Going Aisin-details, details, details

[77mustard40]

And finally time for mounting up



and checking all the connections and then the moment of truth



And...no change, still the exact same symptoms. Engine idle speed randomly moves up and down, vacuum following suit between 18 and 14. So here is where I have ended my day.



It has to be something in the carb, so she is in pieces and I'm getting ready to dive into a good bottle of wine. Time for creative thinking.

 

[Sea Knight]

...I'm getting ready to dive into a good bottle of wine.

That's usually the recommended fix when all else fails...and I'm about to join you.

 

[tucker74]

The more I think about it, it's got to be that carb man. No way you could rebuild it wrong or have a vacuum leak that many times

Tucker

 

[jmdaniel]

Kelly, put Dave's carb on, and give it a go! You're working this down to the (literally) thousandths of an inch, and do you really think these things are put together with that kind of precision?

 

[77mustard40]

Kelly, put Dave's carb on, and give it a go! You're working this down to the (literally) thousandths of an inch, and do you really think these things are put together with that kind of precision?

I think a second carb has to be in the cards.

In the meantime I have re-dipped the base and blown it clean. The bowl is on the overnight boil and I will blow it out tomorrow, I'm wondering if something isn't up with the idle circuit somewhere.

 

[davegonz]

Kelly, you just don't give up.

Come on over and pull the one on my 40 and see if it makes a difference. I'll be working in the garage all day tomorrow.

 

[77mustard40]

Kelly, you just don't give up.

Come on over and pull the one on my 40 and see if it makes a difference. I'll be working in the garage all day tomorrow.

I will give you a call after the lunch hour, thanks Dave.

 

[77mustard40]

Weird Results

I re-cleared the carb components this morning after the dip with spray and compressed air, everything was clear. I reassembled with the only change being to the secondary jet, went with 180 vs 220. I know it will have nothing to do with idle but was burning a lot of fuel and response was heavy before this latest round.

Called Davegonz and while waiting for a call back I finished putting it all back together. Was almost complete when he called so I decided to just finish and see if I could drive it over for the carb swap.

Fired her up with familiar results; vacuum all over the map with idle as long as no choke was applied.

MOMENT OF TRUTH:

1. when I went to pull my vacuum gage off the brake booster line and was expecting it to die or die trying to die, the idle actually jumped up. This was the first time I had run it with an intentional large vacuum leak, and it ran at a higher RPM albeit it was rough.

2. next I started messing with the vacuum lines to the carb. I have been applying vacuum to the PV and TP either from the manifold or the gas filter that I picked up recently. Again, while it was running, I pulled the line off the PV and again the idle improved, this time it was both smoother and higher. Next I put my thumb over the PV port and it idled up a little more so I capped it and simply ran a single line from the manifold to the TP for vacuum there.

3. I adjusted the idle with everything hooked up wrong and although I cant get a perfectly smooth idle, it is 80-90% better. Next I jumped in and ran over to Davegoz's pad and it drove better than it has at anytime with this carb on. Nice strong pull through the entire power band, even smooth transition off idle.

SO I NEED HELP FROM THOSE WHO ARE A LOT SMARTER THAN ME; WHY WOULD PERFORMANCE IMPROVE WITH THE PV BLOCKED? I know this is not supposed to be the correct way to hook up the carb? Here is what I think I remember being in her:

Main jet 141
Secondary 180
Power 90
Primary Slow 50
2nd Slow 85

 

[FJ40Jim]

To save me re-reading the whole thread, what year and PN is the carb?

 

[77mustard40]

To save me re-reading the whole thread, what year and PN is the carb?

Jim, carb manufacture date was 12/24/75, picked it up on Mud as a core, looks non-USA to the beginner (no AAP). The PN off the vacuum secondary is 21100-61032, I found this looking at pics on my phone since I'm at the office. If this is wrong I will have to find the PN this evening. Thanks for your interest, I'd like to PP you for your time so just let me know.

Sent from my iPhone using IH8MUD

 

[FJ40Jim]

The parts are all USA (EGR tube, temp sensor, external PV...)
It is a 1976, so no AAP.

Is there vacuum at the PV port on the carb? If yes, then I've rebuilt it previously.

The pri slow jet is too small, preventing enough fuel for a good idle.
The pri main is too small.

 

[77mustard40]

Is there vacuum at the PV port on the carb? If yes, then I've rebuilt it previously.

The pri slow jet is too small, preventing enough fuel for a good idle.
The pri main is too small.

I will check carefully to see if there is vacuum at the PV, it sure tried to idle better when I blocked it.

I have the old primary slow jet that I think is a 65, it needs to be cleaned up but will that be large enough?

I have main jets of 141, 150, 180 & 220 that came with my rebuild kit, can't remember the old primary jet size but have that as well. Will 150 be enough or should I go 180 P & 220 S?

Sent from my iPhone using IH8MUD

 

[FJ40Jim]

Try the 65 & 150 in the primary side.

220 or 230 on the sec. main.

 

[MoCoNative]

Does the throttle positioner even work. Do you have a vacum pump, or even sucking on the tube. Does it move the rod and does it stay for as long as you suck on it and keep vacum. The diaphram in that can crack, could be a vacum leak there.

Looks like Jim has given you some good advice.

 

[77mustard40]

Does the throttle positioner even work. Do you have a vacum pump, or even sucking on the tube. Does it move the rod and does it stay for as long as you suck on it and keep vacum. The diaphram in that can crack, could be a vacum leak there

yep TP works with it hooked to manifold vacuum, but if I find vacuum at the PV I will re-route the line from PV to TP per a Jim C'd carb I saw in an older thread. Also going to pop the top to change the primary jets. Hopefully closing in on this beast.

Sent from my iPhone using IH8MUD

 

[Pin_Head]

WHY WOULD PERFORMANCE IMPROVE WITH THE PV BLOCKED? I know this is not supposed to be the correct way to hook up the carb?

The power valve is open when there is no or low vacuum on its actuator line. This addes extra fuel essentially providing a larger jet size. This points to a lack of idle fuel or lean mixture as the culptit, as opening the PV make it run better.

 

[77mustard40]

Is there vacuum at the PV port on the carb? If yes, then I've rebuilt it previously.

I can say the carb has not been blessed by Jim C, no vacuum at the PV. I have changed the main jets to 150 & 220. The original slow jet that is a 65 was clogged so it's in the carb dip to see if I can unclog it.

 

[77mustard40]

Houston, we have idle! Cleaning up the old 65 primary slow jet and combined with manifold vacuum to the PV and TP allowed me to set an idle and adjust mixture screw. Driving it was smooth albeit with less pull across the power band as yesterday's bastardization. I'm going to continue to experiment with the main jets as it seems pretty rich right now, may retry the 144 - 180 main combo to see what happens.

Thanks to the guys who hung in with me through all this and kept the expertise coming; it's been one heck of an exercise and I'm learning a whole lot about my truck.

 

[jmdaniel]

Thank goodness! This thread was getting as long as Lee's, but with no Zinger Girls!

 

[Sea Knight]

Thank goodness! This thread was getting as long as Lee's, but with no Zinger Girls!

That's about to change. Now that Kelly has it runnin', he'll have hordes of wimmens chasin' him down the street.