Engine only starts at full throttle.

Flytrade

Flytrade

Active Member
Feb 20, 2018
302
Bradenton, FL
Boat Info
2006 320 Sundancer
Engines
Twin 6.2L Mercruiser
My starboard engine will only start at full throttle. Of course, once the engine starts to fire I immediately bring it back to idle. Once running, it continues to run perfectly. I would think it must be a fuel issue.
The marine repair facilities have a several week waiting list, so I would like to solve this problem myself if at all possible.
Any suggestions would be appreciated.
 
Flytrade said:
My starboard engine will only start at full throttle. Of course, once the engine starts to fire I immediately bring it back to idle. Once running, it continues to run perfectly. I would think it must be a fuel issue.
The marine repair facilities have a several week waiting list, so I would like to solve this problem myself if at all possible.
Any suggestions would be appreciated.
Click to expand...

First thing I would do is read up on what your ECM does when the throttle is fully open while trying to start. A common misconception is that the throttle is controlling fuel flow (give the gas!) It is controlling the amount of air allowed into the mixture. what are the symptoms when trying to start with the throttle at idle position?
6.2L engines in that rig, and do you know the serial number?
 
370Dancer said:
First thing I would do is read up on what your ECM does when the throttle is fully open while trying to start. A common misconception is that the throttle is controlling fuel flow (give the gas!) It is controlling the amount of air allowed into the mixture. what are the symptoms when trying to start with the throttle at idle position?
6.2L engines in that rig, and do you know the serial number?
Click to expand...

The serial number is OW373961
When trying to start the engine at idle, it turns over quite fast - faster that the other engine. However, it does not even try to start until I open the throttle to full.
 
Does this only happen when cold? Or could you get it up to temp, shut it down, then try to restart and same thing happens?
 
Your idle control valve isn't opening, this what allows air in when the throttle blades are closed.
 
I get what you're saying about the IAC. But isn't that bypass only going to help if the TB plate is completely shut?

@Flytrade you're saying it won't start at 1/4, half, 3/4 throttle etc? Only WOT?
 
Not sure what happens on the DTS. I had to replace the TB on my Silverado, which is similar to DTS (no throttle cable). There is no air bypass valve, and the throttle plate is always open a little. If you try to shut it completely, it springs back open a bit.
 
Phil S said:
I get what you're saying about the IAC. But isn't that bypass only going to help if the TB plate is completely shut?

@Flytrade you're saying it won't start at 1/4, half, 3/4 throttle etc? Only WOT?
Click to expand...
That is correct. At anything but full throttle the engine continues to turn over with no indication that it is even trying to start.
 
After reading about the IAC here, I switched the 2 IAC’s between the two engines with no improvement.
 
Full throttle would be a clear flood mode, maybe leaky injectors. Overdue if there're original
 
scoflaw said:
Full throttle would be a clear flood mode, maybe leaky injectors. Overdue if there're original
Click to expand...
Is there someway I can check for leaky injectors?
Can I order injectors and change them out myself?
With this be cost-effective versus hiring a mobile mechanic who is 3 to 4 weeks out?
 
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