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Hello, I’m diagnosing a fuel pump issue on a 91 Honda Accord (original fuel pump). With the gas tank dropped and out of the way, I don’t get any voltage reading at the fuel pump connector, but I do get ~12V at the meter unit plug that’s part of the same wire harness. I read that when the key is turned to position II, the fuel pump should only turn on for a few seconds. When I tried to measure with someone else turning the key, I only see maybe 0.03V jump on the meter before the meter shows 0V again. No corrosion to the wires. Any thoughts or suggestions?
I tried applying 12V to the fuel pump directly and it appears to run so I’m doubting it’s the fuel pump. Could a bad fuel relay only send power to the meter unit connector but not the fuel pump connector? Thanks.
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check fuses for the pump. Do you have spark when cranking? I believe there is a fuel pump
connector under the back seat. check that its plugged in. Main relay would be next. more in this link.https://www.ericthecarguy.com/faq/solving-automotive-no-start-problems
Appreciate the link. Yes, there is spark when I crank. The issue is fuel supply, no fuel to injectors, no sound of fuel pump when ignition switch is first turned ON. So here are the items I’ve checked so far.
– Checked fuses, no breaks observed.
– Took main relay out to test by applying power to respective terminals and getting continuity.
power 6,8 – continuity 5,7
power 2,5 – continuity 1,3
power 3,8 – continuity 5,7
– On main relay connector, continuity verified between pin 2 and body ground.
– On main relay connector, measured voltage between pins 1 and 2.
– On main relay connector, measured voltage between pins 2 and 5 with ignition switch ON.
– Disconnected 3P connector in trunk, jumpered pins 5 and 7 on mail relay connector plug, and found voltage available with positive probe on 3P yellow wire and negative probe on body ground.I also have my fuel tank dropped and applying a voltage probe to the actual plug under the car that goes to the fuel pump, I get 0 V. I suspect there must be something physically wrong or loose with that small length of wire from 3P in trunk to underbody. Have you encountered this before?
The fuel pump was removed and I applied power direct from 12V battery, it started so I think the fuel pump is fine.
[quote=”teatime2morrow” post=170213]Appreciate the link. Yes, there is spark when I crank. The issue is fuel supply, no fuel to injectors, no sound of fuel pump when ignition switch is first turned ON. So here are the items I’ve checked so far.
– Checked fuses, no breaks observed.
– Took main relay out to test by applying power to respective terminals and getting continuity.
power 6,8 – continuity 5,7
power 2,5 – continuity 1,3
power 3,8 – continuity 5,7
– On main relay connector, continuity verified between pin 2 and body ground.
– On main relay connector, measured voltage between pins 1 and 2.
– On main relay connector, measured voltage between pins 2 and 5 with ignition switch ON.
– Disconnected 3P connector in trunk, jumpered pins 5 and 7 on mail relay connector plug, and found voltage available with positive probe on 3P yellow wire and negative probe on body ground.I also have my fuel tank dropped and applying a voltage probe to the actual plug under the car that goes to the fuel pump, I get 0 V. I suspect there must be something physically wrong or loose with that small length of wire from 3P in trunk to underbody. Have you encountered this before?
The fuel pump was removed and I applied power direct from 12V battery, it started so I think the fuel pump is fine.[/quote]
on some cars the fuel pump will only kick on for a secand then turn back off… what I could recommand trying is plug the fuel pump in and disconnect it before the feul fuilter and see if that kicks out a stream of fuel when you try to start it… because if the fuilter is fuly clogged it could cause the pump not to be able to spin
another thing you can check is the feul lever gaudge try to move it and see if moves in the dash….. why you might want to check it is because they run down the same cable uselly and might tell you if you have a bad connecotr or cable is brokealso check to see if your car has a feul safty cut off switch… because that wireing and or sw can be engaged
check that you have the inputs to the relay. see if this diagram helps. I’m wondering
if the ignition switch is going from 5- 7http://www.justanswer.com/car/02vwu-testing-main-relay-1991-honda-accord-dx.html
Thanks for all the feedback and suggestions. So I redid all the tests in the order based on the link provided. All tests passed.
http://www.justanswer.com/car/02vwu-testing-mai…honda-accord-dx.html
On the very last harness test with the relay removed, pins 5 & 7 jumpered on the connector, I do get voltage to the pump’s 2P connector. Knowing from a separate test that the fuel pump works, this seemed to point back to the relay. :blink:
Perplexed, I redid the pin and continuity tests on the relay one more time. Again, it passes. So I’m stumped. I decided to re-install the relay. Now the whole thing works. When key is turned to ON, I get a few seconds of voltage to the 2P pump connector before it shuts due to ECU not detecting engine turning. If I attempt to crank, I get voltage to 2P connector. So I didn’t replace anything and it works normal now.
Aside from the known Mitsuba solder issues, could this be a failing relay where sometimes it works, sometimes it doesn’t and has nothing to do with the solder points? All the tests were done at room temp so I can’t say the relay only acts up when it gets hot. I don’t believe it’s a ground issue because I didn’t tweak or clean any of my ground points. All grounds visually look good and all tests involving ground always pass. The relay is 20+ years old at this point.
It could be the relay but my gut is saying electrical portion of the ignition switch
is not sending to 5-7 keep us posted on how things play out. next time it happens
check that ignition switch input to the relay.Just wanted to give an update on my issue. It was indeed a bad relay, at least a failing relay that inconsistently worked. The times I tested directly with a 12V source, it actually worked, so that only made earlier troubleshooting that much more confusing. I just opted to take a chance and replaced with a new relay and the car no longer has any fuel supply issues. Appreciate the feedback from all.
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