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Old 05-13-2009, 10:47 AM   #1
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Default 1:1 Fuel delivery issues

Ok, so this month I am working on an 86 4x4 Subaru GL wagon carbuerated with an electronic fuel pump. It just started giving me what seems to be fuel issues. It died a couple times, I let it for a little while then re-started it, and it drove fine. Then last week it just out and dies on me. It would start and run for about 30 seconds after it sat for a while, then would die. But if I put gas down the carb, it would run until the gas burnt off. Last night I started it up and it ran for a couple minutes then choked off and died. I unplugged the fuel pump and plugged a 4S lipo into it then started it. It ran until I needed to pull off the lipo. So I quickly unplugged the lipo and plugged the normal plug back in. While the plug was off I tested it for voltage, and it was getting a steady 13.53 volts. Then the thing ran fine. Tonight I am going to wire in a toggle switch in line with the +wire on the fuel pump directly to the battery until I figure out the issue. I was told it may be a fuel pump relay starting to go out. I did put in a new fuel filter and it didn't seem to help when it wasn't running. I need to figure out where the hell the relay is on this car.


Any bright ideas or help would be appreciated. It is scarrier that it has a problem that starts at its whim and I cant find it, more than whatever the problem actually is. With how often I drive in areas with out cell phone reception, it would be super lame to be up a creek without a paddle if the turd died on me again.

Thanks
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Old 05-13-2009, 12:33 PM   #2
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Fuel Pump Relay? Could be worn bad inside causing it to overheat and trip off. If your getting Voltage and it runs for a bit then dies, id start there.
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Old 05-13-2009, 12:50 PM   #3
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Carburator inner pump diaphram? seem the electric pump is working fine? could also have worn bearing/bushing on the pump.
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Old 05-13-2009, 02:09 PM   #4
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Switch the fuel pump relay with the washer fluid relay, they should be the same on that car. If that cures your prob. then you know its the relay.
If that doesnt fix the problem, unhook the fuel pump all together, get a friend or your wife to help you here. Start the car and let it idle, dont touch the throttle. Once it starts to die spray some WD-40, (not starter fluid) directly into the carb. If that makes it continue to run, and stop sputtering, then its deffinatly the pump.

If that doesnt cure the problem, then the problem is in the carb.

I wouldnt recommend hooking the battery straight to the pump. You could force the fuel pump to pump to much fluid into the carb and flood the motor.

Most likely its the fuel pump. Its probably going bad and is having a hard time pumpin the fuel to the carb.
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Old 05-13-2009, 02:15 PM   #5
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Sounds like the relay. Put a new one in and that should cure the problem. Also wiring i directly may work but if you have to many amps getting drawn the switch will fail. You can get like a 30 amp switch and that will work. There is no problem with it pumping to much fuel thats what a fuel regualter is for. Brings down the pump pressure to a usable press. for the carb.
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Old 05-13-2009, 03:18 PM   #6
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Quote:
Originally Posted by dezslash View Post
Sounds like the relay. Put a new one in and that should cure the problem. Also wiring i directly may work but if you have to many amps getting drawn the switch will fail. You can get like a 30 amp switch and that will work. There is no problem with it pumping to much fuel thats what a fuel regualter is for. Brings down the pump pressure to a usable press. for the carb.

I kinda did the same thing with my Eclipse. Bosch relay taking orders from the ECU, but powered right from the battery. The teeny tiny wire that Mitsu uses to power the pump would drop voltage.
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Old 05-13-2009, 03:20 PM   #7
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Yeah, I figured it wouldnt hurt the car with my 4S hooked to it because I let it run for about 10 minutes like that and I blipped the throttle a couple times and it was smooth as butter. In fact, it seemed to run better with the 4S hooked up... Even when it drained down to 10 volts. But when it was giving me crap, it would be very hesitant and have a huge flat spot in the throttle. I was just going to get a 50amp 12v switch and wire it in line and drive it to Napa. And if it dies, and wont start, then I flip the switch, it starts... I know the fuel pump is still working and it is something else.
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Old 05-13-2009, 03:23 PM   #8
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You should see if you can back-probe the pump connection to see what its loaded voltage is...I bet its low.
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Old 05-13-2009, 08:19 PM   #9
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Quote:
Originally Posted by Chris_The_Battery_Man View Post
Ok, so this month I am working on an 86 4x4 Subaru GL wagon carbuerated with an electronic fuel pump. It just started giving me what seems to be fuel issues. It died a couple times, I let it for a little while then re-started it, and it drove fine. Then last week it just out and dies on me. It would start and run for about 30 seconds after it sat for a while, then would die. But if I put gas down the carb, it would run until the gas burnt off. Last night I started it up and it ran for a couple minutes then choked off and died. I unplugged the fuel pump and plugged a 4S lipo into it then started it. It ran until I needed to pull off the lipo. So I quickly unplugged the lipo and plugged the normal plug back in. While the plug was off I tested it for voltage, and it was getting a steady 13.53 volts. Then the thing ran fine. Tonight I am going to wire in a toggle switch in line with the +wire on the fuel pump directly to the battery until I figure out the issue. I was told it may be a fuel pump relay starting to go out. I did put in a new fuel filter and it didn't seem to help when it wasn't running. I need to figure out where the hell the relay is on this car.


Any bright ideas or help would be appreciated. It is scarrier that it has a problem that starts at its whim and I cant find it, more than whatever the problem actually is. With how often I drive in areas with out cell phone reception, it would be super lame to be up a creek without a paddle if the turd died on me again.

Thanks

Shouldn't have gotten rid of the yota...


(by the way, this is keith jr.)
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Old 05-14-2009, 11:30 AM   #10
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The yoda was actually crappier. It looked cool, but wasn't nearly as mechanically sound
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Old 05-14-2009, 11:55 AM   #11
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I would wire a light and/or voltmeter in parallel with the connection to the pump to see if it's dropping voltage when the car dies.
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Old 05-15-2009, 12:47 PM   #12
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Quote:
Originally Posted by Jeckler View Post
I would wire a light and/or voltmeter in parallel with the connection to the pump to see if it's dropping voltage when the car dies.
I actually did that and have driven it about 60 miles since without any luck replicating the problem. I do notice the voltage bumps around between 13.4 and 12.5 and is in-consistant. But we will see if it does it again, and there is no voltage going to the pump
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Old 05-15-2009, 04:08 PM   #13
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The more you fuk with the relay, the harder it's going to be to track down the problem Lots of times you'll have some corrosion on the relay socket, or the wiring behind the relay panel, and pulling the relay in and out will bust enough of it loose to "fix" it for a little while.

Just carry a few extra lipos around, and call it a hybrid
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