Long story short......Inherited this truck, starter wouldnt engage sometimes. I put a new starter, solenoid, new flex plate in it. mechanic had wrong flex plate, shelled the transmission pump.
Rebuilt transmission and with all the new parts, the starter doesnt engage more often now.

Is it the starter? Or could it be the starter cable not supplying enough amps?

Any suggestions would be great

 

The simplest thing to do is, do a voltage drop test on the cables. More than 1 amp on the positive cable or .5 amp on the ground cable are reasons to replace them.
Remember , the system has to be under load, that is attempting to start the engine while doing the test on the cables.
If you see any signs of corrosion it is easy and not expensive to replace them.
Just make sure to remove the negative cable first , replace what you want to replace then last connect the negative cable back on to the battery

 

You said "the starter doesnt engage"
In simple term please, does that mean it's NO CRANK NO START?
You said 1990 F150, there is A LOT MORE to that. Check my signature below and provide the missing info.
Do you have a voltmeter you can check voltage?

 

The starter runs every time, it has a spinning sound like not engaging the flexplate. Not a gear grinding noise. never a grinding noise.

 

1990 F150 XLT Lariat 2 dr extended cab, 5.0 engine 4WD, Automatic

 

If the starter spins without engaging the flywheel/flexplate, the drive inside the starter is defective.

If the starter assy has been on there for a few years,the simplest thing to do is just replace the starter assy with a rebuilt unit.

If you can, take the old starter with you to match the drive end with the replacement because the ends are a different dimension between a std trans and an automatic.


While you have the starter out , take a good look at the teeth on the flexplate to make sure there are no missing teeth.