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No power to 92 240 wagon fuel pumps

H

haroldburbank

Member
Joined
Jul 6, 2024
Hello. Had total fuel system failure after hitting a small highway bump at 65 mph. Then no start. Pumps did not prime as they should (hum) with key on 1 click. Towed home. Replaced ECM. No start. Fuel pump relay on order. Does the 92 have 25 amp fuel pumps fuse under hood next to coil? Pulled a black relay looking box next to coil. Four pin (not blade) male connector plug on box. Dimensions 1.25 inches long and wide, .75 inches thick. Does this serve fuel pumps? All under dash fuses good. ECM replaced (spare in my shop) since check engine light on before fuel failure with code for 02 sensor replaced months ago. Note bulb failure relay overheated months ago and replaced so a ground issue may lurk since the fuel pumps failed after a slight road bump. Comments? Thanks Harold Burbank. Canton CT
 
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haroldburbank said:
Hello. Had total fuel system failure after hitting a small highway bump at 65 mph. Then no start. Pumps did not prime as they should (hum) with key on 1 click. Towed home. Replaced ECM. No start. Fuel pump relay on order. Does the 92 have 25 amp fuel pumps fuse under hood next to coil? Pulled a black relay looking box next to coil. Four pin (not blade) male connector plug on box. Dimensions 1.25 inches long and wide, .75 inches thick. Does this serve fuel pumps? All under dash fuses good. ECM replaced (spare in my shop) since check engine light on before fuel failure with code for 02 sensor replaced months ago. Note bulb failure relay overheated months ago and replaced so a ground issue may lurk since the fuel pumps failed after a slight road bump. Comments? Thanks Harold Burbank. Canton CT
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More reading suggests the black box is an AC pressure relay or radiator fan relay. Fuel pumps not affected. Earlier cars had an engine bay 25 amp fuel pump fuse mounted next to coil on drivers side fender wall.
 
Your fuel pump relay is under the passenger side near the EZK ignition box on the firewall. You should see it after you remove the underdash cover. It's a white six pin relay. Use a test light on terminal 87 large red/yellow wire and see if it powers up on cranking. If it doesn't then you need to check that it's getting the proper signals and the fuel computer grounds the relay to turn it on. It does that when it detects the engine rpm signal so it knows it's making spark.
 
Thanks. My fuel pump relay is maybe 6 years old. Putting a new 1 in today even if only as preventive maintenance. You're right to suggest the problem could be grounds for relay and maybe ECM signals. The bump I hit was just enough to rattle a bad ground connection. The car has over 430k miles. Some rust near the exterior harnesses. I'm 67 and retired. I've done all the basic maintenance and a bit more. Has not been to a shop in 10 years. Owned it 28 years. It's perfect for camping and property projects so I'm hoping to keep it. Second time it's stranded me in 28 years. Engine runs perfectly (to now). 27 mpg hwy. 5 speed manual. Will test as you advise and report. I'm not good with electrical issues. Will take it to the shop next week if the fuel pump relay is not the issue.
 
Before you go any further test whether you are getting power to the fuel pump. The pump itself may have quit. You will need to have someone cycle the key on and off while you have a test light on the yellow power lead going to the fuel pump.
The body harness goes back to the floor area under the back seat on the driver side and goes down the fuel pump right below that area. There is a connector there for the short section of the harness that goes down through the floor. There is a 6mm bolt there that the pump ground wire attaches to.
 
2manyturbos said:
Before you go any further test whether you are getting power to the fuel pump. The pump itself may have quit. You will need to have someone cycle the key on and off while you have a test light on the yellow power lead going to the fuel pump.
The body harness goes back to the floor area under the back seat on the driver side and goes down the fuel pump right below that area. There is a connector there for the short section of the harness that goes down through the floor. There is a 6mm bolt there that the pump ground wire attaches to.
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Thanks. Just installed new fuel pump relay. No luck. And the main fuel pump did not prime which it has not since the fail. Yet to put a test light on the relay but suspect no power to it, so no power to the pump Does relay power come from ignition switch? Testing ideas?
 
Another thought. I have lots of keys on the car key ring. More than once I've hit pot holes shaking the ring enough to turn it a hair and shut off the car. Could the switch be worn from this abuse over time where a power contact in the switch no longer feeds the fuel pump relay?
 
haroldburbank said:
Thanks. Just installed new fuel pump relay. No luck. And the main fuel pump did not prime which it has not since the fail. Yet to put a test light on the relay but suspect no power to it, so no power to the pump Does relay power come from ignition switch? Testing ideas?
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The fuel pump relay is powered at all times. It is not switched with the ignition switch. Do you have a multi-meter or test light? You can check for power at the relay. It is the red wire going into the relay connector. I'm betting you have power there. Sit in the passenger seat and turn the key on/off while holding the relay. Do you hear/feel it click on? If it does, the yellow red wires at the relay are power to the pumps. Those should energize for about 1 second when the key is turned to the run position. If you see that happening then you have a bad connection going to the pumps or the pumps are dead.
 
haroldburbank said:
Thanks very much. Have test light and multi meter. Will get to work as you advised.
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Report your findings and we can go from there. The ECU grounds the relay turning on power to the pumps. The orange wire going to the relay is switched power. That is what supplies power to the electromagnets in the relay. The yellow-black wire is the ground for the main relay. The blue-green wire is the ground for the fuel pump relay. The ECU is what turns those grounds on and off. This is a 1990 240 LH 2.4 diagram. The only difference between this one and you 1992 is the fuse F is located on your fuse panel. It is fuse 6 if I remember correctly.

 
Very common to have the wire section that goes from the hole in the floor to the pumps decay and fall apart. Even on a 92 with the better wiring. Volvo was still selling the section of wiring or Dave Barton can also supply that.
 
2manyturbos said:
Report your findings and we can go from there. The ECU grounds the relay turning on power to the pumps. The orange wire going to the relay is switched power. That is what supplies power to the electromagnets in the relay. The yellow-black wire is the ground for the main relay. The blue-green wire is the ground for the fuel pump relay. The ECU is what turns those grounds on and off. This is a 1990 240 LH 2.4 diagram. The only difference between this one and you 1992 is the fuse F is located on your fuse panel. It is fuse 6 if I remember correctly.

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Not tested yet, but wondering what grounds the ECU? Also, what powers the ECU? You've explained the pump relay is powered and grounded by ECU. If the pumps don't prime at click 1 of ignition switch as they should, I think the ECU must not be sending power, perhaps due to poor ground. Have suspected the grounds on the car for months. Found the easy common ones and cleaned them. This after my bulba out relay overheated partly melting the plug. Weeks ago I found the brake and tail light wires passing through hatch hinges cut through due to that design flaw. The bulb out sensor melted before discovering the hinge wiring breaks. Wondered if these wire breaks caused shorts affecting the bulb out relay. All these electrical problems smack of bad grounds and short circuits to me. Will test fuel relay circuit as advised and report.
 
haroldburbank said:
Not tested yet, but wondering what grounds the ECU? Also, what powers the ECU? You've explained the pump relay is powered and grounded by ECU. If the pumps don't prime at click 1 of ignition switch as they should, I think the ECU must not be sending power, perhaps due to poor ground. Have suspected the grounds on the car for months. Found the easy common ones and cleaned them. This after my bulba out relay overheated partly melting the plug. Weeks ago I found the brake and tail light wires passing through hatch hinges cut through due to that design flaw. The bulb out sensor melted before discovering the hinge wiring breaks. Wondered if these wire breaks caused shorts affecting the bulb out relay. All these electrical problems smack of bad grounds and short circuits to me. Will test fuel relay circuit as advised and report.
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Do you know how to read a wiring schematic? The questions you are asking are all answered in the above schematic.
 
dl242gt said:
Your fuel pump relay is under the passenger side near the EZK ignition box on the firewall. You should see it after you remove the underdash cover. It's a white six pin relay. Use a test light on terminal 87 large red/yellow wire and see if it powers up on cranking. If it doesn't then you need to check that it's getting the proper signals and the fuel computer grounds the relay to turn it on. It does that when it detects the engine rpm signal so it knows it's making spark.
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tested today. relay is powered with key on.
 
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