W140 started after 8 months in storage, idled for 5 min, then died & now won't start!

[slimak9]

1992 400SE.

I took this W140 out of storage after 8 months and it started without any hesitation or problems. I let it idle for about 5 minutes and then it suddenly died.

I tried to start it back up, but got nothing. I tried again a few more times, leaving a few minutes in between, but still nothing.

I started by siphoning out all of the approx 1/8 of fuel that was left and filled it with fresh new gas, but still nothing. I proceeded by removing the Injectors which I'm going to get tested tomorrow.

Last year I did:
* Spark Plug Wires Set
* Both Distributors and Rotors
* Both Ignition Coils

Two years ago I did:
* Spark Plugs
* 8 New Fuel Injector Seals and O-Rings

Anyone have any ideas on what caused it to suddenly die and other areas that should be examined?

Somehow I have a feeling the injectors are not the problem.

Appreciate all the help in advance.

[slimak9]

...just wanted to add that it cranks, but won't fire.

[slimak9]

like I thought, it wasn't the Fuel Injectors. had them tested and even got new o-rings as the current were starting to crack, but it wasn't the issue preventing the lack of firing. the guy at the shop who tested them even said they spray and perform like new...at least some good news.

after doing more research, similar issues people had said that changing the Crankshaft Position Sensor has resolved their intermitent no firing. could the CPS be causing this complete no fire even after the car sat overnight to completely cool down? or could the Ignition Module be fried?

any way to test the CPS or Ignition Module? I'm probably gonna visit a shop in my area that has old MB's and maybe I can find a W140 to try a temp sensor and module swap before forking the cake on new parts.

...back to searching I go.

[compu_85]

You can hear the fuel pump?

-J

[slimak9]

yes the fuel pump is running. even disconnected one of the lines under the hood and had fuel pour into a jar while in the on position.

[Christine in FL]

Have you pulled a plug to see if there is spark?

[slimak9]

I haven’t pulled a plug, but I sprayed some "starting fluid" through the throttle body and noticed a light flame inside the intake when trying to crank, so I assume there must be spark.

Would you recommend pulling each plug to test for spark?

I'm finding so much info on similar no fire issues, but nothing identically to mine. Most people are able to turn on their vehicle after a few minutes or when it cools down. It seems many are still referring to replace the Crankshaft Position Sensor in those similar situations.

I've also found people referring to the fuel pumps, fuel pump relay, and OVP. I can hear the pump running while in the ON position for a few seconds and it seems to provide pressure in the lines as there was a noticable burst of fuel when I unscrewed the lines to remove the Injectors.

I have no idea how to check the OVP beyond checking the three 10A fuses on top, which were good.

I'll continue researching throughout the weekend and probably end up purchasing a new CPS on Monday.

[Ferdman]

slimak9, I guess it's possible the ignition control module may be causing the problem as the engine compartment heats up, but in my experience the engine won't even start with a bad ignition control module. Swapping a known good one would be a good idea.

[slimak9]

I removed the Crankshaft Position Sensor today and found that at the sensor end, the wire was cracked and exposed. A light pull on the sensor caused it to separate from the wire.

It looks like the heat over time cracked the wire insulation and the car sitting there for 8 months I’m sure also didn't help.

I ordered a new CPS today, should get it within a week. Dealer wanted $274 list, ******** AZ had it for $123. Fortunately it’s not a rush, so I will wait. I will post the results after it arrives. Cross your fingers!

[slimak9]

The CPS arrived. I also ordered a Fuel Pump Relay ($16) at the same time, which on many forums was talked about also being the cause of a no start or intermittent shut off.

I hooked up the CPS and the car fired right up , but it had a really rough idle and would shut off if you didn't keep your foot on the gas.

Eventually after shutting off a few times it wouldn't start back up again! Each time I was cranking, it sounded much better than it did with the old CPS. (You could hear it fire the odd time, but there just wasn't enough to completely start it).

So I swapped the Fuel Pump Relay, but got nothing.

Went back to researching, and found the following TSB "Engine hard to start, long cranking time and/or dies again" it was applicable to these models/engines:
119.97 in W129 & W140
119.96 in W129
It reads to add a 0.5mm washer in-between the Crankshaft Position Sensor and the contact surface of the screw that holds it in place. It states that the clearance between the segment on the flywheel and CPS is too low.

So I did just that, and it started right up and has been running smooth for the past 2 days.

I should also add that this new CPS with the 0.5mm washer eliminated a small rough idle I had before putting the car into storage. Overall I find the engine starts quicker, runs smoother, and even notice that the RPM's are running lower at idle.

Who would have though that a 2 cent washer would save the day!

[Ferdman]

slimak9, any reason why the 0.5mm washer would be necessary after all these years running without it? What changed to require the washer?

[slimak9]

Fred, that is a good question. Nothing has been done to the car in 8 months while in storage. I ran fine when put into storage and now I can say it runs better.

Maybe someone more experienced can add to this...

As for the Ignition Control Module, my tech that does all my electrical work says they rarely go bad. The main cause of failure in a ICM is Reverse Polarity if you hook up the battery incorrectly. But he added that the fuses in the OVP should stop damage to the ICM should someone connect the battery incorrectly.