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-   -   40 Series Vapor Lock (http://www.risingsun4x4club.org/forum2/showthread.php?t=13781)

ttubb 08-16-2010 10:31 AM

40 Series Vapor Lock
5 Attachment(s)
On the Triple Bypass run this weekend, Bob (40Zen) was having vapor lock issues. I mentioned to him that my 78 FJ-40 had been converted to a 60 Series fuel pump and the recirc line went from the fuel pump back to the tank, versus from the carb back to the fuel pump. Below are photos first of Bob's stock fuel system (two lines to the carb - supply/return) then my 60 series set-up (single fuel line to carb - supply only). I have NEVER had a vaporlock with this rig (I live at 10,000 feet and wheel uphill from here).
First two are Bob's stock rig, second three are my set-up. I think there is a spacer needed between the pump and the block on the 60 set-up.
Hope this helps someone. Terry

Air Randy 08-16-2010 11:32 AM

I have a stock FJ40 setup on my 74 using the pressure/return lines from the carb and a stock mechanical fuel pump. I've never had a vapor lock issue either and we wheeled at or above 11K to 12K feet on the 40's only run when a number of other rigs did have issues.

I do have an HEI distributor, I ditched the stock exhaust manifold and installed a header, and I have a liquid heat riser installed on the bottom of my intake manifold.

I believe the liquid heat riser makes the biggest difference. Yes, it helps the rig run better in the winter by warming the base of the intake manifold, but it also keeps the manifold base cooler by ensuring it never gets any warmer than the engine water temp of around 180 degrees.

I guess it's possible that running that different fuel setup helps by increasing the fuel pressure inside the carb to help prevent the fuel vaporizing as easily.

nattybumppo 08-16-2010 11:40 AM

I have the stock set-up in my 1977 40, emissions gear and everything, and have had no vaporlock issues this summer either. Knock on wood. My 60 on the other hand...

SteveH 08-16-2010 12:45 PM

Gasohol (now unavoidable) has always caused vapor lock in my stock 1978 '40. My current 'final solution' is a Carter motor type (not vibrator) electric fuel pump mounted ahead of the factory pump, and about 6" lower. It has worked well. My '76 FJ55 was so bad with vapor locking that it left me stranded - first time any 'cruiser did that. I installed a Carter pump at the tank and eliminated the OEM pump - completely fixed it. FJ60-style systems have proven less troublesome across the board than the earlier stuff, for me.

I am no fan of electric fuel pumps (especially Holley junk), but I can't have a vehicle that threatens to kill me by stalling 45 seconds after starting the engine from a hot/parked condition. And yes, I have replaced all the OEM pumps with OEM pumps time and again to no avail. Cursed? Perhaps. But, an electric pump, mounted low and as close to the tank as possible, will save the day.

MDH33 08-16-2010 07:36 PM


Originally Posted by SteveH (Post 159033)
Gasohol (now unavoidable) has always caused vapor lock in my stock 1978 '40.

That's my current theory. I vapor locked on the 40's Run when I cheaped out and put ethanol 85 octane in. When I've run 90+, no problems. Maybe I should look for some Aviation fuel for high elevation runs. :hill:

subzali 08-16-2010 07:55 PM

FWIW, I've never had any vapor locking problems in the 5+ years I've had my FJ40. I always run 85 octane. I have done everything from run over Pearl Pass, Argentine Pass (13+,000 ft), Mosquito Pass (13+,000 ft), Red Cone, Radical Hill, Red Elephant Hill (steep inclines), as well as run around Denver stop-and-go traffic in the middle of summer heat. It's a stock 10/76 Federal spec. (1977 model year) FJ40 (with no cooling fan), with some of the smog components removed (basically only the air rail and smog pump), and my carburetor is a 9/77-12/78 Federal spec. carb, and my jet settings look stock for '78 from what I have researched.

I'm just saying that it seems reasonable to me that the stock setup shouldn't have vapor locking issues, but if you've tried everything else in the book then maybe you need to look into other options to fix it.

Okay, there's my two cents. I'll get off my high horse now.

MDH33 08-16-2010 11:38 PM

Mine isn't stock: '77 2F, '69 carb, header, non-usa vacuum advance distributor, no smog gear. So maybe that has something to do with it. not really sure, but it has only happened a couple of times and I always get home eventually. :hill:

PabloCruise 08-17-2010 07:32 AM

When I lived down in New Mexico I would get occasional vapor lock. A mechanic said that an old trucker trick is to put a quart of ATF in with a tank and that would help with the vapor lock.

I tried it, it worked.

FJ40zen 08-17-2010 10:55 PM


Originally Posted by PabloCruise (Post 159123)
When I lived down in New Mexico I would get occasional vapor lock. A mechanic said that an old trucker trick is to put a quart of ATF in with a tank and that would help with the vapor lock.

I tried it, it worked.

Cough, Cough! Bet that smelled a little also. ;)

Thanks for the many ideas. I have a NOS pump on there from a few months after I got the cruiser. That didn't work. I am going to try Terry's suggestion first, since the higher octane does not really work in my situation. I have tried that several times before and it makes a little difference, not not enough. I really don't see why I need a return line at all. I definitely know that fuel delivery to the carb is at best - weak, but only when hot. I never have the problem in cooler months.

cbmontgo 06-29-2011 02:28 PM

I am reviving an old thread here...

I have a '76 FJ40 with a 100% stock setup. I rebuilt the carb last winter and put a brand new OEM fuel pump in last summer.

She runs great, but I was up in Pike National Forest last week and stopped with the kids for about 15 minutes and she vapor locked for about 30 minutes before cooling enough to restart.

I am thinking that the electric fuel pump may be a good idea from what others have told me. Any particular make/model/flow rate/head pressure that you'd recommend?

Also, does higher octane fuel REALLY help?

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