Please help... 496/8.1L MPI stalling and refuses to start...

[jetdrive]

Much appreciate any ideas/assistance in advance...

I just bought a 2006 Carrera jet boat with 496 MPI motor and a Dominator jet drive.* The motor has about 90 hours on it and for the most part the motor runs great with great throttle response and smoothness that you would expect from a modern fuel injected engine.

Except one problem that I noticed on my very first trip out...

Here is the scenario...* After driving the boat for about half an hour or so at cruising speeds with no issues at all, I decided to just idle it for awhile to relax and after about 5 to 10 minutes of idling, the motor starts to stall and shuts down.* Any attempt to start it fails as it cranks over but acts like it is starving for fuel (but am not sure if that's what is actually happening)...* Also, during the starting process, it makes some nasty banging sounds (like backfiring or something) which make me wonder if something bad is breaking inside the motor...

Any rate, if I were to wait for about 10 minutes or so, the engine will then start with no problem and run perfectly as it does at non-idle speed.

What could it be? Again, the motor runs great about 90 percent of the time... I just can't idle for more than 5 minutes or so or it will die and not start again...* Very frustrating...

Thank you all in advance for your ideas as I'm totally stumped as what it could be.

Mike...

 

[rlemn8r]

Maybe something to look into. I have an 03 eliminator 210 eagle with the same motor. I had the same problem minus the banging part, fire up cold fine and run fine but after about ten minutes of running but if you slowed down to an idle or stopped it would either die or not restart. There are 2 fuel pumps on that engine, a high pressure low volume and a low pressure high volume. The latter one on mine is located on the passenger side of the motor in front towards the bottom. After talking to Greg at GS marine in corona i pulled out the low pressure high volume pump tested it and found out it was bad. Replaced it and no problems since. Just an idea and maybe something to check into..

 

[jetdrive]

Thanx for the tip... It all makes sense that a bad fuel pump could indeed cause this problem.

Couple of questions if u don't mind... How did you test the pump to see if it was bad? Put a voltmeter to it while it's running and making sure to get 12 volts across its terminals?

Also, do you remember where you got the fuel pump from? My 496 is packaged by an outfit called Kodiak marine out of Oregon. Do the marinized versions of the 496 all use the same fuel pumps (since I believe the Chevy truck versions had the fuel pumps in the tank which would tell me that I wouldn't be able to buy them from a Chevy dealer since these pumps are outside of the tank, right?

Thanx a bunch in advnace...

Mike...

Maybe something to look into. I have an 03 eliminator 210 eagle with the same motor. I had the same problem minus the banging part, fire up cold fine and run fine but after about ten minutes of running but if you slowed down to an idle or stopped it would either die or not restart. There are 2 fuel pumps on that engine, a high pressure low volume and a low pressure high volume. The latter one on mine is located on the passenger side of the motor in front towards the bottom. After talking to Greg at GS marine in corona i pulled out the low pressure high volume pump tested it and found out it was bad. Replaced it and no problems since. Just an idea and maybe something to check into..

 

[rlemn8r]

Thanx for the tip... It all makes sense that a bad fuel pump could indeed cause this problem.

Couple of questions if u don't mind... How did you test the pump to see if it was bad? Put a voltmeter to it while it's running and making sure to get 12 volts across its terminals?

Also, do you remember where you got the fuel pump from? My 496 is packaged by an outfit called Kodiak marine out of Oregon. Do the marinized versions of the 496 all use the same fuel pumps (since I believe the Chevy truck versions had the fuel pumps in the tank which would tell me that I wouldn't be able to buy them from a Chevy dealer since these pumps are outside of the tank, right?

Thanx a bunch in advnace...

Mike...

I bought my pump from greg at GS marine in corona. Your correct you would not be able to buy it from the chevy dealer. As for testing it i removed it from the boat and bench tested it. In the the case of mine it was totaly dead.. If you call GS marine and talk to Greg, tell him what set up you have and tell him you need the high volume low pressure pump he"ll know..

 

[jetboatperformance]

Both the OEM style high and low pressure pumps as well as just about any other part or piece you might need for that setup are readily available from us if you need help Thanks Tom

 

[No Butt No Putt]

Pull the valve covers and make sure you don't have any loose rockers. Could have a flat cam.

 

[Brian]

Although I may have to agree with the others on the bad fuel pump thing, you may also want to look at your tank vents. It could be clogged and not letting it vent fast enough. I have seen them clogged with dried up wax before. My bet is on the fuel pump though.

 

[DILLIGAF]

Vapor lock kind of deal?????

 

[Brian]

I wouldn't call what I'm trying to say vapor lock. Just a venting issue.

 

[jetdrive]

I wouldn't call what I'm trying to say vapor lock. Just a venting issue.

By the way, I even considered vapor lock to be an issue but did a bit of a research and found out that with EFI engines especially the ones like mine that incorporate a return line back to the gas tank, although not impossible, the likelihood of vapor lock is extremely nil...

 

[jetdrive]

Maybe something to look into. I have an 03 eliminator 210 eagle with the same motor. I had the same problem minus the banging part, fire up cold fine and run fine but after about ten minutes of running but if you slowed down to an idle or stopped it would either die or not restart. There are 2 fuel pumps on that engine, a high pressure low volume and a low pressure high volume. The latter one on mine is located on the passenger side of the motor in front towards the bottom. After talking to Greg at GS marine in corona i pulled out the low pressure high volume pump tested it and found out it was bad. Replaced it and no problems since. Just an idea and maybe something to check into..

One other question if U don't mind... If the pump is bad, then I'd expect the motor not to run at all and die no matter whether I was idling or doing 4K RPM, right? What am I missing?

Also, if it is bad, then why does it take 10 minutes or so while idling before it dies? I.e., shouldn't it die right away?

Just trying to see how this thing works...

Thanx in advance,

Mike...

 

[Brian]

Any updates?