Ranger engine cuts out over bumps, but electrical does not lose power.
I drive an 88 ranger, 4x4 5 speed. With 488,000 kms on it, it's served me well. For the past year it has randomly shut off over large bumps then instantly bump started itself and kept going. This only ever happened over the really hard bumps in the road, the jolters. Last month this happened and she died right down, did not bump start itself and keep going. Pulled over, jiggled some wires at the cap and plugs, and just about anywhere a wire could be, got back in, fired it up and drove to work, very gently. Driving home that evening it did it again. Jiggled some wires, fired it up and drove to the gas station, pulling into to the gas station it did it again, over a very, very small bump, and would not restart. I found a shitty connection at the plug connector on the ignition coil, cleaned it up as best I could with some wd40 and a safety pin, put the wire back in the plug, fired it up and got home. Thinking that must've been the issue, I cleaned and resoldered the connection to the plug, and went for a drive, the small bump pulling out of the driveway and it died again, and would not restar again. Pushed it back in the driveway, and over the pas few weeks have replaced the coil, the cap and rotor, plugs and wires, the EEC and fuel pump relays. The truck always starts now, but is still really trying to die over the smallest bumps. I only drive it around town now when I need a pickup truck, but would like to continue using it as my little commuter. When it cuts out, the the check engine light comes on, the headlights stay on and the radio keeps going so i know it's not a connection at the battery. I'm stumped as to what I should look at next, I was thinking fuel pump but I don't think the cut off would be instant if it were the pump losing power for a split second.
Sorry for such a long write, just want to be as detailed as possible. Anybody with any ideas, or who has had the same problem please help. Thanks for your time.