Real Fiero Tech

Fuel pump won't prime when the ignition is turned on. I checked the wiring and all that checked out according to my 88 service manual. The relay is agetting a signal from the computer so I don't think that is the prob. I switched relays between the a/c and the fuel and it did nothing. I sprayed a bit of carb cleaner down into the tb and it fired but died, then the fuel pump primed.

THing is, even after oil pressure builds according to the guage in the car while cranking, the engine still does not fire.

The pun said the oil pressure sender could be bad. Ideas?

Edit to add: I can hear the relay clicking when I turn the key to on but the pump still doesn't prime.

pull your oil pressure sender plug and jump the two slots across from each other, this will turn your pump on, and you can diagnose from there.

dont fuck with the sender
just bridge to two bottom far oposite pins on the ALDL i believe it is , that should override and turn on the fuel pump. look at a diagram first as im not positive. I'm putting money on its dead, i've replaced 3 and one just died when i filled up the tank.

I tried jumping the pins on the aldl. The power and the fuel pump pins and that did nothing. I will try the oil pressure connector tomorrow.

I had to use a 14 gauge wire to jump from the ALDL fuel pump pin to the cigarette lighter positive wire to get the pump to turn on mine. I got a false negative thinking my circuit tester would cause it to spin.

ok I want to get this figured out so I went out and I jumped my cig lighter to the aldl fuel pump slot. Pump fired and turned on and primed the system. I did not try to start it though as its late and its very loud when running(open dump)

So now I am confused. What does this mean? Relay? oil pressure sender? Remember I can hear the relay click when I turn the key to on but does that necessarily mean its good if it clicks?

The ALDL connector bypasses the relay and gives 12 volts to the pump, so it's the relay--or at least the relay wiring.

I Just to be absolutely certain, I'd check the wires going into the relay to make sure it's getting 12 volts AND it's grounded. It's suspicioius that both relays aren't working so I'm leaning toward the grounding. I think the relays share a common ground at the end of the head or to one of the bellhousing bolts; somewhere in the general vicinity of the slave cyl. Might be worth double checking those.

There's a timer on the priming routine isn't there? I think the ECM only fires it once every 30 seconds or so.

Yea I checked the wiring diagram and I went through the step by step process outlined in the GM manual. There is power getting to the relay from teh computer as I checked that. I believe thats the grn/wht wire. When hitting the key, the wire was hot for about 2 seconds, then power dropped off. I did move some grounds recently. More specifically the ones that attach to the head by the slave cylinder, and also the one that bolts to the firewall near the relays. I relocated them, but not sure if this is where the relays grounds are located. I guess I could relocate them back and see what happens, or use my test light where they are now to see if they are grounded.

Check the grounds and they all seemed well. THe ground coming off the computer to the relay taht goes to D1 on the computer has a good ground. Only thing left to replace is the relays. LEts hope that works. Otherwise its me jumping the damn pump everytime I get in the car.

Shaun, do you know anything about how to wire up a relay, or how they work?

I don't want to undermine you if you already understand a basic automotive relay.

Just in case you don't...

To test the relay apply +12v to post 85 and ground to 86. They are the two vertical-facing posts on either side of the relay when looking at it like the picture below:



It doesn't matter which one gets power and which one gets ground. If the relay is operating correctly, you will be able to tell.

I don't want to sit around and wait to see if you already knew this, so I just posted it in case that it may help.

Shaun's just too much Fiero owner. He doesn't want to go buy a new relay.

I've got the same identical problem now. I was relying on the oil pressure sender to start the Fuel pump in my V8 swap. I can apply power at the ALDL connector and the pump works fine, but the oil pressure switch won't trip the pump after the motor is running.

The oil pressure gauge itself is working (and registers north of 80 PSI) and the fuel pump worked prior to the swap.

Yes, the fuse is fine.

I might just move it to the 12 volt distributor wire. This is bullshit.

WTF.

Edit: Ok. Help out the slow guy a minute. Am I wrong, or is everything else but the ECM bypassing the relay?

I pulled the oil pressure sender and jumped the two appropriate terminals and the fuel pump spinned up. I've got a bad oil pressure sender, don't I?

Sorry for the thread hijack.

If you want to have visual confermation of power going to the fuel pump Hook a low wattage 12V lightbulb between the Ground pin and the Fuel pump pins on the ALDL port. The light will light up when the pump is sent power to turn on. If the light is on and the pump isn't running BAD pump. If neither is on then Bad relay, Fuse, Wire, Or in worse cases computer on Prime up or sender after it's running or no oil pressure after first start.

Fuel Pump = Pin G
Ground = Pin A

txf wrote:If you want to have visual confermation of power going to the fuel pump Hook a low wattage 12V lightbulb between the Ground pin and the Fuel pump pins on the ALDL port. The light will light up when the pump is sent power to turn on. If the light is on and the pump isn't running BAD pump. If neither is on then Bad relay, Fuse, Wire, Or in worse cases computer on Prime up or sender after it's running or no oil pressure after first start.

Fuel Pump = Pin G
Ground = Pin A

No shit. Read the thread you dumbass.

<sorry>

Where the hell does anyone in this thread speak of using a light for visual confermation? Hmm no where! Shaun talks about using a test light for ground confirmation. People talk about jumping the fuel pump pin to the cigarette LIGHTer to manually run it. But no one speaks of using a light jumping the pins to CONFIRM that the POWER is GETTING through the 3 systems to get to the FUEL PUMP! That's MY POINT! The rest is just a how to incase someone else wants it all together! So before you have DeJaVu while reading my post and calling me a dumbass hit Ctrl F and search for LIGHT or bulb on this thread!

DumbASS!

Chris-Nelson wrote:Shaun, do you know anything about how to wire up a relay, or how they work?

I don't want to undermine you if you already understand a basic automotive relay.

Just in case you don't...

To test the relay apply +12v to post 85 and ground to 86. They are the two vertical-facing posts on either side of the relay when looking at it like the picture below:



It doesn't matter which one gets power and which one gets ground. If the relay is operating correctly, you will be able to tell.

I don't want to sit around and wait to see if you already knew this, so I just posted it in case that it may help.

I actually didnt' know this. I am guessing the relays will make a clicking sound or something when I do this if they are good? I bad no noise at all?

Thanks for the tip

relays have a wound coil in them that becomes a magnet when power is applied across it, which then draws a connection closed

a Dry relay will audibly make a click. But these have grease in them to protect them from moisture so hearing a click that happens at the same time you turn a key that also makes a click will be very difficult if not impossible if the grease is cushioning the contacts connection. USe a test light across the A and G pins of the ALDL. If you turn the key to ON and the light comes on you're relay is good no doubt about it!

Just wanted to say this thread is priceless to me.

I just got my 88GT 3.4 DOHC back, and it won't start--no fuel.

Well the pump doesn't even prime. So I'm going to for the next week do the diagnosii that you all explained and see how it works. Thanks, and good thread!

If you are going to test a relay, just pull it out and use a few pieces of wire on the two terminal that get ground and "+" 12v. If it is in your hand you should feel the "switch" inside move and hear the click.

If it is a bad relay, you will hear one of two things>
1. It will make a fluttering or buzzing noise,
2. Or it will make no noise at all.



pin 87 is basically an input. whatever you want the relay to produce (+12v or ground) goes here.

85 & 86 are two sides of a magno-electric coil. When you apply power and ground it energizes the coil and the coil throws a switch.

30 is the output.

when the coil is not energized, 30 and 87A are connected.

when the coil IS energized, 30 and 87 are connected.