Lean Starting Problem

Flytrade

Flytrade

Active Member
Feb 20, 2018
302
Bradenton, FL
Boat Info
2006 320 Sundancer
Engines
Twin 6.2L Mercruiser
My port engine starts normally, but the starboard engine turns over and over, but fails to start until I advance the throttle. Once started it idles, accelerates and operates perfectly. This leads me to believe the mixture is lean on start.
I thought the problem would be the Idle Air Control Valve, but replacing it did not help. Just to be sure, I exchanged the IAC's between the two engines, and the problem persists.
Prior to shutdown, I tried running the engine at 3,000 rpm, and then turning off the ignition, in the hopes of leaving some fuel in the cylinders. Not much help on starting the next day. Still the same problem.
I can certainly live with starting the engine by advancing the throttle, but was hoping some of you smart boaters would be able to offer another possible solution - that is other than taking it to the dealer. Your thoughts would be appreciated.
 
Wish I could help but I got a boat was built when the dinosaurs roamed, have to pump the throttle til my arm hurts, then crank til the battery half dead. What sick Dr Frankenstein thought carburetors were a good idea.
 
C3B49088-512B-4AB9-94F5-014A419D1003_sRGB.JPG

Are these MPI engines? When it starts, and with the throttle still advanced, what RPMs are you seeing? Is the engine racing or is it idling at 600-850 RPMs?
 
check simple things first
fuel filters last changed?
fuel pressure if you can get a gauge
weak spark, distributor and cap clean, dry and in good shape?
pull a plug after trying and see if dry or wet
 
Flytrade said:
My port engine starts normally, but the starboard engine turns over and over, but fails to start until I advance the throttle. Once started it idles, accelerates and operates perfectly. This leads me to believe the mixture is lean on start.
I thought the problem would be the Idle Air Control Valve, but replacing it did not help. Just to be sure, I exchanged the IAC's between the two engines, and the problem persists.
Prior to shutdown, I tried running the engine at 3,000 rpm, and then turning off the ignition, in the hopes of leaving some fuel in the cylinders. Not much help on starting the next day. Still the same problem.
I can certainly live with starting the engine by advancing the throttle, but was hoping some of you smart boaters would be able to offer another possible solution - that is other than taking it to the dealer. Your thoughts would be appreciated.
Click to expand...

Does this happen only with a cold start? Only with a warm start? Or both?
 
C3B49088-512B-4AB9-94F5-014A419D1003_sRGB.JPG

I looked at the starting procedure in the manual for 6.2 MPI engines. 1. Turn the key. If that does not work, advance throttle to 1/4 open. Turn key. If, after three attempts, it does not start, advance throttle to full open and pull back when engine starts. So, it appears there is some variation in how things work. Crusader used to do engine seminars that I would attend from time to time. One thing I learned is each engine is a little different depending on how the parts were made and how things came together on the assembly line. HP even varies by engine even though they are the same model. Could be the starboard engine is just enough different from the port that it requires a throttle advance. Other advice from the manual is to have the EFI module checked by a tech to see if any faults have been recorded in the computer and fix the faults if any are present. The advice to pull a couple of plugs to check for moisture is a good idea. Leaky cooling jackets might play a role in hard starting. And, these engines are voltage sensitive and require strong starting voltage. Make sure there is enough juice to start both engines.
 
I was speaking of dry being a true lean condition
Or wet with gas actually being rich and more likely weak spark
But water on a plug is never a good sign
 
Thanks for all the advise above. It happens with the engine both hot and cold.
I also read about advancing the throttle, but thought that was for a carb engine. When we start our cars, we only turn the key.
Also, once started it idles and runs perfectly - just starting is the problem.
Unless it's something simple I can check/fix, I'll just have to wait till I take the boat in for some other service.
 
How about cleaning the throttle body. You may have carbon build up that is affecting the amount of air allowed past the closed throttle plate.
 
Assuming this is MPI - The advice on fuel pressure is good. For most FI engines when the ignition is turned on the fuel pump cycles on then back off to pressurize the rails and injectors then during cranking and run the fuel pump runs all of the time; is this happening? When the engine is shut down the pressure in the fuel rail should remain; if it bleeds down there is a problem with the regulator or fuel pump check valve and that/those needs to be replaced. Does this have the infamous Cool Fuel Module?
The second thing to look at is the Throttle Position Sensor (TPS); is it's closed position reading the correct voltage?
The fact you have to advance the throttle lends to issues with the TPS or the rail pressure.
 
Espos4 said:
How about cleaning the throttle body. You may have carbon build up that is affecting the amount of air allowed past the closed throttle plate.
Click to expand...
By cleaning the throttle body, do you mean shooting some cleaner in it while the engine is running?
 
ttmott said:
Assuming this is MPI - The advice on fuel pressure is good. For most FI engines when the ignition is turned on the fuel pump cycles on then back off to pressurize the rails and injectors then during cranking and run the fuel pump runs all of the time; is this happening? When the engine is shut down the pressure in the fuel rail should remain; if it bleeds down there is a problem with the regulator or fuel pump check valve and that/those needs to be replaced. Does this have the infamous Cool Fuel Module?
The second thing to look at is the Throttle Position Sensor (TPS); is it's closed position reading the correct voltage?
The fact you have to advance the throttle lends to issues with the TPS or the rail pressure.
Click to expand...
I appreciate these thoughts, but they are above my pay grade when it comes to this kind of analysis and repair. What is the infamous Cool Fuel Module?
 
I have a similar problem on my 350 mag horizons mpi. On starting, mostly cold engines I have had success by turning the start switch two or three times to presurize the rail.
I never knew there was a fuel pump check valve, does anyone know where this is loactaed?
I do have Cool fuel 3, and have changed both of them with no change in this
problem

Thanks
Rich
 
Yes around they butterfly

any TB or carb has a butterfly
This creates a venturi as air is drawn in
A venturi causes a cold spot like a refrigerator. Crankcase blowby and moisture will condense at that location and crud builds up over time. The crud disrupts air flow at idle when the butterfly is almost closed but has little effect as you open it further
 
Flytrade said:
By cleaning the throttle body, do you mean shooting some cleaner in it while the engine is running?
Click to expand...
With the engine off, spray some cleaner around the throttle plate, especially the edges. It’ll help to open the throttle fully as this allows easier cleaning of the outer circumference of the throttle plate.

Starting the engine right after doing this will be difficult as you’ve created a “rich” fuel condition inside the intake manifold.

You can Leave the throttle wide open for about 15 minutes to let the carb cleaner evaporate.
 
With any electronic fuel injection engine its tough to diagnose problems without a fuel pressure gauge and an ECM scanner.

If you’ve seen many of my posts about my preference for my carburetor engines this is one reason. Injection has its place in cars but its all geared towards emissions and performance. Boat engines run under heavy loads at all times not just acceleration.

Planning Boats will never be fuel efficient. When you only get 1 mpg I just never saw the advantage of Electronic fuel injection. We’re stuck with it because thats where all engine manufacturers were forced to go

new boats even have oxygen sensors and evaporative emission controls.
 
Garwood 003.jpg

I never minded "being stuck with" modern MPI 8.1 engines. They represent a vast improvement over carburated 454s.
 
I’m with Hugh, my comments above about starting, I just need a new choke stove(spring worn not closing plate all the way when cold) were meant as humor, I see a hellalot of ghost issues people chasing on this site. I’ll take simple setups every day. Love high tech in cars. Not in a marine environment.
 
You must log in or register to reply here.

Forum statistics

Threads
113,256
Messages
1,429,459
Members
61,135
Latest member
Gregger
Back
Top