I was walking out to my car to get something when I noticed a hissing sound comming from somewhere in the rearend. I thought it was a tire leaking, but as I went to check I found that the fuel pump was running. This is with the car sitting--probably hadn't been driven for 1.5 hours.

It started and everything when I turned the key, but I didn't know if the battery would last until the end of work, so I decided to take the positive battery terminal off. Out of curiousity, I reconnected it, and then the pump wasn't on. So I thought I "fixed" it; went inside to wash my hands, came back out to lock the car, and then the pump was going on its own again. This all started today.

Any ideas? Thanks...

 

I might be able to actually help on this problem One time I accidentally disconnected my Ignition control module from the distributor and when i plugged it back in the fuel pump was going and going and going. So like you i disconnected the battery but it was too late and i had fried the module. Just a thought but it might be the module. If not maybe your fuel pump relay has shorted out. I also think that the oil pressure switch has something to do with it but im not totally sure it would make your pump keep running. Hope this helps at least a bit.....

 

Well, the weird thing about my situation is that I didn't do anything to prompt this to happen (haven't done anything under the hood 'cept standard maintinence; no tinkering or modding). It completely started out of nowhere.

I was thinking fuel pump relay, too... I don't know if I need to check my ignition module or my oil pressure switch as I can't see what either of them have to do with the fuel pump (directly). I don't know what could cause the relay to do that though--mabye it's corroded and the contacts got stuck? Where is that relay, anyway?

One other thing... you know how when you turn you key to ignition (right before you actually start it) the fuel pump turns on for a few seconds to pressurize the system? Well, I payed special attention to the sound of the pump when I turned my key to that position: the fuel pump got louder (got more power, mabye?) for that few second interval where it would have otherwise turned on and then off. The only difference here was that it went from being on, then louder for the few seconds, then back to just being on...

 

Oh man I hope you didn't burn out the pump. When my first fuel pump died, it sounded sickly as it primed (with engine off, key on for a few seconds). When the second fuel pump died, it sounded like I had an angry nest of bees inside the tank.

Is this the '88 V6 car? If you follow this chart, you'll be able to test the relay and the oil pump safety switch. It's right out of the GM Service Manual for '86 ( http://www.helminc.com ), and even though it's for code 54, it tells you what wires to check out. I'd say first bet, though, is to unplug the relay and see if the pump shuts off. I've also added instructions telling you where the fuel pump relay is... hopefully they work for your '88 car, you'll have different shaped relays compared to the ones GM put in my car.

-----------------------------------------------
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)

 

uhhhhh....yeah what TomP said....haha :hail: After you test all that you should have the problem figured out

 

I'd vote for the stuck oil pressure switch, or stuck relay

 

Wow! Thanks for posts everybody--TomP: I hope that was just a copy-and-paste job. 'cause if it wasn't, you're going to be pissed when I tell you that my car actually "fixed itself"!

Well, I say that--it's just not having that problem anymore. Not sure why it wanted to do that all-the-sudden. Anyway, thanks again--I've got this post and its replies saved so that I can reference it if the problem arises again...