300CE won't start, botched tune up - PeachParts Mercedes-Benz Forum

300celvr · #1 10-23-2006, 01:17 AM

Amazing how something so simple can go so wrong. 1990 300ce running kind of rough, idles poorly. Decided to change rotor, rotor cap, plugs, injectors, seals, seats. Rotor and cap looked like old welding parts on the inside, really burnt and arc traces. Plugs didn't look much better, twice the gap, really burnt and electrode about half the size of normal.
Injectors were a little more work. Had to remove the throttle body and injector assembly to acces number 3&4 injectors. They looked in bad shape and partially plugged on some.
Very pleased with myself about 4 hours later. Let the ignition on for a few seconds to pressurize the fuel system, turned off and did it a couple more tiimes. Cranked over the ignition and it ran beautifully for about 2 seconds.
Cranked again and again and again. Nothing. Cracked the bleeder screw on the top of the fuel dist. fuel ran out under pressure. No sparky? Any clues for the misguided? Thanks!
Greg

t walgamuth · #2 10-23-2006, 05:55 AM

spark is not what i would suspect. it ran then stopped.

i suspect fuel pressure. did you check your fuses? (sorry to be so obvious)

tom w

Hit Man X · #3 10-23-2006, 06:19 AM

Got the rotor on correctly? If it's 180° out it wont' start... but if it sputtered, well... it probably is okay.

TB back on correctly?

300celvr · #4 10-23-2006, 05:19 PM

I spoke with a Mercedes Mechanic friend of mine, who mentioned that If I replaced the injectors, the fuel/air ratio would need to be adjusted, as it would not atomize properly. Before I could ask why, he had to go, his boss was calling him. Dose not make sense to me, as I thought the injectors were the items that atomized the fuel. I did not mess with anything else regarding the fuel system.
Again, it runs for a second or two after I use some starting fluid, although I don't want to continue, as I know starting fluid is bad for the engine. I am hoping my friend will come out a rescue me so I don;t have to get the car towed. When this is all over, I will post the fix, as it might help somebody else out of a problem before they make one for themselves.
Greg

A264172 · #5 10-23-2006, 06:07 PM

Quote:

Originally Posted by 300celvr

I spoke with a Mercedes Mechanic friend of mine, who mentioned that If I replaced the injectors, the fuel/air ratio would need to be adjusted, as it would not atomize properly. Before I could ask why, he had to go, his boss was calling him. Dose not make sense to me, as I thought the injectors were the items that atomized the fuel. I did not mess with anything else regarding the fuel system.
Again, it runs for a second or two after I use some starting fluid, although I don't want to continue, as I know starting fluid is bad for the engine. I am hoping my friend will come out a rescue me so I don;t have to get the car towed. When this is all over, I will post the fix, as it might help somebody else out of a problem before they make one for themselves.
Greg

I don't know if your duty cycle has been messed with to correct for a less efficient electrical system, or if that would even effect the lambda system. Is that an early M104 engine?

300celvr · #6 10-23-2006, 06:59 PM

It is a 1990 model year, with the 24 valve 3 ltr. engine. Car is parked at home so I don't have exact engine model number. Hopefully my mechanic friend will be out tomorrow and get me running again. I will post the cure to my situation as soon as I know. At this point, I would not recommend any body but a trained mechanic to change out their injectors, no matter how straight forward it would appear to be!
Greg

300celvr · #7 10-25-2006, 12:38 AM

As noted earlier, I was dissapointed in not getting the car started after spending all that time with the injectors and plugs, rotor and cap. While I was waiting to have my mechanic friend do a house call to get this tub running again, I thought I would have another go at it.
I was able to get the car started by depressing the air flow plat slightly. I then noticed a sucking sound. Much to my dismay, I found a couple of hoses and vacuum tube lines that came undone when I moved the intake and fuel manifold assembly out of the way to get to number 3&4 injector.
The big one that made a real difference was the one that connected to the cold start valve, and another that went to the throttle body senor. Rehooked them up and away we went. Really runs great now. Both these were under the fuel injector pump assembly and hard to see, even in daylight. Dosn't help that I am old and see like stevie wonder. Anyway make sure you get everything hooked back up when you approach the injector replacment. Really something even a "technically Challanged" indvidual as my son call me, can do!
Greg