Mercruiser 5.0 carb crank/won't start condition :(

[MNugen]

Hello
First time posting on the forum, but have been lurking around since I owned my boat. You guys have been amazing helping everyone with their issues. Well, I have a problem now that I may be needing some advise on. I have a Regal 2150 LSC with a Mercruiser 5.0 Carburated, Serial 0L094405. 2 weeks ago my engine started up and ran okay. There was a solid alarm that came on after the engine is hot, so I immediately turned off thinking it's overheating. So I figured I would take out the bottom out drive to change the impeller because it's never been changed since I bought the boat. I also changed the circulating pump (water pump) on the engine. My engine is a closed cooling system (coolant). So after changing all that, it's now just cranking and won't fire up. My question is, would changing the impeller and water pump have any affect on the ignition system? It's been driving crazy and I have look through the forum, and did all the tests for sparks, fuel and air. What else could it be?

thanks in advance

 

[alldodge]

Howdy
Thanks for the SN

2bbl, TB5, electric fuel pump

did all the tests for sparks, fuel and air.

Which one do you not have?

 

[MNugen]

Well, I tested for sparks and see fuel in my carb. I haven’t test for compression. But the engine started up fine before I worked on the impeller and water pump. Does changing the water pump will affect compression some how?

 

[alldodge]

Please which one do you not have. Its ok to not have done compression, but we need to know what is not working?

Is there fuel in the carb?
Is there spark at any of the components (coil, cap, plugs)?

Without more info I would guess maybe the kill switch was pulled or tripped

 

[MNugen]

There is fuel in the carb. There is spark at the distributor and ignition coil. The kill switch is on run position. Checked the voltage on the batteries and they’re full. Still scratching my head as to why it would do this when it was working before changing water pump.

 

[alldodge]

Sure is a puzzler, have spark and fuel and will not start.

If the kill switch had a problem passing power there would be no spark.

If there is spark and no fire then maybe the fuel is not gas, or more water then gas.

Remove the filter and pour contents into a clear container. Allow to sit a bit and see if there is anything other then clean gas.

If all good run through this guide

 

[MNugen]

Thanks for the tip, Alldodge. I’ll pull the gas filter and check for water. And will do the troubleshooting method.

 

[MNugen]

Hi Alldodge,
so I took some gas out from the filter and the gas looks clean gold color. Looks like there’s no water. I did the troubleshooting process and it pointed to bad ignition sensor. Swapped out a new sensor, still no go
I borrowed an ignition module to test too. Still wouldn’t fired up. Just cranks strongly.
back to square one again....damn it.

 

[alldodge]

gold color

Gas should be clear.

Take a gas can with fresh gas and connect a hose to the filter and stick the other end in the can. Refill the filter

Might even take just a very little bit and pour down the carb

 

[MNugen]

So I tried putting in fresh gas in to the filter and a few dash into the carb. Still not even tried to fire up

I am kind curious about one thing. If I turn the kill switch off, it still cranks the same way as it’s On. I thought the kill switch wouldn’t allow it to crank at all.

 

[Bondo]

So I tried putting in fresh gas in to the filter and a few dash into the carb. Still not even tried to fire up

I am kind curious about one thing. If I turn the kill switch off, it still cranks the same way as it’s On. I thought the kill switch wouldn’t allow it to crank at all.

Ayuh,...... The kill switch kills the ignition, aka: no spark,.....

The neutral safety switch kills the starter,......

 

[MNugen]

That’s the only switch I see that supposed to kill the engine for this boat. It’s located near the throttle lever on the driver side. Do you think there may be something’s up with that switch?

 

[alldodge]

The kill switch turns off power on the purple wire coming from the key switch

Check for 12V at the coil with the key ON

If 12V is there, check for 12V at the coil when the motor is cranking

 

[MNugen]

Hi alldodge
Its been raining the last 5days so I didn’t get to try the test out. So it was dried today and went out to test voltage on the ignition coil. I got 9.9 volt with key ON, and got 9.7volt during cranking. Any directions would help.
thanks again

 

[alldodge]

With low voltage there will be weak spark. You have a bad connection somewhere. Pull the 10 pin connector at the motor and check the pins for corrosion.

 

[MNugen]

Pulled the engine connector and it looks good. My Tach is not working so I removed the gray wire to bypass it. Still just cranks and won’t fire up.

 

[MNugen]

Do you think the broken tachometer is cause of low voltage? The thing is, the tach have always been broken and the engine still works before.

 

[alldodge]

Wanted to remove the tach wire because if it was grounding the -side the coil would not fire.

That said you said there is spark and fuel, so why it will not at least hit is beyond me also

I keep thinking spark is not making it to the plugs, but you said it is

 

[MNugen]

My bad on communication alldodge. I tested sparks at the ignition coil and saw there was sparks. However, when I test at the plugs, there is no sparks.

 

[MNugen]

So I did the no spark test again, and it pointed to bad ignition sensor in the distributor. I changed it out to a new one. But still just cranks and no fire.