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

86 F-150 strange issues

 
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Old 02-08-2019, 04:56 AM
cdubb79w
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86 F-150 strange issues

Long post incoming,

I have a 1986 F150 with the I6 engine and the 1bbl carb that has some odd issues. When I got the truck it has been sitting for 23 years (21,000 actual Miles!) I got running but it ran very rough, almost like a miss or a "cough" and was very rich, it smoked like a diesel. I changed the fuel filter and it ran perfect, but I ran it out of fuel and (I assume) sucked up some junk at the bottom of the tank and it ran horrible again. Ended up rebuilding the carb and it runs perfect again...however we noticed if the truck rocked or bounced it would sputter/cough and sometimes stall and when this would happen it would flood and not restart. Now bear in mind this is sitting and idling, the shocks are totally shot so something like hoping into the cab or closing a door is enough to make it spaz out. Initially I figured I screwed something up on the carb but it runs sooo good (at all rpms) when it doesn't have any sudden movements I have a hard time believing I messed up.

What the hell is going on with it?

I tried tracing leaks by spraying carb clean around the intake, vac lines and carb and found nothing. Tried running it off a remote tank and changed the fuel filter (thinking it might have been junk breaking loose) and that didn't work. Am I missing something? I haven't checked fuel pressure but on a mechanical pump don't they either work or don't work, right??

any ideas would be great
 
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Old 02-08-2019, 06:00 AM
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All you need is a little speck of dirt to go into the carb and it will hold the float needle open and make it flood out. I have had vehicles with constant problems like this, and the only solution was to put a new fuel tank in place. They are cheap enough. You can take the fuel filter off and dump it out on a white rag or paper towel, and see how bad it is. It should be new if you just rebuilt the carb. If it's filthy, it's time for a tank.
 
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Old 02-08-2019, 07:02 AM
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Out of all the places I've checked, https://www.rockauto.com/ has the best prices on fuel tanks.
 
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Old 02-08-2019, 07:09 AM
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Don't over look metal fuel lines as they too can rust from the inside causing problems.
I hope you drained both tanks of old fuel before starting.
Dave - - - -
 
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Old 02-08-2019, 09:17 AM
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why don't you put a clear plastic inline fuel filter for a short while so you can see how much rust is in your system?
 
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Old 02-08-2019, 09:18 AM
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Originally Posted by cdubb79w View Post
Tried running it off a remote tank and changed the fuel filter (thinking it might have been junk breaking loose) and that didn't work.


I want to make sure I understand this statement correctly. When you said trying a remote tank "didn't work", do you mean it "didn't help"? Or do you mean the engine still misbehaved with a new filter and remote tank?

I'm assuming (Danger! Danger!) you meant it didn't help, but want to be sure. If so, I don't think your tank or lines (between tank and pump) are at fault. Even if jostling the truck stirred up some crud in the tank and blocked the fuel flow, but the pump was still good, the engine should still run for half a minute or so using the fuel still sitting in the carb bowl. Now if the carb float level was out of whack, or the carb bowl was already low due to some other defect (such as a weak/damaged pump, clogged line, etc), then all bets are off.




Originally Posted by cdubb79w View Post
I haven't checked fuel pressure but on a mechanical pump don't they either work or don't work, right??
Au contraire. A pump can partially fail. This happened on my truck, and I couldn't get above 40mph. I limped home about 50 miles like that. I changed the fuel pump and all was good again. I also replaced the fuel filter, but cut the old one open and found zilch.

Before diving in too deeply, I'd highly suggest checking the pressure and volume from your existing pump. Rule out the easy stuff first.
 
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Old 02-08-2019, 01:54 PM
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Lots of replies thanks!

Originally Posted by Franklin2 View Post
All you need is a little speck of dirt to go into the carb and it will hold the float needle open and make it flood out. I have had vehicles with constant problems like this, and the only solution was to put a new fuel tank in place. They are cheap enough. You can take the fuel filter off and dump it out on a white rag or paper towel, and see how bad it is. It should be new if you just rebuilt the carb. If it's filthy, it's time for a tank.
Now to be clear there is only one fuel filter stock on this truck and that's the one that threads into the carb right? I made up a section of rubber fuel line to go from the pump to the carb and put a clear inline filter inbetween and there isn't really any gunk to speak of.

Originally Posted by Odisvan View Post
why don't you put a clear plastic inline fuel filter for a short while so you can see how much rust is in your system?
See above, it didn't catch much to speak of

Originally Posted by kr98664 View Post
I want to make sure I understand this statement correctly. When you said trying a remote tank "didn't work", do you mean it "didn't help"? Or do you mean the engine still misbehaved with a new filter and remote tank?

I'm assuming (Danger! Danger!) you meant it didn't help, but want to be sure. If so, I don't think your tank or lines (between tank and pump) are at fault. Even if jostling the truck stirred up some crud in the tank and blocked the fuel flow, but the pump was still good, the engine should still run for half a minute or so using the fuel still sitting in the carb bowl. Now if the carb float level was out of whack, or the carb bowl was already low due to some other defect (such as a weak/damaged pump, clogged line, etc), then all bets are off.






Au contraire. A pump can partially fail. This happened on my truck, and I couldn't get above 40mph. I limped home about 50 miles like that. I changed the fuel pump and all was good again. I also replaced the fuel filter, but cut the old one open and found zilch.

Before diving in too deeply, I'd highly suggest checking the pressure and volume from your existing pump. Rule out the easy stuff first.
You're correct in you assumption, a remote tank did not change how it ran when jostled around. The float was one thing I wondered about as well, I've had floats in the past flood with fuel and sink and cause it to run poorly but I check when I had it apart, it still floats and no gas is getting inside. Now just to verify, how do you adjust the float on these old Carters? And what should my fuel pressure read when I test it? I assume there's only the one pump on the engine or is there also a electric lift pump on/in the tank?
 
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Old 02-08-2019, 02:12 PM
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I have had a little chunk of rubber clog the valve in the carb and that came from me installing new lines. Or your float level is set too high in the carb. Can't think of anything else that would make it run bad by shaking the truck.
 
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Old 02-08-2019, 10:02 PM
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Not really an update but further questions.

I asked earlier about how to adjust the float on a carter, I did some research and it seems like you can't adjust it while it's on the engine (like a Holly), it has to be split in two and adjusted before assembly. Is this correct? Also I assume this would be based off the Carter YF family of carbs but it looks like that family stopped being used in 85, what would be this carb and what are the differences? I see I can buy one for an 85 for $80, kind of tempting if this problems persist, if they can be swapped.

Also on the note of fuel pressure, I assume it should be in the 5-8 PSI range coming off the pump?
 
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Old 02-09-2019, 12:27 AM
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Shot in the dark, not knowing your setup, I'd guess you have a feedback carb, YF or YFA, still haven't figured out the differences between the two and most people use them interchangeably, or just call them all YF's. Most rebuild kits have all the parts for both styles. Pictures go a long way. If I remember half of what I've read about them, there should be four screws on top to split the carb. Cant remember exact pressure numbers, but that range sounds good. Just gave a friend the inline pump off my donor truck for the motor he got, claimed similar numbers, said it was good for all domestic 4, 6, and 8 cylinder carbureted applications.
 
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Old 02-09-2019, 04:57 AM
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Originally Posted by cdubb79w View Post
Not really an update but further questions.

I asked earlier about how to adjust the float on a carter, I did some research and it seems like you can't adjust it while it's on the engine (like a Holly), it has to be split in two and adjusted before assembly. Is this correct? Also I assume this would be based off the Carter YF family of carbs but it looks like that family stopped being used in 85, what would be this carb and what are the differences? I see I can buy one for an 85 for $80, kind of tempting if this problems persist, if they can be swapped.

Also on the note of fuel pressure, I assume it should be in the 5-8 PSI range coming off the pump?
Yes you have to pull it apart to adjust the float. When you rebuilt it that would have been one of the last things done before the 2 halves went together.
You may want to pull it apart again to make sure it is right.

Yes again Carter YF family of carbs. Now for our trucks they come in 2 styles non-feed back used up to about 82 and feed back 83 on till EFI.
The feed back system has a bunch of wires going to the carb and the dist. does not have a vacuum advance hose going to it or a can to hook hose to just a square box and a bunch of wires to it.
This is all adjusted, carb & timing, by a rude computer and everything has to work right for the motor to run right. Codes can be pulled from the computer using a test light.
Non feed back may have 1 or 2 wires going to it (choke & maybe fast idle solenoid if it has AC) and that's about it. The dist. will have a vacuum hose and a can to hook hose to and maybe 3 wires.

Now this feed back system as said everything has to work right for the motor to run right. 1 sensor bad or a vacuum leak can throw the system into fits and make it run bad.
After reading codes on a feed system are pulled and you know somewhat what is wrong you get the fun job of trying to find parts for it.
That is why if you don't need this system to pass smog people swap out the feed back system to a non feed back system. You would need a non feed back carb & dist. and wiring harness. The harness is the hardest part to cam by but can be gotten used, new $$ and guess made.

BTW you should have a feed back system and if it is not right could be why it does not run good?
Dave ----
 
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Old 02-09-2019, 06:09 PM
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Originally Posted by Kramercd View Post
Shot in the dark, not knowing your setup, I'd guess you have a feedback carb, YF or YFA, still haven't figured out the differences between the two and most people use them interchangeably, or just call them all YF's. Most rebuild kits have all the parts for both styles. Pictures go a long way. If I remember half of what I've read about them, there should be four screws on top to split the carb. Cant remember exact pressure numbers, but that range sounds good. Just gave a friend the inline pump off my donor truck for the motor he got, claimed similar numbers, said it was good for all domestic 4, 6, and 8 cylinder carbureted applications.
Was the inline pump stock on this era of truck? If so where is it located? I haven't noticed a inline when I've been underneath it.

Originally Posted by FuzzFace2 View Post
Yes you have to pull it apart to adjust the float. When you rebuilt it that would have been one of the last things done before the 2 halves went together.
You may want to pull it apart again to make sure it is right.

Yes again Carter YF family of carbs. Now for our trucks they come in 2 styles non-feed back used up to about 82 and feed back 83 on till EFI.
The feed back system has a bunch of wires going to the carb and the dist. does not have a vacuum advance hose going to it or a can to hook hose to just a square box and a bunch of wires to it.
This is all adjusted, carb & timing, by a rude computer and everything has to work right for the motor to run right. Codes can be pulled from the computer using a test light.
Non feed back may have 1 or 2 wires going to it (choke & maybe fast idle solenoid if it has AC) and that's about it. The dist. will have a vacuum hose and a can to hook hose to and maybe 3 wires.

Now this feed back system as said everything has to work right for the motor to run right. 1 sensor bad or a vacuum leak can throw the system into fits and make it run bad.
After reading codes on a feed system are pulled and you know somewhat what is wrong you get the fun job of trying to find parts for it.
That is why if you don't need this system to pass smog people swap out the feed back system to a non feed back system. You would need a non feed back carb & dist. and wiring harness. The harness is the hardest part to cam by but can be gotten used, new $$ and guess made.

BTW you should have a feed back system and if it is not right could be why it does not run good?
Dave ----
Ughh, that's what I was afraid of, a friend who knows a little about it said something similar to what you have above, basically mine is a PITA compared to one from a few years earlier
 
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Old 02-09-2019, 06:56 PM
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If the truck does not need to go thru a smog check and you have to replace the carb for some reason I would get an earlier non-feed back and then all you need is the non-feed back dist. and harness.
Then you don't have to deal with that system ever again.
There is a lot of posts in here on this DSII swap do a search.
Dave ----
 
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Old 02-09-2019, 07:24 PM
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Don't know. I assume inline pump isn't stock. But if you do have one it should be inside left rail on the frame.
 
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Old 02-09-2019, 08:25 PM
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Originally Posted by Kramercd View Post
Don't know. I assume inline pump isn't stock. But if you do have one it should be inside left rail on the frame.
I don't think the truck used electric pumps unless they were EFI and the 300 did not g0o EFI till after 87 sometime, so he should only have the pump on the side of the motor.
Dave ----
 

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