924Board.org

Fifty50Plus · Posted: Wed Jul 26, 2023 5:20 am Post subject:

Vaughan,
The only fitting I was able to buy was at the top of the fuel distributor. Every other conversion fitting I made was cut and splice via silver solder. It has worked for a year now but.... Maybe Beartooth's find (www.fittings.space/) has some others that help out but it's not a slam dunk. Hell, look what Porsche did to mount the Audi transmission to the back end of the 924

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1979 924 NA race car
1982 924 NA race car - Sold
1982 924 Turbo almost a PoS
1981 924 Turbo a real PoS, new engine
1982 924 Turbo nice body, blown engine
1972 911 E race car - going to Vintage
Various 944s to become IT-S race car

Beartooth · Joined: 05 Apr 2022 Posts: 206 Location: Roberts, MT

That's pretty funny, Bosch's attitude towards meddling with "their" components. I have to wonder if they think failure is supremely unlikely and modifications are just foolish (you're messing with perfeciton), or if they think the number of amateurs who could successfully correct a problem or modify the system is so low it's negligible. On KE-jet Mercs (and possibly most or all KE-jet applications) the idle CO adjustment had a BB pressed into it to keep it from being tampered with; per the FSM, if an adjustment had to be made, the service center had to drill out the BB, then press a new one in after the adjustment had been made.

Anyway, I also had the thought of welding or soldering to create what I need, but it's far beyond my welding equipment and skills, and even if I had what I needed, I'd be a little concerned about it going wrong and creating a leak down the road. What I might try is using a tubing bender to modify the original metal lines and replace the flexible (polyamide) segment, which would allow for length adjustments. I found a source for the polyamide line (and some fittings) digging through old threads: https://www.partsklassik.com/c-12-fuel-system.aspx. So it should be possible to modify the original lines and re-use them to relocate the WUR. Apparently it's not DIY-friendly though; possible if you're willing to build some tools to hold the lines, but not easy.
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1980 931 diamond in the rough

BWW · Joined: 21 Sep 2021 Posts: 58 Location: Idaho, USA

Thanks for the ideas and the link, Beartooth! I don't have the skills or equipment for welding either, but is there any reason one couldn't have a bracket welded in the fender well area in front of the battery? Or maybe even just drill a couple of holes and mount it in the metal wall directly in front of the battery? It would be on the same side as the CIS on the 931, so you wouldn't need super long fuel lines.
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Brent
'81 931 project car

BWW · Joined: 21 Sep 2021 Posts: 58 Location: Idaho, USA

Hi all. I'm resurrecting this thread to ask a quick (I hope) question. Finally got some time to get back on the car and do some testing. I'm trying to get the system pressure dialed in before moving on to the WUR. I jumped the fuel pump relay connector and the pressure gauge kept moving up until it got to about 30 psi/2 bar. At this point there was a small popping sound from the fuel distributor and the pressure dropped down to about 17psi/1.2 bar and the cycle repeated itself until it got to 30 psi/2 bar again, after which the cycle started all over again. The fuel distributor temp was about 55 F/12.5 C. Is it normal for this to happen? Thanks in advance for any help. Hopefully someday I will be able to give back to this group.
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Brent
'81 931 project car

Fifty50Plus · Posted: Mon Nov 13, 2023 10:36 am Post subject:

Definitely not right. Popping noise in the fuel distributor....

I'd look at rebuilding that before anything else.
_________________
1979 924 NA race car
1982 924 NA race car - Sold
1982 924 Turbo almost a PoS
1981 924 Turbo a real PoS, new engine
1982 924 Turbo nice body, blown engine
1972 911 E race car - going to Vintage
Various 944s to become IT-S race car

BWW · Joined: 21 Sep 2021 Posts: 58 Location: Idaho, USA

Ugh. That’s not encouraging. I already rebuilt it once, but admittedly I’m an amateur with these things. Chuck, would you recommend a professional rebuild at this point?
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Brent
'81 931 project car

Beartooth · Joined: 05 Apr 2022 Posts: 206 Location: Roberts, MT

Could the popping noise be from air bubbles working their way through the FD? I can't imagine anything else causing it. I've found the FD to be fairly foolproof as long as you put it back together the way it was intended, and there are only a few things that can go back together wrong. I'd take it apart and look for anything amiss; it wouldn't hurt to dig through as many rebuild instructions as you can find too, just in case there's something you missed. Really, as long as it goes together properly, the only advantage of a "professional" rebuild is the calibration. The instructions I've got involve checking and matching the depth of the set screws under the little cap screws, which is potentially garbage in, garbage out, plus whatever error is introduced. That said, I suspect if you can measure the injector outputs accurately enough, you can calibrate it as well as anyone.
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1980 931 diamond in the rough

BWW · Joined: 21 Sep 2021 Posts: 58 Location: Idaho, USA

Thanks, Beartooth. I was thinking about it last night, and I'm thinking that the cause might be the pressure regulator. This was what seemed to have been causing my initial issues with the FD (a pinging sound upon acceleration, then stalling out). When I did the first rebuild, the piston was stuck solid. It's unstuck now, of course, but it might be doing other wonky things. I will do some experimentation and see if the popping goes away. Thanks again! Eager to get this thing on the road, though that still seems far away.
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Brent
'81 931 project car

BWW · Joined: 21 Sep 2021 Posts: 58 Location: Idaho, USA

(Which is not to suggest that another tear-apart and rebuild is not still in order; it very well may be.)
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Brent
'81 931 project car

Fifty50Plus · Posted: Tue Nov 14, 2023 8:58 am Post subject:

Lots of folks here have attempted to rebuild the FD. Care installing the new rubber seals and a proper very thin application of Loctite 542 on the metal gasket is all that is needed.
Popping noise....sticking piston. Sounds possible. If stuck you get no fuel or too much fuel.
_________________
1979 924 NA race car
1982 924 NA race car - Sold
1982 924 Turbo almost a PoS
1981 924 Turbo a real PoS, new engine
1982 924 Turbo nice body, blown engine
1972 911 E race car - going to Vintage
Various 944s to become IT-S race car