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Dennis10912

Hard starting issues -2016 Sunesta 264 8.2 mercruiser

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Hi everyone, I’m a newbie and looking for some advice.  I just bought a 264 with 40 hours and it is in excellent condition.  Only one problem, the engine takes 3 tries to start (cold or hot), and sometimes I have to move the throttle 1/4 forward in neutral to get it started. I did do a test on the lake before taking ownership and it started fine then. I have changed the fuel filter and bottom filter screen on the gen III cool fuel module, but it did not help.  I filled the tank with supreme and added techron, but still experiencing the hard starts. The engine idles smooth and steady and runs fast and strong.  My only complaint is the hard starting.  It’s hard to believe something is wrong with only 40 hours on the engine.  Any thoughts would be very helpful?   Dennis

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8 hours ago, Dennis10912 said:

Hi everyone, I’m a newbie and looking for some advice.  I just bought a 264 with 40 hours and it is in excellent condition.  Only one problem, the engine takes 3 tries to start (cold or hot), and sometimes I have to move the throttle 1/4 forward in neutral to get it started. I did do a test on the lake before taking ownership and it started fine then. I have changed the fuel filter and bottom filter screen on the gen III cool fuel module, but it did not help.  I filled the tank with supreme and added techron, but still experiencing the hard starts. The engine idles smooth and steady and runs fast and strong.  My only complaint is the hard starting.  It’s hard to believe something is wrong with only 40 hours on the engine.  Any thoughts would be very helpful?   Dennis

Does it idle smooth once you get it started? Sounds like it could be a failed IAC valve. I'd start with a pressure check at the fuel rail.  W

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Hi Wingnut.  Yes it idles very smooth.  I had the boat checked out at the dealer (July 2018) before buying from the private party.  The dealer said it had no codes and ran fine.  It sounds like a good idea to have the fuel pressure checked at the fuel rail. What psi should it be? Thanks.

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6 hours ago, Dennis10912 said:

Hi Wingnut.  Yes it idles very smooth.  I had the boat checked out at the dealer (July 2018) before buying from the private party.  The dealer said it had no codes and ran fine.  It sounds like a good idea to have the fuel pressure checked at the fuel rail. What psi should it be? Thanks.

Tell me what engine you have and give me a valid e-mail address via PM and I'll get the documentation to you.  WI'll

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2 hours ago, Bt Doctur said:

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He has the new 8.2 Merc with the aftermarket cast iron block and aluminum heads, not the old world 502.

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Wow Wingnut,

Thank you very much for the goldmine of information you sent me. I love working on my boat as the rewards are money saving and the satisfaction of doing it myself, but I will say it is a little daunting.  I'm going to change the Idle Air Control since it is the easiest to do.   If that does't fix the problem then I will check the fuel pressure.  I'm just curious, do you think the 8.2 (now built by Mercury) is as reliable as the when built by GM. I believe the 8.2 when released had some teething problems with overheating and vapor lock. (At least that is what I read)  I think the newest generation of the 8.2 was in 2013.  Do you know when GM stopped building them?  Thanks again.

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The 8.2 is a World Products aftermarket cast iron block which was intended for the high performance market. Thicker decks, and re-enforced main bearing journals, and improved oil distribution. The cylinder walls are thicker too, which helps reduce distortion, but does make them harder to cool. Not a huge issue in a marine application, as you have an unlimited supply of cooling water. The only downside I see with them is the age old problem of dissimilar metals as it pertains to head gasket longevity. The 496 platform was intended for the truck market. They have adequate clamping pressure for head gasket sealing in stock format, use cast iron heads, but they are not good candidates for turbos, superchargers, and NOX power adders. The drag racers use the GM DRE II blocks from GM high performance (https://www.gmperformancemotor.com/parts/25534406.html)  .

These specialty blocks can be punched and stroked to over 900 cubic inches, have superior alloy, and most importantly have additional head bolts and a different bolting pattern to take the increased cylinder pressures. Your block, not so much. So your exposure comes down to two things. Don't add a pro-charger, or Turbo and keep the compression ratio right where it is. Those 3 are easy to do. Lastly, temperature control is vital in these engines as they utilize stage I Edelbrock aluminum cylinder heads. Message here is, if you get a high temp alarm, shut her down immediately and either fix the issue or get towed home. No limp home here as the Smart Craft Guardian system allows. Block temperature (closed loop coolant temperature) must stay below 190 degrees without exception. Engine coolant alarm is set for 188 degrees. Remember that this indication is taken from a single point sensor and is not representative of how hot remote areas of the water jackets are actually getting. The good news is, if you were to suffer a raw water supply failure from a failed pump or clogged intake, the exhaust temperature detectors set for 220 degrees will alarm first, long before the block heats up. Just take your time, allow the engine to cool, and find the problem before you attempt a re-start. Best way to confirm flow is to remove the hose from the inlet tube side of the tube to shell heat exchanger, and start the engine for no more than 3 or 4 seconds. If you have a blockage it will typically be there and if you see no flow then your raw water pump impeller is toast. Lastly, keep your Dex-cool closed loop system anti-freeze fresh. It's a great silicate free extended service life product, but can become corrosive once it exceeds it's intended service life. Cadillac had a recall issue where the stuff was eating head gaskets. Either test the stuff, or just change it out after 5 years or 500 hours, which ever occurs first. W

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Hi Wingnut and everyone,

Today I had the time to check the fuel pressures on the 8.2 mag.  This has the Gen III Cool Fuel.  These are the test performed:

1) Turn key to the on position (Engine off) it jumps to 37-38 psi.

2) I did check the vacuum hose on the fuel regulator (with engine off) for fuel wetness and there was none. 

3) Next test is with the engine running, it is at 36 to 38 psi.  

4) Increase throttle to 1200 rpm, still 36-38 psi.

5) Next fuel regulator vacuum hose disconnect and the psi jumped as expected to 42 psi.

6) Next test after 30 minutes with engine off, the fuel pressure did drop to 30 psi.

7) Still hard starts.  It takes about 3-4 tries to start it.  I turn the key and hold it for 4 seconds each time.

Base on these tests results, I'm thinking the high pressure fuel pump.  I believe the pressure at the fuel rail is suppose to be 44 psi, someone even suggested it should be at 53 psi (Indy mechanic).  Your thoughts?    Does anyone know what the low pressure fuel pump does? 

The leaking/dissipating pressure.  This result directs me to the fuel check valve (which I would have to purchase separately from the high pressure fuel pump since it is not attached.)  In order to perform this task would require removal of the Gen III Cool Fuel module.  It is really tight in the work area.  What were they thinking, lol.

I am very knew to this and my thoughts are based on internet reading.  Everyones knowledge and advise are very much appreciated!

Thanks, Dennis

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9 hours ago, Dennis10912 said:

Hi Wingnut and everyone,

Today I had the time to check the fuel pressures on the 8.2 mag.  This has the Gen III Cool Fuel.  These are the test performed:

1) Turn key to the on position (Engine off) it jumps to 37-38 psi.

2) I did check the vacuum hose on the fuel regulator (with engine off) for fuel wetness and there was none. 

3) Next test is with the engine running, it is at 36 to 38 psi.  

4) Increase throttle to 1200 rpm, still 36-38 psi.

5) Next fuel regulator vacuum hose disconnect and the psi jumped as expected to 42 psi.

6) Next test after 30 minutes with engine off, the fuel pressure did drop to 30 psi.

7) Still hard starts.  It takes about 3-4 tries to start it.  I turn the key and hold it for 4 seconds each time.

Base on these tests results, I'm thinking the high pressure fuel pump.  I believe the pressure at the fuel rail is suppose to be 44 psi, someone even suggested it should be at 53 psi (Indy mechanic).  Your thoughts?    Does anyone know what the low pressure fuel pump does? 

The leaking/dissipating pressure.  This result directs me to the fuel check valve (which I would have to purchase separately from the high pressure fuel pump since it is not attached.)  In order to perform this task would require removal of the Gen III Cool Fuel module.  It is really tight in the work area.  What were they thinking, lol.

I am very knew to this and my thoughts are based on internet reading.  Everyones knowledge and advise are very much appreciated!

Thanks, Dennis

On initial start up the injectors are not commanded to fire until the ECM sees oil pressure. How long does it take for your oil pressure sender to become satisfied during cranking would be a question.  Your fuel pressure is slightly lower than spec, but I don't think being 5 psi low is going to cause a slow start. As long as the engine can achieve rated max WOT rpm, I'd look elsewhere. Start with the IAC muffler, and also MAP sensor testing. You say that you must make several attempts before she fires up. What happens if you continuously crank for say 10 seconds? Before spending big bucks on the HP fuel pump, I'd have a tech install his laptop and see when the injectors are getting their initial squirt signal, while he monitors oil pressure, and fuel pressure. Your low pressure pump acts as a make-up pump that fills the cool fuel reservoir for the HP pump. The HP pumps are dead headed at start-up and idle speeds as very little fuel is flowing through them. On MPI automotive application, the excess un-needed fuel is returned to the fuel tank via a return line. Not possible on a marine application so to keep the pump and gasoline cool the fuel passes through the sea water jacketed cool fuel module. The low pressure pump is high volume, low pressure so it does not build excess heat as much as the HP pump. W

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Did anyone figure out this  problem. I have same problem with Merc. 8.2 380 HP.  Won't start on 1st try, but starts on 2nd try?

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