My wife was driving my 86 TPI T/A when it suddenly quit. I went to check it out, but didn't figure anything out.
I checked the fuel pump fuse=good
I bought a new relay and tried it in all three relay positions on the firewall. Still no hum from the fuel pump.
I pulled the carpet back behine the rear seats and found what I thought was the three fuel pump wires. 1 I am sure is the sender wire, 1 hot, 1 ground.
I turn the key to run and can't get the puel pump wire to turn hot.
Am I correct in asuming this wire should become hot w/ the key?
Please help me out on this.
Oh ya I put 12 volts to the G terminal in the panel and nothing but a click from behind the firewall.


------------------
86 Trans Am
red/silver t-top
305 TPI

 

YES there is a way to test it. I have an 86 2.8 FI and my car died the day I got it. I replaced the pump when it didn't need to be, don't make the same mistake. If you have an in-tank fuel pump then read on.

You have an oil pressure switch which, on my car, is on the driver's side of the engine toward the bottom with two wires going to it. It is about 2 inches deep and 1 inch round. Find it, unplug it and connect the 2 wire terminals with a paperclip. Don't let the paperclip hit metal or else you'll need new wireing! You should hear the pump buz.

Don't take my word that this won't blow your wireing, but I just took a look at the wireing for your car in my manual and the setup is similar to mine. So you might want to consult someone else, just in case.

-Erik W. 86 Firebird 2.8L FI

 

Sensor might bad showing no oil pressure, and that shots down my fuel pump? Good idea how about anyone else?

 

dude , just one thing. is your ignition module good? if its not, then you will get no injector pulse, nor will the fuel pump get its relay signal to operate!! if ya got HEI ignition, which i assume you do, then take off your distributer cap,take off your rotor, unplug the module,(be carefull not to break the plastic tabs, they are brittle) and hike up to your local parts house and get it checked. (most places do it for free) I am sure this is your problem..if not,let me know then i have another solution but please do this first. u should be fine. take care

 

Formula90: The HEI module would prevent the fuel pump from getting power, even tho the motor's not spinning?

Carguy00: That fuel-pump safety-switch is used as a backup to the "real" system, which is the fuel pump relay. GM's idea was that if the car's running, there's gonna be oil pressure- and that's what the safety switch does. Say your relay dies while you're driving- the pump will still get power.

I typed up a chart a lonnng time ago for Erik (above). He was getting a code 54- that's for when the computer senses the pump is getting low voltage. You can use it to check the wires at the pump, under the car, to see if your pump gets voltage.

Obviously, if you've got voltage back there, the pump's dead.

Here's the chart!!

------------------------------------------
Erik, here's that diagnostic chart for ya. Sorry it took so long for me to get it to you,
I wound up having to type it in, since I can't get to the scanner here at work. Let me
know what you find out!


-----------------------------------------------
DIAGNOSTIC CHART FOR CODE 54 (2.8L MPFI ENGINE)
-----------------------------------------------

Preliminary stuff:

Ignition off for ten seconds.
Ignition ON, listen for in-tank fuel pump
Fuel pump should run for 2 seconds after ignition on

Not ok? See "1"
Okay? See "6"

1. Ignition off. Remove the fuel pump relay, but keep the harness connected. This is
____located on the top of firewall, driver's side, on a relay bracket. It's the leftmost
____relay, with a connector that has these wires: Tan/white, black/white, green/white,
____orange, orange.

____Backprobe terminal "A" (that's tan/white, circuit #120) with a test light to ground,
____make sure you can see the test light from the driver's seat. Turn the Ignition to
____on (don't crank the engine/start the car). The light should turn on within 2 seconds.

____Light on? See "1A".
____Light off? See "2".

___1A: Repeat the test on CKT 120 (tan/white) at the rear body connector. You saw this
________connector when you replaced the fuel pump, it's in front of the tank, against the
________top of the underside of the car.

________Light on? Faulty pump ground or pump (ouch!)
________Light off? Fix the open (break) in circuit 120.

2. Disconnect the pump relay. Put the ignition on, engine stopped. Probe the fuel pump
____harness connector, terminal "E" (orange on the edge of the connector, Circuit 340)
____with a test light to ground.

____Light off? See "2A"
____Light on? See "3".

___2A: Repair open in CKT 340, this comes off of both your "computer-and-oil-pressure-
________safety-switch" setup and your "fuel-pump-and-computer-fuse".

________Your fuel pump/ECM fuse is under your hood, screwed down to the upper-frame-rail
________on the passenger side of the car, close to the air cleaner & black fuel-vapor-can.
________You'll see two little black boxes, each with two wires coming out of them, screwed
________down to the upper frame rail by one screw each. One of them has a red wire and an
________ORANGE wire coming out of it- that's your pump/ECM fuse holder. Pop the top off
________to see the fuse. (The holder with red & brown wires is for your MAF sensor, I
________just wrote about it under the Code 34 chart for Brian, on the mailbag below this
________message.)

________Now, two things could happen here. You could have a bad fuel pump fuse- check the
________fuse. If it looks okay, replace it anyway... sometimes a fuse can look good, but
________really be blown. The second possibility- I want you to probe the red wire on the
________fuse holder with a test light to ground. The red wire goes to the positive-
________junction-block on the radiator support- your pump/ECM fuse might not be getting
________any power! If the light doesn't light, check the red wire hookup. However, with
________either case your computer would be acting up, too, and I don't think you could get
________the car to start at all.

3. Connect a test light beteween pump connector pin "B" (black/white wire, CKT450) and
____pin "E" (orange wire from step 2, CKT340).

____Light off? See "3A"
____Light on? See "4"

___3A: Repair open CKT 340. The black/white wire isn't making a good ground. Sorry, I
________don't know where this grounds out to. I'd imagine it goes to a screw on the car.

4. Connect test light between pump connector terminal "C" (dk green/white wire, CKT 465)
____and ground. Ignition to "off" for 10 seconds. Note test light within 2 seconds after
____ignition "on".

____Light on? See "4A"
____Light off? See "5"

___4A: Faulty Relay! Hey that's cool, a $10-$15 part... but didn't you replace that
________already? The manual continues to test the "oil pressure safety switch", I'll put
________that test at the end of this message.

5. Ignition "off". Disconnect ECM A-B connector and check for an open, or a short to
____ground, in circuit 465- that's the dark green/white wire from the relay. It's on
____terminal "A1" of the ECM A-B connector.

____CKT 465 okay? See "5A"
____CKT 465 Bad? See "5B"

___5A: Check resistance across pump relay pins "opposite harness connector terminals B
________and C". Should measure 20 ohms or more to be good.
___________Resistance good? Faulty ECM A-1 connector, or bad ECM
___________Resistance bad? Replace Relay AND ECM.


___5B: Fix CKT 465. If CKT 465 was shorted to ground, re-check for a light "on"
________between harness connector terminal "C" and ground within 2 seconds after ignition
________"on".
___________Get a light? Cool, reconnect your relay
___________No light? Faulty ECM terminal "A1", or bad ECM.

6. Clear codes. Start engine and note service engine soon light. If the light comes
____on, check the code, if it's not 54 or you don't get a light, it's something else
____wrong, or an "intermittant" problem. But you get the code, so I shouldn't have
____even bothered typing this.

7. Backprobe ECM terminal "B2" (that's tan/white, CKT 120) with a test light to ground.
____Ignition off for 10 seconds. Note light within 2 seconds after ignition on.

____Light on? See 7A
____Light off? See 7B

___7A: Faulty ECM terminal "B2" or bad ECM.
___7B: Repair open circuit 120 to ECM terminal "B2".

*** Oil pressure switch test: Our 2.8's have two oil pressure switches. One is for the
gauge panel to control our oil pressure light (or gauge). The other one will keep the fuel
pump running if the relay happens to die while you're driving. I assume the theory was that
if you pull out onto a highway and the relay dies, you don't get killed? Anyway...

OP1. Start the engine, get it up to normal operating temperature. If you can, verify that
______the oil pressure is normal. Disconnect fuel pump relay- the motor should keep running.

______Engine stops? Bad oil pressure switch.
______Engine keeps going? See "OP2"

OP2. Reconnect fuel pump relay. Ignition "off". Find the fuel pump test terminal on the
______ALDL (Assembly Line Diagnostic Link, the connector above the driver's feet you used
______to get the error code out), which is terminal "G" -- the bottom leftmost terminal.
______Probe that terminal "G" with a test light to ground.

______Light off? No trouble found! (Doubtful...)
______Light on? Bad oil pressure switch. Oh yeah this switch is screwed into your engine
_________________block, right above your [edit] OIL (oops) filter, with an orange and a tan/white wiring
_________________harness on it.

Whew.

-Tom P (Hot rodded 1986 Firebird 2.8l)


[This message has been edited by TomP (edited July 31, 2000).]

 

dude PLEASE!!! dont be stuborn. keepit simple right? just check the module bro. it happened on my roomates 90 firebird which was exhibiting the same problems you describe. just check it. that is all i ask. if im wrong (which HAS happened before) then b_tch me out after you screw back the only 4 screws it takes to take it off!! take care...

 

Okay, so he has to pull the distributor out to get to the module, then remove the module, then hitch a ride to an auto parts store to have them test the module.

Or he can run quickly thru that chart I gave him, with nothing more than a volt-meter, and not disable his car.

Sure it might be the ignition module, and if he's not getting power to the back of his car, then it ain't the pump, right?

-Tom P (Hot rodded 1986 Firebird 2.8l) from http://www.v6fbody.com mailbags

 

I think I have a simpler way to check if the fuel pump is working.

I know Carguy00 said he had an 86 T/A, but I think his circuit is essentially the same as on my 91 Camaro.

My suggestion would be to just short the largest two wires together on the fuel pump relay socket. (If you do this to the other two relays (left and right fan), it will simply turn the fan on). FYI, you can do this test with the engine "off" since there should be +12 there all the time.

On my 91 Camaro, simply connect terminal E (goes to the fuel pump) to terminal A (goes to a +12VDC source via a fusible link which is hot at all times).

Simply connect the largest two wires together from the relay socket. The other wires are smaller (thinner) guage that connect to the relay coil and "prime connector".

All you have to do for this test is remove the relay from the socket and just short the largest two wires together from the socket. That will apply +12VDC to the fuel pump. Shouldn't take more than two minutes.

Still no fuel pump operation? Confirm that you have positive 12 volts at terminal A on the relay socket. You could also run a wire from the positive post of the battery to terminal E (fuel pump positive input) to see if it works. Make the connection quickly if you are not using a fuse, in case something is shorted between the socket and fuel pump.

[This message has been edited by Stuart Moss (edited August 01, 2000).]