hi I have a 79 fj40 with the 2f engine. I am getting horrible mileage. What can I tune up or replace to improve?
Getting Bad Milage
- Thread starter Spenny
- Start date
-
- Tags
- fj40 gas mileage
This site may earn a commission from merchant affiliate
links, including eBay, Amazon, Skimlinks, and others.
Whats bad for you? My old 2f and 4 speed used 18l per 100km. Replaced with a 12ht and 5 speed so now 9.5l of diesel per 100km.
1911
chupacabra
Define "horrible".
10-12 mpg is pretty common. With the right gearing, tire size, and a tail wind, you might could get 14-15 on a good day.
With the mighty 2F, you get gobs of torque at low rpm; you get remarkable strength and reliability, and you get ease of maintenance and repair. What you not get is high horsepower, easy freeway speed, or fuel economy. Every four-stroke gasoline engine is a compromise; the designing engineer picks his priorities and goes from there.
10-12 mpg is pretty common. With the right gearing, tire size, and a tail wind, you might could get 14-15 on a good day.
With the mighty 2F, you get gobs of torque at low rpm; you get remarkable strength and reliability, and you get ease of maintenance and repair. What you not get is high horsepower, easy freeway speed, or fuel economy. Every four-stroke gasoline engine is a compromise; the designing engineer picks his priorities and goes from there.
'Horrible mileage' can mean many different things... as @1911 said, 10-12 is common.
Here's a pertinent thread that is running just ahead of your question... maybe it will offer insight into just where the true value of an old FJ40 lies.
Which 2 Barrel Carb will give me the best MPG for my FJ40 with a 2F engine
A few suggestions:
1. Keep tires properly inflated.
2. Eliminate vacuum leaks.
3. Rebuild/tune carburetor.
4. New/clean spark plugs (Denso (W14EXR-U) -- Properly gapped plugs.
5. New spark plug wires.
6. New PCV valve.
7. Properly adjust timing.
8. Properly functioning vacuum advance.
9. Properly adjust valve lash.
10. Keep fuel filter clean.
11. Keep air cleaner filter clean.
12. Drive frugally... no quick(
) starts. Keep speed at ~55 or less. Or, install a Tach and keep it in the green.
The only time mine is economical is when it's in the garage ... and even then, it always finds a way to spend my money.
Here's a pertinent thread that is running just ahead of your question... maybe it will offer insight into just where the true value of an old FJ40 lies.
Which 2 Barrel Carb will give me the best MPG for my FJ40 with a 2F engine
A few suggestions:
1. Keep tires properly inflated.
2. Eliminate vacuum leaks.
3. Rebuild/tune carburetor.
4. New/clean spark plugs (Denso (W14EXR-U) -- Properly gapped plugs.
5. New spark plug wires.
6. New PCV valve.
7. Properly adjust timing.
8. Properly functioning vacuum advance.
9. Properly adjust valve lash.
10. Keep fuel filter clean.
11. Keep air cleaner filter clean.
12. Drive frugally... no quick(
) starts. Keep speed at ~55 or less. Or, install a Tach and keep it in the green.The only time mine is economical is when it's in the garage ... and even then, it always finds a way to spend my money.
GA Architect
SILVER Star
That right there is the "Classic Quote of the Month"!............Nice one D.
...hijack over..........
Look at timing and fuel. Make sure your distributor is working properly and test to ses if the advance is working. Then check the carb and see if it's running too rich.
- Thread starter
- #8
Thanks for the input. It's been getting colder and now it won't really run well without using the choke at about half. Does anyone know what that could be from.
My wife said to get another car....
Even she knows these are mistresses and the cozt Money.
Even she knows these are mistresses and the cozt Money.
Vacuum leak. Check around the carb and intake manifold. Use a can of carb cleaner spray and spray near the areas I just mentioned. When it revs up a bit, you've found a leak.
*Edit - ...unless you are talking about right after starting the engine. Typically, these need the choke pulled for a few minutes after starting until the engine warms up a bit. If it still runs rough after the engine warms up and only smooths out with the choke, then you have a vacuum leak.
rrv333
SILVER Star
FJ40 = Horrible fuel mileage
- Joined
- Apr 14, 2004
- Threads
- 1,476
- Messages
- 37,050
- Location
- 818-953-9230
- Website
- www.marksoffroad.net
And when you're running half choke, what are your RPMs? High enough to drown out a malfunctioning idle circuit...and also mask a vacuum leak?
- Thread starter
- #13
Drive it home last night and backfires really bad. I wonder if I could have somehow purchased bad fuel?
I will also begin to look for the vaccum advance, plug wires
For the vaccum advance...is this a part that you can rebuild or does this require you to purchase new?
Thanks
I will also begin to look for the vaccum advance, plug wires
For the vaccum advance...is this a part that you can rebuild or does this require you to purchase new?
Thanks
Here’s some vacuum advance info links
1979 fj40 vacuum advance - Yahoo Search Results
Here’s a SOR diagram that shows the vacuum advance as item #42
Page 022 Land Cruiser Distributor 1958-8/92 - Std, Semi-Electronic & Electronic
Bottom line... the original vacuum advance module is OLD and is subject to vacuum advance diagaphram failure. To my knowledge, there are NO rebuild kits available. It’s not easy to pulls the module apart and ‘fix’ it, with no new diagaphram available... although, I’ve read that some have succeeded, by using PlastiDip to ‘repair’ the diagaphram... I have no idea how long the repair lasts.
In my case, the diagaphram was the source of a fairly significant vacuum leak (17”@650 rpm), robbing 44 of power and fuel ‘economy’.
I replaced my distributor and vacuum advance module with a D.U.I. and saw a significant increase in power and a static 20” of vacuum, at 650rpm... I don’t know what sort of increase in mpg occurred... I never bother to check.
You can buy a used dissy (distributor)... try Mark (@65swb45) at marksoffroad.com (but call him, he’s old school), or eBay. But, buying a used vacuum advance was a nonstarter for me... how do you know the diagaphram condition?
There are other dissy/vacuum advance options on eBay, but I can’t speak to their reliability.
You never defined ‘horrible’, as in gas mileage... we can’t offer specific insight if you don’t answer our questions.
@FF LC FREAK provided you a starting point for finding vacuum leaks... have you tried it yet?
@65swb65 is an expert in Aisin carburetor rebuilds... answer his question and see what he suggests.
Do a lot of searching and reading and learn about what you have... it’s an expensively fun hobby.. both driving it and working on it... but, it’s best to know where to start whenever it breaks.
Good luck!!
1979 fj40 vacuum advance - Yahoo Search Results
Here’s a SOR diagram that shows the vacuum advance as item #42
Page 022 Land Cruiser Distributor 1958-8/92 - Std, Semi-Electronic & Electronic
Bottom line... the original vacuum advance module is OLD and is subject to vacuum advance diagaphram failure. To my knowledge, there are NO rebuild kits available. It’s not easy to pulls the module apart and ‘fix’ it, with no new diagaphram available... although, I’ve read that some have succeeded, by using PlastiDip to ‘repair’ the diagaphram... I have no idea how long the repair lasts.
In my case, the diagaphram was the source of a fairly significant vacuum leak (17”@650 rpm), robbing 44 of power and fuel ‘economy’.
I replaced my distributor and vacuum advance module with a D.U.I. and saw a significant increase in power and a static 20” of vacuum, at 650rpm... I don’t know what sort of increase in mpg occurred... I never bother to check.
You can buy a used dissy (distributor)... try Mark (@65swb45) at marksoffroad.com (but call him, he’s old school), or eBay. But, buying a used vacuum advance was a nonstarter for me... how do you know the diagaphram condition?
There are other dissy/vacuum advance options on eBay, but I can’t speak to their reliability.
You never defined ‘horrible’, as in gas mileage... we can’t offer specific insight if you don’t answer our questions.
@FF LC FREAK provided you a starting point for finding vacuum leaks... have you tried it yet?
@65swb65 is an expert in Aisin carburetor rebuilds... answer his question and see what he suggests.
Do a lot of searching and reading and learn about what you have... it’s an expensively fun hobby.. both driving it and working on it... but, it’s best to know where to start whenever it breaks.
Good luck!!
A lot can be learned from hooking up a vacuum gauge to diagnose problems. That being said...I get about 10MPG...Doesn't matter, because the joy I get from driving her.
