Irishflyer97

After searching the forums, not coming up with anything similar. 1993 F150, 5.0. Truck ran when parked, next morning, nothing. Replaced ignition module, wants to run, but wont stay running past 1 sec. Fuel pressure is 38. Replaced plugs (fouled after too many attempts of no start, did replace the distributor when old one under inspection was shot. Now for the puzzler. It stays running when I was using a remote starter at the fender relay, with the wire from the ignition switched unhooked. Hook it back up, and truck immediately dies, with no restart. Replaced ignition starter switch, no change. With KOEO, that wire has about 100 ohms to ground, but becomes hot when key is in start postition. I am guessing something in the run circuit is grounding out through that wire to the relay, but not sure where that might be. Any thoughts?

Steve83

Don't worry about similar things - all that matters is YOUR truck, so focus on it.That's not much for us to base our opinions & suggestions on. How many miles? What maintenance/mods/damage/repairs have been done? What trans & other factory options? Even tire size, gear ratio, & color can help us understand the truck's overall condition. Click this, read the whole caption, and put ALL the details into your signature:


(phone app link)The battery was dead "nothing"? Or turning the key caused "nothing" - not even the radio or dash lights "nothing"? Be specific & thorough.Why? What test did the original fail? With what (brand, PN, & source)? Did the replacement pass the same test that the original failed?Does it die instantly like the key is being turned off? Or progressively like it's running out of gas? Does the exhaust become smoky as it dies? White, gray, or black?With what? Did you set their gaps?With what? What test did the original fail? Define "shot".Do you mean the R/LB wire? Does it die instantly or progressively? Do you mean the starter doesn't engage?Why? With what?

Did you keep the original parts? It sounds like there was nothing wrong with them, and they're probably higher-quality than the replacements, so I recommend putting them back on.How exactly did you measure that? Where was each meter probe, and what position was the key in? Was the wire still connected at either end? If not, where exactly did you disconnect it?Don't guess. Learn how the system/circuit works, then test it according to published procedures to diagnose its condition before changing or replacing anything. This caption explains the ignition system, and how it's connected to the R/LB wire:


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Irishflyer97

Plugs gapped at .55, per spec on sticker.
1993 F150 5.0 4x4 187,000 miles.
Non factory exhaust.

Wire was tested unhooked from relay, with a Fluke meter. When running if you reattach the relay wire (r/lb), truck dies instantly, like ignition and fuel cutoff. Any attempt to restart with wire attached results in truck running for a half second, then shutting down. It is repeatable, removing the wire and jumping relay will start truck quickly stay running.
When initial problem happened, truck would crank, no fire. Module was taken to local OReilly and tested bad. Replaced with BWD module.
My theory is that inside the ignition starter switch Run was shorted to Start, so took a chance on an Echlin switch. I will look at the diagram to see what circuits are on the wire.

Irishflyer97

Replaced with Motocraft plugs. R/LB was still attached at ignition switch end. Does that wire show a path to ground when key is off?

Steve83

Of course - through the starter relay windings.


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Irishflyer97

Oh, I meant with the R/LB wire disconnected. I'm finding ground back through the ignition switch/wiring.

Irishflyer97

Update. Did get it to run. Key on, set to run. Energizer wire removed from relay solenoid on fender, and using a remote jump button to trigger solenoid, truck will start and run. I am reading voltage on the energizer wire when unplugged from solenoid, voltage disappears only when ignition module is disconnected. If truck is running, and you reattach the energizer wire to the solenoid, truck dies instantly, like all spark and fuel was shot off. Could my ignition module (third one, all previous ones have been tested as bad, as per parts store machine. Brand is BWD.) be bleeding voltage back onto the energizer wire? There is voltage on the wire, but almost no amperage. A voltmeter can measure the voltage and not kill the truck, but a test light has enough of a direct patch to ground it will kill the truck when testing the wire. Another symptom I didn't think was related, and had forgotten about, but the transmission doesn't upshift at the normal rpms, you have to rev up to 3,000 rpm, let off, and sometimes it will up shift. The pump pressure is definitely higher, and this is an E4OD transmission. Could a bad solenoid in the tranny be shorting my ignition module or PCM, giving me odd voltages and faulty shifting? Is this something than can be typical of Ford trans electric solenoids?