924Board.org

[Fifty50Plus]

Last week I swapped my fuel distributor (0 438 100 065) with a supposed rebuild (same number). I turned on the fuel pump on the race car and the replacement distributor immediately started pumping fuel into the #3 cylinder.
I almost hydro locked the engine before I discovered the issue. I pulled all the fuel lines from the injectors and put them in containers. I then turned on the fuel pump again and the distributor started flowing freely through the #3 fuel line but none of the others. When I pulled the bad fuel distributor apart, I did not see any of the rubber O rings misplaced on the shaft.
So I went back to my original fuel distributor and the car started and ran fine. I also ordered a fuel distributor rebuild kit for the other distributor and then rebuilt it. I put it on the car today and now with the fuel lines disconnected from the injectors, fuel is flowing freely from all four lines when I turn on the fuel pump. What gives? With the air flap closed (engine not turning over) the distributor shouldn't be allowing fuel (at least not much) to flow to the injectors. Any ideas?
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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

[morghen]

I’ve had similar experiences rebuilding a couple of distributors.
Didnt see anything wrong uppon disassembly so..no idea what i did wrong.
At one point i re-asembled the same dizzy with the same parts and it sort of worked but could not stop it from leaking.
Those failures made for a big part of the decision to go efi and make my efi kit.
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Supercharger and EFI kits
https://www.the924.com

[Raize]

It's not just the mixture screw being badly adjusted? The proper adjustment range is very small but the actual possible travel of that screw is very large.

[Fifty50Plus]

Couldn't figure it out so I put in my original fuel distributor. I left the fuel lines disconnected from the injectors and powered up the fuel pump. All the lines remained dry until I lifted up the air flap and then fuel flowed out of each line. Reconnected everything on the car and it runs fine.
I'm racing next weekend so I'm done trying to figure it out. I've rebuilt several other distributors and they all ran fine. Maybe I'll split it when I get back from the track.
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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

[Nobbi]

Hi there,

is it difficult to overhaul the fuel distributor? I have a blocked cyl.1 outlet on mine.Not much fuel coming out and the car runs poorly.
I have seen several videos on YT, but here and there i miss some infos.Is it neccesary to measure some outer srews to locate the position?
Do i need to adjust the co screw after rebuild?

What have you done?

Thanks,

Nobbii
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NA 924 - april/1977- 4-speed-audi gearbox.
500.000 km with fun.....and new toy:Porsche 944 S2 Cabriolet.Other car Daimler c-class cabby,brandnew..Plus : DEUTZ 4005 tractor Built 1969

[Fifty50Plus]

Every time I rebuilt a fuel distributor, I split it, kept the four little springy things with caps separated so that they go back in the same location, removed all the rubber O rings, cleaned the filter on the large shaft (if there is one), and checked that the halves of the distributor are totally clean. I spread some sealer (with a razor blade) on both sides of the stainless steel gasket, replace all the rubber O rings, insert the large shaft into the bottom half of the distributor (ensuring that the smaller shaft inside of the larger one moves smoothly), put the four springy capped things back in the top, lay the stainless steel gasket on 1/2 of the distributor (making sure that the very tiny hole is correctly positioned and not clogged by sealant), and then bolt the top and bottom of the distributor together. There is a bolt on the bottom side that has a spring, possibly some shims and a tiny O ring on the end of it that also needs replacing. I believe the shims are to increase or decrease the fuel pressure a bot but I've never changed or added any shims.
This is all from memory but I don't think I've forgotten anything.
If you are reusing your present fuel distributor I don't think you need to make any CO changes with the 3 mm tool but You can try slight changes with it up and down to see how it affects idle speed.
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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

[Nobbi]

Thank you for your quick answer ! Btw.i am 60 Plus.....
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NA 924 - april/1977- 4-speed-audi gearbox.
500.000 km with fun.....and new toy:Porsche 944 S2 Cabriolet.Other car Daimler c-class cabby,brandnew..Plus : DEUTZ 4005 tractor Built 1969

[morghen]

Hey Nobbi,

I know you're an all original type of guy, but if you ever decide to upgrade your 924, check out my website and how my kit looks for the 924.
You can keep the H plate and of course no problem with TUV, a few 924s in DE using my kit nowadays.
Since we are both on this board since many years and we actually met in person back in 2008 at the Nurburgring, it would make me happy to know many years after, your 924 gets to be a bit better and live longer with my support.

[Nobbi]

Hey morghen,

yes time went on...2008! Long time ago, but i still remember it well.We had a good time on the ring.
I am watching your developments over the years and it is great to see how many effort, money and time yous pend on the" lifetime 924 project".
I fi cant get it running again with K-Jet, ill check your solutions...

schöne grüße aus Deutschland

Nobbi
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NA 924 - april/1977- 4-speed-audi gearbox.
500.000 km with fun.....and new toy:Porsche 944 S2 Cabriolet.Other car Daimler c-class cabby,brandnew..Plus : DEUTZ 4005 tractor Built 1969

[Raize]

[Nobbi]

Hello Raize

these spring seat adjustment screws on the later ones were a great idea.

Question: Does that mean you can adjust the fuel delivery from the outside of the dizzy? If so, could you share a picture?

Thank you,

Npbbi
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NA 924 - april/1977- 4-speed-audi gearbox.
500.000 km with fun.....and new toy:Porsche 944 S2 Cabriolet.Other car Daimler c-class cabby,brandnew..Plus : DEUTZ 4005 tractor Built 1969

[Mclaren924]

Nobbi I think your 77 car wouldn't have the adjustment screws, I believe that started in 80 in US cars. Not sure about ROW cars. Currently having FD woes on a customers martini car and got lucky that my buddy had hoarded 5 or so and only ONE was good.
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1980 931 "Salt" Bucket wannabe racer (Dreaming)
1979 924 Sebring "Pepper" -Sold
1977 924 Slicktop "Pennie"-Most likely parts
1979 3/5 gt clone 924- Shop Test Car

[Beartooth]

I bet those adjustments came in with the switch to aluminum FDs, replacing the earlier iron ones. The iron FDs will be black if they have the original finish, which has probably flaked off of some, in which case you'd expect some surface rust. I've never worked on one, but I can only assume they used shims and/or an assortment of springs to calibrate them, which would have been a big time suck even with all the right equipment because it would mean at least one disassembly and reassembly every time a FD came off the line out of spec. That would be another advantage of the later FD, although calibrating one yourself is pretty daunting. My 931 runs fine after I rebuilt it, so I haven't touched them. It would be dead simple to adjust them: just remove the plug, and then clockwise adds fuel, counter-clockwise reduces on the set screw below.

I've tinkered with it on a KE FD, and it was a big hassle because with the plugs removed, the set screws pour out fuel - so you can just run the fuel system and adjust one by one until you get a certain flow. I'm not positive the k-jet FDs will also leak fuel with the plugs removed, but I assume they would. Next, determining flow is pretty difficult. Since KE has a set screw and o-ring at the base of the plunger, I used that to over-adjust it until I was getting approximately a drop of fuel per second - BUT, even there, it's hard to be sure you're measuring accurately. I found that the injector end of the line would drip at a different rate if it was pointed straight down (similar to where it'd be when connected to the injector - on a 931 at least) vs. at an angle. To hopefully overcome that, I cut some fuel line at a 45 degree angle and put it on the end of the injector line, which I think made things more consistent.

That said, if you're getting the impression that there's no way to do this accurately without a precise flowmeter - short of running a lot of fuel through the FD into a graduated beaker (which would take 10 minutes per line, and have to be repeated a few times most likely) you're getting the same idea as me. Never one to give up on a job "for the professionals," I've heard of and am trying to track down a flow meter that's supposedly precise enough and isn't ridiculously expensive ($200-300 was the price I remember being given). Bosch, back when, spec'd some very precise equipment and would put each FD on a bench with a flow meter on each port to calibrate it; I don't remember a number, but the cost was astronomical. Of course, being able to quickly and accurately calibrate each unit offset that, considering how many thousands of FDs they turned out.

For a DIY setup, my plan (if I can get an accurate flow meter) would be to set up a test bench where I gang all the lines together to the flow meter with a shutoff on each port. Then I could quickly get an accurate reading by shutting off each individually and doing some quick math. This is more personal indulgement and maybe a service I offer down the road - I only mention it to give an idea of what's involved in actually calibrating a unit. On the other hand, you do have a decent chance of putting a kit in and having it come out serviceable (possibly as good as the day it left Bosch), assuming you can keep the springs and pieces in order and get everything back together right. There's not a lot of investment required to "kit" a FD, and you can always waive the flag and send it in if it comes out wrong. Hard to argue for it economically though; there's a reason most shops would't dream of opening one up. So just bite the bullet and send it to someone if there's any question. Flowtech is the only one I know for sure can do it right, but I haven't been impressed with the longevity of their rebuilds - one died on my and I was able to bring it back to life, the next died as well, and I'm still trying to figure that one out. They won't respond to queries or grant any kind of allowance outside of warranty - and their warranty (frankly) sucks.
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1980 931 diamond in the rough