the C313 connector. There's lots of room to work with the rear wheels on ramps -- super easy connector to access. Probe the connector thru firewall for continuity of the TAN/WHT wire all the way back to the relay. And then probe continuity of ground wire to chassis. Follow the problem if you find one.
But if that looks good then probe the harness side of the connector at the fuel tank by checking resistance between the TAN and BLK wires. You're going to get some resistance because it's measuring the pump coils too. I don't know what is the right number but I can probably guess whether it sounds about right when you report back (just based on how motors work).
I have an idea to power the fuel pump prior to starting: what if I wire in power to the tan wire for the fuel pump, with a momentary push-button switch? The PO tried to do this, but he wired the switch in to the wrong relay! LOL. Will it work if I use a tap-in Tee connector to power the FP?
Figure out what's wrong and fix it. The car used to work, you don't need to redesign it.
Just think about how much you must hate the previous owner by now with all the custom wiring he did to "improve" things... Yeah, don't be like that guy.
To properly fix this wiring, I would have to take out the engine and rip out all the wiring. I am not going to do that. At this point, it is not necessary to fix this fuel pump issue, the car does start after the oil pressure comes up. It would be a "nice to have". I would just prefer to have the car start immediately, without having to crank the engine so long. So if I can work around this problem, the car will be closer to being a daily driver.
There is absolutely NO NEED to remove the Engine or Transmission to access of remove the Stock Wiring Harnesses!
You also do not need to remove the Wiring Harnesses.
But if you ever did need to... there are 2 large Harnesses.
One is on the Driver-Side and ends at the Fire-Wall Bulkhead Electrical Connector (C100 Connector, below the Relays in your Image).
The other is on the Passenger-Side and ends at the passage in the passenger-side Fender, where it meets the Fire-Wall.
Is the Car/ does the Car have 1988 Camaro Wiring Harnesses?
Different Model Years, and Engine Packages have slightly different Wiring Configurations in regard to Connectors used/ Terminal locations...
But the Circuits involved more or less are very similar.
The Fuel Pump Relay uses the following connections:
-18AWG Black with a White Tracer Wire that is always connected to a Chassis Ground.
-18AWG Green with White Tracer Wire that is switched to 12V Positive by a connection to the PCM. (Turns Fuel Pump ON/ OFF).
-12AWG Red Wire that is NOT Connected. With the Ignition Off, the Red Wire can Turn the Fuel Pump ON when connected to 12V Positive.
-12AWG Tan with White Tracer Wire that is always connected to the Fuel Pump.
-12AWG Orange Wire that is switched to Fused 12V Positive by the Relay
(Powers Fuel Pump when PCM switches the 18AWG Green with White Tracer Wire to 12V Positive).
A cheap $10 Multi-Meter from Harbor-Freight will allow you to perform Continuity Testing at the Relay Connector.
QwkTrip gave you perfect advice.
If you do not know what to do, please just tell us, and ask.
If you have a Meter in hand we can quickly test the Wires at the Relay Connector...
Or just a Test-Light if that is easier for you.
Unplug the Relay Connector.
Connect the Test-Light to the Battery Positive, Touch the Probe to the Terminal for the Black and White Wire.
Light turns ON = Good, NO Light = Not Good.
Turn the Ignition Switch ON.
Connect the Test-Light to the Battery Negative, Touch the Probe to the Terminal for the Orange Wire.
Light turns ON = Good, NO Light = Not Good.
No Test done for the Red Wire.
The Tan and White Wire will require you to unplug the Fuel Tank Connector under the Car, above the Rear Differential.
The 3-Wire Connector is basically behind the Back Seats, but under the Car.
The Image below shows the Stock Connector and a second Connector to the left that is NOT Original.
Your car should ONLY have the One Connector.
Unplug the Connector and Probe the Terminal for the Tan Wire.
You can use the OHM/ Resistance setting on the Multi-Meter, if you have one.
You will need a long wire to use as an extension for the Meter Probes.
If you have No Meter, reply here and I will give you different instructions.
The Green and White Wire will probably require you to cycle the Ignition On and Off several times before the PCM will supply 12V Positive to the Wire.
Connect the Test-Light to the Battery Negative, Touch the Probe to the Terminal for the Green and White Wire.
Light turns ON = Good, NO Light = Not Good.
Hi there,
I finally traced the wires to the fuel pump connector between the rear seats. There are 3 wires - black, grey and purple. According to other posts, grey should be the hot wire to the pump, purple goes to the gas gauge, and the black is ground. someone correct me if I am wrong. I put a connector on the grey wire and hooked it up to a red power wire, I think coming from the starter, hot at all times, and put a test light on it. The light turns green, but the pump does not turn on.
This is all very confusing. When the ignition is off, the test light turns green, going from the red power wire to the grey fuel pump wire. But when I start the engine - after it cranks several seconds until oil pressure builds up - the light goes out. No light at all. But the pump runs. I just don't understand what is going on with this circuit.
BINGO BINGO BINGO!!!
I got it working. I hooked up the red power wire (looks like it comes from the starter) to a momentary push-button switch, and from the switch to a Tee connector on the grey fuel pump wire. Now when I push the button and hold it while starting the engine, the engine roars to life immediately. Problem solved!
