Loud Bang after replaced starter

gmc
2500

#1

Hear a loud bang after replacing starter,actually I didn’t replace its a friend mechanic did…but for some reason he cant figure out why there is a bang,im thinking the starter was not installed properly an it jamming with the fly wheel. he thinks crank shaft…he is at the garage now checking things out,any help asap would be greatly appreciated…


#2

Just off the top of my head I’d suggest that the starter wasn’t shimmed properly.
Knowing when the “bang” occurs, much more about the vehicle (year, engine, mileage, and tranny type would help) might also help.

Is your friend working to a repair manual or just “winging it”?


#3

Neither he is a mechanic…It’s a 97 GMC 2500…Not sure why he can’t figure out the bang noise but yea a few people said the same…It’s not shimmed at all…Gonna give him a call and have him checked that out…Thank you


#4

Does the bang only happen when turning the ignition key? Does the truck start? Did it make this bang before? Where did the starter come from? Could be the wrong one, or boxed incorrectly, or even just built wrong.

I’ve bought starters that had to be flipped on the mounting plate to be installed correctly before. It happens.


#5

Is he than using Alldata or Mitchells or some other subscription database? This is typically what mechanics have these days.


#6

Cracked flywheel if it is not improper shimming. By the way, does anyone but GM use shims on the starter? Never seen shims on a Mopar.


#7

I don’t see that suggested anywhere in the thread. Did you pick up on something that I missed?


#8

I would venture this has the 5.7 engine. If so there could be a bad distributor cap causing it to cross fire inside the cap or the crank sensor connector is full of oil causing the crank sensor to send errant signals to the PCM causing erratic spark.


#9

Loud bang after replacing starter.- yes, an improperly shimmed starter is the most likely cause, but a cracked flywheel will make a racket too. To check it out, remove the starter and turn the engine over by hand looking for a crack radiating in from the ring gear.


#10

Excellent advice. Also do a visual inspection of the new starter, does the mechanic notice anything weird going on w/this new starter while it is on the bench? Does it have the correct number of teeth on the little gear that sticks out and engages the flywheel? Does it seem to extend the same distance when you pull it out? Does it rotate that gear in the correct direction? If nothing found, what I’d do next, try a different starter.

Edit: It’s possible to get the starter installed a little cockeyed on its mounting surface too. You’d think this was all but impossible but guess who did it one time ? … lol . It’s b/c of where the starter is located, right at the junction of the engine and transmission. Visibility can be very poor in that area without removing a bunch of stuff first. Esp when working with the car on jack stands. On a lift visibility wouldn’t usually be a problem.


#11

Cracked flexplates are quite common on this generation of GM V8 engines . . . and the succeeding generation, as well

These damaged flexplates can cause very deep sounding noises, which are often mistaken for other things

I like Oldtiimer’s way of thinking :blush:


#12

OP, reading your post, is seems you had ONE loud bang when you tried to start the car, but it has been fine ever since.

In that case, I’d ignore it.

Or do you get the loud bang every time you attempt to start the car?