Mercruiser 120 poor starting

[Guffer]

Who winterized the boat ? You as usual ? Or some other place ?
Did you have any hard freezing winter weather ? What state was the boat stored in ? Really cold winter in N J. Did you refill your gas tank after the engine repair ?

Yes, I winterised but head was already off. Based in uk, quite a mild winter. 40 l of new fuel but some treatment in existing fuel too. Issue is no fuel getting to carb. Thinking a blocked breather may also be the issue…..

 

[Guffer]

I hooked up a fuel line with fresh fuel. She ran for 60-90 seconds and then died. Always felt like it was going to peter out. Does this suggest fuel pump is at fault? Was working before winterisation.

When i try to restart she wont fire at all.

Poured a little fuel down carb throat, wont start.

Notes:
- Found i had air leak at sedimentor so am now replacing fuel line from tank to just before fuel pump
- Still have small drip of fuel on carb intake. Will use some permatex 2 on that as have tried 4-5 times to reseat it
- no block in old fuel line i have connected outboard fuel tank to

Any thoughts?

Many thanks

 

[Scott06]

I hooked up a fuel line with fresh fuel. She ran for 60-90 seconds and then died. Always felt like it was going to peter out. Does this suggest fuel pump is at fault? Was working before winterisation.

When i try to restart she wont fire at all.

Poured a little fuel down carb throat, wont start.

Notes:
- Found i had air leak at sedimentor so am now replacing fuel line from tank to just before fuel pump
- Still have small drip of fuel on carb intake. Will use some permatex 2 on that as have tried 4-5 times to reseat it
- no block in old fuel line i have connected outboard fuel tank to

Any thoughts?

Many thanks

May be other issues but if you dribble gas down car and I won’t fire then you are missing spark. This assumes the engine has decent compression

a cheap spark gap tester can be helpful to test strength of spark

 

[Guffer]

Took fuel intake off the carb and cranked it a few times, so dont think it is the fuel pump. Will test the spark plugs next.

 

[Guffer]

Still working through this no starting issue…As the engine has started a few times, and run for a while i thought i had spark.

When i checked spark at plugs and coil lead there was no spark
Assumed the coil was issue and replaced leads at same time….same result
Have looked to clean contacts points and tighten them all
Got spark on coil and cylinder 4
She started up but died quickly
Now no spark at plugs and coil….
Battery reads 13.28v

What have i missed?

Many thanks!

 

[nola mike]

May be other issues but if you dribble gas down car and I won’t fire then you are missing spark. This assumes the engine has decent compression

a cheap spark gap tester can be helpful to test strength of spark

Or you're flooding. Op mentioned fuel dribble somewhere

 

[nola mike]

Still working through this no starting issue…As the engine has started a few times, and run for a while i thought i had spark.

When i checked spark at plugs and coil lead there was no spark
Assumed the coil was issue and replaced leads at same time….same result
Have looked to clean contacts points and tighten them all
Got spark on coil and cylinder 4 View attachment 407393View attachment 407393
She started up but died quickly
Now no spark at plugs and coil….
Battery reads 13.28v

What have i missed?

Many thanks!

Not sure what you did with the points? Replaced, set dwell? You have voltage at the coil?

 

[Guffer]

Or you're flooding. Op mentioned fuel dribble somewhere

Intermittent lack of spark appears to be the issue but with new coil is this suggesting a cable isn’t attached properly or is fouled?

 

[Guffer]

Not sure what you did with the points? Replaced, set dwell? You have voltage at the coil?

I had voltage at coil but now when i put a spark plug in cable from coil to distributor there is no spark.

 

[ESGWheel]

Guffer,
I know this must be very frustrating for you and while I do believe you will ultimately get this running, I have to be frank and suggest that your approach seems to jump around. We started off with what was perceived as lack of fuel to the carb and I am usure if that has been truly solved based on your posts. Example in your post 22 you still have this 30 second run, then stall. Back on post no. 7 this was addressed on how to check this. Here is what post 7 said in part:

• Post checking if good compression and spark etc. from above, and still have the 30 sec. run then stall, check this: post stalling, take spark arrester off so can see down the carb throat. Then pump open the throttle fully in a rapid motion while looking down the throat. Should see a stream of gas from the carb’s accelerator pump. No gas? Bowl is empty. Now with the coil wire removed crank the engine for a bit and then redo that accelerator pump test. If you get a good squirt, then the issue is intermit / poor fuel delivery. And if no squirt, fuel delivery issue.

Did you do that check as indicated?

There are three basic ingredients for an engine to run: compression, spark and fuel. We started with fuel but I feel is not fully confirmed is ok and then you found an issue with spark. While totally possible to have multiple problems, my strong suggestion is to tackle one at a time starting with the fuel. And even if you have fuel going to the carb it does not mean its going into the engine properly. But first step is to validate that you are getting fuel to the carb and the next step is to validate that the carb bowl is getting filled and not running dry or overfilling either of which can cause a stall.

Happy to continue to help but need your follow up on the suggestions with clear communication on what was found. Thanks.

 

[Scott06]

Still working through this no starting issue…As the engine has started a few times, and run for a while i thought i had spark.

When i checked spark at plugs and coil lead there was no spark
Assumed the coil was issue and replaced leads at same time….same result
Have looked to clean contacts points and tighten them all
Got spark on coil and cylinder 4 View attachment 407393View attachment 407393
She started up but died quickly
Now no spark at plugs and coil….
Battery reads 13.28v

What have i missed?

Many thanks!

Have you ruled out the shift interrupt switch as possible spark killer?

 

[Guffer]

Have you ruled out the shift interrupt switch as possible spark killer?

No, not sure how to check this.

 

[Scott06]

No, not sure how to check this.

Not sure which style yours has but you can disconnect the wires to it and see if you have spark . It grounds the coil to momentarily kill the spark so the dog clutch in outdrive can unload and pop out of gear

good to rule out the switch isn’t killing it

 

[Bondo]

No, not sure how to check this.

Ayuh,...... The points, fires the coil, so start with the points,.....

 

[Scott06]

Ayuh,...... The points, fires the coil, so start with the points,.....

True if points haven’t been cleaned and dwell set start there

 

[Guffer]

Guffer,
I know this must be very frustrating for you and while I do believe you will ultimately get this running, I have to be frank and suggest that your approach seems to jump around. We started off with what was perceived as lack of fuel to the carb and I am usure if that has been truly solved based on your posts. Example in your post 22 you still have this 30 second run, then stall. Back on post no. 7 this was addressed on how to check this. Here is what post 7 said in part:

• Post checking if good compression and spark etc. from above, and still have the 30 sec. run then stall, check this: post stalling, take spark arrester off so can see down the carb throat. Then pump open the throttle fully in a rapid motion while looking down the throat. Should see a stream of gas from the carb’s accelerator pump. No gas? Bowl is empty. Now with the coil wire removed crank the engine for a bit and then redo that accelerator pump test. If you get a good squirt, then the issue is intermit / poor fuel delivery. And if no squirt, fuel delivery issue.

Did you do that check as indicated?

There are three basic ingredients for an engine to run: compression, spark and fuel. We started with fuel but I feel is not fully confirmed is ok and then you found an issue with spark. While totally possible to have multiple problems, my strong suggestion is to tackle one at a time starting with the fuel. And even if you have fuel going to the carb it does not mean its going into the engine properly. But first step is to validate that you are getting fuel to the carb and the next step is to validate that the carb bowl is getting filled and not running dry or overfilling either of which can cause a stall.

Happy to continue to help but need your follow up on the suggestions with clear communication on what was found. Thanks.

Fuel flow was previously fine but i have had to change fuel line to incorporate a fuel separating fuel filter.

On finding there was no spark it seemed logical to me to follow up on this to establish why that’s happening. Clearly not.

I have redone the fuel test and it’s not getting to the carb now.

 

[ESGWheel]

Thanks for the follow up and explanation. In spite of other potential issues, suggest focus on the fuel issue until 100% resolved.

For your statement “I have redone the fuel test and it’s not getting to the carb now” what exactly does that mean? Let me explain what I am driving at / info that is needed:
1. Did you disconnect the fuel line at the carb and crank the engine and observed no fuel coming out of the line?
- Or -
2. Did you look into the carb and advance the throttle and observed no squirt of fuel from the accelerator pump?

To continue to analyze the issue, need to know exactly what you did. Test No. 1 (if no fuel) would result in test No. 2 also not having a squirt. However, if only did test No. 2 it does not mean that no fuel is getting to the carb > it could be a failed accelerator pump or problem with the float. This is why your detailed communication back is critical for us to help.

So please explain what test you did to determine no fuel to the carb.
Thanks!

 

[Guffer]

Thanks for the follow up and explanation. In spite of other potential issues, suggest focus on the fuel issue until 100% resolved.

For your statement “I have redone the fuel test and it’s not getting to the carb now” what exactly does that mean? Let me explain what I am driving at / info that is needed:
1. Did you disconnect the fuel line at the carb and crank the engine and observed no fuel coming out of the line?
- Or -
2. Did you look into the carb and advance the throttle and observed no squirt of fuel from the accelerator pump?

To continue to analyze the issue, need to know exactly what you did. Test No. 1 (if no fuel) would result in test No. 2 also not having a squirt. However, if only did test No. 2 it does not mean that no fuel is getting to the carb > it could be a failed accelerator pump or problem with the float. This is why your detailed communication back is critical for us to help.

So please explain what test you did to determine no fuel to the carb.
Thanks!

Thanks for all your help.

I did test 2 this time. I can try test 1 tomorrow.

Re the float - when I rebuilt the carb I put the float back in as it was. There was more than one option re the gasket in that area so i used the one that was similar to what has been there before. In the pic - the gasket I used is like the one on the left rather than the one on the right.

 

[Guffer]

True if points haven’t been cleaned and dwell set start there

Done this now.

 

[Buster53]

I haven’t read all the posts, but…
has anyone suggested the idle control valve could be the problem? I used to have a boat with a Merc I-O that was having starting/idling issues. Replaced the ICV, about a $40 part and all was good.