Mack Jenkins

My 2018 F150 Crew/4x4 55k miles will not turn over more than once or twice, in turn wont start, AFTER the truck has been running for a while. This only happens when I've been driving longer than just a trip to the grocery, lets say driving out to the farm 30miles away. What usual happens is I will then stop somewhere, maybe gas station, turn it off for 5min and when I go to turn it back on it will do the slow turnover one time and then nothing. Sometimes, I will then cut it off and when I try again it will crank up.

The only thing consistent about this problem is that if I let the truck sit overnight, or a few hours, no matter how long I have been driving, it never has a problem cranking up. It is never an issue cranking first thing in the morning.

The battery has been load tested and results like a brand new battery. Symptoms don't seem like alternator, since it is never short on power after several hours of sitting.

Could starter somehow be affected by the heat? Literally I am wondering if the heat of the engine is causing something in the starter to expand, not spin, and bog down the engine......

I am disappointed in the low milage and really hope to fix this. The Ford dealer was as useless as bad directions.

Thank you for your help.
Mack

Blackbuzzard

Intermittent starter behavior?

Do the standard four voltage drop tests under load.....which is the basic starter system diagnostic method. (Assuming you have some electrical diagnostic background.)
Use vom with min max mode and a couple long aligator clips.Should take about 20 min

1 battery + - terminals: doesn’t fall below 9.6 while cranking

2 bat+ to solenoid +big wire input, should be near zero volt drop. More than 0.5volts and theres a wiring issue.

3 solenoid/start ground to bat neg terminal…..should be near zero voltage drop. More than 0.5volts and theres a wiring issue.

4 Solenoid control side (ign ON) to bat + terminal. should be near zero voltage drop. More than 0.5volts and theres a wiring issue.

If all the above is good, then odds are very high its a bad starter.

Do this while starting or attempting to start! Otherwise the numbers are meaningless.

Mack Jenkins

Thanks Buzzard, I'll be running through those tests as soon as weather allows. Any possible explanation for the intermittent starting issue? Again, it only stalls cranking after running a while, never first thing in the morning.

Mack

Blackbuzzard

Not sure....cranky bendix, heat affects it a bit, bad spot on commutator? Might not BE the starter. Until one gets in there and measures and tests stuff, it's just a good guess.


Good Luck!

Dfrost419

Mack Did you ever resolve your issue? I’m having exact same issue as you?

wondering if it was starter or electrical…

Thanks!

tristanfernandez831

I am having the same problem. Can anyone help me out? Please. Thanks.

David Hineline

Literally 4 replies above you said what to check, and your response, can anyone tell me what to do to fix this?

haulinarse

I have the same 2018 truck with 5.0 and same problem. Only happens when pulling a trailer when drivetrain is fully hot. Definitely seems battery is not the issue. My buddy who is pretty smart with motors says maybe the starter windings are getting hot is causing issue. Was hoping there was a smoking gun to get an answer. Will try the 4 options above. Thanks for add.

Firedaniel

Did anyone figure this out? Same exact problem today. Battery is new alternator is good. Has to be starter right?

haulinarse

Does everyone in this thread have 5.0? I'm guessing so.....my truck is still doing it. When I had my battery changed last year I had them put in an H7 instead of H6. I think an H8 will fit in battery tray and I will upgrade to that next time to see if additional cranking amps help. Mopar has a nice battery blanket for H8 when time comes. Ram OE 5033397AE - Battery Cover.