87 300e cranks but won't start-did I mess it up? - PeachParts Mercedes-Benz Forum

richard28 · #1 06-29-2004, 10:34 AM

I just swapped the ecu so I could set lambda. With koeo I still get a 90% fault code, but with the car running I now get a fluctuating duty cycle around 22%; before the swap I got the same fixed fault code. Regardless of how far or in which direction I turned the screw I couldn't get this reading to change much. Now, after all this trying, the car cranks but will not start. I got it to run once by light pushing down on the air flow plate with my finger, but when the car was shut down it wouldn't start again. Did I mess up, or is this just coincidence? BTW, OVP, ignition coil & fuel pump relay have been swapped & seem ok, & the O2 sensor is new. Also, the neutral safety switch was replaced by an indie about one year ago when the car wouldn't start in P or N, and I just tried it in N & it doesn't even crank in N (maybe it never did). Could the NSS be involved? I am planning on checking it this weekend based on posts & the Haynes manual I just got. Thanks- I need to get this car running so my daughter has something to drive!

autozen · #2 06-29-2004, 10:43 AM

I don't have my DTC book here at the moment, but usually you do KOEO to get one of two codes which tells you whether the car is Federal or Calif. Then start the car and check for a sweep. If you get a sweep, lambda is working ans can be adjusted. If you get a steady percentage reading, you need to look that # up in the DTC book. It sounds like you have adjusted the car way out of limits. That screw should never be turned past one turn.

Peter

ctaylor738 · #3 06-29-2004, 02:20 PM

You should get 70 koeo US, 85 if California. If it's really 90, then the CU is confused. What did you get after a cold start before you go into closed loop?

A fluctuating 22% sounds like the brain is working but thinks the mix is rich.

I agree with Peter - you need to retrace your steps and get the mix back to where the car will run.

autozen · #4 06-29-2004, 06:05 PM

Chuck,

I've found these meters to be off by 5%.

Richard,

Is your car a Calif. car? If the car hasn't been in a front ender, there should be a sticker on the radiator support that says " this car meets specs of -------"

Peter

richard28 · #5 06-30-2004, 11:15 AM

Last nite, after much counterclockewise screwing, I got the car to start reliably. I noticed something I thought very interesting. I increased the engine revs by moving the throttle linkage, and when I first touched the metal the duty cycle reading immediately jumped up to 64% and fluctuated around there. It struck me that this was like touching a radio antenna and getting better reception, ie, a bad ground condition might exist and be my problem. Where/what should I check?
BTW, this is not a CA car.

autozen · #6 06-30-2004, 05:30 PM

Got a chance to look at my DTC manual and they didn't start the 70% 85% check until 88. I never thought of it before, but the test is stupid. Why bother checking at the round plug when you can just look at the 16 pin connector. If it has a light that blinks, it is a Calif. car. No blinking light it is federal. Don't worry about what you read KOEO on that car. It means nothing. All you need to do is bring the car to full operating temp which means the oil has to be hot and not just the temp gauge. Check pin 3 for a sweep. If it is sweeping, there is no problem, and you can adjust it. If the needle stays steady, you need to look the % reading up in the code book. What do you read under these conditions?

Peter

richard28 · #7 07-01-2004, 02:21 PM

Thanks so much for confirming the KOEO reading is irrelevant in the '87 300e. That's really a $$$ load off my mind. I'll do a reading ASAP; I just hope that if it is off that it can be adjusted in my car.

pesuazo · #8 07-01-2004, 09:23 PM

I am reading my MB DTC as I type this:
W124
"Up to 03/86 (production date 643) no fault recognition integrated in KE control unit (N3)." Page 14 of Testing Electrical Components of the KE injection system.

Furthermore:
"Since 04/86 faulty input signals have been recognized by the KE control unit (N3) and passed on to the lambda test output. Fault recognition is performed with a lambda control tester (012) at the diagnostic socket (X11)." Page 15 of the document above.

"Recognition of control units:
70% with fault recognition
100% without fault recognition"

No mention of when the 85% for California started though.

richard28 · #9 07-19-2004, 02:03 PM

Here's the next chapter in this frustrating story. At operating temp, with red in pin 3 & black grrounded via the strut metal (I got a fixed 90% reading when the black was in pin 1) , the duty cycle fluctuates around 22 %, and when I revved the engine via the linkage it was around 56-64%. At idle, turning the adjustment screw did nothing. I was reading the Haynes manual & wondered whether the microswitch/accelerator cable connection might need to be adjusted. Also, this car used to be pretty quick, & now I have minimal pep & its very hard to get over 40mph. Any thoughts guys?

pesuazo · #10 07-19-2004, 08:04 PM

It sounds like my intermittent bog down on acceleration problem.
I am still searching for the cause. I have posted a couple of times, but no response. The bog down is accompanied by a fixed duty cycle of 93% (which by the way, is not in the manual). The closest is 95% (deceleration shut off switch).
I am pretty sure it is an electrical problem (in my case).
Yours sound awfully familiar to mine.

simmo300e · #11 07-19-2004, 11:05 PM

Have been doing much the same with my 87 300e recently and would like to add my 2c

First off, my car wouldn't restart after the engine bogged down during adjustment. I thought it might be too rich still, based on the X11 reading of 2.9v (78%) but after research in this forum discovered the mixture was probably too lean, no gas to ignite. Went back outside, richened up the setting and was able to start the engine and continue.

I had the same problem of adjusting the mixture trying to get some response at the X11 terminal and had much the same readings - 70% at KOEO and 77/78% at idle which I try as I might I couldn't change through adjustment.

Steve B kindly responded to my request for help last week and pointed out that there was not much use trying to adjust for lambda when there was no lambda sensor fitted. Doh! Don't know if that applies to your US model cars though but take a look.

http://www.peachparts.com/shopforum/showthread.php?threadid=99320

Perhaps you might also be interested in my fuel pump relay adventures.

http://www.peachparts.com/shopforum/showthread.php?threadid=98631

Have now been reliably informed (by my local dealership) that it is OK to use a relay for the automatic model (marked with kickd) in a manual, but not the other way round. In manual models, the 10th pin (87h, I believe) has no corresponding contact in the socket.

And for the kicker, I've hopefully traced my intermittent idle and hesitation problem to bad electrical connections at the ICV and now the EHA valve. Replaced the connectors and so far its running fine.

Hope this helps. Good luck