I recently did an emotional thing and bought a 1993 300sd. I love the car and knew that I would have to do some work on it. Has 142k miles on it. It also has alot of gadgets on it. Smoothest car I ever driven at 100 miles hour. Anyway to get to the problem. Sometimes turning ignition switch and car starts up and sometimes nothing happens. Very random. Thought it was the starter and had my wife hold start switch on and I hit starter with hammer and engine started right up. Therefore thought it was bad brushes etc. I replaced starter and eveything was ok for a few days and same problem occurred. I had my remote starter with me and jumped solenoid to starter and cranked right up. I don't what problem is- suspect the following. Ignition switch has bad contacts on it or start relay is bad or connection somewhere is failing intermittenly. I don't think its the lockout on the transmission as moving shift lever to neutral had no effect. I guess when it fails again I will try to do some continuity tests. Also I don't have a good schemetic and have been told that the infrared alarm has a relay that is not shown in start circuit which may be causing the problem. Maybe the relay K38 is the culprit. Any help with this would be appreciated.
At least I have elminated starter as problem. I have owned diesels for years and currently have 300sdl 126.
Just sold my 1983 300d turbo. I enjoy working on these cars- but this current problem is frustrating and embarassing.
Jacked up car- removed ground cable from transmission to chassis and cleaned ends with sandpaper and replaced. Hope this helps. Also cleaned battery ground cable and reattached. Now I am testing the car. Will drive and see what happens. Battery is in the trunk on this car.
Have emergency remote starter in trunk to jump starter wire and solenoid. That is if I cannot start with ignition switch. This problem has been going on for 3 weeks now.
Drove car all day and so far - no starting problems- you may have provided the correct fix- wonderful so far.
My local German mechanic - was talking about bad harness to transmission or start relay from alarm system- cannot find any start relay from alarm in the schemetic I got from ALLDATA. I will try to get good factory schemetic.
He never mentioned bad ground(not enough money in that)
He tried to charge me $550 for new engine wiring harness (without installation) which I purchased for less then $300 and told him I would supply to him all he wanted for $300.00 a piece. I installed it in 1 hour- 15 minutes was putting tie wraps on new harness. The other harness was falling apart - biodegradable-(Mercedes screwed up on that big- no wonder people buy more Toyotas) The old harness was working but all the bare wires ment it was only a matter of time before it failed. I do most on my own work as it is hard- maybe impossible to find an honest mechanic. PS I am in Miami. If I had a lift I would do all the work. I only have 1 1/2 foot clearance when I jack car up on my jack stands- maybe less. I like working on these cars.[:)]
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