1985 fuel pump issue? sounds strange

Teddyd · Jul 31, 2020

HI, i just bought an 85 gt, it had no spark when I bought it so I replaced the coil and the ignition control module and now it starts. however it keeps cutting out and stalling when i test drive it. sometimes it will start back up sometimes it wont for a while. I have never had a carbureted mustang only efi. i'm familiar with the high pitch wine of the fuel pump but this one does not do that its kind of a quite "blub blub".if you leave the ignition on eventually it stops making noise completely, and the inline filter under the hood is never quite full. what is this fuel pump supposed to sound like? is this a high pressure pump like efi? or different? what is normal for an 85 pump?

Teddyd · Jul 31, 2020

General karthief · Jul 31, 2020

With a carb it should have a mechanical pump, inexpensive and easy to change, do the fuel filter too. I would check the fuel line under the car too in case it is pinched.

Teddyd · Aug 1, 2020

General karthief said:
With a carb it should have a mechanical pump, inexpensive and easy to change, do the fuel filter too. I would check the fuel line under the car too in case it is pinched.

I did some more investigating. It does not have a mechanical pump. It looks like it has one of those low pressure Holley pumps by the tank. Part number 12-801-1. I guess it detects when the bowls are full and shuts off automatically.... still not sure if it’s working 100%
The dude I bought it from took out the ballast resistor that goes before the coil and I’m wondering if that’s causing the coil to overheat?

General karthief · Aug 1, 2020

Check fuel pressure, and I don't know how a fuel pump could tell a carb float bowl is full.
Auto or stick car?

Blown88GT · Aug 2, 2020

Teddyd said:
I did some more investigating. It does not have a mechanical pump. It looks like it has one of those low pressure Holley pumps by the tank. Part number 12-801-1. I guess it detects when the bowls are full and shuts off automatically.... still not sure if it’s working 100%
The dude I bought it from took out the ballast resistor that goes before the coil and I’m wondering if that’s causing the coil to overheat?

Fuel pump by the tank sounds wrong but should work, but don't know how they did the '85's.
I had a 1977 Ford Courier that had an aftermarket 6psi fuel pump, which would overfill the fuel bowl. A 3psi factory pump solved the problem.
The low pressure pumps are silent.
When the carb float rises & closes the needle valve, it deadheads the low pressure pump, i.e no flow.
Yes. You need the ballast resistor.

Teddyd · Aug 2, 2020

So I believe I solved the problem. I started checking all the wires really good and the 4 prong plug that goes to the ignition control module was missing insulation on all 4 wires, and they were all twisted around each other. idk how I didn't spot this when I changed the module but I covered the wires with shrink tubes and soldered them back together as nice as I could. took her for a decent ride and it seems fixed. more power, no stalling or breaking down. she feels good.
Its amazing it ever ran at all like that.

side not about the fuel pump: it still sounds funny but i pulled the fuel line off the carb and its definitely pumping... seems to work so Ill leave that alone for the moment.

1985 fuel pump issue? sounds strange

Teddyd

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Teddyd

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General karthief

wonder how much it would cost to ship you a pair

Teddyd

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General karthief

wonder how much it would cost to ship you a pair

Blown88GT

Teddyd

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1985 fuel pump issue? sounds strange

Teddyd

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General karthief

wonder how much it would cost to ship you a pair

Teddyd

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General karthief

wonder how much it would cost to ship you a pair

Blown88GT

Teddyd

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