Question for the engine guys,nf

[vinnimon]

I have a 3 ltr mercruiser inboard engine, I have rebuilt it from top to bottom. I had my boat out last week as she ran like a dream

As usuall I run the engine the night before an outing as I tried tonight and it wont start.

I have spark and replaced the plugs tonight.

I have plenty of fuel pressure and delivery to the carb

I replaced the carb fuel filter as well. Main filter at the pump is good.

Now I tried pouring fuel down the carb, and I didnt even get a back fire or a burp out of it.This tells me that my carb is plugged, or im sucking up seperated fuel.

Possibly a stuck float

Any opinions would be appreciated

Thanks in advance

V

[skinny]

altho late when you discovered that it didn't fire after dumping fuel in the carb (therefore bypassing any proper things it does) did you by chance check for spark

I was always taught if you have fuel(you dumping) and you have spark it has to run

 

first I would pull a plug and check for spark. if plugs are wet burn them off (I use propane torch) turn over the motor several times with out the plugs to get extra fuel out of bore. if you have spark you can put the plugs back in (always check plugs when you buy them with ohm meter when we use to drag race more than once we found bad plugs out of the box)

 

After the plugs are back in it you can try it or give it a drink(dump some in carb) and try it. it should buck or bark

 

but go back to the got to have's no fuel no run no spark no run

[Canuck2fan]

Three things an engine needs to run. If it is turning over but not firing

1 spark which you say you have

 

2 fuel which you dumped down the carb

 

If it is turning over but not firing

 

3 the last thing is compression.... Have you checked your timing belt or chain?

Edited May 21, 2011 by Canuck2fan

[vinnimon]

Three things an engine needs to run. If it is turning over but not firing

1 spark which you say you have

 

2 fuel which you dumped down the carb

 

If it is turning over but not firing

 

3 the last thing is compression.... Have you checked your timing belt or chain?

 

 

Its gear on gear(cam to crank) no belt or chain., and theres lots of compression.

[Big Cliff]

Its gear on gear(cam to crank) no belt or chain., and theres lots of compression.

 

Then it can only be spark or fuel.

 

Canuck2fan is right on all three counts. I would check those plugs though, just in case. If you remove the plugs, squirt a small amount of fuel into the cylinder, replace the plugs and try to start it. If it still won't fire then there is a problem with the ignition. If it does fire then quit then there is a problem with the fuel supply. It is always possible that one of those gears has sheired a key throwing it out of time. Not likely but I have seen stranger things.

[OhioFisherman]

I almost always had a can of ether around to check for starting problems, ether will fire when gas won`t, weak spark. For safety reason? blow off the plugs with an air compressor rather than a torch?

 

An engine needs 3 things to run, fuel, air, ignition, and the proper timing of the 3.

 

With a carb the engine is getting fuel if you spray ether or pour a little gas into the carb, and it is also sucking air if it turns over, even with low compression, so spark and timing are suspect.

[irishfield]

Then it can only be spark or fuel.

 

 

 

Not if this is the engine with the old stripped cam gear issues????? Has it happened again???

[vinnimon]

Not if this is the engine with the old stripped cam gear issues????? Has it happened again???

 

 

No, the disributor is turning. Seems to me its a week spark

[Terry]

No, the disributor is turning. Seems to me its a week spark

 

so what do you need a day spark or month spark:oops:

 

 

sorry seemed funny at the time

[Big Cliff]

Not if this is the engine with the old stripped cam gear issues????? Has it happened again???

 

You are right Wayne, could be a lot of things!

[vinnimon]

You are right Wayne, could be a lot of things!

 

 

Well I walked away from it for an hr or two, picked longer plugs(as advised on iboats). Regapped the plugs to 35 thou. I went with the mr43lts instead of the mr43t plugs.

I went to crank it over and it started for a minute then died out. What I did notice at times while checking for spark, it was intermitant(high and low spark or no spark)

Im assuming that the distributor is is cutting in and out. Moisture, point breaker,condensor, rotor or cap may be faulty. Best to replace it all.

On top of that I need a new starter now

 

Terry, it will be a week, before she sparks again. Maybe I hope.

[Terry]

well my boat is STILL in the shop

I sure hope it's home and working by next weekend

[vinnimon]

well my boat is STILL in the shop

I sure hope it's home and working by next weekend

 

 

I guess we are in the same boat Terry

Hopefully yours is all said and done, and ready to roar by next weekend. Mine wont be

[mrpike]

HI ! IT could also be the coil if the coil is old or as a bad ground . IT may not fire under a load. But fire fine with the plugs out . JUst my two cent. hope it works out for you.

[Tybo]

One of the most common problem after a cam change is the pintel roller on the

bottom of the distridutor.If the pin and roller is warn you will decrease in spark.

For the timing will always be a little out.Could also be a weak coil.

 

Get yourself a spark tester, This is the only way to tell if you have the right spark.

[skinny]

just a thought here I have talked with vinny and he has told me the motor is the same as what was in a chev car . I have seen that many times the multi purpose for engines. now my question is if it did match a cheve motor from a car could he upgrade the ignition to a HEI type and eliminate the points and condensor and all that sorta old school stuff.

 

He would also be getting away from some of the over priced parts because they are marine