86 ford motor home (460cid) fuel pumps

Front tank fuel pump only operates in crank mode filling carb and allowing engine to run untill carb empty. Will restart and same thing happens. The rear tank pump is dead at all times. This problem happened when attempting to start after it sat for some time. We had to replace a starter and battery and while checking roll over switch (bypassing it) it did not start. However all of a sudden it decided to start and run long enough to pass CA smog (dyno test) and return home about twenty miles away. It has not started since. I have no wire diags and think it may be the loss of a ground or connection. Any clues to finding usable diagrams or where to look for connectors. Thanks in advance for any help, would like to go out on dads day for trip.

Reply to
Bob S
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If it's an electric fuel pump you should test it with a simple voltage meter and jumper wires. Put 12 volts to the connector on the pump. If it doesn't run, the fuel pump is bad. Check for voltage when the key is on, if the fuel pump doesn't run, then something in the control wiring has an issue.

If the pumps run when you put 12v to them. Then you'll need to track the wiring down to see what's keeping them from coming on. There may be a impact safety that cuts out the pumps if you crash. you mentioned something about a roll over switch. The pumps are likely run by a relay, so try to track the wires down to the relay. Then find the wires that energize the relay and see what they go through.

Reply to
Mike H

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