Mercruiser 5.0 dies while idling - no fuel from line

[Kman530]

New oil pressure switch came in and I changed it. Ran the engine for about 15 minutes on a hose without a problem. Then...
I turned the engine off and started to clean up my tools which took about 10 minutes. Turned the water back on and fired it up. Ran for about 30 seconds, coughed and died. Cranked and it fired up but stumbled and died. Cranked again and it wouldn't start. Changed the fuel filter and checked the oil. The oil was about a quart low, just above the add line so I topped it off. Cranked again and it ran but was running really rich as black smoke was coming out of the exhaust and I had to run at high idle (about 1,000 RPM's) to keep it running. That cleared up and it idled normal without the excessive rich mixture after about 5 minutes. Shut it down and waited another 15 or so minutes and repeated the same thing with the same results.

Not sure what is going on but whatever it is it only happens after the engine heat soaks after being ran. From a cold start no problem. It's at least starting up and running, but it's extremely rich for about 5 minutes and won't idle then clears up.

Fuel filter was changed today. Carburetor was rebuilt last season. Changed the coil last season to a PerTronix 40011 Flame-Thrower.
Changed the plugs, cap rotor and wires at the start of this season. I did notice the PCV valve is rattling at idle and goes away above idle but I'm not sure if that will cause anything.

This problem first started after the 4th of July weekend. The lake was packed and we hit some pretty hard wake at times going about 25 mph and it seems that right after that weekend I started noticing this issue.

Any help would be much appreciated as I have family coming into town for Labor Day and we already have a lake house booked....

Thanks!

 

[tank1949]

Forgot to mention this is 2150 Bayliner with a fiberglass tank. The fuel filler hose connecting to it is about 1 inch in diameter. I have siphoned gas from the tank before so I don’t think it has anti-siphon but I’ll check. I’ll check both items you mentioned. Just need to find a fuel pressure gauge.
I’m still not sure why it would only happen after it’s hot and not while it’s running from a cold start. One would think it would happen under power and not only after it has been ran and sitting.

some tanks have strainers in the pickup tubes. Pull and examine. Tank may be full of floating crap that settles and then finds pick up tube when demand is high.

 

[Kman530]

some tanks have strainers in the pickup tubes. Pull and examine. Tank may be full of floating crap that settles and then finds pick up tube when demand is high.

Pulled tube this weekend and it was just an open pickup with no screen or anything. Couldn't see anything in the tank. Post #21 has the latest and the issue now is it won't run correctly after warm.

 

[Eric 3.7LX Alpha 1]

Sounds like the carb may have some junk in it. I know you have inline filters, but if there was ethanol gas sitting in it over winter time, it could have caused corrosion in the carb by itself.

 

[Kman530]

Sounds like the carb may have some junk in it. I know you have inline filters, but if there was ethanol gas sitting in it over winter time, it could have caused corrosion in the carb by itself.

I’ve been running non ethanol since the carb was changed last year. It starts and runs fine when cold. Only have the issue after trying to restart when it’s hot.

 

[alldodge]

Fuel pressure is good but fuel line is dry when motor is shut off when warm. The antisiphon valve is working and fuel is not draining back.

If the above statement is true, then its either the pump or the rubber fuel line is collapsing inside

 

[nola mike]

Fuel pressure is good but fuel line is dry when motor is shut off when warm. The antisiphon valve is working and fuel is not draining back.

If the above statement is true, then its either the pump or the rubber fuel line is collapsing inside

I don't know that the fuel line is still dry after the switch replacement?
Sounds now like it's rich at idle, more like some crud in the needle/seat, incorrect float, incorrect mixture adjustment, choke not opening.
OP, look down the throat of your carb at idle, see if it's dripping. Also make sure your mix screws aren't out of whack.

 

[Kman530]

I don't know that the fuel line is still dry after the switch replacement?
Sounds now like it's rich at idle, more like some crud in the needle/seat, incorrect float, incorrect mixture adjustment, choke not opening.
OP, look down the throat of your carb at idle, see if it's dripping. Also make sure your mix screws aren't out of whack.

Correct, after the switch replacement the dry fuel line problem (knock on wood) has been corrected. It’s acting like it’s over rich during idle. I just looked up the instructions for setting the idle mixture and it looks like I need to lock the base timing first. I’ll give that a try and check. I’ll also look into the carb at idle as you recommended.

 

[Kman530]

Fuel pressure is good but fuel line is dry when motor is shut off when warm. The antisiphon valve is working and fuel is not draining back.

If the above statement is true, then its either the pump or the rubber fuel line is collapsing inside

Changed the rubber fuel line when I did the antisiphon. There is definitely fuel getting to the engine now. It’s running really rich at idle. Not sure why the issue only comes up after the engine is shutdown after its hot.

 

[alldodge]

ok, the carb is flooding the motor.

 

[Kman530]

ok, the carb is flooding the motor.

I’ll pull the spark arrester off and look inside to see if it’s dripping or anything. Should I pull the top of the carb off and look into the bowl? Not sure what’s all involved in that.

 

[alldodge]

Look inside the bowl if you see the carb dripping. My guess it is dripping, and then need to find out is it the needle, incorrect float setting or float is to heavy

 

[tank1949]

I don't know that the fuel line is still dry after the switch replacement?
Sounds now like it's rich at idle, more like some crud in the needle/seat, incorrect float, incorrect mixture adjustment, choke not opening.
OP, look down the throat of your carb at idle, see if it's dripping. Also make sure your mix screws aren't out of whack.

Dripping????? GM Quad-jets were bad about dripping. I had a couple that I could never get to stop, after rebuilds from so-called experts. I replaced and problems ended. I'd usually know if carb was dripping by the increase in gas millage.

 

[Kman530]

Look inside the bowl if you see the carb dripping. My guess it is dripping, and then need to find out is it the needle, incorrect float setting or float is to heavy

Will do first thing tomorrow morning. A thunderstorm rolled in so I can't get access to it tonight. I'll report back what I find!

 

[tank1949]

I’ll pull the spark arrester off and look inside to see if it’s dripping or anything. Should I pull the top of the carb off and look into the bowl? Not sure what’s all involved in that.

There is an unorthodox trick an old mechanic taught me concerning Quads. Manually advance throttle with you hand while covering carb's butterflies (airhorn) with other hand. Motor will try to die. So, you may have to advance considerably. Do this a few times. Hopefully, it will suck the small stuff through carb. Or, your hand. It won't! Just be careful. Most of us allow carbs to set up and craps accumulates inside. If you let carb sit for several months, crap should be expected. Good luck!

 

[crazy charlie]

Charlie, Thanks for the recommendation but I don't believe my carb has a filter. I replaced the carb last season and I just took the fuel line off and looked into the bowl and didn't see a screen or anything. I do have a spin-on fuel filter that I replaced.

Post a pic of the carb where fuel line enters the carb.Thats where the filter typically is.Not much bigger than a thimble with similar shape minus the taper .Charlie

 

[Kman530]

There is an unorthodox trick an old mechanic taught me concerning Quads. Manually advance throttle with you hand while covering carb's butterflies (airhorn) with other hand. Motor will try to die. So, you may have to advance considerably. Do this a few times. Hopefully, it will suck the small stuff through carb. Or, your hand. It won't! Just be careful. Most of us allow carbs to set up and craps accumulates inside. If you let carb sit for several months, crap should be expected. Good luck!

I like it! I’ll give that a try in the morning first thing!

 

[Kman530]

Post a pic of the carb where fuel line enters the carb.Thats where the filter typically is.Not much bigger than a thimble with similar shape minus the taper .Charlie

Will do. I didn’t take the actual fitting off but just looked inside and didn’t see anything but looking at the rebuild manual I see what you’re talking about. Small little screen ‘rock catcher’

 

[Kman530]

Alright, it does have a little screen at the carb. You guys where right! It was clean with only a small speck of something that I cleaned out.
As for the carb, at first I didn’t see any dripping and it was running good. I advanced the throttle a few times to 1500-2000 RPM and back to idle. Started to cough so I looked into the carb and sure enough fuel was dripping from the ventri cluster. I advanced the throttle to 2000 RPM and that cleared up and idled normal. After a few more minutes it started to cough again at idle and again, fuel dripping. Do you think the needle/seat might have some junk in it? I did try to hand over the carb trick while running and it seemed to improve the issue and went from dripping from both to only one every few seconds.

 

[Kman530]

Video of it dripping. Tried my best…