Om606 no start at 80C - PeachParts Mercedes-Benz Forum

treetops · #1 04-25-2022, 09:04 AM

I’m trying to fix this no start condition on my 99 300D, 265K miles. I’m thinking it’s the crankshaft position sensor after replacing the fuel lines-air bound.

The car has been a little finicky to start after running in the past, but always did start after a few tries. This all started 2 Fridays ago coming back from NJ. I got caught in a traffic jam and the engine warmed up to just at the top of the 80C mark and stayed there for about 15 mins or so and then the car stalled. Here's where I am currently.

1st attempt of the day, she will start up w/o issue. It seems that after the engine has warmed up to 80C that the issue comes up. If I turn off the engine, it will crank but not start. It definitely seems to be temperature related. At anywhere between 60-80C the car cranked over, but no start. If I let about 40 mins go by, temp lowers to below 60C, she will startup w/o issue.

I have replaced all the plastic lines to the main filter and IP, except for the return line on the engine side of the IP. I replaced the pre-filter. I replaced the o-ring on the shut off valve(I think my mechanic replaced that a few years ago) and the o-ring on the return line from the IP to the main filter. Lastly I replaced the fuel hose from the feed pipe on the firewall to the preheater on the engine block.

I am seeing air in the line from the bottom of the shut off valve to the lift pump when revving. I occasionally see air bubbles in the 1st line from the preheater to pre filter, but not in the other lines. I've checked for leaks under the shut off valve and lift pump with a paper towel, but nothing conclusive. I hope this helpful and better than "it wont start"

After reading a number of posts here and other forums I’m thinking CPS is the next logical step. Thoughts??

barry12345 · #2 04-25-2022, 08:38 PM

Get a can of cold spray at any electronic parts supplier. After car warms up and will not start spray suspect part or parts one at a time. Starts right up you usually have it.

All you are fundamentally doing is reducing the 40 minute cool down to less than a minute. No guarantees but it should work.

jay_bob · #3 04-26-2022, 11:18 PM

Been there done that, definitely get a MB branded replacement one, the Bosch 'substitute' does not work!

The thread title is 'CAN bus trouble' but the problem ended up being the CPS.

W210 CAN bus issues

and a "Diagnose Dan" who had a similar problem with a Bosch 'replacement':
https://www.youtube.com/watch?v=8dtv1kRNF_U

I wonder if I had the same problem with the signal polarity...

treetops · #4 04-29-2022, 02:09 PM

Called the dealer Monday and got the new CPS yesterday, installed it today. JayBob I did read your thread and heeded the warning-get it from the dealer.

I’ve had the intake manifold off, which I can do in my sleep now 😂, so getting at the CPS was straight forward. Cleaned up the years of crud and sprayed some lubricant. No big deal.

I ran the engine up to 80C, shut down and was able to get 5 consistent starts. I did wait from 2-7 mins between starts to see if I could reproduce my previous issue. Glad to say I could not. We’ll see over the coming days if the issue resurfaces.

barry12345 · #5 04-30-2022, 10:10 AM

Great news yet buying parts before proving they are defective. Is termed shot gunning. If a part is dirt cheap it does not matter. It can very much when they are not.

We frequently get asked for help. Also being presented with a horrendous list of what has been changed with no results already. In many cases. There are usually workable tests instead.

That in most cases work out cheaper to apply first.

engatwork · #6 04-30-2022, 08:23 PM

I've gotten to point of replacing original CPS with new MB oem units between 230,000 to 250,000 miles on my personal cars.

treetops · #7 05-01-2022, 09:18 AM

The diagnosis/choice to buy the CPS was not based on empirical testing, rather an informed progression based on what was done and other’s knowledge shared here. I agree that diagnostic testing is the best way to go-OBD, voltmeter…etc. This forum has been a life and wallet saver for me and others. I’m very grateful for the wealth of info and help available from everyone here.

The CPS had not been replaced in my ownership(140k of 268k miles) and the fuel lines were due anyway(they were browned out if that makes sense)

jay_bob · #8 05-01-2022, 06:55 PM

Quote:

Originally Posted by barry12345

Great news yet buying parts before proving they are defective. Is termed shot gunning. If a part is dirt cheap it does not matter. It can very much when they are not.

We frequently get asked for help. Also being presented with a horrendous list of what has been changed with no results already. In many cases. There are usually workable tests instead.

That in most cases work out cheaper to apply first.

I hear you about the parts cannon...

But in this case, the sensor fails intermittently, and when it fails the engine just *stops dead in its tracks*. Even though on the 606 there is no reason for it to do that, the fuel is inherently in time with the engine through the injector pump on the timing chain. The later CDI 648/642/651 engines you need that data to know when to squirt each injector so shutting down on signal loss is necessary.