Ok, this is just getting too wierd. I got a chance to go out and monkey
with the fuel pump relay a bit. I hooked up a multimeter and tested the
connections. The relay pins are arranged something like this:
1 2
__ _
|
3 |
|
------
4
the long pins 3 & 4 at the left and bottom are the ones that I was
connecting with a jumper to run the car. They go to battery positive and
the fuel pump circuit. They appear to be working properly. The other two
pins, the wide (1) and thin (2) pins, supply the power to switch the
relay.
I measured and found by toggling the ignition that the wide pin was
connected to ignition +12v, it would be hot with the key on and open with
the key off.
The other one was open with the car off, and when I turned the key on, it
would be connected to ignition +12v for about 1 second (the same amount of
time the fuel pump usually runs to prime the fuel system). What the hell!?
According to bentley it should be connected to ground for about 1 second.
How does something like this get mixed up?
Now I know what the problem is: because both contacts are connected to
+12v ignition, the potential difference between them is zero, and the
relay doesn't close.
I bought a new fuel pump relay ($14) and as I suspected it didn't change
anything. I tried to remove the fuse panel but the wiring harnesses were
so short I didn't want to do anything I couldn't undo quickly, like pull
off a bunch of connectors I couldn't see.
I can't think of any reason why the ECU would suddenly switch from
supplying a ground pulse to a +12v ignition pulse to power the relay while
I was driving down the road and cause the car to stall.
So, I'm completely dazed. Does anyone have any ideas about this at all?
Thanks
-Toby
--
'87 16v
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