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JFairman JFairman is offline
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Join Date: Jul 2006
Location: S. Florida
Posts: 7,274
Here's my yellow relay with the insides removed.

It may be the origonal one to my 1987 car.

I've spread the pins a little to try and make better contact in the relay socket.

I've taken a soldering iron and melted every solder point on both circuit boards to eliminate the possibility of a bad solder joint over a year ago when trying to figure out why my fuel pumps would shut off every now and then.

I've since found it was probably the speed relay contact pins not making good contact to the plug under the driver seat that was causing that. Lightly scraping the pins which already looked clean with a knife blade has stopped the intermittant fuel pump shutoff problem.

With a cheap digital ohmeter on the continuity setting and the red positive lead on 87a and the black negative lead on 86 it reads around 600. The polarity has to be that way or there is no continuity... probably one of the diodes on the board is causing the polarity thing.
Then if I push the double contact points on the relay apart the ohmeter reading goes to no continuity or nothing.
That makes me think pins 87a and 86 are the right ones to jump to get around a questionable or non working yellow relay.

You can see the dual contact points in this picture and at rest they are together making contact even though it looks like they are apart in this pic..

I took an old non working red fuel pump relay and gutted the insides of the burned out relay and diode and soldered a wire across the 87a and 86terminals and then glued the red cap back on.
I keep it in the glovebox as a yellow relay jumper now and it's in my car in place of the yellow relay at the moment.
The surprising thing is the overboost sensor white wire works with the jumper in place of the yellow relay the same as it does with the yellow relay installed. Ground the wire and the fuel pumps run. Disconnect it from ground like a new overboost sensor does around 1.3bar and the pumps shut off.

I remember the speed relay under the seat has a couple skinny white wires going to the plug that goes on it along with around 8-10 other wires.
The only skinny white wire I remember seeing in the car is the overboost sensor wire. It makes me wonder if the overboost sensor is actually connected to the speed relay with the yellow relay somehow associated with it and the main purpose of the yellow relay might be to shut off the fuel pumps when the air flow meter safety switch is closed like when the engine is off but the ignition is still on.

It's a mystery... I wonder if anyone really knows how all 4 fuel pump relays are wired together and work together.
I'm talking about the 2 red fuel pump relays on the back end of the front relay panel. One is for each fuel pump and the rearmost relay runs the rear fuel pump and WUR and AAV heater elements.
Then the speed relay/rev limiter under the driver seat and the yellow relay on the engine bay relay panel have to be plugged in for the fuel pumps to run too.
Old 06-11-2010, 03:29 PM
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