Non-starter 107 (and technical overconfidence)
I got called for help with a non-starting '83 380SL three years ago. Cranked endlessly, but would not ignite and run. After checking the forums here, the problem was worked down rapidly and correctly to a failed fuel pump relay. Bravo, M-shop posters! You prevented a tow-in. I fixed it where it had failed.
Yesterday, same car, same symptom, this time while the car was up on ramps in the driveway for a coolant change.
I instantly said, "Must be the same thing as last time, fuel pump relay, easy fix," while patting myself on the back.
Uh, nope. I jumpered the pins on the relay to get the pump running, and still no start.
Fuel level was quite low. I figured that it *had* to be a case of a dry pickup in the tank starving the pump because of the ramp angle. Went and fetched a big can of fresh gas.
Nope. Uh, does the fuel pump run? Seems to do so. I can hear it when I jumper the fuel pump relay.
Battery good? Better than good. Doing great. Turning out more cold cranking amps than a cheap Exide ought to be able to.
Distributor okay? Yep. Clean under the cap, only minor wear, rotor looks fine. No moisture inside or outside.
Is there spark? Pull a cylinder wire and check while turning over. Yep, seems strong. At least that one cylinder should fire.
Starter solenoid engaging? Yes, the engine happily spins all the stuff at its front.
Metering plate stuck? I pulled the airbox and checked. No.
Geez, for a guy who was confident he had it nailed right away, I'm pretty confused now.
The car will crank until battery exhaustion (I have a charger on it in between start attempts, to prevent deep discharge).
Yesterday, it cranked with no hint of ignition. Today, it coughs a little roughly, as though it's considering starting. I tried pouring a bit of fuel directly past the metering plate. Nothing.
Any hotter wrenches than I am care to take a shot at diagnosis? Am trying to tell myself that it's not a sick fuel distributor.