8.1L 496 Starting issues

jbschmalz23

I have the 496 engine in my 280EC. Starting at the end of the season last year, every once in a while, I would go to start the engine and it would just crank. Once was even after I had been out cruising for a little bit and we did some floating to eat some lunch.. went to start it and nothing. If you wait a little bit, and crank some more, it will eventually start. I saw on another forum to swap the relay on top of the engine for fuel with the trim relay, etc. Got the boat out of storage this weekend, it started right up with the muffs.. was idling for about 5 minutes and then quit, and wouldn't start again. I tried the swapping of relays... nothing.. anyone ever have this happen? This is my first fuel injected boat.. wasn't sure where to start?

Lifes Good

How new is your battery?  Check all your battery connections are tight.  All the way to the starter too.  

Michael T

Good points from LG.... as well check the condition and gauge of the cables. Could a p.o. have replaced with the wrong cables. Do they show signs of corrosion. What shape are the breakers/fuses in - any signs of corrosion. IAC? Solenoid?

jbschmalz23

The batteries came with the boat. I'll have to check to see how old they are. What kind of readings should I be seeing before and while cranking on the volts? The connectors are good and tight. Just put the batteries back in for the season. I'll check tomorrow to see what they're putting out while cranking over.  And check the connection on the starter. Thanks for the input. Hoping I can figure it out without having to take it somewhere to be looked at. 

jbschmalz23

The cables all looked pretty good. I will go over them again tomorrow. Not sure about the IAC. I noticed some mention of that on some other forums I was researching. Also saw mention of the fuel pump. Thanks so much for the info! Not sure if it helps, but also wanted to mention that on the last trip out before putting it away.. It idled fine as I pushed off the dock but as soon as I engaged to give it some throttle it would die out, but then started right back up, and did the same thing..  I revved it some and was able to go after that. 

jme097

That sure sounds like a fuel pump to me. 

craigswardmtb

Start easy and replace that IAC.  These things fail often anyways so worth replacing.  You can get them for cheap at Rock auto online.

212rowboat

how old is your fuel filter?  it may be worth changing all the same, anyway. 

it could certainly be a gummed up IAC... it could be a clogging fuel filter... it could be a blocked vent on your tank... it could be a weakening fuel pump... that's the order I would approach it... 

get a fuel pressure gauge from the parts store... you should hold a steady pressure no matter the RPM's- so if it fluctuates more than 3 or 4 psi, you've got issues with the pump... if it steadily decreases, you've got a tank vent issue... if it holds steady throughout, you've got IAC or air filter issues... if it drops and then returns w/ more throttle, you've got fuel filter issues. 

jbschmalz23

Thanks so much everyone! Just replaced fuel filter when I put the boat away and changed oil etc. was hoping that the filter was the issue and it wouldn't happen when I got the boat out. What should the pressure be reading? Does anyone have the part number for the iac I would need? Also, not sure if it matters, but it is the cool fuel module. 

jbschmalz23

Picked up a fuel pressure tester: there should be a valve to hook up to on the fuel rail, correct? I am going to test that this weekend. Is my IAC inside the throttle body? I know there's a foam muffler on it. When I felt inside, the muffler is pushed way back, can't even pull it out (not sure if that's how it's supposed to be). Not sure if you can tell by the picture. Also, a friend let me borrow his OBD scanner for a car. Can I hook that to my engine for codes or do boat engines take a separate scanner? Thanks in advance for any info! This forum is my bible! Lol. Be lost without it!

212rowboat

yup- test port on the fuel rail- schrader valve... 

nope- OBDII reader will do you no good, has to be merc.. the ports won't even connect..

that TB has some build up on it, and it indicates to me the IAC is going to be filthy, too- it when that blade is closed, all that stuff is sucked through the IAC... I wager that is your issue after seeing the blades.  

always be careful pushing things around in the IAC- the mapping is easy to toss on those things, and the PCM can be tricked. 

that hole in the blade- it makes sense now, after reading your symptoms, that if that was the primary source of air for the engine at idle and because the IAC is obstructed, it would behave as you described.  a 496 is a whole lot of engine to feed through a tiny passage........  I've never liked those ports- and certainly not using more than one (as the perforations allow you to knock out another) because it pushes the logic on the PCM to the outside parameters of it's air tuning mapping- which pushes other items to theirs as well- TPS's, fuel trim to account for more air, ect... 

If it were me, and it isn't, but if it were- that TB would be on my bench tonight with the electronics carefully removed and getting blasted with TB cleaner- then put back together (it's not NEAR so difficult as a carb) with a cleaned or new IAC and gaskets... sparkling... 

craigswardmtb

IAC's are so cheap that I would replace rather than clean.  Rock auto is your friend.

jbschmalz23

You guys are the best! That's what I'll do. My fingers were black from where I reached in there. Definitely dirtier than I thought it would be. Would that keep it from starting too? Do you guys happen to have the part number for the IAC and its filter. The filter was pushed so far back in there that I wasn't even able to pull it out with my fingers. Should it be that far in? Don't know what I would do without you all! 

212rowboat

it certainly could make it hard to start... a little bit of a compound on that:

the IAC's position is 'supposed' to be known, and that known position allowing a certain volume of air past... no air, no run... meanwhile, that certain volume of air is sprayed with a catalyst (fuel) which allows it to be ignited at a controlled point- the injectors and fuel pressure regulate via logic on the PCM (reconciling IAC position, throttle position sensor info and mass of air flow (maf) or manifold absolute pressure (MAP) info) about how much fuel is to be sprayed, and in proportion to the amount of air ingested.... if the air is too much or too little, and the fuel too much or too little, which is easy to happen when one of the measures in place to meter it (your IAC), is misbehaving.  = no start or hard start and poor running.

make sure and clean your flame arrestor too (air filter).   

craigswardmtb

That little foam piece is useless and usually disappears after a while...  It supposedly gets rid of a pronounced whistle under operation.  A lot of the performance guys just remove it if its not already gone.  Here is a thread on it from last year: https://rinkerboats.vanillaforums.com/discussion/3384/496-whistle

craigswardmtb

Here is the link to purchase the IAC:

 https://www.rockauto.com/en/moreinfo.php?pk=1319722&cc=10001422&jnid=120&jpid=0

jbschmalz23

The new IAC should be here tomorrow. Going to definitely take your advice and clean the TB. Any other tips on pulling the TB to clean it? 

212rowboat

If it's your first time, use your phone to take pictures... It's pretty straight forward but sometimes how something goes back on or is oriented gets forgotten of you don't have something to compare it to. 

jbschmalz23

I cleaned the throttle body this weekend and replaced the IAC. Started and shut off the boat several times without any issues. Fingers crossed! Don't know what I'd do without you guys! The IAC looked clean, but you never know what the inside looked like. I also took the little foam muffler off. It looked really bad and was crushed almost flat. I'm not going to put one back on. I never heard the whistling. Hoping to be in the water in a few weeks to enjoy the summer!!! Thank you guys again! 

aero3113

Great news!

craigswardmtb

Good to hear.

jme097

What exactly is an IAC? And what does it stand for? LOL

frenchship

An idle air control actuator or idle air control valve (IAC actuator/valve) is a device commonly used in fuel-injected vehicles to control the engine's idling RPM. In carburetted vehicles a similar device known as an idle speed control actuator is used.

jme097

Ahhh I see. Thanks for the info @frenchship. Where is this located?

frenchship

Look at number 16

jme097

Should get myself a ported throttle body lol. Installed one in my ZL1. 

212rowboat

I know you spoke that in jest, jme, but for others- No... porting is for top end... at the expense of bottom end... it's all about volume to velocity of air ratios.  Using velocity through smaller passages allows Rev and curve to happen faster, where more air will pull slower through a ported throttle body.  There is a point where the ported will surpass the unported, but it's usually way up there near wot.  

jme097

Hahahah was definitely just kidding 212!