Need help with fuel pump relay

deserttoad · 05-29-2015, 03:41 PM

I've been reading through the posts about the fuel pump relay. Simple version is that terminal 30 should have 12 volts, when jumped to terminal 87 the circuit is complete and the fuel pump should run. Well I don't have 12 volts at thermal 30, I have zero. If I send 12 volts to terminal 87, the starter engages.

I had problems with this relay in the past, but once I got the terminals all cleaned up with deoxit, its been working fine.

What has happened?

Thanks!

1979 Euro

stepson · 05-29-2015, 03:53 PM

You should be dealing with the third relay from the right on the bottom row which is the fuel pump relay.

It appears that are trying to work on the 4th relay from the right on the bottom row which is the starter relay.

deserttoad · 05-29-2015, 03:56 PM

I just figured that out. As many times as I've taken this relay out in the past, I feel like a real idiot. ran jumper and the car fired right up. Thanks for quick response. Now someone please delete this embarrassing post..... ;-)

stepson · 05-29-2015, 03:58 PM

Go to 928 SPECIALISTS ONLINE STORE - 30,000+ 928 Parts - 928 SUPERCHARGER KITS! and find the fuse/relay chart for your model year car. I always print a couple out and carry one in my glove box.

And believe me, although I have done something like this a hundred times, it never feels any better when you realize what you've done, except that it was actually an easy fix in the end.

deserttoad · 05-29-2015, 06:32 PM

Yes indeed stepson. Easy fix, just need a new fuel pump relay!

stepson · 05-29-2015, 08:01 PM

I bought an '83 once upon a time as a package deal with another more desireable to me 928. I was told that something was wrong with the engine and it was a parts car. Sure enough, the fuel pump had been removed and wrongfully placed on the other purchased car, the fuel tank was in the passenger seat, and the fuel pump harness had been cut. But the more I looked at that car, the more I realized it just had not been taken care of recently, and for most of it's life had been well taken care of.

I was determined to bring this car back from the dead. I replaced the fuel pump and the fuel tank and did the timing belt and tensioner. Everything I thought was corrected as it should have been, but the car would not run without spritzing fuel through the "barn door".

I did everything I could think of to make that car run for about a month. It came to me in the shower before work one morning: I had never checked that the fuel injection relay was correct. Lo and behold it was not. With a towel around my waistand in my driveway, I replaced that relay with a correct fuel injection relay and the car ran like a banshee. Never have I felt like such a dumba$$ and almost never have I had that kind of elation all at the same time.

deserttoad · 05-29-2015, 08:54 PM

That is a great story! Our 928 was due to be scrapped, so we saved it. Only thing left to do is the timing belt/water pump. But I don't think I'm ready to attempt it. As a farmer I work on equipment all day long. I've rebuilt old tractors, a Ford Model A, a '51 international pickup, a '67 jeepster. But I'm leery to tackle the timing belt on this "modern" car. Perhaps a northern Nevada member could me out....

deserttoad · 06-03-2015, 03:19 PM

So I have a new relay, but just barely touching it causes pump to shut off. I've messed with the tabs a bit without much success. Is there a trick I need to know?

also, three relays to the left of the fuel pump is a relay that clicks constantly. I don't have a correct chart for a 79 - what does this relay do, and why is it always clicking?

Thanks!

deserttoad · 06-04-2015, 03:52 AM

Update: seems that when I was putting the relay in, I was actually pushing two wire connectors out the back of the panel. So I had to install the wires onto the relay from the back of the panel. This also stopped all the twitching of the other relay. Hope this helps someone else down the road.

stepson · 06-04-2015, 07:36 AM

DT,
There are several instances I have heard where folks were selling a non-running 928. A knowledgeable 928 buyer arrived, paid the money, reconnected the terminals of the fuel pump at the Central Electric panel, and drove the car away.

Sorry I didn't see your post last night to save you some grief, but glad you figured it out.

Don't be cowed by the TB/WP job. Timing belt/water pump for an older car is not a big deal. Is the WP leaking? or do you just not have history on it and therefore want to replace it before you have to?

Remember: On your MY 928, even if the TB snaps in 2 pieces, you have a non-interference engine. It generally won't hurt your engine and all you have to do is retime the cams to the crank and restring a new TB.

When you really get ready to do your TB, find Dwayne's write-ups on doing the TB/WP. There are lots of pictures and he explains it really well. Post here with any questions and there are folks that will help you through it. Take pictures. (Note: the only thing I'm not sure of is if Dwayne did a write up on a 16 valve engine, which is quite a bit easier than 32 valve, but has some different quirks to the process)