Vacuum controlled check valve?

[Eric]

Hello,
Is there a vacuum controlled check valve that with stand gas fumes/vapors, that be small enough to put on or near an air cleaner.

Reason I ask, Is.
If I can block the carburetor fuel bowl vent. While engine is off, The fuel in the carburetor bowl would most likely not dry up while vehicle sits a week or two.

If you start it the next day it starts right up, If you start it 2 days later, it'll start right up. 3 days f sitting it takes a few extra cranks.
A week sitting double the cranking of the 3 day. Week and a half to two weeks. long cranking. Like draining battery and starter cranking slower long cranking, I'm sure that is not doing the starter any favors.
Already check to make sure the bowl plugs on the bottom of the carburetor are not leaking,(70's gm 4venturi carburetor) but the fuel is drying out of bowl.
If after a week and a half go by, if we take 60 cc of fuel ( 2 fluid ounces to you I guess) and dump down the carb. it start right up. and run almost long enough most times for the fuel pump to get enough in the bowl to stay running.
Only other thing, I've come up with was a vacuum line from vent to base of hood near windscreen, and a moped manual fuel shut off to manually close off the vent. and hope you remember to open it before you go to drive away.

[anotheridiot]

I had problems with mine on the 99 Jimmy that ran the air duct system for the heat and cooling. I would think you would want a 3 way, (dont we all), but maybe 2 and a t so it could vent?

https://www.amazon.com/ACDelco-14047619-Original-Equipment-Control/dp/B000C982H2/ref=sr_1_1?keywords=vacuum+check+valve+3+way&qid=1581084522&s=automotive&sr=1-1

There are others on there as well, but just make sure they are not just for water.

[cstmwgn]

Not what you are asking for BUT an electric fuel pump pretty much solves the hard starting part (not the gas evaporating part)

[DanStokes]

A 12VDC solenoid valve would do the job - just run a switched power wire. These are pretty common. Get a normally closed valve (spring loaded to closed position) so it'll open when power is supplied and allow the float bowl to vent then close when the power is off. Here in the US most towns of any size have an industrial fittings store such as Parker-Hannifin or Swagelok and they carry these. They're also available online (Ebay, etc.) but the quality is unknown. If you find a decent brand on line (ASCO, Red Hat, others) they should be fine.

EDIT: Here's one example, if you trust Amazon quality: https://www.amazon.com/4inch-Normall.../dp/B074Z5SDG3

Dan

[Eric]

A 12VDC solenoid valve would do the job - just run a switched power wire. These are pretty common. Get a normally closed valve (spring loaded to closed position) so it'll open when power is supplied and allow the float bowl to vent then close when the power is off. Here in the US most towns of any size have an industrial fittings store such as Parker-Hannifin or Swagelok and they carry these. They're also available online (Ebay, etc.) but the quality is unknown. If you find a decent brand on line (ASCO, Red Hat, others) they should be fine.

EDIT: Here's one example, if you trust Amazon quality: https://www.amazon.com/4inch-Normall.../dp/B074Z5SDG3

Dan

Well, um. !2 volt switching relay (solenoid valve) and fuel vapors. Maybe if the solenoid was divorced from the sealing part(valve).
I don't know enough about things like this to trust any seal it might have to keep the vapors out of the 12v powered part of the unit.

[Eric]

Not what you are asking for BUT an electric fuel pump pretty much solves the hard starting part (not the gas evaporating part)

Three things
1) Not really wanting to have to add wiring and plumbing To the list
2) The evaporating fuel leaves crud in the bowl. Not ideal for the small channels in the unit or needle,seat .
3) Pumps (electric) out side of in-tank pumps don't have a great record of reliability .

[cstmwgn]

...2) The evaporating fuel leaves crud in the bowl. Not ideal for the small channels in the unit or needle,seat ...

Well, I hear a lot about carbs getting gunked up by LEAVING fuel in them over extended periods of time.

...3) Pumps (electric) out side of in-tank pumps don't have a great record of reliability...

I have been running external electric fuel pumps for over 40 years and have only had a couple fail in that time. One of the main issues with electric pumps is the need to run good fuel filters. On lower output combinations, the carters (P4070) have proven to me to be very reliable and can support 500hp. You can also leave the mechanical pump plumbed and functional. If you were so inclined you could put the electric on a toggle to just prime the system and not use it to run the car. I have run both mechanical and electric on the same vehicle at the same time with no issues.


I have seen mechanical valves that rely on vacuum to operate but I would be concerned that they might influence float level adversely.

[RockJustRock]

In the old days they used to blame float bowl evaporation on residue wicking the fuel up on the float and sides of the bowl. Rather than re-engineering the fuel system perhaps a good carb cleaning and rebuild is in order?.

[Eric]

In the old days they used to blame float bowl evaporation on residue wicking the fuel up on the float and sides of the bowl. Rather than re-engineering the fuel system perhaps a good carb cleaning and rebuild is in order?.

It was just gone through.
new float, new gaskets, new needle/seat everything that comes in a r&r jiffy kit.
And bronze (I think) throttle shaft bushings.
I do need to get a new chock pull off, and maybe the a/c idel bump thing. They have not checked those yet.

[Eric]

Well, I hear a lot about carbs getting gunked up by LEAVING fuel in them over extended periods of time.


I have been running external electric fuel pumps for over 40 years and have only had a couple fail in that time. One of the main issues with electric pumps is the need to run good fuel filters. On lower output combinations, the carters (P4070) have proven to me to be very reliable and can support 500hp. You can also leave the mechanical pump plumbed and functional. If you were so inclined you could put the electric on a toggle to just prime the system and not use it to run the car. I have run both mechanical and electric on the same vehicle at the same time with no issues.


I have seen mechanical valves that rely on vacuum to operate but I would be concerned that they might influence float level adversely.

The unit getting gunked up. is why it is being run every so often ,
Also to empty the tank as the fuel gauge is reading full ,and that needs to be looked into
The vehicle isn't mine (yet) we plan on using it on the power tour and if we can bring it legally back with us, then the title will change hands.
Rather not put a bunch of equipment the owner might not want on it, in case we can not take it with us and it is still thiers.
If I knew we would 100% be allowed to bring it back with us.
Ya ,sure put the money into it.

[RockJustRock]

Still sounds like something out of the ordinary on THAT carb. The accel pump can't be evaporating and that will be enough gas to run to refill the bowl. I'd wait until after Power Tour to worry it. You'll be starting it there daily.

[anotheridiot]

Still sounds like something out of the ordinary on THAT carb. The accel pump can't be evaporating and that will be enough gas to run to refill the bowl. I'd wait until after Power Tour to worry it. You'll be starting it there daily.

Does not sound out of the ordinary, might help to get some heat shield between the manifold and the carb so the heat is not boiling the bowls after it gets turned off.