W210 has starting issues
 

This problem has been going on with increasing severity about a year now and it's getting to the point where j think it may just not start one day. What happens is usually after I've driven it a while I park and get back in and the car won't crank or it will crank Rpms go up then down and car shuts back off. It takes a few turns of the key till I am finally able to start the car. It does not always do this but the issue is becoming more prevalent. I changed the cps and it did nothing. And getting mixed stories from mechanics.

Help us to help you by putting the type of vehicle in either the text or your signature => I assume it is a petrol engined vehicle because you didn't post in the diesel section.

Have any of the mechanics made an attempt to read error codes?

Are you saying that when warm the engine has starting problems and if it does start it will rev high and then stop?

Oh sorry forgot about the diesel I have the 98 w210 e320 sedan no diesel. When the car starts its fine but when it gives me issues it will do one of two things a slight crank then cut off or it will turn over, start and then just cut back off. Sometimes if it really takes a while to start I get that red battery charge indicator. If by warm you mean that the car was recently driven then parked yes this is when the problem occurs usually at a cold start in the beginning of the day it starts up fine no issues.

Have you or a mechanic tried to read the engine management error codes? These days many mechanics reach for the code reader before they even open their eyes...

Yea one mechanic told me I need a whole new eis another said it is my transmission. I know they hooked it up to the star machine but I don't think they found anything definitive.

Well it is unlikely to be something like a neutral safety switch - the starter shouldn't operate. I'm not sure if something wrong with the electronic brain on an automatic transmission would stop an engine from starting or encourage it to shut down. Wait for others to chime in on that.

As the response from the mechanics isn't especially helpful I'd start by cleaning electrical contacts and checking for damaged wiring.

It is possible to get little data loggers that attach to diagnostic ports so you get a better idea of what is going on rather than just a snapshot in time.

Often with these, a failing crankshaft position sensor wil cause difficulty with warm starts. The symptoms are that it cranks, but doesnt fire.
The no-crank could be key/EIS related, but could also be an intermittent bad electrical contact. Check and or clean all grounds and battery contacts, and the starter cable first to rule it out before dropping big $ on MB parts.

Your initial post says that the RPM goes up? We may be on to something here. MB's of that vintage were affected, believe it or not, by surface rust on the teeth of the ring gear. This condition resulted in flywheel acceleration being affected during starter engagement. The CKP interprets this as a running engine and aborts the crank. I've seen this many, many times. The tell-tale sign is a brief chirp when the starter gear meshes with the ring gear. Listen closely and let us know what you hear.

I actually do hear a quick squeak or chirp when I attempt to start the car sometimes when it fails. I just noticed it recently as it can only be heard outside the car near the engine. Also I changed the crankshaft position sensor about a year ago it never really did anything.

In fact last time I was at my mechanic they put some grease on the flywheel which seemed to reduce this issue. Is there anyway I can check myself to see if rust is an issue?

This is what you need
Optimol Paste TA p/n 08452-215 Mercedes Benz Grease 1KG for Sale - FSdownload.com

Thanks this sounds way better than replacing my eis is there any info for applying this stuff I'd like to see if I can put it myself. Or does it have to be up on a lift.

The fix required pulling the starter and applying the paste from there. You can rotate the engine from the crank pulley bolt (in neutral, parking brake or chocks set) in the direction of normal engine rotation to check all the teeth.

When they applied it at my shop I don't recall exactly but I don't think they removed anything. Seemed to only take about a minute.

No need to remove the starter, just the plastic inspection cover at the bottom of the bell-housing. Make sure you get the paste between the ring gear teeth.