ULpilot

I have picked up a 86 928 with a rough history. It spent a few years under a tree and in the dirt until we picked it up several years ago. We drove it home, though it had some minor (unrelated to this, like alarm) problems.My dad went down past the valve covers to clean up the top of the engine (I think he wanted to see what it was designed like as well). He reassembled it and went to start.... and it turns over fine but doesn't catch. Unhooked fuel lines and there is nothing at all.
I've followed a lot of the checks for electrical problems with the fuel pump. Tonight I bridged the relay with a wire, it made a click noise (not real loud, also it wasn't a hollow sound, very solid click). And then no noise. I went down by the fuel pump, watching it, looking at wires (red to positive, brown to neg, and that's it, right?). Then I noticed a vapor (smoke?) coming out of the output side. Ran up and unhitched the bridge, which was warm.
The sound seemed like an electric motor which was jammed- I especially conisdered this after reading "The hose between the pump and the outlet comes apart and a piece will get into your outside the tank pump and cause it to jam. Sometimes you can reverse the wires on the outside pump so it will run backward and spit out the debris.". Does this sound like the case? I have all fuel lines on both sides of the pump unhooked. Can I just reverse the lines and try to spit it back out? Blow it out? Or is the fuel pump bad and do I need to replace that? Or does this sound fit with an electical problem....there is absolutely no sound after that one click. I have the manuals, and a multimeter..... unfortunately in the middle of upgrading to a new garage and I'm not exactly sure where right now. I'm an MG guy, this is more complex than anything I've touched before. I don't want to mess it up.
Thanks in advance,
Simon

G Man

Is there voltage to the pump? I assume there is since you indicate that it is making a noise like it is locked up. I would remove the pump from the car and try to reverse the connecton away from the gas tank. We don't want to have any accidents! Maybe you can spray some cleaner in there to loosten up any crud that may be there. It might be a good idea to pull the tank and flush it out to make sure there is no crud waiting to get into the pump once you get it sorted out. Did I mention installing a new fuel filter too?

jebdog

The 86 has only a single pump remove from the car and test by reversing polarity but only run for a few seconds the pumps are cooled and lubricated by the fuel running through them. Grounds and relay often are problems as well as the crank reference sensor on the back of the engine. Since your dad "took it apart and put it back together" the potential problems are nearly unlimited because I doubt he had access to the factory workshop manuals. If the car has factory alarm that may be triggered and preventing it from running. You need fuel spark and compression for it to run check all the above. The common failure mode of the LH injection computer is failure to turn on the relay for the fuel pump. Generally speaking you go back to what you did to it just before it stopped running.

ULpilot

Thanks a lot! I did take it off and it did seem jammed. While trying to do this I accidently dropped it off the table, and then it started working! Made sure it will work a bit more consistently, I guess there was something stuck in there. Put it back in the car and it didn't work. I bypassed the relay again and it works. SO I guess a combination of 2 problems! Thanks for the QUICK responses, it was great!
-Simon

Bill Ball

Drop the relay off the table.

Jim bailey - 928 International

Bill that was COLD !

Imo000

When i picked up my '86.5 project car, that sat for 6 years, the fuel pump was also siezed. I went to the local Porsche wrecking yard and bough a replacement pump. They had to test at least half a dozen before we found one tha tworked. I think these pumps have a tendency to sieze up if they are old and dry. Make sure you also replace or at least flush out the fuel filter before attempting to start the car for the first time.

Bill Ball

CWO4Mann

I just finished "doing" my fuel system at the rear (working my way forward in restoration). I removed the pump and made a circular rubber tube arrangement and ran the intake and out-flow into a bucket of kerosene. I bashed the pump a few times with a rubber mallet while it was hooked up in reverse (positive to negative, etc). I ran it 24 hours continuous pumping kerosene in reverse, then turned the connections around and ran it 24 hours forward. The pump runs very quietly now and the filter I made up for the pump around clean out (a lawn tractor filter from Home Depot) showed total rusty red. The second filter (they're cheap) does not even look dirty. This may seem like tough love but I didn't want to buy a new pump.

Remember that if your tank was open to the element (as mine was without a cap for several years) the inside might look like this:

HTH

SharkSkin

Then what, drop the shark off the table?

Bill Ball

Ultimately, that may be the right thing to do.

ULpilot

Ok, so maybe it isn't fixed. Before getting a new relay I hooked up all the fuel lines and put in the starter (same type) relay in its place. Turned the key to the normal 'run' spot, and nothing happened. I checked the fuse, it is ok. Remember, with the system all set up I jumped the relay and it worked. I put the old fuel pump 'bad' relay in the starter slot- turned the key to start to see if that relay was good. The engine turned over ok- and the fuel pump kicked in while it was turning over. I have NO coolant in it right now (see thread on removing radiator that I will soon post if I can't find anything on the search). So I really didn't want to let it turn over enough that it could catch. But from the couple seconds I do let it turn over- I can definitely hear the pump running.
Is it supposed to do this? There wasn't any fuel in the lines- so I'm doubting that it just stops becuase it gets up to pressure until I start to suck some in. Any thoughts?
I'm confused
Thanks again,
Simon

Jim bailey - 928 International

The fuel pump only runs when the starter is cranking or the engine is running it does NOT run in the run position if the engine is not running.

ULpilot

THANK YOU THANK YOU THANK YOU
That made my day a whole lot better. So relieved to hear that! Now, on to the other 100 problems. Maybe dropping the entire car off the table would help ;-).

Jim bailey - 928 International

When the engine is running the fuel pump runs all the time and the excess fuel is returned to the tank by the hose on the fuel level sending unit on top of the tank body. Do not run the pump dry it needs fuel to cool and lubricate it.