We have a 1971 FJ40 completely stock (three on the tree) that we're trying to bring back to life. It was running great for about 150 miles this last week, but all of a sudden, its now bogging down and bucking in 2nd and 3rd gear at higher rpms with backfires out the tailpipe. The fuel lines have been cleared and the fuel filter replaced. Fuel level appeared good in the carb window, and the carb solenoid does click. We tried running it without a gas cap and that didnt help. The engine runs flawlessly when revving it up with the clutch pressed or while in neutral, so I assume its not fuel starvation. I don't think its a vacuum leak (at least not anywhere you can check with starting fluid) The points and rotor looked fine on the distributor, but there was some play in the rotor. How much is normal here? If its not the distributor rotor, then do these symptoms match anything else? Could this be a failure of the vacuum retard? What about the coil? Any other ideas?
71 FJ40 bogging down only in 2nd and 3rd gear (3 Viewers)
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Sounds like the ignition points are burnt or not gapped correctly.
Crap/water in the gas tank can plug a filter quickly - put a new on (set the old one in sun for a few days to dry out and it will be good again. New fuel could/will help. I have been running Chevron Premium to help clean out my system.
My delco dizzy developed a lot of play in the top shaft - wiggle side to side/front to back - was at least 1/8 of an inch. I got a chinesium one from Amoron for $115. Changed it to my old drive gear, installed the split bushing adapter and the skinny oring. Got timing set today, has oil pressure. Was a PIA, glad its done for now.
Plan on doing the Rochester soon - have a new ultrasonic cleaner and carb juice for it. I had the leather accelerator pump stick to the wall back in about 2003. I freed it and lube the cup with neatsfoot oil, other than that I have never really touched the carb.
Oil seal. I would use the fill cylinder with rope threw the spark plug hole at BDC, then pull on fan blade to lightly compress the rope to hold the valves up. The use the special valve spring compressor to R/R the seal. Back crank off, remove the rope and move to next cylinder in line.
My delco dizzy developed a lot of play in the top shaft - wiggle side to side/front to back - was at least 1/8 of an inch. I got a chinesium one from Amoron for $115. Changed it to my old drive gear, installed the split bushing adapter and the skinny oring. Got timing set today, has oil pressure. Was a PIA, glad its done for now.
Plan on doing the Rochester soon - have a new ultrasonic cleaner and carb juice for it. I had the leather accelerator pump stick to the wall back in about 2003. I freed it and lube the cup with neatsfoot oil, other than that I have never really touched the carb.
Oil seal. I would use the fill cylinder with rope threw the spark plug hole at BDC, then pull on fan blade to lightly compress the rope to hold the valves up. The use the special valve spring compressor to R/R the seal. Back crank off, remove the rope and move to next cylinder in line.
Hmmm, well, a number of things. Maybe your timing is too advanced and it's pinging the motor on such hard acceleration.
Also, if you want to see if the vac-retard is causing issue, you can cap off the vacuum port at the distributor and drive around like that. I use to use a cut piece of vaccum hose with a metal bb from a bb gun pushed into the tube and stuck it onto the port of the distributor. Don't forget to cap off the other end, I think it goes to the carb.
Another thing, and probably really uncommon, but doesn't hurt to check. Look at your exhaust pipe from the manifold down all the way to the tail pipe. Check to see if it's crushed or bent at any point that would restrict its airflow/exhaust. I also had popping/backfire noise and bogged down acceleration at some point. I could accelerate fine as long as it was a gradual increase in rpm. If I stepped on the gas and opened up the secondaries, the popping/sluggish/backfire would happen and I couldn't go any faster. Turns out, my exhaust pipe was bent in on itself. I don't know how it happend, but it did. Had to cut off the bad section and repair it with a piece of exhaust pipe from the auto parts store. It runs great again.
Ask as many questions and provide insight to your findings. I have a 1971 and have done a lot of troubleshooting on it.
Also, if you want to see if the vac-retard is causing issue, you can cap off the vacuum port at the distributor and drive around like that. I use to use a cut piece of vaccum hose with a metal bb from a bb gun pushed into the tube and stuck it onto the port of the distributor. Don't forget to cap off the other end, I think it goes to the carb.
Another thing, and probably really uncommon, but doesn't hurt to check. Look at your exhaust pipe from the manifold down all the way to the tail pipe. Check to see if it's crushed or bent at any point that would restrict its airflow/exhaust. I also had popping/backfire noise and bogged down acceleration at some point. I could accelerate fine as long as it was a gradual increase in rpm. If I stepped on the gas and opened up the secondaries, the popping/sluggish/backfire would happen and I couldn't go any faster. Turns out, my exhaust pipe was bent in on itself. I don't know how it happend, but it did. Had to cut off the bad section and repair it with a piece of exhaust pipe from the auto parts store. It runs great again.
Ask as many questions and provide insight to your findings. I have a 1971 and have done a lot of troubleshooting on it.
RodrigzCrzr
SILVER Star
Check your PCV valve, hose and connection.
Check for any vacuum leaks.
Check for any vacuum leaks.
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Original tank from ‘71?
Try running a hose from a gas can to your fuel pump, drive it and see what happens.
Try running a hose from a gas can to your fuel pump, drive it and see what happens.
Vacuum advance hose fallen off?
Following... as many of you are also helping me in another thread with my trouble shooting! Though my symptoms are slightly different, still very much the same!
Based on my research in this time of confusion with my 72, based on a vacuum questions I had, someone explained the evap emissions control system to me. Not sure if yours is the same or if its even still attached to the vacuum switch on the drivers side front wheel well, but because you say, while parked, you can accelerate the rpms smoothly, that fits the description of how it works... it adjusts vacuum based on ground speed. Once up to a certain speed, it closes off the vacuum retard and the line to the charcoal canister (if I understood correctly). So maybe your timing is set to the vacuum retard and when it advances while moving, you end up to far advanced. Have you disconnected the dizzy vacuum when adjusting timing? I have plugged my vacuum Retard and adjusted timing with no change to my issue, but maybe that could help you.
Based on my research in this time of confusion with my 72, based on a vacuum questions I had, someone explained the evap emissions control system to me. Not sure if yours is the same or if its even still attached to the vacuum switch on the drivers side front wheel well, but because you say, while parked, you can accelerate the rpms smoothly, that fits the description of how it works... it adjusts vacuum based on ground speed. Once up to a certain speed, it closes off the vacuum retard and the line to the charcoal canister (if I understood correctly). So maybe your timing is set to the vacuum retard and when it advances while moving, you end up to far advanced. Have you disconnected the dizzy vacuum when adjusting timing? I have plugged my vacuum Retard and adjusted timing with no change to my issue, but maybe that could help you.
I had an after school job at Midas muffler. They had a little black Datsun pickup truck parts runner with a 4 speed. It was so strange, it ran like a it stole something except in third gear. It had a miss and ran like crap, only in third gear.
