ColinOpseth

Hey guys,
I have an '87 IROC that's been sitting for about six years now. Looks like I had some rodent friends get up in my engine compartment and have lunch, dinner, and a few BMs all over everywhere. Car had zero wiring issues when parked.

Fuel pump doesn't prime. I had some chewed wires over there I soldered. Fuel gauge shows that the level is at infinity (no issue before it was parked).

I have some chewed wires over by the heater core. See pic. Could this be my issue? I have no fuel pressure at the Schrader valve so I know the pump hasn't primed. Added 5 gallons of fuel to the tank so I know it isn't out of gas.

Thanks,
Colin

Ace

iTrader: (2)

In the 3 pack of relays in the front corner one is for fuel. You can jump connector to test or use a multimeter to verify voltage.

That main pack that goes across has all the main power feeds so likely it's not good if there was damage.

ColinOpseth

Hey Ace,
I had a bit of damage in the area on the firewall over there by the brake booster. I fixed all the damage I could see. There's a large bundle with flex tubing that runs across the rear of the engine by the heater core. The connector in the first picture is the one that I'm not seeing on any wiring diagrams. It looks like it's held to the firewall with a single bolt and one end of the connector has a black wire with blue stripe coming out the top. Any idea what the wire is?

I didn't spend too much time on it today. Going to check for spark tomorrow. Engine turns over good (new battery) but no pressure at the Schrader. I'll trying jumping with a test wire to see if I can get the pump to run that way. Also, should see 12v on the green wire at the ECM during crank, right?

Thanks,
Colin

Ace

iTrader: (2)

I've never seen that plug on any of my thirdgens. Would have to dig thru the wiring diagrams for 87 on the engine side probably.

mmadden55

It may also be a bad pump or clogged filter.

Might try jumping direct to pump to see if it comes on.

Bob88GTA

iTrader: (2)

When you turn the key on, do you get the 2 second Fuel Pump prime? Check your relay by the brake booster.

NINÅ

ColinOpseth

Hey guys,
Thanks for the help. Had a bit more time to work on it today. Here's what I came up with... No matter what I did, the pump wouldn't prime.

This is what I did:
1) Removed the fuel pump relay. Probed for 12v on the orange white (always hot) and got a solid 12v.
2) Checked the 20A fuse by the battery. Fuse is good.
3) Used a bulb probe and saw a solid ON with the key in crank and run on the green/white wire at the relay.
4) Saw a 2 second ON with bulb probe on brown/white at the relay.
5) Ran a 12v lead from battery to G on the ALDL. No prime or run.
6) Jacked up the car and disconnected the pump at the connect on the rear bulkhead near the tank. Ran a ground to frame and black on the pump side of the connect. Ran a 12v from the battery to the gray wire on the pump side of the connector. No run.
7) Checked ohms on the pump. Solid 3.5ohm from grey to black on the pump side of the connector.

I still see the fuel level on the gauge as infinity. Something isn't right here... I'm thinking bad pump, but how could the fuel level also act like it's shorted to ground? Those wires are run under the floor, right? Thinking maybe I got some chewage under the dash somewhere, but I'm not sure.

So, questions..
1) What should pump resistance be across the black and grey terminals?
2) What else could potentially cause a short to ground on the gauge?
3) Any other troubleshooting steps you can think of?

Also, ECM flashes code 12 only. No 54.
Thanks,
Colin

ColinOpseth

Just checked at the connector there on the car side with the key on:
- voltage from black to gray is 0v.
- voltage from black to pink is 8.5v

Rechecked my connections and tried to run the pump. Got the obligatory spark from the battery positive to gray on the pump connector. No run. Bad pump? Doesn't solve the mystery of the gauge, though.

Thanks again,
Colin

ColinOpseth

Another update..

Removed the fuel pump relay. Applied 12v to brown wire with white stripe. I got 11.06v on both the gray wire and pink wire on the rear bulkhead connector at the pump. Am I looking at a short to ground situation?

Thanks,
Colin

ColinOpseth

No one has any ideas? Thinking I need to complete the circuit and test for good connection from the relay to the pump, right? Does anyone know where the gray wire at the connector junctions into the brown wire with white stripe? I've read that wire is routed under the carpet inside the car..?

ColinOpseth

Anyone? Had a few people chime in...kind of doing more than throwing questions at a dart board..

Maverick H1L

iTrader: (8)

Well, it seems to me that the pump resistance should be a bit more than 4 ohms as you're reading. Not having my old one to compare, I don't know for sure.

If you have the back of the car in the air, next time you apply power to the pump circuit, use a rubber mallet or something and hit the bottom of the tank. You don't want to dent the tank, but the objective here is to possibly jar the pump enough to work if it's going to.

Fuel pump/sending unit wiring runs from the 15-pin connector behind the driver's kick panel down under the door sill and then across the front of the driver's rear seat to the rear body connector on the front of the gas tank hump. The ground for the sending unit is under that seat bottom on the support.

Fuel pump power wiring should be tan/white from the front to the back. If part of it is gray, something has been replaced a some point. Also, the pump wire runs from the passenger's side of the dash, C207, to the driver's side where it joins the 15-pin C208. It's very likely your rodent issue chewed up the pump wire by the HVAC box.