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Fuel Pumps Run with Ignition Sw On. Help

Both fuel pumps run when ignition is turned this is a new issue . Checked the contact switch at the metering plate. Switch is closed(continuity) when plate is in rest position. Switch opens when metering plate is depressed. To test pumps you remove the connection to allow both pumps to run without jumping the relays. Not sure how to read the electrical schematic. I have changed out relays with no change. What would cause to to happen? Not comfortable driving with the safety of pumps not shutting off in an accident. Probably because recently had a rear collision with my other car. Any ideas where to look?
Old 05-23-2018, 06:33 AM
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What year 930? Do you have a yellow overboost relay? If so, that's likely where your issue lies. Happened to me too. Resoldered the internal connectors that were loose and it fixed it. It could be just making poor contact in the plug too.
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1988 930 Venetian Blue
Old 05-23-2018, 06:56 AM
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Originally Posted by Jeff NJ View Post
What year 930? Do you have a yellow overboost relay? If so, that's likely where your issue lies. Happened to me too. Resoldered the internal connectors that were loose and it fixed it. It could be just making poor contact in the plug too.
1979 do not have yellow relay. Will check connection to safety contact. Thanks
Old 05-23-2018, 07:58 AM
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I jumped the plug to the contact sw and pumps run, but should not.

Last edited by Handyjay; 05-23-2018 at 08:20 AM.. Reason: Correct spelling
Old 05-23-2018, 08:12 AM
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Someone that is familiar with the circuit on a 79 will jump in here soon, I am sure. My experience with my 88 isn't going to help you since the circuits are different.
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Old 05-23-2018, 08:30 AM
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There is a relay in the engine compartment electronics panel for the air meter safety switch. If the circuit goes to ground the switch will be defeated, like it is unplugged. Check the daisy chain starting at the trunk fuse panel with the pump relays and follow it until you find the fault.
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Old 05-23-2018, 09:18 AM
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^^^ The air meter switch is the green plug on the back of the CIS next to the air plate. I was thinking the same thing could be the issue.
Maybe it became disconnected or the harness is shorted somewhere. I would start at the switch and work toward the relays. The engine harness gets brittle and IMO has an easier chance of shorting.
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Old 05-23-2018, 10:01 AM
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Ok thanks for the input. Found bad wires shorting from the contact switch down to the point where the CSV goes off and some wires go to the starter I think. There is still a short in the circuit somewhere as the pumps still run with the ignition on. The brown and black wire and brown wire do not look bad down to the junction, but must still be making contact somewhere. Where does the brown/black wire go and where does the brown wire go. Thinking I could just run new wire and bypass the short. Difficult to access the wiring with the engine in the car.
Old 05-23-2018, 12:40 PM
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Solid Brown is Ground on these cars.
The brown/black would be the signal wire. Follow it.
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Old 05-23-2018, 12:55 PM
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Derrick, short of dropping the engine any idea how to trace the brown or brown/black through all the electrical tape bound wires? I guess I could just run the brown to ground and just trace the signal Br/Bk. if I knew where it connects a bypass might be easier.

Last edited by Handyjay; 05-23-2018 at 01:35 PM.. Reason: additional info
Old 05-23-2018, 01:33 PM
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I'll need to look at the schematic. I would assume it runs around the back of the CIS to the right and into the main harness that goes across the shroud, by the fan, and to the large rectangle connector at the back of the rear fuse relay panel.
Unplug the harness at the panel and at the sensor connector. You should be able to check for a short between that wire and another pin. You may need to cut the tape back to expose the wire colors. Easy to retape when done.
If the engine harness is ok then you'll need to check further forward toward the relays.

Check to see if the sensor itself is bad too. I don't have the info on the sensor but it must be a trigger that grounds when closed. You will probably get a reading by opening and closing the air plate with your hand. If there is no change then its the sensor.
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Old 05-23-2018, 01:45 PM
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The contact sensor is closed in the non running or rest position and open when metering plate in depressed. The contact switch wire( brown and brown/black) were in contact due to deteriorated wiring from the switch to the cable junction behind the engine, therefore shorted or connected just as if connected to the contact switch. I connected ohm meter to the contact switch and had continuity with the metering plate in rest and no continuity when the plate was depressed. So I feel switch is OK. Need to trace the wire until I find the problem area or rewire the circuit. Hard to get to the wiring behind the engine.
Old 05-23-2018, 03:29 PM
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Going with a 1981 , which I'm sure is the same , yes the brown wire is the ground and connects to the alternator .The other wire should be pin #8 on the 14 pin engine connector . And your switch sounds good .Good luck .
Old 05-24-2018, 06:51 PM
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Greg, I'm still stuck. Here's what I know:
Contact Sw is closed at rest, open when plate is depressed. Assume sw is ok.
Found bad wiring from sw to wiring loom behind engine and replaced to where is appears to be ok.
Tested the Sw wire: Brn goes to ground. Brn/Blk does not, but has continuity to boost relay pin 85.
Both pumps run with key on regardless if the Sw wires are connected or not.
Pumps do not run if boost relay is removed.
Pressure limit Sw wire(white) has continuity to the 14 pin connector pin #4 female. I do not get continuity to ground on the male #4. The pressure limit Sw is closed unless excess pressure opens the circuit. What am I missing?????

Last edited by Handyjay; 05-25-2018 at 10:53 AM.. Reason: updated
Old 05-25-2018, 07:40 AM
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Check to hear if engine bay relay is working . Is the relay a red 5 pin ? Turn ignition on and pull the connector on the fuel head off and on . You should hear the relay click open , closed . Another one , remove relay . Pumps should not run , turn ignition on , jump #30 to #87a . Pumps should run .Good luck .
Old 05-26-2018, 12:12 AM
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A rewording . Remove engine bay relay . Turn on ignition , pumps should not run . Then jump ,
Old 05-26-2018, 12:18 AM
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Greg, appreciate you staying with me on this problem. I will check out the relay as suggested. Running out of ideas on what to do next. I found the wires to the contact switch were fused together. Obviously they got hot and shorted which but what could have caused this to happen? This all started when I was trouble shooting the rear wiper not working and found the contact pins on the switch broken off. I had the ignition on for some time and saw smoke from the engine compartment. What what would do this? The contact switch is only a on/off to ground right? Does this make any sense?
Old 05-26-2018, 05:08 AM
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If you are seeing smoke from the harness I would be removing it and all of the insulation. You really need to take it apart and inspect. You don't know what other wires are a part of the shorted area. It's a breakdown or fire waiting to happen.
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Old 05-26-2018, 06:13 AM
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Derrick, I agree. Will have to dig further.
Old 05-26-2018, 07:49 AM
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Having a time reading the wiring schematic and understanding how how all the bits connect in normal operation. I know if I unplug the contact SW the pumps should run. They run if the SW is plugged in or unplugged. With the plate depressed the meter switch opens so how does the boost relay function during run? I'm lost! Can someone explain this circuit so I can figure out where to dig into next. Hoping help from the forum brain trust. Thanks in advance...
Old 05-26-2018, 08:41 AM
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