Good idle, but any throttle will stall it.

[Raboyto2]

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.

[Raboyto2]

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?

[Frank Reiner]

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).

[Raboyto2]

Originally Posted by Frank Reiner

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.

[Frank Reiner]

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).

[Raboyto2]

Originally Posted by Frank Reiner

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.

[MBeige]

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.

[Frank Reiner]

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.

[Raboyto2]

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?

[Frank Reiner]

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.

[Raboyto2]

Originally Posted by Frank Reiner

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.

[PanzerSD]

This sounds very similar to a problem I had in my SEL. The Wire going to the safety shut off switch on my air meter housing had some damaged insulation and whenever my throttle linkage would begin to move, it would ground out and shut my fuel off....my 2c

[Raboyto2]

Originally Posted by PanzerSD

This sounds very similar to a problem I had in my SEL. The Wire going to the safety shut off switch on my air meter housing had some damaged insulation and whenever my throttle linkage would begin to move, it would ground out and shut my fuel off....my 2c

Safety shut off? As far as I can see, i only have wires going to the air flow potentiometer which would be on the other side of the linkages. Ill have to take a peek again.




Finally had a chance to take a look at the fuel flow.

I connected a tube from the exit of the fuel pressure regulator and ran it into a bottle. Jumped the fuel pump relay.



Frank you said 140-150cc per 60 seconds, which doesnt sound right. Im thinking you ment 1400-1500cc per 60 seconds? Either way, I actually did what the fellow did in this video:

M103 fuel pump test - YouTube

Ran the pump for 40 seconds and measured the amount of fuel. In the video he refers to his factory service manual which states "1 liter in 40 seconds".

In 40 seconds I had 1.3 - 1.4 liters. (40/60seconds --> would give me 2.02 liters in 1 minute, which would be 2020cc).



Im assuming my m103 passed the fuel flow test with flying colors.

Safe to say that the EHA is defective and replace it?

[MBeige]

What's the compression in the cylinders?

A misfire can also be attributed to uneven compression. I would pull the plugs and check compression on the cylinders before moving forward.

[Raboyto2]

Originally Posted by MBeige

What's the compression in the cylinders?

A misfire can also be attributed to uneven compression. I would pull the plugs and check compression on the cylinders before moving forward.

Low compression (burn valve etc) would cause miss fire would also continue after 1500rpm, but this misfire does not.