who is right ?????? 2 Different viewpoints

[kussfamily]

3 Connections on a fuel pump. One coming from the tank. One going to the Carberator. One plugged. Where does it go. Half the people I talk to say it goes to the carberator and is a vent in case the diaphram gets a hole in it, It will give you that indication via a clear line to the carb. The other half say no, a clear line would get hot and melt and they have seen it where the 3rd line goes back to the fuel tank since A gas combustable engine burns 60-70% of the fuel and 30-40% has to be exhausted, returned back to the fuel tank or forced into the block mixing it with the oil.<br /><br />So who is right ? Should fuel come out of that 3rd connection. Its located at the base of the fuel pump. I'm totally confused. Like to hear what point of view is and why there are so many people who disagree about what the 3rd connection is for.

 

[flashback]

Re: who is right ?????? 2 Different viewpoints

you didn't mention what kind of engine,carb etc. but in most cases, it goes to the carb and just dumps into the intake ports. and it is a safety feature to prevent the gas from getting into the crankcase in th event of a leak in the diaphram...I have a 350 chevy 1980. the fuel pump has a sight glass on it which i check regularly for signs of fuel. as far as a clear hose to the carb goes, I don't know..........good luck......

 

[kussfamily]

Re: who is right ?????? 2 Different viewpoints

1978 Mercruiser I/O 120HP 4cyl

 

[Trent]

Re: who is right ?????? 2 Different viewpoints

Factory part and USCG MUST. If the double diaphram fails fuel is sucked into the carb and into the intake. Its normally a yellow line. <br /><br /> Fuel Pump

 

[bomar76]

Re: who is right ?????? 2 Different viewpoints

Quote " Like to hear what point of view is and why there are so many people who disagree about what the 3rd connection is for."<br /><br />The only people who disagree are fools who have no idea what it is.<br /><br />In a marine mechanical fuel pump if the diaphram fails, the fuel that in an automotive application would spill out on the road is diverted to the intake manifold via a clean tube. Thats a REAL BAD thing to have in your enclosed engine compartment. Gasoline vapors are explosive. Most marine fuel pumps have 2 diaphrams so the engine will still run but fuel will leak past the ruptured one to the tube.<br /><br />If you have fuel coming from the 3rd connection you need a new fuel pump. Period.<br />Put the clean tube on and see.<br /><br />Wanna see pictures of the same tubes on both my boats? Be happy to send pics. Or, go to any boat dealer and look @ the engines there.<br /><br />I would not knowingly ride in any boat that had that vent plugged.

 

[Bondo]

Re: who is right ?????? 2 Different viewpoints

An Automotive Mechanical Fuel Pump, would have a small hole in the casting in the same place the vinyl tube is attached.... <br />On a car, When the diapharm Fails, it'll drip onto the road... Or in a Boat, into your Bilge....<br />On a Marine Fuel Pump, the tube directs the spilled fuel to the carb. throat, causing an extremely Rich condition.... When you see the fuel in the tube, You'll know you need a fuel pump...... <br />Or, In your case, Someone just Plugged the vent,+ Started sending all that raw fuel into your base.... Does the oil smell "Gassy" ??????

 

[kussfamily]

Re: who is right ?????? 2 Different viewpoints

where can i get a clear tube and where do i connect it to my carb ? there is no obvious connection

 

[biloxiriver]

Re: who is right ?????? 2 Different viewpoints

Don't know if this was correct or not, but here goes. About 2 years ago a marine mechanic observed that third connectin on my fuel pump was not connected, this was on a 165 mercruiser I/O with a GM 250 in-line 6 cyl with a rochester carb. So he ran a standard fuel hose from the connection up to the carb filter, and he merely drilled a hole in the filter element and secured the hose in the element so that it would dump into the carb throat. He told me that this was so fuel would flow into the carb if the fuel pump diaphram leaked, and in the event of a severe failure would flood out and kill the engine. Since there is no other connection point on the carberator this was the only way to connect the line. Any thoughts on this one.

 

[magster65]

Re: who is right ?????? 2 Different viewpoints

I guess that would work but it seems odd for a marine carb to not have the connection. I'd use clear line so you can see in it. My Merc 7.4 has a clear line on it.

 

[akriverrat]

Re: who is right ?????? 2 Different viewpoints

biloxiriver, many spark arrestors come with the fitting for this hose from the factory. sounds good to me. nukerick, you have a lot of friends that grew up with fuel injection. reminds me of recently graduated certified mech who couldn't fix lawnmower engine...no computer hookup. second diaphram goes and crank bearings follow.

 

[biloxiriver]

Re: who is right ?????? 2 Different viewpoints

nukerick, sounds like you got your answer. By the way, have you asked your local mercruiser repair shop??

 

[biloxiriver]

Re: who is right ?????? 2 Different viewpoints

nukerick, don't know if you have had any luck finding that clear tube or not where you are, but it cannot be found here. I checked my current boat, an inboard, sure as heck no tube, so went looking for a fuel resistant clear pvc tube. Turns out the "yellow" tube is made by a company called Tygon (sp?) and they will only sell in bulk. NONE of the local marine outfits here sell or carry it. The only place I have been able to find it is a small engine repair shop (lawn mowers, weedeaters, etc.) and the largest they carry is a 3/16. Bought a small peice to try but lo and behold, when they installed the fuel pump on my engine the vent port is obstructed by the engine oil pressure sending unit, so I have to pull the fuel pump to install it! LOL! Will it ever end? Anyway, don't know if tube will work or not, lady sellin it said it will stretch over fitting, looks like a weekend job.

 

[prosin]

Re: who is right ?????? 2 Different viewpoints

It has to be to flood the carb in case of a fuel pump failure.

 

[fishhunter911]

Re: who is right ?????? 2 Different viewpoints

my brand new 3.0 mercruiser has the clear tube.... was told exactly what yall said.. incase the pump fails it shows fuel in the tube and tells u that your pump is bad.. this was from the Mechanic

 

[kenimpzoom]

Re: who is right ?????? 2 Different viewpoints

I've seen Tygon tubing at Lowes and The Home Depot.<br /><br />Ken

 

[kussfamily]

Re: who is right ?????? 2 Different viewpoints

Should I drill a hole in my flash arrestor to connect the tygon tube Its the right carborator for my boat (model wise), which doesn't make any sense to me. figure they would already have the hole for the fuel pump. ??

 

[newDIYer]

Re: who is right ?????? 2 Different viewpoints

On my 1972 Merc 140 I/O with rochester carb I had a connection on the starboard side, same side as fuel pump, of the carb just below the flame arrestor.<br /><br />In my case the previous owner had installed an automotive fuel pump and and placed a plug in this hole in the carb. I have replaced the fuel pump but like you still need to get the line connected.

 

[biloxiriver]

Re: who is right ?????? 2 Different viewpoints

Sounds like there is a number of us running around without that line connected; coastys would love that. Personally, if it came down to drill a hole in the flash arrestor or not have the line, I would drill the hole. As it is, my Tiger is parked until I get it installed; not worth the potential damage! Fortunately there is a connection at the base of my carb (Holley 4bbl).

 

[wires crossed]

Re: who is right ?????? 2 Different viewpoints

nukerick the hole should already be there under the arrestor(manual man it will help)my manual clearly agrees with Fishhunter911. Either the port is plugged off by a bolt or screw and it is not obvious or someone has replaced the carb with a automotive one. Use caution drilling into a carb you can ruin it. Remove to drill you don't want metal shavings in your intake. Try looking dead center at the base of your carb on the starbord side, center of the motor, get down next to the motor on fuel pump side you should see the connection and the line needs to be CLEAR I have the same motor manual says IF YOU SEE FUEL IT THE LINE REPLACE THE FUEL PUMP IMMEDEATLY so it must be clear, any hardware store clear hose that fits will work this is NOT a fuel supply hose it IS a safety hose check periodicaly for fuel in the line. Look closely before you drill. I would suggest to tap (thread) the new hole and install a nipple only if it is nessary.<br />Be carefull.