Jagermonster

Hello everyone. I hope I am not duplicating posts or posting in the wrong one. I made a quick search and did not find anything similar or that can help me solve my problem.

My vehicle is a daily-driver W163 ML320 1998, with close to 200k on the dash, I have owned it for about 6 years and ever since I have been fixing different sort of issues, thanks to the information in this forum. It recently started stalling or shaking when engine was hot. It was not much of an issue until it started dying when you stepped on the gas (usually from a full stop). I would then turn the switch back to the off position, wait for a few seconds, and restart with no issues.

While trying to fix the shaking issue, I recently changed sparkplugs, wires and all 6 coils (all bosch, and sparplugs are NGK platinum) because it was giving me misfire errors on 3 cylinders and wires looked worn out. I also changed some gaskets and seals trying to mitigate the stalling and shaking (intake, egr, throttle body o ring, injector o'rings, brake line connector and the rubber thing on top of the throttle body [all MB stealership ordered parts]), and all vacuum hoses were replaced (8x3mm). All of that because I thought it might be a vacuum leak. Running improved a lot, it would not stall or stop, but would still shake a little after being in heavy traffic.

2 weeks ago I arrived to a Walmart and parked to buy groceries. When I wanted to go home, engine would not start at all. Waited for a couple of hours, thinking maybe it was too and something related to the CPS. No go. Ended up towing it back home. I scanned it using a "half-decent" scanner that can read MB codes, there was nothing but one code for the ac pressure switch being in short circuit and another for a door lock issue.

Things done so far:
-checked fuel pressure. about 50lbs.
-checked spark using a tester - somewhat weak spark
-checked for voltage getting to the coil connectors - 12v on all 6.
-checked all fuses and relays - all good and all with power (specially the ones for the coils and the engine functions)
-checked the switch - I had replaced it less than a year ago as it had burned. This one looks like new. Replaced it with a genuine MB part.
-checked for power coming from the key/switch/ignition - All good when moving to pos. 2.
-replaced the Crank Position Sensor.
-LED on the dash flashes when turning the key, and also confirmed with the scanner that the key is working fine.
- tried a second key (working fine) and same symptoms.
-battery was replaced about 7 months ago with no issues at all until now.

after checking all that, engine just turned, but did not start.

I found something in an MB forum where someone was saying it might be the computer. He ran a wire from the + in the battery, to the cable in the middle of the connectors of the coils and it would start. I tried that and it worked just fine. Removed the cable, and the engine died and won't restart unless I put that wire to the coils. However, after the third or fourth attempt of doing this with a "mickey mouse cable", the engine started working just fine. And it worked fine until last Saturday, when it came back to the same issue.
I have a theory and please guide me and correct me if I'm wrong. The first time this happened, I had the AC on. It was not turned on again until last Saturday, when the engine died again. What is the relation and my theory? Read next.
There is a code "Stored&Current" that reads:
"B1 232-000 The sensor for refrigerant pressure supplies implausible values: Short circuit to positive"

Do you think both problems might be related, and causing the engine not to start? Should I start looking for a new computer? The switch not providing enough Amps even when it "looks" fine?

At first I thought this was the pressure sensor. I disconnected it yesterday, but the code is still current and the engine still not running.

Any advice and help would be highly appreciated, and my apologies for the long post. I am trying to provide as much detail as possible on what's been done.

Dfixit1

I may be a bit off here on this one but MB is REAL fond of protecting the A/C compressors if low pressures etc exist, but to kill the engine might be a streach if all is working well. There are 1 or 2 pressure/temp. swithces,Binary or Trinary. Mine has 1 and it's a Trinary switch that sits to the right upper of the condenser coil. If you go that route It was easier for me to remove the cross member to get to and R&R that. You seem fairly mechanical and might could swing replacing that your self. Last I looked they are 50-75 bucks then would need to vac down and replace the 134a and that needs to be spot on, mine was 26oz or that switch won't let the comp. and fans start for cooling. At the age of our SUV's that is a fairly easy do and even if thats not the complete cause it might be a contribuating factor. So while you in this deep look at trying that. Also be sure to clear all old codes then run and recheck after all the work you have done and will do. Be sure to let us know what you find out

Jagermonster

Thanks Dfixit1. I will check on the power lines and see if there is anything going on there. I have already unplugged the pressure sensor that is above the dryer (well, somewhere around there) and the code still shows as current in the scanner.
I will follow the lines from the connector all the way to the fuse box and see if I find anything. I will update with findings as soon as I have time to check on it because my 9-5 job keeps me quite busy so I might just do that over the weekend.

Dfixit1

I'm still working on my ML. Have a new hose ordered and pressure/temp switch on the way too. My Indie said he will clear codes after I get the system able to work with the repairs. He said some models have to have codes cleared with that expensive reader he and MB use in their service depts, that generally insures the vehicle is in a shop to be seen. While I was working on this a couple weeks ago I had the trinary connector loose and pulled up where I could work some VooDoo on it. I had ran a jumper wire from the battery with an attached 12g wire down in the switch, green wire I believe. With the inside switches on then the hot wire attached the clutch came on and ran so I was able to get the remainder of the freon into the system. My calls for 26oz and I was careful to weigh the 12oz cans and had put just over 27 oz in. It was close but I still had an issue so I bought a new switch and the hose it attaches to and with hi hopes after I get the parts {in the mail| all that will get codes cleared and cross fingers that fix works and not have a further issue with the module that runs that system.