To everyone on here that replies to problems people post... Thank You


I have read these forums for the past year or so constantly finding solutions to issues with my sons car. Its amazing all the little tidbits of info on here that collectively amount to a vast sum of knowledge.


I have exhausted my search capabilities and I am stuck on a couple problems, one of which I have found contradictory answers to.


1985 Mercedes 380SE


1. What is the timing to be set at? I have found three answers on these and other forums. 25BTDC, 35BTDC and 0. I have it currently set at 0 and its starts and runs fine (outside of the next issue) No idea how it drives.


2. Background on this issue... My son bought this car from some dude that didnt know what maintenance was and did very sketchy things to make it run and drive. All the throttle linkages were adjusted wildly and the timing was erratic. After a lot of unrelated work (suspension and the like) I got to work on the engine (after many hours of time spent on these forums troubleshooting) and handled most of the issues. I then found the timing chain tensioner did not pump up. Replaced it and cranked over the engine without spark plugs in it and the coil disconnected and it pumped up. I had the fan and shroud already removed and turned the engine over by hand to line up the cam and crank pulley timing marks. Everything was good and I left as it was late. I got back to work on it several days later and put in the plugs, connected the coil and put on fresh valve cover gaskets.


I got in the car to start it and the key was left in the run position from previously working on it and the battery was dead. Charged the battery and tried to start it and found no spark. Came back here for knowledge and replaced the ignition control module. Car started and promptly died. Over and over. Came back here Replaced the fuel pump relay. Car starts and runs for a random amount of time between 5 secs and 15 secs.


I can jumper either 7 to 8 and the starts and stays running or 7 to 9 and the cars starts and stays running (with the fuel pump relay removed) but the cars idles at a high RPM. After it warms up the idle remains high. The tach does not work, but i checked the tach signal at the test port and its there and varies with the rpms of the motor.


While running I can pull the OVP and the idle goes up a little but it continues running. Reinstall the OVP and the idle drops down a little. I have replaced the OVP with the known good spare with the same results. I have replaced the FPR with the known good spares (2 of them) with the same results.


So here I am, kinda stuck. Any and all help is appreciated. Let me know if theres any more information that you need.


Thank you

the ovp supplies power to the idle control unit, abs and other ecus. it will never cause a car to not run when removed.

replacing the cpr will do nothing if you don't know why to replce it. you need to pressure test the system with the correct gauge set and check cold, warm and rest pressures. the fact the car is the same with other cprs means it may NOT be a control pressure problem you have to test to find out.

high idle could be vacuum leaks. smoke the intake and find out.

you don't mention the mileage nor where the cam marks were in relation to the crank tdc. just good doesn't relate well online because we can't see under your hood, the light here sucks.

here's a link to the manual-

https://www.tonk.ca/Index/116.3index.html

good luck, chuck.

Thank you for the reply

I removed and replaced the OVP relay to test that is was working and having an effect on the system ie to the idle control unit

The fuel pump relay was replaced because troubleshooting showed it had failed

Its has 279000 miles on it

When the cam marks were lined up the crank mark was at TDC as well

Some more info. The car idled at around 650-700 prior to leaving the key on for several days. We have smoked the engine bay and solved several vacuum line issues.

Thank you

1) A tach signal (TD) at the test port is a good sign; the ignition amplifier (TSZ 8) is supplying a signal.
2) Check on socket #10 of the fuel pump relay (FPR) for the same TD signal. The TD signal goes, in sequence, from the TSZ to the idle speed control unit (ICU), to the FPR.
3) Since there is neither idle speed control, nor latching of the FPR, both of which depend on the TD signal, look for a fault in the wiring between the TSZ and/or test socket, and the ICU. The wiring will usually be green w/yellow tracer. There may be a junction block on the left fender well.

I get roughly 3.5v at pin 10 to the FPR.

The Idle Speed Adjuster Solenoid does not appear to be getting a signal. I pulled the two prong connector off of it and applied neg to one post and 12v pos to the other and the idle immediately dropped to what sounded like the correct range. I checked the plug with a volt meter and neither one showed any voltage.

The ICU is the black box on the firewall next to the ABS box?

Some thing s have changed and I dont know why.

I get 1.8v at the diagnostic port 1 (tach) and at pin 10 for the fuel pump relay now instead of 3.5 that I was getting.

The Idle speed solenoid is now sorta working. Its getting voltages nad is adjusting the idle speed but its a little erratic. Getting between 3.5 and 4.5 and its very jumpy.

I ohm'd out a bunch of wiring along the tach circuit and it appears to be intact.

I still cannot figure out why the fuel pump relay is not latching in and why its random on how long the car starts and runs with it in. The car will start and almost instantly quit sometimes and other times it will run for 10 or 15 seconds before the relay drops out.

1) If you can, post a picture of the TSZ that you have.
2) It is good that the TD circuit appears to be intact. The varying voltage in that circuit suggests that either the output of the TSZ is failing, OR there is one or more points of high resistance (loose or corroded connections) in the TD wiring, starting at the plug on the TSZ.

The TSZ is the ignition control module, correct?

https://www.ebay.com/itm/306252681369?fits=Model%3A190E%7CMake%3AMercedes-Benz&_skw=IGNITION%20MODULE%20FOR%20MERCEDES%20190E%201984%201985%201986%20PNS%200227100023%200227100042&itmmeta=01JYW7ATDA0GBZ65W0C3S6FMWH&itmprp=enc%3AAQAKAAABMFkggFvd1GGDu0w3yXCmi1cgxyhDLGrw%2BMAyTxuxVhIQp1fMSWUBogcwaRD27vXUUl73h4wALPegN R4QBYwxB7VuFmprqeezJew71C2HL16QS7e2PcVHNePApMYSQe%2FRxTQALLW0FlmYHNhM9uPMVV9NaMPcqI2gYEOBsFQ62j6Y%2B osA5YxYk%2BpXD2CidN%2BatPgPOCEwgzEuzucRzotnGSwyAavn6CwmLm2z4dQ0k51RniQN8bYKJqdKrwqwhuI0A%2F51cz4Sx0J 4RcH91whqtYiLxFseyP8k3mJ6N9eAKBuIwfyecLohHBHlqpbl6Qs03z5WVTa2Ri5fa6yGGpRYJZPoWcLv3g6TDdOGrkDjU2w5eJM IMP%2Fv3VWxUfIaSIyvZjSbSyxiF6XYDQcyme5klA4%3D%7Ctkp%3ABk9SR-amq4f3ZQ

It looks like the one the above link points to. I bought it after the original one failed which looked like the following link and is bolted to the front of the drivers sie fender next to the coil.

https://www.ebay.com/itm/235645882281?chn=ps&google_free_listing_action=view_item

You have gone down the familiar TSZ road!
The replacement unit which you bought, unbranded, has unfortunately been less than satisfactory. Was there any problem with the fit of the plugs? In many cases the pins and the trigger lead socket are so badly made that they will not connect dependably, or the trigger plug cannot be inserted into the socket.
The brands that are known to be good are Huco, Siemens, Transpo and the Bosch OEM version.
That TSZ was also used by many BMW models; a Pick-n-Pull yard may be a good source.

I replaced the TSZ with an OEM from a wrecking yard on the east coast. Took awhile to get here, but it was the only one that had a return policy if it was a bad unit. Plugged it in and the car runs like a top now

Thank you so much for the help, both the advice and the link to the manual.

A new problem cropped up after driving it for a bit. The idle kept climbing as we drove it until it was around 2k RPM. You could use the brakes to slow down and the like but you had to use them to keep from booking along. Is there a way to adjust that manually? I hear you are not supposed to but I am concerned that the PO may have made changes to get it to run instead of actually fixing things. (they made alot of changes to linkages and the like)

did you use the link i posted?

I did, thank you

if you did, then you should be able to find the problem. good luck.

If that 2K is the in-gear idle it is probably outside the range of the idle controller. Does it run that fast or faster in Park/Neutral?
Try disconnecting the link from the cruise control actuator bellcrank that goes down to the throttle. That will remove the effect of any mis-adjusted linkages.

I went out to chk on it and started it up. It idled at 2200 or so with a great sucking sound under the hood. Opened the hood and the tube on the passenger side at the front that connects to the air filter housing was disconnected from the air filter housing. I put my thumb over the end and it had powerful suction. The suction quit and came back quickly then quit. The idle wobbled a bit and I reconnected it. The idle wobbled a bit lower, I then goosed the throttle lightly and the idle came down to normal (650ish) and stayed there. Test drive tomorrow after some reading on that