Mercruiser 140, starts when cold, won't start when hot?

[Neutron68]

So, after all the carb work, the boat starts fine when cold.  One pump of the throttle lever is all it seems to need to get enough of a gas squirt from the accelerator pump.  Two pumps and it cranks longer before it starts and then runs a little uneven for about a minute (flooded?) before it smooths out.

The engine runs well - smooth at all throttle settings I've tried.

After the engine has been running a while and is up to full operating temperature, it does not start easily if you shut it off for any reason. 

A few weeks ago, we docked the boat at the local lake resort for a burger and beer.  When we came out, I had a hard time starting the engine again.  Luckily it did start.  I was not sure if it was flooded or starved for gas
I had 2 elderly passengers on board so we docked the boat when we returned from the resort.  When I wanted to start the engine and move the boat to the boat lift, I had a hard time starting it again.

This afternoon, we were near the mouth of the river in the lake and I got into a weedy area and the engine bogged and killed.  I could not start the engine again.  We threw out the anchor and called a neighbor on the cell phone for a tow.  Luckily the neighbor was home and got our message.  We got towed the 1/4 mile back to our boat lift, and I called it quits for the weekend.

Are these symptoms familiar?  They don't make sense to me.

Eric

[Rich_V174SS]

Sometimes even with a warm engine you may still have to partially open the throttle to start it, not necessarily pump it to prime but just crack open the throttle a fraction which will close the choke and squirt in a little fuel.

Engine bogging down and quitting could be something unrelated. Your symptom is vague - you could have run out of gas, fuel pump could have failed or have a clogged pickup in the tank or obstruction in the fuel line, ignition coil or related ignition components could have failed, or even have water in the fuel. You'll have to use process of elimination to determine which.

[Neutron68]

Thanks for the ideas.  I was hoping the symptoms would be more indicative of a problem someone had solved in the past and they'd say, "I had that exact situation, and the XXXXX was the problem."

Sometimes even with a warm engine you may still have to partially open the throttle to start it, not necessarily pump it to prime but just crack open the throttle a fraction which will close the choke and squirt in a little fuel.

I did this today.  Testing the theory that it was flooded, I had the throttle lever fully engaged so the throttle plate was open.  I took off the spark arrestor cap to be sure all the flaps were open.  I ran the starter for 10-20 seconds and it didn't help.  I blew air down the throat and smelled gasoline fumes coming back in my face, so I know there was gas present.  I could also see plenty of gass in the clear plastic fuel filter I put inline between the fuel pump and carb body. 

Engine bogging down and quitting could be something unrelated.

Agreed, today's trigger for the engine stopping is likely unrelated to the starting problem.  I just mentioned it so everyone reading this would know it didn't quit on it's own. 

Your symptom is vague - you could have run out of gas, fuel pump could have failed or have a clogged pickup in the tank or obstruction in the fuel line, ignition coil or related ignition components could have failed, or even have water in the fuel. You'll have to use process of elimination to determine which.

Given that I had trouble starting the engine when hot, under normal circumstances a few weeks ago, the important symptom is, hard to start when hot.
As I see it, the items in your list which focus on the hot-starting issue are "ignition coil or related ignition components could have failed."

How likely is it that the new Petronix Flamethrower ignition coil has a problem when hot?
How likely is it that the Pertronix ignition module (3 years old now) has a problem when hot, when it was powered with the resistance wire, in the past? 
Recall that the resistance wire is connected to the ignition coil, and there is a bypass wire that that sends the full 12V ignition voltage to the Pertronic ignition module.  I believe this is the correct setup, you advised earlier this summer.

Eric

[dorelse]

I had starting issues in my CVZ, would start and run when cold.  When hot it wouldn't...or was very hard to start.  For me, it ended up being that my choke coil had fried and the choke was always on, ie. wouldn't open.

Did they replace it during the rebuild?

Rich is the man on this stuff.

[Jason]

Check timing?

When warm, I usually just start it at closed or slightly open throttle. If it does not start right away, I keep cranking whiling increasing the throttle slowly to wide open. I leave it at wide open till it starts as it must be flooded and will start eventually at wide open as that is the cure for a flooded motor.

Also, always cary a can of starting fluid. It will help even on a flooded motor. If you use it though, unbolt the flame arrestor and squirt directly into carb.

Like Doran said, check your choke. Unless you are boating in 40 degree temps you shouldn't need a choke at all.

Also, like Doran said, Rich is the man!

[Glastronjohn18]

Two pumps and it cranks longer before it starts and then runs a little uneven for about a minute (flooded?) before it smooths out.

Along with the other ideas presented let me throw a couple more of my own.

Does the starter sound sluggish when hot?  With a hot engine clearances are tighter and a failing starter may not have enough power to turn it over fast enough.

Sounds like you're getting fuel, maybe too much.
You may have the classic  'Hot Soak" where the hot fuel bubbles in the fuel bowl and into the primary nozzles causing a flooded condition.
Is your float level correct?
Is your needle and seat leaking?

Just a few more things I was thinking of.

[Plugcheck]

        Check the choke butterflies, since I rarely ever boat under 50 degrees, I have wired my open.  No need for them.  Does run a tad lean at cold start up, but warms quickly.   Might just need an adjustment.   Heat soak is possible, but not likely considering the type of manifold/carb/engine set up.   V8's are far more prone to this issue.   I would not rule out ignition, but that can be checked easily next time it hard starts with a simple spark gap tester, Your going to need a helper to crank though to check. 

[Neutron68]

Some answers to your questions...

This Mercruiser 140 engine has the automatic choke (exhaust gas temperature controlled, not electric).
The choke flap was open when I had trouble starting the engine on Sunday afternoon.  I had taken the spark arrestor can off the carb so I could check both the choke flapper and the accelerator plate down in the carb, to be sure both were open.   When I had trouble at the resort several weeks ago, I did the same and the choke flapper was open then too.

I have not checked the timing.  I bought a timing light earlier this summer, but have not hooked it up, because the engine was starting and running fine.
What should I look for?  Wild variation between cold and hot?

In June, I had the carb totally disassembled, ultrasonically cleaned and rebuilt by The Carburator Shop in Maplewood.  They have a 90 day warranty on their work.  Should I pull the carb and ask them to check it again?

The starter seemed to be cranking at normal speed.  The starter was replaced when the engine was installed in my boat in fall 2014.  Could it have gone bad that quickly?

I don't recall having this hot-start problem last summer (the first summer after the Mercruiser 140 engine replacement).  Last summer it was the opposite - hard to start when cold, due to the bad accelerator pump section of the carburetor.
Things that were changed since last summer:
1.  replacement carb in fall 2015, to fix the accelerator pump fiasco
2.  inline fuel filter (clear plastic) added, to be sure only clean fuel was getting to the carb, and so I could see that fuel was pumping.  Adding this made the fuel line about 6 inches longer and so it touches the engine in a couple of places. (see photos).
3.  Pertronix ignition coil added this summer.  I have a Pertronix electronic ignition module (bought in fall 2013 for the previous engine and moved to this engine) in the current distributor cap and I was advised to get a matching Pertronix "Flamethrower" ignition coil to go with it.  Could it be bad?

Could this be vapor lock? 
Will a fuel pressure gauge reveal a vapor lock condition?
Earlier this summer I bought a pressure gauge that is purported to work as a fuel pressure gauge and a carb vacuum gauge.
https://www.amazon.com/gp/product/B00KRJFSFQ/ref=oh_aui_detailpage_o02_s00?ie=UTF8&psc=1

To check for spark when it's hot, I could order one of these inline spark checkers?
https://www.amazon.com/Pittsburgh-Inline-Ignition-Spark-Checker/dp/B00L1IC2W4/ref=sr_1_2?s=hi&ie=UTF8&qid=1472483025&sr=1-2&keywords=spark+checker

[Rich_V174SS]

I seriously don't think timing is your issue. There should be no change between a hot and cold engine and should be set at around 4-6 degrees before TDC at idle.

If the engine sits between runs I would expect the choke to cool down and close partially if not fully. Cracking open the throttle with the control handle should allow it to release and shut. These engines will be hard to start if the choke isn't operating as it should, which means they all benefit from having a closed choke when starting. However over-priming or flooding can be an issue so it's not often necessary to pump the throttle on a warm start-up, just crack open the throttle to release the choke. As far as the bogging issue goes you also need to check that your carb isn't flooding when the engine is running at idle, evident of fuel dripping from the spray nozzles onto the closed throttle plates. This is indicative of a bad float inlet needle, incorrect float height, or too much fuel pressure from the fuel pump. I had this happen with my own engine 2 years after installing a new fuel pump and also with a customer's boat immediately after installing a new fuel pump. To solve it I removed the mechanical fuel pumps from both engines and installed a 3-5 psi electric pump in place of them. No more flooding problems on either engine.

[Neutron68]

you also need to check that your carb isn't flooding when the engine is running at idle, evident of fuel dripping from the spray nozzles onto the closed throttle plates. This is indicative of a bad float inlet needle, incorrect float height, or too much fuel pressure from the fuel pump.

I can measure the fuel pressure with the gauge I bought earlier this summer. 
What is the sweet spot I should be looking for 3-5 psi?

Will The Carburetor Shop be able to detect if they set incorrect float height or have a bad inlet needle? 
Should I take it back to them and tell them I suspect the carb is flooding the engine at idle?

Since the inline spark gap testers are cheap enough, I'll order one and test the spark when hot, this weekend - just to know for sure.

Eric

[Rich_V174SS]

I can measure the fuel pressure with the gauge I bought earlier this summer. 
What is the sweet spot I should be looking for 3-5 psi?

Will The Carburetor Shop be able to detect if they set incorrect float height or have a bad inlet needle? 
Should I take it back to them and tell them I suspect the carb is flooding the engine at idle?

If you're seeing more than 6psi it's probably too much for the float and inlet needle to hold back so the valve is forced open causing the carb to flood.

You first need to verify if your carb is flooding. When it's running at idle after a good warm-up take off the flame arrestor and look down the intake and if you see fuel dripping from the nozzles then it's flooding. At idle there shouldn't be any fuel dropping into the barrels, it is supposed to go through the idle passages at the base of the carb and is regulated by the mixture screw(s). Only when the throttle is opened should fuel transition to the spray nozzles and drawn in by increasing vacuum.

[Rosscoe]

Verifying you have spark when cranking it warm will tell you a lot. Could your new ignition be bad?
Absolutely. I found that out with my Mallory Unilite. It usually started fine when cold but would just quit working at any time. Not as consistent as your problem. With the help of folks here, I chased that intermittent problem for way too long. Sent it back, got a new one and no issue like that since. Can't rule out new stuff being bad.

[Neutron68]

My plan is to do a bunch of measurements and observations this weekend!

This Mercruiser 140 engine is a 1973 model and likely doesn't have all the refinements that a 1980s or 1990s Mercruiser would have.
I assume that a Mercruiser 140 made in the 2000s has more sophisticated fuel control system?  Maybe even fuel injection?

Thinking ahead...

If this turns out to be a flooding problem caused too much fuel pressure, what are my fix options?
1.  bypass the mechanical fuel pump and add an electric fuel pump like Rich did?
2.  add a fuel pressure regulator between the mechanical fuel pump and the carb?
3.  modify or change the carburetor to a newer model?

My hope is that the ignition coil is bad, because the fix is easy - swap ignition coils.

I've had several people suggest that this could be vapor lock. 
How likely is this?
Can it be measured with the fuel pressure gauge?
Note that the fuel line is a rubber fuel line that touches the engine block in a couple of spots.
I plan to try spacing the rubber fuel line away from the engine and see if that helps.

Eric

[Neutron68]

The guy who installed the engine routed the fuel like like this - clamped to the block, rather than away from the block like you see in stock engine installs.  Could this cause vapor lock?


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[Plugcheck]

      Vapor lock is a bit more prevalent in fuels with alcohol added, but can and does occur with non-ethanol fuels.  Even in marine engines which do not generally see the temperatures that road vehicles, it can still occur.  Being in rubber line reduces this possibility further, but again it is possible.   I would use a tie wrap and a 1" length of fuel line to make a standoff at that point.  You route the tie wrap through the piece of hose, around the adel clamp, back through the tubing, then around your fuel line, then close up the tie wrap.   Its an old off-road trick, I use it on lots of stuff like plug wires.   If its truly vapor lock, does it fire right back up when cool?

[Neutron68]

I rerouted like this and tried it out.  It still is hard to start after it warms up.

I've got it tied to the dock trying to diagnose.
Even when having troubles starting warm today, it seems to start right when I release the key.  I note that at point the voltmeter rises.
I wonder if this is battery voltage related?

I still have to check for spark when it won't start.
I also want to measure the Voltage at the + coil terminal and the Pertronix module red wire.

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[Tonka Jim]

I had the same problem with my 4cyl.
You should be getting 12 Volts from the starter solenoid when cranking & reduced voltage in the run position.
I think you have a bad solenoid and not getting 12V coil voltage during cranking.

[Tonka Jim]

An easy way to check is to run a jumper wire "Hot Wire" from the positive + side of battery to the + side of the coil.
If it starts every time its the starter solenoid.

WARNING; Engine will keep running until you remove jumper!

I have a rebuilt starter from a 1972 Mercruiser 140 if you want to try it

[Neutron68]

On the Voltage idea, I think the battery may be at the end of it's life, with little capacity left.  At one point last fall, I left the ignition switch on in the garage and the battery was discharged totally dead - zero Volts dead.  I recharged the battery and it has seemed to hold a charge so I figured I was ok.  Now, I'm thinking that DEEP discharge hurt it.

BUT, now I've got a new problem.  Likely a bigger problem. 

During engine test cranking (where I noted that there wasn't spark on plug 1), there was a loud CLUNK sound, a puff of smoke and the crankshaft stopped dead.
Now, when I attempt to crank the engine, it turns part of a revolution and encounters resistance and stops.

I'm guessing this is bad - engine removal bad, perhaps?

[Neutron68]

I had our local lake mechanic come over for a look.

To be sure a piston rod hadn't broken, he pulled the spark plugs to look for damage - no damage seen.

So he advised me to crank the starter.  Water sprayed out ALL 4 spark plug holes.  The resistance was hydrolock!

So, now the focus is, how is the water getting into the cylinders?!

The dip stick oil is clean, clear and full - not milky.

Frustraited...