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1963 Spyder Turbo - Won’t hold idle when warm
Date: September 24, 2022 05:08PM

My ‘63 Monza Spyder starts well, runs well and idles most of the time. However, twice I’ve had this problem: after driving for long enough that the engine is warm, I will park the car and run a few errands. When I return to the car (let’s say 30-60 mins later), it may start but it won’t idle. Once it konks out it is hard to start again. If I manually turn the choke to very rich (allowing the choke to close) I can get it started. While keeping the revs high, I turn the choke back to the normal position. If I take my foot off the gas, the revs will fall below idle speed and will konk out again. If I wait a few hours for the car to completely cool it will start and idle fine again. Note that even though the car idles normally at about 500 RPM, today I had the idle turned up to about 1000 RMP. Not sure if that would make any difference. I have the original YH carb in there which I’ve rebuilt a couple of times. Any thoughts as to why it won’t hold the idle? Thanks.



Edited 1 time(s). Last edit at 09/27/2022 09:47PM by 1966-Corsa-GT-180.

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Re: Won’t hold idle when warm
Posted by: RobertC ()
Date: September 24, 2022 05:34PM

Know nothing about YH carbs, but

There are "100's" of threads on this site on this subject.

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Re: Won’t hold idle when warm
Posted by: steve c goodman ()
Date: September 24, 2022 06:08PM

Do you have an electric fuel pump or mechanical?

best wishes, Steve
Rear Engine Spec. Inc. Golden, Colo.

1962 spyder 3.0L turbo---1965 Crown V8
1967 monza 110/4---1968 monza 110/4
1971 amante gt 110/4
CORSA/RMC/PPCC/V8 Registry

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Re: Won’t hold idle when warm
Date: September 24, 2022 08:57PM

Electric and pretty near the gas tank. I don’t think it’s vapor lock if that’s what you’re suggesting since if I close the choke it does start which confirms there’s liquid fuel available. I’m suspecting that with the choke open and the main butterfly slightly open, there’s not enough vacuum on the idle circuit to pull fuel through. If that theory is correct I can’t explain why the idle circuit works just fine if I hadn’t stopped for an hour. Perhaps it’s possible that after stopping for an hour the coil and the engine simply cool to different temperatures and they’re out of sync for a bit. Would love to hear an expert’s opinion though!

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Re: Won’t hold idle when warm
Posted by: playerpage ()
Date: September 25, 2022 06:31AM

Vapor lock is not possible with an electric pump. Lock is caused by heat soak, and the electric pumps are never going to get that hot, especially since they are always so far from the engine.

Some very likely scenarios are that, 1) The pump is too high and is flooding the carb. Our YH women (temperamental, lovely, and worth it) can only handle about 2.5 psi of gas. Any more than that, and you can easily overwhelm the bowl.

2) The electric pump is clogged, causing it to send fuel in spurts, if at all. The closer it is to the tank, the more likely it is to get crap coming at it. Perfectly fine to be near the tank if the tank is new, but an old tank used after a long sit will need time to clear out if you don't remove and clean it yourself. I went through 6 pumps in a single year before my pump could be trusted with that crap. It was worth it to me not to replace the tank though. You can try replacing the fuel filter, but if you're only using the filter the pump comes with, it is gonna be clogged, and the whole pump may be ruined.

3) When you do replace the filter, whether or not you replace the pump, use this one. It has a built in fuel return, another thing the YH needs and may not have on an electric pump.

ACDelco Gold GF423 Fuel Filter

4) YH carb means Turbo engine. Turbo engine means idling at 24 advanced. Are you there?

5) even with the right PSI of pump--install a fuel regulator if you can't find a pump at the proper pressure--the screws may be adjusted wrong and flooding you. Baseline adjustment should be just barely seating the idle screw and then adjusting it back one and a half turns. The mixture screw should be just barely seated, and then turned back 3/4 of a turn. Proceed to fiddle.

6) Check your choke. It's never one and done with the choke. Try a lean setting try a rich setting, and be prepared to adjust again depending on the weather conditions you find yourself in.

Given the complex nature of the deceptively simple YH carburetor, this is by no means an exhaustive list of what could be going wrong, but these are great basics. I recommend the Bob Helt YH carburetor book. Clark sells it, Amazon sells it, your best friend in the Corvair world sells it, just get it somewhere.

7) What you describe about it being off for an hour and then unable to start it, sounds very much like a hot carburetor issue. The carburetor simply gets heat soaked, and will have a hard time starting. It's kind of a design flaw. All of the above techniques will mitigate this, but it's going to happen to you once in a while with a YH. Improving your cooling by making sure that you are timing advanced to the proper degree, checking the engine is properly sealed in all the spots of the shrouds, and maybe even investing in a Nash Fan, will help to keep this from happening. Unless of course you are a leadfoot who loves to run his boost!

Happy motoring! It may not sound like it but I continue to believe In my own carburetor.

Eric C. Player
Fargo, North Dakota
MEMBER: CORSA National, Central Coast CORSA, South Coast CORSA, Vintage CORSA, Sfba CORSA, and Great Plains Corvair Club.
THEN: 1965 Monza 110, Canary Yellow - 1965 Corsa 180 Turbo, Red - 1966 Monza 110, Purple - 1967 Monza 140, Red - 1966 500 110, Black; nicknamed "Shadow" - 1965 Monza 110, Camaro Yellow; nicknamed "Silver"
NOW: 1966 Corsa 180 Turbo, Blue; nicknamed "Bluvair"
---------------------------------------
"He cautioned me not to take notes. It would not have helped if I had, as he would start a paragraph with, 'It is therefore obvious. . .'
and go on from there to matters which may have been obvious to him and God but to no one else."
-- Robert A. Heinlein, character of Daniel B. Davis, 'The Door Into Summer.'



Edited 5 time(s). Last edit at 09/27/2022 09:44PM by 1966-Corsa-GT-180.

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Re: Won’t hold idle when warm
Posted by: playerpage ()
Date: September 25, 2022 06:44AM

Might help me to more carefully read your original post.

Point 1a: You should know that the factory setting for the turbo carburetor is at 850 rpm. 500 is way too low, and 1,000 isn't that big of a deal. See point 5 regarding adjusting the idle.

Eric C. Player
Fargo, North Dakota
MEMBER: CORSA National, Central Coast CORSA, South Coast CORSA, Vintage CORSA, Sfba CORSA, and Great Plains Corvair Club.
THEN: 1965 Monza 110, Canary Yellow - 1965 Corsa 180 Turbo, Red - 1966 Monza 110, Purple - 1967 Monza 140, Red - 1966 500 110, Black; nicknamed "Shadow" - 1965 Monza 110, Camaro Yellow; nicknamed "Silver"
NOW: 1966 Corsa 180 Turbo, Blue; nicknamed "Bluvair"
---------------------------------------
"He cautioned me not to take notes. It would not have helped if I had, as he would start a paragraph with, 'It is therefore obvious. . .'
and go on from there to matters which may have been obvious to him and God but to no one else."
-- Robert A. Heinlein, character of Daniel B. Davis, 'The Door Into Summer.'

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Re: Won’t hold idle when warm
Posted by: steve c goodman ()
Date: September 25, 2022 07:45AM

Instead of being vapor locked it can be the opposite.

The following was printed in EXCELLENCE magazine (a Porsche magazine) probably 15 years ago and I have found it true in many cases: The thought is that oxygenation properties in todays fuels to deal with emissions will evaporate by the heat soaking. The liquid fuel is left in the intake system however and when starting a hot engine it must be treated as if flooded. Thus foot to the floor and no pumping because the engine has fuel already it needs air to mix with it.

I always install a toggle switch on fuel pump for turbo cars so the pump can be turned on/off by choice. When starting hot first turn off the pump then foot to the floor and start engine. After running engine for 30 seconds or so then turn on fuel pump but continue to keep engine running at a higher rpm. Engine will settle down usually within a couple of minutes and act normal then.

Try this with yours and see if it helps. It certainly worked on my car as well as several others around here. even several non-turbo cars have improved starting by just treating the engine as if it is flooded too.

As I said it is not my ideaa but something that certainly works in some cases.

best wishes, Steve
Rear Engine Spec. Inc. Golden, Colo.

1962 spyder 3.0L turbo---1965 Crown V8
1967 monza 110/4---1968 monza 110/4
1971 amante gt 110/4
CORSA/RMC/PPCC/V8 Registry

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Re: Won’t hold idle when warm
Posted by: playerpage ()
Date: September 25, 2022 08:58AM

I like that "treat it like its flooded" technique. I sort of do that too. (I have a switch on the dash for my pump.) But not quite that way. Gonna adopt it.

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Re: Won’t hold idle when warm
Date: September 25, 2022 07:51PM

Steve, thanks for the advice to treat it like it’s flooded. Why the fuel pump switch though? Isn’t the pump just filling the well? It’ll stop filling once the foot raises. How does the toggle stop further flooding?

Eric, appreciate your comments. My responses:

1. The pump is under the chassis so it shouldn’t be too high, physically. I think the pressure is ok because the float appears to operate and any extra gas gets routed back to the tank.

1a. It’s weird, I had it set to 850 RPMs per spec and for some reason it would occasionally drop down to 450-500 RPMs at a stop sign and later on it would settle again at 850. Not sure why that fluctuation. I was fiddling with the throttle linkage this afternoon and found that sometimes the spring doesn’t pull the linkage as far closed as it should. That might be the cause of the fluctuation.

2. Gas tank is new.

3. I replaced the filter with one with a return.

4. Yes, idle timing is at 24 degrees advanced.

5. The mixture and idle speed screws are set as Bob Helt recommends.

6. I love Helt’s book and adjust the choke accordingly.

7. I will take a look at any sources of unnecessary heat warming the engine compartment.

Thank you all very much!



Edited 1 time(s). Last edit at 09/27/2022 09:46PM by 1966-Corsa-GT-180.

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Re: Won’t hold idle when warm
Posted by: playerpage ()
Date: September 26, 2022 04:56AM

The spring can be a pain. Roger Parent makes a specialized linkage to help smoothness of operation, maybe it can help you. I got my throttle adjustment bolt from him. I also went out and bought a slightly stiffer spring than stock.

Good luck!

And regarding a pump switch:

Keep in mind, the mechanical fuel pump only ran when the engine did. The motion of the engine moves the pump. With an electric, once everything shuts down it's still running if it's on a circuit that doesn't kill as soon as the engine does, and I don't know any circuit that does that. (It shuts down when the power turns off, not when the engine does.)

It's that pumping out of sync with the engine that an electric switch prevents. There are guys who install switches to automatically shut off in the case of a crash as well.

Eric C. Player
Fargo, North Dakota
MEMBER: CORSA National, Central Coast CORSA, South Coast CORSA, Vintage CORSA, Sfba CORSA, and Great Plains Corvair Club.
THEN: 1965 Monza 110, Canary Yellow - 1965 Corsa 180 Turbo, Red - 1966 Monza 110, Purple - 1967 Monza 140, Red - 1966 500 110, Black; nicknamed "Shadow" - 1965 Monza 110, Camaro Yellow; nicknamed "Silver"
NOW: 1966 Corsa 180 Turbo, Blue; nicknamed "Bluvair"
---------------------------------------
"He cautioned me not to take notes. It would not have helped if I had, as he would start a paragraph with, 'It is therefore obvious. . .'
and go on from there to matters which may have been obvious to him and God but to no one else."
-- Robert A. Heinlein, character of Daniel B. Davis, 'The Door Into Summer.'



Edited 5 time(s). Last edit at 09/26/2022 05:03AM by playerpage.

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Re: Won’t hold idle when warm
Posted by: zarfnober ()
Date: September 26, 2022 07:00AM

I’ll second Steve’s opinion on oxygenated/ethanol gas, of my turbo sat for a couple days, the carb would be empty, so I never bothered trying to start it right away. I had a Holly electric pump on it, and after sitting, I’d turn the key and wait till the pump got gas back there again, you could hear the pump quiet down once the carb filled. Then it’d start right up, and it hasn’t had a choke on it in 22 years.

Hope you get it sorted out, good luck!

Rocco

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Re: Won’t hold idle when warm
Posted by: steve c goodman ()
Date: September 26, 2022 07:54AM

Hello Graham: My logic in being able to turn off the pump is that the fuel 'growns' when hot and there is a risk of having the carb enter a flooding stage and the opposite is needed here NO extra fuel. Also as Rocco states having the switch enables you to fill the carb after sitting for a while. There are ways of installing priming switches etc but that just adds to the wiring through the car etc. It depends upon how safety minded you are with the various relays and cut-off switches that some use. Everyone around here has electric pump wired through the ignition switch with a toggle switch in many cases regardless of engine hp.

In regards to the return spring beware of using a strong return spring. The pivot under the rear seat can be torn from its' mounting point and very easy to do if the floorboard is already weakened from rust/corrosion.

Instead adjust both the adjustable link at the carb to ensure a full travel plus the rod from the trans to the upper linkage can be out of adjustment and trying to hold the carb open at idle conditions.

I hope this is helping.

best wishes, Steve
Rear Engine Spec. Inc. Golden, Colo.

1962 spyder 3.0L turbo---1965 Crown V8
1967 monza 110/4---1968 monza 110/4
1971 amante gt 110/4
CORSA/RMC/PPCC/V8 Registry

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Re: Won’t hold idle when warm
Posted by: gbullman ()
Date: September 26, 2022 09:13AM

I don’t have a turbo car but do have an electric fuel pump. I wasn’t comfortable splicing into the ignition feed so I supply power via switched power. Turns out back in 66 that in the ACC position everything is fed except the ignition so I hid a toggle switch so I can turn the pump off in the ACC position.

For safety in the event of a crash I also installed an inertial switch. I didn’t include the oil pressure switch that many do. I felt the inertial switch was sufficient and didn’t want to deal with the complexity and extra wiring of an oil pressure switch.


Gary
1966 Corsa Convertible
Northern New Jersey


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Re: Won’t hold idle when warm
Posted by: steve c goodman ()
Date: September 26, 2022 09:41AM

Hello Gary: If you splice to 'ign' wire on back of ignition switch the pump will only get voltage when key is in run position. Obviously a fuse must be added.

I started finding defective oil 'vega style' oil pressure switches a number of years ago that left a couple of customers stranded so I quit using that switch.

best wishes, Steve
Rear Engine Spec. Inc. Golden, Colo.

1962 spyder 3.0L turbo---1965 Crown V8
1967 monza 110/4---1968 monza 110/4
1971 amante gt 110/4
CORSA/RMC/PPCC/V8 Registry

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Re: Won’t hold idle when warm
Posted by: wittsend ()
Date: September 26, 2022 10:17AM

One thing I prefer to do with my cars that have an electric fuel pump (only) is to shut it off but leave the engine running for a short duration. This eliminates any residual pressure in the line and lowers the level in the bowl that might experience percolation. It only takes a few seconds to replenish the bowl before the next start. This can be done by putting a switch post ignition switch/pre- pump. A three position switch (full time hot - momentarily on, ignition switched/on/off) will allow for priming but still turn off with the ignition key.

The collision shut off switch has its place and I would never advise against it but do remember on a carbureted car that the float bowl must run dry before the engine will stop. The switches are more to prevent dispersion of fuel than halt the engine from turning. The switches were primarily used with injector cars that had 40-60 pounds of pressure. That isn't to say that 3-6 pounds pressure of fuel isn't an uncomfortable situation if you are trapped in your carbureted car.

------------------------------------------------------------------------------

***'61 Lakewood, a "Freebie" in hibernation for 27 years - In the process of applying CPR.***

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Re: Won’t hold idle when warm
Posted by: playerpage ()
Date: September 27, 2022 07:26AM

Thanks for the mention of the adjustment on the ends of the rod, Steve. A "duh" moment for me.

The spring on the Bluvair isn't THAT much tighter than stock, but just enough, in my opinion. Roger makes a replacement pivot linkage for under the car, too, and I use that in conjunction with the tighter spring. Maybe that could be another avenue for Graham to consider.

Eric C. Player
Fargo, North Dakota
MEMBER: CORSA National, Central Coast CORSA, South Coast CORSA, Vintage CORSA, Sfba CORSA, and Great Plains Corvair Club.
THEN: 1965 Monza 110, Canary Yellow - 1965 Corsa 180 Turbo, Red - 1966 Monza 110, Purple - 1967 Monza 140, Red - 1966 500 110, Black; nicknamed "Shadow" - 1965 Monza 110, Camaro Yellow; nicknamed "Silver"
NOW: 1966 Corsa 180 Turbo, Blue; nicknamed "Bluvair"
---------------------------------------
"He cautioned me not to take notes. It would not have helped if I had, as he would start a paragraph with, 'It is therefore obvious. . .'
and go on from there to matters which may have been obvious to him and God but to no one else."
-- Robert A. Heinlein, character of Daniel B. Davis, 'The Door Into Summer.'

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Re: Won’t hold idle when warm
Date: September 27, 2022 08:18PM

Good call Eric. When I took the drivetrain out this summer I noticed that the pivot mechanism attached to the transmission is a little mangled. I thought I might have also bent the rod when lowering the engine. It’s hard to tell if it’s bent since it naturally has some bends in it. Nonetheless, those two points may be contributing to the less-than-complete throttle closure.

I just re-read the section in Held’s book about the setting for low idle is one screw turn from completely closed to allow air to mix with the fuel. I don’t know why you don’t get sufficient air mixed in with just the right setting of the idle mix screw. Perhaps this just reinforces your point about our YH women!

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