View Full Version : Carburetor Problems i think need help quick
04-22-2004, 09:26 PM
" Hi! I'm new here, but I am having a little problem with my boat. I just purchased a ?ust-about?new motor from some good guys in Michigan. The engine is great, but it did not come with a carburetor. I purchased a Holley carb to put on my GM/Volvo Penta 3.0L inboard motor. (I'm very new to marine terminology so bare with me) The motor is in the boat and has a shaft that drives the propeller through an outdrive. (I think i got that right) But as it goes, the motor cranks fine, but it seems to die after about 45 seconds. I salvaged the fuel pump from the previous motor which bolts onto the bottom end of the engine, and has a lever that hits the crankshaft, moving the lever, which in turn pumps gas through the lines into the carb. The engine kind of sputters at first and takes a second to come on, but I noticed, while looking through the carb barrel, while the engine is running, that virtually no fuel comes out into the barrel. The only time it does come out is when I give it a little more gas, but it only makes one squirt, then ceases to give more gas. Eventually, the gas inside the engine burns off and it putters out. The gas seems to come out fine when I pump the throttle, but doesn? come out constantly when the throttle is open. I've tried to manually adjust the carburetor, but i've had no such luck. I believe the pump is working fine, even though when I removed it from the old engine, I separated it to find gunked-up rubber from a previous hose, stuck inside the holes and along the walls of the pump. I cleaned it out thorough, and it should work fine, because fuel is reaching the carb, but it just doesn? seem to have a continuous drip/flow of gas. I haven? yet tested to see the amount of pressure coming out of the fuel lines, but it is coming out of the carb, which means it is reaching it. It seems weird that no fuel would come out into the barrel as the engine was running; could it be a fuel pump problem, a carb problem, or a vacuum problem? Someone said something to me about a main orifice in the carburetor not operating, but I'm not sure what that is. Is it possible to purchase a 2-barrel Holley carburetor from a local parts store for marine application?
The timing is quite accurate and shouldn? cause this problem, the vacuum hoses and PCV valves are new. The carb is new/rebuilt, and the fuel pump is ?efurbished? Any information would be much appreciated.
04-22-2004, 10:29 PM
The squirt is from the accellerator pump ( a plunger ) in the carburator. There apparently is little or no fuel getting to the jets in the carburator barrels. Either they are clogged or the needle valve is stuck or the float is stuck or improperly adjusted. If the problem is caused by varnish and/or dirt from your fuel system then you're stuck with a carburator rebuild. If it was an error by a respected proffessional he likely would be glad to make it good. If the guy thinks he's great, but isn't a pro you're stuck with a carburator rebuild. If you ever need carburator work done ALWAYS go to the guy who's done hundreds of rebuilds. This is where I don't mess with shadetree mechanics.
04-23-2004, 12:03 AM
" Thanks Eddie! Unfortunately, I am the guy who thinks he's great. hah! I purchased the Holley carb and fitted it myself. I took the boat to have the engine timed, and everytime they turned it on, it shut off after that minute period. The two squirters that spit fuel into the barrels do work, only when I push on the accellerator, but other than that, they dont do anything else. If you dont mind me asking, what is that hose looking piece that curves down, directly above the first flap? Is that supposed to release fuel as well? If so, it doesn't. There are two lines running to my carb, one is a rubber fuel hose and the other is an aluminum gas line. The rubber hose is new, but the fuel line is the from the old engine. I'm not sure if it needs to be replaced, but it sure wouldn't hurt. Where is the needle valve or the float, if you dont mind me asking?
04-23-2004, 01:10 AM
As the float rises the lever it is attached to pivots pushing the needle into it's seat closing off the flow of fuel coming into the carburator. This is located under the cover of the bowl. You might check the metal fuel line for clogs by blowing it out. One other thing. If the vent to your gas tank is clogged, the vacuum created will stop the flow of fuel. You can break the vacuum by opening the fuel filler cap. Always be careful when replaceing items in the fuel system. Use new gaskets, Coast Guard approved fuel line, and double check for leaks afterward.
04-26-2004, 05:41 PM
1. If the engine is running you WILL NOT see any fuel entering the body of the carb. As Eddie stated you only see the jet when you throttle up due to the accelerator pump.
2. The bent tube you describe is the bowl vent. On marine carbs it bends completely down, on automotive it is straight. No fuel comes out of this tube.
The Holley is quite simple to adjust. The idle mixture screws should start at 1 1/4 turn out. The fast idle setting should just crack the butterfly's about 1/16 inch. Install a $20 fuel pressure gauge. About 5-7 pounds is correct. Start the engine, remove the screw on the side of the bowl to observe fuel level. Adjust the float on top of the bowl to just get the level even with the bottom of the screw hole. Adjust the fast idle to proper setting, adjust the idle mixture to gain RPM and reset the fast idle.
If it still stalls, check the inlet screens where the fuel line fittings connect to the carb. Your used pump might have clogged them up.
It is not unthinkable to have a bad carb, even new or "rebuilt". Try swapping one from another boat or even a automotive to test, but don't run it due to its non-marine attributes. "
03-06-2006, 03:32 PM
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03-06-2006, 10:42 PM
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