1970 FJ40 1F sudden rough idle, stalling, smoke from exhaust

[SlowmoFJ40]

Hello - I've been working on and regularly driving my original 1970 FJ40 for over a year now. The engine starts well without choke, gets good gas mileage (14mpg), has decent power, runs smooth. The engine, carb and fuel pump are all original and have not yet / ever been rebuilt to my knowledge. Valve cover had original F155 sticker on it. Mileage on the engine is unknown. New plugs, wires, cap, rotor, points and condenser have less than 1000 miles on them. Compression is good at about 142 +/- (when I checked it months ago), plugs are a bit oily. BUT yesterday evening after I took it for a drive, the idle was suddenly extremely rough and the engine stalled. After some attempts to restart, I got it going enough to back it in the garage but I had to use full choke to get it going. There was a decent amount of light colored smoke from the exhaust and it was running very rough - had to work the gas peddle and keep it choked to keep it running. Oil and coolant both look clean. I let the engine cool completely and tried restarting - again, it required full choke and produced smoke and was idle was rough....

Unfortunately I'll be traveling most of the next two weeks and won't have a chance to diagnose immediately - anyone have suggestions on the potential cause and cure?

Thanks in advance for your time and suggestions. Much appreciated!

 

[Green Bean]

As a fellow 197 owner, just spit-balling with you here...Perhaps check fuel filter? Fuel cutoff solenoid? How does the fuel level look in the sight bowl? Could be just some debris got sucked into the carb?

 

[SlowmoFJ40]

As a fellow 197 owner, just spit-balling with you here...Perhaps check fuel filter? Fuel cutoff solenoid? How does the fuel level look in the sight bowl? Could be just some debris got sucked into the carb?

I will check the filter and sight bowl - but the filter is only a few months old and I've run many tanks of gas over the past year (most all with cleaner / additives). Maybe some debris from the tank is clogging things up. I'll check the solenoid too. Thanks for the comments.

 

[B y r o n]

Try running some fuel system cleaner through it. Sounds like one or more passages in the carb have plugged up. The fuel system cleaner may dissolve the blockage and prevent a tear down and rebuild.

 

[SlowmoFJ40]

Try running some fuel system cleaner through it. Sounds like one or more passages in the carb have plugged up. The fuel system cleaner may dissolve the blockage and prevent a tear down and rebuild.

I have been adding Seafoam or other cleaners with every fill up - this really improved the idle, need for choke, etc. Everything was running very well until yesterday evening. It would start with a quick turn of the key but this condition started abruptly for the first time ever when I got back to my garage last night.

 

[Living in the Past]

Full choke possible vacuum leak. That will mess up the gas air mixture.

A life time ago I had the hose from the PCV come loose at the bottom of the Carburetor on my 68. As I remember it caused the same symptoms.

 

[charliemeyer007]

Add a bottle of Fuel dryer - warm days/cold nights, water condenses out of the air as the fuel tank breathes. Change the fuel filter - water wet paper doesn't pass fuel well. Leave old filter out in the sun for a few days, after it dries out it will be good again unless clogged with rust and gunk from bad tank.

 

[SlowmoFJ40]

Full choke possible vacuum leak. That will mess up the gas air mixture.

A life time ago I had the hose from the PCV come loose at the bottom of the Carburetor on my 68. As I remember it caused the same symptoms.

I installed a vacuum gauge a few moths ago - its been consistently reading 18-19 at idle but, if something suddenly came loose... I'll definitely look over all of the hoses.

 

[SlowmoFJ40]

Add a bottle of Fuel dryer - warm days/cold nights, water condenses out of the air as the fuel tank breathes. Change the fuel filter - water wet paper doesn't pass fuel well. Leave old filter out in the sun for a few days, after it dries out it will be good again unless clogged with rust and gunk from bad tank.

I'm going to pull the fuel filter and give that a try.

 

[Living in the Past]

I installed a vacuum gauge a few moths ago - its been consistently reading 18-19 at idle but, if something suddenly came loose... I'll definitely look over all of the hoses.

On

If you were having problem before you check the vacuum probably not the problem. Would check the timings and gap on the points in the distributor. Some years a friend on a group run had issues keeping his FJ60 running. He hadn't had that long and issue was a small piece of wood was intermittently getting sucked into the pick up tube in the fuel tank.

 

[SlowmoFJ40]

On

If you were having problem before you check the vacuum probably not the problem. Would check the timings and gap on the points in the distributor. Some years a friend on a group run had issues keeping his FJ60 running. He hadn't had that long and issue was a small piece of wood was intermittently getting sucked into the pick up tube in the fuel tank.

I definitely need to check the fuel line, filter and tank for any obstructions - this 40 was a farm truck for the 15 years prior to my purchasing. I was rough and dirty!

 

[vfrer]

Definitely check the fuel cutoff solenoid. Mine came disconnected one time and acted exactly as you described. Simple thing to eliminate first. Make sure it is getting 12V and that it clicks when 12V is applied.

 

[SlowmoFJ40]

Definitely check the fuel cutoff solenoid. Mine came disconnected one time and acted exactly as you described. Simple thing to eliminate first. Make sure it is getting 12V and that it clicks when 12V is applied.

Sounds like a good place to start - I've got a good list of items to check now. Appreciating all the comments and suggestions from everyone for sure.

 

[SlowmoFJ40]

Full choke possible vacuum leak. That will mess up the gas air mixture.

A life time ago I had the hose from the PCV come loose at the bottom of the Carburetor on my 68. As I remember it caused the same symptoms.

I believe a vacuum leak was the issue - The fuel flow was clear from the tank, no obstructions and I cleared the filter by back flushing fuel through it into a jar but no debris was present. All of the vacuum hoses were in good shape and tight so I kept checking - I put a wrench on the carburetor bolts. the lower mounting bolts were tight but the two upper hex bolts (with a slot across their head) were just a little more than hand tight. After snugging them up, all is well and I'm back in normal running condition. Thanks for the comments and suggestions!