MichaelBrown

On a 93 2.3 with all of the electronics disconnected (o2, EHA, cold start) except for the airflow potentiometer, what determines how much fuel goes to the injectors when the throttle is increased or decreased? From what I understand, at this point it’s a purely mechanical system, basically limp mode.

i’ve been struggling for weeks to track down a fuel injection problem that I have not been able to resolve and no one else has either. I’m trying to break the system down into the least amount of variables possible and this will help.

insame1

when the plunger goes down to let air in a needle moves up to let fuel into the distributor.

MichaelBrown

Thank you for the information

MichaelBrown

Thank you for the information

dolucasi

I think we covered this in your other post but basically all you need to unplug is the EHA for the electonic part of the system. That is the final actuator electrically.
The rest is all in the fuel pump and FD.

I think DaveKost stressed on measuring the lower chamber fuel pressure as well as system pressure. Usually one needs a Bosch pressure test kit with a valve so you can switch between the two as it is the delta that matters. This delta creates more or less fuel to be injected. Again do not quote me on this but I believe more delta means less fuel, and less delta means more fuel. The FD is built that way.
Hopefully I do not have this backwards.

So in your case it is critical to measure the delta and might shed a light into why you are flooding the engine even with the EHA disconnected.

Perhaps report on that and maybe we can suggest the next step.

- Cheers!

MichaelBrown

Hey there so yes we have done all of this already the fuel pressures appear to be in spec. We swapped out the FD from my parts car thinking the fuel distributor diaphragm may have ruptured but it’s still exhibited the same issues. I thought it highly unlikely the 2 FD’s would have the same issue but we went ahead and rebuilt the FD but are still having the same issue.

even with everything disconnected the car is still flooding so I’ve pretty much come to the conclusion that it has to be related to the throttlebody specifically that valve. I don’t know what else it could be at this point I’ve exhausted all options.

Even with everything disconnected and the car not in the flooded state it starts right up and idles well. However if you give it a little bit of gas, the RPMs rev and when you let up on the accelerator they don’t go back down. Then at times it seems like it has a mind of its own and the RPMs and engine continue to rev until you have to shut the car off. Clearly something is going on even at the most basic level with the amount of fuel being fed to the injectors.

our next plan of attack will be to pull all of the injectors and visibly monitor the fuel to see if we can see anything unusual. Will also be thoroughly looking at the throttlebody.

MichaelBrown

Never mind, my patience has run out with this car I’m sending it to the junkyard it’s not worth hauling it into a shop to have someone else try to figure it out.

it’s got too many miles on it anyway it’s pretty much worthless

dolucasi

Too bad.

Throttle body does not really do anything in the mechanical injection, just opens to let in more air though, which moves the AFM plate to increase the fuel flow.

Had you already tried leaning the mixture through the adjustment screw? Had you tried this already? Maybe someone prior to you messed up the adjustment way too rich incorrectly and could not get it back in range. Is this what you meant by checking the throttle body? The adjustment screw is part of the throttle body.

If not done so, I would adjust it before you get rid of the car. It could be way too "rich" adjusted and swapping the FD would not solve this.

Dave Kost

"Hey there so yes we have done all of this already the fuel pressures appear to be in spec. We swapped out the FD from my parts car thinking the fuel distributor diaphragm may have ruptured but it’s still exhibited the same issues. I thought it highly unlikely the 2 FD’s would have the same issue but we went ahead and rebuilt the FD but are still having the same issue."

Any time you change anything with the Airflow Meter Assembly (AFM), you need to reset the mixture. What I mean, if you change fuel distributors, change potentiometers or change EHA's. or make any major adjustments. By doing this you are setting the position of the plunger in the FD to the position of the metering plate of the AFM. This is your basic setting. BUT, before you do this, the fuel pressures need to be in spec. as well as fuel delivery volume. Small adjustments make a big change in the air fuel ratio.

Who rebuilt the fuel distributor?

MichaelBrown

I took apart the throttlebody off my parts car yesterday so I could visibly see how the thing was put together and I see how it operates now.

yesterday I messed around with the duty cycle again thinking exactly what you just threw out there, that someone may have tampered with the mixture adjustment screw on this one as well.

it was at this point that I lost my patience because the thing is supposed to read 85 indicating that it’s a California car. It was doing that in the past no problem. Now it’s reading 30 when you set the thing in diagnostic mode. This is the deal with this car it’s always something new it’s probably some sort of error code I don’t know at this point.

The oxygen sensor light is back on on the dash even though I just spent $120 replacing the oxygen sensor and I’m very hesitant to spend anymore money buying another one and I know the thing is not gonna run right with some issue with the oxygen sensor.

Even though the duty cycle said 30 when it’s supposed to say 85 I went ahead and got the thing running and it was showing I believe 52 when cold which if I read correctly was in spec Even though it was reading 52 the idle was extremely fast then the car starts surging when it got warm and when the car starts surging the duty cycle meter fluctuates wildly I mean this car so messed up I don’t know that it’s ever going to run again at. It was at that point that I just threw my hands up and I’m just like I’m done with this.

MichaelBrown

I found this man’s thread on a diagnostic and I’m gonna go over it as it as one final last ditch attempt to get this thing to run.

it’s kind of all over the place but I think I can extract enough out of it to check all of the components.

I just have to now figure out why the duty cycle isn’t showing 85 like it normally does before the car is started. It makes me feel that I might not be getting accurate readings.

https://mbworld.org/forums/e-class-w...diagnosis.html

MichaelBrown

If anyone is reading this and having serious trouble like I am I’ve run across this gentleman on YouTube that has broken the system down it has provided the exact information we need in order to get this running. Here are several of the links.

dolucasi

At this point what you need more is Pieter Hedary's tutorial on Jetronic. I would ignore all error codes until you have a working FD and AFM plate assembly aligned to it.
As mentioned before once you unplug the EHA valve you are down to these 2 basic components (and the fuel pump and injectors of course).

The error codes could mislead you if you do not have a working mechanical part of the injection.

The car will struggle a bit without the EHA valve when cold but probably not in your case because your FD/AFM is aligned way too rich to begin with.
I would not even connect the EHA valve until you can get rid of the super high rich condition.

Oh and the check engine light is on because you unplugged the EHA. Ignore it for now.

Dave Kost

>Get the car running in closed loop > 80C
Unplug your o2 sensor
Attach your Multi meter positive lead to green wire of the O2 sensor , negative lead to a ground
Put your meter to DC volts- you now are reading the output of the O2 sensor
Adjust the 3 mm screw on the AFM so the reading on the MM reading is between .1 to .9 volts DC. (lambda is .45 volts DC) the reading will be oscilating
Plug you O2 sensor back in.
Now basic mixture is set so the ECU can command the EHA to reach lambda.

The ECU assumes that the fuel pressures are in spec both system and differential and that there is no unmetered air entering the intake past the throttle body.

190Efan

At this point, you guys might want to contact the MB Classic Center is CA because I think the issue might be tampering with the settings by previous owners to the point that the entire system is now fouled up because of it and could be what's causing all of the problems because various parts of the system are getting bad data because of the incorrect settings and are now trying to compensate for it.. The MB Classic Center can give you the settings that your cars actually left the MB factory with. They're really knowledgeable about our W201s. You can explain the steps you've taken to try to solve these issues and see what additional advise they might have for you. That's what I would do at this point if it was my W201. Just my 2 cents.

MichaelBrown

I’m gonna go out to the shop tomorrow and spend a few hours with the car again using all of this new advice

MichaelBrown

Dave this is interesting. Should I performed this adjustment with the EHA unplugged?

Dave Kost

in your case I don’t think it matters. We are to get the base setting so the ECU can do it’s job.

also, you should have 1-2 mm of free play of the air meter disc before it moves the piston of the fuel distributor with key on engine not running.

Again, who rebuilt your fuel distributor ?

MichaelBrown

We did it at my shop we replaced the diaphragm and the o rings we did not tear the thing apart. There was no difference in behavior between the one that was on there and the one that we replace the diaphragm on. In addition, we replaced the assembly off my parts car which is the same year model and there was no difference.

we definitely have a major over fueling situation because the catalytic converter started glowing bright red once I got it to 80. I’m running it without the EHA plugged in at the moment and I’m letting the car cool down.

I am getting an O2 sensor warning light on the dash even though it’s a new O2 sensor so I’m not sure if that’s unrelated I’m ignoring it for the time being.

i’m going to continue to mess with it for a couple more hours today

MichaelBrown

Unfortunately none of these suggestions seem to have any effect at all. Out of desperation and the fact that I really don’t care at this point anymore, I got the car running without the O2 sensor or the EHA valve hooked up.

the idle was at 2100 RPM so I adjusted the mixture screw down and got the idle much closer to where it supposed to be. I don’t know if the duty cycle works in this mode or not but It was at 52 after I made that adjustment.

when you turn the car off and try to start it, you get right back to this flooded situation and have to pull the fuel pump relay to burn off the fuel to get it to start again.

In one of the videos I posted, the guy said there’s an O-ring at the base of the fuel distributor that could cause fuel issues if it goes bad and I’m just wondering if that might not be at the root of my problem.

Dave Kost

Not only is there an o ring at the base of the fuel distributor, there is also a critical dimension that you set the slotted nut that sets the correct piston height. If you tightened that nut down too much the injector could be seeing pressures that would keep the injectors flowing. I believe the dimension is .6 mm.

Can you smell fuel in the intake when you push down the AFM plate. If the seal is leaking you will smell and also see the fuel.

Dave Kost

To be clear,the o ring I am taking about, is in the inside of the lower half of the FD. It seals the outer barrel to lower half FD. There is also a seal around the nut that the tip of the piston slides thru.

Also, you can pull the injectors and see if they are flowing when you shut down the car. Put them in baby bottles.

MichaelBrown

That O-ring has not been replaced and we did not touch that adjustment as I have to order it. I can smell fuel inside of the afm housing.

I just set the mixture control using the calculation of measuring the top of the plate to the top of the support then adding 1.9 mm to that.

using that calculation the mixture screw was extremely off but now the car will not start at all, even with pulling the fuel pump relay but I actually see that as a positive sign.

MichaelBrown

I could not use the method recommended measuring voltage off the O2 sensor as the catalytic converter is overheating due to over fueling at 80c

MichaelBrown

So after letting it sit for a little bit and using the 1.9 mm calculation and mixture adjustment the car is now trying to start but won’t run