Weber 40 IDF is dripping Options

[malcolm2]

Nice day for a drive yesterday.... Drove some, filled up with gas and drove a bit more.



Woke up this morning to smell gas in the garage and noticed a pool of fuel on the floor.

I removed the air filter and see a drip in one barrel. 1 barrel is very wet and even has a pool sitting on one side of the plate. The others are wet, so they could be dripping, but less frequent. You know gas, it will evaporate pretty quick.

looks to be coming from the center of #14, Aux Venturi. I removed the Main Jet on that barrel (47 - 50), hoping to get it to stop dripping. I think it stopped.

What is causing this? (IMG:style_emoticons/default/WTF.gif)

I should add that Dual Carbs are new, set up at AC.net... now out of business. Last summer I fully adjusted, and sync'd them. Had been running really well, parked for about a month. Total of about 800 miles on the whole rebuild.

[MikeK]

Sounds like a cracked float allowing fuel past the needle valve.

[Robarabian]

If the carbs are new, it may just be a stuck float valve. Before you remove the tops, maybe pull the float valves and ensure there isnt something gumming them up. The gaskets for the tops tear easily..before you rip into them. I had brand new carbs do this through all three bores. they were laying on the side at some point on the bench and something was stuck. But a small piece of dirt could keep a ball valve open... Otherwise, I agree, could be a bad float in that bowl.

[malcolm2]

I did pull the float on the worst side. I will re-check the float setting. IIRC that was one of the last things I did back in May.

My guess on the drip is pure surface tension. Bowl over fills. Fuel continues to seek a low level and is soaking in the gasket. Makes it's way to the venturi and is able to drip from it's low point.

So is there some residual pressure pushing past into the bowl? Maybe as you said some junk not letting the valve close?

Once on the table, I did a blow test thru the fuel inlet. Seems to block my air.

[Superhawk996]

Here is the thing- fuel tank on a 914 is lower than the fuel inlet on the IDFs.

So with the car turned off, and no fuel pump running, there isn’t much of a fuel supply to bleed into the bowls (even with a stuck needle valve). The only fuel available is what is in the crossover that connects the two carbs.

Are you sure your fuel tank is properly vented and not building up pressure to drive fuel from the tank up to the carbs?

How big of a puddle? Larger than what can be contained in the crossover hose?

[malcolm2]

apologies.... my 914 is L-Jet.... My Bus has the carbs. This group has proven to be better help on engine and carb stuff than the folks at The Samba.....

So I think the full line on the bus tank is higher than the float bowl.

I now have the float on the bench and will check for debris and I will re-set the float as well.

Any other checks to consider?

[MikeK]

Personally, I'd pull both carbs and set the float levels. I'd rather be sure than chasing some mystery problem. Drop the floats in some warm water to ensure they aren't leaking.

I've also seen carbs heat soaking and boiling over, for lack of a better term. If the float/needle/seat solutions don't fix the problem, you may consider running a set of phenolic spacers to keep the heat out of the carbs. This is, of course, once you've checked everything to ensure it's not a problem in the carb.

[MikeK]

weber float adj.

[malcolm2]

help me out here.... you say the phenolic spacers will keep the heat out of the carbs.

I don't see how that fixes my issue. I parked the Bus at 8pm. At 8am I smelled gas, see gas in the barrels.... How does heat or lack of heat in a 45*F garage cause fuel from a full tank to over fill the float bowls.

What I do see.... I pulled the top of the carb, put the hose in a cup on top of the engine. I still get 1 drip per second into the cup. That makes me think the FULL line in the tank is above the end of the hose.

So I have gone back to setting the float. I have cleaned everything on the top plate, checked for debris in the float valve. Cleaned the inlet filter and now looking at the float setting.

Current settings are 11.2mm closed and 23.3mm open. Measurement are with no gasket.

I see 10mm and 32mm respectively on weber sites and other books.

[malcolm2]

Floats are reset to 10 and 32. Cleaned the top plate fully. Re-installed and started her up. Idled and rev'd like a champ. Maybe 3 mins. Shut her down and damn the dripping started again.

During the run, i verified my electric pump's pressure to be 2 psi.

Got one suggestion to use a float valve with a rubber tip. I see several out there in big rebuild kits for the Weber IDF 40s.

Any drawbacks there? What is next??

[gnomefabtech]

How much gas is in the fuel tank? Check to make sure the fuel tank vent is open because if it's clogged there can be pressure build up after the fuel warms up.

[malcolm2]

have not checked, but I did take the fill cap off for now. I just filled the tank. It actually spilled out at the pump. So it is extra full.

This tank has two small pipes on the top corners. Those pipes run up into the D-pillars of the bus and back down into the engine bay. On the upward direction of each there is an oversized bulb section.

These pipes are supposed to go to the charcoal filter, which i am not using. I have connected the pipes together with a hose in the engine bay.

[VaccaRabite]

Are you sure its not the two large lead plugs in the carb that are leaking? That's a super common place for IDF carbs to leak. When I had carbs I drilled them out and replaced with NPT plugs. All 4 of those plugs on my car were weeping fuel. I have a thread on it somewhere here about the issue and the fix.

Zach

[malcolm2]

what is a LEAD PLUG?

To get the top plate off, I had to pull the hose from the barbed inlet. I placed the open hose end in a bucket. The whole day, as I was putz-ing with the floats, the hose dripped into that bucket. Hoses from both carbs (each side) did that.

So i think i have 2 things at work here. Fuel is siphoning past the electric fuel pump, that is the drip in the bucket..... and #2 is when attached to the carb, that drip over fills the float bowl. So I assume the valve is not closing off.

[VaccaRabite]

All IDF style carbs have 2 large prominent plugs (they used to be lead I don't know what they are made of these days). They are known for leaking and have been the cause of many fires over the years. When the plugs fail they drain all the gas out of the bowl out and down on to your engine.

Found the thread!
http://www.914world.com/bbs2/index.php?showtopic=133490

Zach

[MikeK]

help me out here.... you say the phenolic spacers will keep the heat out of the carbs.

I don't see how that fixes my issue. I parked the Bus at 8pm. At 8am I smelled gas, see gas in the barrels.... How does heat or lack of heat in a 45*F garage cause fuel from a full tank to over fill the float bowls.

What I do see.... I pulled the top of the carb, put the hose in a cup on top of the engine. I still get 1 drip per second into the cup. That makes me think the FULL line in the tank is above the end of the hose.

So I have gone back to setting the float. I have cleaned everything on the top plate, checked for debris in the float valve. Cleaned the inlet filter and now looking at the float setting.

Current settings are 11.2mm closed and 23.3mm open. Measurement are with no gasket.

I see 10mm and 32mm respectively on weber sites and other books.

You mentioned that you parked the Bus after a drive. Heat soak from the heads to the carbs can vaporize the fuel in the bowls of the carbs and in some instances may push some fuel past the needle and into your engine. This seems to be more of a problem with ethanol-mix fuels. This may or may not be your problem.

From what you describe here, it appears that your needle and seat are leaking. Viton, standard, whatever, replace them with genuine Weber parts and your problems are likely solved. If not, then it's something else.

Oh, and your fuel pressure is set too low if it's at 2 psi.

Good luck!

[MikeK]

One last thing. The lead (led, not leed) plug is used to plug holes made during the machining of the carb, much like the aluminum plugs which are swaged into the engine case during machining of the oil passages.

It's and imperfect World and sometimes things like this leak. That's why conscious and knowledgeable builders pull said plugs and replace them with threaded and sealed plugs.

Haven't seen a carb one leak, but I'm not the least bit surprised.

[rhodyguy]

The plugged holes are also for getting core cavity material out of the castings. The cores form the passageways. I can’t see fuel getting past a new rotary FP that’s not pumping. Lowering the pump a bit?

[Superhawk996]

Got one suggestion to use a float valve with a rubber tip. I see several out there in big rebuild kits for the Weber IDF 40s.

Any drawbacks there?

Watching this one evolve

With respect to rubber tipped needle - at this point I thought most carbs have probably been rebuilt wirh rubber tip needle.


If you don’t have them - get them. No downside to them that I’m aware of.

[malcolm2]

I got screwed by the USPS. Pierce got the order, shipped it the same day. Gave me tracking number..... I watched it for a week as it bounced around the state of Georgia. Not my state !!! I called and Pierce send another set. The ARRIVED. Too bad, I am out of town this weekend.

You can see the non-viton one does have a ridge. Brand new carbs. Went thru 3 tanks of fuel and there is a ridge. (IMG:style_emoticons/default/bs.gif)

More to come....