Hard to start when engine is hot... Sugg. for troubleshooting please!!

[Razvanbuc]

My Mercruiser 3.0 starts perfect when dead cold. I only need less then 2 seconds of crank when cold. After i run it , no matter how long, then i let it sit for 5 min it will not start easely .... It prob needs a couple of cranks to start... Any suggestion what to check for? I was thinking to take apart the gas pump maybe there is dirt in the filter? Its just mind boggling how could it start so easy when it is dead cold... Thank you

 

[tntauto]

Re: Hard to start when engine is hot... Sugg. for troubleshooting please!!

dirty fuel would be dirty when cold or hot. is it carb or fuel injected?

 

[Don S]

Re: Hard to start when engine is hot... Sugg. for troubleshooting please!!

Check the choke. If too tight, it could be flooding a warm engine.
Engine could also be due for a tuneup. When was the last full tuneup?

 

[Razvanbuc]

Re: Hard to start when engine is hot... Sugg. for troubleshooting please!!

Tntauto it is a carb engine. I use only 89 or 91 gas

Don - i am not sure last time full tune up was performed. I just purched this boat 1 month ago. The chock is the screw that allow set how much air goes into the fuel mixture? Also the fuel pump filter and water separator filters wouldn't have anything. I took the flame arestor off and had my friend prime while engine was off. The 2 gas jets had plenty of flow. I have tomorrow off and plen to try to get to the bottom of this. Thank you

 

[Razvanbuc]

Re: Hard to start when engine is hot... Sugg. for troubleshooting please!!

One more thing... I'm reading in the manual that if fuel is present in the sight tube from pump to carburator, the pump is broken and must be replaced. Could you explain why ? If i recall correctly there is fuel in that tube

 

[ShaneCarroll]

Re: Hard to start when engine is hot... Sugg. for troubleshooting please!!

When you go to start it after warm, do you put the the throttle at 1/4 open? It allows these engines to start better, maybe not quite 1/4, but open it up a little bit. It worked miracles on mine.

 

[Razvanbuc]

Re: Hard to start when engine is hot... Sugg. for troubleshooting please!!

Yes i tried to start a different trottle positions with no difference. Now i am wondering what nagative impact would have the sight tube if its full of gas

 

[myoldboat2]

Re: Hard to start when engine is hot... Sugg. for troubleshooting please!!

I'm having a similar problem ("Choke Plate Closing After 1 Hour"). What I can add to this thread is that my 1974 Mercruiser 140 (older 3.0) used to start great cold or hot. When cold, pump threee times, crack throttle, started in about 1/4 second. When warm, leave it in neutral at idle, no pump or cracking, just turn the key and it started immediately. Now something has changed and warm starting is painful. Razvanbuc, being careful, taking the flame arrestor off allows you to check the choke plate once the engine is warm (have a fire extinguisher ready). Cold engine, my choke has the choke plate closed lightly, and it opens after a minute or two as the engine warms. But my problem is that after running an hour or so, the choke plate is closing again with lots of tension on the choke coil spring. This floods the engine and makes hot starting very difficult, and I have to go to full throttle so that the unloader will mechanically open the choke plate to lean the mix and allow starting. Maybe your problem is similar, with the choke not acting right when fully warmed.

 

[jtybt]

Re: Hard to start when engine is hot... Sugg. for troubleshooting please!!

If you have fuel in the clear tube from the fuel pump to the carb, it means the diaphram is ruptured and probably flooding the engine.

 

[Razvanbuc]

Re: Hard to start when engine is hot... Sugg. for troubleshooting please!!

After a day spent troubleshooting it seems the carburator is at fault. The clear tube had no gas in it. The color of the tube is yellowish so that threw me off. I clean all connections at the battery and all seemed to work well. When i was ready to leave the marina i thought to start the engine one more time but it would start. Immediately i remove the flame arrestor to find that the carburator it was dripping gas. It was coming from both circle thing in each barrel. The mechanic said it has to be rebuilt. What do u guys think?

 

[myoldboat2]

Re: Hard to start when engine is hot... Sugg. for troubleshooting please!!

I had my Merc 140's Rochester carb rebuilt a few years ago at a local carb shop that does a lot of marine carbs. Didn't cost very much and improved the idle and acceleration. With all those little teeny springs and things, rebuilding a carb is not something my big fingers can do...

 

[myoldboat2]

Re: Hard to start when engine is hot... Sugg. for troubleshooting please!!

btw, as in my thread about the carb dumping fuel, i fixed mine by replacing the carb float, which was leaking and taking on fuel (getting too heavy).

 

[T-Bone Coug]

Re: Hard to start when engine is hot... Sugg. for troubleshooting please!!

Immediately i remove the flame arrestor to find that the carburator it was dripping gas. It was coming from both circle thing in each barrel. The mechanic said it has to be rebuilt. What do u guys think?

The float valve is hanging open. Either the float is bad, needs adjusted, or valve/seat are bad. Mine was doing same thing, except at idle mine would slowly drop RPMs and die.

Rebuild it using the spring loaded valve in the kit. It will help prevent this problem in the future. The only drawback (according to Mercury) is the potential for leaning out in sharp turns.

 

[mthieme]

Re: Hard to start when engine is hot... Sugg. for troubleshooting please!!

Yup, sounds like it's time to rebuild it.
I rebuild mine about every 4 years or so. Seems that's all the longer the accelerator pump lasts.
Don't forget to tune it up like Don suggests.

 

[kaliona]

Re: Hard to start when engine is hot... Sugg. for troubleshooting please!!

I've had the same hard start problem when warm with my 165HP Mercruiser. I thought I solved it by cleaning all my battery, solenoid, and starter terminals. I have a new coil, distributor, points, plugs, wires etc to eliminate electrical problems. It starts great cold, and also if I try to restart within a minute of shutting the engine off. But if I wait for 5 minutes or more, then its hard to start. I've had the carb rebuilt but that didn't help. Could the carb be so far gone that even after a rebuild, it may still be leaking fuel and flooding the engine. To start, I open the engine cover, remove the flame arrestor and let it sit open for a few minutes. Eventually it starts. Is there any sure fire way to check for a leaking carb?

 

[Don S]

Re: Hard to start when engine is hot... Sugg. for troubleshooting please!!

Best to start a new thread with your question.