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1980 - 1986 Bullnose F100, F150 & Larger F-Series Trucks Discuss the Early Eighties Bullnose Ford Truck

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  #1  
Old 05-10-2012, 02:46 PM
jacrawley jacrawley is offline
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83 F150 300 carb backfire no longer runs

My friend borrowed the truck to haul some garbage a few blocks from the house it backfired out the carb and no longer starts. It's getting spark the compression on all cylinders is 90 to 100 lbs. I have dumped gas straight it and it still won't hit. At TDC the rotor is about 25 degrees before the #1 plug post.

Any ideas? Someone said timing gear skip but 25 before (advanced?) isn't really all that off is it?

thanks
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  #2  
Old 05-10-2012, 03:08 PM
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Yes that is a lot. Have you tried to loosen and move the dizzy some to try and start it? I have even had to move the plug wires around the cap to get them to run long enough to home or to the shop. And yes I do believe she has jumped timing. Unless she has no spark as ya have not said.
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Old 05-10-2012, 03:10 PM
1983F1503004x4 1983F1503004x4 is offline
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Originally Posted by jacrawley View Post
My friend borrowed the truck to haul some garbage a few blocks from the house 1) it backfired out the carb and no longer starts. It's 2) getting spark the compression on all cylinders is 90 to 100 lbs. I have dumped gas straight it and it still won't hit. 3) At TDC the rotor is about 25 degrees before the #1 plug post.

4) Any ideas? Someone said timing gear skip but 25 before (advanced?) isn't really all that off is it?

thanks
I've had a pretty long and aggravating day, so if I sound kinda mad, whoops.

1) If it backfired out of the carburetor and no longer starts, then you can go ahead and assume timing. A backfire occurs when the spark plug on a particular cylinder fires while a particular valve is open. If it's through the carburetor, it's due to the intake valve being open. If it's through the exhaust, it's because an exhaust valve is open (or burned up). Backfires can occur because of lean fuel mixture, bad rocker arms, incorrect ignition timing, burnt valves, sticking valves, etc.

2) If you're getting spark on all the cylinders, and dumping gas in it won't help it start either, then timing. Also, your compression looks low. How many miles is on the motor? May be time for a head rebuild or boring over.

3) How do you know it's 25 degrees before the #1 plug post? Does your timing mark on your balancer or whatever kind of timing tape on your balancer let you read that far back?

4) Timing gears won't "skip" on the 300 inline-6. It doesn't have a chain. If any "skipping" happens, it's going to shear the teeth off of the timing gears (it doesn't have a chain, it's direct gear-drive) and the cam timing will go wacky, and this CAN show up as bad ignition timing if a light is put on it. Some motors will continue to run if teeth shear off because the later model 6's have metal gears, whereas the earlier ones have fiber gears. The transition from fiber to metal occurred in sometime between 81 to 84.

25 degrees off of the number 1 post and you wonder why it won't start. That's WAY more than enough to %#$@* things up.

Get a timing light, set your timing to 8 or 6* before top dead center, and tighten the bolt down on the distributor hold down clamp.

Then, don't let your "friends" borrow your crap anymore. That's one we hear kind of regular here. People let their "friends" borrow their vehicles or something of that sort and it comes back broke.

Precisely why I won't lend anything I have.

If re-setting the timing fixes it and then the problem occurs again, then you can suspect timing gears or something wrong with the distributor or something of that nature. But get the old girl timed first and see what she does. 10$ bet it fixes it.
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Old 05-10-2012, 03:28 PM
jacrawley jacrawley is offline
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Quote:
Originally Posted by 1983F1503004x4 View Post
I've had a pretty long and aggravating day, so if I sound kinda mad, whoops.

2) If you're getting spark on all the cylinders, and dumping gas in it won't help it start either, then timing. Also, your compression looks low. How many miles is on the motor? May be time for a head rebuild or boring over.


3) How do you know it's 25 degrees before the #1 plug post? Does your timing mark on your balancer or whatever kind of timing tape on your balancer let you read that far back?


25 degrees off of the number 1 post and you wonder why it won't start. That's WAY more than enough to %#$@* things up.

Get a timing light, set your timing to 8 or 6* before top dead center, and tighten the bolt down on the distributor hold down clamp.
The ODO has just rolled over but perhaps this is its second roll over. Not the original owner.

I mean 25 before when looking at the rotor not with a timing light.

thanks for the advice
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Old 05-25-2012, 11:06 AM
jacrawley jacrawley is offline
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I have now removed the timing cover and the cam timing gear. That was a real bear. The timing gear was aluminum which I think means it is not the original(cloyes brand). It had some broken teeth but the dots still lined up which means it did not cause the timing to go out. The gear broke apart when removing it with a gear puller. This caused the tip of the puller to snap off in the end of the cam. Will I need a new cam? or can I get the gear on without that hole? I tried getting the tool tip out of the cam with no luck. Even if it would come out the threads are ruined in that hole.

I am now unable to pull the crank gear. It has no threaded holes and is to close to the engine to put a gear puller behind it. I think if I remove the main bearing cap I could get the puller back there but this involves dropping the oil pan which I would like to avoid. Does anyone have any magic tips for removing this SOB. Is removing that main bearing cap a bad idea?

Oh and before removing this stuff I reset the rotor to #1 at TDC and it started so it was definitely the timing that was off but how did it get off if the timing gears were not?
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Old 05-25-2012, 11:06 AM
 
 
 
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