Trouble with carb / engine hesitates upon acceleration (1 Viewer)

[procomsignathid]

Hello all!

Yesterday I disassembled / cleaned my carb as I could not get the engine to stably idle below about 1100 RPM. I've had some issues recently with debris in the gas, and have since installed a 2nd inline filter with a much finer screen. Unfortunately, this was after I had the shop rebuild the carb, and it looked like the idle ckt was clogged again (I noticed fuel coming in from the venturi).

I followed (as best I could) the YT series Pin Head put together (). Note that I did not give the carb another bath, but cleaned as best I could w/ carb cleaner and compressed air everywhere I could.

The good news is that the engine now idles just fine, even as low as 400, but Ive adjusted the idle speed screw for around 650ish (based on the cheap tach Ive got anyhow). The bad news is that when I accelerate, the engine nearly dies. I can rev it in certain throttle positions, but it's like it's just not getting enough fuel. I verified the accelerator pump is working as well (it is), but Im not sure how big of a spray it should produce.

Looking at the glass during idle, it does seem a smidge low. I adjusted the float to these specs (AISAN Carb issues - https://forum.ih8mud.com/threads/aisan-carb-issues.1159560/page-2), namely 6mm from the carb base (not including the gasket) to the float when inverted, and 1.1m when lifted between the needle valve and the float.

I'm getting about 15" of vacuum at idle (which is an improvement from before the disassembly, it was around 12"). I also took a vid which may be helpful... Audio isn't great when I rev the engine but it shows vacuum (taken from the intake manifold), RPM, fuel level in the bowl, the accelerator pump jet and the behavior Im getting when I accelerate the throttle:

Any help would be hugely appreciated!

 

[Pighead]

What is your timing set at?

 

[procomsignathid]

Went and got a timing light, had to adjust the dizzy a bit. Not sure if it I did it correct, but I connected the timing light to cyl #1 (front-most but I may be mistaken), couldn't see the BB anywhere. There was a scratch on the flywheel that could be used for timing I guess? It's a SA import so who knows what they did. On a lark, I moved the timing light to the rear-most spark plug wire (closest to cab), and I could see the BB. I set it right on the needle, then advanced about 5 degrees so the BB was at the bottom of the window (searching around it seems folks like around 12d BTDC). This is my first go-around, so pardon what is likely incompetency!

This effectively advanced timing by a small bit, which gave me 1 more inch on the vacuum and slightly reduced the issue I was having, but its still there. I followed the drop lean method as outlined in , got to around 650 idle, and took it for a spin... It's technically driveable, but from every stop when i start to accelerate the truck nearly dies (I need to feather in a bit more gas). Got it around the block a few times and drove it back.

Scratching my head a bit...

 

[charliemeyer007]

Timing is usually set on #1 by the radiator.

Maybe download some free manuals

Land Cruiser Factory Service Manuals (FSMs)

Factory service manuals (FSMs) for your Toyota Land Cruiser ! From the 1950s to the present!

www.cruisercult.com

Make sure your manifold bolts are torqued properly. Check the bolts/nuts and screw on the carb too.

Put some gas dryer in the tank, and go for a drive to mix it and get it to the carb. Paper elements in fuel filter don't readily pass gas if wet with water. Leave them out in the sun for a few days they will dry out and you can use them again.

 

[procomsignathid]

One other thing that popped into my head… Are my nozzles backwards? I read this thread (2F Aisan Carburetor Jets and Venturi question/help - https://forum.ih8mud.com/threads/2f-aisan-carburetor-jets-and-venturi-question-help.975566/) and it looked like for his carb the main nozzle was a 5, secondary was a 3. Mine seems the opposite of that (see pic). I have the shorter tube on the primary side (stamped 55).

 

[procomsignathid]

Timing is usually set on #1 by the radiator.

Maybe download some free manuals

Land Cruiser Factory Service Manuals (FSMs)

Factory service manuals (FSMs) for your Toyota Land Cruiser ! From the 1950s to the present!

www.cruisercult.com

Make sure your manifold bolts are torqued properly. Check the bolts/nuts and screw on the carb too.

Put some gas dryer in the tank, and go for a drive to mix it and get it to the carb. Paper elements in fuel filter don't readily pass gas if wet with water. Leave them out in the sun for a few days they will dry out and you can use them again.

Do you think there's water in the tank clogging the fuel filter? I'm wondering if I adjusted the float improperly as well. I will definitely check torque on the intake manifold / carb.

 

[charliemeyer007]

Warm days and cold night will condense water out of the air into the tank. Keeping your tank full helps prevent the condensation if you don't drive it a lot. It take very little water in the fuel to clog the fuel filter - that could make it hard for the fuel pump to keep the float bowl full.

 

[Pighead]

This effectively advanced timing by a small bit, which gave me 1 more inch on the vacuum and slightly reduced the issue I was having, but its still there.

If advancing the timing a little helped a little, try advancing a bit more. Practice timing, it'll come in handy. Follow your plug wires and see if they are plugged into correct socket on dizzy cap. Make sure you are timing to TDC #1 and not #6. Most people like 17* BTDC. I like a little more.

 

[Skreddy]

If you can’t see the bb at idle with the timing light on cylinder #1, start there. Do you have a vacuum advance or retard distributor? Is it hooked up? Is it working? Is it hooked up when you’re setting your timing?
Have you adjusted your valves lately? How new are plugs, wires, cap, rotor, gas, vacuum lines, etc.

 

[procomsignathid]

If you can’t see the bb at idle with the timing light on cylinder #1, start there. Do you have a vacuum advance or retard distributor? Is it hooked up? Is it working? Is it hooked up when you’re setting your timing?
Have you adjusted your valves lately? How new are plugs, wires, cap, rotor, gas, vacuum lines, etc.

Fair point, Ill dig back into it tonight. I have a vacuum advance dizzy, and for timing i unplugged it (and plugged the hose).

Im guessing i will have to go old-school to find TDC if the flywheel isnt timed to cylinder #1.

 

[Skreddy]

You should see the bb on 1 and 6 at TDC since they are on the same “phase”, but they fire 180* out from each other. Are the plug wires on the cap in the right order?

 

[procomsignathid]

You should see the bb on 1 and 6 at TDC since they are on the same “phase”, but they fire 180* out from each other. Are the plug wires on the cap in the right order?

No idea, Ill trace em out. Is it even possible for it to idle smoothly if the wires are out of order?

 

[procomsignathid]

OK, I checked the timing light hooked up to the lead on cylinder #1, and I could see the BB… gonna chock that up to user error. I adjusted timing (again without the vacuum advance plugged in) so the BB was in the lower part of the window.

I also adjusted the accelerator pump linkage to get around 8-9mm of travel. Both of these things seemed to help a bit, but problem still persists.

Fuel level seems low in the glass, and Im wondering if I put too much gap between the cast surface of the carb top and the float (I did 6mm, but am seeing other folks online suggest 4mm).

Also mapped out the wires, see below:

 

[charliemeyer007]

I think your cap wires are in the correct position. Look at the contacts inside the cap. Aluminium ones can get a heavy layer of oxide build up - its an insulator. You can take the small blade on your swiss army knife and scrape off the oxide. I prefer caps that have brass contacts NAPA Echlin for example were that way. Also make sure its corrosion free inside where the plug wires go in. On a dark night open the hood and start the engine - look for dancing fire sparking out of the wires - old insulation can have micro cracks that leak and reduce spark at the plugs. Make sure the center electrode on the plugs is square - I use a flat needle file to true them up and then gap them.

 

[procomsignathid]

Alright, did lots of t-shooting today, and I think I'm in a good spot! Short version if you don't want to read to the end: It was the E85 gas.

I checked torque on the intake manifold bolts, that was good (barely any tightening, and it didn't make a difference for the vacuum). Vacuum has stayed around 16". I checked all the spark plug connections and the inside of the dizzy (I definitely have one with aluminum contacts). Everything looked clean, but i gave everything a hit of electrical contact cleaner (both ends of the main wire and each spark plug wire, the points and contacts). No real improvement.

I then took the top of the carb apart (for 3rd time), and adjusted the float to 4mm off the cast surface. After re-assembly, no difference in fuel level in the bowl. Then I took off the first inline filter temporarily and blew compressed air back into the tank until I heard bubbles. Re-connected, and bam, fuel level increased in the bowl. I definitely have crud clogging up the pickup. That said, it still didn't solve the acceleration issue!

Next up, I decided to go after that bee in my bonnet about swapping the #3 and #5 venturis... Took the top of the carb apart for the 4th time and swapped em. Ya that was a bad idea... truck had no power on acceleration (not just stumbling). Took top of carb apart for 5th time and put em back.

By now I was getting into a bit of a routine with the lean/drop method. I also found that it was easier to back the choke adjustment screw way out so it wouldnt interfere with the idle speed screw (then when I was happy w/ idle, i screw the choke adjustment screw back in until its just off the plate).

By now the truck was driveable, as long as I feathered the throttle. Had to run the kids to a bday party, so I decided to try my last option to think of... The gas. I had drained the tank earlier in the week to about 1/4 tank (took 5gal out), and filled up with about 7gal of E85 to pass emissions. Worked a charm (to pass), but I started thinking it was the E85 causing my woes. Drove around for a bit, and put the 5gal of normal gas back in that I took out... Bam! No hesitation issues at all.

I feel like a total idiot, got so zoned in on the adjustment of the carb / timing etc that I mindlessly ruled out the E85. Truck is back to driving healthy again! Next up, new gas tank...

Thank you all for your help in this thread! Silver lining is that I am now very comfortable with the innards of the carb as compared to the start of the week...

 

[a77fj40]

Would old gas cause this same issue? I have the same issue but i didn't use E85.

 

[procomsignathid]

Google seems to think so (I did a quick search and it suggested that rough idle / sluggish acceleration could be issues). Based on my experience w/ E85, I think its totally possible... Depending on how old I would think there could be issues w/ the gas gumming things up in the carb as well. Is your accelerator pump working OK?

Do you have new gas you could add to the tank?

 

[pb4ugo]

Would old gas cause this same issue? I have the same issue but i didn't use E85.

Yes, gas is always going to degrade overtime. If the old gas is an ethanol mix it degrades quickly. Maybe over a yr or more. The ethanol tends to absorb moisture overtime. because of the alcohol/ ethanol in it. Once it gets saturated separation inversion occurs which can't be reversed. The water/ethanol separates from the gas and it migrates to the bottom of the tank and the left over gas is on top. The left over gas is useless. This mix cannot be refreshed and needs to be pitched. If you think it's bad gas, hook up a secondary fuel can with fresh gas and see if it runs better.

 

[a77fj40]

My problem is that it runs fine sometimes. Ill be driving along find and then it will lose power and run exactly like the above video. I have an aux tank that has very old gas in it and im thinking that somehow a slug of old fuel is getting pulled into the system somehow periodically.