I have been going around with the problems of the fuel pump relay and would like to know how the internal relay (A) actually gets the ground to pull in. The other internal relay (B) has a hard wire ground and gets the +12 from the IGN SW in RUN or START position.
I have looked estensively at the Wiring Diagram in Bentley and still can't find the so called 31b connection.
Is it thru the ignition switching circuit on the low side of the Ignition coil, and the associated pick up unit in the distributor?

This might be too long to post, so I'd like to hear via email is that's better.
rjstulsa@aol.com
Thanks Bob

Bob,
Your 86 is different than some of the other descriptions in the other replies. The 31b reference in a fuel pump relay is for K-jet and somehow remains part of the schematic in Bentley's copy of the wiring diagram -- I figure it is there for some application I don't see here in US.

Yours has the white relay box with two relays inside. The main relay half goes on with the ignition key and off about 5 seconds after the key is turned off, controlled by the ECU, not the ignition computer, but the fuel computer. The fuel pump half gets its ground return through the ECU when it senses ignition pulses recurring at ECU pin 1.

Look on the schematic where the ECU is drawn. That is where you'll find the correct wiring for your fuel pump relay, not up by the starter and distributor.

Good luck,
--
Art Benstein near Baltimore

I stand corrected.

On my 93, a blue/green wire from the relay goes to the ECU wherein it gets grounded when the ECU receives a tach signal from the coil that the engine is moving. A common failure of the 561 ECUs is with this internal circuit. A common workaround is to cut this blue/green wire and ground it to the body, thus causing the fuel pump to run whenever the key is on. Not a good idea, since this circuit was designed to shut down the fuel pump when the engine is off or not cranking to prevent a fire in the event of a crash.

You are right. The ground source for the fuel pump relay is supplied by the ignition control module. This is the same source that energizes and breaks the field on the coil (many times per second) to provide spark for the plugs. If this ground source is not functioning, you probably have a broken or loose wire between the distributor and ignition module, problems in the distributor sensor, or a faulty ignition module. If the fuel pump relay pulls in while cranking you should have spark from the coil. I guess it's a safety thing.

At least on my 93, the ground is made inside the ECU, not the ignition control module.

Your 93 doesn't have a ignition control module, the 86 does.

What do you think that box is above the ECU?

ER... my 85 does.

Please excuse my previous post. I thought we were talking grounds. My Green book shows 31b going directly to the coil neg. terminal and then to pin 16 on ignition module.

just compared the bentleys w/the volvo green book......seems there are a few schematic diffs...the 31b pin in bentley, ( i think) is the the 86/2 pin in volvo...it shows a BL/GN wire going to pin 17 of the computer......is that what you're seeing?.......the volvo book doesn't show any direct connection w/ the dist...hope this helps.............j.

(like so many folks, i spent a week in tulsa one night..)

Do you mean there is no wire comming out of pin 31b in the relay socket? Most of the grounds in the dash connect to the chassis by a ring lug under a screw in the dash frame.