Bad Fuel Pump or ?

[courtenay]

This goes back to my Tow Job thread... ('80 Fi)
The car would start when it was cold, run well for awhile, but would not restart. When I moved the AFM lever when cold, the fuel pump would turn on. When I moved the lever when the engine was hot, the pump would not run.
I replaced the dual relay, but this did not solve the problem.
In fact, now when I move the AFM lever even when the engine is cold, the relay clicks but the pump doesn't run. I've checked the voltage at the pump and there is 12.5 volts when the relay is operating.
I'm assuming my fuel pump is bad, but am wondering if there is any other electrical thing that would prevent the fuel pump from operating?
Any advice would be appreciated.

[76was124]

This goes back to my Tow Job thread... ('80 Fi)
The car would start when it was cold, run well for awhile, but would not restart. When I moved the AFM lever when cold, the fuel pump would turn on. When I moved the lever when the engine was hot, the pump would not run.

This problem sounds like the coolant temp sensor, it's a common problem. However, your replacing the relay giving problems when cold too now would make me think the fuel pump was marginal.

One thing to try so as to be sure 'the pump not working when cold' is not related to the new relay being the wrong type or defective, would be to put the old one back in and see if the car starts when cold. If it does, I would check the coolant temp sensor and double check you have the correct replacement dual relay.

If it doesn't start with the old relay either now, it's likely the fuel pump, or fuel pump ground.

there is 12.5 volts when the relay is operating.

When you checked the voltage at the pump was it with the pump still connected? If not, having 12.5volts on just a volt meter could still happen with a bad (high resistance ground). Check the pump ground connection, it should be in the trunk and wired to the driver side tail light circuit board under a long shafted thumb screw. I moved my ground to bare metal in the trunk with a new mounting bolt, star washer and nut.

[courtenay]

Thanks for the quick response. I have checked the relay - same result. The volts were measured through the electrical connections to the fuel pump so it's not a bad ground.

[azruss]

check your fuel pump by putting 12V across the leads. You can use a battery charger for this as the fuel pump only draws a few amps. You can also use the battery as well. If it doesnt run with a straight 12V, then you know its bad. Dont assume the 12V you read with the meter is the same. You can see 12V on the meter if there is no load and still not have the juice to run the pump. You need to isolate the pump from the car system to test it.

[courtenay]

Thanks Russ - I'll give that a try tomorrow.

[courtenay]

OK - connected the fuel pump directly to a fully charged 12V battery. The pump "clicked" when I connected the terminal but would not run.
I'm assuming I need a new fuel pump.
Anything else I should check?

[2ndwind]

You should have heard it humming. Even if you got the +/- switched when u hooked it up, it should still humm (running backward).

If you happen to buy a cheapo pump, the terminals may be the same size for +/-. Be sure you have +/- connected correctly. I bought a car that wouldn't run but I could hear the fuel pump running. It was hooked up backward, trying to pump gas to the tank.

[courtenay]

No humming - no sound at all. I've ordered a new pump from AR.

[courtenay]

New pump arrived today - thanks AR! Fourteen days from Texas to Vancouver Island via USPS, Canadian Customs and Canada Post. That's pretty good.
Anyway - made sure there was no crud in the gas tank, installed new pump and fuel filter. Car started right up. Drove for about 20 minutes or so to get it well warmed up, shut it off and it started right back up again. Wouldn't do that before.
It's pretty wet here today, and I don't drive my car in the rain, so will wait for a dry day to give it a longer run.
So far looks like the problem is solved.
Too bad top down season is pretty much done...

[spider2081]

great!!! Enjoy your ride