Gas tank vent

PostPost by: frearther » Sun Jun 06, 2010 4:45 pm

I'm trying to solve a new fuel feed problem on my S2; looking at the tank, I'm stumped as to how it is vented to prevent airlock as the fuel level recedes. There is a pipe - apparently a vent pipe - about 1/4 inch wide mounted inside the filler pipe. The bottom protrudes into the fuel. The top is open, but it only opens into the filler pipe which is sealed from the atmosphere when the cap is closed. It looks like a closed system to me, but that wouldn't work. So I assume there is another vent somewhere that I'm overlooking.

Can anyone enlighten me (said he with embarrassment).
Art Frederick
S2 Roadster, built in 1965, registered in 1966, No. 26/4934
Nothing else of interest at present
User avatar
frearther
Fourth Gear
Fourth Gear
 
Posts: 501
Joined: 23 Sep 2003

PostPost by: alan71 » Sun Jun 06, 2010 5:08 pm

The vent is in the filler cap, the small pipe is to let the air out while you are filling the tank.

Alan
alan71
Second Gear
Second Gear
 
Posts: 223
Joined: 15 Jul 2007

PostPost by: frearther » Sun Jun 06, 2010 6:36 pm

My filler cap is the "quick release" type. How do I find the vent to be sure it's not plugged?
Art Frederick
S2 Roadster, built in 1965, registered in 1966, No. 26/4934
Nothing else of interest at present
User avatar
frearther
Fourth Gear
Fourth Gear
 
Posts: 501
Joined: 23 Sep 2003

PostPost by: prezoom » Sun Jun 06, 2010 7:13 pm

Art,

My S2 is equipped exactly like yours, and the tank vents through the flip cap. If you want to check to see if the cap is plugged, remove the cap/tube and try to draw a vacuum from the bottom of the tube with the cap closed. You will have to plug the small tube, and draw through the large tube or just the opposite. If you have a MityVac, it may be easier to plug the large tube with some tape. You should not be able to draw a vacuum and hold it, with the cap vent.

Rob Walker
26-4889
Rob Walker
26-4889
50-0315N
1964 Sabra GT
1964 Elva Mk4T Coupe (awaiting restoration)
1965 Ford Falcon Ranchero, 302,AOD,9",rack and pinion,disc,etc,etc,etc
1954 Nash Healey LeMans Coupe

Owning a Lotus will get you off the couch
prezoom
Coveted Fifth Gear
Coveted Fifth Gear
 
Posts: 1332
Joined: 16 Mar 2009

PostPost by: Robbie693 » Sun Jun 06, 2010 10:37 pm

frearther wrote:My filler cap is the "quick release" type. How do I find the vent to be sure it's not plugged?


There should be a hole in the sealing ring to breathe through. On the cap on my Plus 2 (sorry if these are different - I'm not sure what is fitted to S2's) there was a hole in each half of the sealing plate, 180 deg apart, top and bottom to vent to atmosphere.

Cheers

Robbie
User avatar
Robbie693
Coveted Fifth Gear
Coveted Fifth Gear
 
Posts: 1637
Joined: 08 Oct 2003

PostPost by: frearther » Mon Jun 07, 2010 11:17 am

Robbie, my cap is different - there are no holes in the sealing plate.

Rob, I'll do the check that you suggest. That sounds like a good way to find out whether or not my vent got plugged.

Thanks to all who helped.
Art Frederick
S2 Roadster, built in 1965, registered in 1966, No. 26/4934
Nothing else of interest at present
User avatar
frearther
Fourth Gear
Fourth Gear
 
Posts: 501
Joined: 23 Sep 2003

PostPost by: RotoFlexible » Tue Jun 08, 2010 6:01 pm

frearther wrote:Robbie, my cap is different - there are no holes in the sealing plate.

Rob, I'll do the check that you suggest. That sounds like a good way to find out whether or not my vent got plugged.

Thanks to all who helped.


I believe I've seen the hole in my sealing plate (also an S2). Ever since the tank was reconditioned (along with many other changes to the car), I have had occasional issues that seem related to fuel feed. They have just resurfaced. Has anyone ever experienced fuel feed problems that could be traced back to the cap vent?

An easy way to check this is to simply unlatch the cap when the problem occurs, and see if it goes away.
Andrew Bodge
'66 Elan S2 26/4869
I love the sound of a torque wrench in the morning. Sounds like... progress.
User avatar
RotoFlexible
Fourth Gear
Fourth Gear
 
Posts: 679
Joined: 01 Sep 2005

PostPost by: frearther » Sun Jun 13, 2010 7:25 pm

I just finished a vacuum test on the filler tube assembly, and it does vent to the atmosphere. I used the Mighty Vac procedure since the fuel system was already partly disassembled before I even thought to check the vent. But since the vent works, I guess I have to look for gunk in the line somewhere. Rats! :cry:
Art Frederick
S2 Roadster, built in 1965, registered in 1966, No. 26/4934
Nothing else of interest at present
User avatar
frearther
Fourth Gear
Fourth Gear
 
Posts: 501
Joined: 23 Sep 2003

PostPost by: prezoom » Mon Jun 14, 2010 3:49 pm

Let us know what you find. On my last run, it looks like the DPO's having the fuel tank coated is now coming undone. Something is getting sucked up against the end of the tube in the tank and shutting off the flow. Have to shut off the electric pump and let the stuff fall off then restart the pump to get fuel back in the carbs. Will source a new place to get the tank cleaned and recoated.

Rob
26-4889
Rob Walker
26-4889
50-0315N
1964 Sabra GT
1964 Elva Mk4T Coupe (awaiting restoration)
1965 Ford Falcon Ranchero, 302,AOD,9",rack and pinion,disc,etc,etc,etc
1954 Nash Healey LeMans Coupe

Owning a Lotus will get you off the couch
prezoom
Coveted Fifth Gear
Coveted Fifth Gear
 
Posts: 1332
Joined: 16 Mar 2009

PostPost by: frearther » Mon Jun 14, 2010 5:34 pm

prezoom wrote:On my last run, it looks like the DPO's having the fuel tank coated is now coming undone.
Rob
26-4889

I'm awfully afraid that this is my problem, except that I'm the DPO :cry: :oops:
Art Frederick
S2 Roadster, built in 1965, registered in 1966, No. 26/4934
Nothing else of interest at present
User avatar
frearther
Fourth Gear
Fourth Gear
 
Posts: 501
Joined: 23 Sep 2003

PostPost by: Galwaylotus » Mon Jun 14, 2010 7:45 pm

frearther wrote:
prezoom wrote:On my last run, it looks like the DPO's having the fuel tank coated is now coming undone.
Rob
26-4889

I'm awfully afraid that this is my problem, except that I'm the DPO :cry: :oops:

Look on the bright side. You don't have to go far to give out to the guilty party!! :lol: :lol:
Mechanical Engineer, happily retired!

'67 S3 SE FHC

See Facebook page: W J Barry Photography

Put your money where your mouse is, click on "Support LotusElan.net" below.
User avatar
Galwaylotus
Coveted Fifth Gear
Coveted Fifth Gear
 
Posts: 1348
Joined: 01 May 2006

Total Online:

Users browsing this forum: No registered users and 20 guests