Vapor Recovery Hoses - what to do?

[Theodore]

Vapor Recovery Hoses - What to do?

Am working to restore a '90 GW that's been fuel-injected by PO with nearly all of the vapor recovery stuff removed as part of that process. I'm working on cleaning up the engine compartment, and one of the remaining things/loose ends: is this set of vapor recovery/gas tank vent hoses. I'd like to remove them & cap the connections on the fuel tank. I've already got a vented gas cap (due to an issue a couple of years ago with gas being pushed out of the tank due to high temperatures a couple of years back), so this seems plausible.

Is there a good reason why this shouldn't be removed & capped at the tank?

Has anyone done this & if so, where'd you find caps?

[tgreese]

Other than the very desirable characteristics of vapor recovery vs. a vented cap, there's no reason to keep it. And vapor recovery is really easy if you don't need a float bowl vent. Easy. And completely passive, no effect on mileage or performance - all positive.

I'm running an XJ canister on my J20, and it works fine. Hardest part was making a bracket to hold the different-shape canister.

Map out what you've got; single vent line to the canister, purge line to manifold vacuum, purge signal to ported vacuum.

[Theodore]

Other than the very desirable characteristics of vapor recovery vs. a vented cap, there's no reason to keep it. And vapor recovery is really easy if you don't need a float bowl vent. Easy. And completely passive, no effect on mileage or performance - all positive.

I'm running an XJ canister on my J20, and it works fine. Hardest part was making a bracket to hold the different-shape canister.

Map out what you've got; single vent line to the canister, purge line to manifold vacuum, purge signal to ported vacuum.

Hey, Tim, was hoping youd weigh in. Have seen other posts youve made re: vapor recovery. ? - can I run the manifold & ported vacuum connections straight to the throttle body, or do I need vacuum switches involved? Am planning a run to the junkyard soon for a vapor recovery canister to give it a try but am not sure.

[tgreese]

No switches needed. There are bunch of similar canisters out there that will function like the original. You need a canister with a diaphragm in the top that will close the canister when there's no vacuum (the purge signal). Your throttle body has a ported vacuum port.

[tgreese]

Here's a thread that covers the gist of it. https://www.jeepforum.com/forum/f12/vap ... e-2492001/

You need a canister with the purge valve. The canister closes up mostly at idle in response to the purge signal, so that it does not seem like a vacuum leak at idle. Then off idle, the purge opens and draws vacuum across the charcoal bed.

[FLeetFox]

Tim, this might be a dumb question, but is it possible to get a purge signal by teeing into the vacuum line from the carb that feeds/pulls the distributor vacuum advance? I think you stated this above, but I can be a little dense, Sometimes a lot dense.

Motor is modified, no CTO, etc.. , very little in the way of emissions.

Fleet Fox

[tgreese]

You need a ported vacuum signal. All carburetors have this, AFAIK. The GM Rochester throttle body has this signal too.

Purge signal = ported vacuum. Canister purge = manifold vacuum.

Ported vacuum is the same as manifold vacuum, except at idle. The port in the carb or throttle body is blocked by the throttle flap at idle, so vacuum goes to zero or very near zero at idle. Easy to test, if you aren't sure from the vacuum diagram.

Sometimes ported vacuum is called distributor vacuum, but you have to test the ports on the carburetor. One or more will be ported, others will be regular manifold vacuum. Don't look at the distributor - it could be connected to either ported or manifold vacuum - look at the carburetor for the vacuum port you need.

[tgreese]

Looking again, I think what you are asking is, can you tee into your ported vacuum port even if it's connected to other devices? Yes.

As long as you aren't leaking the vacuum signal to the air, you can pretty much run as many devices as you want from the ported vacuum source. The engine has way more vacuum to spare than you'll use up with these little vacuum motors like the canister valve or the distributor advance or whatever. They aren't open to the air - they just move in response to the amount of vacuum. Takes some energy but very little volume - unless they leak.

The vapor canister sucks air constantly to purge gasoline vapors trapped in its charcoal bed. That's why it's shut at idle, when this metered vacuum leak might make a difference.

[Theodore]

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Vapor Recovery Hoses - What to Do? - SOLVED

It's been a long time, since I posted about gas gushing out of the gap cap (11/2018) (https://www.fsjnetwork.com/forum/viewto ... 52#p168852), and issues with the gas pump constantly shutting off due to no vent... First step then, was to get a vented gas cap & leave the vapor recovery hoses alone until i could find the parts required to put things back to stock; it took 3 years to find/source a charcoal canister & man, i glad i did! After 3+ years of owning the GW, i can finally pump gas unimpeded. thanks [mention]tgreese[/mention]!
for the recommendation to add this capability back.

The charcoal canister & now installed non-vented gas cap was part of a treasure trove a friend of mine tripped across in a local junkyard a couple of weeks ago, that included leather seats, leather-wrapped steering wheel, radio, rear air deflector, etc.; most of which will be added to our '90 GW - see here: https://www.fsjnetwork.com/forum/viewto ... =7&t=22226.

Following [mention]nograin[/mention]'s advice (http://www.ifsja.org/forums/vb/showthread.php?t=174213), i used Dupont Viton 1/64" rubber sheet to replace the blown diaphram under the purge signal cap.

Charcoal canister & mounting bracket came from a GW in Jake's FSJ Junkyard in Burnsville, NC - Thanks, Jake! [mention]tanker[/mention]


First by tracing around the existing diaphram(pic bottom left), and cutting carefully(pic bottom right), then by cutting closely around the metal to sit on top of the spring.


Success!


After rebuilding the charcoal canister, i set about finding parts to replace the vacuum switch, hoses & fittings. Thanks
[mention]mysticrob[/mention] for pointing me to the Howell Vacuum diagram.
Howell Vacuum Diagram by Robert Stone, on Flickr

Parts list:

• 2-port vacuum switch - Standard Ignition Products - PVS71
• 5/32" vacuum tubing - Gates #27038
• 7/32" vacuum tubing - Gates #27039
• 1/64" Dupont Viton from Dixie Rubber & Plastics, Greenville, SC
• 5/16" Fuel Line - Gates - 8ft - replaces the vapor recovery hoses
• 5/16" Elbow - Gates #28620 or Napa NBH-9920
• 3/8"x3/8"x1/4" Tee - American Grease Stick - PRF44B
• 3/8" Tee - Gates #28632 or Napa NBH-9932
• 3/8" Elbow - Gates #28622 or Napa NBH-9922
• 1/4" Tee - Gates #28631 or Napa NBH-9931
• 1/4" -> 3/16" Reducer - Gates #28593 or Napa NBH-9893

Note: I have the parts to connect to the EGR, but haven't yet verified if it's good; and, have seen mention that it's better to run an ECM-controlled EGR valve, if running EFI; so, jury's out on that right now.

Underhood