Fuel Pump / Relay weirdness (Page 2/2)
phonedawgz SEP 14, 09:22 PM
OK, I see you have an MT. Pretty much any ECM will work then. You may get a SHIFT light at times you didn't want it, but I think in 88 they didn't even put a bulb in the socket.

This is what the stock PROM looks like under the cover - printed silver sticker on the right - Click on the IMG thing

This images is larger than 153600 bytes. Click to view.

Early 1226869s had a multipin socket for the PROM. Later ones used a carrier like the one in this pic.


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On your stall issue - Check your fuel pressure - Replace your plugs if they haven't been replaced in years. That includes the three on the front of the engine that are hard to reach since many times they have not been ever replaced.

[This message has been edited by phonedawgz (edited 09-14-2017).]

OriginalDoug SEP 15, 09:40 AM
Awesome, thanks for all of the help so far. I'll take a look and see what PROM is in there and go from there.

Also on a different note, I did notice yesterday while I was tinkering that while the pump wouldn't prime when I first turned the key, it would after I actually engaged the starter for a moment, as soon as I let off the start it would prime, then again if I hit the starter and let off again. Does that make sense?

Last I checked my fuel pressure was a bit low, in the mid 30's. So yes that is probably what is causing the stalling. I just thought it was weird that out of the blue the pump started not priming and then that same day I started getting the stalls... I figured I'd look into the relay/ECM before committing myself to a tank drop.
OriginalDoug SEP 15, 07:42 PM
Ok so I took a look at the PROM and it say's 'fty' and 9359 (or something like that). Like you said the 'fty' is the same as what is written on the sticker on the outside of the ECM.

So I am taking that to mean that the PROM is stock for the 85 instead of being reprogrammed for the '88 yeah?

So I should start searching for an ECM with the correct PROM for an '88 5 speed?


Before I go and do any of this, I do want to just say that I had the car running almost perfect, even with this wrong ECM and the pump always primed when I turned the key on up until the other day... Based on what we've discussed here are we for sure that the ECM is the reason for the non priming pump?

I'll do the plugs for sure. as far as the low fuel pressure is concerned is there anything I should try before dropping the tank. Supposedly the fuel pump was replaced not long ago.
Gall757 SEP 15, 08:07 PM
The original PROM for an 85 4 speed manual transmission car is FTY9355.
OriginalDoug SEP 15, 09:51 PM
That's probably what the number was, I couldn't remember by the time I got back to the computer.
Patrick SEP 15, 10:40 PM

quote
Originally posted by OriginalDoug:

That's probably what the number was, I couldn't remember by the time I got back to the computer.



Back in ancient times we used archaic items such as a paper and pencil.

phonedawgz SEP 17, 11:05 AM
There is an oil pressure switch that ALSO will turn on the fuel pump. Redundant but wtf. Later years (not Fieros) dropped the oil pressure switch and just relied on the relay.

Yes stock ECM. Stock Prom. Most who ran the 3.4 used the stock ECM and it works OK. So you should be able to use any 85-88 stock manual transmission ECM, either SERV number, along with the stock PROM that comes with that ECM and it should function for you.
OriginalDoug SEP 18, 09:15 AM
Ha! yes I should've written it down, I stupidly thought I'd be able to remember it.

Thanks for all the help, I'll pick up a new ECM when I find a good deal on one and see if that fixes the priming issue.

Going to do the plugs and see if that helps the stall issue at all.

If not I guess I'll have to drop the tank and either replace the pump or the little hose that disintegrates in there. Hopefully that will fix the fuel pressure issue.
altownsend AUG 31, 02:40 AM
1986 V6 4-Speed Fiero

I had this problem also. Initially, the fuel pump would not prime, so, after a few engine revolutions from trying to start the engine, the oil pressure switch activated the fuel pump relay. To alleviate the problem, I installed a momentary push button on the green wire running 'from' the ECM to the circuit and activated the fuel pump manually when I first started the car.

Now, I cleaned the engine yesterday, and now, the engine will not start. I no longer get the fuel pump to activate when oil pressure is up. I can still manually activate the fuel pump with my momentary push button. I can also run 12VDC to the brown/white wire at the oil pressure switch connector and get the fuel pump to activate. I can also, with the fuel pump relay removed, run 12VDC to the brown/white wire at the relay connector and activate the fuel pump. I can also run 12VDC to the brown/white wire at the ALDL connector and activate the fuel pump.

Now, since the oil pressure switch does not activate the fuel relay, and the relay does not activate when the oil pressure builds up, could it be that my fuel pump relay has become defective? The engine turns fine, when I put a little starter fluid in the intake housing, I get a start-up attempt, but the engine does not catch.

Does anyone have a solution?

I will replace the relay on Monday. It is a new relay (about 5 months old)

Question:

Can someone walk me through the circuitry that activates the fuel pump relay when the oil pressure switch reaches the required pressure to activate the fuel pump relay? I want to test the circut at each step to determine if I have a bad circuit or a bad relay.
olejoedad AUG 31, 12:19 PM
The OP sender has a pressure activated switch the turns on the FP.
It does not turn on the relay, it is wired in parallel with the relay.

KEY - ON should show momentary battery voltage at ALDL D if relay is energizing.
If no voltage, try cranking the engine. If you see voltage at ALDL G, the OP switch is supplying voltage to the pump.