93 300e won't crank, need help diagnosing
 

Initial problem: failed emissions testing yesterday, due to high hydrocarbons. Drove to local parts shop to get spark plugs, since I was told by emission shop that was the first thing to suspect.

As I got back in car to leave parts store.....car would not crank. Heard fuel pump run briefly and a single click from engine compartment, then nothing. Lights, radio, windows etc all work fine. I tried starting while jigling shifter all around neutral and park to no avail. Guy in store came out with portable battery jumper and tried that too..still nothing. I then figured the OVP relay had gone bad again, since this is how car acted about 4 years ago. So today I purchased a new OVP relay and put it in after work...still nothing (no crank, fuel pump runs, and only an occasional single click when turning key to start). I also had searched forum last night and had decided I would try jumping X27, as per Arthur Dalton's informative posts (hope you are reading Arthur!). But unlike the posts I read last night which all indicated starter engaged upon jumping 12V to middle terminal of x27 today, I got nothing. Only a small spark at terminal/jumper indicating I had current. I am now assuming I have a starter/solenoid problem.

I had to get the car towed back home tonight from auto parts store since I was unsuccessful in getting it started. And I really don't want to buy any more parts unnecessarily (I now have and extra non/refundable $60$ OVP relay). Any suggestions from anyone on how to procede? Arthur?

How easy is it to get at the starter on that car? Perhaps I should rephrase that... how difficult is it to get at the starter on that car? If you can get to the terminals at the starter, you can easily determine if the starter is the problem. (And it sounds like it is.)

If you jumpered from bat + to center terminal of X27 w no crank, then the problem is at the starter/solinoid or a bad ground.[ assuming bat is up on charge]
Take a jumper cable and go from the bat - and go to a good engine ground
and retry with + to x27.

Also, take a good look at the wires going from the X27 to the starter [ behind oil filter]..common for those to have the same problem as the engine wire harness.

Suspect is starter.

hope this flow chart helps

That is a RUN chart..he does not have CRANK.

And we know he has power to X27...so the problem is downstream from X27.

it tells him the 3 major areas to check when the car dont start but doesnt give all things to consider ie bad battery etc

You don't get it.
We are working off the Starter circuit schematic ..and the Starter circuit is the complaint...not Run complaint.

NO CRANK...see that ?????

NVM figured out the suspects causing the problem.

I've had the exact same experience on MB's and had 3 different issues.

1. Defective Battery, most common. I couldn't even jump start. Replaced battery, no more problems.

2. Defective Neutral Safety Switch. Started the car with a push button start switch. Replaced NSS, no more problems.

3. Defective Starter. It started out intermittent, passed bench test at one auto parts store, then failed at another. Replaced starter, no more problems.

Check all the basics first.

hes not getting nothing at x27 which means NSS is out of the picture.
Battery, wiring, corrison, bad grounds., starter solenoid

Thanks for the responses. I tried the grounding jumper as you suggested Arthur, no effect. Lost daylight so no chance to check wires closely from x27 to starter. Priced rebuilt Bosch starter/solenoid today at $180. If I can't find fault in wires from x27 to starter guess I will move forward with replacing that. Anybody have replacement procedure for starter replacement on this rig?

That is the basic idea... except it is not that he is getting nothing at x27... it is that when he brings 12v from the battery to x27, he is by-passing the NSS, K38 relay , and ign sw....
That is the reason we use X27 for the test point..that eliminates all cabin controls upsteam , as you can see on the schematic. So, the problem has to be downsteam from X27.

If he were getting nothing as you suggest [ meaning no power at X27] than the problem would be upstream..NSS/K38/Ign sw/fuse5.

So, X27 is a convienient test point in this circuit to isolate the problem up or down from that point..we use it b/c of it's simple convienience...it can also be used if one gets caught with his pants down somewhere with a bad NSS/K38 circuit..by jumping to that x27, it will get you home w/o a tow truck.
I have seen guys that had a bad NSS and used that jumper for a year to start their car every time the NSS failed. .....:)

Download 15-7100.pdf from FileFactory.com

Download that file

<Anybody have replacement procedure for starter replacement on this rig?
>

The top bolt takes a long extension [ I use a 20" and a 6" combined] and you get way back and sneek in over the top from the upper right side of the tranny.

If that harness is OK, then the suspect is sol or brushes...sometimes you can get a starter with hung up brushes to spin if you give it a smack while someome holds the key over..that will verify starter.

OK, let's be old school about this. First, confirm that your battery is good. Next, if you can get to the terminals on the starter... the big terminal connects directly to the battery positive terminal. You should have battery voltage here at all times. The small terminal energizes the solenoid when you turn the key to "start." Take a screwdriver. Use it to bridge the big terminal to the small terminal. If the starter cranks the engine, your starter is good. If it doesn't, your starter is bad. (Or your engine is seized, but we don't want to go there.) But be VERY careful not to touch the screwdriver to anything else when it is touching the main terminal!