madmachine

I've asked this question under another of my threads, bumped it, and still no answers. So, hopefully this will get more attention.

-Middle Pin, 8.50 volts. Is that correct?

I need to know if my Fuel Problem is before the clip or after it (fuel pump).

8Mike9

Too low, should see 12-14v, depending on whether the Alt is doing it's job.

madmachine

This was taken with the car off and a relatively new battery.... I guess it's time to rip apart the wiring harness... (Goodie Goodie)

Vader

Too low, but at least you might not have to drop the fuel tank.

I'd take a close look at the connection right at the tank, the ECM/FP fuse holder near the battery, and the relay and its connector. Those are the ones exposed to the weather.

Make sure your ground reference is solid when you're testing the voltage, too.

madmachine

I know my relay/clip is all messed up. I've replaced the relay - still no "Ignition On" fuel pump activation... but I have just been dealing with it. I'm not sure how to test the clip connectors (as far as where I should be seeing voltage - how much, and at what pin(s), but it hasn't prevented the fuel pump from running in the past. Fuse in the fuse holder was my first place to check.

I'm going to run a jumper lead from the neg. battery terminal down and back to the gas tank so I can use that as my ground reference.... a rusty bolt may not have been providing a great ground.

Given my F'ed up relay and what not, how would you proceed Vader? Oh, and do you still have the Imp's and Fiero's?

Arawn

For what it's worth, I'm having a dilema with my FP as well. When I tried to test the harness I couldn't read anything, in any configuration. But if I either of the wires connected to the tan/white I got a clicking noise. And when I hooked 12v from the batter to the tan/white wire on the relay my pump sounds very unhealthy..

Vader

This might be helpful:

madmachine

Oh boy oh boy oh boy....tomarrow is going to be so much fun!

I'm sure I'm going to be asking many many questions tomarrow!

TomP

You didn't mention what year your car is, but here's the code 54 chart from my '86 Helms manual. I added notes for a 2.8 V6, so your relays might not be in the same spot, but the wire colors should be the same. Good luck!

-----------------------------------------------
DIAGNOSTIC CHART FOR CODE 54 (2.8L MPFI ENGINE)
---------------------------typed by Tom P------

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.

____With the relay still connected, back-probe terminal "A" (that's tan/white, circuit
____CKT #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 if 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.)

________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 from the GM dealer! But, if you
________replaced that already, something's funny. You might want to do the chart again.
________Note: 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, if you got this far & nothing's wrong...)
______Light on? Bad oil pressure switch. Oh yeah this switch is screwed into your engine
_________________block, right above your oil filter, with an orange and a tan/white wiring
_________________harness on it.



Whew.

-Tom P (Hot rodded 1986 Firebird 2.8l)

Prem

Hi I have what could be a serious problem or just a simple one?
Anyway here is what happened,
I started my car and drove to town. About 5 hours later I tried starting my car and it would not turn over. I popped the hood and I heard a hissing sound from near the injectors. I then went to the back wheel and heard a hum at the gas tank. THE IGNITION WAS OFF. The pump ran the battery down! This problem occurs randomly. I also get hard starting as well as bad or no idle and than out of now where the car would start perfectly and drive after an hour. This pump problem is intermitant.
Could this be the relay? and if so where is this relay located. Should I follow the thread
"Is 8.5 Volts To The Fuel Pump The Correct Voltage Or Not!?!"
to troubleshoot?
Thanks
Prem, 87 GTA 350 TPI

Prem

oops I am sorry my post was suppose to start a new thread, I was reading this one and must have clicked the wrong button.
Since It is here any thoughts?

8Mike9

Prem,

Disconnect the FP relay....is the pump still running? If so, might be the oil pressure switch stuck closed.

Vader

I still have the small herd of Impala, but am thankfully "Fiero-free" They're a fun little car and I had no real reliability problems to complain about, but I think I found the limits of the car. I went from three to zero in less than 12 months. I still find a few odd parts lingering around here and there, however. Need something?

monte-ss

vader, what year diagram is that for? Im trying to troubleshoot a problem Im having with my fuel system but the pin config is different, Im working with an 89 TPI maf system do you have that as well I would greatly appreciate it. Unless its just my overlooking I cant seem to find anything related to fuel pump wiring in my GM service book either nor does it list the MAF system, I figured it would in the wiring diagram pages but no where to be found so far.

thanks
Jack

Vader

Monte,

That diagram is for an '88 TPI 'F' car (cold start). What kind of problems are you tracing?

monte-ss

I found the diagram I needed in the ECM code section of my manual, I am/was having charging problems, I cant get the alternator to put out enough amps to charge, and when I had the X-ray hooked up it was showing FP volts about a volt or so less than the batt volts, I was chasing through it to see if possibly had wires melted together since it was reading so low but Im not sure yet. According to the wiring schematics everything is ok with the fuel wiring so Ill continue to track through wires, the only way I can get the alt to charge is if I hookthe tan/white sense wire to the batt wire, so Im still at a loss there.

vjsimone

If you have an inline resistor, then yes 8.5vdc maybe right.

OrangeBird

iTrader: (1)

Whats with all the thread necro lately , digging up 15 a year old thread to post this nonsense to ?

There is NO "inline resistor" factory installed in the fuel pump circuit of ANY third gen F body car ! If your gonna go bumping ancient threads could you at least TRY to add to them by posting accurate information instead of useless conjecture ?

vjsimone

I'm not on the forum I thought I was, not even the right make.. lol , sorry about that.

But, as far as the thread age, my truck is 32 years old, so everything is relevant back 32 years......