Ok here is the problem... I tried to crank my Duke today and got nothing. I removed the fuel line that goes into the filter and turned over the motor, no fuel pumping. The guy I bought my coupe from said his mechanic said that it was a problem with the computer. I have 3 different computers that I have tried and still no fuel flowing. I really dont think its a computer problem. His mecanic said the fuel pump is not getting power.

Has anyone experienced this issue? I am wondering if I need to just get another fuel pump and try it or if this may be a common issue with these cars and there could be a simple fix that I don't know of maybe?

Thoughts, ideas? Thanks in advance.

Try switching the Fuel and A/C relays if your car is equipped with A/C. Either way the relay is only 12 bucks at the partstore and is easy to swap.

IF you dont know where it is then open the engine bay and its just to the left of the hood supports on the firewall. I think the one on the left IIRC

Hope this helps.

Ok, which is the ac and which is the fuel relay? Fuel on far left, and AC on far right or AC in the middle? Thanks for the advice.

You should have two right behind the driver seat in the engine bay. AC is on the right (4 wires) Fuel on the left (5 wires)

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You can't go by the arrangement since they can be changed. The fuel pump relay has GREEN/BLACK, DARK GREEN/WHITE, TAN/WHITE, AND BLACK wires on it.

[This message has been edited by phonedawgz (edited 09-12-2010).]

OK Thanks guys. I will look tomorrow. I just made it in from church. I was delayed because I am on the fire department and I came up on a grain truck on fire and had to work it. Thanks for the info.

But, I have 3 relays behind the driver seat in the engine bay. I will check the coloring on it and see if I can swap them around to get it pumping. Thanks guys.

What year is your Fiero?

The fuel pump should run for a second or two when you first turn the key to "on", then turns itself off. If it does not, have someone turn the key on while you hold your hand on the relay--you should feel it "click". This means the relay is getting a sig from the ecm to trun on during that 2 second bulb test sequence. Of course, the fuses have to be good for both the ecm and for the fuel pump, AND, just because the relay energizes (clicks), that does not neccessarily mean that the internal contacts are closing the circuit.

If you have an ignition problem of some sort, this can also prevent the fuel pump from coming on while cranking. While cranking to start, the ecm will not turn on the fuel pump relay, unless it senses a spark refenernce pulse from the ignition system (distributor) but, there is also a redundant circuit built into to the fuel pump wiring, that sends 12 Volts directly to the fuel pump, when oil pressure builds to about 4psi--independant of the fuel pump relay. IOW, assuming the wires and connections themselves are good, the fuel pump should run while cranking to start even if the fuel pump relay is bad--once oil pressure builds while cranking. The 12v connection for this, comes from the oil pressure switch BTW.

.

There is also, a fuel pump test terminal on the ALCL interface behind your cig lighter bezel. I forget which pin it is now, but you just apply 12 v to that terminal and it "should" send 12v straight to the fuel pump.

I don't have the circuit diagram handy, but all the connections that run the fuel pump independant of the ecm are on the "output" side of the FP relay--or "teed" into the wiring just downstream of the relay.

Ok, here's the diagram:

[This message has been edited by maryjane (edited 09-13-2010).]

quote Originally posted by maryjane: What year is your Fiero? The fuel pump should run for a second or two when you first turn the key to "on", then turns itself off. If it does not, have someone turn the key on while you hold your hand on the relay--you should feel it "click". This means the relay is getting a sig from the ecm to trun on during that 2 second bulb test sequence. Of course, the fuses have to be good for both the ecm and for the fuel pump, AND, just because the relay energizes (clicks), that does not neccessarily mean that the internal contacts are closing the circuit. If you have an ignition problem of some sort, this can also prevent the fuel pump from coming on while cranking. While cranking to start, the ecm will not turn on the fuel pump relay, unless it senses a spark refenernce pulse from the ignition system (distributor) but, there is also a redundant circuit built into to the fuel pump wiring, that sends 12 Volts directly to the fuel pump, when oil pressure builds to about 4psi--independant of the fuel pump relay. IOW, assuming the wires and connections themselves are good, the fuel pump should run while cranking to start even if the fuel pump relay is bad--once oil pressure builds while cranking. The 12v connection for this, comes from the oil pressure switch BTW. . There is also, a fuel pump test terminal on the ALCL interface behind your cig lighter bezel. I forget which pin it is now, but you just apply 12 v to that terminal and it "should" send 12v straight to the fuel pump. I don't have the circuit diagram handy, but all the connections that run the fuel pump independant of the ecm are on the "output" side of the FP relay--or "teed" into the wiring just downstream of the relay. Ok, here's the diagram:

Thanks for the info. That diagram is German to me but I have a neighbor that can read it like magic! Thanks I will show that to him.

Here is a pic of my relays. I stated above that I have 3. Here is a pic I took this morning.



So, your saying that there is a 12v connector under the console that will allow me to give a direct 12v to the pump? That would be very easy to test if I could find that. Thanks.

Since there is three, I know that Fiero is an 84. I pretty sure the 3rd one (left most one) is for the tail-lights, since 84's used a relay for the turn-signals.

The fact that your relay clicks, omly means that you have control voltage going to the relay at terminal "A"--that is the circuit that energizes the little coil inside the relay. That magnetic coil "pulls" the contacts closed to complete the circuit from terminal "E" thru the contacts, to terminal "B" , I have seen relays that worked, in the sence that the coil clicked in, but the contacts were either burned, pitted, or corroded, and the pump still didn't work, which is why Ramespride advised you to swap the FP relay out with the A/C relay--they are identical relays. You want to test for 12V at terminal "B" to make sure you are getting voltage thru the relay to the FP circuit.

There is a pull apart connector in the tan/wht wire just before it goes down to the tank. That connector, is almost always hidden behind a big silver heat shield on the firewall behind the exhaust side of the engine. It is fed directly from Terminal "B".

The aldl is behind the cig lighter bezel--just take out the 2 little t-15 torx screws, remove the bezel, and you will see a plastic connector in there with a bunch of pins in it. That's the aldl--or alcl as they call it in the wiring diagram. It lookie just like this:


Apply 12v to the terminal marked Fuel Pump in the pic, and the pump should run--as this bypasses the ecm, the fuel pump relay and the fuel pump fuse. If it doesn't run, either your pump is bad, or you have a break in the tan/white wire.

btw GADjet, if you will click on the "search" button (top right of this page) it will bring you to some search options. Every post ever made in Tech, GeneraL, and OT since the beginning of this website are archived, and available thru search, as well as current posts from all sections. Options are to search by subject, username, or entire thread. Type in fuel tank, or fuel pump, and everything you ever wanted to know will be there. Not trying to sway ya from asking questions--just wasn't sure if you noticed the website had a search.

[This message has been edited by maryjane (edited 09-14-2010).]

quote Originally posted by mattwa: Since there is three, I know that Fiero is an 84. I pretty sure the 3rd one (left most one) is for the tail-lights, since 84's used a relay for the turn-signals.

In that case I would say to RULE OUT one of them... Turn on the emergency flashers and the one clicking then is the turn signals and NOT the pump.

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quote Originally posted by mattwa: Since there is three, I know that Fiero is an 84. I pretty sure the 3rd one (left most one) is for the tail-lights, since 84's used a relay for the turn-signals.

If it's an 84, there should be 4 relays if he has AC. I have three 84's sitting outside--they all have 4 relays there. 2 on top--two on bottom. 84 used a separate relay for left turn and another for right turn afaik. I could be wrong on that, but I have heard the relays clicking back there when my turn sigs were on or if I pressed the brake pedal down. Kinda hard to see the 4th one, but it's down there on the bottom right--behind the harness. I've had 4 84's, and all were configured exactly this way, but someone told me a sport coupe only had 3 relays there. All mine are Indys or SE.

[This message has been edited by maryjane (edited 09-13-2010).]

quote Originally posted by mattwa: Since there is three, I know that Fiero is an 84. I pretty sure the 3rd one (left most one) is for the tail-lights, since 84's used a relay for the turn-signals.

It is indeed an 86 Coupe. According to the title anyways. And it does have AC. I don't have a clue what the other relay is for though.

quote Originally posted by maryjane: The fact that your relay clicks, omly means that you have control voltage going to the relay at terminal "A"--that is the circuit that energizes the little coil inside the relay. That magnetic coil "pulls" the contacts closed to complete the circuit from terminal "E" thru the contacts, to terminal "B" , I have seen relays that worked, in the sence that the coil clicked in, but the contacts were either burned, pitted, or corroded, and the pump still didn't work, which is why Ramespride advised you to swap the FP relay out with the A/C relay--they are identical relays. You want to test for 12V at terminal "B" to make sure you are getting voltage thru the relay to the FP circuit. There is a pull apart connector in the tan/wht wire just before it goes down to the tank. That connector, is almost always hidden behind a big silver heat shield on the firewall behind the exhaust side of the engine. It is fed directly from Terminal "B". The aldl is behind the cig lighter bezel--just take out the 2 little t-15 torx screws, remove the bezel, and you will see a plastic connector in there with a bunch of pins in it. That's the aldl--or alcl as they call it in the wiring diagram. It lookie just like this: Apply 12v to the terminal marked Fuel Pump in the pic, and the pump should run--as this bypasses the ecm, the fuel pump relay and the fuel pump fuse. If it doesn't run, either your pump is bad, or you have a break in the tan/white wire. btw GADjet, if you will click on the "search" button (top right of this page) it will bring you to some search options. Every post ever made in Tech, GeneraL, and OT since the beginning of this website are archived, and available thru search, as well as current posts from all sections. Options are to search by subject, username, or entire thread. Type in fuel tank, or fuel pump, and everything you ever wanted to know will be there. Not trying to sway ya from asking questions--just wasn't sure if you noticed the website had a search.

I will try the B Terminal to see if I can get power directly to the pump and see if it will start. MJ, I just found the search that afternoon while looking at the car. Thanks for showing me that though. You all are a tremendous help and I greatly appreciate your help.

check the oil pressure sending unit too, if it goes bad, it will kill voltage to the fuel pump to prevent engine damage.

quote Originally posted by larini74: check the oil pressure sending unit too, if it goes bad, it will kill voltage to the fuel pump to prevent engine damage.

Even with bypassing the ecm with the B terminal?

I did notice when I put a little fuel in the throttle body to see if it would run that the oil pressure was pegged out beyond 80 PSI. I dont know if its a bad sending unit or just faulty Oil Pressure guage.

The oil pressure sending unit/switch is a combo device that has a switch to supply power to the fuel pump AND has the gauge sending unit in the same housing. The two outside contacts of the connector are the switch portion The middle contact provides a variable resistance path to ground to control the oil pressure gauge.

The oil pressure switch is a redundant switch parallel with the ECM/Relay 'switch'. The fuel pump can be powered by either of these soruces. In a proper operating Fiero both would be 'on' during normal engine operation.

Usually when the sending unit of the oil pressure sender/switch goes bad the oil pressure gauge will peg full at a low oil pressure. (just like yours is doing)

Many replacement switch/sending units are miswired internally.

The oil pressure switch has no 'short to ground' function to kill the engine under low oil pressure situations.

IF someone's fiero's ECM/relay portion of the redundant fuel pump power circuit isn't working, AND the oil pressure drops below the switch's threshold, the switch will turn off and of course with the resulting lack of fuel pressure, the engine will die. The way this 'mystery' trouble is reported is the engine dies when oil pressure is lost, and can't be restarted till the engine cools down. After the engine cools down enough the oil thickens and after some cranking, the oil pressure switch will again turn on and restart the car. This isn't a design feature of GM's. The ECM/relay IS suppose to be working, and as a redundant supply line for fuel pump power, would prevent the stalling that occurs.

The pin you should be checking on the ALDL isn't pin B but pin G - The previous poster was talking about jumpering from pin D(he said E) to pin B - ON THE RELAY SOCKET, not the ALDL.

On the relay socket you should always have power on pin D. When the relay is energized by the ECM the relay connects that power from pin D (Orange Black) to pin B (Tan White) and thus sends power to the fuel pump. You could insert a wire from pin D to pin B to bypass the relay as a test to see if it makes the fuel pump run.

Note this drawing is orientated 180 deg from the previous picture. Use the center plastic lug to figure out how your's is orientated. The two side plastic lugs are deceptively drawn on this picture which could make you think it is upside down from what your's is like. Again use the CENTER lug to determine your orientation. Study it and you will understand what I mean.



The previous pictures do have it shown as the correct pin.

As a final check before dropping the tank, I would take a test light into the fuel pump pin on the ALDL and also confirm that voltage is being supplied there by the ECM. Ground the other side of the test light. You should see the test light come on during the "prime". If you crank the engine you should also see the test light come on and stay till two seconds past the last rotation pulse of ignition sent by the distributor. Look at C502 (the yellow connector at the firewall that comes from the fuel tank) Stick a paper clip up into the tan/white wire's connector from the back side of the tank's wireing harness and confirm you have voltage there. Then take a second paperclip and insert it into the black wire's connector again on the tank side of the connector. Use that as your test light's ground. Again check for power during prime. IF you're getting power there during prime, and the fuel pump is not running, then quite certianly the problem is either the fuel pump, or in the fuel pump harness and requires you to remove the tank.

[This message has been edited by phonedawgz (edited 09-15-2010).]

I had this happen to me. And the ground came off inside the fuel tank.

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Phonedaws. Did you used to work for GM or something? That's the most endepth answer to the simplest question I have seen yet. It actually gave me a better understanding. I was not doing this the correct way. Heck, i was trying to prove power from my battery in my silverado. :-/

I will definitely try this tomorrow afternoon. Thanks for the info.

It really sounds like a pain in the butt to me. But I guess I gotta get her running some way. Right?

OK... I shot a video with my iPhone 4 yesterday trying to figure this out. You will see me crank it once with fuel poured into the TB. It does run with fuel in. However, you will see me after that try to crank it after changing the relays. Here is a pic of the relays. Remember we discussed the relays may be a problem? They look corroded but I think they are making proper contact. I did check the module under the cig lighter. I do get 12v on the pump wire when I turn on the ignition and when I crank, but my pump does not pump. :| Here is the video. http://www.youtube.com/watch?v=qX1dBdkvOKE

Clean the relays--the black goop is from factory to insure good connection and keep moisture out , but gets ugly after 20+ years. Connect the relays back up.
Pull the connector apart where the FP wire turns down toward the tank--should be behind the heat shield. This, is the LAST connector before the pump.
1. Have someone turn the key to "on", while you check for voltage at the connector half coming from the ecm/oil press sw/fp relay. No voltage means you aren't getting signal from the "upstream" portion of the circuit.
2. Apply 12V to the pump wire connector half that goes down to the pump--if no pump runs--you have in-tank problems. I believe it is the Tan/white wire.

[This message has been edited by maryjane (edited 09-20-2010).]

quote Originally posted by maryjane: Clean the relays--the black goop is from factory to insure good connection and keep moisture out , but gets ugly after 20+ years. Connect the relays back up. Pull the connector apart where the FP wire turns down toward the tank--should be behind the heat shield. This, is the LAST connector before the pump. 1. Have someone turn the key to "on", while you check for voltage at the connector half coming from the ecm/oil press sw/fp relay. No voltage means you aren't getting signal from the "upstream" portion of the circuit. 2. Apply 12V to the pump wire connector half that goes down to the pump--if no pump runs--you have in-tank problems. I believe it is the Tan/white wire.

TY MJ. I am going to do that this week. (when I find time)

THREAD REVIVAL!!!!

the 84 SE I'm selling doesn't run due to either a bad relay or fuel pump.
the relay doesn't click on. so I'll try the direct 12v bypass. if that works then what exact wires should I check on/to/from the relay if when I replace it there still isn't power?
just wondering as I want the car to be driveable so no one has to tow it away.
or if I hang on to it for a while, I need to be able to move it without hurting my back

quote Originally posted by gtxbullet: THREAD REVIVAL!!!! the 84 SE I'm selling doesn't run due to either a bad relay or fuel pump. the relay doesn't click on. so I'll try the direct 12v bypass. if that works then what exact wires should I check on/to/from the relay if when I replace it there still isn't power? just wondering as I want the car to be driveable so no one has to tow it away. or if I hang on to it for a while, I need to be able to move it without hurting my back

You are close to me. If you need help changing that pump let me know as I have done quite a few.

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I swapped my relays around, no luck, applied 12v directly no luck. Well it would come on for a minute then die again! VERY VERY Frustraiting! I finally discovered that if the 12v directly wont continue to work it must be a bad pump. I bought a pump but haven't installed it yet. Getting that tank out is a booger! I hope to do it on the morning of the 4th or between church times tomorrow. Most likely the 4th.

I just finished replacing my fuel pump just about an hour ago. Getting the pump swapped and replaced once the tank is out is a snap. It's getting the dang tank out and then back in by yourself under the jacked up car that is the real issue. There is barely enough room to try to get the hoses convinced to let go of the tank. Then you have all the other little lines getting in the way...frustrating. Your best bet is to get the car up as high as possible so you can get your hands into the tight spaces and get some leverage. Remove the fuel line retainer bolts on the filter hold down as well as to the supply lines to the passenger side. Push them up and out of the way to clear some space. Of course you have to remove the heat shielding (four 7 metric bolts, two of which you'll have to use a cresent wrench to get at 'em). Now you can remove the hose clamps and then the hoses (good luck...took some time!). Now there are four line clamps, two on each side of the tank ( 7 metric again) remove them. Then remove the heavy cross beam (4 13 metric bolts). You'll have two more bolts to remove from the drivers side of the tank. These are 13 metric too, but you'll need a deep socket to get at them. Now the tank should now be ready to drop out. You'll have to pull a little, depending on how much gas is in there. Now once the tank is out, use a flat head screw driver and a mallot to turn the retainer ring off the tank. You should now be able to swap out the pumps.

Okay, here comes the fun. Getting the tank back in! I raised my tank up off the ground with my creeper and started reconnecting the hoses with the third metal line first, then somehow forced the two large hoses back on the end of the tank. Make sure you thread the electrical line back through its hole above the filler hoses or you won't have enough slack to re-connect it later and it is very hard to find room to do this once the tank is back in place (ask me how I know...). Push the tank back into its home and connect the strap bolts back first, then the line clamps, then the cross bar. Next reconnect the rest of the lines and re-connect the fuel line brackets. Finally, put the heat shield back into position and screw in place.... Whala....new fuel pump. Took me about three hours over two days to do this. Mostly due to the tight spaces and extreme heat outside. Good luck!

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