Second new starter still grinds when starting

I’m so lost! My friend dropped off his (99 Chevy van 5.7l) cause he installed a rebuilt starter and was getting a grinding noise when he try to start it. So I told him to buy a new AC Delco starter and two new starter bolts and drop off the van. I installed everything and tighten everything to torque specs. It still grinds but not as bad as the other starter. So I thought maybe ignition. I hooked up my remote starter switch to the starter n when I engaged the starter with my starter switch it cranks the motor perfect. So thought it might be the ignition or relay. I pulled the starter relay and used the fuel pump relay. Crank it with the key with no fuel and it sounds perfect. Maybe Relay? So I Run out buy a new relay turn the key and back to grinding again. I pull the fuel pump relay turn the key and it starts perfect! Plug the fuel pump relay back in and the starter is back to grinding again. So if the fuel pump is not running it starts perfect. Give the motor fuel, the starter grinds. WTH! So I then hooked my starter switch back up. I turn the key to the run position so I have fuel press the button on my starter remote…back to grinding again! So it’s not the ignition switch ether. Looked at teeth on the flywheel they are all still there and doesn’t look warn, no cracks and not warped. Any one have any ideas? Is it even possible to hydrolock?
The starter doesn’t grind all the time. First 4 or 5 seconds it spins the motor fine then you get a grinding noise. Turn the key off, turn the key again, starter spins the flywheel for a second or two then it grinds a little then the motor starts

I am not a mechanic but I know GM’s used to have shim’s on the mounting plate could that be your problem too many or not enough shim’s?

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Inspect the positive battery terminal for corrosion.

There may be a voltage drop occurring so that when the starter, starter solenoid, and fuel pump are operating at the same time, all have a voltage drop where the starter solenoid can’t hold the starter drive gear into the ring gear.

So, no grinding when the fuel pump doesn’t operate. And grinding when it does.

Tester

Yes grinds with with fuel no grind with out fuel. I can spin the flywheel perfectly for 15 seconds straight with out fuel. I Checked and cleaned all connections. Brand new battery too. I guess I can see if I’m losing Amps or volts when I start it with the fuel pump running. Maybe the wire from the starter to the battery is bad. But yes, strangely when I pull the relay for the fuel pump and turn the key it cranks the motor perfect. Doesn’t the fuel pump only run for a few seconds while starting it? I tried to turn the key until I hear the fuel pump kick off n tried starting it n it stilled grinds

The ac delco starter saids I don’t need shims. Plus i did try it just made it worst cause with shims it pulls the starter further away from the flywheel

If it only grinds after the engine fires up then it is almost certainly mounted too close to the flywheel. You don’t need to remove the starter, just the outer bolt and loosen the inner bolt ~1 turn. Then slip a thin shim into the gap, install the outer bolt, tighten it and test start. If indicated replace the thin shim with the next larger. Most every parts store sell a pack of GM shims on the HELP aisle.

Only my experience but I put in a new starter that made bad grinding noises,I took it out, going to return and said to myself I should video it. I had read up on shims etc., and was thinking ok here we go. I put the starter motor back in, and made an effort to snug it up get it as close to the flywheel as I could. Hit the crank and it did fine for 50k miles afterward. The mysteries of life! 03 trailblazer. There was a little play with the bolt holes on mine.

All ready tried shims didn’t work. Shims was the first thing I tried

Make sure your starter bolts are super tight.

Has the transmission been removed lately? If so carefully inspect to confirm that the engine and trans mate together fully. Heck, check that anyway.

Now you say that he did tell me he recently got the torque converter replaced. Definitely need to check that. Good call Rod-Knox :+1: