Logo
FULL SITE MENU

Engine wonbt turnover

W

wet_wonder

Contributing Member
"Hi,
I have a Mercruiser inbo

"Hi,
I have a Mercruiser inboard 351 Windsor 233HP. It won't start. The symptom is that its not getting fuel. I pulled the spark arrest and watched the carb spray during ignition. When I turn the ignition and accellerate, it sprays for about half a second and the motor kicks, but then the spray stops and fuel trickles/bubbles out and the motor stalls. So whenever I hit the accelerator, I get a momentary spray, which stops and turns to a trickle. My guess is that when under power there should be a continuous spray of fuel from the carb, it's volume relative to the accelerator. And that the trickling fuel is some type of failure. Can someone please advise on what the problem is here?
Thanks, Dave"
 
"what you are seeing in the ca

"what you are seeing in the carb is normal operation. The accelerator pump squirts extra gas in when you pump the throttle. After that 1 shot, the venturi effect of the carb draws the fuel in with vacuum- a carburetor doesn't spray fuel in. Only fuel injection systems do that.

Just for future reference, "turn over" means rotate. Your engine is turning over just fine by the sounds of it."
 
"Ok thanks, so after the motor

"Ok thanks, so after the motor kicks from the intial spray of fuel, it dies. The only way I can keep it running is to pump back and forth on the accelerator, revving it, to maintain the spray. If I stop revving and just hold the accelerator forward, the motor dies. Any thoughts? I was thinking maybe it was water in the fuel perhaps."
 
"DAve,

What is the choke b

"DAve,

What is the choke butterfly on the top of the carb doing during this time? If this is a cold engine, it is supposed to be closed so that extra fuel is pulled into the engine to make it rich enough to start.

I'm assuming this is an honest-to-goodness carburetor, not a throttle body-type fuel injection system. Is that true?

Big picure, assuming the engines has been shut of for more than a few hours, it needs to have extra fuel in there to get it lit off and running.

Pumping the throttle is giving it a "pump shot" from an accelerator pump. And you say the engine likes that, so it sounds like if you have a carb, you need to figure out why you are not getting choke operation. If you have Fuel Injection, the problem starts to sound like fuel pressure issue...

Provide more details. This sounds pretty basic. I'll bet the experts here can help you get it solved."
 
"Based upon what I am decipher

"Based upon what I am deciphering, you need to rebuild the carb; idle circuits are plugged w/varnish.

IF the engine starts and then dies when you let go of the key, I would say the coil ballast resistor or wire is open."
 
"The motor is a 1975 mercruise

"The motor is a 1975 mercruiser, with a standard carb. Last rebuild 2004. I had a suggestion here at the marina that there might be a varnish clogged channel in the carb, and to send the carb out to be redone. Does that sound right? Any other thoughts?"
 
"If you think the carb is the

"If you think the carb is the right direction for this problem, I'll drop it off at a very reputable marine carb place near me. I'll let you know how it works out. Thanks for all of your help."
 
I pulled the fuel hose from th

I pulled the fuel hose from the carb to check the fuel pump flow - and captured some of the gas in a jar to check for water. There was one part gas floating on top of 4 parts water. So then I syphoned two gallons from the bottom of the fuel tank and it started up and ran w/o problem.
Thanks everyone.
 
Back
Top