Fuel Pump Issues, Please Helpq

seafood10 · 12-29-2023, 04:22 PM

Hi,
this is for my 88 930 slant. 2 weeks ago the car wouldn't start and I found the fuel pump fuse in this condition, pic below.
I thoroughly cleaned the contacts as I thought there may be some resistance, the plastic melted but the element was still intact, and yes, I know. I need to get the ceramic fuses and I don't want to upgrade to the blade fuse panel, I like stock.

Anyway, I was driving today and car quit, I checked the new 20 amp fuel pump fuse and it was in brand new condition, I tried changing the relays and other tricks but ended up calling Hagerty for a tow.

I was sitting there for about 30 mins and tried the key again and heard the pump so I started it and took off towards home, thankfully I live down the hill from there as the car died a few times and I bumped it back to running and then died but I had enough momentum to make it in my garage, so happy about that as a flatbed won;t fit down my long driveway.

Before I tear into everything I was wondering if a bad DME relay could do this, or would a bad pump act in this manner? It seemed to work when it cooled down while I was waiting and it's been an hour now and will not energize., and the fuse connection has 12.5v so that's OK.

Any help is truly appreciated if you know where to look before I take out that monster 3 way powered seat.
Here is the pic from 2 weeks ago:

Happy New Year!

seafood10 · 12-29-2023, 05:36 PM

I just tried the key and can hear the pump energize. A buddy told me to get the car running and use my FLIR camera to look at the fuse and pump when I put it up on my lift which I'm going to do tomorrow.
But if anyone knows why it would intermittently fail, more than likely when the car has been run for about 30 mins, I would like to hear any possible reasons.
Thanks!

GH85Carrera · GH85Carrera's Garage

When my original DME relay was dying, it was like someone turning the ignition off for a 1/2 to 1 second at random. I replaced the relay and it was cured. And of course the relay controls the fuel pump.

seafood10 · 12-29-2023, 07:50 PM

Hey Glen, thanks for the reply, it was what I was looking for, to see if others have had intermittent issues with the DME relay
This one is hard to diagnose as the pump will work but doesn't want to work when the car has been driven for about 30 mins. so I will start with the relay and also check the wiring at the pump to make sure it's not corroded or damaged.

Also, I like you motto!

Jeff Alton · 12-29-2023, 08:07 PM

Your turbo does not have a DME relay though...

seafood10 · 12-29-2023, 08:15 PM

Quote:

Originally Posted by Jeff Alton

Your turbo does not have a DME relay though...

DOH! I can't believe I forgot that it's a CIS!! I've had my 84 Cab since 96 and so used to thinking about DME issues I completely forgot, a true idiotic moment on my part!
You win the Internet tonight!

seafood10 · 12-29-2023, 08:58 PM

So I just turned on the ignition without starting the car, the pump energized and I pointed the FLIR to the fuse panel and discovered a different issue but the pump fuse kept it's cool.....
Cab's don't have a rear window defroster so that helps deduce this new issue.

I'll use the FLIR tomorrow with it running and see what happens

Thanks again to Jeff!

seafood10 · 12-30-2023, 02:58 PM

So the FLIR found the issue, you can see inside the pump at how hot it's getting after only running a few minutes, along with the fuse.

I could also hear a sort of 'grinding' sound coming from the pump so a new one is on order