Fuel pump electrical woes

[pauls81sc]

Car is 1981 911 SC, all stock as far as I know. She was running rough and I parked her in the garage then I went back to school. Two and a half years later it's time to start driving her again.

New battery. New plugs. Cleaned major ground connections. Figured the fuel needed to go so I drained it and put in a couple gallons of new. Wanted to flush the fuel system so I pulled the injectors and soaked 'em in cleaner. While they were out I figured I would run the fuel pump and purge the fuel system.

This is where things start getting weird.

When I turn the key to 'on' position and lift the sensor plate inside the air box I can hear the relay click but the fuel pump doesn't run. When I jumped terminal 30 to 87a the frequency valve makes a loud buzzing sound (doesn't seem right) and still no fuel.

I disconnected the battery and checked the wires at the fuel pump and both wires have continuity to ground. That doesn't seem right either. Working backwards to the fuse box, again with battery disconnected, I check ground continuity at the relay sockets and all except 85 have continuity to ground.

I've searched the forums but haven't been able to find anything. Has anyone seen anything like this before?

[Joe Bob]

Typically it's either the relay is bad or the pump itself is frozen.

[pauls81sc]

Originally Posted by Joe Bob

Typically it's either the relay is bad or the pump itself is frozen.

So when you say 'frozen', are you telling me that not running it for a couple years ruins it?

And if so, is there a way to reverse that (besides buying a new one)?

Thanks,

Paul

[ossiblue]

Originally Posted by pauls81sc

So when you say 'frozen', are you telling me that not running it for a couple years ruins it?

And if so, is there a way to reverse that (besides buying a new one)?

Thanks,

Paul

I agree with Joe Bob, it sounds like your fuel pump is the problem. To answer your question, not running it will not necessarily ruin it, in fact it will have little effect on a healthy pump. However, if the bearings are going, and there is moisture in the fuel (very likely), and the fuel begins to leave varnish deposits, and the pump doesn't operate for two years, you have a set up for failure.

My suggestion would be to pull the pump and bench test it. It may be possible to free up the impeller if it's frozen, but I wouldn't want that pump on my car--but that's just me. Remember, that pump is likely thirty years old, and they don't last forever.

[Joe Bob]

When gas turns/breaks down due to sitting too long/age, it gums up parts. I picked up a Turbo a few years back....it was in a long sleep. One of two pumps was filled with gunk and not saveable.

The other was brought to life with a judicious use of Seafoam. I was able to save the fuel dist as well.

[pauls81sc]

Originally Posted by ossiblue

...
My suggestion would be to pull the pump and bench test it. It may be possible to free up the impeller if it's frozen, but I wouldn't want that pump on my car--but that's just me. Remember, that pump is likely thirty years old, and they don't last forever.

I pulled it and tried the bench test but it doesn't respond at all. Sounds like it's time to order the replacement.

Thanks for the help.

~ Paul