 Fuel Pump Troubleshooting, I'm stumped |
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| ThinAir |
 Sep 17 2019, 07:12 PM
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Best friends  Group: Members Posts: 2,569 Joined: 4-February 03 From: Flagstaff, AZ Member No.: 231 Region Association: Southwest Region 
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Trying to get my car on the road for Red Rock Classic. It's not looking good.
I had an intermittent problem with the fuel pump not running, which at the moment seems to be no longer intermittent. I've successfully tested the pump by connecting it to a battery charger. I've followed the steps in the two fuel pump diagnostic documents at Jeff Bowlsby's site (http://bowlsby.net/914/Classic/zTN_FI_FPChecklist.pdf and http://bowlsby.net/914/Classic/zTN_FI_FPChecklist2.pdf). They both fail at the point where it says I should wrap a wire around pin 87 and reinsert the relay. I get no power on the wire. Following the steps in the Brad Anders document, I don't have 12V on pin 86 and when I test pin 8 on the plug I have power so that means I have a faulty relay board trace. My board was rebuilt last year by a member here who has a great reputation so I don't have any reason to doubt my relay board. I have also tested with 2 other relay boards as well as multiple relays - all with the same result. It just doesn't make sense to me that 3 boards could all have the same issue. I'm stumped. Can anyone provide some additional things to check? |
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| Spoke |
Sep 17 2019, 08:44 PM
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Jerry Group: Members Posts: 7,295 Joined: 29-October 04 From: Allentown, PA Member No.: 3,031 Region Association: None
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You can isolate the fuel pump drive circuitry from the FI ECU. I assume you have fuel injection and the OEM FI ECU.
Here's a way to check the fuel pump drive circuitry: 1) Pull the FI ECU plug from the relay board connector. 2) Pull the +12V wire from the Positive + connection on the ignition coil. This is just to keep the coil/points/Pertronix/electronic ignition from overheating while you do the test. 3) With a separate wire with female spade connector, connect to pin III on the relay board FI connector and connect the other end of the wire to chassis ground. This will turn the fuel pump on full time with ignition on. 4) Turn ignition switch to ON; don't start the engine. You should hear the fuel pump run full time. With this setup, you can check the fuel pump control circuitry without interference from the FI ECU. |
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Posts in this topic
ThinAir Fuel Pump Troubleshooting Sep 17 2019, 07:12 PM
TravisNeff I would also suspect the relay board. When you tu... Sep 17 2019, 07:26 PM
ThinAir Thanks, Spoke. I'll give that a try in the mor... Sep 17 2019, 11:50 PM ThinAir Grounding pin III does indeed cause the pump to ru... Sep 18 2019, 12:53 PM rhodyguy Can you use the carb jumper wire trick to power th... Sep 18 2019, 12:58 PM ThinAir
Can you use the carb jumper wire trick to power t... Sep 18 2019, 01:06 PM SirAndy Can you use the carb jumper wire trick to power th... Sep 18 2019, 01:09 PM SirAndy Is your fuel pump fuse OK? (91) in the pic below.
... Sep 18 2019, 01:12 PM ThinAir
Is your fuel pump fuse OK? (91) in the pic below.... Sep 18 2019, 01:22 PM dr914@autoatlanta.com no all three cannot be bad and relay boards rarely... Sep 18 2019, 01:40 PM ThinAir It works again!
After reviewing the diagram, ... Sep 18 2019, 01:40 PM Spoke
It works again!...I'm thinking that I jus... Sep 18 2019, 07:25 PM ThinAir :driving: WooHoo!!!!
Just got ba... Sep 18 2019, 03:46 PM SirAndy Red Rock Classic 2019 - here we come!
Pack sp... Sep 18 2019, 04:52 PM jim_hoyland A spare pump is cheap insurance... :) Sep 18 2019, 04:33 PM |
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