Mixture setting

[Mike1830]

Today, i noticed after removing my fuel distributor that the plunger is jammed in the full load position. After looking at the mixture screw, i found that it is screwed almost all the way down, with maybe 2-3 threads showing at the top. Ive seen diagrams and pictures of the mixture screw and was wondering if this sounded normal to be screwed down that far considering that screw is almost 3/4 of an inch long. Im guessing this is why i found gas in the oil pan?

Im not at a point right now to fire the motor due to being in the process of replacing all of the fuel lines, filter, pump etc.

The hole for the mixture screw has the gold colored rod with the rubber plug in the hole. I read that these originally came with an anti tamper plug if im not mistaken.

[dmcnc]

Only way to know if your screw is in the right position is to reset it. Once your system is reinstalled and you can get fuel to your FD, bridge the fuel pump relay (pins 30 & 87) and watch for fuel coming out of the injector line outlet ports of the fuel distributor. The mixture screw (3mm Allen Key) is between the fuel distributor and the air flap.

If fuel is rising out of the injector line outlet ports, rotate the mixture screw, with a 3mm Allen key, anti-clockwise until the fuel just stops rising. Wipe the injector line outlet ports and watch to see that it has stopped flowing. Turn the mixture screw anti-clockwise a further 45 degrees. This should give you a basic starting point for setting the correct mixture.

[Ron]

Only way to know if your screw is in the right position is to reset it. Once your system is reinstalled and you can get fuel to your FD, bridge the fuel pump relay (pins 30 & 87) and watch for fuel coming out of the injector line outlet ports of the fuel distributor. The mixture screw (3mm Allen Key) is between the fuel distributor and the air flap.

If fuel is rising out of the injector line outlet ports, rotate the mixture screw, with a 3mm Allen key, anti-clockwise until the fuel just stops rising. Wipe the injector line outlet ports and watch to see that it has stopped flowing. Turn the mixture screw anti-clockwise a further 45 degrees. This should give you a basic starting point for setting the correct mixture.

Correct me if I'm wrong but, I don't think it is a good idea to pressure up the system with the injector lines disconnected. Seems fuel would go everywhere even if his is not as far off as he thinks it may be..
???

=======

Not sure if you mean the plunger is seized in the up position or not... Just in case:
When the engine is running there is fuel pressure pushing the plunger down, which pushes the plate up. When you shut it off some pressure remains for a while. If someone presses the plate down, the plunger will go up (and the plate will flop when you tap on it). If the plunger stays up and sits for a long time, it may seize in that position. It may be that the adjustment screw is OK.

Running the CO screw down (CW), makes the plunger go up and the A/F richer. As you suspected, if it is was stuck up, the engine would start to flood as soon as you turn the key on. Definitely a source for oil contamination (and washed out rings).

You could rough in the CO screw as follows:
Have fire extinguisher ready.
When everything else is together, put the injectors in a container. Jump the RPM Relay (http://dmctalk.org/showthread.php?1155-How-To-Jump-the-RPM-Relay) and watch the injectors while someone turns the key to ON only. If they spray, turn the screw (CCW) just past enough to make them stop when you remove the wrench. The CO screw will then be roughed in.

You are correct on the gold and anti-tamper plugs.

[Mike1830]

Not sure if you mean the plunger is seized in the up position or not... Just in case:
When the engine is running there is fuel pressure pushing the plunger down, which pushes the plate up. When you shut it off some pressure remains for a while. If someone presses the plate down, the plunger will go up (and the plate will flop when you tap on it). If the plunger stays up and sits for a long time, it may seize in that position. It may be that the adjustment screw is OK.

Running the CO screw down (CW), makes the plunger go up and the A/F richer. As you suspected, if it is was stuck up, the engine would start to flood as soon as you turn the key on. Definitely a source for oil contamination (and washed out rings).

You could rough in the CO screw as follows:
Have fire extinguisher ready.
When everything else is together, put the injectors in a container. Jump the RPM Relay (http://dmctalk.org/showthread.php?1155-How-To-Jump-the-RPM-Relay) and watch the injectors while someone turns the key to ON only. If they spray, turn the screw (CCW) just enough to make them stop when you remove the wrench. The CO screw will then be roughed in.

You are correct on the gold and anti-tamper plug.

When i say frozen i mean it will not budge at all. There was definatley a bunch of gas in the oil. I just spoke with the previous owner yesterday. I asked him about when he last drove it. He said it ran fine and pulled it into the garage in 2003 where it remained due to health issues.

[Michael]

"Ran fine when parked."

Famous last words

[DMCMW Dave]

When i say frozen i mean it will not budge at all. There was definatley a bunch of gas in the oil. I just spoke with the previous owner yesterday. I asked him about when he last drove it. He said it ran fine and pulled it into the garage in 2003 where it remained due to health issues.

2003 is 16 years ago!! Any fuel in there has turned into varnish (aka glue). Yeah, it's stuck. Wide open. Which is why there is gas in the oil if you've been trying to start the car.

You can adjust the mixture screw all you want and it's just going to keep flooding the engine. Get the plunger unstuck, or get another fuel distributor, before you go any further.

As for how to set it, I would recommend the opposite of the initial post. Back the screw all the way out (don't force it, there is a stop). With the injectors attached and pointing into jars, turn the screw clockwise until it just starts to flow thru the injectors and then back off until it just stops. This should run the car. Using the method given, if the screw is really way to far in, you'll probably spray fuel all over the engine. If there are any loose or bad plug wires, you'll set it on fire.

[Mike1830]

I found the gas in the oil before i ever even hooked up a battery to the car. The fuel pump is also dead so when i was cranking it, nothing was being pushed through. Im in the process of ordering everything to rebuild the fuel system and have the FD rebuilt or replaced.

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[Mike1830]

2003 is 16 years ago!! Any fuel in there has turned into varnish (aka glue). Yeah, it's stuck. Wide open. Which is why there is gas in the oil if you've been trying to start the car.

You can adjust the mixture screw all you want and it's just going to keep flooding the engine. Get the plunger unstuck, or get another fuel distributor, before you go any further.

As for how to set it, I would recommend the opposite of the initial post. Back the screw all the way out (don't force it, there is a stop). With the injectors attached and pointing into jars, turn the screw clockwise until it just starts to flow thru the injectors and then back off until it just stops. This should run the car. Using the method given, if the screw is really way to far in, you'll probably spray fuel all over the engine. If there are any loose or bad plug wires, you'll set it on fire.

Also i havent touched the mixture screw. I just thouggt it was odd that for as long as that screw is that it is in that far. It appeared someone may have been in there before me given the condition of the mixture hole having wheat appears to be tooling marks from possible previous work.

[dmcnc]

Correct me if I'm wrong but, I don't think it is a good idea to pressure up the system with the injector lines disconnected. Seems fuel would go everywhere even if his is not as far off as he thinks it may be..
???


The procedure I mentioned was strictly for reseting the Fuel Distributor once everything else was addressed (loose plunger, system hooked up, etc) - apologies for not clarifying.
Here are some references for this procedure:
http://www.cisflowtech.com/frequently-asked-questions/testing-k-jet/k-jet-mixture-setting/
https://k-jet.biz/fuel-distributors/
http://www.type17.ch/downloads/Injection/Bosch%20-%20K-Jet%20-%20Workshop%20Manual.pdf (Page 32)

[Mike1830]

Not a problem. Thank you for all the info.

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[Ron]

The procedure I mentioned was strictly for reseting the Fuel Distributor once everything else was addressed (loose plunger, system hooked up, etc) - apologies for not clarifying.
Here are some references for this procedure:
http://www.cisflowtech.com/frequently-asked-questions/testing-k-jet/k-jet-mixture-setting/
https://k-jet.biz/fuel-distributors/
http://www.type17.ch/downloads/Injection/Bosch%20-%20K-Jet%20-%20Workshop%20Manual.pdf (Page 32)

NP!
Other good info on those sites!

FWIW- They don't agree on the procedure (one vs all lines off, number of turns, etc.) but get the job done. Main thing to me is they were written to be followed after a FD rebuild and probably assume the screw hasn't been tampered with.
And as the first link says, "This is the Bosch recommended procedure for initial mixture setting and adjustment." Not the initial setting for the mixture screw.
Anyway, I have it somewhere and will dig it up and post it as soon as the hectic holidays allow, for prosperity.
:cheers:

[Andy_]

I know this is an old thread, but i was trying to reset the fd today. I?ve seen some posts here saying go counter clockwise until the injector ports stop rising, and then reduce it half a turn (which i took to mean 180 degrees).
Here,
https://k-jet.biz/wp-content/uploads/2020/08/001-Refitting-Fuel-Distributors.pdf
It says to stop the ports rising, then reduce by 15 degrees.
Should the car roughly start using any of these numbers? 15/45/180 ?
Mines 99% trying to start, almost running. Runs for half a second.
Ive just replaced the wur which was causing backfires etc.
to be honest i only had 1 injector hose removed so will remove all and check theyre all filling at the same point.

[Bitsyncmaster]

I know this is an old thread, but i was trying to reset the fd today. I?ve seen some posts here saying go counter clockwise until the injector ports stop rising, and then reduce it half a turn (which i took to mean 180 degrees).
Here,
https://k-jet.biz/wp-content/uploads/2020/08/001-Refitting-Fuel-Distributors.pdf
It says to stop the ports rising, then reduce by 15 degrees.
Should the car roughly start using any of these numbers? 15/45/180 ?
Mines 99% trying to start, almost running. Runs for half a second.
Ive just replaced the wur which was causing backfires etc.
to be honest i only had 1 injector hose removed so will remove all and check theyre all filling at the same point.

Just adjust it to get the injector to just stop spraying. The car should start and run there. Then use the dwell meter to finish the adjustment on a hot engine.

[MrMac4800]

This was documented at Bosch back in the days and used in the workshops:

71242

Google Translator:
?Bridge the electrical safety circuit (see vehicle-related test and repair instructions).
Turn in the mixture control screw slowly without applying pressure to the adjusting key until fuel is just being delivered to the open outlet (arrow) of the flow divider. Then turn the adjusting screw back ? turn.
Reconnect the fuel line to the flow divider, start the engine and warm it up.
Make the final assignment by adjusting the idle speed according to test section 12 and according to the values ​​on the test value sheet.?

Worked perfectly for me after i got my WUR and Distributor rebuild.