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Thursday I hauled a large trailer load of wood, no problems.
Friday I did the same. The truck was not running right. It acted like it was not getting enough fuel and low on power, and back firing. I am thinking the fuel filter is getting plugged up or the plug wires are damp and it's misfiring.
I got the load of wood and got it delivered and it's running worst, really lacking power and back firing.

I made it within 3 miles of home and it quit. By the time I walked home my daughter had just came home form College for Christmas break with the Suburban. I used it to bring the trailer home (thinking it might not be there the next morning).

By now it was 5PM so I decided to wait to tow the truck home for daylight.

It was 3:30PM before I could get help to tow the truck home. No EASY way to get it into the pole barn, so I had an hour of daylight to work on it. New fuel filter, new air filter, new spark plugs, cleaned cap and rotor. Still no start and out of daylight.

I am thinking the pickup coil in the distributor has failed, or the brain, box or coil.

Next day I tried a spare brain box, still no start. So off to the auto parts store to buy a pickup coil. Not in stock, have to order it. You would think they would have parts for a 36 year old truck :banghead: So I ordered it for next day deliver.

Picked up the distributor pickup coil and installed it today. Still no start. My next thought is it jumped time. Before I pull everything off the front of the engine. I put a socket on the crank to turn it by hand to see how far of the rotor is from #1 when I get it turned to TDC. When I check it's off by a cylinder and 1/2, meaning it's not pointing at #1, but between the next two terminals on the distributor.

I don't know why, but I grabbed the rotor and tried turning it. And it turned all the way back to #1, almost 1/4 of a turn. Being gear drive from the cam it should not have turned!

I pulled the distributor and found the roll pin for the drive gear sheared. What was left of the roll pin in the shaft had bound up the gear about 80 degrees off.

A new roll pin later, distributor ready to install, but does not want to seat. I hooked up a remote starter button and start turning the engine while tapping the distributor shaft with a rubber mallet. FINALLY it seats.

After everything is reassembled, I try starting it. Fires right up!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! and runs like it's old self.

That was my 4 day weekend. All because a 1/8" x 3/4" roll pin sheared. At least the drive gear did not fall off into the oil pan.
 

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Since you've already done a tune-up, I'd say you're good to go for the next 30 years or so.:thumbup1gif:

Just can't beat a good old truck!
 

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So let me get this straight. Your 1978 Ford broke down, and you ended up fixing it with a hammer? :thumbup1gif:

I love old trucks. I miss my '78 F-100, and have the itch for a 70's era F-350 extended cab with a 460. They're not very common, but there's one running around town here that looks really nice.
 

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Funny! While I was reading your thread I was thinking timing chain or distributor drive gear issue. Seen it many times over the years on mid-late '70's Fords. Good to get to the root of the problem though isn't it?
 
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Thursday I hauled a large trailer load of wood, no problems.
Friday I did the same. The truck was not running right. It acted like it was not getting enough fuel and low on power, and back firing. I am thinking the fuel filter is getting plugged up or the plug wires are damp and it's misfiring.
I got the load of wood and got it delivered and it's running worst, really lacking power and back firing.

I made it within 3 miles of home and it quit. By the time I walked home my daughter had just came home form College for Christmas break with the Suburban. I used it to bring the trailer home (thinking it might not be there the next morning).

By now it was 5PM so I decided to wait to tow the truck home for daylight.

It was 3:30PM before I could get help to tow the truck home. No EASY way to get it into the pole barn, so I had an hour of daylight to work on it. New fuel filter, new air filter, new spark plugs, cleaned cap and rotor. Still no start and out of daylight.

I am thinking the pickup coil in the distributor has failed, or the brain, box or coil.

Next day I tried a spare brain box, still no start. So off to the auto parts store to buy a pickup coil. Not in stock, have to order it. You would think they would have parts for a 36 year old truck :banghead: So I ordered it for next day deliver.

Picked up the distributor pickup coil and installed it today. Still no start. My next thought is it jumped time. Before I pull everything off the front of the engine. I put a socket on the crank to turn it by hand to see how far of the rotor is from #1 when I get it turned to TDC. When I check it's off by a cylinder and 1/2, meaning it's not pointing at #1, but between the next two terminals on the distributor.

I don't know why, but I grabbed the rotor and tried turning it. And it turned all the way back to #1, almost 1/4 of a turn. Being gear drive from the cam it should not have turned!

I pulled the distributor and found the roll pin for the drive gear sheared. What was left of the roll pin in the shaft had bound up the gear about 80 degrees off.

A new roll pin later, distributor ready to install, but does not want to seat. I hooked up a remote starter button and start turning the engine while tapping the distributor shaft with a rubber mallet. FINALLY it seats.

After everything is reassembled, I try starting it. Fires right up!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! and runs like it's old self.

That was my 4 day weekend. All because a 1/8" x 3/4" roll pin sheared. At least the drive gear did not fall off into the oil pan.
Great that you got it running again. I had a 72 F250 with the 390 engine auto trans and that thing was a WORK truck. I pulled a 28 foot travel trailer over Wolf's Creek pass in Colorado with that thing without missing a lick. 11,000 feet up with a two barrel carb. Over 12,000 lbs gross. Wish I still had it as we usually do after selling it.

Dave
 
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So let me address the elephant in the room. Why did the roll pin shear?
 

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A loose timing chain can cause the problem due to slack take up. Also if a piece of grit gets lodged in the oil pump it can cause the roll pin to shear.


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I miss My 78 F250 4x4 lo boy. that I made into a HIGH BOY. Dana 60s front & rear 351m an a granny first gear. Close to 8 inches of lift an a set of 38.5 monsta mudders !! That was my first Baby.
 
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Ah, the good old days! I assume at least the distributor was up front?
Good deal Zebrafive.
BTW, I'd find another auto parts store, after 36 years they have had plenty of time to stock parts.:munch:
 

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Discussion Starter #13
Since you've already done a tune-up, I'd say you're good to go for the next 30 years or so.:thumbup1gif:

Just can't beat a good old truck!
RUST is the biggest issue, plus I don't think I have another 30years left in me.

So let me get this straight. Your 1978 Ford broke down, and you ended up fixing it with a hammer? :thumbup1gif:

I love old trucks. I miss my '78 F-100, and have the itch for a 70's era F-350 extended cab with a 460. They're not very common, but there's one running around town here that looks really nice.
I could not have fixed it with out a couple of hammers!

Funny! While I was reading your thread I was thinking timing chain or distributor drive gear issue. Seen it many times over the years on mid-late '70's Fords. Good to get to the root of the problem though isn't it?
YES!

So let me address the elephant in the room. Why did the roll pin shear?
Good Question! Maybe there is slack in the timing chain and it "loads and unloads" as the cylinders fire?

I miss My 78 F250 4x4 lo boy. that I made into a HIGH BOY. Dana 60s front & rear 351m an a granny first gear. Close to 8 inches of lift an a set of 38.5 monsta mudders !! That was my first Baby.
Mine has the Dana 60s front and rear IIRCC the front was a $110 option part of snowplow prep. I also have the 4 spd, 400M and 4.10 gears. Plus the biggest GVWR. It came with split rims, tubed tires. I asked why and they said it was the GVWR. I should have ordered one step lower GVWR. As soon as those tires were worn out the split rims GONE.

Ah, the good old days! I assume at least the distributor was up front?
Good deal Zebrafive.
BTW, I'd find another auto parts store, after 36 years they have had plenty of time to stock parts.:munch:
YES, distributor is in the front. You can't even see the distributor on the Suburban, it's back there somewhere.
 
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