What would cause my Fuel Pump to stay ON after I turn off the car?
09-18-12, 11:08 PM
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What would cause my Fuel Pump to stay ON after I turn off the car?
Old thread for reference:
https://www.clublexus.com/forums/sc-...ebody-kit.html
^Thread summarized: My sc would throw a code 14, and would get a sort of fuel cut off/stutter while driving. After grounding out my battery completely by running wires from the battery to the engine, and the engine to the chassis the problem completely went away. This, paired with my drain issue being caused by my fuel pump which I still haven't figured out has given me a big, big headache.
Currently,
My fuel pump will not shut off after I turn off the car. It was draining my battery until I figured out that it was staying on all the time. So for the time being, I have to go to the back of the trunk, disconnect the fuel pump harness and then connect it again when I want to drive it to prevent battery drain. It stumped me for over a YEAR because I would keep buying new batteries and they resisted the drain for a few months, then the problem would appear again after the battery started to weaken from the drain. (Regardless...)
So I figured out the previous owner did the 12v fuel ecu bypass mod by connecting the two wires... And I checked my main EFI fuel fuse in the fuse box in the front. It keeps getting EXTREMELY hot. Initially I swapped the defroster fuse with the EFI and the fuel pump would shut off like normal again, but then after driving it for the rest of the day the problem came back and hasn't gone away since.
Now, where do I go from here? I couldn't find anything in the search/google because every thread I find remains inconclusive. The last resort thing to do here would be a kill switch running to the main EFI, but I rather do this the right way.
any ideas?
also if someone could tell me why my SC idles at 3k. I would really appreciate it, lol.
https://www.clublexus.com/forums/sc-...ebody-kit.html
^Thread summarized: My sc would throw a code 14, and would get a sort of fuel cut off/stutter while driving. After grounding out my battery completely by running wires from the battery to the engine, and the engine to the chassis the problem completely went away. This, paired with my drain issue being caused by my fuel pump which I still haven't figured out has given me a big, big headache.
Currently,
My fuel pump will not shut off after I turn off the car. It was draining my battery until I figured out that it was staying on all the time. So for the time being, I have to go to the back of the trunk, disconnect the fuel pump harness and then connect it again when I want to drive it to prevent battery drain. It stumped me for over a YEAR because I would keep buying new batteries and they resisted the drain for a few months, then the problem would appear again after the battery started to weaken from the drain. (Regardless...)
So I figured out the previous owner did the 12v fuel ecu bypass mod by connecting the two wires... And I checked my main EFI fuel fuse in the fuse box in the front. It keeps getting EXTREMELY hot. Initially I swapped the defroster fuse with the EFI and the fuel pump would shut off like normal again, but then after driving it for the rest of the day the problem came back and hasn't gone away since.
Now, where do I go from here? I couldn't find anything in the search/google because every thread I find remains inconclusive. The last resort thing to do here would be a kill switch running to the main EFI, but I rather do this the right way.
any ideas?
also if someone could tell me why my SC idles at 3k. I would really appreciate it, lol.
Last edited by Bleak; 09-18-12 at 11:12 PM.
09-19-12, 08:20 PM
#2
This could be multiple problems at once. The idle at 3k could be TPS, ECU or MAS. Check those and try to eliminate the possibilities(could also be related to fuel pump/regulator). The fuel pump; did you actually check the 12v mod to see if it was done correctly or if it is shorting out? In your post you just say "I figured." It's easy to get to the wires I would start there and report back. If they are not soldered and heat shrunk I would re-do them to be safe.
09-19-12, 09:04 PM
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This could be multiple problems at once. The idle at 3k could be TPS, ECU or MAS. Check those and try to eliminate the possibilities(could also be related to fuel pump/regulator). The fuel pump; did you actually check the 12v mod to see if it was done correctly or if it is shorting out? In your post you just say "I figured." It's easy to get to the wires I would start there and report back. If they are not soldered and heat shrunk I would re-do them to be safe.
09-21-12, 07:15 PM
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my efi relay would over heat, turns out i bought a new one from toyota (they still use the relay in their cars today) for 12$ and no more fuel pump issues.
To me i would test the relay by putting it in and trying to see if you can get the pump to stay on. then take off the pump and put a stripped short wire or paper clip in place of the relay and see if the pump stays on
To me i would test the relay by putting it in and trying to see if you can get the pump to stay on. then take off the pump and put a stripped short wire or paper clip in place of the relay and see if the pump stays on
09-22-12, 12:12 AM
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my efi relay would over heat, turns out i bought a new one from toyota (they still use the relay in their cars today) for 12$ and no more fuel pump issues.
To me i would test the relay by putting it in and trying to see if you can get the pump to stay on. then take off the pump and put a stripped short wire or paper clip in place of the relay and see if the pump stays on
To me i would test the relay by putting it in and trying to see if you can get the pump to stay on. then take off the pump and put a stripped short wire or paper clip in place of the relay and see if the pump stays on
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09-27-12, 12:01 PM
#8
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My SC400 started doing the same thing when I did the 12v mod. My problem was actually the ignition switch. When turning it off,trying pushing the key in while turning it off. My guess is theres a short in the switch causing it to stay on.
09-28-12, 06:35 PM
#9
Originally Posted by bryan767
my efi relay would over heat, turns out i bought a new one from toyota (they still use the relay in their cars today) for 12$ and no more fuel pump issues.
To me i would test the relay by putting it in and trying to see if you can get the pump to stay on. then take off the pump and put a stripped short wire or paper clip in place of the relay and see if the pump stays on
To me i would test the relay by putting it in and trying to see if you can get the pump to stay on. then take off the pump and put a stripped short wire or paper clip in place of the relay and see if the pump stays on
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09-29-12, 08:49 PM
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A mechanically failing pump/poor flowing filter/fuel lines can cause a high amp draw, which in turn can weld the relay contacts together. This can give you warm/hot wiring/fuses/relay, constant fuel pump running, low power at WOT/High RPM.
I would do all of the following in this order:
swap the relay
measure the amperage the pump is drawing
measure parasitic drain
test fuel pressure
Swapping the relay may fix the problem in the short term, but if you have an underlying problem, it may reoccur.
That said, relays are a mass produced item, subjected to the last 20 years of heat, vibration and use, they do just "go bad"
I would do all of the following in this order:
swap the relay
measure the amperage the pump is drawing
measure parasitic drain
test fuel pressure
Swapping the relay may fix the problem in the short term, but if you have an underlying problem, it may reoccur.
That said, relays are a mass produced item, subjected to the last 20 years of heat, vibration and use, they do just "go bad"
09-30-12, 09:19 AM
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A mechanically failing pump/poor flowing filter/fuel lines can cause a high amp draw, which in turn can weld the relay contacts together. This can give you warm/hot wiring/fuses/relay, constant fuel pump running, low power at WOT/High RPM.
I would do all of the following in this order:
swap the relay
measure the amperage the pump is drawing
measure parasitic drain
test fuel pressure
Swapping the relay may fix the problem in the short term, but if you have an underlying problem, it may reoccur.
That said, relays are a mass produced item, subjected to the last 20 years of heat, vibration and use, they do just "go bad"
I would do all of the following in this order:
swap the relay
measure the amperage the pump is drawing
measure parasitic drain
test fuel pressure
Swapping the relay may fix the problem in the short term, but if you have an underlying problem, it may reoccur.
That said, relays are a mass produced item, subjected to the last 20 years of heat, vibration and use, they do just "go bad"
09-30-12, 01:51 PM
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Without having Lexus specific values, that should be about right. Check a fsm to be sure
edit 38-44psi no vac/KOEO 28-34psi idle
edit 38-44psi no vac/KOEO 28-34psi idle
Last edited by gambit4000; 10-01-12 at 10:47 AM.
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