Well, well, well... I’m back! And now the Disco is stranded in the snow. Since bypassing the ECM and running the fuel pump relay directly from the ignition switch, we’ve put 300 happy, trouble-free miles on the truck. It’s climbed steep grades, waded through snow, been up on the highway, run errands, and generally been terrific... Until this morning, when it quit while warming up, and then wouldn’t restart. Cranked and cranked, no fire. My first thought was that the wire bypass bypassing the ECM for the fuel pump relay must have come loose. Nope. I can hear the fuel pump running, and I have a little geyser of fuel at the fuel rail. Just for grins, I swapped multi-function relays. No dice. Irritated, I went inside to stew about it. After an hour or two on poking around online, I still didn’t have much in the way of a new plan, but I remembered that way back when the whole no-start saga began in a grocery store parking lot, I’d managed to get the engine to start by pulling the IAT sensor. Imagine my glee when the truck started instantly after pulling the IAT plug. Just as an experiment, I plugged the IAT back in, and the truck kept idling away happily. I left it to idle for a few minutes, and then drove a short distance, shut it down, ran an errand, and came back... truck started without a hiccup! Drove a bit further stopped to fill the tank, and wouldn’t you know it, the old war horse started without hesitation. Guess the IAT is either intermittently failing, or a red herring. I hopped in the Disco, and headed out for a longer drive. It ran as smoothly as it ever has.
So imagine my surprise (or lack thereof) when after several hours of working, I came back to the rig to find that it won’t start. My IAT-pulling trick does nothing (I really think that’s a red herring) and after 90 minutes of fussing, fretting, checking connections, swapping relays, I called my wife for a ride. In the pitch dark, we ended up leaving the Disco where it sat, on top of a hill, in 8” of snow, out of reach of any AAA tow truck I’m aware of. Great.
Tomorrow morning we’re headed back up to try to replace the 300-mile-old CKP sensor, as that seems the most likely candidate for taking the truck down. After that... I’m at a loss. I’ll report back...