Mercruiser 4.3LX - No Start

[tony203040]

Hello everyone,
Thank you in advance for reading my post. First time post for me on this forum...any advice will be greatly appreciated. Here are the details of my issue and my troubleshooting steps.

Equipment Details: 1995 Mercruiser 4.3LX (GM) with 4 Barrel Carb (Alpha One Gen II Outdrive).
Engine SN: 0F296848

1. Engine does not start
   1. Engine will rotate during key turn, but will not start. Initially the “turn” is very slow and slowly ramps up to a speed I would expect to see the engine start. Potentially bad battery, but I only attempt to start while jumping from a truck.
   2. Verified Spark
      1. Checked input to distributor cap ~12VDC.
      2. Checked output of one spark plug wire; reaching 12VDC (as expected)
   3. Fuel Checks
      1. Checked carburetor and cannot see fuel spray from the jets.
      2. Manually added gas to carb, engine started for a quick second.
      3. Found damaged (dented) fuel pump; replaced fuel pump as a precaution.
      4. No change in symptoms.
      5. Disassembled carburetor and cleaned internals. Then replaced the cable connectors at the battery terminals.
      6. Engine would then start; but with a slight roughness and varying idle.
      7. Go on vacation for 10 days; engine no longer starts when I return (same symptoms as original problem).
      8. Replaced oil pressure sender. Now, I can hear the fuel pump running…not sure why I didn’t hear it before.
      9. Disconnected fuel line from carb input; attempted to start; fuel is DEFINITELY flowing to the carb (from the pump).
      10. Reconnect fuel lines; looked in barrels of carb; still not seeing any spray.

At this point, I’m considering a carb rebuild kit, but wanted to make sure I wasn’t missing or overlooking something. Any chance a battery could be so bad, that even jump starting could cause this issue? Still doesn't explain the lack of fuel spary in the barrel, but I'm losing focus at this point due to my pure frustration...haha. Thanks again, everyone.

-Antonio

 

[Bondo]

Reconnect fuel lines; looked in barrels of carb; still not seeing any spray.
At this point, I’m considering a carb rebuild kit,

Ayuh,..... Welcome Aboard,..... No doubt yer biggest problem is the carb,....

Get a kit, 'n make sure it comes with the acc. pump too,....

 

[Rick Stephens]

As bondo said, absolutely sounds like fuel problem. Start with carburetor kit, do it completely making sure every passage is perfect, float level is perfect, throttle pump is new with check balls and pump passages perfectly clean. Only one way to do a carburetor rebuild - all the way. Clean it, run a fishing line or wire through it, clean it some more. Triple check it. The two words that matter: perfect and clean.

Also do not forget to pull the fuel water separator and dump its contents into a baggie or glass jar, look for evidence of water and foreign materials.

Next time I would check the output of the fuel pump before just replacing it. '95 has an electric I think. Make sure it is getting voltage from the starter during cranking. Make sure your replacement is putting out now. You can slip the fuel line into a soda bottle and power the pump to confirm.

Rick

 

[tony203040]

Thank you, gentlemen! In the interest of time, I've decided to have a marina do the carb rebuild. I will update the Post as soon as it's finished.

Thank you!