fuel starvation, summertime edition-SOLVED 4 years later

[lcwizard]

you are correct sir. ive never had an issue with it in the winter.


is ethanol free a temporary solution or is the modern fuel mix still an issue with vaporization regardless of ethanol?

I don't know about the gas but my last stock FJ60 was basically a non driver in the summer unless I kept the trips under 100 miles.
After the fix it never did it again. I'm 80 miles uphill from Phx. at about 3800 ft. we're about 10 degrees cooler here in summer.
If I took a trip to Phx and back I'd almost always need to stop about 18 miles from home where we have a 7 % grade for five miles.
I could baby it on flat, keep it around 55, but once I hit the climb it would do the vapor lock thing and I'd have to take a half hour picnic
with the hood open.
I've done the same to a couple 40s with the same issue

 

[hooter]

I don't know about the gas but my last stock FJ60 was basically a non driver in the summer unless I kept the trips under 100 miles.

I was at 100 miles exactly when this started. coming and going.... The temp of the fuel and the resolution of symptoms with new fuel cooling the mix makes perfect sense. this is the first explanation that makes sense. ill look at electronic fuel pump option

thanks

 

[lcwizard]

I keep this app on my phone and check the route before I take a long haul with my rig: Pure Gas

I think the only pure gas in Az is race fuels like VP. There's a station about 60 miles from here. At more thandouble
the price per gallon I'd try the fuel pump thing first

 

[lcwizard]

I was at 100 miles exactly when this started. coming and going.... The temp of the fuel and the resolution of symptoms with new fuel cooling the mix makes perfect sense. this is the first explanation that makes sense. ill look at electronic fuel pump option

thanks

I used a tbi fuel pump. A couple years later I could use the same pump when I did the fuel injection swap. The GM style swaps use a 14psi system.

 

[GA Architect]

I used a tbi fuel pump. A couple years later I could use the same pump when I did the fuel injection swap. The GM style swaps use a 14psi system.

Does this vapor lock go away with the installation of fuel injection?

 

[SteveH]

Not to sound like the old grumpy guy, but I spent 15 years with 5-6 different electric fuel pumps (of varying costs, pressures, heights relative to tank depth) mounted all over my '78 FJ40, and installed AFI TBI last summer. In my case, the truck would stall and die 45 seconds after you re-started it - which is just the time you'd pull into a busy intersection after gassing up. It also would alternately flood and starve for fuel (and stall) within 60 seconds of each event, while 'wheeling. I had carefully rebuilt the carburetor twice over the years. I had dual gas tanks, which complicated issues, as well.

I just decided that after 29 years of ownership, I either had to make a museum piece out of it or make it driveable, so I installed TBI injection. Now, it starts and runs at 80F just like it does at 20F - very well. The TBI delivers more power (seat-of-the-pants) and works well at 7000' elevation. Slightly worse gas mileage, but I don't care. When I'm going 55 and floor it, it pulls hard up to 70 - never did that before.

 

[lcwizard]

Does this vapor lock go away with the installation of fuel injection?

I installed my first TBI on a 40 in 1990. At some point in time all my Land Cruisers got TBI. I've never experienced vapor lock
with one. All TBIs use the same principle of fuel delivery. The pump feeds far more than you could use. The return keeps the fuel
cycling and cooling. The TBI pumps deliver about 34 gallons per hour. You'll use about six of those at 10 mpgs @ 60 mph.
Most of the fuel is just cycling back , cooling while it does

 

[Solace in Solitude]

@Solace in Solitude may have some good insight to this question.

I don’t know about “good insight”... but, here’s what I did... in the order I did it..,

When it first occurred, it was 108 outside (212 in the truck) and I was climbing a steep hill, going south out of Tonopah, NV. I had my foot to the floor and she suddenly died. As soon as I pulled off the road, I was immediately able to restart her. Vapor lock, in my AZ experience years ago, doesn’t allow immediate restart.

I sleeved the hard line, from the fuel pump to the carb, using this —> Amazon product ASIN B00FS6CKUO
Didn’t hurt...

When it next occurred, I was climbing a steep grade, north out of Vegas, on I-15. Same symptoms... I was able to start her back up, without leaving the freeway... but, she would immediately die each time... I pulled off the freeway and phoned @FJ40Jim.. I described the symptoms and Jim asked if my coil was leaking oil (it wasn’t)... Jim said, it fuel starvation and suggested I repeat the situation and turn the key off immediately after she died. Then “... safely pull off the road and check the carb sight glass, your sight glass will show what it looked like when the engine died... then call again”.

I repeated the issue and report “no gas, in sight glass” to Jim.

Jim said, “Your fuel pump is sucking a lot of air when the secondary kicks in. Check everything, from the tank to the carb, you’re pumping air from somewhere”.

I did as Jim said and found my clear, glass fuel filter (with replaceable element) was not sealing completely. It worked fine, UNTIL the secondary kicked in.

I replaced that filter with a spare and finished my 2-week trip, with no further problems.

Several months later, my oem fuel pump failed, in the middle of nowhere. I removed the battery and tray and replaced the oem pump with a spare and returned home.

When I opened the failed pump, I found a 1/2” slit in the diaphragm... so, I changed my oil and filter. I apparently caught it before it flooded my crankcase with gas.

But, the possibility of contaminating my crankcase, in the middle of nowhere and the pain in the ass, of removing the battery and tray, stayed with me... I found myself worrying about it.

So, I decided to redesign my fuel delivery system and ultimately moved to a pair of electric pumps... one for each tank.

As long as I don’t empty a tank below 1/4, I can always switch back to the other tank, should the active pump fail.

I actually try to keep both above 1/2 full and carry a spare. All three pumps are—> Carter P4070 In-Line Electric Fuel Pump [32UR46AT] - $29.99 : outletits.com. Note: I paid $50+ for each, at the time.

These pumps deliver 4-6 psi, which is what an oem pump delivers. No need for a Regulator.

But, I wouldn’t run an electric pump without an oil pressure safety switch (OPSS). I use this —> Amazon product ASIN B000CSWR10
The OPSS causes the fuel pump to shut off when oil pressure dips below 2 psi. It also allows the fuel pump to run when the starter is engaged.

In the event of a wreck, I don’t need to worry about fuel continuing to pump and, ultimately, frying my boys to a crisp.

Bottom line... if the engine dies under load, and the sight glass is empty and the engine will immediately restart, it’s not likely vapor lock.

The carb sucks a lot of fuel, for the secondary. Even a pinhole, in a fuel line, will suck a lot of air. If the air source is downstream, from the fuel source, the pump will draw more air than fuel.

I love my electric pumps and the feeling of security my fuel system design provides.

But, I don’t attribute the elimination of my fuel delivery problem to my electric pumps... Jim was the key to solving my problem.

Good luck with yours!!

 

[hooter]

^^^THANKS^^^^

 

[77mustard40]

Hooter I’ve been following this and thinking about your issues. I’m up in AUSTIN with the same truck as far as color and production date ( not nearly as nice as yours ), but I’m desmogged. About the only other difference is I’m running an FJ60 big cap dizzy but sounds like your issue is fuel.

It gets hot here too but I’ve never had a vapor lock problem even in heavy stop n go traffic for an hour plus. Makes me think something is going on with your truck that you need to get figured out. About the only other mod I have done on mine was to remove the check valve going to the fuel separator. Mine was blocked and my tank build enough pressure to make gas tank vent lines whine when it was hot and I’d been on a long run. Don’t know if that makes a difference but it’s pretty easy to pull and find out.

Best of luck and super looking 40 you’ve got there.

 

[Boaf 32]

This crossed my mind. But what confuses me is the full fuel tank runs great and 3 gallons later it’s dead. The temptation is to change a bunch of stuff but then I’ll never know what actually works.

Do you have debris in the tank? My 72 ran fine as soon as the debris was sucked down below half a tank, blockage. Just one other thought after new tank, and gasket.

 

[Boaf 32]

Do you have debris in the tank? My 72 ran fine as soon as the debris was sucked down below half a tank, blockage. Just one other thought after new tank, and gasket.

Methodical approach. Check one, move on. One of the other LC'rs told me it's usually a combination, Fuel, Air, Spark. No Fuel in the glass mean's it's not getting ot the carb. Check also Fuel Pressure and volume. I read 8 ounces after 15 seconds of cranking (don't think that is the problem), but a methodical step.

Vapor lock, maybe, air may be getting in a clamp. Good hunting.

Boaf

 

[Dizzy]

@Solace in Solitude

How did you plumb the stock oil pressure sending unit with the oil pressure safety switch?

 

[hooter]

Thanks for the info

 

[emac]

If you narrow it down to vapor lock, why not try insulating the fuel line? Especially the line from the pump to the carb. Ethanol fuel sucks.

I remember the old datsun z cars in 1974 had factory insulation around the fuel lines because the flat top carbs had so many vapor lock problems.

 

[Solace in Solitude]

@Solace in Solitude

How did you plumb the stock oil pressure sending unit with the oil pressure safety switch?

I used this —> Amazon product ASIN B00QXK0QSW

 

[thebigredrocker]

As mentioned above, it's chemically harsh on many of the rubber & leather parts. It also draws moisture, leading to rust & corrosion.

There is a driveability difference with RFG because of the higher vapor pressure / lower BP. This translates to fuel boils out of carb bowl overnight, leading to hard starts next day. Fuel boils out of carb bowl sitting in traffic, leading to rough,stumbly hot idle. Fuel is easier to vapor lock in the pump, making it hard to reprime the system if tank level is low.

 

[Pin_Head]

Chances are good that it is just a flake of rust or some other piece of dirt swimming at the bottom of your tank that covers the fuel outlet and starves the pump of fuel.

Modern vehicles built after about 1950 are pretty resistant to vapor lock because they have the tank fuel level above the inlet for the fuel pump. The later 40s also have a fuel return line to keep the fuel moving and lower the chances of vapor lock.

 

[hooter]

Chances are good that it is just a flake of rust or some other piece of dirt swimming at the bottom of your tank that covers the fuel outlet and starves the pump of fuel.

Modern vehicles built after about 1950 are pretty resistant to vapor lock because they have the tank fuel level above the inlet for the fuel pump. The later 40s also have a fuel return line to keep the fuel moving and lower the chances of vapor lock.

I hope I can find said rust flake.
Any idea why this happens only when it is hot out or when the tank is less than full? The tank was a new OEM tank placed 18 months ago and all lines, filter etc were replaced.

 

[Pin_Head]

The less volume of gasoline, the less chance the POS is going to swim over the outlet. Have you tried it in cold weather?