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300 inline 6 mechanic question

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Old 01-12-2017, 05:44 PM
Jerad Harrison Jerad Harrison is offline
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300 inline 6 mechanic question

OK so I own a 1985 Bronco with 300 inline 6 cylinder. Was driving home from work at highway speed and heard one backfire noise and it died and wont start up again. Pulled it home and started doing some looking around and realized there was no fuel in the filter (had over 1/2 tank). So I pulled the manuel fuel pump off and had someone turn the key and realized the load is not moving and that's about as far as I have went. I am almost certain it's going to be a broken cam or timing gear but my question is without taking her half apart are there some ways to check between the two? I'm no professional mechanic but have enough knowledge to fix most problems but with this I have no prior experience and was just curious if someone could give me some input.
thank you for your time.
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Old 01-12-2017, 05:56 PM
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Pop off the distributor cap and see if the distributor is turning when you rotate the engine. I believe it's also driven off the camshaft. You could also remove the plugs and put a borescope in (Harbor freight has them on sale for ~$60.00 with a coupon) and watch the valves as you slowly rotate the engine.
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Old 01-12-2017, 06:27 PM
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It's more likely that you stripped the drive gear on the distributor. I've had this while driving and it's an instant pop/backfire/death.

As SparkyAl said, pop off the distributor cap.

Then, try to rotate the rotor by hand. You should be able to turn it back and forth maybe a half inch in each direction and then it should snap back straight. If it's gummy and/or can keep turning, the pin that keeps the drive gear in place has sheared.

Pull the distributor slowly so the gear doesn't fall off into the oil pan and either get a new pin or distributor.


If, however, it's solid, your cam gears may be suspect. Disconnect the coil and hit the starter and see if the rotor spins. If not, it's possible you shredded the cam gear.

A way to fully check this without tearing the engine fully apart is to either pull off the valve cover, or pull of the lifter cover on the driver's side of the engine (easier to access and a great time to replace the gasket).

Get a 15/16" socket on the harmonic balancer bolt and rotate the crank (in neutral).
If the valve cover is off, you should see the rocker arms raising and lowering.
If the lifter cover is off, you should see the lifters/pushrods raising and lowering.

If you're rotating the engine and the rocker arms/lifters aren't moving at all, then your cam gear shredded.
Fortunately, it's a non-interference engine so nothing should be damaged.
Remove the radiator and then pull the harmonic balancer (can rent pullers from most autoparts stores) and then remove the timing cover. You should have the gears right in front of you. Replace.

Then, drop your oil pan and remove all the shredded bits of the old cam gear.

Put it back together and you should be good for a long time. If you get metal gears, you'll never have to think about them again.

Keep us posted on how it goes.
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Old 01-12-2017, 08:10 PM
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X2 on the timing gears.
I've experienced this one myself also. The gear on the cam is driven by a steel gear on the crank. The cam gear is a fiber like material and wears over time. Mine let go in a service van with almost 200K miles.
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Old 02-04-2017, 01:09 AM
Jerad Harrison Jerad Harrison is offline
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Update:

Quote:
Originally Posted by AbandonedBronco View Post
It's more likely that you stripped the drive gear on the distributor. I've had this while driving and it's an instant pop/backfire/death.

As SparkyAl said, pop off the distributor cap.

Then, try to rotate the rotor by hand. You should be able to turn it back and forth maybe a half inch in each direction and then it should snap back straight. If it's gummy and/or can keep turning, the pin that keeps the drive gear in place has sheared.

Pull the distributor slowly so the gear doesn't fall off into the oil pan and either get a new pin or distributor.


If, however, it's solid, your cam gears may be suspect. Disconnect the coil and hit the starter and see if the rotor spins. If not, it's possible you shredded the cam gear.

A way to fully check this without tearing the engine fully apart is to either pull off the valve cover, or pull of the lifter cover on the driver's side of the engine (easier to access and a great time to replace the gasket).

Get a 15/16" socket on the harmonic balancer bolt and rotate the crank (in neutral).
If the valve cover is off, you should see the rocker arms raising and lowering.
If the lifter cover is off, you should see the lifters/pushrods raising and lowering.

If you're rotating the engine and the rocker arms/lifters aren't moving at all, then your cam gear shredded.
Fortunately, it's a non-interference engine so nothing should be damaged.
Remove the radiator and then pull the harmonic balancer (can rent pullers from most autoparts stores) and then remove the timing cover. You should have the gears right in front of you. Replace.

Then, drop your oil pan and remove all the shredded bits of the old cam gear.

Put it back together and you should be good for a long time. If you get metal gears, you'll never have to think about them again.

Keep us posted on how it goes.
Update: it was the Cam gear sheared, put on a steel one and cleaned out oil pan and put new oil pan gasket on and she is purring like a kitten
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Old 02-04-2017, 11:06 AM
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Sounds great, and glad to hear it!! And thank you for the update, not enough people do that.


On that note, would you mind giving this guy some guidance and help? It sounds like he's in the same boat you were! It'd be very appreciated.

http://www.ford-trucks.com/forums/14...s-in-carb.html
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Old 02-04-2017, 10:03 PM
Jerad Harrison Jerad Harrison is offline
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Quote:
Originally Posted by AbandonedBronco View Post
It's more likely that you stripped the drive gear on the distributor. I've had this while driving and it's an instant pop/backfire/death.

As SparkyAl said, pop off the distributor cap.

Then, try to rotate the rotor by hand. You should be able to turn it back and forth maybe a half inch in each direction and then it should snap back straight. If it's gummy and/or can keep turning, the pin that keeps the drive gear in place has sheared.

Pull the distributor slowly so the gear doesn't fall off into the oil pan and either get a new pin or distributor.


If, however, it's solid, your cam gears may be suspect. Disconnect the coil and hit the starter and see if the rotor spins. If not, it's possible you shredded the cam gear.

A way to fully check this without tearing the engine fully apart is to either pull off the valve cover, or pull of the lifter cover on the driver's side of the engine (easier to access and a great time to replace the gasket).

Get a 15/16" socket on the harmonic balancer bolt and rotate the crank (in neutral).
If the valve cover is off, you should see the rocker arms raising and lowering.
If the lifter cover is off, you should see the lifters/pushrods raising and lowering.

If you're rotating the engine and the rocker arms/lifters aren't moving at all, then your cam gear shredded.
Fortunately, it's a non-interference engine so nothing should be damaged.
Remove the radiator and then pull the harmonic balancer (can rent pullers from most autoparts stores) and then remove the timing cover. You should have the gears right in front of you. Replace.

Then, drop your oil pan and remove all the shredded bits of the old cam gear.

Put it back together and you should be good for a long time. If you get metal gears, you'll never have to think about them again.

Keep us posted on how it goes.
I just had this very similar thing happen to my 85' Bronco with the Straight 6. My cam gear was shredded and because of this was keeping my distributor rotor from spinning since the cam was not moving. As stated above. It is a little work to remove and replace but with a little research and renting a 2 prong puller for the gear and harmonic balancer puller you should have no problems getting life back in your ride. Hope this helps you.
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