Fuel Distributor help and tuning thoughts?

[OLD MAN]

So over the years:

I have collected a few extra E21/M10 parts.
I have also forgotten a lot of what I knew/learned about them.

I have a few fuel distributors and they are not all the same.

This is a picture of one of the extra FD I have - Note this one has no allen/hex head caps next to injector line bosses.

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One of my other ones has allen/hex head caps on it next to the injector bosses.

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These hex head caps have a copper washer under them meaning pressurized fuel is below them.
Also under the caps are hex head driven set screws - which I believe to be fuel flow adjusters.

Am I correct?

DSC_0033.JPG DSC_0034.JPG

Shot of the set screw on the inside.

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Questions:

Can these be used to set fuel flow to each injector separately?
Which direction is richer?
Should these be touched by me?
Can these move by themselves over the decades?

Looking forward to your answers.

[epmedia]

Hi Daryl, those are for calibration and should not be touched. Unless you know what you're doing! (I don't know the method used for calibrating them, so I can't help with that).

I don't think they'd move over the decades, by themselves that is...

[320iAman]

Can these be used to set fuel flow to each injector separately? Yes
Which direction is richer? CW
Should these be touched by me? makes no Difference if your going to volume adjust-- I took mine out and installed new o-rings on them.
Can these move by themselves over the decades? Possibly, yet the little spring tensions will change , the little o-rings on these will age, crack and break and the thin plate can get small dents in it-which will change volume to each injector.

See FAQ's- Fuel Distributor Rebuild to rebuild and re-calibrate the Fuel Distributor, I'm running a rebuilt and re-calibrated Fuel Distributor now and for some time--all signs point to good.

Randy

[OLD MAN]

Robert and Randy thank you both for your input.

Reason I asked is because my 81 is still running a bit off.

#1 plug is chalk white
#2 & 4 look a perfect light brown
#3 is a pretty light tan

Which means the four cylinders are not getting the same amount of fuel into them.

[320iAman]

Check injectors as well- I had a slight pop in one cylinder-heard at muffler-changed out injector--all good-- it sprayed and dripped-substitute one sprayed only.

Randy

[Tom D]

hey daryl,

never having worked on distributor with these screws i'm going to have to hold pause with the answers above, mostly because you do not show whats below these screws and how they might interact within the upper chambers.

from what i can make out there appears to be a grub screw below the cap screw and that grub screw might be adjustable. if that is the case and the grub screw interferes with the upper chamber's spring then yes, its conceivable that the inner grub screw is used to adjust the spring's counter-pressure being applied to the top of the diaphragm.

if there is an adjustable inner screw below the cap screw and it does interfere with the upper spring then yes i agree that it's for fine tuning fuel delivery at each injector independently.
they would do this by adding or subtracting pressure being applied to the diaphragm via the upper chamber's spring. screwing in the grub would load the spring and it's reaction would be to further load the diaphragm resulting in more fuel volume being delivered to the injector. screwing out the inner screw would result in less counter pressure against the diaphragm and a leaner condition would result.

if there is no connection between between the upper camber's spring and the external cap screw (including a internal 'grub' screw beneath the cap screw) then no, they are not used for fuel monitoring and are more likely to be an air bleed-off port, used for priming a dry system.

DSC_0036.JPG

[Tom D]

..... under the caps are hex head driven set screws ......

i did not catch this the first time i read your post, so now my question is, does it interfere with the spring?

if it does then i will agree with randy and have outlined how it works in my statement above.

[epmedia]

Hi Tom. From Josh's post #20 on the 'fuel distributor rebuild' thread...
(regarding: perch height adjustment screws)

After spraying everything out with carb cleaner. Here you can see the upper spring perches, as well as the perch height adjustment screws (the allen bolts next to the injector bango bolts). This is how counter spring pressure on the diaphragm is adjusted to calibrate the flow between each port. You can also see the valve seat for each injector:

click to enlarge
FDRebuild030.jpg

[Tom D]

thanks robert,

and there you have it. screwing in the grub screw (CW) will richen the fuel mixture and screwing it out (CCW) will lean it.

[OLD MAN]

Thanks guys - this is what I thought but I have been wrong before...

- - - Updated - - -

How about the small filter below the bango bolt, anyway to clean it in the FD while on the car?

Wondering if this could be making #1 run lean?

[epmedia]

Thanks guys - this is what I thought but I have been wrong before...

- - - Updated - - -

How about the small filter below the bango bolt, anyway to clean it in the FD while on the car?

Wondering if this could be making #1 run lean?

It definitely could, which is why I removed all mine. The little filters are more finicky about debris than the injectors.

You want to try removing it. Gentle upward twist with either torx driver or trimmed pocket-screwdriver. Use spray can carb-cleaner. Want to also (carefully) flush some fuel/debris out of the port(s) before putting the cleaned filter back in. (lots of crap get's trapped in the area under the filter)

[OLD MAN]

Thanks Robert.

[320iAman]

If you dont want to remove them(Fuel Micro Basket Filter) spray with carb cleaner thru the threaded hole and then thru the fuel pot-using the red straw with the carb cleaner--this will get the job done as well, spray a couple of times each way--since fuel is going to the injectors thru the fuel pots small holes--spraying down thru the threaded button holes most likely would be enough-- air thru the button hole will help dislodge the small particles as well--reduce the pressure though. This is with FD taken apart.

DSC_0036.JPG The Four Fuel Pots with there small holes. On the top 2 fuel pots above can see the gas volume adjusting screws-there ends.

Randy