I had a look everywhere here on the forum, google etc. All kinds of info on Fuel pump relays. But nowhere can I find how to test this Fiero V6 Fuel Pump Relay for proper functioning. Normally a relay has a schematic embossed on there so you can test. The one that is in the engine compartment on the firewall driver side next to the A/C relay does not have that. I have a 12v source and a multi meter.... Does anybody know how to test it?
------------------ Job 86 Fiero GT 2.8 V6 with Lambo Countach body
Follow the power. The ECM closes the relay for 3 seconds when key is turned on to prime/pressurize fuel system. The once engine is running, the ECM receives a reference signal from distributor and then keeps replay closed. The oil pressure switch is a backup in case relay fails. It provides power to fuel pump once oil pressure builds up during cranking (and running).
An easy place to start is to look for battery voltage on the Tan/White wire in the ALDL connector. That is the wire from the relay to the fuel pump .The ALDL connector is behind the cigarette lighter plate.
An easy place to start is to look for battery voltage on the Tan/White wire in the ALDL connector. That is the wire from the relay to the fuel pump.
Interesting. I've used that terminal many times, but not in that manner. If I've wanted to test a non-functioning fuel pump, I've applied 12v to that terminal to bypass the fuel pump relay.
The relay energizes that wire, also. So if the fuel pump relay is working, that wire should have 12VDC any time the fuel pump is supposed to be running.
The schematic is posted above. But just to be thorough, here's a testing procedure you can use.
- Make sure the black wire has a good ground - Apply 12V to the green/white wire. The relay should click (if it has a good ground) - Make sure the orange / black wire has power (hot at all times) - Check for power on the beige/white wire when you turn the key
Side note: I've also seen the relay sockets deteriorate, and make it seem like the relay is bad.
[This message has been edited by Blacktree (edited 08-14-2020).]
Interesting. I've used that terminal many times, but not in that manner. If I've wanted to test a non-functioning fuel pump, I've applied 12v to that terminal to bypass the fuel pump relay.
It's also handy when you need to empty the fuel tank (if pump works)
It's also handy when you need to empty the fuel tank (if pump works)
Of course, the need to empty the tank is usually to lessen its weight prior to dropping it... to investigate why a fuel pump isn't pumping. Yeah, been there done that.
Of course, the need to empty the tank is usually to lessen its weight prior to dropping it... to investigate why a fuel pump isn't pumping. Yeah, been there done that.
But handy to know about the ALDL fuel pump connection...
There are people driving around with a bad fuel pump relay and don't know it. Their only complaint is, "I have to crank for half minute or longer before it starts". It's the Oil Pressure Sender powering up the fuel pump once oil pressure has built up from cranking engine.
Now... if their Oil Pressure Sender ALSO fails, they are hooped because the fuel pump isn't getting power from anywhere. Unless they know they can "hotwire" the fuel pump through the ALDL port to power it up.
My prime circuit was not working, causing me to get the il pressure up, so that the fuel relay would power the fuel pump. So, I cut the green/white stripe wire coming from the ECM, and spliced it between a 12 VDC power source (keyed), and a toggle switch to power the pump at first start-up.
Two days ago, October 15, the toggle switch circuit stopped working.
Troubleshooting:
I jumped the wires for the fuel pump at the OBT port, and the pump did not activate. I checked the fuse (Fuse position 2, 10A), fuse okay I removed the fuel relay and attached an electrical load - lamp-using the brown striped fuel pump wire and green/white wire at the fuel relay plug to test 12VDC at the plug. With my switch, I confirmed 12 VDC at the fuel relay plug.
I purchased new fuel relay and put it in, and neither of the new relays activated the fuel pump. The fuel pump will no longer activate with the switch. I confirmed that the switched circuit is sending 12 VDC to the fuel relay plug. Does anyone know what my problem?
New relays, no fuel pump. The engine will still start and run using the oil pressure switch.
When I got the car (1988 Fiero 2.5 w/19k miles), it always started hard. It would crank at least 10 seconds before starting, then run fine.
I remember when I owned a 1984 with a 2.5 when I graduated back in 1989, it started with what seemed like barely tap the ignition key.
Anyway, this 1988 Fiero I have was running in my driveway, then after about 15 minutes or so, just died out. It would not start again. Plenty of gas in the tank.
I started throwing parts at it because I just wanted to get this going. No luck.
I replaced the Fuel injector at the throttle body carb. Replaced the Oil Pressure Switch under the Ignition coil pack area (1988 no distributor). Replaced the fuel regulator (although the old one looked fine). Replaced the Throttle Position Sensor (TPS) at the throttle body. Replaced the Idle Air Control Valve (IAC).
I jumper the ALDL port pin behind the cigarette lighter, and I can hear the pump run, but it won’t start by doing this.
If you spill some gasoline into the throttle body, it starts and runs until it runs out…. It runs maybe like 5-8 seconds or so.
Also, once running by spilling some gas into the top of the throttle body carb….. if you steadily keep pumping the gas pedal, the Fiero will stay running… but very badly. … not drivable but runs (if you qualify that as running). It will sputter and feel like the ignition misses badly, sometimes it pops, and the instant you stop pumping the gas pedal, it will die out … and won’t start again
I’m thinking it’s a bad Fuel Pump or maybe even a Bad ECM computer (where you need to pull the center console to get at it behind the firewall).
I have not checked fuel pressure yet… was hoping something would have worked. I will need to buy a fuel pressure set to get this information.
Other than that, I’m stumped
Any suggestions?
I am really hoping I don’t have to drop the gas tank and replace the fuel pump, but I’m running out of things to try.
I jumper the ALDL port pin behind the cigarette lighter, and I can hear the pump run, but it won’t start by doing this.
Hearing the fuel pump running doesn't mean there's necessarily any fuel pressure. The fuel filter could possibly be plugged... but more than likely the flexible "rubber" hose inside the tank has rotted and ruptured.
Check if you have fuel pressure, but I suspect the tank will need to be dropped.
Hearing the fuel pump running doesn't mean there's necessarily any fuel pressure. The fuel filter could possibly be plugged... but more than likely the flexible "rubber" hose inside the tank has rotted and ruptured.
Check if you have fuel pressure, but I suspect the tank will need to be dropped.
I’ll replace the fuel filter just in case. I was thinking I had done that, but reading your reply got me really thinking that maybe I didn’t. I just don’t remember changing the fuel filter. Hmm… maybe I didn’t because I need to lift the car to get to it under the passenger rear area.
I’m definitely going to change it, but I’m already mentally getting myself up to having to drop the tank.
I didn’t even think of the rubber hose rotting or being ruptured.
Thank you This does help because it’s a virtual another set of eyes.
Yeah, been there done that. 
