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  #11  
Old 11-21-2017, 09:11 AM
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JimN JimN is offline
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Originally Posted by MDB1056 View Post
If your boat is EFI it's harder to determine if it's fuel delivery. If carb'd, when it won't start hot try starting fluid in the carb and see if it lights. If it does then you know it's fuel delivery. The other very real possibility is your ignition module. These can age over time and sometimes not work right when hot. You also noted "losing power". This brings up another possibility of an EI conversion module as old ones have been known to malfunction after many years and result in sudden loss of power. After cool down will fire again and seem fine for a while etc. If I missed the spec's on what boat and engine you have my apologies but that would be a help. I'm sure others will also chime in that it could be your coil as they do go bad. See how hot it feels after normal use, or if it's leaking .

I'm running down a similar issue on my 92 Hydrodyne Comp. Always stars cold just fine with a couple of pumps. But turn it off between skiers and it won't start when hot. Wait 10 minutes, open the cover, crank it over a bunch and give it lots of fuel and it will catch, and run fine again. Really annoying. I did the starting fluid test and it did not light which made me look at spark, The original ignition module in the distributor was was old and looked BAD so I replaced. It's better but still only 50 / 50 hot. I just rebuilt the carb (quadrajet) and am back to thinking it may in fact BE fuel after all, as if it's flooding, the starting fluid wouldn't override that . Boat runs great once running. 100% Quadrajet folks are having me adjust my float a bit. Hoping that's the other 50%.

Point out your boat & engine specs

MDB........................
Easy test- open the throttle and if it starts, it's too rich. If it still won't start, open the throttle to WOT and if it starts, it was flooded. I wouldn't advise using starting fluid (especially a lot of it, as I have seen people do)- when it fires, the expansion can damage the engine.

It's 25 years old- the carb may need to be rebuilt or adjusted.
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  #12  
Old 11-21-2017, 09:13 AM
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JimN JimN is offline
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Originally Posted by Sammy View Post
Any help is appreciated! Boat starts fine when cold, no issues. Once the boat has warmed up if we turn it off, it then won't start again. We have read through multiple forums and are having no luck! We've check to see if there is water in the fuel tank, looked for the crank sensor - cannot seem to locate this, do these exist??
To be able to start the boat again we have to disengage the fuel pump and crank it over and expel all the excess fuel till it fires up again. Fuel filter has also been checked and is fine.
Does anyone have any ideas as to what would be causing this?
We also have issuers driving along around 3 grand and suddenly the motor will loose power, once we stop it clears and is fine again.
Thanks!
Expel the fuel from where, the fuel line? Not without fuel pressure.

Check for spark- if you don't have that, THEN look for the cause.
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  #13  
Old 11-21-2017, 12:32 PM
agarabaghi agarabaghi is online now
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Boat: 1994 Mastercraft Prostar 205
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Quote:
Originally Posted by Sammy View Post
Any help is appreciated! Boat starts fine when cold, no issues. Once the boat has warmed up if we turn it off, it then won't start again. We have read through multiple forums and are having no luck! We've check to see if there is water in the fuel tank, looked for the crank sensor - cannot seem to locate this, do these exist??
To be able to start the boat again we have to disengage the fuel pump and crank it over and expel all the excess fuel till it fires up again. Fuel filter has also been checked and is fine.
Does anyone have any ideas as to what would be causing this?
We also have issuers driving along around 3 grand and suddenly the motor will loose power, once we stop it clears and is fine again.
Thanks!
my 1994 u get vapor lock. we insulated the fuel line that was exposed running on the side of the engine and it helped.

it does sound like fuel pump though
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  #14  
Old 11-21-2017, 03:40 PM
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JimN JimN is offline
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Quote:
Originally Posted by agarabaghi View Post
my 1994 u get vapor lock. we insulated the fuel line that was exposed running on the side of the engine and it helped.

it does sound like fuel pump though
Running the blower often helps, too.
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  #15  
Old 11-21-2017, 05:18 PM
curver900 curver900 is offline
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Boat: Mastercraft, prostar 2001 205v
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Quote:
Originally Posted by Skyskiguy View Post
Found the sensor - on top of the block, just below the t-stat housing? Is this the only one on the MCX? $83.45 on MC Parts Depot, $14.90 on Discount Inboard. Can it really be this easy? Again, if this sensor is bad, causing the warm starting issue, wouldn’t the gauge be reading low as well?
it sends a signal to the ECU and when hot and out of spec sends the wrong signal.. nothing regarding the temp you see on your gauge...

I hate to replace parts until it is determined that is it, but this one is pretty cheap...
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  #16  
Old 11-21-2017, 05:42 PM
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JimN JimN is offline
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Originally Posted by curver900 View Post
it sends a signal to the ECU and when hot and out of spec sends the wrong signal.. nothing regarding the temp you see on your gauge...

I hate to replace parts until it is determined that is it, but this one is pretty cheap...
Measure the resistance of your sensor and compare it with an online chart for resistance vs temperature. If it's out of range, it will store a code and if it's IN range, it won't affect performance.

Last edited by JimN; 12-02-2017 at 10:46 AM.
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  #17  
Old 12-02-2017, 09:44 AM
Cumminscj Cumminscj is offline
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Edited:. Jim covered a lot. My two cents is the fuel pump harness has some issues with connectors going bad. So I always like to check for fuel pressure while checking for spark. Had similar issue with one dying under power fully warmed up, turned out multiple connectors in the fuel pump harness were bad. Of course having a fuel pressure gauge on it made it quick to see I was losing pressure.
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  #18  
Old 12-02-2017, 10:42 AM
h2oski89 h2oski89 is online now
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I had an 89’ ski centurion with a 4 barrel holly carb that did this all the time, started on a dime when cold, Then wouldn’t start when warm...I had a buddy who worked on race cars that told me that they had this problem on the race car and it had to do with fuel evaporating when you shut the engine off bc the engines hot...they solved it by putting insulation on the fuel line. I never got around to testing this theory out but it may be that simple.

I like to start simple, like just reboot your computer . My wife gets mad at me when I ask her if she rebooted her computer first, then she won’t talk to me when that fixes the problem
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  #19  
Old 12-02-2017, 10:51 AM
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JimN JimN is offline
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Quote:
Originally Posted by h2oski89 View Post
I had an 89’ ski centurion with a 4 barrel holly carb that did this all the time, started on a dime when cold, Then wouldn’t start when warm...I had a buddy who worked on race cars that told me that they had this problem on the race car and it had to do with fuel evaporating when you shut the engine off bc the engines hot...they solved it by putting insulation on the fuel line. I never got around to testing this theory out but it may be that simple.

I like to start simple, like just reboot your computer . My wife gets mad at me when I ask her if she rebooted her computer first, then she won’t talk to me when that fixes the problem
When the fuel was being drawn from the tank by a low pressure pump, vapor lock was common/inevitable but when the pump is in the tank and the pressure is much higher, vapor lock is almost totally impossible. Also, the fuel line on injected boats is Teflon with a fiberglass sheath, stainless braided sleeve, fiberglass sheath, another stainless braid and the orange flameproof jacket. It's unlikely that the heat is having much affect on the fuel in the line.

Nobody likes to hear "Yes, I can definitely help you with that one. Please unplug the power and wait......":.
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