No power to fuel pump, seems to be a common problem around here Options

[warrenoliver]

Car stalled on me this morning. When I tried to restart, the fuel pump would not turn on so no luck with the start. Towed it home and checked it out. It is a 73 2.0 with FI.

The pump runs when I jumper directly to the battery. I have continuity from pump connector to the #13 pin on the relay board. If I jumper from the fuse to the #13 pin, the pump comes on. The fuse is good.

I have replaced the main power relay and the fuel pump relay with known good ones. With the ignition on, when I remove and reseat the main power relay, I can feel the relay click but I do not hear the injectors click nor do I hear the fuel pump start (I got this test from Dr. 914's Tech Tips).

On the fuel pump relay socket, I have power at the 30 pin and also the 85 pin. When I jumper to the 87, it does not turn on the fuel pump.

I don't know if it is related, but I have the same problem with the heater blower relay also. I jumpered 30 to 87 and I do not have power. I am not sure but I think the car died when I had the heater blower running.

I'm stumped. What do I check next?

[Tom]

Jumpering pin 87 of the fuel pump relay is the same as jumpering pin 13 of the 14 pin connector to power. You say pin 13 to power makes the fuel pump work. Try jumpering the fuse to pin 87 of FP relay. Pump should come on. If not, you have a problem with the fuel pump relay socket to relay board traces. Try cleaning the fuel pump socket with a small wire brush or rolled up fine sandpaper.
Here is a different pic of the relay board.
Tom

[Jon H.]

Do you still hear the clicking coming from the TPS when you have the ignition in the run position and you move the TPS by hand? If not then your ECU might not be getting power which controls the ground on the fuel pump relay. Or the grounds for the ECU might need to be cleaned. I just had this happen on my 73' 2.0l. It ended up being a poor connection at the molex connecter on the power board.

Jon

[warrenoliver]

Tom,

When I jumper from the fuse to 87 of the fuel pump relay, the pump comes on. That really makes no sense to me since the 30 pin for that relay also has 12V but when i jumper from 30 to 87 - no joy. What gives?

Jumpering pin 87 of the fuel pump relay is the same as jumpering pin 13 of the 14 pin connector to power. You say pin 13 to power makes the fuel pump work. Try jumpering the fuse to pin 87 of FP relay. Pump should come on. If not, you have a problem with the fuel pump relay socket to relay board traces. Try cleaning the fuel pump socket with a small wire brush or rolled up fine sandpaper.
Here is a different pic of the relay board.
Tom

[Cap'n Krusty]

Install the 2 headlight motor relays in the FI control and fuel pump relay positions and see what happens.

The Cap'n

[warrenoliver]

I tested the heater fan circuit also. The fan runs when I jumper from the fuse to the 87 pin. It does not run when I jumper from the heater fan 30 pin to 87. Both the heater fan blower and the fuel pump relays get their power from the power supply relay (I think), but it still doesn't make sense why I can't get either one to turn on from the 30 pin of their respective relay.

[76-914]

. Here ya go http://members.rennlist.com/pbanders/FPChecklist_frame.htm

[warrenoliver]

I spread the pins on the relays and cleaned the contacts. When I jumper from the 30 pin of the power relay to the 87 pin of the fuel pump relay, the pump runs. Seems to be something between those two relays.

I don't really know where the white wires in the molex connector go but I assume they go to the ECU. I looked at the ECU and it looks like the wiring harness is hardwired into the ECU so I don't know if those wires go into it.

When I ground pin III on the relay board, the pump does not turn on.

I am stumped. I have an AX tomorrow that I would like to go to so I hope someone can help.

[Dave_Darling]

Both the heater fan blower and the fuel pump relays get their power from the power supply relay (I think)...

Your thought about the fan and pump relays being powered from the "power supply" relay matches the diagram above, so it should be correct.

... but it still doesn't make sense why I can't get either one to turn on from the 30 pin of their respective relay.

It makes sense to me. A relay is just a switch that is flipped electrically. What these do is connect pin #30 to pin #87a by default. When current passes through the coil (i.e., when you have +12V at either #85 or #86 and you have ground at the other) it flips to connect #30 to #87. That's how it supplies power; it takes whatever it is getting at 30 and connects it to 87.

So, jumper from the fuse to #87 of the power relay socket. You should now have +12V at #30 of the blower and pump relays. If those operate normally at that point, you have a good idea that the power supply relay is at fault.



....Of course, you could follow the Cap'n's advice and swap those relays for the headlight relays. That puts different relays in, and turning on the headlights will also check the relays you just swapped into them...

--DD

[warrenoliver]

I tried that previously but I just tried it again and no joy.

Install the 2 headlight motor relays in the FI control and fuel pump relay positions and see what happens.

The Cap'n

[warrenoliver]

Thanks Dave,
The relays are good. When i have the power supply relay in, and the key on, I have power to fuel pump relay 30. When I jumper from that fuel pump relay 30 to the fuel pump relay 87 i do not get the pump to turn on. If I jump from the fuse to the 87 of the fuel pump relay, the pump turns on. The problem is that i don't know what that means.

Both the heater fan blower and the fuel pump relays get their power from the power supply relay (I think)...

Your thought about the fan and pump relays being powered from the "power supply" relay matches the diagram above, so it should be correct.

... but it still doesn't make sense why I can't get either one to turn on from the 30 pin of their respective relay.

It makes sense to me. A relay is just a switch that is flipped electrically. What these do is connect pin #30 to pin #87a by default. When current passes through the coil (i.e., when you have +12V at either #85 or #86 and you have ground at the other) it flips to connect #30 to #87. That's how it supplies power; it takes whatever it is getting at 30 and connects it to 87.

So, jumper from the fuse to #87 of the power relay socket. You should now have +12V at #30 of the blower and pump relays. If those operate normally at that point, you have a good idea that the power supply relay is at fault.



....Of course, you could follow the Cap'n's advice and swap those relays for the headlight relays. That puts different relays in, and turning on the headlights will also check the relays you just swapped into them...

--DD

[warrenoliver]

Thanks for the Anders troubleshooting tips. When i follow his guide, it instructs me to "remove the ECU from bracket and remove wiring harness plug" - I don't see a plug, the wiring harness goes directly into the ECU. Do I have to open the case of the ECU?

. Here ya go http://members.rennlist.com/pbanders/FPChecklist_frame.htm

[Bob L.]

Thanks for the Anders troubleshooting tips. When i follow his guide, it instructs me to "remove the ECU from bracket and remove wiring harness plug" - I don't see a plug, the wiring harness goes directly into the ECU. Do I have to open the case of the ECU?

. Here ya go http://members.rennlist.com/pbanders/FPChecklist_frame.htm

There's a clamp that holds the harness at the corner of the ECU where the wires go in.


Loosen it and slide the plastic cover off.


You will then be able to grab the plastic handle and unplug the harness from the ECU. Carefully pull it straight out.

[warrenoliver]

OMG, thanks Dave for the pictures. Without those, if i had opened the ECU and seen that mess, i would have closed it up! I will have to get after it this afternoon.

Thanks again.

[Bob L.]

OMG, thanks Dave for the pictures. Without those, if i had opened the ECU and seen that mess, i would have closed it up! I will have to get after it this afternoon.

Thanks again.

You're welcome.


BTW, I'm Bob. (IMG:style_emoticons/default/bye1.gif)

[warrenoliver]

Oops, sorry! Thanks Bob.

You're welcome.


BTW, I'm Bob. (IMG:style_emoticons/default/bye1.gif)

[Tom]

Warren,
Sorry to not answer back sooner. I have been dealing with the loss of my 16 year old puppy. It is hard when a pet you have had for so long passes.
For some reason you are not getting current flow thru the pin 30 connection on the fuel pump relay socket. It could be corrosion in the socket or corrosion where the #30 pin connects to the traces on the relay board.
Most folks assume that if there is 12 volts there when they test, then the equipment should work. Voltage is potential, current is power. Dirty or corroded connections may give a voltage reading, however when current is needed to run the equipment, the connection will not supply the necessary current. You can think of it like this: a 1/4 inch hose will give a reading of 50 PSI, so will a 5 inch hose. The 5 inch hose will flow a heck of a lot more water than a 1/4 inch. Think of the 5 inch hose as a good clean connection and the 1/4 inch as a dirty/corroded one. They both may give you a voltmeter reading of 12 volts, only one will give the current necessary to power the equipment.
Here is what I would check given your tests and results; check the sockets and relay prongs of the power relay and the fuel pump relay to make sure they are clean and make tight connections. You can spread the relay prongs slightly with a small knife to try to ensure they make good tight connections with the relay sockets. The sockets can be cleaned with a small bit of sandpaper rolled up to fit in the socket, or a small wire brush will clean the sockets also. It sounds if your relays are working, so concentrate on the prongs and sockets to see if you can get good connections.
Hope this helps,
Tom

[warrenoliver]

Tom,

I think you may be right but I just don't know. I am hesitant to tear into the ECU and make more problems. I have already spread the prongs slightly and have tried to clean the sockets but I will try to do some more to see if I can make some sense of it.

Thanks.

[Tom]

Warren,
From what you have said, it doesn't sound like an ECU problem.
Also powered at the same time as the fuel pump is the AAR, which has a noted problem of shorting and draining power. Try disconnecting it and see if things work better. You can by-pass the ECU function by providing a ground to the fuel pump relay by jumpering a ground to pin #3 of the 4 pin connector that goes to the ECU. This will energize the fuel pump relay anytime the key switch is on.
If all else fails, you can run your auto-x tomorrow by jumpering the fuel pump relay, jumper fuse 13, the rear most fuse, to the pin #13 of the 14 pin connector. Just remember that the fuel pump will continue to run anytime the key switch is on, even if the engine has stopped.
Tom

[Jon H.]

Don't forget, he is also not hearing the injectors click. If both the fuel pump and the injectors are affected then there is an issue with either the ECU or the power supply to the ECU. Do you hear the clicking from the TPS when you move the throttle by hand when the key is in the run position?

Jon