Going Aisin-details, details, details

[77mustard40]

What frustration! After working on a second source for 12V I finally figured out that the original was fine by unplugging it, turning the key on and then making the connection again...and click.

So why am I having trouble getting it to run (or start for that matter). Set choke and turned it over a lot with an occasional half stroke on the accelerator. Checked to see that power valve is delivering fuel then got worried I had it flooded and laid off for an hour. Came back and right on the first crank it wants to turn over but no.

After waiting some more I tried again and got it to start, the fast idle with the choke kept it running so I let it warm up for a couple of minutes. There seemed to be decent response to the pedal so I put the top on the air cleaner and went for spin in the hood. In the first five minutes as it continued to warm up it seemed to be running better and better. I ran through the gears on an incline and had solid performance, it really pulled well in third and forth. On my way home I stopped at a red light and noticed the idle was beginning to struggle so I pulled the choke slightly. With in a couple of minutes and almost home it barely would respond to the pedal, it just wanted to bog down. I stalled it a couple of times by dropping the clutch while rolling and used my momentum to refire it.

Got home and nursed it to an idle and went back through the idle speed and mixture settings, still laboring idle. Thinking maybe the solenoid is an issue I unplug it while it's running and it dies instantly. Re start and place a vacuum Gage on it, reads 17 with the laboring idle, will drop to 10 with the accelerator and peak at 20 as it drops back to idle. I pull the timing light, still lit just below (advanced slightly) the mark. I've noticed I have heavy soot at the exhaust on the garage floor. I don't know if it was from my first labored start or later, but it seems that I am real rich. I'm all ears as to where to go with this tomorrow evening when I get my next shot.

 

[Pin_Head]

The cold start drill is pull the choke all the way out (you did check that the cable adjustment closes and opens it all the way?), give it two pumps of gas all the way to the floor and hit the key.

You have a header and you don't have any carb heater, so it it going to take a long, long time to warm up. you didn't say how long you warmed it up, but if it runs better with the choke on, it may not be warmed up yet.

It would be very unusual to have it run great for a while and then not all of a sudden.

The soot in the tail pipe is normal and not necessarily an indication of a rich condition.

I am having trouble visualizing what you mean when you describe the problem, so paint a brighter picture and that might help.

 

[77mustard40]

The cold start drill is pull the choke all the way out (you did check that the cable adjustment closes and opens it all the way?), give it two pumps of gas all the way to the floor and hit the key.

You have a header and you don't have any carb heater, so it it going to take a long, long time to warm up. you didn't say how long you warmed it up, but if it runs better with the choke on, it may not be warmed up yet.

It would be very unusual to have it run great for a while and then not all of a sudden.

The soot in the tail pipe is normal and not necessarily an indication of a rich condition.

I am having trouble visualizing what you mean when you describe the problem, so paint a brighter picture and that might help.

I won't have time to work with this until this evening, but I did use the full choke, two pump start method this morning and it fired right up. Check

I'm certain I had obtained a normal operating temp last night, temp gage was up to the first mark for a good 10 minutes. Could not figure out why I could not establish a consistent idle without the choke feathered, or why it would stumble with accelerator. I did make some adjustments with the mixture and idle speed screws but plan to "start over" this evening and use my vaccum gage to work on these adjustments (which I did not do last night). I poured thru the FAQ's and other carb adjustment threads and feel I have a better game plan for adjusting idle and idle mixture after doing more homework.

One more question:

Another Hijack, same topic:
mine is a 75 Aisan, just rebuilt. I capped off the brass connection (power valve)at the front of the airhorn. However, When I put manifold vac on it the engine would not run hardly at all. capped off it is fine. So what is wrong with the power valve that it runs so poorly with manifold vac to the power valve port?
This picture shows the open vac connections for the brake booster and the vac gauge, they are connected now, so no unpluged vac connections during the test.

Saw this post last night in an old thread and it was never answered. I have manifold vacuum to the power valve right now but then I read stuff like this and think This question was never answered, any thoughts?

 

[SHUSH]

im still running a webber but have a mark a. rebuilt Aisin in the garage.......taking notes and watching. good luck tonight

 

[Pin_Head]

The temp gauge just measures the water temp; not the carb temp. The fuel needs to completely atomize to burn efficiently and this takes more time if the carb and manifold is cold. Some people run a manifold heater that uses coolant to heat the base of the manifold.

If you have trouble getting it to idle at 650, the idle mixture screw has little effect on idle speed and a flat spot or bogging down off idle can be indications of a lean mixture due to a manifold vacuum leak.

The power valve is an aux main jet that increases the fuel in all circuits and it is open when there is no vacuum. When manifold vacuum is high, the valve is closed. If it runs better with the PV line disconnected, it indicates a lean condition (manifold vacuum leak, wrong jets, etc).

 

[77mustard40]

The power valve is an aux main jet that increases the fuel in all circuits and it is open when there is no vacuum. When manifold vacuum is high, the valve is closed. If it runs better with the PV line disconnected, it indicates a lean condition (manifold vacuum leak, wrong jets, etc).

If I need to look for a vacuum leak what is the best method? I've read about a number of approaches, but I'm hesitant to spray carb cleaner (or other highly combustable items) all over the place. Some day I'd like to get buried in this thing but just not tonight.

 

[tucker74]

If I need to look for a vacuum leak what is the best method? I've read about a number of approaches, but I'm hesitant to spray carb cleaner (or other highly combustable items) all over the place. Some day I'd like to get buried in this thing but just not tonight.

Carb cleaner or brake cleaner work well, they evaporate quickly and will raise the idle noticeably when you spray around a leak. Shouldn't be a big deal but I would probably do it outside the garage There is no open flame, and the vacuum leak only pulls the fluid into the carb where you notice the engine idle jump -

Tucker

 

[Sea Knight]

If I need to look for a vacuum leak what is the best method? I've read about a number of approaches, but I'm hesitant to spray carb cleaner (or other highly combustable items) all over the place. Some day I'd like to get buried in this thing but just not tonight.

You might try mixing a small amount of dish detergent with water, and spray the soapy mixture onto your vacuum lines while looking for air bubbles. Not as effective as the carb cleaner method, but less likelihood of incinerating yourself.

 

[jmdaniel]

Carb cleaner or brake cleaner work well, they evaporate quickly and will raise the idle noticeably when you spray around a leak. Shouldn't be a big deal but I would probably do it outside the garage There is no open flame, and the vacuum leak only pulls the fluid into the carb where you notice the engine idle jump -

Tucker

You might try mixing a small amount of dish detergent with water, and spray the soapy mixture onto your vacuum lines while looking for air bubbles. Not as effective as the carb cleaner method, but less likelihood of incinerating yourself.

Listen to these gents, Kelly; we want you around for awhile!

 

[Pin_Head]

Carb cleaner works fine as long as you don't over do it and make sure that you hold your cigarette in your other hand. An unlit propane torch works well too and may help get the underneath the manifold leaks.

Water is supposed to work too and make the RPM go down. I don't see how you would be able to spot detergent bubbles inside the manifold or tube, but then again I am a pin head.

 

[Sea Knight]

I don't see how you would be able to spot detergent bubbles inside the manifold or tube...

You're correct, of course. You wouldn't be able to see bubbles inside the manifold or vacuum lines.

Here's the way my Dad explained it to me, in the days before spray carb cleaner. The soap-water mixture is already bubbling when sprayed on vacuum lines and connections. You're trying to identify any agitation of the bubbles, including a disappearance of bubbles at the site of leaks. If a soapy area appears to be agitated or even depleted of bubbles, odds are you've isolated the leak. I'm not sayin' this is the best method by any means, but it usually works.

 

[77mustard40]

Ok here is another incomplete update, I'm hardly painting a brighter picture for diagnosing the problem. Setup my vacuum gauge and started the vehicle with the air cleaner installed. After a couple of minutes of full choke I dropped it down to half half choke (still had fast idle fulling engaged) and let it run for 15 minutes hood down to warm the entire engine compartment. Its a balmy 75 in the garage.

Vacuum read 20 under fast idle, tried to adjust fast idle but its a guess without a tach (flog me if you must). Closed choke and pumped the accelerator a couple of times and let idle drop down, vacuum oscillates between 17-18 and idle does not sound smooth. After reading the direction for my fire extinguisher I sprayed carb cleaner all over hell and back. Every connection, manifold surface and abutment to the head was shot, vacuum remained at 17-18 with no noticeable change in idle speed.

Moved on to idle adjustment (guessing at rpm). Set idle speed by sound and then proceeded to work through the mixture adjustment screw a quarter turn at a time listening for idle change and reading the gauge. At roughly 3 to 3.5 turns out idle flattened and vac was closer to 18. Backed off the idle speed about 1/8th of a turn to drop idle back to where I think I started. Repeated this process with no noticeable changes.

The fun part - took it for a drive. All good driving up hill into the throttle, coming home was a different story. In a downhill with no throttle I can not drop the clutch without it wanting to die, had to use momentum a couple of times to restart it (and apply about 1/4 to 1/3 throttle). It is a heavy cough and sputter bringing it back to life when it wants to stall and I engage the clutch to jump the engine (i.e. lots of throttle to blow it out and get it running again). Once back in the garage I cant get it to stall, this has only happened while driving.

I need to get or borrow a tach to make sure I'm setting things correct (have not adjusted the throttle positioner). Not sure I understand Lean Drop Idle after reading the FSM. My truck does not immediately drop to base idle, it stays at a higher idle for several seconds and then starts dropping back. Its almost as this is happening that it goes all the way to nothing.

Overall the truck is good if I'm engaging the throttle, its coasting downhill (no throttle) with the gears engaged and coming up to a stop that makes things interesting.

 

[77mustard40]

Possible Problem

Went out to take a good look at everything again, here is the layout but more importantly here is a possible issue. Second pic shows fuel leaking from the butterfly shaft on the primary after I tried to start it again (two pumps and full choke), did not start. Hard to see in the pic but there was quite a bit of fuel there that ran down and saturated the base of the carb.

Its also worth noting that in my other pics the fuel was just above the half way mark in the sight glass, now only about a third of the way up. I feel like gas is dumping out of this thing somewhere inside.

 

[Pin_Head]

Strange problem, running great up hill and stalling down hill. Sounds like a float problem or a fuel level problem with fuel pouring out of the vent tubes into the carb. Take the top cover off and check that the float swings freely and that the height setting is correct. Also stop when the engine dies down hill and look in the bottom of the manifold for fuel puddle to confirm puking.

The fuel leak after shut off is pretty common in my experience. It comes out of the transition slot runs over the butterfly and leaks into the manifold and out the shaft bushing. It shouldn't siphon because: 1) there is an air vent at the top to prevent siphoning and 2) the idle solenoid is supposed to shut off fuel when off. I'm thinking that it may be capillary action, but I never found out for sure.

 

[77mustard40]

Strange problem, running great up hill and stalling down hill. Sounds like a float problem or a fuel level problem with fuel pouring out of the vent tubes into the carb. Take the top cover off and check that the float swings freely and that the height setting is correct. Also stop when the engine dies down hill and look in the bottom of the manifold for fuel puddle to confirm puking.

The fuel leak after shut off is pretty common in my experience. It comes out of the transition slot runs over the butterfly and leaks into the manifold and out the shaft bushing. It shouldn't siphon because: 1) there is an air vent at the top to prevent siphoning and 2) the idle solenoid is supposed to shut off fuel when off. I'm thinking that it may be capillary action, but I never found out for sure.

Thanks for the advise, this gives me something to focus on tomorrow night. I will report back.

 

[FJ40Jim]

What is the PV hose connected to? It comes off the top of the carb and disappears on the driver side of carb somewhere.

 

[77mustard40]

What is the PV hose connected to? It comes off the top of the carb and disappears on the driver side of carb somewhere.

Jim it's running to the drivers side where i have a tee. The vacuum source is the carb insulator coming directly up to the tee and splitting for the PV on the front and choke break on the side.

After thinking about PinHead's comments and suggestions I'm wondering if I made a mistake in assembling the needle and seat. I believe after watching his video I placed a small rubber ring over the needle when assembling it. Late last night in research mode I did not see that ring depicted in any pictures in the FSM or Haynes manuals, and I don't recall there being one in place during disassembly. maybe I've caused my own misery, but hey I'm on a steep learning curve now.

 

[Rzeppa]

A friend just now pointed me to this thread. Not to hijack, but I have a similar issue in my bone stock 60 where she won't idle when pointed downhill (or coming to a stop when you put in the clutch), but is fine pointed uphill. Runs great at all throttle settings except idle. Solenoid checked and double checked, even hardwired to battery. Carb was rebuilt by PO's mechanic shortly before I bought the rig.

My issue started when I bought the rig and had to get her through smog, had to change the primary jet to a leaner one, then after passing went back to the richer one that was in there before.

It *looks* like I may have low fuel level from the window, but how could I have buggered the float level just by changing the jet through the port on the front of the bowl? Obviously I need to pop the top off the carb (again!!!) and check the float level.

It *looks* like the idle circuit gets its fuel from the top rear corner of the float bowl, thence drawn into the solenoid and then down to the mixture screw, right?

 

[Pin_Head]

There is no small rubber ring that goes over the needle. In the video, I said that the needle had a rubber tip. The ring is probably the one that goes over the nose of the solenoid valve and may be why it is leaking if you left it out or didn't use the right one.

Jeff: How did you end up with the same strange problem? When it stalls, check to see whether the carb is flooded and what the level of fuel is in the bowl. Either way, it sounds like a float problem. As you know, these carbs don't normally mind going up or down hill. Regards.

 

[77mustard40]

There is no small rubber ring that goes over the needle. In the video, I said that the needle had a rubber tip. The ring is probably the one that goes over the nose of the solenoid valve and may be why it is leaking if you left it out or didn't use the right one.

Yep, I remember replaying that section a few times and still had a strange feeling of doubt as I assembled it. Should have posted a question back then and saved a lot of people time. Hope to find it in there and then see if I'm headed the right direction.