No Start / Merc 1998 EFI 5.7

[TilliamWe]

Re: No Start / Merc 1998 EFI 5.7

...
If you swap it and the problem does not move it's a different issue, maybe a connector or a ground. Grounds can be a pain but at least you aren't throwing parts at a situation-guessing.

My point exactly. Just throwing parts at it is not always the most cost effective repair.

 

[300sflyer]

Re: No Start / Merc 1998 EFI 5.7

Update:

Not knowing if the marina would get to my boat or not, I decided to buy a new IAC from my local auto parts store, and head to the boat. When I arrived, the engine would turn over, but again it would not fire up. I removed the original IAC, and installed the new one. Magic! the engine now starts and runs without advancing the throttle! Let it run for 10 min, and everything was still good. Turned it off and back on again 5 or 6 times and its still good. Just then the marina mechanic came by. Told him what I had done, and he was surprised I had it running. He felt the bad IAC was not the reason for the no start... however he checked everything over himself, [including a scan] and found nothing wrong. I then went for a half hour test run and it ran perfectly with no hickups what so ever. The mechanic told me to enjoy my vaction next week. All seems good.

Thanks for the help guys!

 

[TilliamWe]

Re: No Start / Merc 1998 EFI 5.7

Well, glad it worked for you. I didn't believe an IAC would cause a "no start", either. But it appears that can/does.

 

[scoflaw]

Re: No Start / Merc 1998 EFI 5.7

IAC valve is the only spare part I carry on my boat. They fail frequently. This boat I have and the last one, the 98 both have had issues. Symptoms vary from no start to stuck at a very fast idle. Just replaced one last week, merc dealer says they're a hot item.

 

[NHGuy]

Re: No Start / Merc 1998 EFI 5.7

Of course it can be the cause of a no start. It manages the idle. If it is too closed, the idle goes too low. What's lower than idle? Stumble, stall or stopped.

 

[edsmax]

Re: No Start / Merc 1998 EFI 5.7

I agree with NHGuy. When my IAC went on my old EFI motor, it would not start unless I opened the throttle. Normal operation on that engine was just "turn the key".

 

[TilliamWe]

Re: No Start / Merc 1998 EFI 5.7

Of course it can be the cause of a no start. It manages the idle. If it is too closed, the idle goes too low. What's lower than idle? Stumble, stall or stopped.

It has been my understanding, and my eyes that have told me that the IAC doesn't function until AFTER the engine is running. On a TBI, cold starts are supposed to be handled by the ECM, acting as a choke. But yes, I guess if the IAC was completely closed, it would allow no air at all, which would keep it from starting.

I also wonder if the best fix is to use your boats more often. My 1997 boat had 800 hours on it by 2008, and it never had a problem. But my 87 Chevy van, that I put 4000 miles on in 5 years didn't have trouble either. I was just lucky, I guess?

 

[300sflyer]

Re: No Start / Merc 1998 EFI 5.7

In this particular case, even advancing the throttle would not allow the engine to start. It was only immediately after I installed the new IAC that the engine started and ran fine. Somehow the engine did not like the defective one. The mechanic is still puzzled by this.