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FJ40 Vapor Lock Mystery

Discussion in '40- & 55-Series Tech' started by Bob D, Mar 21, 2004.

  1. Bob D

    Bob D

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    Can anyone help solve this mystery? I have a 1977 FJ40, new to me last fall. I put in a rebuilt SOR carburetor shortly after getting it because fuel mileage was terrible, back firing on shifting, etc. Fixed that problem just fine, but I started having a problem with the engine stalling if I started it up after it sat with a hot engine for even a short time. Now that the weather is getting warmer, I'm noticing it even more, practically every time I shut down and restart soon after.

    Here's what I've done: suspecting vapor lock, I wrapped the fuel lines over the engine block, replace fuel filter and fuel pump, fussed with the carburetor adjustments per the manual. No success. OK, now here's the mystery clues: I realized that my stalling seems to happen mostly as I make a turn (like out into traffic!!) after startup. If I drive the vehicle until the engine is hot and then shut it down, I see bubbling in the window on the carburetor. If I start it up, it seems to run fine at idle, but if I rock the vehicle back and forth it starts to bog down (but doesn't quite stall) and I see increased bubbling in the carburetor window. I'm beginning to think the carburetor rebuild needs rebuilding. Does this suggest any definite culprit to anyone?
     
  2. spotcruiser

    spotcruiser Geezer SILVER Star

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    I have the same problem with my '78 when the carb cooling fan is not working. In fact, that's how I find out that the fan has quit. With the carb/intake manifold bolted to the exhaust manifold there is a lot of heat transferred to the base of the carb, which will boil fuel out of the carb when you shut the engine down. Is your cooling fan working?
     
  3. Bob D

    Bob D

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    My FJ40 (1977 built in October 1976) doesn't have the fan, even though I understand it should have one. I talked to SOR about it and they indicated it would be mounted on the driver's side front, blowing back to the carb. I have searched all over and I can't find any mount area where it would have been, nor any wiring that would have been used for it. Unless I'm missing something it doesn't look like it ever had one! I guess I'll be installing one soon, though, if that is the only solution.
     
  4. spotcruiser

    spotcruiser Geezer SILVER Star

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    My '76 has one in the front DS corner of the engine compt. I don't think that location is as effective as the later models. My '78 has the fan by the cowl vent, below the clutch master. Don't know whether the '77 should be the early or later style. Is your windshield wiper reservoir below the clutch master (indicates early style fan)?

    Couple of possible solutions:
    1) Install a later-type fan (should be pretty easy to find and install).
    2) Going to headers will reduce the heat transferred to the carb. Personally, I prefer the stock manifold.

    Good Luck.
    Todd Bull.
     
  5. Pin_Head

    Pin_Head

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    Sounds like the fuel is boiling out because the carb is too hot.
    Make sure that the preheat flapper valve in the exhaust manifold isn't stuck closed. Your heat shield and or insulator may also be missing. Check the SOR catalog for the description of these parts.

    Also check that the engine isn't running hot. Retarded ignition timing can elevate the exhaust manifold temps.
     
  6. spotcruiser

    spotcruiser Geezer SILVER Star

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    Thanks Charlie. Those are things I didn't think to mention. Anymore, I keep the exhaust manifold dampers wired open. Next time I have the manifolds off, I will weld them open.

    I did have to replace the insulator between the exhaust and intake manifolds some years ago. I don't actually know if the insulator is available still or not, or whether it is actually necessary. I had to have a crack in the intake manifold welded up at the same time, so perhaps the insulator is important.

    Good Luck Bob.
    Todd.
     
  7. Bob D

    Bob D

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    Thanks for the great suggestions. I checked the manifold flapper and it seems to be working correctly (it rotated after the manifold warmed up). I did find that the hot air flap on the air intake did not seem to be moving, so I removed the unit, took off the sensor and tried heating it up. It didn't move at all, so I've reinstalled it with the flap now open to cool air all the time. Test drive didn't get any stalls, so maybe it was getting overheated from the air intake. I'll repost if this is the fix.

    Still wonder about the stalling on the turn or rocking the vehicle. Something to do with the float, maybe? Thanks for the help!
     
  8. hammerhead

    hammerhead

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    That's cool...hehehe... 8)
     
  9. swank60

    swank60

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    you should get that fan hooked up sooner than later - from what I understand, the heat can crack your intake manifold if it bakes just right. I ran around without the fan for a while too, and got lucky...it's supposed to be pretty common (the cracking intake thing)
     
  10. Bob D

    Bob D

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    So far fixing the hot air flap on the air intake seems to have made the difference, but I'm not convinced yet. More time on a hot road and I'll know better. Still, I think it has to help cool the carb as it should have if the intake were shifting over to fresh after a warm up.

    I swear I can't find any evidence of this vehicle having a fan, though. There are no open sockets on the wiring harnesses either in the engine compartment or on the passenger side firewall behind the blower vent where the relay should be mounted (no relay, either, but there is a bracket there where it could be mounted). There are three holes on the driver's side wheel well , widely spaced. It is possible that these aren't the originals, but I would sure think the wiring harness would have to have some socket there.

    Read the fuel poll, too, and it brought up an ah-ha for me. Here in Southern Arizona the gas has 10% ethanol from October through March. Maybe that just aggravated the boiling, too.

    I'll have to track down an aftermarket fan if the manifold is at risk, as it seems to be. Thanks for the info!
     
  11. DenverCruiser

    DenverCruiser

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    A stock 69' wouldnt have an manifold flap would it?
     
  12. Romer

    Romer fatherofdaughterofromer Moderator

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    Just a comment. My 77 doesn't have a fan. Don't know if it ever did. I have driven a lot of Hiway miles and never had a heat problem. Just mention it because maybe you have another problem.

    Ken
     
  13. IDave

    IDave

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    Yeah, it isn't the lack of a fan. Definitely, the 69 has a heatriser flap. Definitely the heatriser coils fail, and if yours has, you are toasting your carb.
     
  14. Bob D

    Bob D

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    Digging into the supplement in the Haynes manual it says the fan was standard on the 78's on, but it could be that California emissions had them earlier. That would explain the absence in my vehicle. In any case I looked at the wiring schematic and figure I can't just add the fan and relay anyway because it shows a manifold temp sensor in the wiring, and I doubt if I have that if I never had a fan.

    I hear of this being a common thing, but it sure doesn't feel good to stall out pulling into traffic. The air intake fix wasn't the total cure . . . I'm still getting the burp. I'm hoping that it eases when the ethanol season is over here in Arizona. I'm going to have to find an aftermarket fan that will go into available space and mount a toggle on the dash, I guess.
     
  15. Romer

    Romer fatherofdaughterofromer Moderator

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    Since again your 76 didn't come with a fn, i think you will be disappointed with the results if you put one in. There is something else wrong. tell us about last tune up, timing etc. How do you knoe you got the right carb from SOR? Was it adjusted ;properly AFTER installation on your 2F?
     
  16. Bob D

    Bob D

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    Well, I don't know that the carb from SOR is the correct one. It mated up with all the connections perfectly. I installed it with new gaskets and used the existing spacer block between the carb and the intake manifold (made of some non-metallic composite stuff . . . I assume it is a heat spacer). I didn't notice any cracks or damage. I just did a tune, new points. Set timing with strobe to hit the little silver bb just right. I have fussed with the carb adjustment several times trying to match the specs in the Toyota manual. I'm not expert by any stretch but I think I'm pretty close. It seems to start and run fine. The new carb took me from 8-9 mpg to avg 12. It's just this engine stall after a minute or two of running after the vehicle has been sitting shut down with a warm engine (and that's not long hard driving, I'm just talking 10 miles maybe). It almost seems to be flooding in that I can smell fuel when I crank it over and over until it starts again. If I have enough speed up I'll leave it in second and let the momentum try to turn it over again, and it still takes a few seconds before it sputters and cranks. It is sure driving me nuts!
     
  17. DenverCruiser

    DenverCruiser

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    Anybody have a picture of what I should be looking at when looking for the heatriser flap on my 69'? I had the exact same problem all last summer and thought it was the fuel pump or something else but it seems to work great. THANK YOU! I really hope this is the problem as I dont think I can take the vaporlock for another summer.
     
  18. Bob D

    Bob D

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    If I'm correct about this, the heat riser on my 77 is on the exhaust manifold right side (I'm facing the left side of the engine block). It looks like a coil of metal (spring) with a half moon weight beyond the coil. I am assuming that when the weight is oriented flat side vertical the heat goes to the intake manifold surface, and as the engine warms up the weight and flap rotate to horizontal, shutting the flap. I can flip it and hear the thing open and shut inside the manifold.

    I hear ya about the vapor lock for the summer ahead! I sorta dread the startup now for the first few minutes. That'll be me driving around in the parking lot waiting for it to stall so I won't get broadsided as I die pulling out in traffic.