New carb, still stalling when hot. FJ60 rebuild fun! (2 Viewers)

[mattressking]

@mattressking Don't forget that in addition to the static timing bump the HAC also leans out the mixture under three different conditions. That isn't something that the idle mixture & speed screws can adjust for during actual driving. There is definitely a need for a little more air up here at elevation so I've kept my stock carb and HAC. Under about 80% throttle the HAC is kicking way to much air into the mixture though, so I have a 25cc VCV on that vac hose to kind of neck down the airflow a bit. At 80% throttle cruise the A:F was pegged lean before (18+) and is now about 16.

Fwiw My engine is pretty tight and the emissions systems have all been verified, and I sit at about 17inHg. They say there's appx 1inHg loss for every 1000' elevation, so I feel like I'm fairly on track that. Maybe that data point helps somebody.

Correct to assume 1inHg for every 1k, that's the usual standard for carbureted engines.

You're absolutely right on leaning out, you're right that I forgot to mention - that said, I never use HAC and just bump timing manually since most folks don't have a functioning advance unit.

I'm tempted to dyno a desmogged 2F with stock jetting at sea level and see how lean it truly is with 91.

 

[CruiserTrash]

Correct to assume 1inHg for every 1k, that's the usual standard for carbureted engines.

You're absolutely right on leaning out, you're right that I forgot to mention - that said, I never use HAC and just bump timing manually since most folks don't have a functioning advance unit.

I'm tempted to dyno a desmogged 2F with stock jetting at sea level and see how lean it truly is with 91.

I would love some A:F numbers from a smogged truck at sea level. That would give me a baseline to compare it to. I'd also love A:F numbers from a desmogged truck at sea level, but desmogs are all over the place and a lot of them are a total s***show. The thing that would interest me the most would be a world market 2F I guess.

 

[Spike Strip]

I'm at 700 ft and fully smog'd and functional. My A/F meter (analog face gauge) bounces between 14:1 to just under 15:1 which is right where I want it. Theoretically, a bit richer equals more power, but I'm light on the skinny pedal with 33s and the H55f, and it seems to run very well as is - plus, I went with what gave me the highest vacuum reading at 650 rpm idle. I have an in-cab vac gauge I monitor constantly. Also, the smog police do run road-side inspections here, though they are 'voluntary' and are 'supposed' to just be a blind measure of compliance, but ....

FWIW, anyone who is thinking of installing an A/F wideband meter, go digital. I made a mistake thinking the analog gauge would be less distracting at night.

 

[CruiserTrash]

@Spike Strip I run vac and A:F gauges in the cab too. It's taught me a lot about how these trucks run and what the carb is doing. My A:F is a digital Autometer wideband unit with an "analog style" gauge. Out of curiosity if you're going down the highway at about 80% throttle (first barrel almost all the way open, second barrel still closed), what do you read?

 

[Spike Strip]

IIRC, It will bounce between 16 to 17 or so, if not under load and just cruising on slow flat highway, partial throttle. I don't go 70 mph. I'm low and slow with a 40 year old brick with crap steering and the Prius' and Tesla's hate me

But to be honest, it's not something I typically pay attention to. I'll try and check it tomorrow or so.

 

[Otose]

12.5 is too low.

Is vacuum gauge needle steady at idle? Either condition of engine is very poor or you have a hella vacuum leak.

Mattressking beat me to it: you can't use HAC with that carb - it doesn't have the ports like the stock Aisan carb. If you want to use HAC for going above 4K feet, you'll need to go back to the stock carb.

Thanks for the support so far... much appreciated! I am working between a few different projects at the moment, and whenever you ask something, I either have to go into town to buy another tool or learn how to do something! Have been trying to get a base timing reading with my old school timing light without much success. Cannot seem to find the markings on the flywheel, so will have to get under it once the other car is far enough along and pull off the cover.
Just to clear up some confusion on the carb, you may be mixing me up with the OP... I do have an Aisin original carb that also has the choke breaker - and I would like to make it to the "valley" at some point with this LC, so will be interested in the HAC functionality once the vacuum issues are sorted.
Will update again as soon as I can get more time on it. Thanks again, and if any pointers on the timing, please let me know. Have found some good threads here, but always looking for any help!

Rob

 

[Spike Strip]

Thanks for the support so far... much appreciated! I am working between a few different projects at the moment, and whenever you ask something, I either have to go into town to buy another tool or learn how to do something! Have been trying to get a base timing reading with my old school timing light without much success. Cannot seem to find the markings on the flywheel, so will have to get under it once the other car is far enough along and pull off the cover.
Just to clear up some confusion on the carb, you may be mixing me up with the OP... I do have an Aisin original carb that also has the choke breaker - and I would like to make it to the "valley" at some point with this LC, so will be interested in the HAC functionality once the vacuum issues are sorted.
Will update again as soon as I can get more time on it. Thanks again, and if any pointers on the timing, please let me know. Have found some good threads here, but always looking for any help!

Rob

You're correct, I did confuse with OP picture.

If you have stock carb, then absolutely HAC will work. You will need to test the HAC valve. Though not common, they do fail.

FWIW, I use this timing light (about $100 at Walmart). Very bright flash and has a nifty feature of advance timing so there's no guessing where you're setting the timing advance. Has dwell, RPM, everything you'll need. Quite a few YT videos on how to use properly the advance and other features. Good luck!

5568 Pro Digital Timing Light

The Pro Digital Timing Light 5568A by Innova is a precise and reliable tool for engine timing adjustments. Perfect for automotive enthusiasts and professionals.

www.innova.com

 

[Otose]

You're correct, I did confuse with OP picture.

If you have stock carb, then absolutely HAC will work. You will need to test the HAC valve. Though not common, they do fail.

FWIW, I use this timing light (about $100 at Walmart). Very bright flash and has a nifty feature of advance timing so there's no guessing where you're setting the timing advance. Has dwell, RPM, everything you'll need. Quite a few YT videos on how to use properly the advance and other features. Good luck!

5568 Pro Digital Timing Light

The Pro Digital Timing Light 5568A by Innova is a precise and reliable tool for engine timing adjustments. Perfect for automotive enthusiasts and professionals.

www.innova.com

Alright, back at it after getting the Innova light delivered and returned from an event with another car.
Trying to answer the question from @mattressking earlier.... not sure if I am getting this right, but with the new light with the advance figure and the lines marked on the flywheel, I am showing 16 degrees of advance at 750rpm. This is the reading with the flywheel line aligning with the timing indicator. With the vacuum line pulled off of the DUI dizzy, it doesn't run very smooth, but again I am only getting about 12in of vacuum.
@Spike Strip the reading on the vacuum gauge is solid, does not move around at all.
Found a picture I had of the slightly battered "Vacuum Hose Information" label and have been going through it to see if I had any errors in routing. The bottom of the HAC valve was separated from the unit, so put that back together and got a brief improvement up to about 14", but it seemed to settle back down to 12 after running for a bit.
With the new DUI unit, some of the lines have nowhere to go, so I have plugged them.
Any thoughts based on the latest status? If nothing else, I am learning a few things along the way.

 

[OSS]

16° is a lot of advance.
Use the vacuum schematic in the emissions FSM. It’s way better than what you’re using.

Pdf page attached here

 

[Otose]

16° is a lot of advance.
Use the vacuum schematic in the emissions FSM. It’s way better than what you’re using.

Pdf page attached here

That's much easier to read - thanks!

 

[Pighead]

16° is a lot of advance.

I guess it's more than the book says but I'm running 22* base timing. Was running 33* at 6k feet, now at 3k feet.
Advance your timing a bit and see what happens

 

[BlackCat]

I guess it's more than the book says but I'm running 22* base timing. Was running 33* at 6k feet, now at 3k feet.
Advance your timing a bit and see what happens

View attachment 3488367

Just to clarify, your static timing is set at over 3x’s the factory 7°BTDC?
If so, I highly recommend not doing that, lol.
Could you even get the timing at 33° with the distributor installed correctly or did it need to be a tooth off? That’s what, nearly 60° of total timing?

 

[Pighead]

Just to clarify, your static timing is set at over 3x’s the factory 7°BTDC?
If so, I highly recommend not doing that, lol.
Could you even get the timing at 33° with the distributor installed correctly or did it need to be a tooth off? That’s what, nearly 60° of total timing?

yup. you know that the BB disappears after 15* or so. back before digital timing lights I would time by vacuum gauge. Advance to best vac then back off just a hair. if it pings, back off another hair. so I had no idea what my static timing was in numbers, that was just where it ran best.
Then I got a new timing light, found I was at 33* BTDC. that seemed a bit much even to me. ended up replacing the leaky double diaphragm advance mechanism with a new single diaphragm unit (I can only power 1 diaphragm anyway), fiddled with the springs a bit and found I could drop the advance to 22*, still pull 15" of vacuum, and keep it drivable. any less and it's just too sluggish. The engine is getting old, I built this one in 2004, been promising it a valve job for 10 years.
sure, this engine isn't stock, but it's not that far off. and the FSM does not always have our best interests in mind. I have found that the further these rigs get from the factory, the less the FSM matters.
The distributor is installed correctly in that it turns the oil pump and rotor points to #4 sparking plug at TDC and I am using the stock hold down.

 

[65swb45]

Alright, back at it after getting the Innova light delivered and returned from an event with another car.
Trying to answer the question from @mattressking earlier.... not sure if I am getting this right, but with the new light with the advance figure and the lines marked on the flywheel, I am showing 16 degrees of advance at 750rpm. This is the reading with the flywheel line aligning with the timing indicator. With the vacuum line pulled off of the DUI dizzy, it doesn't run very smooth, but again I am only getting about 12in of vacuum.
@Spike Strip the reading on the vacuum gauge is solid, does not move around at all.
Found a picture I had of the slightly battered "Vacuum Hose Information" label and have been going through it to see if I had any errors in routing. The bottom of the HAC valve was separated from the unit, so put that back together and got a brief improvement up to about 14", but it seemed to settle back down to 12 after running for a bit.
With the new DUI unit, some of the lines have nowhere to go, so I have plugged them.
Any thoughts based on the latest status? If nothing else, I am learning a few things along the way.View attachment 3488234

1. If you’re running a Chi-com carb and a DUI, why are you messing with a HAC in the first place?
2. If your vacuum drops when you disconnect the hose from the dizzy at idle, it was/is not routed correctly in the first place. The correct source for the advancer has no vacuum at idle.

 

[Otose]

1. If you’re running a Chi-com carb and a DUI, why are you messing with a HAC in the first place?
2. If your vacuum drops when you disconnect the hose from the dizzy at idle, it was/is not routed correctly in the first place. The correct source for the advancer has no vacuum at idle.

1. I am running the original carb with the DUI. I was initially looking to understand what the original poster had done and that has caused some confusion on my setup. I basically have an original California emission setup with the addition of the DUI unit as a potential means to improve the hot stall condition I have, which tends to only happen after about an hour of running, and the truck is generally undriveable at that point. I am at ~ 4500'
2. The factory dizzy that I replaced had two lines to it, the DUI only has one. In my photo above of the routing diagram, I have the straight line off the hard pipe connected to the DUI unit advancer, I have plugged the line with the blue VSV. I could swap those, but I think the blue VSV only flows "back"

Went through the rest of the lines as well yesterday, and did not find anything major that changed the vacuum. Do seem to have some oil around the base of the PVC valve and grommet, so a new one is on it's way.

 

[Otose]

1. I am running the original carb with the DUI. I was initially looking to understand what the original poster had done and that has caused some confusion on my setup. I basically have an original California emission setup with the addition of the DUI unit as a potential means to improve the hot stall condition I have, which tends to only happen after about an hour of running, and the truck is generally undriveable at that point. I am at ~ 4500'
2. The factory dizzy that I replaced had two lines to it, the DUI only has one. In my photo above of the routing diagram, I have the straight line off the hard pipe connected to the DUI unit advancer, I have plugged the line with the blue VSV. I could swap those, but I think the blue VSV only flows "back"

Went through the rest of the lines as well yesterday, and did not find anything major that changed the vacuum. Do seem to have some oil around the base of the PVC valve and grommet, so a new one is on it's way.

So, new PVC valve (and grommet - old one was petrified)... and no change to vacuum levels. Any thoughts on where to go next??

 

[65swb45]

So, new PVC valve (and grommet - old one was petrified)... and no change to vacuum levels. Any thoughts on where to go next??

Disconnect the EGR valve and brake booster from the engine, cap off both, and run another vacuum test.

 

[Otose]

Disconnect the EGR valve and brake booster from the engine, cap off both, and run another vacuum test.

With Brake booster disconnected at the engine and plugged, EGR valve disconnected (lines Q and darker line from the diagram out of the bottom of the EGR-VM) and plugged, no noticeable difference. Full choke, runs about 9 in, after a few minutes of warm up, choke in it drops to about 8 in. Will include the diagram again that I am using, a bit hard to read, but it does match the truck. Vacuum readings are steady, not jumping around.

 

[Otose]

With Brake booster disconnected at the engine and plugged, EGR valve disconnected (lines Q and darker line from the diagram out of the bottom of the EGR-VM) and plugged, no noticeable difference. Full choke, runs about 9 in, after a few minutes of warm up, choke in it drops to about 8 in. Will include the diagram again that I am using, a bit hard to read, but it does match the truck. Vacuum readings are steady, not jumping around.

Meant to attach this image....

 

[CruiserTrash]

Meant to attach this image....

View attachment 3494628

This will be much better:

Emissions Manual