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?

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.

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

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.

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.

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?

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?

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.

weber float adj.

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.

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??

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.

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.

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

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.

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

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!

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.

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?

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.

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.

More to come....


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maybe the holes in the side of the valve body are an upgrade. I saw others like that when I was looking to buy.

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I finally had time and the temp was good in the garage, to work on this.

Got the floats re-set and new top plate gaskets.... coated with some chap-stick. Took a drive around the neighborhood and it ran great....

Re-check for drips and pools in the barrels and saw none. Rechecked this morning, so more than 12 hours and no drips.

Viton did the trick.

new question here tho.....

anyone use a QFT pressure regulator?

This one is giving me trouble. At first I could not get it to go down...... Now I can't get it to go up.

Been trying to see how 2.5 psi does. 1.5 is about as high as I can get it. in the pix below, the engine is idling.

Any tips on what is going on? Is this a crappy regulator? What might be better? Does it take a long time for a SCREW turn to register on the gauge?

I think I will remove it and see what the electric pump puts out on it's own.

I can then maybe take it apart and see if there is something in it....

Other than that, I guess I need to try a better model.

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Looks like a knock off of the Holley LP one ?,with the adjuster set like that you will be getting full pump pressure , however it maybe ported in a differant way ,unlikely but what happens when you screw it out ? if no result just replacing it would be better ,the Holley 12-804 will suit your needs and a well proven unit , just make sure your pump pressure isn't exceeding the range of the regulator by too much ( 1-4psi ) , by all means remove the regulator as it will give you a better picture and also indicate your gauge is ok .
Good luck ,cheers.
Edit ...what is your pump pressure ?

Curious if these were Webers or are they EMPI knockoff?

I remember way back when I got my first IDFs for my original1.7L back in late 80s, they came with solid brass float needles. But subsequent rebuild kits always came with rubber tipped.

Somehow I thought Weber had probably migrated to rubber tips as original parts. Wondering if this is the case?

@malcolm2

Two questions:
1. What fuel pump are you using? It's possible it's output pressure is very low, and an inline regulator plumbed upstream from the carbs can only lower pressure from what the pump puts out, not raise it.
2. You don't have a return line plumbed, right?

They are Webers.

Rotary Electric Fuel Pump, 3.25 psi

https://vwparts.aircooled.net/Rotary-Electr...ed-p/rotary.htm

no return line. Tank to pump. Pump to regulator, one side thru the gauge, last stop is to the webers.

Just sitting all week at the last regulator setting.... no other changes

I started it up last nite and the gauge hit the advertised PSI for the pump... 3.0+. Driver side carb was popping. I hope from too much FP.

I gave the regulator screw 2 full turns. Will re-start and see where the gauge goes.

UPDATE: Tinkered here and there with this regulator screw. It finally got to a point where I could see the needle move as I turned the screw.

So at about the 1/2 way point on the screw is where the action starts. I was able to set the PSI at about 2.5.

Started nicely, ran very smoothly, saw no leaks during the Engine OFF tinkering. I think I got it. Never ends tho.

This issue is never ending......

I took the regulator out of the fuel line. Left the gauge.

I started the engine and saw 2.5 psi. So I took it for a drive around the block.

Seemed to run fine. I did get one LEAN POP during that drive. I stopped a few times and checked the gauge. PSI was not staying at 2.5. By the time I got home it was less than 1.0 psi, again, with no regulator. I parked it and returned in about 10 minutes.

I could hear the fuel filling the carbs. Took the air cleaners off and YEP. Fuel running into all 4 carb ports.

Even with Viton tipped float valves, I am getting a siphoning action with the engine off. Tank is about half full. I pulled the hose from the Tee that is replacing the regulator and raised it above the tank and the flow stopped.

Sorry, but you may remember, this is a 72 bus with a 2.0 TIV. You guys seem to provide the best troubleshooting, so I come back here.

I think I have a Carter electric spare pump, I am gonna install that tonight. Should the pump allow fuel to pass thru it with the engine OFF?

Post picture of where you have fuel pump mounted relative to the fuel tank.

If you are getting a siphoning effect, the pump needs to be mounted higher. Especially since the tank is located higher than the carb bowls and would be able to supply fuel pressure via gravity. Ideally pump would be at top of tank level to break any siphon effect.

@malcolm2

Full transparency - I don’t know about busses. Just giving you the theoretical answer of what needs to be done to break a siphon effect.

Had a similar thought. Run the hose, at least some of it, higher than the tank. Would be easy to try.

If I remember correctly, the pump will push the fuel. It does not do well pulling it from the tank. My old cabriolet MK1 had a pump in the tank and one under the tank.

Regardless, the damn viton tipped float valve should hold back fuel, right? Very low pressure if the pump is off, I would think.

They used L-jet FI in 73. Guess i need to study up on where those were and where the hose ran.

I don’t think I’d agree.

When the gas tank is higher than a carb and can be gravity fed, it usually has a fuel shutoff valve. This is true with my 1948 Case tractor, lawnmowers, generators, etc.

However in all my experiences with hydraulics, it is always assumed an orifice will bleed down over time. This is true of hydraulics spool valves, solenoid valves,etc. Though they may leak down very slowly, they all leak down to some degree. This is also true of solenoid valves in ABS/ESC modules - the solenoid valves all have a degree of leakage over time if you attempt to use them as a long term line lock.

You could try adjusting float level to provide more sealing force but that may cause other issues (low fuel level in bowl) when running.

Picture I found of a bus and fuel pump
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i have some feelers out to see what the OEM L-JET FI (1974 and up) fuel line diagram or pictures look like.

I might look into something similar to your picture. Also need to study up on if the electric pump is ok to SUCK fuel at a high point, similar to your pic.

Agree, it would be better to leave pump at low or mid point and have part of hose (pressure side) higher than tank.

Here’s another example with a Facet pump more at mid tank level
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I’m not a fan of facet pumps due to their noise but they do have pumps available with an anti-siphon valve

https://www.pegasusautoracing.com/group.asp...ID=FACETSHUTOFF

Ooooh, this is fascinating. I think my 2056 with EMPI IDF carbs has a similar problem. Facet pump relocated to the steering rack (from before I owned it). Strong gassy smell after driving and I've had issues with excess fuel getting into the cylinders, especially #3. Fouled a spark plug a while back. I wonder if the anti-siphon fuel pump would help.

Carbs will always have a gas smell when left to sit in a garage as they are an open system. Some run the bowls empty in the driveway and coast into the garage after it stalls.

The tank is about even with the carb inlet on your 914 so I'm not sure gravity pressure is the problem. The only time I have seen carbs drip extra fuel is when a problem with the float and needle is present. "Side load" is the term that is used when the float does not evenly press on the needle allowing fuel to continue to fill the bowl.

Maybe this was discussed, but where exactly is the drip coming from, aux venturi OR the accelerator tube? If auxiliary venturi then float overfill, if accelerator then the check valve has failed.

I assume the float is over filling. Fuel spreads out on the gasket between the top plate and the main housing. Finding it's lowest point the fuel flows into the barrels. It also flows to the outside of the housing and flows down the carb.... makes it's way to the garage floor.

This time most of the fuel was going in the barrels. I disconnected the hose and raised it up... flow stopped. After the bowls evened out the flow stopped and I got some paper towels and stuck them in the barrels to absorb the fuel that was pooling on the throttle plate.

hose path today. yellow line comes out of the btm of the tank to the pump mounted on the side of the frame. Red line goes thru the firewall to the red box (a regulator and gauge). this picture has the removable firewall removed, which is where my regulator is mounted. Purple to the carbs.

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Might try this.... run the white line up into the rear quarter panel cavity and back down to the regulator... which is now a BRASS TEE and the gauge.

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That’s a lot of hose (white path)

Could do this (green) - just get to top of tank and then back down to regulator ? Could do a sort of u-turn drip loop if line has to enter from bottom of regulator?

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Another option; can you lower the regulator to get the distribution lines closer to height of carbs to reduce fuel in lines that can be gravity fed?

I like your idea. found a few decent pictures of the tank firewall and the tank. Notice the height of the red hose.... and then the height of the tank below. that would never siphon.

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My feeling here is it's getting kind of crazy and off track.

If this were my bus I'm going back to basics - float level. Also if I purchased a rotary pump that is only producing 2.5 psi then I'm not running a regulator. I'll maybe run a fuel pressure gauge inline just for sanity, but have had similar setups and just ran pump to carbs.

If you really want to test a theory, put gas in a jug attach to a gauge cap the end and raise the jug. It will tell you how much pressure you have. My guess is less than 1 psi. You can also test your needle valve by hooking the jug up to your carb top. Rest the top on the bench so the float is closed all the way. It shouldn't leak. When you set the float level did you get it to 10mm with the gasket in place and the ball not depressed? This is very important.

AC.net is out of business, but bought the new idf 40s before they shut down. paid for the cleaning and set up per his recommendation.... 12mm on float level. not sure why it is different than the book, but it is. I re-checked the 12mm when I installed the viton needle valve.

Yes, I have lots of tests to try on this. I did remove the regulator and left the gauge. Really did not see any change to the gauge readings. I start the bus.... I see 2.5 psi, i take a drive. I stop and check the gauge, it is down to 1 or 1.5 psi.

So there are a couple things going on...... 1. the random siphon activity and 2. the low driving pressure.

This whole thing started with the siphon activity. I will re-route the hoses 1st. easy to try.

Then I will change the pump and see if my pressure holds. Might try a Facet pump as recommended above.

All test suggestions are welcome, as thing proceed, I will certainly try anything.

I might be one of the only people to remove carbs and go to L-Jet.


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Just a side note on gauge vs pressure.

I wouldn’t trust that gauge as being highly accurate. It appears to be max at about 10 psi and you’re trying to measure down at 1- 2 psi. You can’t expect high accuracy when your nominal pressure and variances are only 10% of gauge and the gauge itself may only have an accuracy of plus or minus 2-5% at standard temperature (73.4 F) and atmospheric pressure (29.9 in Hg).

It may be reading 1 psi hot but it would be hard to tell if that pressure reduction is coming from the pump or the gauge getting hot in the engine compartment.

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I do trust ACN as most of my carb knowledge came from John over several emails when I was just starting out learning them. 12mm is fine and if anything would shut the flow sooner, so not as filled.

Was the regulator always used with your setup?

Random thought:

Is your tank vented properly? Pressure build up in tank so close to heat source could pressurize tank and fuel supply leading to the flooding of carbs / siphon behavior.

Tank is vented. Picture is not mine, but in the picture of the tank above you can see the yellow hoses they go from the top rear corners of the tank, into the engine compartment and up into the D-Pillars then back down into the charcoal can. There is a "bulb" in each line going up into the pillar, i assume it can assist in pressure and siphoning.

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Anyone know where John is now? Hated to lose Cap'n Krusty on here. John was a great resource on the Samba. Kinda Krusty too


Was not there when I ran the engine on the floor of my garage, but I added it as I installed. The low pressure pump is probably fine by itself. Don't see a benefit with it, as I have run with and without.

I guess it is a help if you have a higher PSI pump and need lower psi to run. I guess I listened to some of the inter-web garage hands that maybe only give their personal info and don't always have all the reasons why. Taught me something tho.

You sure those venting lines are clear and not plugged up? It's pretty common on the T3 (not the van T3, the Squareback, Notchback, Fastback T3) for the fuel tank vent lines to get plugged up with rust and junk.

Also on Pg.1 you note that you have those two vent lines connected together which will effectively NOT vent the tank FYI. It's just a closed loop at that point.

I am not familiar with the bus evap system, but on the T3 the vent lines went back to the engine after the charcoal canister and it would pull those fumes into the intake system. I used a kit Jim Adney makes to bypass all that since it is more than likely plugged up anyways, so my tank is open to atmosphere now. The canister on the T3 also tends to collect crap from the road and cause rust under the fender so that was extra motivation.