No power to fuel pump

[babyrat]

Hello Everyone,

I've decided it was time to get the old 928 back on the road again. It's a 1981 auto transmission. It is the poster child for the 1981 Weinrot on the landsharkoz colour page. Not so shiny anymore.

It has been sitting a while (over a year), so I expect some problems, but not this one.

It seems the fuel pump is not working. Checking around I found some info on jumpering the relay, so I did with no luck - could not hear the fuel pump running. I then tested for voltage at the pump itself and found none. The fuse is good, battery has plenty of juice and all the lights back there work.

So my question for the moment is, with 15 and 30 of the relay jumpered, and the ignition switch on, should there be voltage at the fuel pump? There is no sensor that senses the engine running and stops the fuel pump after a set period of time? (I have read the LH systems have something like that, and my corvette used to stop the pump after 15 seconds IIRC).


Any and all help is appreciated.

Thanks,

Jerry

[vdubr928]

Yes, as long as you are jumping the correct realy.

Your going to have to get out the voltmeter again and test the top and bottom poles at the relay. Pull the realy. Stick the leads in the socket (top and bottom) turn the key on. Make sure your ignition is sending power to the relay trigger.

[babyrat]

Well, sometimes I wonder if I am in the right car, never mind having the right relay.

There is no voltage across the upper and lower connections in the relay, either with the ignition switch off, on or start.

I did find if I jumper left and right, I do in fact have voltage at the pump but it still doesn't run.

Could I have a bad pump and a bad switch?

I'm planning on trying external power to the pump to see if it runs, just to make sure. It doesn't run, and I can't hear any humming or anything.

[Arizona_928]

you can try jump it with the battery, but if it has juice and still isn't running my bet is that it's bad. you can confirm by bench testing it also... but that isn't your main problem though. I would say check the switch, and maybe DME, but the 928 DME's don't go bad as quick as the 944's do.

[american-kiwi]

when i got my 82 home...i had the same thing...ended up being a locked up fuel pump from sitting too long....like you, i had 12v at the pump...but nothing was happening...it didnt even blow the fuse either (?)..used the meter and jumper, put a new pump in...all happy again..lol

[Mrmerlin]

take the fuel pump off and spray some carb cleaner into the inlet let it sit for about 30 mins. then dump it out then refill the pump with marvel mystery oil and let it sit overnight.
hook up 12v on the bench and see if it runs

[vdubr928]

Originally Posted by Mrmerlin

take the fuel pump off and spray some carb cleaner into the inlet let it sit for about 30 mins. then dump it out then refill the pump with marvel mystery oil and let it sit overnight.
hook up 12v on the bench and see if it runs

Never bench a fuel pump. Running one dry is a sure way to kill it if it's not already dead.

[Mrmerlin]

Thanks V Dubr, I guess i could have added more info.
It isnt a good idea to run the pump dry,

That said if its not turning at all there isnt any harm in working the pump back and forth till it does start to turn.
SO if you have it off the car you can run the pump with a small container of fluid and few hoses this way the fluid will be recirculated , it works pretty well, use the Marvel Mystery oil as a fluid

[vdubr928]

Yeah, I've brought a couple back from the dead. If only long enough to get another.

[new928]

i dont mean to revive an old thread but in the instance that someone like me with the same issue stumbles across it. im pretty sure the 2 posts that should be jumped are 30 and 87 not 15 and 87. this is how i got my fuel pump to run 15 and 87 did not work for me

[DPW928]

If you jump the 15 to 87 connections, the ignition switch needs to be in the on position to provide voltage to the pump. 30 to 87 is direct from the battery.