Good double relay - no voltage to fuel pump.

[TrollFromDownBelow]

To provide some background, about 4 weeks ago, I had to pull the bus out of the garage to work on my DD. It was ~ 20 deg F, and had to jump start it due to cold, thick oil, and low battery. Four hours later had to throw jumpers on it again. Let it warm up for about 1 min, took the jumper cables off, and it was idling fine. About 60 seconds after removing the cables the bus dies very abruptly. Couldn't get it restarted, so pushed it back into the garage.

Finally had some time to work on it a few weeks ago. After fully trickle charging the battery overnight; plenty of juice; turns the engine over very well. Had my wife crank, and I put my test light across the coil, it was flashing, so pretty confident it's not an ignition issue.

I then put the key in the run position and moved the AFM lever over to the left so it would activate the double relay and the fuel pump.....I heard neither. I used both volt/ohm meter and my test light to check if there was any current getting to the double relay, and it appears that it isn't getting any.

I do have power coming into 88y and 88z (Colin's diagrams were very helpful!). I also checked per Bentley that I have power coming to terminal 88d when cranking, and 88b with ignition on, so that should mean the double relay is working. Also confirmed that the black wire with the fuse holder is connected to #15 on the coil.

I know it is a fuel delivery problem; fuel pump does not go on with ignition "on" and moving the AFM flap.

Have also confirmed there is no voltage going to the fuel pump in the same state as above, so most likely not a fuel pump (that, and I just replaced the pump about 5k ago....not impossible, just not likely the pump is bad).

I received my new double relay today, plugged it in, and it was a no-go. Assuming I need to check for physical connection/wiring issues at this point.

[skip]

I don't know, but check the resistor bank mounted on the firewall, mine had a broken connector that
I soldered. Because it was old I ordered a replacement. This is after I purchase a spare 7pin AFM
and double relay.

[SlowLane]

Hi Mike.

Sounds like you have done most of the signal tracing around the double relay. You say that you have voltage at 88D when cranking, so referencing Colin's excellent and beautiful Double Relay schematic, that means that the relay providing power to the pump is working.

So I would start by checking for voltage at terminal 88A on the double relay then move along the signal path to pin 39 on the AFM connector, then check pin 36 on the AFM, then check 86B at the double relay. It's simpler if you have the lid off of your AFM.

It's possible that one or more of the terminals in the AFM plug connector has receded so that it has lost contact, or that your AFM plug isn't fully seated. You do have the retaining bail wire on the plug, don't you?

Good luck

[TrollFromDownBelow]

Hi Mike.


It's possible that one or more of the terminals in the AFM plug connector has receded so that it has lost contact, or that your AFM plug isn't fully seated. You do have the retaining bail wire on the plug, don't you?

Good luck

Been working some crazy hours...finally have time today to play with it...retaining bail wire on the AFM plug? I don't believe mine ever had one.

[SlowLane]

Hi Mike.


It's possible that one or more of the terminals in the AFM plug connector has receded so that it has lost contact, or that your AFM plug isn't fully seated. You do have the retaining bail wire on the plug, don't you?

Good luck

Been working some crazy hours...finally have time today to play with it...retaining bail wire on the AFM plug? I don't believe mine ever had one.

Well, more like a wire clip, like the ones on the injector plugs.