Intermittent starting

[ThePenguinKnight]

Got a 94 Ranger STX 4x4, 4.0L with 268K on it (original, no significant engine work done). 6-8 months ago she decided to occasionally not start; cranked fine till the starter died, replaced the starter and cranked fine since then, but didn't fire. A quick spray of carb cleaner in the intake normally made it fire right up; figured it was probably a fuel issue, and I lived with it till today when I replaced the fuel pump and filter and went about my day.

Its behavior was curious: it would fail to start, then 5-10 minutes later it would fire up fine and run perfectly. Never died when the engine was on, but after stopping for any random length of time (anywhere form 5 minutes to 2 days) it would occasionally decide to crank but not fire.

After driving off-and-on for ~3 hours, the truck failed to start. I spent about 3 hours thereafter doing KOEO and ER tests, jiggling and inspecting wires, and generally trying to figure out a pattern for it starting/nostarting. The only correlation of events I can find is that when it fails to start, it appears to not be turning on the fuel pump or ignition (as it now doesn't even cough with starting fluid), and the check engine light does not come on either (always comes one when the key is turned to the "ON" position before starting). I've spent 20 minutes not moving except to turn the key on and off, with no discernible patterns to when it fails to turn on the systems (judged by the lack of fuel pump noise and CE light).

I'm not sure I've expressed the issue well enough, but hopefully that's something to start with. I'm somewhat baffled at the moment, and any help would be appreciated in diagnosing the problem. Thanks ahead of time

 

[289-tiger-]

Shot in the dark, but try swapping the relay modules in the power distribution box under the hood for the engine control and fuel pump to see if the pump starts working KOEO.

Good luck

 

[ThePenguinKnight]

Forgot to mention that I also replaced the fuel pump relay, so that one's brand new. I've tried swapping them anyway, to no avail.

As I mentioned, when it fails to fire, I've tried spraying starting fluid and carb cleaner (seperate attempts) directly into the air intake, and the engine did not even cough when I tried to turn it over (cranked, but no spark).

Another thing to note, if the fuelpump and CE light do not come on as I turn the key to the "ON" position, I am also unable to start the KOEO procedure by either voltmeter or CE light flashes.

My dad said the behavior makes him think it is the vehicle computer acting up, but I have no way of testing that. I'll be contacting the dealer come Monday, but I figgured I'd see if anyone else had run into this one before. Thanks again.

 

[robbieo11]

CHECK GROuND WIRES FOR CORROSION