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[UhmWhat]

Sort of an update

I changed the spark plugs, oil and coolant but no start. when I was last with the car I had noticed a lack of noise from the fuel pump. What I'm doing now is waiting for a chance to go see the car again to test if maybe my stupid self did the wiring wrong on the pump or see if maybe its jammed. I have a lot on my plate with graduation soon so until then i probably wont see the car but after that I will have a lot of opportunities to go work on it.

For now i just need to ask a few questions:

1. can the fuel pump be cleaned out
2. if I were to say buy a huge spool of vacuum lines so I can cut sections to replace all my dry rotted tubing, what diameter line do I need?
3. what's the easiest way to clean the fuel tank without having to remove it from the car
4. is there a way to test if the car runs like they do with old carbureted cars by like spraying starter fluid in or is that just not something you can do on a fuel injected car?

Thanks

-Uhmwhat
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5-Speed 81' 924

[Cedric]

[Beartooth]

The place to start with the fuel pump is to see if it's drawing current. Ideally, you want fuel in it, so it's probably best to do it with it in place. I'd disconnect the wires an apply 12V to the terminals (make sure any fuel leaks are taken care of and it's dry, and have a fire extinguisher handy) and see if you get a spark and a little tick sound. If there's no sign of it taking current, then you can stop there. There's some kind of internal fuse on these pumps that I've found will blow if it gets gummed or runs dry up and you apply power long enough. In my case, my pump would draw current and I think I could hear the sound of something trying to move inside, so poured every kind of fuel system cleaner I could think of in it, but never was able to get it to break free. After hours of mucking around on it, that internal fuse finally blew, so I picked up a new pump. There's a good chance your in-tank pump is shot, and those are stupid expensive, but another option is to switch to the fuel stainer used on several later Porsches (part number 92820108104). It's about $80; the in-tank pump is almost $1000!

With the vacuum line, you can order metric vacuum line, but I couldn't tell you offhand what sizes and how much. The other option would be to measure the lengths you need and cut pieces of each size and go to NAPA or wherever with that and buy the closest size. For now, I wouldn't worry about the crankcase vent lines, and I think with the line going from the charcoal canister to the intake (just below the air sensor plate) you'd be best just to cap it for now.

When I was initially trying to get my car started, I drained the tank, then cleaned whatever debris out of the sump that I could by hand, then poured some fresh gas through the filler (with the bottom of the tank where the fuel pump goes open) just to flush out anything loose. The best thing, especially if the tank is badly rusted or gummed up, would be to drop the tank and clean it out, but that might be impractical, and hopefully not necessary if it's not in too awful shape. Mine's not badly rusted, so I plan on driving it a bit and then cleaning or replacing the fuel strainer a few times; if I have issues or it keeps plugging up, then I'll drop it, but for now... One thing to keep in mind, if the tank is really bad, there's a good chance you'll keep having issues and probably burn up a fuel pump until you address it.

You can try starter fluid just to see if you can get it to pop and run a few turns, but I wouldn't go any farther than giving it a spray, then cranking it. You might get it to run continuously by pulse spraying down the intake, but there's a possibility you'll back-fire and maybe even create a fireball. You can often run an engine with no fuel supply by trickling gas into the intake, and that's safer than starting fluid, but I wouldn't call it safe... It's sort of fun, I suppose, but definitely risky. A compression check will give you a good idea of whether you've got major mechanical issues. Whatever you do, one thing to look for is making sure you've got oil pressure. I noticed I wasn't getting any, even with repeated cranking, until I took the oil pressure relief valve apart and sucked some oil up the line. Just cranking mine now, I get oil pressure within about 10 seconds, just to give you an idea. It won't hurt anything to crank it over to your heart's content (other than maybe the starter, but that's not a big/expensive deal) as long as you have oil pressure. On the other hand, you could chew up the crankshaft bearings by cranking dry, and teh bearings themselves aren't cheap or easy to come by. Not to mention how much work it is to replace them...
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1980 931 diamond in the rough

[UhmWhat]

[UhmWhat]

[Beartooth]

Don't feel bad about the oil pressure, I didn't think of it initially either. I cranked mine over several times before I got the oiling issue sorted (I did pour oil over the cam, but obviously that doesn't do anything for the bearings). I think the oil pressure gauge is electronic; Ihaven't looked into it myself since it seems to work. If you take the valve cover off and have somebody crank it over, you should see oil dribbling on the cam lobes if it's pumping. If it's not, it's probably just because the pump lost its prime, which was my case. As long as it's pumping oil though, you're good for the time being.
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1980 931 diamond in the rough