Post Carb Rebuild Starting/Running Problems!! - HELP!!

[djfam]

OK. First of all. Thanks in advance for any help you can provide. I just rebuilt my Rochester 2bbl carb on my Mercruiser 470. The carb had not been cleaned since I got the boat in October and the old owner gave me the carb rebuild kit. I did all the work myself and took a good day and a half to take the carb apart, clean it and rebuild it. I followed the instructions very closely and felt confident that i had done everything right. Today, I went to start up the boat on the muffs and it had a hell of a time getting going. I eventually primed the carb with a little fuel and it started and then died. I got it running for about 2 minutes then it died. I can't keep it idling at all for more than a few seconds so I think the fuel may not be getting through. Help me understand what I may have missed here! I replaced the fuel water separator and the fuel line as well as part of the rebuild. The gas is fresh. I'm not sure about the choke or how to test it, but I'm not sure if that is the problem. When I followed the directions for the re-build, I also put a check ball in where there was not one when I removed the carb. The directions said to put it in, so I did. Perhaps that is the problem. It was the check ball that sits below the pump return spring. Should it be there? HELP! I'm looking forward to reading your responses.

 

[JCF350]

Re: Post Carb Rebuild Starting/Running Problems!! - HELP!!

Carb destructions always show where to place every part in the kit. Trouble is
that particular carb may not use every part in the kit. Go back and remove the check ball that wasn't there to begin with and retry.

 

[fixb52s]

Re: Post Carb Rebuild Starting/Running Problems!! - HELP!!

It could be a number of things. As for that ball, I had one too and also put it in under a screen. There was also another ball in one of the passages with another spring and a retainer under the metering horn. They would open and close whenever the acceleration pump is moving to either draw in or push out fuel. In your case, the ball probably should be there, and this should not affect idle, just acceleration if it was incorrect. To check for sure, if the pump cavity is open on the side to the fuel bowl, the ball should not be there. If it is the older design and does not have this cutout, then it should be there. The best way to tell is look up the car number in the Mercruiser manual.​

Things to check:​

1. Is the fuel pump putting out proper pressure? Disconnect it from the carb, put the line in a container and crank it. You should get a strong flow of fuel.
2. Does your pump have a filter? Most do, and they can get dirty.
3. Is the idle mixture screw turned out the proper amount? 2 turns is a good starting piont.
4. Did you properly adjust the float? If you put the spring in the needle assembly, the adjustment is different than the solid link when measuring for float closed. You also have to check the float level when it is hanging. The little ruler that comes with the kits is in 32nds of an inch. If your measurement is say, 9/16, ensure you properly read the ruler. Measure the distance from the flange with the gasket installed.
5. Did you get the old check balls out when you stripped down the carb? A lot of times, they get corroded in the passage and will not come out. This could explain why you maybe did not see one come out.
6. Are ALL the passages clean? On the rochester, there are a few passages that run at the bottom of the throttle body that get plugged rather easily. It is very important to get them completely cleaned out, and blow them out with compressed air.​

Go back and check. Good luck chasing it down.​

 

[djfam]

Re: Post Carb Rebuild Starting/Running Problems!! - HELP!!

Guys, thanks for your responses.

JCF350- I will try it with the check ball out. Based on the descriptions, I am now pretty sure that it should not be there even though the instructions said it should be.

fixb52s-I will try to run through your list of items each day this week after work. I'll let you know how it goes.

One other question - I replaced a tube (clear plastic) that runs from a fitting at the top of the carb to a similar fitting on the fuel pump. Should that be filled with gas or should it be empty? For some reason I thought it was a vaccuum line, but I may be wrong there. The old one was all crudded up and nasty, so I just got rid of it. The new line is obviuosly perfectly clean, but I did not see any fuel in it. If it needs to have fuel in it, should I prime it? Perhaps I have some kind of air lock going on? Thoughts?

 

[fixb52s]

Re: Post Carb Rebuild Starting/Running Problems!! - HELP!!

No fuel here, just vacuum. If you do find fuel, your fuel pump diaphram would be leaking.​

 

[djfam]

Re: Post Carb Rebuild Starting/Running Problems!! - HELP!!

fixb52s - thanks for that clarification. I was starting to think the fule pump had gone bad as well. For now, I'll concentrate on the carb.

If anyone could also explain to me (or send me a diagram) of the linkage for the throttle and choke mechanisms, that would help. I took pictures of every step i took during the rebuild for cross referencing EXCEPT the linkage. I'm wondering if I have something hooked up wrong with the linkage? Just a thought!

 

[djfam]

Re: Post Carb Rebuild Starting/Running Problems!! - UPDATE!!

Re: Post Carb Rebuild Starting/Running Problems!! - UPDATE!!

OK, so I am a week behind schedule but I finally got time to get the carb off the motor today. When I got it off, I noticed that the small filter where the fuel enters the carb was halfway filled with a dark, sandy, dirty looking material!! Holy S**t!! where the hell did that come from!??! I just got done rebuilding this carb and the boat has not been run since so it obviously came from somewhere in the fuel system before the carb when I was cranking it over last week. I disco'd the line from the filter to the carb and that seemed to be clear of any blockages. Other than replacing the fuel lines, what else do you suggest I look at? By the way, I can look inside the tank from the fuel sender location and it looks to be fine - no junk floating in the fuel in the tank. Suggestions???? Fuel filter perhaps? can those be rebuilt?

 

[Don S]

Re: Post Carb Rebuild Starting/Running Problems!! - UPDATE!!

Re: Post Carb Rebuild Starting/Running Problems!! - UPDATE!!

Junk floating in the gas won't be the problem, the problem is the water, crud, crap and corrosion that sinks to the bottom of the tank and gets picked up by the pickup tube. (which obviously doesn't have a screen on it anymore)
Now, to get the water out of the tank, try this.
First, head to NAPA and get a cheap electric fuel pump. Make and model doesn't make any difference. Pickup some fittings for the pump so you can attach some 1/4" ID clear tubing to both ends of the pump. Then get you a couple of feet of copper tubing that will fit tight inside the clear tubing, and put it on the pickup side of the pump. Make the output hose long enough to go into a container for your junk gas.
Now, put some wires on the pump (a red and black will work..... red for positive and black for negative) put some clips on the end so you can hook to a battery.
NOW, since water always settles to the bottom of the tank, raise the bow of the boat so the back of the tank is lower than the front. The water will also head to the back.
Then remove the fuel pickup tube from the tank (make sure the fuel level is low enough when you start that it doesn't run out of the fitting when you pull it out).
Start your electric fuel pump and stick the copper tube all the way to the bottom, move it around and you will get all the water and leave the gas.

Dispose of the contaminated fuel properly.

After you do all that, install a water seperating fuel filter between the tank and the engine, and replace it yearly and check for water. It's cheaper than rebuilding and replacing the carbs.

 

[djfam]

Re: Post Carb Rebuild Starting/Running Problems!! - HELP!!

Don...do you really think that is it? The fuel is less than two weeks old and the tank was emptied at the end of last year before I filled it with the fresh fuel. I already have a fuel water separator in line ad it was brand new when i redid the carb. I checked it today and it was not dirty or clogged at all.

 

[Don S]

Re: Post Carb Rebuild Starting/Running Problems!! - HELP!!

How did you empty the tank? If you just pulled the gas out of the tank with the bow down, then all the junk would be in the front of the tank.
To many unknown things to say for certain. Don't forget, we can't see, hear, feel, or know and see how everything has been done.
Seen to many people claim they rebuilt the carbs, when all they did was change a few gaskets and call it a rebuild.

 

[djfam]

Re: Post Carb Rebuild Starting/Running Problems!! - HELP!!

Don, I store my boat bow up anyway to let rain drain out if it gets in. I drained the gas tank with the bow as high as possible using a large flow siphon. I got most, if not all of the old gas out. (There may have been a quart or so left over). The gas is fresh. My carb rebuild was a true rebuild and not just a gasket change. Everything was stripped down, cleaned and replacement parts used when possible. All parts sat in carb cleaner for about 24 hours and were air blown out afterwards.

 

[Fishermark]

Re: Post Carb Rebuild Starting/Running Problems!! - UPDATE!!

Re: Post Carb Rebuild Starting/Running Problems!! - UPDATE!!

I noticed that the small filter where the fuel enters the carb was halfway filled with a dark, sandy, dirty looking material!!

I'm with Don on this one - if that is a new filter which was replaced when you rebuilt your carb and now it is halfway full just with cranking you engine over.... I wouldn't know where else to suggest you look for crud except in the tank.

Try doing what Don suggests and see what comes out of your "fresh gas." The new stuff you put in the tank may have simply dissolved the gunk that was left over from the old.

 

[Fishermark]

Re: Post Carb Rebuild Starting/Running Problems!! - UPDATE!!

Re: Post Carb Rebuild Starting/Running Problems!! - UPDATE!!

One more thought is this - if you have access to your tank, try doing the opposite. Put the bow as low as possible for the water, etc to go to the front. Then remove the sender. Depending upon the style of tank you will be able to see inside the tank and determine what you have then. You can also remove the fuel from the front and see if you can see any difference.

 

[djfam]

Re: Post Carb Rebuild Starting/Running Problems!! - HELP!!

OK...Sorry for the late post...I have cleaned the tank and that took the gas tank and it's contents out of the equation. I also removed the check ball from the carb and the fuel is now flowing again. I got the boat started today, so I am back on track...somewhat...When the motor turns over, the gas works it way out of the bowl through a hole at the top near the choke plate. When the motor stops a pretty good spurt of gas is sprayed from this hole. I think the engine is flooding. I can't start it unless I have the throttle open a little. Does this point to a float adjustment or somethinge else? Thanks!!!

(I can post a picture of this hole if necessary)

 

[Coors]

Re: Post Carb Rebuild Starting/Running Problems!! - HELP!!

Float level, or needle/seat has trash in it.

 

[djfam]

Re: Post Carb Rebuild Starting/Running Problems!! - HELP!!

Coors...thanks. I'll check the float level. I did not adjust it after the rebuild because the kit did not have the measurements for my motor/carb combination and I was worried about it. I figured I would leave it the same as it was when I removed it to clean it out. Do you know what the measurement is for a Rochester 2GC on a Mercruiser 470?

 

[ziggy]

Re: Post Carb Rebuild Starting/Running Problems!! - HELP!!

Do you know what the measurement is for a Rochester 2GC on a Mercruiser 470?

i don't know. maybe i missed where ya stated the year and s/n to be sure the info ya get is correct....
ya could maybe get lucky and find yer service manual for yer rig here...

http://forums.iboats.com/showthread.php?t=251571


a service manual would tell ya exactly what the facts are that ya need to know...... confirm proper sm by s/n.....

 

[fixb52s]

Re: Post Carb Rebuild Starting/Running Problems!! - HELP!!

Did you check the filter at the fuel pump? Thre is a large filter in it that could have some old junk in it.​

 

[djfam]

Re: Post Carb Rebuild Starting/Running Problems!! - HELP!!

Ziggy...I have the manual for my motor ('82 Mercruiser 470) and it says nothing about the float drop measurement - actually states to check the kit. The kit did not have the motor listed so I was in the dark. With the fuel flowing too much, I'm guessing I need to increase the float drop measurement to compensate for the bowl being too full..correct? I will probably have to work with trial and error on the measurement if no-one knows what it should be. Maybe Rochester can help? The carb is a Rochester 2GC.

 

[djfam]

Re: Post Carb Rebuild Starting/Running Problems!! - HELP!!

So if I raise the float (decrease the float drop measurement) does that stop fuel from flowing past the needle, or does it increase the flow? In other words, if I make the float drop measurement less, the needle gets pushed up, which allows less fuel to move.

Correct assumption on my part or am I backwards here?