Mixture base setting

[Michael]

I'm going to look at a non runner in a few days. They have done a lot of work to it and they want to put on a FD next. I am going to poke around on it and one of the things I want to check is the mixture. Does anyone know how many turns gets you close? In other words, can I tighten it fully, back it out say 7.5 turns and be in the ballpark enough that it will start and run long enough to go into closed loop?

[dn010]

I'm not sure if there is a way to count turns to get close but I did once read somewhere that you jump the RPM relay to keep the fuel pump running, pull a few injectors and turn the screw until it just stops spraying fuel. I can't remember if it was from a Volvo manual etc. but I did use this method and it worked for me.

[dmcnc]

^pretty much what he said:

After assembly of the fuel system, run the fuel pump and depress the air flow sensor plate for a couple of seconds to bleed air out of the fuel distributor. Remove one injector line from the top of the fuel distributor, and while looking into the injector port in the top of the fuel distributor turn the mixture adjustment screw clockwise until the port just starts to fill with fuel then turn the mixture screw 1/2 turn counter clockwise. Reinstall the injector line, start the engine and adjust mixture when it reaches operating temperature. This is the Bosch recommended procedure for initial mixture setting and adjustment.
Ref: Bosch K-Jet Mixture Setting

[Ron]

I'm not sure if there is a way to count turns to get close but I did once read somewhere that you jump the RPM relay to keep the fuel pump running, pull a few injectors and turn the screw until it just stops spraying fuel. I can't remember if it was from a Volvo manual etc. but I did use this method and it worked for me.

THIS!

^pretty much what he said:

After assembly of the fuel system, run the fuel pump and depress the air flow sensor plate for a couple of seconds to bleed air out of the fuel distributor. Remove one injector line from the top of the fuel distributor, and while looking into the injector port in the top of the fuel distributor turn the mixture adjustment screw clockwise until the port just starts to fill with fuel then turn the mixture screw 1/2 turn counter clockwise. Reinstall the injector line, start the engine and adjust mixture when it reaches operating temperature. This is the Bosch recommended procedure for initial mixture setting and adjustment.
Ref: Bosch K-Jet Mixture Setting

This doesn't seem right to me??

Removing an injector line at the FD can spew quite a bit of fluid from just rest pressure.
With the key on or the RPM Relay jumped, things could get exciting.
Or am I missing something??

$.02
Watch the for the injector(s) to fire. Then barely nudge it CCW (1/2 turn is too much).

[dmcnc]

It's exactly what I did when I installed a new FD, with no issues. This is the procedure for resetting a new FD so there is no rest pressure, at least not until after the procedure.

THIS!




This doesn't seem right to me??

Removing an injector line at the FD can spew quite a bit of fluid from just rest pressure.
With the key on or the RPM Relay jumped, things could get exciting.
Or am I missing something??

$.02
Watch the for the injector(s) to fire. Then barely nudge it CCW (1/2 turn is too much).

[dn010]

run the fuel pump and depress the air flow sensor plate for a couple of seconds to bleed air out of the fuel distributor.[/URL]

This is the procedure for resetting a new FD so there is no rest pressure

If I am not mistaken, running the pump and pressing the plate will get you pressure in the fuel distributor.

In my quick search of any K-jet related vehicle manual I have, it doesn't say anything other than "...it's set from the factory" and then gives adjustment procedures. Another quick search here brought this up:

http://dmctalk.org/showthread.php?16116
Keep your new copper washers at home and go with Dave Swingle's advice. This is exactly what I did probably 5+ years ago even before this post so this information must be floating around somewhere in the D community.

[Ron]

It's exactly what I did when I installed a new FD, with no issues. This is the procedure for resetting a new FD so there is no rest pressure, at least not until after the procedure.

Now I'm confused-
Where is the pressure filling the port coming from during this procedure??

I only mentioned the rest pressure because we've seen how much that will leak when a banjo breaks, etc....To compare with the pressure that procedure uses to "...fill with fuel then turn the mixture screw 1/2 turn counter clockwise".
It doesn't say whether to use the key or relay, but since it is not gravity feed at all, you'd about have to use one or the other to get it to fill. There could be ~4 Bar of pressure there. No?

If I am not mistaken, running the pump and pressing the plate will get you pressure in the fuel distributor.

That will get you fuel out of the injectors. No need to press the plate -- The FD would fill (and pressure the plate up) anyway.

In my quick search of any K-jet related vehicle manual I have, it doesn't say anything other than "...it's set from the factory" and then gives adjustment procedures. Another quick search here brought this up:
http://dmctalk.org/showthread.php?16116

Keep your new copper washers at home and go with Dave Swingle's advice. This is exactly what I did probably 5+ years ago even before this post so this information must be floating around somewhere in the D community.

+1

======

Maybe this will help:
When you activate the pump, the FD gets line and control pressure (both ~4.9 bar, depending on temp). If you do nothing else, the plate will be firm and the plunger, etc. will have the injector port pressure just below where the injectors open (~4 Bar). This is where setting the screw comes in. You simply turn the screw CCW to make sure the injector doesn't spray, turn it CW until it barely starts to spray, then nudge it CCW until it stops -- Ya want the port pressure just below the point at which the injector(s) open.
Just enough to fill the port is way too low for a base setting. (Not to mention spewing @ ~5 Bar. Or more, if you do press the plate.)

Injector port:
Rest = ~3 Bar
Pump On = ~4 Bar
Fully Pressed Plate = 120 liters/hr (min).

[Bitsyncmaster]

I would recommend you put all six injectors into jars. I guess it would then be a good idea to press the plate to purge the lines of air. Then you just turn the mixture screw until the injectors just stop leaking fuel. Of course all this is done with the RPM relay jumped.

If you leave any injectors in the engine your going to pool a lot of fuel somewhere.

[Michael]

If you leave any injectors in the engine your going to pool a lot of fuel somewhere.

Only if you continuallly press the metering plate.

Thanks all for the help. Sounds like I could get close with the advice here. I will probably just jump the relay and pull one injector line off the head to set it.

[dn010]

Only if you continuallly press the metering plate.

It depends on how far off the adjustment is. If it is off lean it won't do anything, if it is off set too rich it will drip/spray even without the plate pressed.

This is the Bosch recommended procedure for initial mixture setting and adjustment.
Ref: Bosch K-Jet Mixture Setting

Are you able to reference this from Bosch for us so we know for sure?

I've never seen any 'official' recommended procedure for setting base. You're quoting a repair website and then telling everyone - this is it - the procedure - Bosch recommended. I think we'd all feel better if we saw something from Bosch themselves stating it because it seems unnecessarily messy and dangerous as opposed to simply removing an injector and controlling where your flammable liquid goes.