Popping=backfiring?
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Popping=backfiring?
I have a 86 f150, that seems like when I fix one problem, another arrives.
To give some short history, I've rebuilt the engine, transmission, and carb on this thing, and have also bought a rebuilt carb because my carb still didn't work right.
My current problem is this; under load (heavy or not) with the truck in gear (but never in Park or Netural), it will "pop". Out of the carb. Now, it won't go out the back of the tailpipe, which is what It hought happens when it backfires. During this time, the truck tries to die. Especially if its a big hill or something.
Any thoughts? I've replaced things like: spark plugs, wires, o2 sensor (when I did the rebuild). I still haven't gotten this thing totally road-worthy, and its really beginning to annoy me, but I've got to much in it to stop now! Help!
To give some short history, I've rebuilt the engine, transmission, and carb on this thing, and have also bought a rebuilt carb because my carb still didn't work right.
My current problem is this; under load (heavy or not) with the truck in gear (but never in Park or Netural), it will "pop". Out of the carb. Now, it won't go out the back of the tailpipe, which is what It hought happens when it backfires. During this time, the truck tries to die. Especially if its a big hill or something.
Any thoughts? I've replaced things like: spark plugs, wires, o2 sensor (when I did the rebuild). I still haven't gotten this thing totally road-worthy, and its really beginning to annoy me, but I've got to much in it to stop now! Help!
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If your sure about the timing, i can think of a couple of other things that could cause the popping and/or backfiring including: 1) the mixture screws being off, 2) clogged fuel lines or pick up tube,3) a wore out fuel pump, 4) a stretched timing chain or damaged timing gear..
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Originally Posted by oldhawkins
If your sure about the timing, i can think of a couple of other things that could cause the popping and/or backfiring including: 1) the mixture screws being off, 2) clogged fuel lines or pick up tube,3) a wore out fuel pump, 4) a stretched timing chain or damaged timing gear..
2. Brand new lines, and pick-up tube. The tank was dropped and cleaned.
3. Brand new.
4. Brand new timing gear.
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Haynes makes a manual for these trucks Marty, they have a great section in them on how to tune carbs..chances are your carb just needs to be tuned. One easy way that i used to adjust my mixture screws was to turn them in all the way.(truck should not start if turned in all the way) Then turn them out(equally) until the truck would start.Once the truck would start,then turn another full turn. Now, to get it exact,u will need to use a volt meter and follow the specs in the manual for the correct rpm at idle. Some of us "old guys" can get pretty close by "listening" to the engine, and another way is by driving it down a back road and "listening to the feel" and adjusting the mixture until the engine is right....again the later ways are for guys who know what they are hearing....
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I have two Chilton manuals...I don't remember that being in there, but I'll try to see if it has. If not, I'm on the hunt for a Haynes manual.
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I spoke with my teacher at school (I am currently attending a school for automotive), and he doesn't agree with the mixture. He thinks (he has driven the truck) that its more likely the pump, or the sending unit not send enough fuel to the carb. Especially since the fuel filter was plenty dirty. I'm going to try and see if what he suggested works, and get back to yall.
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From: Virginia
Your teacher is correct, if you have a dirty fuel system. Little bits of rust and dirt can create havoc with the carb. If you find it is really dirty, your best move is to get a new fuel tank. The tanks on these trucks are famous for rusting through where they lay against the crossmember on top of the tank. If you search through the posts for the last couple of weeks, we had a guy on here with the same problem, and his truck ran like a new one after we convinced him to pull the tank and get another.
Then after you clean the fuel system up, I would take the top of the carb off and clean it and the main jets out, and then it should run a long time with no trouble.
Then after you clean the fuel system up, I would take the top of the carb off and clean it and the main jets out, and then it should run a long time with no trouble.
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Marty, if u go back and read my posts, my second and third solutions to your problem are exactly as your teacher mentioned and yet your reply was that u have brand new lines,pick up tube,tank was dropped and cleaned and u have a new fuel pump......was the fuel filter dirty before u did all this or after??
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ahh......ok we are getting somewhere, check the fuel filter again, and does the pick up tube in the tank have a "sock filter" on it or no? I have had these same problems with a suburban i once had. Was the inside of the tank rusty? also the inside of metal filler tubes can harbor rust as well ...if the tank has a visual scale of rust inside and it has broke loose it will cause all sorts of havoc...definately replace the tank. Blow compressed air thru all the lines to make sure they are clear as well. Also fuel pumps can pull some of this gunk into them and damage the bellow and /or not allow it to pump right, so a new fuel pump may be in order along with the tank.
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Alrighty. I've been out of town, plus holiday's.
I dropped the tank, and replaced it. The sock filter was a little dirty, so I cleaned it, and it looks like new. I used my air compressor and sprayed out all the fuel lines thoroughly. I also checked the fuel filter again, and it is clean.
But, we are still poping. I tried messing with maybe its the timing, and I think it could still be timing related? But why does it do it MORE when its at 10 BTDC, where its supposed to be, versus 14 BTDC? Or is that my imagination? I am so frustrated at this point. I can't even think anymore!
I dropped the tank, and replaced it. The sock filter was a little dirty, so I cleaned it, and it looks like new. I used my air compressor and sprayed out all the fuel lines thoroughly. I also checked the fuel filter again, and it is clean.
But, we are still poping. I tried messing with maybe its the timing, and I think it could still be timing related? But why does it do it MORE when its at 10 BTDC, where its supposed to be, versus 14 BTDC? Or is that my imagination? I am so frustrated at this point. I can't even think anymore!
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Marty, I know its frustrating, but it is also a learning process.. by the time u figure it out u will have gained valuable knowledge and can help someone else with a similar problem.Hang in there!
Ok...You now have the fuel system clean and replaced ,so u have elimanated that and know its not the issue... We like to be dead on at a diagnosis, but sometimes the process of elimination is the best solution...As far as i can think marty, you only have two things left to rule out,An out of adjustment carb. Or a timing issue..For some reason you may have gotten a bad timing gear set when the engine was rebuilt, or possibly the old one was reused.I had a similar issue on a 71 ford where the nylon timing gear broke.It idled fine but when u gave it rpm it popped and backfired.. the way it acted had me stumped for days until i broke down and pulled the cover off and saw it folded in two on the shaft.
Ok...You now have the fuel system clean and replaced ,so u have elimanated that and know its not the issue... We like to be dead on at a diagnosis, but sometimes the process of elimination is the best solution...As far as i can think marty, you only have two things left to rule out,An out of adjustment carb. Or a timing issue..For some reason you may have gotten a bad timing gear set when the engine was rebuilt, or possibly the old one was reused.I had a similar issue on a 71 ford where the nylon timing gear broke.It idled fine but when u gave it rpm it popped and backfired.. the way it acted had me stumped for days until i broke down and pulled the cover off and saw it folded in two on the shaft.