2004 3.0 automatic. I had hit and miss for awhile.Turn key and seems the starter would spin faster than normal,no start,turn key off turn key on sound normal perfect start.It did this off and on for several days. Went for a coffee at Speedway turned key, fast spin on starter and no start,turned key off tried restarting with key off and on several times no start, so I had it towed down the street to the mechanic. Bad starter ? solenoid,crank sensor? What do you think?? Help Please.

 

Bump

 

Yes, bad starter

It was spinning fast because gear wasn't engaging Ring gear on flywheel/flexplate, so no resistance

Most likely issue is the solenoid on the starter motor, it was not pulling the gear OUT to engage flywheel/flexplate, or you would have heard grinding noise

When you turn the key to START that 12v activates a solenoid on top of the starter motor that pulls back a rod, that rod is on a pivot and so pushes starter motor gear out to mesh with gears on the flywheel/flexplate, the ring gear
When the solenoid fully moves back it also connects the positive battery cable to the starter motor, like a relay does, so its a combo solenoid/relay unit

Drawing here of whats inside: https://qph.fs.quoracdn.net/main-qim...ff623d026eb9a8

There is also an "overrun" clutch, this allows the ring gear to spin faster than starter motor without damaging starter motor, i.e. when engine starts ring gear is moving faster than starter motor, the overrun clutch spins the starter motor gear BACK into starter motor housing which disengages it from ring gear


You can often buy replacement solenoids, up to you, but most just replace whole starter motor as a unit

 

Thanks Ron.Ended up being the inertia switch code, was hit and miss cutting off the fuel.the mechanic replaced it, total cost $70. Starts right up.

 

Good work, glad you got it fixed

Odd issue from your description, starter wouldn't turn engine any faster with or with out fuel pump power.
You had a crank but No Start issue, just for future reference

Yes, inertia switch should be changed if it ever trips, it can be reset but usually won't hold.
If you purchased vehicle used then it may have been in an accident, this trips the inertia switch, and repair places often don't replace it just reset it

But odd again that it started up and then didn't and then did, inertia switches don't reset themselves, failing fuel pump relay can act that way

 

I guess my description wasn't accurate, because the truck always started immediately and never heard it whirl like it did. I will look up the parts you recomended and get them replaced. I highly regard your replies. Thank You!