'80 300se start,stall,start,stall,start,stall - PeachParts Mercedes-Benz Forum

bolomiester · #1 06-04-2009, 04:42 PM

This is an '89 300se and I've been chasing this problem since I bought the car in March. It always takes at least 2 tries to start it, sometimes 10 times or more. It starts, revs up then the rpms drop to zero and it stalls. When it finally does keep running it will sput and sputter for a few seconds before settling down to a normal idle.

There have been occasions when even 10 or more tries was not enough. On those, it will start if I hold the throttle open a bit. But if I take my foot off it will stall. Even if I hold the throttle open for several minutes before releasing it. The only way I keep it running then is to ease the rpms down to where I can shift into drive and drive it for a few minutes. Eventually it runs fine, but if have to stop within those few minutes it stalls. It seems to need that sput/sputter bahavior before it will run right.

It is much worst on a hot start after it sits for 30 minutes or more.

I replaced:

Distributor cap & rotor
Spark Plug wires
Spark plugs
Fuel pump
Fuel filter
Fuel accumulator
Hoses leading to and from the ICV
All fuses
Air filter

I've tried jumpering the fuel pump to take the fuel pump relay out of the equation but it did not make a difference.

Everything on this car works, and once started it runs and idles very well.

Can anyone give me a clue where to look next. Thanks.

david s poole · #2 06-04-2009, 05:34 PM

check and see if the fuse in the ovp relay is blown.it sounds as though you are starting without the benefit of power to the fuel injection computer or "limp home mode".

mak · #3 06-04-2009, 08:51 PM

suggest pull out the over votage protection relay, clean the pins on it and the fuse on the top side . same for the fuel pump relay . the solder joints in the OVP do open up like it did on mine unit.
Remove and clean the ICV thoroughy , check for operation by momentarily applying 12 V to the pins and kistening for the operational click and monement.
keep us updated
regards
mak
89 300se

Randy · #4 06-05-2009, 09:15 AM

Don't forget the crankshaft position sensor. This one got to me once, and it is cheap/simple to replace, and for an older model, cheap insurance, even if it is not causing the immediate problem.
Hope this helps you, like someone on this forum helped me.

bolomiester · #5 06-05-2009, 03:27 PM

I checked the OVP relay fuse and it was fine. However, I had a spare OVP relay I bought in a box lot of various relays and switches back when I had the 380 SEL. It didn't fit it the older car but it's the exact part number to work on this one. I cleaned the pins and plugged it in. Last night it seemed to do the trick, but today the car's behavior has been pretty simular, though not as severe. I'll see how it does over the next few days.

The idle has always been good, and I did clean the ICV with carb cleaner when I changed its hoses, and that did stop the idle from "hunting" from time to time.

Thanks for the CPS suggestion. I'll try that next.

bolomiester · #6 06-06-2009, 12:19 PM

I went into Fastlane to order a new crank position sensor. I expected to find one part listed, as that's all the repair CD shows, but discovered two parts listed. One says, "located at front crank pulley, W0133-1613779." The other is "at flywheel, W0133-1603956." I thought I could sort it out by checking another parts supllier's website but found the same confusing listing, plus that website also listed a camshaft position sensor, which I can't find on the repair CD. Then I checked another supplier and found only one CPS listed. ?????

Can anyone help me sort this out. Does my car have two crank position sensors and does it have a cam postion sensor as well?

The car is still up to the same behavior after swapping out the OVP, so that pretty well rules it out as the culprit.

Cal Learner · #7 06-07-2009, 09:01 AM

Here's my understanding of the M103 motor of your vintage. There are 2 sensors. The one you want is at the flywheel in back down by the bell housing. The other one up front is, I've been told, for diagnostic rather than operational purposes, by providing the so-called TD signal to the EZL. No cam sensor in '89 (I think). The condition of that flywheel sensor is very easy to confirm with your ohmmeter though, so do that before investing in a new one.

bolomiester · #8 06-07-2009, 10:35 AM

Quote:

Originally Posted by Cal Learner

Here's my understanding of the M103 motor of your vintage. There are 2 sensors. The one you want is at the flywheel in back down by the bell housing. The other one up front is, I've been told, for diagnostic rather than operational purposes, by providing the so-called TD signal to the EZL. No cam sensor in '89 (I think). The condition of that flywheel sensor is very easy to confirm with your ohmmeter though, so do that before investing in a new one.

I see the one in front and it connects to front of the engine. I looked at the CD for info and see this drawing:

Then I found this drawing which shows the "position pickup" located in the back taking its input from the segmenbts on the flywheel:

Finally I see this drawing which is an overall view showing "position pickup" GOING FROM THE "N1/2" connector on the EZL to the back of the engine:

Is it possible that the PO or his mechanic has this hooked up wrong? That is the connection to the EZL that should be going to the crank position sensor on the bell housing is instead connected to the "diagnostic sensor in Front? Would the engine even run if this was the case?

This sure has me scatching my head. I finally found the sensor mounted to the bell housing and I can see the wire that comes from and it is thicker than the one coming from the N1/2 connector on the EZL. It is also a different color, black instead of the gray that is currently connected from the front sensor to the N1/2 connection on the EZL.

BTW, what is the test procedure for the crank position sensor and what should its value be?

Thanks,

Cal Learner · #9 06-07-2009, 02:07 PM

Bingo! Those are the diagrams you want to see. The L5 crank sensor is supposed to be connected to the #2 plug location in the EZL diagram. I don't see how it could be mis-wired and connected to the front sensor, but if you say that's what's happening, that's wrong! That would explain your problem. What is the wire from the L5 (back) sensor connected to?

I don't have the diagnostic test for L5 right in front of me at the moment, but you should find it in the FSM section 15-1250. I think it's something like this: engine cold. Ignition off. Unplug the L5 at the EZL. Multimeter set to Ohms. Positive probe on inside of pin. Negative probe on outer part of pin. Spec is around 700 -1200 Ohms. If no, rplc L5 sensor.

EDIT: Confirmed test proc above, but spec range is actually 680 - 1200 Ohms.

bolomiester · #10 06-08-2009, 11:05 AM

I'm wrong. I made a more careful inspection of where the crank position sensor goes this morning and it goes go to the #2 plug on the EZL. I had to remove a number of wire ties and really dig into the wiring harness before I could see its path acurately. Sorry for the misleading report.

Anyway, I measured the resistance between terminals 7 and 31d and it was 787, as measured on the scale below. I thought I could use the 200 scale but when I did I got no reading. Now I wonder if I had my multimeter set wrong. The second part of the test, terminal 7 to ground did not change the static reading.

So . . . my first question is did I have my multimeter set right. The second is, based on the procedure below, if my meter was set right and I got no reading going from terminal 7 to ground means the crank position sensor is bad, right? I don't see any breaks or damage to the sensor's wire.

I should probably just replace the crank position sensor and hope for the best, but it's so much better to accurately diagnose what's really wrong before throwing parts at the car. I really appreciate the skill and knowledge the forum's members have given me. Otherwise I would have given up on MB ownership long ago. Thanks for all the help.

Cal Learner · #11 06-08-2009, 01:06 PM

Your test result of 787 is OK for the first test, and for the second test to ground, your static reading is infinity, and that's OK too (the spec is >=200K or infinity). I just tested mine and got 872 and infinity. Based on your results, your CPS is not the problem.

bolomiester · #12 06-08-2009, 01:22 PM

Quote:

Originally Posted by Cal Learner

Your test result of 787 is OK for the first test, and for the second test to ground, your static reading is infinity, and that's OK too (the spec is >=200K or infinity). I just tested mine and got 872 and infinity. Based on your results, your CPS is not the problem.

Too bad, I hoped I was closing in on it. When I tested terminal to ground thought I would see a change in the meter's display, I do when I touch the leads together. But the display just stays the way it is on my photo, not a flicker.

The last couple of days I've been just holding the key in the start position longer. It sort of tries to start, but since I have the key held over it just keeps cranking instead of stalling until it finally does the sputter, sputter thing for a few seconds, then idles normal.

I'm back to scatching my head as to where to look next. Thanks for the confirmation, even if it was bad news ;-)

bolomiester · #13 06-15-2009, 08:54 PM

Since my last post I've installed a new ignition coil, and a new crank position sensor, but neither helped. The starting behavoir is the same.

It will fire right up then instantly stall. If I hold the key in the start position it will fire up instantly - stall - crank some more - sort of fire - crank more - finally continues running but spits and sputters for several second before finally settling down to a smooth idle. If I have to crank a long time before it continues running, it will spit and sputter longer, and the idle will be a bit rough until I've driven a few blocks.

At times it acts as though it's going to stall when I'm sitting at a light. The rpms will drop, then speed back up to a normal idle speed. Sometimes I feel like the car has a very slight miss at idle, other times it's smooth. It never misses at driving speed, and pulls very strong and smooth from tip-in all the way to red-line.

Here's what I've done so far:

New Distributor cap & rotor
New Spark Plug wires
New Spark plugs
New Fuel pump
New Fuel filter
New Fuel accumulator
New hoses leading to and from the ICV
All new fuses
New Air filter
New ignition coil
New crank position sensor

None of this has made any difference, and about the only thing, in the ignition, that I haven't replaced is the EZL. Could this be it?

I've also tried jumping the fuel pump relay to force it to run and it made no difference.

I checked the fuse in the OVP relay and it was fine, plus I swapped it with a salvage yard OVP and that made no difference.

One thing I've noticed is that when it starts normally, it cranks longer before any firing. When it does that it doesn't stall but settles down to a smooth idle right away. This only happens when I turn off the key and restart immediately.

Help! I'm running out of money and ideas.

bolomiester · #14 06-16-2009, 10:41 AM

Is it possible that the EHA could be causing this? Do any of our experts have an opinion?

brewtoo · #15 06-16-2009, 10:51 AM

At cold start, the EHA is not functioning yet. A signal from the O2 sensor has to be provided before the electronic adjustments will come on line.

The system is really a mechanical fuel injection system with electronics that fine tune the mixture. If the lambda is properly adjusted, the system will function - even with the EHA disconnected.

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