30 second run time then dies, must wait (hour?) before it will restart

[C420sailor]

The smoking gun is to attach a code reader capable of live data and try to start the truck. If it reads 0rpm while cranking, it’s very likely the crank sensor.

My truck would be fine unless I let it sit for a few days. It would start, run for maybe a mile, then quit. Had to let it sit for 45-60 mins, then it would fire right up like nothing happened. Often wouldn’t bother me again until I let it sit for a day or two.

Replaced the sensor and it all vanished. This was months ago.

Edit: it only threw a code for it once, despite the many many times it did this. Seems this failure tends to evade the PCM’s diagnostics.

 

[Mr. Alligator]

^^^^Sensor.

You might be able to overthink this one. These only cost about $20-$30. (Of course, try to get Motorcraft.). Not a lot of labor either.

Good luck.

 

[EB4X]

Running out of time tonight but went under and wiggled the connector. Didn't take it off. Started up and stayed running. It kind of bothers me though because that makes me feel like it could be a wiring issue instead of the sensor. I'll run it longer tomorrow to do a better test

EDIT

 

[freak]

^^^^Sensor.

You might be able to overthink this one. These only cost about $20-$30. (Of course, try to get Motorcraft.). Not a lot of labor either.

Good luck.

Yeah but corrosion on the connection might make it seem like the sensor is bad. It bugs me to throw parts at it without knowing for sure.

 

[C420sailor]

same, but there also comes a time when it’s not a bad idea to replace certain parts preemptively/by mileage. Especially when it’s a cheap part that can leave you completely stranded.

I normally hate firing up the parts cannon, but if doing so will improve the overall reliability of the truck regardless, it’s not a total waste

 

[EB4X]

/\ Exactly, and having a sporadic shorting / cutting out situation like this can tax the sensor so that it is NOW more prone to actual failure/ premature failure. My old OBD1 setup would not pick up a failing o2 sensor, and put in a chinese dpfe sensor which worked for a little over a month, but these situations caused me to fire up the parts cannon, fortunately I wheeled and dealed on ebay and got (good) parts inexpensively, so in hindsight it's nice to know I wont have to worry about / address those functions (25 + year old) parts going forward.

 

[freak]

All a moot point now. Broke the sensor taking off the connector. Oh well. Probably good that it happened. New part from Ford dealer tomorrow. Kinda pricey at $72 but I don't want to deal with it again. I notice that the mounting holes are oblong. Are we supposed to set the gap to something specific?

 

[freak]

I opened it up. Looks almost perfect. Reads 430 ohms. Could be failing as it heats up I'm sure.

 

[freak]

For kicks I un-spooled the wire from the coil. Wasn't broken anywhere. No discolorations or places where it was stuck to itself. Pulled off about 54 arms lengths (about 6 feet) of wire which is around 300 feet.

 

[freak]

New sensor is in. Runs and starts fine so far. I have a strong suspicion that the problem was poor contact at the sensor connector but will never know. Thanks everyone for all the help!

 

[C420sailor]

I think it’s just an age thing. I feel like we see problems in batches. Crank position sensors have been failing a lot lately

 

[Metalface]

I think it’s just an age thing. I feel like we see problems in batches. Crank position sensors have been failing a lot lately

Haha... accurate..

 

[freak]

I think it’s just an age thing. I feel like we see problems in batches. Crank position sensors have been failing a lot lately

Well it's BS that Ford can't make a sensor that lasts any more than 415,000 miles.