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Jacket
09-27-2009, 08:48 AM
So the full day of wheelin' and driving brought back some attention to an issue I first experienced when I drove the 40 home from Baton Rouge. Here are the basic symptoms I've experienced:

- Significant hesitation at speed, or when trying to maintain highway speed
- With foot on pedal at speeds above 45 mph, the truck will occasionally lose throttle and hesitate, as if the fuel delivery is interrupted.
- Intermittent. If I let off the gas, and then "re-accelerate", the engine responds well for a bit and then will hesitate again.
- definitely more noticeable trying to climb hills (i.e., Eisenhower tunnel)
- no issues with low speed acceleration, or maintaining power on trails with steep climbs
- possibly associated with a fully warmed engine?

Even driving east on Arapahoe yesterday after returning from Summit Cty - a route I drive routinely with no issues - I experienced a bit of hesitation. The worst of it was climbing up to the tunnel, where I was in 3rd going about 30 mph and struggling to maintain speed.

So my instinct tells me I should start with the fuel system: fuel pump, fuel filter, carb? Or timing? This is on my FJ40 with stock drivetrain.

TIMZTOY
09-27-2009, 10:47 AM
i would have to second fuel delevery. I would forget about the pump for now. And change the fuel filters. You only need one inline. Timmbuck2 had 3 or 4 LOL. Ofcorse the proper thing to do, would be to run a fuel pressure test and get the truck to duplicate the problem while looking at the gauge. Ie run the gauge into the cab and drive the truck keeping an eye on the pressure Because it could also be carb tuning or timing. Even vacume leak but doubt it.
Start with pressure test and that will give you a direction as to were to look :thumb:
Pm me if you need me to come give a hand

MDH33
09-27-2009, 10:52 AM
I would also throw a timing light on it. Hesitation could be a misfire also. I was also thinking fuel delivery, most likely a clogged main jet since it's happening at higher speeds.

You mentioned at the 40's Run a carb rebuild. If you get me the spare you have and a rebuild kit, I'd be happy to set it up for you.

:beer:

TIMZTOY
09-27-2009, 11:10 AM
A timing light for sure. I thought I mentioned that. Oh well must have just been in my head. :lmao: good save MDH33

rover67
09-27-2009, 04:54 PM
Hey Matt, Mine was doing the exact same thing. I rebuild the carb since it felt like a lean miss and it ran well after that. You may want to just get the rebuild kit from NAPA (just for the gaskets) take the top off of yours and just give it a quick going through. also check your fuel level in the bowl and reset if needed.

I also checked the timing (it was fine), adjusted valves (they were pretty close), checked vacuum (it was 15 inches and steady), did plugs, wires, cap, rotor, and tightened manifild bolts. None of that changed it, but the carb rebuild did. Not saying none of that is wrong with yours just relaying what I went through. I know I have a small vacuum leak at my manifold gasket but i'll leave that till later.

Like the other folks said, change the fuel filter. Undo the fuel line at the carb and let it pump gas through for a bit to flush anything that may have gotten past the old one after installing the new one. I've seen fuel filters come apart in the past and cause all kinds of headaches with carbs. When you pull it off cut it open and check it out.

Jacket
09-27-2009, 07:02 PM
Thanks for the ideas. I had a new fuel filter on hand so I went ahead and put it in this afternoon. The old one didn't look that old/bad...

To PO indicated he "replaced the carb gaskets", but I think that a total carb refresh seems like a good idea at this point. Speaking of which - my rig came from sea level, so is there any rejetting or other adjustments I should make in the fuel system? From what I've read, most folks advance timing a bit over spec up here to compensate for the thin air. Anything else?

SteveH
09-28-2009, 08:37 AM
I have a new genuine Toyota mechanical fuel pump and clean filters and I still had to retrofit my '78 FJ40 with an electric fuel pump. Regulated to 5.5 psi, it instantly solved a variety of heat-related issues - hot soak problems, classic vapor locking while driving, and cold start issues. So, don't rule that out if all else fails. IMO - don't buy a Holley red/blue pump, however - they are not sealed and mine quickly failed due to dirt contamination.

powderpig
09-28-2009, 08:49 AM
Make sure the advance in the distibutor is moving freely. If this is not working well, it will also create the same type of feeling

Jacket
09-28-2009, 09:41 AM
Thanks for the additional suggestions. The funny thing about it is:

- the 40 starts great, even in the cold months
- it idles really well, albeit a bit high (still tuned for passing emissions)
- throttle response in 1st-2nd gear is normal
- I've never noticed the problem during local driving, even at speeds > 45mph

So there's something specific to the high speed throttle, and something about it being fully warmed and running over a long period of time.

MDH33
09-28-2009, 09:46 AM
Thanks for the additional suggestions. The funny thing about it is:

- the 40 starts great, even in the cold months
- it idles really well, albeit a bit high (still tuned for passing emissions)
- throttle response in 1st-2nd gear is normal
- I've never noticed the problem during local driving, even at speeds > 45mph

So there's something specific to the high speed throttle, and something about it being fully warmed and running over a long period of time.

Maybe it's when your secondaries open? Probably a clogged jet or passage in the carb.

subzali
09-28-2009, 12:13 PM
I think a way you could check fuel delivery is to hold the idle up for a while and watch the fuel in the bowl. Have you checked your plugs for fowling/wrong gap? Plus what everybody else has already said...

throw some alcohol in your tank to get rid of any water that might be in there?

Why is this in Chat?

Jacket
09-28-2009, 04:47 PM
Why is this in Chat?

:dunno::comp:

Rezarf
09-29-2009, 09:31 AM
Matt-

I was going to retune my carb soon here if you want to tag team it and do both at once. I am going to clean it up, reset the idle and mix and check over the timing and tune up the valvetrain.

Let me know, I have been there a few times before it is simple.

Jacket
09-29-2009, 08:53 PM
I put the light on it tonight, and sure enough it was right at factory spec (7*). I went ahead and adjusted it to 12* per this thread. (http://www.risingsun4x4club.org/forum2/showthread.php?t=10482&highlight=timing)

I guess I'll put all my money on the carb rebuild, and give that a shot next. I've got plugs, wires and a cap around here somewhere so I could try that too (but the wires and cap on there now seem pretty new).

rover67
09-29-2009, 10:31 PM
That's right where my timing was set (6 degrees).

remember to count the number of turn out the idle mixture screw is if you take it out... some books I have say stock is two turns, others say three. or you can tune it using what they describe as the "lean drop" method.

I didn't pull my idle misture screw out when i went through mine just because I didn't want to change it, and it was easy to blow out through the passage that goes to the main bore. I have run into trouble forgetting what a stock setting is for an idle mixture screw on motorcycles before and wished i had taken note of where it was originally because it's easy to bounch around a certian number of turns looking for what runs the best. I've found where they had it set at stock was best.

Rezarf
09-30-2009, 01:06 PM
Matt- I just realized why your 40 is hesitating at speed...

































... its a FJ40! :D

Jacket
05-08-2010, 09:32 AM
Well after nearly 1100 miles on the FJ40 between Boulder, Moab, the Swell, and back, I'm pleased to report that the hesitation is completely gone. I rebuilt the original carb last fall (Oct/Nov), soaking all parts in carb cleaner, blowing everything out and replacing all the gaskets. It's been running great since then, but the Moab trip proved that whatever the issue was, it's been resolved by a refreshed carb.

I still barely held 35mph in 3rd gear over Eisenhower and Vail Pass, but that's to be expected with a 2F. Case closed.

MDH33
05-08-2010, 10:10 AM
Well after nearly 1100 miles on the FJ40 between Boulder, Moab, the Swell, and back, I'm pleased to report that the hesitation is completely gone. I rebuilt the original carb last fall (Oct/Nov), soaking all parts in carb cleaner, blowing everything out and replacing all the gaskets. It's been running great since then, but the Moab trip proved that whatever the issue was, it's been resolved by a refreshed carb.

I still barely held 35mph in 3rd gear over Eisenhower and Vail Pass, but that's to be expected with a 2F. Case closed.

Awesome that it's running well.

Very :cool: you drove your 40 on the whole trip too. :thumb:

DaveInDenver
05-08-2010, 01:16 PM
I still barely held 35mph in 3rd gear over Eisenhower and Vail Pass, but that's to be expected with a 2F old Toyota.
Yeah and I second Martin's comment, I really dig it when people drive what they 'wheel. Trailer queens strike me as silly as driving someplace to ride a road bike.

subzali
05-08-2010, 09:37 PM
very :cool: Matt :thumb:

subzali
02-08-2011, 11:27 AM
Rather than gum up Ricardo's thread...

Do you think it was something internal to the carb you fixed, or something like a vacuum leak that was also fixed at the same time? Were there any major issues when you did the rebuild, like check balls missing or stuck, secondary diaphragm torn, etc.?

Jacket
02-08-2011, 02:00 PM
It's been a while now since I did the work, but there was nothing significant I documented as missing or broken when I dissembled. I soaked everything (metal) in carb cleaner for a day or two, and ended up buying 3 different rebuild kits to make sure I could replace all lost, missing, or worn parts and all gaskets (oddly enough the Napa kit is way more detailed then the Keyster kits). I reinstalled the stock jets to baseline it after the rebuild, but they've done well enough for me to not bother trying to re-jet for high altitude. Everything else was tested, reinstalled and adjusted per the FSM.

So maybe it was an air leak, vacuum leak, clogged jet, sticky valve or some combination of things? I bought a spare carb (12/75) off Mud for $30 in case I blew it or needed parts - but I only used it as a point of reference for reassembly.

It was definitely worth the time, and I had fun doing it.