Expert Troubleshooter Help needed!

[Finney]

I'm running a Merc 260, and the first day on the water this season it fired right up. We took it out and all was well, except the fuel line was clogging. We went out again after adding fuel treatment, then the engine choked out when our rpm's were over 4000. We checked for vapor lock, and it wasn't a problem. We figured bad gas, and now we've replaced the fuel. Now i'm having problems starting it. It has an automatic hot air choke and I think it may be bad. With the choke attached, when we turn the engine over the barrels stay closed and it doesn't start unless we give it full gas on the throttle. When we disconnect the auto choke the barrels open and it starts right up. So here are where the questions start. Is the choke supposed to be open or closed when you start it? Does anyone else have other clues as to what may be going on with this thing? Please help.<br />-Gerry

 

[Boatist]

Re: Expert Troubleshooter Help needed!

Finney<br />I do not know your motor but most non EFI chokes use engine heat or outdoor heat to open the choke. On a cold day the choke will close, when the engine starts it uses heat off the engine or manifold to heat choke and cause it to open. <br />On a hot day should not close all the way. Most chokes I have seen are adjustable, some just turn the houseing to adjust where will open faster or not close at all on a hot day. However some you have to been linkage to adjust.<br /><br />With the engine off and cold pull the flame arester and open the throttle about 50 percent. Now check the choke butterfly and see if it moves free. If it does then I would adjust Leaner in your case. If it is stuck then try and find out what is holding it and clean until it is free as can not work unless it is free. If you get the manual it will tell you how to adjust. Sorry I do not know your motor so could tell you how to adjust your unit.<br />Good Luck

 

[anesthes]

Re: Expert Troubleshooter Help needed!

For now i'd disconnect the choke and hold it open with mechanics wire until you rules out other issues with the motor.<br /><br />-- Joe

 

[magster65]

Re: Expert Troubleshooter Help needed!

Does the choke come off after it's warmed up? If not it sounds like you have a bad connection on your choke stat (or it's failed). Your choke should be open an 1/8" +/- while you're turning over.

 

[bernieb]

Re: Expert Troubleshooter Help needed!

Finney if you have an outboard type gas tank laying around 6 gal or so ,rig it as if you're replacing the onboard tank, secure with bungy cords,have fire extinguishers handy when trouble- shooting on the water.If engine runs fine the pick-up tube is sucking up on occassion some debree or the check valve (one way flow)brass which collects trash that mounts on top of onboard tank where hose connects.Assumming you have a four barrel rochester, have someone look down the larger two barrels as you attempt to open her up ,look for gas as to what happens.Change fuel/water separator check sm filter at carb and make sure it's not reversed.

 

[Finney]

Re: Expert Troubleshooter Help needed!

Thanks for the help guys, i'll play with it this weekend. I think magster has it right with the linkage being bad. The Barrels don't move right now when we are trying to turn it over, so I think it makes sense that the engine is starved for air as it's starting. Would you guys reccomend replacing it with a brand new hot air choke or a electric choke?<br />-Gerry

 

[Yepblaze]

Re: Expert Troubleshooter Help needed!

Change the fuel filter(s)<br /><br />Make sure to check and see if it has one of those ones inside the carb (also). And if it does make sure you use the right wrenches. If the fuel line is kinked from someone elses feeble attempt to access the carb fitting replace the fuel line also.

 

[Bondo]

Re: Expert Troubleshooter Help needed!

Sounds to me like your engine is Starving for fuel, not Air....

 

[horndog]

Re: Expert Troubleshooter Help needed!

as bondo said, its starving for fuel. The choke plate should be closed when starting a cold engine. <br /><br />Try this...<br /><br />With the engine off, pump the throttle lever while you or somebody else looks down the carb with the choke plate open, you should see fuel squirt into the barrels. If not two streams then you have a bad accelerator pump. <br /><br />What kind of carb is on your motor?

 

[Bondo]

Re: Expert Troubleshooter Help needed!

You say you added gas treatment, then changed the gas altogether... Did you also change all the filters ???? How much sh*t is In the Carb.???? How plugged up are the jets ???<br />Which carb do you have ????<br />Your choke is working Perfectly....

 

[Finney]

Re: Expert Troubleshooter Help needed!

It's a 4 barrel quadrajet on there. I changed the fuel filter and nothing else. The fact that there is another filter built onto the carb is news to me. I'm going to look into changing that filter as well. I don't know how to check the jets in the carb, but right now once we get it started it runs just fine and normal. On reccomendation from others we are going to go to electronic choke and electronic fuel pump. I guess we'll go from there. I really appreciate all the help on this. Hopefully she'll purr like a kitten soon!<br />-Gerry

 

[Boatist]

Re: Expert Troubleshooter Help needed!

Finney<br />If your motor runs fine with the choke held open or disconnected you do not have a fuel supply problem. Your problem is the choke is misadjusted or sticking and your engine is flooding. Again with the engine off push the throttle forward to about 1/2 and check the choke butterfly. Make sure it is free where you can open and close. If it is stuck then that your problem as should be free with throttle foward. If it is free then must determine if adjusted right. As engine warms up should open all the way up. On a cold day with a cold engine the choke should close at least part way. Again with the engine off try advancing throttle all the way. at full throttle the choke should be forced open some this is so can start a flooded engine with the choke closed.<br /><br />When you start the engine the choke should start to open and with in 5 minutes should be all the way open. Lots of ways to do this but since I do not know your engine can not tell you what your has.<br /><br />Some use vaccum off the manifold to open the choke part way as soon as engine starts. Choke usually colsed by a coil that will open up the choke when the coil heated. Coil can be heated by a tube going to the exhaust manifold. Use engine vaccum to suck hot air thru tube and up to heat the coil to cause choke to open. Other just mount coil down near the exhaust manifold and heat it by being close. Anyway the choke should open with in 5 minutes all the way unless it is stuck maladjusted or the coil is not getting heated or it rusted and stuck.

 

[Finney]

Re: Expert Troubleshooter Help needed!

OK, after further review here is where I am. The choke is fine as far as I can tell. I decided to put a clear fuel filter on the line between the pump and the tank to be able to monitor fuel & flow. We went out and all was fine for about a football field, then it started starving for gas. We could Cruise at 2000 rpm's and it would never die. As soon as we go over, it dies on us. I watched the fuel filter and after 2000 rpm's the engine starts demanding more fuel coming from the line, and the filter starts to empty of gas. It gives me the idea that were not getting enough vacuum from our fuel pump. On a Merc 260hp what should psi be? Would an electric fuel pump be a better option at this point? I think I've narrowed it down to this point, but the fuel pump on it is really new so It makes me question whether it's the right one or not. All help appreciated!<br />Mercruiser 260 horsepower 1989<br />350 cubic inch block<br />Rochester Quadrajet Carbarator 650 cfm

 

[akriverrat]

Re: Expert Troubleshooter Help needed!

i would work my way back from fuel pump checking all lines and filters for obstructions and air leaks. including tank vent(easily checked by opening cap while running). fuel pumps really aren't very good at pulling.

 

[Finney]

Re: Expert Troubleshooter Help needed!

Already tried it without the gas cap. Checked all lines and they are clear. I'm just wondering how to get a stronger fuel pump, without going overboard!

 

[Boatist]

Re: Expert Troubleshooter Help needed!

Finney<br />Put a fuel pump pressure guage on it and see what you get. Need about 4 Lb of pressure and most new pump are 6 to 8 pounds. Specifications in my book for a V8 are 5 3/4 - 7 PSI at idel and pumps one pint of volume in 45 sec or less at idle. Be carefull testing as gas very danerous. On fuel pumps I like new not rebuilt. Make sure all filters clean and back blow line to tank.<br />Good luck.

 

[conimicut1]

Re: Expert Troubleshooter Help needed!

my first point is to stick with a mechanical pump, they are fine for carbs. retrofitting an electrical needs alot of safety wiring issues, like if the engine stops running and the pump stays on, your bilge will the get filled with gas. The newer systems with electric pumps as origion equipment have all that backup stuff built in and they usually are fuel injected too and need the higher pressure to operate. In fact, too high of pressure is just as bad as too low for a carb, you'll force off the needle/seat and flood the engine. <br /><br />Make sure the choke is open after warmup. there are two sheet metal flaps on a Q-Jet, the smaller one is the choke it must be all the way open when warm, the bigger one is for the secondaries, don't mess with them for now. <br /><br />Check pressure, looking at filter is not conclusive. Make sure you have a new filter inside the carb, be careful taking off and putting on the big nut and fuel line nut, use flare wrenches for the flare fuel line fitting. <br /><br />if all this is OK and still have problems, rebuild carb with new float or get a rebuild ( maine carb!). poor float or float height will cause problems under load/RPMs.

 

[Finney]

Re: Expert Troubleshooter Help needed!

I always like happy endings so I'll give you guys mine. After draining 45 gallons of gas, pulling apart fuel lines, fuel pumps and almost rebuilding a quadrajet, I pulled the fuel inlet out of the gas tank. To my amazement this thing comes apart and on the inside is a screen. The whole inside of the tube was full of jelly, or as I like to call it "Vaseline." We were lucky to get just a little gas to the engine. Well, I wanna thank everyone on here for all their wonderful advice and help. I think I've officially fixed everything so I don't think I'm ever posting for help again. That is unless everything starts falling apart all over again, but at least this time i'm ready for it! But seriously guys thanks for all the responses! <br />-Gerry