Fuel injection pump always running - 1979 Super

[dpothomsonvw]

I am rebuilding my 1979 SuperBeetle and I have a problem with the fuel pump. The pump runs even when the key is off. I did all of the tests on the double relay and I found that terminal 88d has power to it all the time. When I unplug the opposite side which goes to the ECU and air flow meter, there is no power to terminal 88d. I checked the air meter and it passed all of the ohm ranges. Does anyone know why 88d would be powered all the time?

Also on the double relay, should there be continuity between 88y and 88d while static (unplugged)?

thanks

[Amskeptic]

I am rebuilding my 1979 SuperBeetle and I have a problem with the fuel pump. The pump runs even when the key is off. I did all of the tests on the double relay and I found that terminal 88d has power to it all the time. When I unplug the opposite side which goes to the ECU and air flow meter, there is no power to terminal 88d. I checked the air meter and it passed all of the ohm ranges. Does anyone know why 88d would be powered all the time?

Also on the double relay, should there be continuity between 88y and 88d while static (unplugged)?

thanks

Read this:

http://itinerant-air-cooled.com/viewtop ... =50&t=5459

I can clarify later.
Colin

[dpothomsonvw]

Thanks Colin. I did read all about the relay. Great post by the way. But I was not sure if 88d should have continuity with 88y while unplugged. If there is continuity while static, it could explain the reason why I have power to the pump all the time, therefore a bad relay (although it is brand new).

Any other suggestions?

[SlowLane]

Thanks Colin. I did read all about the relay. Great post by the way. But I was not sure if 88d should have continuity with 88y while unplugged. If there is continuity while static, it could explain the reason why I have power to the pump all the time, therefore a bad relay (although it is brand new).

I think youve nailed it.

Looking at the Beetle Bentley, 88y should have +12V under all conditions: it's wired directly to the battery's positive terminal.

There should not be continuity between 88y and 88d when the relay is not energized.

[dpothomsonvw]

Problem still there. I have been chasing wires all night. I have power to terminal 88c on the FI side all the time as well as 88d. At one point, the power was gone to 88d and the fuel pump stopped running. I cranked the engine and the motor ran for a short time, but when I turned it off the fuel pump kept running. The relay got really hot. Could I have problem with the ECU? Is there a way to test it? Any other suggestions?

Thanks

[SlowLane]

Problem still there. I have been chasing wires all night. I have power to terminal 88c on the FI side all the time as well as 88d. At one point, the power was gone to 88d and the fuel pump stopped running. I cranked the engine and the motor ran for a short time, but when I turned it off the fuel pump kept running. The relay got really hot. Could I have problem with the ECU? Is there a way to test it? Any other suggestions?

88c and 88d are hard-wired to one another inside the double relay.

If there is continuity between 88y and 88d with the relay out of the car and just sitting on the bench, that relay is BAD. Stop using it! Take it apart and see what went wrong, or if it's brand-new, take it back to the vendor and throw it at him.

With the relay out of the car, check and see if you have 12V at any of the "86" terminals with the ignition off. It is the several 86 terminals which energize the relay under various conditions. None of them should have power when the ignition is off.

[dpothomsonvw]

Ok. The relay disconnected and ignition unplugged, I have power at the 88c and 86b on the FI (white wires) side. I took the relay apart to see what was going on inside. It is working properly. When I unplug the AAR, 88c no longer has power.

[SlowLane]

Ok. The relay disconnected and ignition unplugged, I have power at the 88c and 86b on the FI (white wires) side. When I unplug the AAR, 88c no longer has power.

That isn't good. It does sound like an ECU issue, or a short somewhere in the harness. Power shoudn't be coming from the ECU on those wires.

As tedious as it is, you need to eliminate the harness as a suspect before deciding that it is the ECU. If you determine that the harness is the culprit, then 1) you may be able to avoid buying a replacement ECU needlessly, and 2) you may avoid wrecking a new replacement ECU by plugging it into a damaged harness.

I took the relay apart to see what was going on inside. It is working properly.

I'm confused. Initially you said that you had continuity between 88y and 88d. Is this still the case, with the relay sitting on the bench, no power applied to it?

[dpothomsonvw]

Sorry for the confusion. I asked if there should be continuity without checking first. I checked and there is no continuity. I checked the ECU plug and found that there are 3 terminals on the plug that have power with the ignition off. I traced these wires to the the white wires connected to alternator, which makes sense since they are on the same post as the direct battery wire on the alternator. When plugged into the ECU, 4 terminals all going to the injectors have power as well as the 6 and 9 terminals on the air intake sensor.

[Amskeptic]

Thanks Colin. I did read all about the relay. Great post by the way. But I was not sure if 88d should have continuity with 88y while unplugged. If there is continuity while static, it could explain the reason why I have power to the pump all the time, therefore a bad relay (although it is brand new).

Any other suggestions?

Unplugged? No continuity is allowed from 88y to 88d(c).
New? Means nothing in today's crap world.
BUT!
You must make sure that the control circuit, 86/85 is not being erroneously activated. If you hear a click everytime you try to plug in the relay, it is being energized. You may have to search for melted wires inside of harnesses . . .

[Amskeptic]

Sorry for the confusion. I asked if there should be continuity without checking first. I checked and there is no continuity. I checked the ECU plug and found that there are 3 terminals on the plug that have power with the ignition off. I traced these wires to the the white wires connected to alternator, which makes sense since they are on the same post as the direct battery wire on the alternator. When plugged into the ECU, 4 terminals all going to the injectors have power as well as the 6 and 9 terminals on the air intake sensor.

I am getting violently confused. why are we chasing around the ECU plug? The four terminals from the ECU to the injectors better damn well NOT have power. The injectors get their power directly from the ignition side and are GROUNDED through the ECU. This is critical. What on Earth is the alternator doing in this discussion? VW absolutely demanded that the fuel injection be released from any association with the entire electrical system when you shut off the ignition.

Step back.
Find your symptom > fuel pump runs without consent.
Go directly to the circuit(s) responsible.
Colin

[Amskeptic]

Problem still there. I have been chasing wires all night. I have power to terminal 88c on the FI side all the time as well as 88d. The relay got really hot. Could I have problem with the ECU? Is there a way to test it? Any other suggestions?

Thanks

Stay away from the ECU! Don't just go there. Don't flail and cast about. Look at the diagrams mentioned! Right there, you SEE that 88c and 88d are internally connected to each other, as goes one so goes the other.

Take the double relay out. Ohm out each terminal on the plugs to their destinations with the battery disconnected!

Reconnect battery. With the double relay still out, check for 12 volts at the hot terminals.
Now turn on the ignition. You should also have 12 volts waiting at 86c.

The article gives you a step-by-step pictorial representation of exactly how electricity flows through the relay at different operational points. You have a fuel pump running with the ignition off??
You desperately need to track this down carefully with an expert's help.
Colin

[dpothomsonvw]

Ok. I will go back and double check, but here is what I have done so far. I started at the fuel pump and chased the red/blue wire to terminal 88d on the DR. With the ignition off (relay plugged in), 88d had power as well as 88y. I know 88y should be powered because it comes directly from the battery. Since 88c and 88d are connected 88c has power too. As the diagram shows, 88c goes to the AAR. I unplugged the AAR which cut the power to 88c. I then chased the hot wire from the AAR plug to the ECU. That's when I checked the ECU plug (unplugged) to find power at the terminals where the 3 white wires on the alternator go. I used an ohm meter to follow the wires. When I plugged the ECU plug back in (cover off), I found power at the 3 terminals and at the 4 injector terminals and at the 6 and 9 terminals on the AIS. This is all with the ignition off. To make sure it wasn't as simple as a switch., I unplugged the ignition switch. The kicker is that 1 time I checked the 88d and there was no power. I thought problem solved. I tried to start the car, turned the key on, the pump ran for a second, cranked it over the pump ran again, the motor srtarted for a second with a ittle help of a squirt of fuel in the AIS, the motor quit, I turned off the key and the fuel pump kept running. I checked 88d again and once again it had power. I am at a loss.

[SlowLane]

That's when I checked the ECU plug (unplugged) to find power at the terminals where the 3 white wires on the alternator go. I used an ohm meter to follow the wires. When I plugged the ECU plug back in (cover off), I found power at the 3 terminals and at the 4 injector terminals and at the 6 and 9 terminals on the AIS. This is all with the ignition off.

Could you elaborate a little more on these "three white wires on the alternator"? Like which pins they connect to on which device at the other end?
I'm wondering if you maybe have the FI harness ground connections connected to the +12V side of your alternator somehow.

Also check for continuity between pins 36 & 39 on the AFM (AIS) with nothing connected to it. There should be an open circuit unless the flap is open. Flap closed = open circuit; flap open = closed circuit.

Also see this link: http://www.vaglinks.com/Docs/VW/Misc/VW ... Manual.pdf

[dpothomsonvw]

Ther are 3 white wires. 1 is a single connection and the other 2 are together. All 3 are connected to the only threaded post on my alternator. There is also a red battery wire on the same post. When I check for power, all 3 white wires are hot with the ignition off. The other post on the alternator is a spade connector that has the green wire. I assume that is the idiot light for the dash. I will check the continuity when I get home this afternoon and get back to you. I really appreciate your efforts in helping me solve this issue.