need help. loud hitting noise when starting

[justin4260]

i went out to start my truck this morning. i just put a new battery in it and i was going to adjust the air fuel mixture. when i turn the key the engine turns over but then i hear a really loud hitting noise by the started it sounds like. the noise is so awful i stopped turning the key as soon as i heard it. i would take a video of the noise but id rather not make it again. i tried to start it one more time and it did the same thing. i checked the fly wheel and there are wear marks on a lot of the gears. some grinder down spots and some just were it rubbed of the black dried grease.

[no1udknow]

Look at your oil pan for dents. I had that happen to me on my 73 k10, aparently I knocked the oil pan on something and though it didn't make noise right away, from being dented, the spot welds broke loose on the air deflector inside the oil pan and it was hitting the bottom of the crank shaft. It was so loud and hod almost a bonk bonk sound to it. I pulled the pan , knocked out the dent, and welded the plate back down.

[7tee]

I'm not sure if you mean the noise is at the starter, if so it could very likely be the starter drive being that you noted wear or shiny teeth on the flywheel. It's an easy fix if that's it...

[Me&My53]

My first guess would be a broken flywheel.
It could be cracked or broke around the bolt holes.
Joe

[11SECSS]

Yeah like others say check your flexplate teeth ,also check the starter bolts.

[WarMonger]

I was thinking maybe lost a starter bolt. Starter maybe tweeked or kicked a little bit?

[hotrodder]

if it is a automatic check for loose torque convertor bolt

[justin4260]

its an automatic. there is a dent in the oil pan but it won't even start because when it makes the loud noise the engine stops cranking and the truck shakes from it stopping so quick i guess. the flywheel isn't broken but the teeth are worn. the start isn't missing any bolts and the starter has no room for tweaking, it doesn't move at all when its bolted down. i took off the starter and when i took on of the bolts i turn it just slightly and the gear in the starter went back in. it was stuck on the flywheel. Ill check for a loss torque converter bolt. maybe the starter all of a sudden needs to be shimmed? this is the same one the po put on like 4 years ago and its worked fine every time. the dent in the oil pan happened also with the po 4 years ago.

[special-K]

Are you saying it makes a clunk clunk clunk as you crank it? Always, everytime? Could be low voltage to starter. That could mean poor connection at starter, wiring, or possibly neutral safety switch. It could also mean NSS going bad.

[11SECSS]

You should take out all the plugs and see if it turns over easier without any noises . It should spin really fast and make no noises if everything is okay since there will be no compression in the cylinders.

[justin4260]

i think the starter rod may be bent. I've got it off i just have to check it out. i unbolted the starter but left it plugged in and cranked it the starter spins freely. its not like its low on voltage, its like the engine is cranking at normal speed for about 2 seconds and then a really loud bang! the engine suddenly stops turning over so fast the truck rocks left and right. when you look at the starter after the noise the shaft is stuck out and the gear halfway engaged on the flywheel.

[justin4260]

how can i check if my starter shaft is bent?

[Boog]

A bent starter armature is unlikely. At least I've never seen one bend in all my many years. My suggestion is try a couple of starter shims. That should give it a bit more clearance to let the gear engage and release the flywheel. I understand it has been working ok for several years but it's not normal for the starter gear to stay engaged with the flywheel.
So it started fine and ran good up until that morning?
I tend to think you may have a timing problem causing the engine to kick back while turning over or a valve sticking open maybe. Have you had any of the plug wires off for some reason? Could someone have switched a couple of plug wires on you as a prank possibly? Had the distributor loose?

[no1udknow]

perhaps it lost time, check your distributor to see if it is loose. other than that it would be mechanical. What were you doing when this happened? I have also seen what you are describing when a cam fails, or you pull a rocker stud out of the head and a cylinder is vapor locking because the exhaust valve isn't opening

[hamjet]

Put your starter back on and try what 11secss suggested in post 10. or just pull the coil to dizzy cap off and crank it. see what it does and go from there...

[kc69]

So,what did it end up being??.

[snipescastle2]

make sure that little brace/bracket is on the free end of the starter that attaches the starter to the block, that may have contributed to the problem.
Ben

[frankslagoon]

How long has that 'dent' been in the pan and how bad is it.

[justin4260]

Originally Posted by snipescastle2

make sure that little brace/bracket is on the free end of the starter that attaches the starter to the block, that may have contributed to the problem.
Ben

i don't know what braket your talking about.

Originally Posted by frankslagoon

How long has that 'dent' been in the pan and how bad is it.

im not sure. at least 3 years. previous owner dented it didn't tell me how but i bought the truck out of a storage unit it had been there for 3 years.

i found out that the noise was the starter. the starter was engaging and not disengaging so it was stopping the flywheel. put a new starter on and the noise went away

[justin4260]

ok it was the timing. if the timing is to advanced when you try and start it, it fires way to soon forcing the piston back down way to soon and the engine stops turning

[special-K]

So, it kept doing the same thing after the new starter? Now you timed the engine and it cranks fine?

[justin4260]

When I had the old starter I my worked great then I "timed" the engine just by turning it as the rpms raises and stoped when they stopped climbing. Then the noise started happening. After I timed it the distributor was turned all the way to the driver side and that didn't seem right to me so I moved it back to were it was before. I replaced the starter and the noise stopped. Well I got a Timing light set the timing correctly (or so I thought, I was using a scratch that I thought was the timing mark) shut the endings off and later went to start it and the noise was back. So I put 2 and 2 together put the ditributor back to were it was before again and the noise went away. I turned it too much and the noise was back. I was advancing the timing by hand that's why the Rpms were raising before. To much initial timing and it stops the cycinders from turning because it fires way to soon. Also could that have cause my head gasket to blow? Because one of them did.
Posted via Mobile Device

[Custom/Ten]

If your timing is too advanced then yes it could cause the head gasket to blow, among other things. A lot of old timers time by ear, but it's not something I practice seeing how a timing light is pretty cheap. I wonder if you didn't jump timeing when that motor locked up.

[justin4260]

Originally Posted by Custom/Ten

If your timing is too advanced then yes it could cause the head gasket to blow, among other things.

what other things?