Starter Relay
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Cross-Country
Joined: Jan 2004
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Starter Relay
I have a 1985 F250 and have been having trouble starting after setting for a few days. Some say the carb bowl is leaking. Since the fuel pump does not run unless the starter is cranking it has been suggested to jumper the battery to the "i" terminal on the relay for about 10 seconds to run the pump. My question is there are 2 small terminals on the relay and it is hard to tell where they go as some go in to a bundle. Can anyone tell me which is the "i" terminal - the right or the left?
Separate question: Why would Ford not design to run the pump when the ignition is turned on
Separate question: Why would Ford not design to run the pump when the ignition is turned on
Lead Driver
Joined: Nov 2013
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Look closely on the body of the relay. Should be a small S or I at the small terminals.
If not there, chock the wheels, put the transmission in neutral and momentarily connect a small test lead between the battery (+) post and either small terminal on the relay. The one that makes the starter spin is the S terminal.
BTW, your carb may not be leaking. Fuel may simply be evaporating after a few days.
Lead Driver
Joined: Nov 2013
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My best guess is they didn’t have to. They’d have been solving a problem that didn’t really exist at the time. Fuel chemistry has changed over the years and is no longer optimized for ancient carbureted vehicles.
Modern fuel no longer requires much resistance to evaporation, thanks to fuel injection and sealed tanks. But put modern fuel in a vehicle with a freely vented carburetor bowl and now evaporation can cause trouble.
In retrospect, we can say they should have included a pump prime function, but it wasn’t a needed feature back then.
Moderator
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From: Virginia
Look at the color of the wires on the small terminals. The colors do fade, but the "S" terminal will have a red/blue stripe wire on it. The "I" terminal will sometimes be blue or pink/black.
Are you using the original carb but the emissions have been taken off? That aggravates this problem of evaporation.
Are you using the original carb but the emissions have been taken off? That aggravates this problem of evaporation.
Moderator
Joined: Jan 2001
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From: Virginia
The colors on this wiring fade bad. You can faintly see the blue stripe on the red/blue wire in the picture above. Ford used the red/blue color for the start circuit for many years.
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Lead Driver
Joined: Nov 2013
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Another means to identify the small terminals:
Disconnect both wires. Use a multimeter to measure the resistance from each terminal to the relay base, where it bolts to the inner fender.
The S terminal is connected to the big electromagnet coil inside. The exact number isn’t important, but I’m guessing maybe 5-10 ohms.
The I terminal is isolated when the starter relay is not energized. You should see infinite resistance, same as if the meter leads aren’t touching anything.
Disconnect both wires. Use a multimeter to measure the resistance from each terminal to the relay base, where it bolts to the inner fender.
The S terminal is connected to the big electromagnet coil inside. The exact number isn’t important, but I’m guessing maybe 5-10 ohms.
The I terminal is isolated when the starter relay is not energized. You should see infinite resistance, same as if the meter leads aren’t touching anything.
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Lead Driver
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You're better off starting a new thread. Title your thread appropriately and after you post you will likely see related threads below. Also Your thread may help others with similar issues.
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