Fuel pump delays when I turn on the ignition??
#31
03-20-2016, 12:30 AM
Update - ECU replaced
I too was wondering if there was another reason for the delay. Below is a more detailed description of my diagnosis...
After looking at the wiring diagram, internally in the relay there is a bridge between terminals 6 (ecu power) and the + side of the pump relay coil with a resistor and a diode between. The other side of the pump relay coil is terminal 1, and needs to be grounded to close the relay contact at terminal 4.
I tested this by first disconnecting the ecu, then supplying a ground on relay terminal 1 to energize the coil and close the contact, which it did and forced the fuel pump to run. Relay test = ok.
From there, with ecu plugged back in, I then put a dvom on relay terminal 1 to test, and then after that to ecu terminal a7 to rule out a harness issue. At both ends with cold ecu dvom registered roughly battery voltage which is what was flowing through the pump relay coil, and after 30-60 seconds, it registered a ground for 2 seconds, then roughly battery voltage again. Then I cranked it over and went to ground again and started. With a warm ecu the ecu supplied the initial ground for 2 seconds right away.
Since the grn/blk wire isnt shown to go anywhere else, it cannot have a ground supplied from anywhere else but the ecu.
Conclusion is an ecu problem. Since the car has over 200,000 miles I will also put a relay in it for preventative measures.
After ecu replacement, I will post back. Take care!
After looking at the wiring diagram, internally in the relay there is a bridge between terminals 6 (ecu power) and the + side of the pump relay coil with a resistor and a diode between. The other side of the pump relay coil is terminal 1, and needs to be grounded to close the relay contact at terminal 4.
I tested this by first disconnecting the ecu, then supplying a ground on relay terminal 1 to energize the coil and close the contact, which it did and forced the fuel pump to run. Relay test = ok.
From there, with ecu plugged back in, I then put a dvom on relay terminal 1 to test, and then after that to ecu terminal a7 to rule out a harness issue. At both ends with cold ecu dvom registered roughly battery voltage which is what was flowing through the pump relay coil, and after 30-60 seconds, it registered a ground for 2 seconds, then roughly battery voltage again. Then I cranked it over and went to ground again and started. With a warm ecu the ecu supplied the initial ground for 2 seconds right away.
Since the grn/blk wire isnt shown to go anywhere else, it cannot have a ground supplied from anywhere else but the ecu.
Conclusion is an ecu problem. Since the car has over 200,000 miles I will also put a relay in it for preventative measures.
After ecu replacement, I will post back. Take care!
I was blessed to find a used ECU on EBAY for $50.00 and about $10.00 shipping. (New part was over $700! Other used ECU's were $150. Hey, for $60.00, was worth taking the chance!)
The ECU has been in the car for over a month and is working perfectly, on cold and warm days.
I did not replace the main relay yet, as I also performed a voltage drop test across the relay terminals which showed no significant drop in voltage when activated. If it acts up later, I will throw a relay at it. But for now the car works perfectly.
So, even as rare as ECU problems are these days, this one was officially bad.
Hope this diagnostic test plan will help someone in the future.
TheVanman
Last edited by TheVanman; 03-20-2016 at 12:32 AM.
#32
05-29-2020, 06:04 AM
1995 Honda Fuel Pump Issue Bad ECU
Its a bad ECU. I changed fuel pump and relay. Still had issues.. There are known problems with the ECU on the mid 90s Hondas. Google It. Change the ECU.
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ronie1983
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