I don't think any gas is getting to my carb

[MikeDobbs]

Hi everyone- if you've been following my saga I believe I have got the electrical sorted out, and I've moved on to starting the engine. Bolted on the newly rebuilt carb today, and she turns over, and started to catch with a little starter fluid, but never fired all the way up.

(Mercruiser 3.0lx by the way)

I know the carb is supposed to pump gas with the throttle once there is pressure from the fuel line, but even after a fair amount of cranking and pumping of the throttle I could not hear any gas being pumped into the carb.

I suspect there is no gas making it's way to the carb. What should I do? I saw another post on the forum where someone recommended that the person prime the fuel pump, but I'm not sure how to do this.

Thanks in advance : )

 

[Eric 3.7LX Alpha 1]

You can squirt a little gas down the throat of the carb, and then give it a couple of good pumps on the throttle.

I'll take a plastic cover from a can of spray paint and use it to measure out about a half cover worth of gas and dump it down the carb then a few good pumps and give it a go. If it ain't running from not getting gas, it's gonna fire right up. If it still isn't getting gas, it's only gonna stay running for a few seconds until that half cup worth is burned..... it is better for the engine than the starting fluid.

Getting the engine to run for a few seconds at a whack will get a mechanical fuel pump primed if that's the cause.

Just a word of caution... anytime the flame arrestor isn't on the carb, and your trying to start it or even if it's running in the driveway with the flame arrestor off while working on it...... I make sure no one is standing over the carb you never know... even if it's running like a top.... my face stays away from the top of the carb...

 

[MikeDobbs]

OK- I will try that tomorrow, and thanks for the tip about staying clear of the carb when running

Two Questions:

1st - When you say dump it down the carb, does it matter where? Or just through the opening where the flame arrestor would go? And when you say pump it a few times, do you mean that moving the throttle should pump the gas I just poured in somewhere else?

2nd - I noticed that when I look down the carb the holes at the bottom are basically closed when the throttle is just forward enough to where it would go into gear. Should the throttle be open more than that when trying to start the engine? Or is this the correct amount. To me, it looks as though the openings are basically closed, so I'm not sure if the engine will get enough air.

 

[Eric 3.7LX Alpha 1]

Question 1: Yes the opening in the middle where the flame arrestor is.... I try and aim it down the primaries.... which would be the smaller set of openings (towards the front of the carb if it's a 4 barrel... which will be closed until you pump the throttle.

Pumping the throttle will let gas spill from the carb into the intake manifold and eventually down thru the intake valve into the cylinder so it can be ignited.... and also set the choke closed if it is open.

You could also pull the spark plugs and put a little gas in each hole and put the plugs back in.. and avoid the carb all together, but it's kind of a pain with too many cylinders.... but with a small engine, like a lawn mower good way to troubleshoot... if it's not getting gas for any reason. a little gas in the cylinder thru the spark plug hole..... is instant running.. but if it continues to not get gas it will only run until that gas you put in is burned off.

 

[MikeDobbs]

HAHA! Worked like a charm. Thank you so much- I was worried I might have a more serious fuel delivery issue.

For the record- I dumped about a half spray can top worth of gas into the carb, pumped 3 or 4 times, and turned it over until it fired up. It ran for just a second or two and stopped. I got off the boat, got a little more gas in my container, dumped that down the carb, and started it up again. This time, after running for a second or so, it started to die out, and I gave a pump of the throttle, and it kept running!!!

I let it run for a minute or so before shutting it down. Waited about an hour or so and put the flame arrestor etc. back on the carb. Went to the help, pumped the throttle, cranked about 5 seconds- pumped the throttle again and she fired up and kept running!

If you don't know- I purchased this boat NOT running- I ran a compression check and the price was right so I took a chance, needless to say I'm very excited to have her running : )

Thanks again for the help

 

[Eric 3.7LX Alpha 1]

Nice! glad to hear. :thumb:

Don't forget to have water running thru the muffs on the drive when it's running, it only takes a few seconds of running dry to effect the rubber impeller in the drive.

 

[MikeDobbs]

Thanks for the tip- I actually have the leg off right now to do the bellows and rebuild the impeller- so I just tied my hose up to the water inlet hole on the gimbal while I was running it

 

[Eric 3.7LX Alpha 1]

That works just fine. Good luck with the rest.