C36 Starting Problem: OVP, CPS, Wiring Harness are OK; whatelse??
 

Hello,

My 96 C36 with 75k + miles currently have a problem starting and I can’t seem to find an answer (fix) by searching the forums for previous posts; only recommendation of what I can do.

Problem: When starting the car, it would take at least 3 to 4 cranks before it would turn over. Once it starts, however, and within minutes of shutting it off, it will start again with no problems. But if I let it stand 10 – 30 minutes, the car would require 3 to 4 cranks again before it would start back up.

The car also performs as it normally would when it starts; no loss of power, no erratic idling, No CEL, and or anything out of the ordinary.

Forum Recommendations: Bad Over Voltage Protection Relay (OVP) as it is common to go bad. I replaced this and the problem did not go away. Check bad fuses and relays.

Next Step: I gave up and went to the dealer for them to diagnose and fix. The dealer had my car for over two weeks and was not able to re-create and diagnose the problem – they think I’m making it up. They said they performed the following checks: Electrical short, OVP, Wiring Harness, Gas (water; bad tank from gas station), Clogged Fuel Rail, Crank Positioning Sensor (CPS), and blown Fuse/Relay, Spark Plugs, Coils, and found nothing. With the chance to potentially charge me a significant amount of money for any of these services, they didn’t find anything wrong with the car, but once I got the car back I still had starting problems. I escaped without paying a dime for the diagnostic services and I was provided with a 2011 C300 as a loaner for two weeks – not bad.

I am looking for some feedback from C36/W202 owners and mechanics that have experience with the same symptoms.

Thanks!

Might not be it, but the CPS is usually something that is intermittent when it fails. And during normal diagnostics will most likely test good.

If what you are saying is that, intermittently, when turning the key the engine would crank but not catch, I had the same problem last winter on my C230. No CEL, no codes, mine was caused by the fuel pump relay. Swapped it out and it never happened again.

I will try the fuel pump relay swap.

hello,

Question:
does the car start up on first try in the morning(after 8+hours ) ?

you may want to consider checking the following, the next time the NO START issue pops up again : 1 Do a CPS test
2 do a fuel pressure test

both tests can be found on this forum.

good luck

My 92 500Sl m119 is having the exact issue. I presume it's the pump or the relay. I will be testing it tomorrow and will report back - otherwise PM me if I forget

Obvious question is, what's the commonality between an m119 and an m104 AMG in this area? If any?

Problem solved!

It was a leaking Fuel Pressure Regulator.

Thanks timmyr for pointing to the right direction.