c 280 starting
 

I have a 1994 C280 with approx 110,000 miles on it. Once in awhile is will not start. If you get out and lock it and unlock it it eventually will work. Has a really strong battery so after several tries it still will crank fast. Never happens first thing (I am in Tucson where it is never really cold).. Is it possible that the alarm is involved? Doesn't seem to matter if it was locked or not. When it does start it pops right off and never dies when running. When running it performs well and gets about 24 mpg! Never misses and will run hard right up to the redline in lower gears.

thx

When the car doesn't start??? does the starter operate or not?

The starter always works. Strong battery and starter as it always cranks fast. Either fuel or ignition is not there. After several tries of locking and unlocking the doors it pops right away. This is why i suspect that there may be something in the alarm that is part of an anti theft feature. Is there a module somewhere operated by the locking system that disables the engine?

Your first suspect is OVP relay.

Allways state if the car cranks with a No Start condition b/c we do not know that and the diagnosis is different.
Search OVP and see if yours is the new part #.

Where is the OVP relay? How can I tell if it is the new part # as I suspect it is orig (mine is an early 94 date on drivers door post is 1/94) Sorry for the confusion as I originally implied that each try involves cranking with no start.

Just search "OVP"
..

There are enough threads there on OVP to fill phone book.
Notorious failure part that effects power to your engine management systems.

Behind the panel, behind the battery.

http://catalog.peachparts.com/ShopByVehicle.epc?q=1994-Mercedes--benz-C--80-Body--Electrical&yearid=1994%40%401994&makeid=63%40%40MERCEDES%2DBENZ%40%4063%40%40MERCEDES%2DBENZ%40%40X& modelid=6333%3AMBC%7C1556%3AED%7C10000015%40%40C280&catid=241959%40%40Body+Electrical&subcatid=24200 3@@Overload+Relay&mode=PA

>so after several tries it still will crank fast. Never happens first thing >

This is your statement. I read that as not cranking all the time, specially when you talk about the alarm system switching having helped the condition. Alarm has starter interlock, so that makes me look at starter circuit..whereas I now can see you have engine management condition...
.......regardless ...my mention of this posting tip will help get you a faster responce if mentioning you have crank when posting a NO START condition...Crank and Run condition determine our responce...which is why MBDOC asked the very same question.....The post was just confusing, but no problem...................
I saw your post last night and had you been clear on crank , but no start, I would have answered with possible OVP immediately.
So, on your chassis, OVP is first suspect for a Does Crank, does not Start condition. And they were so troublesome, they changed them to a modified /upgraded part....

I've got the same car. Had the same problem about a year ago. Mechanic diagnosed a bad Crankshaft Position Sensor (CPS). I changed both that and the OVP only to find that an intermittent fuel pump relay was the problem. One telltale symptom was the car would idle strangely sometimes-probably due to lack of fuel.

your getting good help from these guys and I cant offer any other advice except have your bettery tested (probably not the problem) Tucson heat is hard on batteries though. Great to see someone else here from tucson with a 1994 c280, i love mine!

This appears to be a very complex problem. When i first got the car 2 years ago the previous owner stated that sometimes you have to losk it with the door key and unlock it if it doesn't start. Happened once or twice in the first year and always would start after one reset. Thew longer i have had the car the more frequent the problem. It recently has gotten worse. Once it does start it runs perfectly. Just doesnt seem like a voltage control problem.

<doesnt seem like a voltage control problem. >

Sure does to me..........................

1. Spend $90 and get a new OVP.
2. Install it.
3. Problem fixed.

I'm 99% sure that the lock/unlock issue is pure coincidence. Does it always start the first crank after doing that?

Local MB Dealer wanted to replace the crank sensor, EA and wiring harness to the tune of about 3k. I changed the OVP and problem was cured.

i think you are right [dstorey] looking at the wiring diagrams the door lock pump is interconnected to ata module which is located in the trunk.i think that you can unplug it and still run the car.

Can't run that chassis if you unplug N/26 ATA b/c it will no longer Start. You will have to jumper relay K38 pins 30/87 for Starter Interlock Defeat...