Finding the source of a gas leak

[Minnesota_Slick]

Hi folks,

My late model A4 has a gas leak somewhere around the carb. I've done a thorough inspection of the fuel lines from the electric fuel pump(which is installed on the bulkhead). The in-line fuel filter was leaking, so I've replaced that, along with the hose that went from the pump to the in-line filter.

The hose from the inline fuel filter to the carb is not leaking, but I'm not so sure about the actual brass elbow that screws into the block. It looks like the previous owner used some black goop(RTV?) on the threads instead of pipe tape.

If I unscrew that elbow, would I use pipe tape on the threads, or will gas eat that tape? If not pipe tape, then what?

Shortly after purchasing the boat last summer, the carb burped a bunch of gas into the bilge. So we had to pump that out, and, being new to the A4 and not having my Moyer's Manual yet, I paid the local boat mechanic to install a new carb kit.

The gas doesn't seem to leak out when it's just sitting there, as I've cleaned it up, come back the next day, and it's still clean. I think it must be leaking either while running(yikes!) or right after stopping the motor from a trip on the lake.

Are there any other places other than the gasket between the top & bottom halves of the carb, where gas can leak out the carb?

Right now, I suspect either that gasket(which I assume was replaced when they changed out the carb kit), or the brass elbow. But if there are other possible culprits, please guide me.

This A4 runs like a dream, but it seems like it's been one gas leak after another since I bought it.

I'm tempted to remove the carb and do an inspection and re-install. But I've got about only 2" of clearance on that side of the engine. It's really difficult to work on.

The mechanic who replaced the carb kit was the first one to inform me about installing a oil pressure safety switch, so I'm also doing that this week. That's another fun one, because the install spot is right above the oil pressure adjuster, which is also on that side of the engine.

Any advice of how to methodically track this gas leak down is greatly appreciated.

[CalebD]

gas leaks/smell

A few things...

These engines can have a hodge-podge of new/old parts as mine does. We have the vertical flame arrestor which provides a place for any excess fuel to leak out of the carb. Many others have a horizontal flame arrestor which points up and holds the fuel in the carb.

It is much easier to remove the carburetor (2 bolts and the throttle and choke controls & fuel line) and work on it on a bench when you do. You may consider making a removable panel to make this kind of work easier if it is very tight access.

My experience with fuel issues after 10 years of A4 ownership tell me that most fuel leaks are associated with dirty fuel clogging the float valve of the carb. If that gets stuck open it will allow some gas to drop down into the carb where it may accumulate and eventually leak out or evaporate. In my case the cause of this was dirty fuel in our gas tank. You might consider pumping out your tank and inspect the last few gallons carefully as any gunk will float under the gas.

Replacing old hoses & filters is always a good idea but will not clean up the problem if the bottom of your tank contains what is pictured below:

[Overdraft]

permatex for gas fittings

Don't use tephlon tape or RTV for fuel line fittings. Use Permatex Form-a-gasket #1 as a sealant on the threads of rigid fuel fittings such as the elbow you describe. Might well be what is on there now.

[Minnesota_Slick]

Thanks for the replies and tips, guys. I sure do appreciate it.

Here's a pic of my A4, and the tight confines I'm dealing with on the manifold side. I'm not sure if I can make an access panel, because frankly I'm not sure what's behind the fiberglass opposite the carb. I'll have to go down into the aft port locker where the fuel tank battery charger and wiring panels live. I might be able to squeeze in there and find what's just beyond the exhaust.

Permatex #1, check.

Shouldn't the (Edit: thanks ndutton!)flame arrestor prevent the fuel from spilling out if I have a float valve stuck?

If I go ahead and remove the carb, will it be readily apparent if the float valve is clogged?

For bonus points, can anyone tell me what that thing is that's sticking out the front, just below and to the right of the thermostat?

[ndutton]

A couple of things Slick,

It's not a fuel arrestor but rather a backfire flame arrestor. Get enough fuel in there and out it will come.

About the limited access where the OPSS is normally located, nothing says it HAS to go there. It can be installed at the same location as the oil pressure gauge sender. If considering this be aware of added weight on the lengthy and small pipe nipple. I made an oil pressure manifold out of 1/8" NPT Tees for the gauge sender, fuel pump OPSS and alarm sensor all fed from the oil port behind the flywheel. Due to weight concerns I mounted the sender array on a nearby bulkhead and connected it with 300 psi hose.

It should resolve your access problems.

[Minnesota_Slick]

A couple of things Slick,

It's not a fuel arrestor but rather a backfire flame arrestor. Get enough fuel in there and out it will come.

About the limited access where the OPSS is normally located, nothing says it HAS to go there. It can be installed at the same location as the oil pressure gauge sender. If considering this be aware of added weight on the lengthy and small pipe nipple. I made an oil pressure manifold out of 1/8" NPT Tees for the gauge sender, fuel pump OPSS and alarm sensor all fed from the oil port behind the flywheel. Due to weight concerns I mounted the sender array on a nearby bulkhead and connected it with 300 psi hose.

It should resolve your access problems.

Thanks, Neil! I've edited my post above so as not to confuse a rookie reading this thread in the future.

You must have read my mind regarding the nipple where the oil pressure sending unit is located behind the flywheel. I was wondering if that was a "legal" configuration. I did read in the Moyer Manual that you don't want that nipple to break....ever.

Believe it or not, I can actually get to the "normal" location of the OPSS if I lie on my tummy in the rear berth and get it from behind. I'm taking my 1/4" ratchet down to the boat tomorrow to see if I can get that plug removed. I wasn't able to do it with a thumb ratchet today. It's in there pretty tight.

Any idea what that thing is that looks like a spark plug that's SE of the thermostat? It's got a wire attached so I'm guessing some kind of sending unit like a water temp sending unit?

[ndutton]

Any idea what that thing is that looks like a spark plug that's SE of the thermostat? It's got a wire attached so I'm guessing some kind of sending unit or maybe a water temp sending unit?

Correct, water temp sender.

[Scuppers]

MS,

That is the cleanest and neatest engine I have ever seen. Nice work!

Mark, up the river from you

[Minnesota_Slick]

MS,

That is the cleanest and neatest engine I have ever seen. Nice work!

Mark, up the river from you

Ha, thanks Mark!

Actually, when I get the gas leak fixed I'm going to take a wire brush and a can of spray paint to it to clean it up even more. The PO did a wonderful job with her, and I'm determined to continue his legacy.

The PO didn't sail her much in the past few years, but instead rewired it, redid the exhaust system, hoses...well, everything. We were really lucky to find a boat in this shape.

[seapadrik]

Slick,

You have an Ericson 29. Mine is one year older ( 1976 ). Great boat and fairly decent engine compartment when compared to some, with one exception: That entire right side ( carb side ) of the compartment when looking aft.

My engine compartment has a rectangle cut into that bulkhead to allow access to that side so you can adjust carb, adjust choke screw and just get something done. You essentially are then able to reach your right hand into one of the galley cabinet doors and hook left through that space.

Mine is about 20 inches long and 7 inches high and provides me some ability to work in that area. At some point when you have your carb removed and fuel lines out of the way, you might consider making such a modification yourself. I use a Multi-tool with appropriate fitting for this kind of cut.

https://www.ridgid.com/us/en/jobmax-3-amp-multi-tool-starter-kit

I may see if I can find a photo that shows the access rectangle that I am talking about and send it to you.

Good luck.

[seapadrik]

Here goes ( photo taken as I was reinstalling my engine ).

[lat 64]

I am not sure the glass fuel filter you have inline from the pump to carb is Coast Guard approved. I had one and it was useful for seeing the flow of fuel but it may not pass the burn-test requirements.

Get the leak fixed soon. A small leak is dangerous. A co-worker blew up his boat last summer and sent his 15-year-old daughter to the burn center. it's that serious.
I learned so much about this subject on this forum. I am just embarrassed about my ignorance before then.


Russ

[Marian Claire]

Fuel line touching the manifold????
Dan S/V Marian Claire

[edwardc]

For bonus points, can anyone tell me what that thing is that's sticking out the front, just below and to the right of the thermostat?

That's your temperature sensor. It extends into the cooling jacket in the head and measures the coolant temperature at that point.

[Minnesota_Slick]

Slick,

My engine compartment has a rectangle cut into that bulkhead to allow access to that side so you can adjust carb, adjust choke screw and just get something done. You essentially are then able to reach your right hand into one of the galley cabinet doors and hook left through that space.

Mine is about 20 inches long and 7 inches high and provides me some ability to work in that area. At some point when you have your carb removed and fuel lines out of the way, you might consider making such a modification yourself. I use a Multi-tool with appropriate fitting for this kind of cut.

I may see if I can find a photo that shows the access rectangle that I am talking about and send it to you.

Good luck.

Many thanks, seapadrik!

I have both the reciprocating tool and a dremel, so I should be set to make an access panel. One thing I can't quite tell from your picture, though, is what's on the back side of the panel? Isn't the galley cabinet floor in the way, or did you take your tool to that, too?

Fuel line touching the manifold????
Dan S/V Marian Claire

Point taken! I'm pretty sure it's been like this for years, but I agree that heat against a fuel source is not a winning combination. I will see how I can redress that situation.

Looks like my whole week of vacation is going to be spent with the boat!