another old gremlin i'm coming back to finally... but yea, with the key "on" and after the initial prime, if i hit the lights, brakes, sometimes even reverse lights, the pump will prime again. kinda' thought it was "noise" or interference in the vicinity of the coil and/or module. if the 4-pin connector on the dist that goes to the module is disconnected, it will not do it. i have an MSD dist, so changed the module and pick-up coil = no joy. can't remember all the troubleshooting i did before, but i think there's a ppl/wht wire on that connector, and that is the one the "signal" was coming from to "tell" the ecm to prime again. if, for some odd reason, this is caused by a voltage drop somewhere, i have no clue where to start looking... long time ago, another member had similar issue, but don't think he ever got any resolution, either. looking for ideas, help to get started on this again.

 

did some more searching of the wiring, components seemingly involved with this and only seem to find one common link between the lights themselves, but nothing related to the fuel pump/relay/ecm.

so, key on - pump primes... pull the headlight switch for marker lights, it primes again, unless the dimmer is all the way down. but pull the headlights on, pump primes again. as it does with the foglights. and switching hi to lo beams. if i hit the brakes, it only does it the one time, won't repeat. headlights, hi/lo switch, hi beam indicator all on circuit #11. light switch, marker lights, brake lites, tail lights all on circuit #9. common item is the fog lamp relay - both circuits are on it. nothing else appears to be related, even by a ground. so how in the world could "activating" any kind of lights simulate a "key-on" evolution to the ecm to prime the pump. it's receiving that "command" from the distributor high reference pulse input wire, circuit #430, from the ignition module. btw, i have not pulled / changed the fog lite relay yet, was trying to get some feedback here first. is it even possible a relay could cause this?

 

You are right when you say that these components don't have any link between them. Something's wrong in there, definitely.

I'd try disconnecting the fog-light relay. I'd also to disconnect the FP relay (to see if the power is coming from somewhere else).
You say you have an MSD distributor. Do you still have the separate coil? If so, disconnect it.

I know it's not much but it's a start. That's what I would do if I was chasing down this gremlin.


My thoughs:
Logically, if the ECM only PRIMES the fuel pump (meaning, it runs it only for 2 seconds), I'd suspect two possible causes of the prime:
1) loss of power to the ECM and when power is restored, it primes
2) faux tach pulse being generated - ECM detects it, assumes engine is running, turns on fuel pump .... no more pulses coming, ECM shuts down FP.

Very, very interesting.
Let us know what you find out!
Lou

 

If I remember correctly, and I'll have to check again, if I remove power from the coil (still separate coil), it will not do it. If I remove the small 2-wire cable from coil to module, it will not do it. I tried disconnecting just the tach wire at the connector by the coil, it will still do it. I know the signal is coming from that one wire cuz I went thru the painstaking process of elimination with every single wire going in to the ecm by using another set of connectors and jumpers. so maybe another thing to check on the coil is if there is a voltage spike coming in to it > going thru the module to the ecm...

Thanks for the response on the PM, Lou...

 

That definitely sounds like a voltage spike on the coil fooling the ECM into thinking that it's the tach pulse (engine turning).
The best would be to borrow a digital storage scope and put it on the white coil wire (and then the pink wire) and test with a falling edge trigger. I realize it's not something that everybody has in their closet but JUST in case you know somebody or actually have a scope at home (like crazies like me ).

A test light on the wire "might" possibly blink if the spike is long enoug but my feeling is that it won't be visible to a naked eye.

Lou

 

well... I bypassed the coil by jumpering just the pink wires together - no phantom prime then with the tach wire disconnected all together. I couldn't remember what the "test value" was supposed to be for the tach wire, but apparently "more than 10 volts". I also put a volt meter on the pink wire from ignition to coil and all it showed was a slight drop in voltage as I tried different lights, didn't see any kind of a spike that way. probably not the right way to be testing it, but... So if the tach wire is disconnected at the coil, it doesn't do it. So tomorrow I'll have to check that wire, even though the tach does work, and also the ground for it (G112) which just happens to be one of the grounds for the ECM as well... (remember you mentioned "loss of power" to ecm). BUT - in the past, I don't know how many times I have checked that ground... I could try a test light in a dark environment, too, maybe it'd be visible that way.

 

well, the saga continues... the white tach wire has the required "more than 10 volts" to it. i forgot to check it for a spike, though - will do it later. disconnected the fog light relay - no joy, but didn't expect that to fix it anyways. i also separated the grounds at G112, but only to the point of the 2 lugs, cuz there's 4 ground wires there altogether. left one lug attached, jumpered the other one somewhere else, then vice-versa. no joy. the issue seems to be between the coil and module. took that 2-wire cable off and checked it, seems to be good, not shorted, etc. or else something funky in the module (changed it before and pick-up coil, too) when power is supplied thru that cable, namely the tach wire. with it disconnected, it doesn't do it... so tonight i'll try a test light on both wires to see if i can see something... news at 11...

 

Alright, I'll tune in ...

 

This problem sounds similar to mine. I can turn on ignition and fuel pump primes normally, but if I turn on the right turn signal the fuel pump comes on and stays on. I can also see and hear the tach pulsing when this happens. The right turn signal doesn't work when car is running either. Left works fine .

 

possible back feed threw the gauge???????????? id check the grounds on the cluster

 

this is on the back burner for me again for now... but i think i checked the grounds long time ago. BigBabyLou had posted a response to another post a long time ago that suggested that a screw may have shorted a couple of wires along side the driver door sill that made me think about this issue, but i don't think that's the case with mine, although i haven't looked yet. at this point, anything is possible... just need to find the time to get back to it. more to follow...

 

Ding-Dong! Hiya, here to revive an old dead thread.
Did you ever figure it out? Having same issues like you, except when I activate hi-beams, fog lamps and/or the highest speed on the blower motor the fuel pump primes.

Can't have the hi-beams on, after a while the circuit-breaker in the headlight switch kicks the bucket for a while & kills all the headlights, then they come back on.

 

I know this isn't much help. But I got my IROC bone stock with 60,000 miles on it in 2001. If the key was forward and the engine wasn't running, turning the headlights on would make the pump prime for a few seconds. When I pulled the motor I checked what wiring I could, cleaned all my grounds. Made sure all the ground wires were in good shape. Installed a MSD distributor, MSD Ignition box..etc. Even with all that, it will still prime the pump if the the headlights are turned on in the run position with the engine off.

I never really bothered to look into it more. The car runs fine. If I drive at night. I start the car then turn the headlights on. There's really never a scenario for me where I'm turning the headlights on in the run position then starting the car. I always drive with my fog lights on. If my high beams are on I have no issues. I'm not saying this is normal but I have yet to find anyone all the years actually figure out why this happens.

 

It's strange, that's for sure. Haven't seen anything suspicious whilst lying with my back, hips & neck in 40 different angles whilst scanning the wires under the dash on the drivers side, nor under the hood. Cleaned every darn ground there too, even the one behind the engine going block-to-firewall. Gonna try under the "drinkers side" dash sometime later when I get home from this trip.

I might find something there. I do believe the instrument-panel has something to do together with all these...Things. Gonna see if Hawks has a new circuit print for me, since mine has seen better days anyway. I have cleaned it up as best as I could with some stuff I had laying around. I ordered a new ignition lock cylinder from RockAuto and eagerly await it.