Corvair DiagramCorvair Photo
Corvair Center
home forum corvairs calendar links Corvair Podcast
California Corvairs
Clarks Corvair
Clarks Corvair
“CORSA"



Chevy Corvair License Plate
Chevy Corvair Chrome Wheel
Corvair Center Forum :  Corvair Center Phorum The fastest message board... ever.
Corvair Center 
Pages: 12Next
Current Page: 1 of 2
Accelerator pump issue
Posted by: autocomman ()
Date: September 18, 2020 04:56PM

So on the 62 rampside I got it running pretty good and it sat for a few days. When I went to start it back up it wasn't happy. Long story short I found the idle tubes in the Venturi cluster ended up with some junk in them. I clean them out made sure everything in the carburetor was good, reassembled them and now I have an issue when I open the throttle slowly I have no accelerator pump squirt. The only thing I can think of that would cause this would be to check ball in the accelerator pump assembly. It's got new viton cups, and if I snap the throttle there's no problem with squirt. if I open the throttle slow, like if you're moving through a parking lot or going to take off normally, there's no squirt and the thing just bogs. But move the throttles a little faster and they squirt. So something is bleeding off not allowing fuel out of the discharge nozzle with a slow throttle movement. Thoughts? I'll post a vid in a few hours

Options: ReplyQuote
Re: Accelerator pump issue
Posted by: MattNall ()
Date: September 18, 2020 05:36PM

Raise the float level 1/8". Also, remove the bent linkrod and see how it works if the arm goes further down. Some need the arm shortened / new hole drilled to work slowly.

MODERATOR
Sea Mountain, between Charleston Harbor and Coos Bay! SW Oregon Coast
Click HERE for My Website...Click HERE for My TechPages!
..............................110-PG.................................................Webered-Turbo




Edited 1 time(s). Last edit at 09/18/2020 07:18PM by MattNall.

Options: ReplyQuote
Re: Accelerator pump issue
Posted by: autocomman ()
Date: September 18, 2020 07:00PM

Doesnt seem to matter where the lever is. I unhooked it to move it by hand and its the same deal. Move the lever slowly, nothing comes out, moves it a little faster, you get a good strong stream, well 2 streams as there are 2 holes.

I tried bending one carbs rod to have the pump pump more and no difference. All that adjustment will do is give you more pump shot as you stroke from idle to WOT. Otherwise it will only pump till about 1/2? 3/4 throttle before the pump bottoms out.

Accel pump issue

Acell pump issue engine running

Options: ReplyQuote
Re: Accelerator pump issue
Posted by: autocomman ()
Date: September 18, 2020 07:29PM

After srudying the manual and realizing the pump assembly has that check ball ratteling around in there makes me wonder if it would even squirt when moved slowly. The ball in teh assembly moves up when the pump is pushed in, but i cant remember if that part of the assmebly physically pushes the ball in place or if its a flow thing. MOving the pump down in the more forces the ball into place. Can anyone verify that on an accel pump assemnbly?

Otherwise there may be something clogged in the off idle discharge port. Thats reponsible for slow transition from idle to off idle. That may actually be where my issue is. These carbs were pretty nasty when I get em, and they took a lot of cleaning. So I wouldnt be suuprised if there are some little bits just working through now. Still though...any thoughts would be appriciated.

Options: ReplyQuote
Re: Accelerator pump issue
Posted by: RobertC ()
Date: September 19, 2020 12:25AM

Seems you are over thinking the problem. Especially with the accelerator pump linkage adjustments. If the linkage is correctly aligned - the mark on the lever correctly placed - you should be ok.

You state that there was "corrosion" problems with the carbs.

If the walls of the accelerator pump well are not perfectly smooth; there will be problems. If so, the bases need to be replaced with bases in better condition - probably not that easy these days.

Memory is fading, but I do not recall that much accelerator discharge if the linkage is moved slowly. Accelerator pump seems to supply more fuel with a rapid change in throttle position - as it should.

What jets are you using in the carbs? I guess that is related to which carbs of the many primary carbs are on your engine?

For reference: Decades ago, a piece of scale lodged in the idle tube of one carb (110). Performance was poor - until 30 - 35 mph was reached and then the engine ran fine - no longer running on the idle circuit.

Good luck.

Options: ReplyQuote
Re: Accelerator pump issue
Posted by: ken ()
Date: September 19, 2020 04:44AM

Make sure that your gasket between the top and bottom of carb is in good shape and the screws are snug . The gasket seals that area and you cold loose pressure there .

Options: ReplyQuote
Re: Accelerator pump issue
Posted by: JimBrandberg ()
Date: September 19, 2020 05:14AM

There was this thread a while back about the check ball in the bottom of the accelerator pump.
[corvaircenter.com]

Jim Brandberg
Isanti, MN
CorvairRepair.com



Options: ReplyQuote
Re: Accelerator pump issue
Posted by: autocomman ()
Date: September 19, 2020 08:47AM

From that other thread

"The check ball lets fuel bypass the pump when the throttle is moved slowly"

This mostly answers the question. The cars are pretty clean inside. And if there was any amount of junk in the well then I shouldn't have such a good pump shot with the throttle moved a little quicker. Considering the issue with the idle tube plugging up, it's very possible more of that junk is down in the idle tube, which feeds the off idle circuit, which is what's responsible for fueling before the main kicks in. I'll find out today when I hear em down.

Also the top cover gasket is new and it lookee like it was sealing time around the pump area. I know about the lever adjustment and the notch needing to be lined up with the casting mark at 12pm. But it does't matter where you start to move the throttle or pump arm from. If you go slow there is no pump shot, and according to that other thread and how that ball rattles around in there, u less you move the pump down fast enough in the bore, the ball won't move up and seat giving you a pump shot

Options: ReplyQuote
Re: Accelerator pump issue
Posted by: Wagon Master ()
Date: September 19, 2020 09:05AM

You Got It!

Options: ReplyQuote
Re: Accelerator pump issue
Posted by: Brizo ()
Date: September 19, 2020 01:57PM

Some will squirt with slow action and some wont. These days, a lot depends on how smooth the wall of the pump bore is, and if the plunger has an aluminum or steel check ball. If enough gas leaks past the cup, it may not build enough pressure to push the ball up to the seat.

Dan Brizendine, Circle City Corvairs
'64 8door Greenbrier 140 PG. "In beautiful Wanamaker Indiana...with one stop light and 5 pizza shops"

Options: ReplyQuote
Re: Accelerator pump issue
Posted by: autocomman ()
Date: September 19, 2020 06:44PM

Ok, well the ball ddint rattle very well when I checked em today, so a litttle cleaning and they ratteled pretty easily.. Bores are clean and smooth, and i have a good stream, but when the throttle is moved slow I dont have anything. Im not convinced this is the issue.

The off idle slot is also clean. No evidence os junk inside it. Infact everything seems to be open and clean in both carbs.

They have #50 jets which should be correct, but Ive read somewhere #51s seem to be a goto for rebuilds? Not sure how well this would help the off idle circuit. When I had the carbs off I noticed inside the intake port in the heads there is a varnish like substance, its not thin, its almost like there was a coating or something in the heads thats starting to melt of that makes any sense. Its really wierd. Im wondering if that has anything to do with it. If its absorbing fuel and not letting it all pass into the cylinders. I dunno. Gonna have to pull both carbs again and clean it all out as best as I can. Its also possible after driving it a bit that it might clean up by itself, which is prolly what Ill do. See if it smooths out.

Thoughts on the jet? Should I bump it up 1 step to a #51?

Options: ReplyQuote
Re: Accelerator pump issue
Posted by: Wagon Master ()
Date: September 19, 2020 07:06PM

So what is the driveability issue you're trying to cure?

Options: ReplyQuote
Re: Accelerator pump issue
Posted by: autocomman ()
Date: September 19, 2020 07:23PM

Tip in it leans out so much it will stall or want to stall or backfire through the carbs. So if you wanted to just take off normally form a stop, or if your off the throttle and you wanna go back in slowish, or if your trying to manuver in a parking lot it just stumbles. There is a video of what it does in a post above.

I need to recheck the float level and be sure the seat is the correct size. THe carbs were 7023101, but i have to double check that. The tag was still on one fortunatly, and im pretty sure thats what it was. Float level set at 1 3/16 with the gasket installed.

Options: ReplyQuote
Re: Accelerator pump issue
Posted by: RobertC ()
Date: September 19, 2020 09:51PM

Finally looked at your video.

Looks like your chokes are not hooked up. Actually, I do not see hole in the left shroud for the rod that hooks to the choke coil in the bottom of the head.

With a cold engine and no choke the engine will hesitate like it does in your video.

I am not familiar with EM engines, so I do not know the particulars.

Options: ReplyQuote
Re: Accelerator pump issue
Posted by: Brizo ()
Date: September 19, 2020 10:01PM

autocomman Wrote:
-------------------------------------------------------
> Tip in it leans out so much it will stall or want to stall or backfire through the carbs. So if you wanted to just take off normally form a stop, or if your off the throttle and you wanna go back in slowish, or if your trying to manuver in a parking lot it just stumbles. There is a video of what it does in a post above.
>
> I need to recheck the float level and be sure the seat is the correct size. THe carbs were 7023101, but i have to double check that. The tag was still on one fortunatly, and im pretty sure thats what it was. Float level set at 1 3/16 with the gasket installed.

That sounds more like a fuel draw problem from the transition slot or main nozzle, rather than pump squirt. If seen people drive Corvairs for years with no pump function and never knew it. Your cluster number should be 19495. Are all the idle jet / mix passages, restrictor, and air bleeds clear, and cluster not warped?

Dan Brizendine, Circle City Corvairs
'64 8door Greenbrier 140 PG. "In beautiful Wanamaker Indiana...with one stop light and 5 pizza shops"



Edited 1 time(s). Last edit at 09/19/2020 10:03PM by Brizo.

Options: ReplyQuote
Re: Accelerator pump issue
Posted by: Marco_a_p ()
Date: September 19, 2020 10:31PM

Is this affecting one car or both? I had an experience with GM Mono jet on a 220Ci straight 6 out of a 69 camaro that would not get a slow shot. Rebuilt, cleaned etc. Studied it intensely, and figured that the Accel pump well was worn out.

Got luck and found an NOS Mono Jet Base/Body. Swapped everything over and the accel shot was restored. It seems that the cup would flare out when a quick throttle move was made, but when it was slower, it would not flare out enough to make a seal that would allow the fule to flow around the cup.

Just before I transferred the air horn and the rest of the parts, I compared the accel wells and it was obvious with them side by side that the problematic carb base was larger in diameter than the NOS one.

Just and observation. Seems to me that is the issue you are encountering.

Marco
A 2nd Gen Monza Wagon, a 2nd Gen GB 8door, a 2nd Gen (61's were 1st Gen) R/s and a 62nd Gen Turbo coupe..

Hanging out with the scorpions, king snakes, road runners, coyotes and quails In the southern desert of the silver state
Mesquite NV 89024

Options: ReplyQuote
Re: Accelerator pump issue
Posted by: autocomman ()
Date: September 20, 2020 12:26AM

It's both carbs, they behave identically. I'd love to see how many actually squirt at a slow speed. The way the pump assembly is designed it has to be pushed into the well at a certain rate for the check ball to seat. The monojet didn't have that type of check ball to allow the pump well to refill. I think it had its own refill passage from the bowl.



Edited 1 time(s). Last edit at 09/20/2020 12:28AM by autocomman.

Options: ReplyQuote
Re: Accelerator pump issue
Posted by: Wagon Master ()
Date: September 20, 2020 06:41AM

So this whole condition started after finding and cleaning junk out of the carbs.? It was running perfect before that?
A viewed oddity. When trying to give it gas both choke pull-offs cycle back and forth like a dist. vacuum advance.
Don't ever recall that, but then I've never run pull-offs with no choke thermostats. It almost acts like an intake valve(s) is not sealing and it's bleeding combustion back into the intake logs. Plus the "barking" "spitting" back out the carb. throat acts more like a leaking intake/flipped valve seat than a lean pop.
Just for the sake of ruling things out, do a compression check and report back.


'29 Ford Model A Tudor (Great Grandfather bought new)
'61 700 Lakewood 110 4 speed
'69 Monza Convert. 140 Auto.
'70 Dodge Challenger R/T 440 4 speed

Been aircooled since 1973
Northwest Ohio

Options: ReplyQuote
Re: Accelerator pump issue
Posted by: autocomman ()
Date: September 20, 2020 09:38AM

This is not an old motor. New pistons cylinders, .060 over. Heads are NOS. Compression is 150 across the board. It's a lean backfire. The pull off are moving like that cause the rom gets so low when it bogs your loosing vacuum.

This motor I just got running a few weeks ago, and I only drove it for the first time this week. Its always done this. I know I said I wasn't sure if it did this before but it actually has. I was dealing with other issues after I got the engine running I don't think I really payed attention to this issue. (Been a lot going on over thr last few weeks around this project). Now that I'm getting to the end of it all and have had time to think I realize it's always done this. There are choke thermostats, they just sent hooked up cause I'm waiting on new clips.

The throttle shafts are a little loose on the carbs. Not enough I don't think to be a problem, I've definitely seen much worse shafts. Either way, I've ordered #51 jets and new shafts. I'm going to. Change those parts out and we will see what happens.

Options: ReplyQuote
Re: Accelerator pump issue
Posted by: Wagon Master ()
Date: September 20, 2020 10:25AM

autocomman Wrote:
-------------------------------------------------------
Compression is 150 across the board. It's a lean backfire. The pull off are moving like that cause the rom gets so low when it bogs your loosing vacuum.


when was the compression check done? Right after you got it running, or was it the last thing you did?

I'm still leaning towards the lifters have finally pumped up and now the valves are a little too tight.

Just stick the choke thermostat rods in the holes without the clips. Unscrew the rods to where the chokes don't completely open even when warm, to rule out this lean condition. It will make the mixture richer under all phases, like it has bigger jets.

Options: ReplyQuote
Pages: 12Next
Current Page: 1 of 2


Sorry, only registered users may post in this forum.
This forum powered by Phorum.