What are your solutions for vapor lock?

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FineWynsFJ40

FineWynsFJ40

Too much to do...
Joined
Jan 13, 2005
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1,378
Location
Grand Haven, MI
From my research and experience, it seems that the cheap gasoline that is being sold at the pump contributes even more heavily toward vapor lock (due to the ethanol added). I never had this problem before, until about a year ago. When it warms up it takes forever to start, and the cranking is different than normal cranking. Seems that people find the fuel vaporizing between the mechanical fuel pump and the tank, which would cause the need for excessive cranking.

I do not have the return fuel line or any of the bracketry for it, as well as emissions - thanks to the previous owner. I have the original factory setup as far as intake, carburetor, etc.

What are your solutions for this? It's been driving me crazy. I see one solution is an electric fuel pump in/near the tank, what are some others?

Thanks,
Brian
 
Never had one, those were 1976 and later, I believe.
 
Are you sure it is a vapor lock problem? There are probably a few possible reasons for hard hot starts...
Maybe put a bag of ice on your fuelpump or carb next time it happens, see if that helps fix it.
 
Brian, you may have gotten the electric fuel pump idea from me. I'm not a mechanic so I don't know if there are a zillion things that can cause a vapor lock, or remedy a vapor lock, but here is my schooling on the subject: My motor home vapor locked on a hot day/long trip. The mechanic/dealer told me that vapor locks always occur between tank and fuel pump. The lesser the distance between tank and fuel pump, the lesser chance of vapor locking. Since electric pumps are pushers instead of suckers, the right place to put them is at the tank anyway---make sense???:meh:
 
With a stock carb isn't there a site glass? Is the fuel half way up the site glass? If the fuel is still in the carb is should start and then die after that if there is a vapor lock in the fuel line. Hard starting makes my think the carb bowl is dry. This was the reason for the cooling fan. The early cruisers had this problem covered. There is a hand primer on the pump which lets you prime the whole system before starting.

While all pumps push the reason closer to the tank is better. Less suction line (before the pump) means less area to be vapor locked. The discharge side of the pump will force fuel all the way to the carb as long as the pump is primed and has a fuel supply.
 
When I developed vapor lock one hot summer it turned out to be the fuel pump itself. Check all the screws on the pump body - make sure they're tight.

I think it's just as likely to get your fuel boiling/vaporizing between the pump and carb where the line runs next to the block/head.
 
The chances of having real vapor lock in a truck like an FJ40, where the fuel pump inlet is below the level of the fuel tank outlet are slim to zero. It would especially unlikely in the years where the fuel is constantly being recirculated to the tank via the return line.
 
Pin_Head said:
The chances of having real vapor lock in a truck like an FJ40, where the fuel pump inlet is below the level of the fuel tank outlet are slim to zero. It would especially unlikely in the years where the fuel is constantly being recirculated to the tank via the return line.
Click to expand...

I don't have the return fuel line or brackets, thanks to the previous owner. Would going through the trouble of reinstalling it help ward this off? Who would have the return line brackets? Thanks.
 
With the design of the FJ40 fuel line infront of the pump it very unlikely your having a vapor lock there. Besides being low it is away from any engine heat until after the pump.

The fact your say starts hard but does start sounds more like the fuel is no longer in the carb bowl. If there was fuel in the carb it will start and die after that fuel is gone if it is vapor locked in the fuel line somewhere. The fuel pump's only purpose in the operation of the carb is to feed the bowl. It doesn't have feed the fuel under pressure to the carb. Just keep fuel in the bpwl. Install a tank above the carb and gravity will work.
 
Even without the fuel return line, the chances of vapor lock are slim to none. I doubt it is your problem.

Hot restarts are often a problem because the engine is flooded, not because there isn't enough fuel. The restart procedure is the same as on any flooded engine:
Hold the pedal to the metal and do not pump it. This opens the throttle wide open.
Hit the key to crank the engine and when it starts let up on the pedal.
Try it.
 
I pull off the air cleaner lid when the carb bowl is boiled dry on hot days and then cup my hand over the carb and crank it over until it sucks the bowl full of fuel and runs. A Turkey baster with some fuel in it helps also, but the hand over the carb trick works quickly and effectively when you need it.
 
One of the reasons behind the return fuel path is cooling. This keeps the fuel moving so it typically is cooler which helps the engine run more efficent. Also reduces the chances of vapor lock. I know that semi-truckers will pull in for a top off just to cool down their fuel tanks in summer.
 
I'm curious abou tteh cranking, you said the cranking is different, what di dyou mean by that? is it slower or faster or labored or how is it different? vapor lock shouldnt change the cranking. I agree with Pin_head about the flooding. Do you have excessive fuel smell too? One thing that works in addition to the pedal to metal method is to put teh pedal all the way to the floor and crank, if no success at that point , then very slowly let it up when the engine fires it is at the right mixture to air ratio, stop letting up on the pedal righr there and it will run if flooding is your problem.

it is possible that your cranking sounds different as it starts to fire and your cranking speeds up a little as your engine is starting to fire and the load on the starter lessens. Im not sure if that is what you were referring to as "its cranksing is differnt than normal cranking" .

just my 2 cents worth.
 
Pin_Head said:
Even without the fuel return line, the chances of vapor lock are slim to none. I doubt it is your problem.

Hot restarts are often a problem because the engine is flooded, not because there isn't enough fuel. The restart procedure is the same as on any flooded engine:
Hold the pedal to the metal and do not pump it. This opens the throttle wide open.
Hit the key to crank the engine and when it starts let up on the pedal.
Try it.
Click to expand...

X2 on this. really haven't had to deal with flooded carb since I went back to stock one barrel carb. The only thing I would had is I hold the pedal down for a minute before trying to start. This lets the fuel sitting in the intake manifold dissipate.

I guess I misundertood I thought the problem was when the weather warmed up. (it's now in the 100s here in AZ) not after the engine was warmed up.:whoops:
 
I have had several different motors/carbs/fuel pumps on my 40, and have never had a vapor lock. Maybe a bad fuel pump, or maybe too far advanced, but never vapor lock, as on my old 50's era chevys and fords
 
FJforty said:
One of the reasons behind the return fuel path is cooling. This keeps the fuel moving so it typically is cooler which helps the engine run more efficent. Also reduces the chances of vapor lock. I know that semi-truckers will pull in for a top off just to cool down their fuel tanks in summer.
Click to expand...

sorry if this is obvious.. but does heat make vapor lock? I guess at some temp, all liquids will go to gas phase, right? My rig has an aux tank at the very back. The fuel line runs at one point in a narrow space between the muffler and the tub. Someone looked at it and said that might get too hot and cause a vapor lock, and maybe even melt the line. In fact, there was a small gas leak at a bend near this heat source. I did a cheapo fix and temporarily wrapped the line with this metallic heat shield tape.

What about those steel or braided fuel lines? Are they more likely to vapor lock? Sorry, more questions.. no answers or suggestions from me. :hhmm:
 
"In fact, there was a small gas leak at a bend near this heat source. I did a cheapo fix and temporarily wrapped the line with this metallic heat shield tape."

You might be contributing to the problem if there's even the tiniest hole for air to get into the line at this point.
 
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