Engine cranks over but will not start?

Okay. With light connected, same as sw plugged in, it gives me 12.5v then goes to zero. With sw out of circuit, unplugged relay zero goes to 6.92v. Should be zero if relay is only connection to wire.

Exactly! I agree. If relay is good, I swapped all 4 into fuel pump position, then it can only be one thing. Connectors at inertia sw plug. The 6.83 volts is at the relay contacts that goes to the cpu pin 40. So I would say floating voltage. You? As I understand, cpu mostly connects the ground circuits. True?

Thank you for all the help and talking it out with me and the patience. I will chase out the wires and connectors and get back to you with results. Will be good to resolve this issue.

Okay, wires all ohm out good. Getting 12.5v to relay coil. Ground to relay coil good. All comes back to connectors at inertia sw. If I have running and move wires around on back of plug, it quits. Going to get tool to remove pins from plug. Has to be bad crimp. Makes since. While idle, it will run for four seconds after disconnecting. So on a rough road or bump, it has four seconds to reconnect. Will let you know.

The connector is under dash so hard to see good Took pics of to find one and the female end is all black. Does not look good. That is the bad connection. Must of not been tight, overheated and carboned up. Located a Dorman at Amazon, same at Autozone and O'Reilly but $10 cheaper. Cutting off old connector. Tie those 2 wires plus one for my light so I can drive and monitor. Want to be sure it is fixed before I put switch back into circuit. Then will connect new connector and put all back normal. Thank you for all your help Roy! I appreciate your responses and guidance.

And to help, here are pics.

Good luck all.

Good idea! Thank you!

Hi Roy! Update: have been driving it. Made five plus trips. Working great. I took old plug apart. Crimp was good. Has to be loose fitting connection which would account for wire being warm to the touch before. Wire now normal temperature. Still have light on it for monitoring the proper sequence. Waiting for new connector.
Your website is fantastic. So glad to have the knowledgeable resource.

Okay. New connector. Dealer did warranty on inertia switch all new, works great. It was s bad wire connection in connector. About 600 miles. No problems. Wired in 12v light on pump side for monitoring.

Hi Roy! I have driven the 04 Ranger 4.0 all summer and no troubles. Then Oct 6th, no start. My test light was normal sequence, light on for 2 seconds, then constant when cranking. Tack was bouncing and it would run like 200rpm stumbling along every time I tried it. In parking lot, could not hear pump. After waiting about 30 minutes, started right up. Got home. Off on off on, started fine. Fuel pressure 65psi. Then Nov 5th, same thing, only I had fuel pressure gauge with me. I had 10 to 12 psi while cranking. Light normal. Tried fuel cap off, could not hear pump. Noisey. Waited 30 minutes, Key on had 65psi, started right up. Now what. Only 85 degrees outside. Coming home waited in mile long stop and go traffic. Before no start, traffic moving normal. What I s your thoughts Roy?