1986 260e. It is a grey import from Germany. M103


The last few days I've been noticing a little hesitation and a misfire. This morning it started getting a lot worse to the point where I was stuck at a light for 5-10 seconds hesitating, then it would clear up and go just fine. It got to the point where it would completely stall. It would restart and go for another minute then die again.

Currently it will start and idle just fine. The second I put any pressure on the throttle it will start missing (almost like running on 3 cylinders) then completely stall. No amount of throttle will keep it running.

What iv done so far : pulled the plugs; they are perfect. Noticed the wires were on their last legs so I replaced those, cap and rotor (Bosch for all three), but it has made no impact.

I can hear the fuel pump turning on when I turn the key , and it turns off like usual (when pressure is reached). Temperature does not seem to make a difference. It does the same thing hot or cold.

It's currently still in the parking lot where I left it.

Any suggestions?

I was thinking possibly crank position sensor. Anyway of testing this? But would it idle if it was gone?

(I will post a video when I get home later tonight)

Thanks in advance.

The video i was suppose to post:

http://www.youtube.com/watch?v=vMy85VRe7IU

So, the next day I had the vehicle towed home. I didnt have much time to work on it until recently.

I noticed there was a strong fuel smell when ever it stalled so to me it sounded like it was flooding out. I removed the fuel injectors and dipped them in Redline fuel injector cleaner for a while and put them back in. To my suprize the vehicle ran great for about 10 minutes and then went to crap again. I thought maybe the injectors were sticking so i replaced them and their rubber holders. No affect.

So, so far replaced (because they are maintenance items
-spark plugs
-distributor cap
-distributor rotor
-spark plug wires
-injectors

(o2 sensor and fuel filter were replaced a year ago)


So now I actually started testing individual parts:

- Over voltage protection relay (OVP) seems to be working properly, fuse is good, opened it up and did not find any corrosion or cracked boards or solder points.

-Fuel pump is coming on, coming up to pressure and turning off until I crank the engine. (So I assume this eliminates the fuel pump relay?)

-Fuel pressure seems good. I only have 1 fuel pressure gauge so cant taking a differential reading, but the lower chamber seemed to be a few PSI lower at idle.

-Fuel filter (fuel screen) at fuel distributor is clear.

-Air/fuel mixture duty cycle is at around 50 and does go up and down properly (o2 sensor is working)

- Idle air control valve (IACV) is getting a signal, current is within spec, resistance is correct on it, it does function if I apply 12v to it.

-Cold start valve (CSV) does open and has a nice spray if I apply 12v, but I do not see a signal going to it to open when then engine is stone cold.

-Fuel accumulator is working as the air metering flap has resistance after sitting for a few hours, also if I crack one of the fittings fuel squirts out. (fuel distributor stays pressurized)

-Fuel pressure regulator (on front of fuel distributor) seems to be working? Diaphram doesnt seem to be torn as there is no fuel coming out if the vent tube.

-Electronic hydraulic actuator (EHA) isnt leaking fuel, and has the proper resistance (19.5ohm if remember correctly), and from the information I can find online, has the correct current fluctuations but im not 100% sure on this. (Should be around 0mA fluctuating up and down ?)

-Air flow potentiometer I did not test yet other than it shows full open when doing the air/fuel mixture test.

-Coolant temp sensor (for ECU) tested and showed proper resistance.

-Crank Position sensor I tested and showed proper resistance. (just incase)

-I did find a crack in the hose going from the engine to the idle air control valve (where the cold start valve sits), and replaced it.

-I made sure every electrical connector to all the sensors and actuators were corrosion free.

-Non of the pins at the ECU look damaged, bent, or corroded.

So now during all this testing it was running and idling fine, still had its hesitation like before. It was maybe a little harder to start then usual quite a bit of cranking (probably because of that cold start valve not getting a signal?) The last thing I did was replace the hose to the IACV, took off the EHA (to have a look at it), and cleaned out the fuel screen and now it wont start, at all. It cranks and cranks and cranks. (Im getting frustrated) So I cracked the fuel lines a the injectors, and cranked. There is no fuel pressure at the injectors now. Hooked up the gauge to the distributor and I have pressure from the pump there, but its not being distributed to the injectors. So what does that mean?

A through examination sequence indeed!
Have you tried starting with the EHA unplugged? That condition leaves the acctuator plate in the neutral position, i.e., neither enrichening nor leaning the mixture. There is a possibility that the system controller is sending a full lean (coasting shutoff) signal to the EHA. To build fuel pressure remove the Fuel Pump Relay (FPR) and bridge sockets 7&8 (the FPR contains a timer which shuts off the pump if the engine is not running).

I did. I unplugged the EHA while it was running and watched the duty cycle, it started to drop slowly : 50, 40, 30, then stopped at around 20. I dont remember if thats lean or rich. (this was when it was running)

At the momment i cant get it to start at all, EHA plugged in or unplugged.

It seems fair at this point to ask if you have confirmed that spark is present at the plugs? Remove a convenient spark plug, stick it back into its wire, and lay it on a grounded surface where you can see the gap. Is spark visible when cranking? If yes, confirm rotor phasing/timing. If no, begin the hunt with a continuity check of the flywheel trigger and its lead up to the ignition controller (EZL).

If you can confirm proper ignition function, repeat your check of fuel flow at the injectors (lines cracked), while pushing down on the airflow sensor plate (manually moving the fuel plunger).

I checked for nice constant spark back when i was stuck in the parking lot. But havent since. But since im not getting any fuel at all with the lines cracked (and tried with them comletely open not even connected to the injector). Flywheel trigger being the crank position sensor, i already checked its resistance. But that wouldnt block the fuel flow? I can check for spark the next time i have a chance.

I'm with you on your view that the problem is fuel; the ignition suggestion was to eliminate that area.

Does the car have one fuel pump or two? If two, are both running?

The previous suggestion to check for fuel at the injectors (lines cracked) while simultaneously moving the fuel dist. plunger, was to ensure that fuel was moving through the metering slits and upper chambers. You might also try cracking the fuel lines at the FD. While all these checks are being done it is necessary (obvious!) to have the pump(s) running and if possible have a gauge connected to the upper fitting of the FD (system pressure). Bridging the pump power at the relay socket ensures that the pump runs while doing checks.

The car has one fuel pump.

I have not tried moving the plunger while cranking with the fuel lines cracked.

I should probably read up on how the fuel distributor works a little better. I know it has a diaphragm, and the EHA regulates the pressure between the top and bottom. Do all the injectors just spray fuel continuously?

I did connect the gauge at the top of the fuel distributor and monitored pressure. It jumps up (75psi if i remember correctly?) as soon as I turn the key to on, then I hear the pump turn off and the pressure drops to around 20-25psi until i crank it (which then turns the pump back on to 75ish again.)

These figures are not exact as i was trying to monitor this tiny gauge from a distance haha. I like the idea of bridging the pins to force it to come on, then im not running in and out of the car. I have a little free time tomorrow, ill see what i can find.

Im assuming im doing something similar to this



M103 WOT flow test - YouTube



In one of his other videos he states to jump pins 15 and 87. Was there a change up here?

I wasnt aware this is how it worked

Bosch K-Jetronic (CIS) explained - YouTube


So , its 100% mechanical for what is stopping fuel from reaching the injectors if the fuel pump is running. I must of messed something with my air flow meter. Ill inspect tomorrow.


Question : The IACV is connected to two hoses. One hose goes back to the "air chamber" where the fuel metering valve is located. The other hose (the one i replaced) runs to the cold start valve. Where does this hole run to? Does it feed all the cylinders?

Had the same issue with my '89 190E 2.6 (same engine basically), but had a concurrent low compression problem also. A head job did the trick for compression and passing smog (along side a new catalytic converter), but it kept misfiring and stalling at times even after this job was done.

Turned out to be a loose 8mm nut on the ignition coil. Remove the cap and check for sparking in the dark.

You're coming up to speed on the basics; good!

Re: Bridging the pump relay. There are two sets of numbers involved; one set is for the socket (7&8), the other for the relay itself (either 15&87, or 30&87). When you remove the relay you will see that the pins are numbered (30,87,31,15, etc.); the socket is also numbered (1 thru 12). Since you will be inserting a jumper wire into the socket, the socket numbers are given, rather than the relay pin #s.

Yes, fuel flow is continuous, hence "CIS" (Continuous Injection System).

There are (in your case) six sets of upper chamber, lower chamber, and diaphragm; one set for each injector nozzle.

The IACV is a throttle plate bypass; measured air from under the air meter sensor plate is directed to the intake manifold/inlet ports to control idle speed independently of throttle position. Cold start fuel is injected at the point the bypassed air enters the manifold. Yes, the bypassed air serves all cylinders.

Thanks Frank.


I jumped the fuel pump relay. Opened all the injector lines (completely) and pushed down on the air flow flap. I did not get any flow to the injectors.

Although it shouldn't matter, I tried with the ignition on/off , and with the EHA valve plugged in and not. Made no difference.

I checked the pressures as well.

Top chamber : 82-83 psi
Bottom chamber : 80 psi.

I made a video of this.

M103 Fuel Flow - YouTube

I'm suppose to have a 4psi difference correct? Could this be why I'm not getting fuel out the lines? The last thing I had off before it would not restart is the EHA. Is it possible I damaged it and it is allowing the pressure difference to be to small? I made sure to be gentle with it.

Is it possible something inside the fuel distributor Is damaged? I'm assuming a torn diaphragm would only affect the port where it is torn.

Edit: I see now that the pressure difference is suppose to be 0.4-0.5 bar. (5.8-7.25psi) Which is quite a bit more an I'm showing. Should I try giving the EHA a 1/4 turn clock wise?

Check fuel flow at the lower chamber fitting; remove the line, connect a piece of hose that you can direct into a container. Flow should be approx. 140-150 cc per minute. There is a restrictor in the lower chamber outflow circuit; if that restrictor is clogged the flow will be low, the lower chamber pressures will be too high (as you observed), and injector flow will be cut off.

You ask about turning the EHA; I am not familiar with any adjustment provisions in or on the EHA.

Im heading out of town tomorrow morning. Hopefully I find a little time before then. To access this restrictor, im assuming I would need to disassemble the fuel distributor? I do remember the fuel pressure being in the low 70's (psi) about a week ago before this hole no start thing started.

With all respect, caution on any thoughts of disassembling the FD; there are service facilities that are successful in rebuilding them, and they are available on an exchange basis. The FD is, however, not considered to be field serviceable other than replacing the EHA, and the inlet screen.

What you can do is to remove the FD from the engine, remove the EHA, and squirt carb cleaner back through the lower chamber outlet fitting. This process may or may not clear the orfice. This cleaning process would, of course, follow a flow check that was too low.

If, however, the lower chamber flow check is normal, your attention should then be turned to the EHA, as it is a component which you have, ah, investigated.