Fj40 1968 with single barrel Aisin running rich

[Jaskas]

Hi guys.

Im have been trying to look for advisory on what is assume is that my FJ is running rich. The assumption is based on that there is quite a lot of black sut on in the exhaust and on wot it does smoke dark smoke. Also the exhaust gas does smell quite horrible.

I have done a full rebuild on the car. On the engine ONLY the head has been resurfaced (nothing else major done) and carb rebuild and ultrasonicly cleaned. Plugs, plug leads, and distributor cap/rotor is new.

The carb rebuild kit did not have all the parts for the rebuild but 90% anyway. I dont remember what was missing as this wss few years back. The fuel level is correct on the glass on the carb. The engine did run the same way before the repairs.

Symptoms:
- Hard cold start. At first it seems to start for few revolutions with the fuel in the carb, but then you have crank it a long time. It looks like as the fuel line and/or carb drains empty and then fills when cranking a while. Warm start not a issue.
- The power seems to be there, but there is a slight hesitation when suddenly pushing the pedal to the floor. I don't know is this normal or not
- Dark smoke on heavy load / WOT.
- The car smells on idle and driving quite a bit

I havent really found advise on adjustment of my presumed Aisin single barrel carb really anywhere.

Do you have any advice where to start?
-Vacuum?
-Something wrong with carb as it drains?
-Carb adjustment? How?

Edit. The carb type is D40 (with bigger window) I beleive.

Br, Jaakko from Finland

 

[charliemeyer007]

Nice rig.

Vacuum leaks - runs lean.
Could be timing is retarded.
Pinhead on youtube vid's for carb adjustment.

Do a dry then wet compression test. Maybe the rings never seated due to wrong oil for break in. Valve stem seals?
What do the plugs look like? All the same or some way worse. Just because you bought new parts doesn't mean they are good.

 

[Jaskas]

Nice rig.

Vacuum leaks - runs lean.
Could be timing is retarded.
Pinhead on youtube vid's for carb adjustment.

Do a dry then wet compression test. Maybe the rings never seated due to wrong oil for break in. Valve stem seals?
What do the plugs look like? All the same or some way worse. Just because you bought new parts doesn't mean they are good.

Thanks for these.
-Timing has been checked
- I did not touch any of the engine internals. Only the head was resurfaced. I dont think that this is a oil burning issue.
- Compression check could be worth doing
-Pinhead YouTube videos are helpful, but he is working on a different type of carb.

 

[charliemeyer007]

Rings could be stuck, and not sealing well - oil control ring(s) plugged - valve guides and or seals worn.

If compression is low/un even or improves a lot wet - put a spoonful or two of Marvel's mystery oil in each cylinder. Pull the engine thru 2 revolution to distribute the oil. Let it soak for a few days. Drive it hard for a while - Italian Tune Up

Maybe factory service manuals, free downloads

Land Cruiser Factory Service Manuals (FSMs)

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

www.cruisercult.com

 

[Jaskas]

Charlie, please explain me your reasoning why stuck rings or loose valveguides/seals would cause rich running conditions? What is your reasoning behind this?

Also, trust me. I have been running the car hard for couple of thousand miles after the rebuild. I think the stuck rings would be loose allready, or more severe damage would have happened.

Also to the FSM. There is not really advice for this carb, this is why I'm asking this. All the adjustment according to the FSM has been done

 

[ceylonfj40nut]

Hook up a vacuum gauge to manifold vacuum and get reading at 650-690 rpm and factory timing. Should be steady and about 17-20 inches of vac. If needle is bouncing there are other issues. Google diagnostics with vacuum gauge. There are some pics with explanations. The vacuum gauge connected to ported vacuum on the carb as above pic can be used to lean out your carb to factory spec.

 

[Jaskas]

Hook up a vacuum gauge to manifold vacuum and get reading at 650-690 rpm and factory timing. Should be steady and about 17-20 inches of vac. If needle is bouncing there are other issues. Google diagnostics with vacuum gauge. There are some pics with explanations. The vacuum gauge connected to ported vacuum on the carb as above pic can be used to lean out your carb to factory spec.

Is the idle adjust screw the only thing I should adjust? Does this affect AFR while driving as well?

 

[ceylonfj40nut]

Idle adjust screw and idle mix screw. Back and forth until you reach the highest possible vacuum. Look up the lean drop method to carb tuning

 

[charliemeyer007]

I was thinking its rich from burning oil. That's why I ask what the plugs look like and for the dry/wet compression test to see what the rings are doing. Plugged up oil control rings will make it burn oil even if it has good compression. Loose/worn valve guides (can also effect compression) or bad seals both will/can allow it to burn oil. Fouled plug makes it smell/look rich

It could also be the carb, maybe you didn't get something correct and fuel is pouring threw some gap/pinched/torn gasket.

 

[Jaskas]

Thanks for the support guys.

To confirm the carb adjustments om my Aisan d40. Which is the carb adjustment and which is the carb mix screw? Only external adjustment screw seems to the ones in the pics attached.

 

[charliemeyer007]

So what does that screw look like. Usually they are a long smooth taper. If someone cranked it down gorilla tight, there will be a ring swaged into the taper. The seat will also likely be damaged too, tho harder to see. If the screw/seat are damaged then actual adjustment will be almost impossible because the smallest turn of the screw results in a giant change due to the lack of the smooth taper.

Put on the pressure regulator and set to 3 or 4 PSI. Maybe fuel is leaking internally (runs rich) while not raising the level in the window

 

[65swb45]

Do a compression test. Period. There are many known cases of rebuilt engines with rings that didn’t seat. I just had one in my shop two weeks ago. It’s not what you want to hear. But it’s what you need to know.

Marks Off Road Home Page - https://marksoffroad.net/index2.html

 

[Jaskas]

Thanks for replies. Maybe my initial post was a bit misleading. The engine was not fully rebuild. Only the head was resurfaced + new headgasget was put on. That said, it might still be that some of the rings could be stuck as the engine was sitting for a long time. -> Compression check will done.

Still on my question on the carb adjustment: Which is the carb adjustment and which is the carb mix screw. Or is there even both of these on this carb?

 

[Jaskas]

I think I got it now. The idle mix screw is the big brass one ( in the first pic) and the idle screw is the one which is adjusting the throttle valve itself (not in the pics)
Found also a nice old thread clearing out the functions of the carb quite nicely: Aisin carburetor idle circuit routing - https://forum.ih8mud.com/threads/aisin-carburetor-idle-circuit-routing.795118/

Next up:
- Compression check
- Adjust the carb with leaning out method

Will be traveling for a few weeks, but will post about the progress.