Help with FD rebuild

[turbochaz]

Hello all. I guess first let me introduce myself. My name is Charlie and although I'm new to this forum, I've been a BMW junkie my entire life. (which is a lot of years now). Anyway, I recently embarked on an 82 e21 resto project and have hit a stumbling block. I set out to rebuild the fuel distributor and paying close attention to Josh C's and the company that I bought the rebuild kit from, I completed the rebuild. After installing it, I decided to go straight into an injector balance test before seeing the car ran first (thankfully). What I found after jumping the fuel pump relay, was that with the air flow meter at rest, injectors 2 & 3 spray what looks like a WOT quantity of fuel. Injectors 1 & 4 spray nothing until I lift the air flow meter. Small at first and the gradually increasing. So I'm assuming that 1 & 4 are working correctly and 2 & 3 for some reason aren't getting metered and just spraying full quantity. My first thought was that I have what Josh refers to as the "perch height adjustment screws" incorrectly adjusted. So I checked my measurement on #2 and although it appeared right on, I screwed it in a half turn. No change. I'm now at a loss for what could be wrong. Does anyone have any idea what I could have done wrong with this rebuild. I'm really not looking forward to pulling the unit apart again. It took me months to get the parts to do the rebuild and I'm hoping there is something else I can check first.
Thanks,
Charlie

PS. For those that are going to say, just carb it, while that is not out of the realm of possibility, I would really like to get it running as well as possible in stock form before I go down the mod road.

[turbochaz]

BTW. Here is what I started with.
PXL_20210321_175143851.jpg

[amarino]

Move injectors around and see if the issue follows the injectors or the FD?

[turbochaz]

Thanks for the tip, but I guess I should have mentioned that this was a running car prior to pulling the FD out. It idled smoothly but was a bit down on power. My goal with the rebuild was just to bring a nearly 40 year old part back to top performance and not necessarily to correct any existing issue.

[320iAman]

Read thru FAQ's---- E21 Fuel Distributor Rebuild ,,See Volume Test * in the posts to get fuel ports matched to factory specifications by adjusting the needle valves, fuel jets,,ect--Volume-Air Box link has pictures and discussion on exactly how to do this.

Randy

[turbochaz]

Thanks Randy. So you are saying that a needle valve out of adjustment can cause an injector to spray even when the airflow meeter is at rest?

[OLD MAN]

Thanks Randy. So you are saying that a needle valve out of adjustment can cause an injector to spray even when the airflow meeter is at rest?

CIS = "Constant" flow, these things are always spraying fuel, what the FD does is change the amount of flow to the injector.

So CIS sprays fuel even when the intake valves are closed. So bad injector can end up acting/spraying like a squirt gun instead of a mister, which is a big problem. Replacing injectors on 40 or so year old cars should be done at some point no mater what the mileage is.

[turbochaz]

Yes, I understand the fundamental concepts of CIS. My issue is, that with the AFM at rest, and the fuel pump jumpered, two injectors are spraying and two aren't. Is this an adjustment issue or mechanical issue? In other words, did I screw something up when I put it together?

[OLD MAN]

Sorry was still editing when you were typing. The issue is mechanical. All the injectors should be flowing the same, this is why Randy said move the injectors around.

Sorry it some times take me awhile to understand what is going on.

You can also pull on the spring plunger in the end of the not flowing injector to see if it changes the no flow issue.

[320iAman]

Thanks Randy. So you are saying that a needle valve out of adjustment can cause an injector to spray even when the airflow meter is at rest?

If the needle valve(s) is(are) too far in , yes. The valve too far in presses the flexible plate downward in essence and this allows fuel to go to the injectors out of sync with the others. Back the the valves off till they are not spraying in fuel and adjust each to 11.74 mm.

Set the needle valves initially all 4 of them at 11.74mm( close is good enough as there will be further adjustment when doing the volume test-if needed) in from the top of the FD-using a micrometer to the inside bottom of the needle valves--then adjust to factory specifications by the volume testing in Faq's in E21 FD rebuild. This is a spare one I rebuilt with 80 mm air disk up from stock 60mm and its volume adjusted as to factory specifications on the car. I'm running the same Fuel Distributor mentioned in FAQ's now for years--no problems.

The only problem I see here that can arise is if the flex plate is bent too much and backing off the fuel screws does not allow the flex plate to come back into original position--in that case a new plate would be required or bend the plate flat and true.

DSCI0619.JPGDSCI0620.JPGDSCI0622.JPG

Randy

[turbochaz]

Thanks Randy. This is exactly what I was looking for. I backed the screws for 2 & 3 out quite a bit just to be sure and they still spray. Then after doing some looking around on my bench, I noticed I missed installing the little red ring that goes on the metering body. I guess, I'm pulling this thing apart again whether I want to or not.

[turbochaz]

Pulled the FD apart this weekend and cleaned everything really well, and set the depth of each of the needle valves to 11.74mm and put it back together. Now 3 injectors work correctly and only 1 sprays with the afm at rest. The only thing I can think of is somehow one of the o-rings is pinching or binding on the metering assembly as it's going in. I guess I get to try one more time. Practice makes perfect!

[320iAman]

I use a o-ring lubricant on the o-rings to keep them in place and for an easier press/slide fit.


Randy

[turbochaz]

Thanks Randy. I did use a silicone spray, maybe something with a little more body would work better. Makes me wonder though, if the o-rings aren't sized correctly. I bought this kit - https://www.ebay.com/itm/0438100075-...kAAOSwx0hdD4HC

[320iAman]

I use the kit that's in FAQ's and reuse the flex plate.
From FAQ'S

O-Ring Store-order

cs mm x id mm

Qty 2-V3.00x018; 3mm x 18 mm V75 Viton O-ring- inside bottom of Bottom half of Fuel Distributor(Qty1)
Qty 8-V2.00x007.5;2mm x 7.5 mm V75 Viton O-ring-Fuel Metering Barrel Fuel Slits(Qty4)
Qty 4-V2.00x015.5; 2mm x 15.5 mm V75 Viton O-ring-Fuel Metering Barrel(Qty2)
Qty 12-V1.80x002; 1.8mm x 2mm V75 Viton O-ring-Fuel Volume Screws(Qty4)

Good for 2 rebuilds of Bosch Fuel Distributor 0438100075, I have plenty of Pressure Regulator o-rings V75 Viton. Thirteen (13) o-rings for complete rebuild of FD 0438100075. O-rings seal the fuel flow so that the fuel goes to where it was designed to go.

For the pressure regulator:
new style piston -AS568A size # 008
Warm up regulator seal- 2mm CS - 7 ID x 11 OD

O-ring Lube--Grease sticks better than Spray.

s-l1600.jpg

Randy

[turbochaz]

Great advice on the grease Randy. I took it apart (again) cleaned and reassembled, this time using silicone grease. What a difference. It went right back together very easily and viola, all injectors work correctly. Curious note though, when trying to start it, it would start and die only. I know there was mention about readjusting the CO after this repair so I started adjusting in at first. Using a long 3mm allen, I had to turn it about 3 1/2 turns clockwise before the engine would even run. Then about an additional 1 1/2 turns to get it to idle smoothly. It runs great now, definitely better than it ever has under my ownership. So just curious Randy, have you experienced this before?

[320iAman]

Glad you got it sorted out and its running now. From what your saying it was set very lean,, My experience was the other side of the equation, my FD rebuild was set too rich and as I turned A/F adjustment screw counter clockwise the idle started to increase I kept going until I hit the point when the idle started to go down--too lean then went clockwise to increase the idle and then set the A/F adjustment electrically thru the O2 sensor. I ran it at ~ +.8V--this is for more power, since then I backed it down and fluctuates between + .3 -.4 to + .7 V..

The CO % for these cars is .2 to 1.2%, mostly 1% CO is what most shops will set them at with an infrared sniffer that measures CO%--the twin ports with screws in them right after the exhaust manifold is where CO% is measured and adjusted by the A/F screw while watching the LED reading showing CO%.

Randy