Hi All!
I've got a '83 240DL with few miles (around 90k) with a sudden and unexpected case of no-start. The symptom is a typical AMM failure. I can start wonderfully, but it stalls 1 or 2 seconds later. Disconecting the AMM lets it run, but very roughly (limp home mode).
Here is what I have tried so far:
- Checked the resistance of AMM leads according to Haynes manual. No problems here (~4ohms and ~600ohms, and changes properly when I turn the pot).
- Swapped the AMM and plastic intake baffle (between AMM and throtle body) for a used loaner. No luck, same symptoms.
- Checked all the tubes for leaks: vacuum lines, baffles, intake, TB, idle control valve, etc. Nothing found, although I (and 2 witnesses) hear what sounds like a sucking noise or whining somewhere around the idle control lines and valve. Unfortunately, I checked with a stethoscope (ok, well, a tube to my ear) and the sound is just kind of everywhere, not in any particular place.
- Checked the air filter. Seems okay, a little dirty. Removing it doesn't help.
- Removed and inspected idle control valve (checked resistance, too). Looks like new, rotates fine, resistance right on target.
- Checked resistance of AMM, coolant temp sensor, idle control valve, etc, from the passenger side compartment, at the LH control computer connection. Everything seems fine here, too.
- Checked as many wires as I could for continuity at the LH computer connector, and checked every pair for possible shorting, and checked for possible ground faults, and bad ground connections, etc. No problems found. Since this is one of the biodegradable-wiring cars, there are some badly deteriorated wires, but they seem unrelated, and have been completely stripped of insulation for years. In particular, the lead wire for the console coolant temperature sensor (this one connects only to the dashboard, I think, and is positioned just above the knock sensor), the oil pressure sensor (again just for the dashboard, I think), and the little wire coming off the alternator near the oil pressure sensor. All these are totally bare, and doused in oil.
- Tried to check the fuel pressure regulator, but having no vacuum pump thing, the best I could do was detach the vacuum hose and look for dripping gas. I did smell a little gas, but the whole thing is running so rich that my whole yard seems to smell like gas.
So obviously I am a bit out of ideas. And I am running out of favors at my favorite garages -- the first loaned the AMM, to no avial, the second hunted for a vacuum leak without success, and the third tried adjusting my throttle position and fiddling which only made the car sound better but still in limp-home mode.
It is a bit chilly here (5-deg F). But if anyone has any ideas whatsoever, I would love to hear them. Perhaps my loaned AMM is also bad (it also checks out with an ohmmeter)? Perhaps those bare wires are the culprit? Or my huge oil leak in one of the gaskets? The fuel pressure regulator (is there any way to test this more thoroughly?). Bad injectors? Bad LH computer?
Hopeful in Ithaca,
-kev