I've replaced the pump and checked the tank side of the loom and all is well there. The tank is installed and has 3 gallons of gas and the loom connected but I dont have the 'key-on' pump actuation. I tried to crank the motor to get oil pressure but the battery couldnt take it so I used ether to get it to fire. It built 40 lbs of pressure with the 2 attempts but that also fails to get the pump to run. I need to know what to check to figure out why I'm not getting any power to the pump at all. Any suggestions?

ps - I forgot about terminal G in the ALDL... I'm going out now to test it. Still could use some ideas.

TIA
Steve

fuel pump relay?

I'm assuming so. Was able to actuate the pump via the ALDL/lighter jump, worked some air out and the motor fired and ran for about 5 minutes. I'm assuming the pump problem is found.

Now on to other things as it smells and looks like the 'choke' is stuck. Anyone care to help tackle the 'too much fuel' syndrome? This is in line with what the previous owner explained to me just before the pump died on them.

Helps to know what engine you've got. Have you checked fuel pressure with a guage? Tried running with the ECM coolant temp sensor disconnected?

JazzMan

quote Originally posted by FieroMojo: I'm assuming so. Was able to actuate the pump via the ALDL/lighter jump, worked some air out and the motor fired and ran for about 5 minutes. I'm assuming the pump problem is found. Now on to other things as it smells and looks like the 'choke' is stuck. Anyone care to help tackle the 'too much fuel' syndrome? This is in line with what the previous owner explained to me just before the pump died on them.

Four or six cylinder?

Sorry I was rattled and posted in a hurry. Its an 86Gt with a stock 2.8.

FWIW, I've got a similar problem.. My oil pressure switch will start the pump, although it has to get well over the halfway point on the gauge. If I unplug the FP relay, I get 12V to the relay from the ECM (for a long time, more than two seconds, anyway), but that drops to 0.7V as soon as I connect the wire (I dissassembled the relay connector) to the relay, i.e. as soon as I put any load on the wire, it doesn't have the juice to close the relay.

I tried plugging in another ECM ('91 4.3L) and turning the key on made the pump run for two seconds. I did not try to start it.

Someone on this board told me that a transistor the fuel circuit can burn out in the ECM, makes sense with the strange behavior. For now I have the pump hotwired to my cig. lighter and plan to replace the transistor on the board as soon as I get a little time. Easier said than done, I'm sure.

If you've tested everything else and have access to a spare ECM, try it out. This may solve the problem. Then again, there may be a reason the circuit died, and you might fry another ECM.

Hope this helps.

Its for that reason that I wish I could get my hands on a diagram of each individual circuit explaining the origin and destination of every wire involved, what the ideal condition would be when working properly and what to test for and in what mode, car running, key on, etc. Locations of various items would be a boon as well. I'm quite new to the computerized cars as I've not had a major problem with my vehicles in nearly 20 years. Guess its time to hit up the local community college and take mechanics courses and bone up on this stuff.

BTW - its running and doesnt appear to have the rich fuel problem now that I've gotten it warmed up and drove it around the parking lot. I replaced the relay but it didnt seem to make any difference in that circuit. It cranks until the oil guage is well in the red area and then fires up... looks like its still being controlled by the OP relay and not the FP relay. Cant hear the pump run as the fan is in constant-on mode as is the radio.

OK, next step is to put a voltmeter on the dark green wire on the relay when it's unplugged. Have someone turn on the key and watch the voltage, you should have 12VDC for 2 seconds or so and then the voltage should drop to nothing. That means the ECM is telling the pump to turn on. Mine stays at 12V all the time while the relay is unplugged but this is incorrect operation.

Next, tap into the dark green wire while the relay is plugged in and turn the key on and check the voltage - this is checking the circuit under load and is where my system fails. If you've got 12V, then check that the black wire is a constant ground and that the orange/black wire is constant 12V. If these all check out, then check out the tan/white wire leading from the relay to the fuel pump.

The way the relay works is: when power is applied to the dark green wire by the ECM and the black wire is grounded, the relay will close the circuit between the orange wire and the tan wire, sending power to the fuel pump.

You can check the relay's operation by putting power to one of the outer terminals on the top row of connectors (the row with three connectors) and ground to the other outer terminal. If the relay clicks, it's likely fine but you can check further by making sure there is continuity (0 ohms with the ohmmeter) across the remaining two terminals while the power and ground is on the terminals described above. It should be infinity without the power and ground described above. Relays sometimes fry themselves closed, so if the pump doesn't shut off, this could be the reason.

I hope this makes sense.. PM me if you want some clarification. Good luck!

Apply 12v to the fuel pump test terminal. If the pump runs, the pump is good. If not, there's a wiring or pump problem. If it runs this way but not for the 2 second prime when the key goes to RUN, the relay/wiring/ecm is bad.

JazzMan

Jazzman-we addresed this member's problem a few weeks ago and offered these suggestions at that time. I was concerned at that time he would still have a problem after changing the pump, since the wiring check at the loom was inconclusive. I'm pretty sure that the oil presure wire to the fuel pump connects at the FP relay on the output side, but it may be a direct tie in on the connector going to the fuel pump.
a couple of possibilities:
The ecm is not recieving an ign reference pulse during cranking, thereby failing to energize the fuel pump relay. This is usually caused by a bad ign module, or it's wiring going to the ecm.

Either the primary wire to the relay is not getting it's 12v from the fuse box at terminal 'D' on the relay, or the ground from terminal 'C' on the relay is not complete.

Terminal 'A' on the relay is not recieving a 12 v signal from the ecm.

quote Jazzman-we addresed this member's problem a few weeks ago and offered these suggestions at that time.

This is correct. After installing the new pump, I can get it to run from the ALDL but not from the FP relay. If I remember right, there was something amiss at that point but I'm not sure what it was as I basically shooting blind not knowing what I was checking.

quote Either the primary wire to the relay is not getting it's 12v from the fuse box at terminal 'D' on the relay, or the ground from terminal 'C' on the relay is not complete. Terminal 'A' on the relay is not recieving a 12 v signal from the ecm.

This clarifies what I should expect from these connections... now I have to figure out which terminals are what. I'm not sure if they're labled on the relay and the only reference I have is the Haynes manual which is primarily written for the 4 cyl. engine.

quote The ecm is not recieving an ign reference pulse during cranking, thereby failing to energize the fuel pump relay. This is usually caused by a bad ign module, or it's wiring going to the ecm.

Are these scenarios the only ones or is there maybe something else? I can get the engine to fire and remain running if I crank until the OP relay kicks in and that happens fairly quick... about 2 to 3 seconds of cranking time. If I mimmic the FP relay function via terminal G on the ALDL it fires instantly and remains running. Its my assumption that the trouble lies with the FP relay wiring as I have replaced the old FP relay and it didnt seem to help matters any. I'm not sure if the reference pulse is used only for this purpose or if its shared by other functions of the ECM. If it is shared then I assume the FP relay wiring or that function in the ECM is faulty as I don't see any other problem with the engine's opperation once running, which would mean that the reference pulse is being sent and seen by these 'shared' functions. Does anyone concur on this?

Thanx again,
Steve

Maryjane - yes, the OP switch connects to the output side of the relay. When the car is running (using the OP switch to turn on the FP) the tan/white wire will have power at all points: relay, pump, ALDL G, etc.

The dk. green wire runs from the relay, directly to the left firewall connector and into the ECM..

You mention that possibly the ECM isn't receiving a reference pulse.. IMHO, the problem is deeper than that - if the ECM is not putting out 12V on the dk. green wire when the key is turned on, then there's an issue in there. That same circuit is used by the ECM to turn on the fuel pump when it's running, so regardless of a reference pulse, the ECM cannot energize that circuit.

Just my two cents, I'm fighting with the same problem right now.

To clarify what I stated... Its my assumption that, if there was no reference pulse coming from the ign. mod., the engine wouldnt run at all as it would affect other parameters within the ECM. As the engine runs fine throughout the RPM range, I'm doubting the problem is there... unless that reference pulse is used solely for the initial starting sequence. In that case, the problem could rest there. That is what I'd like to discover. Any thoughts?

Thanx to all,
Steve

quote Originally posted by FieroMojo: now I have to figure out which terminals are what. I'm not sure if they're labled on the relay and the only reference I have is the Haynes manual which is primarily written for the 4 cyl. engine.

The relay should be the same for 4-cyls, but I'm not sure. The terminals are labelled on the connector (maybe on the relay itself, can't remember) but I used the colors rather than the terminal designation because that's easier for me. Either will get you where you want to go.

[This message has been edited by Stinkin_V8 (edited 09-19-2003).]

Thanx... just what I was looking for. This is the same diagram that was posted before except its now in its entirety. I saved the link in my favorites for future reference. Now to begin to troubleshoot

Thanks again to all,
Steve