5.0 Won't Start

[Ben Levitt]

Our 2013 240 Sundeck with a 5.0 Mercruiser won't start. Last few times when started, it struggled a few seconds to get to idle then smoothed out and ran fine. Now, it won't start. Battery and starter are good. Recommendations? Thanks very much!

 

[Espos4]

Does it crank strong?
Does it crank EVERY time you turn the key?

If that’s the case, next move on to fuel and ignition. Check the fuel pressure when you turn the key to “run” but before cranking the motor. Should be around 40 lbs.

How about some maintenance history?
How long have you owned it and what’s been serviced in the past.

 

[Ben Levitt]

Long Island! I was raised in Jericho.
It does crank strong and every time.
Don't know how/where to check fuel lbs?
208 hours, I've owned for 2 years, regular maintenance and winterizing, new fuel filter. Risers were replaced in 15 under warranty, caps, plugs, rotor 3 years ago.

With that said, I went out to start it and it started - not the "rhythm" as usual, and I had to give it a bit if throttle to get it going but it ran very smooth at idle. Brought it to op temp and shut it down. Did 3 more re-starts and it turned over, but kind of skipped a beat in the cranking process.

 

[Espos4]

You’ll need a fuel pressure tester, basically a gauge and a hose to connect to the Shrader valve. I’d have that done first to rule out (or confirm) a fuel problem. If the fuel pressure is low, it’ll give you difficult starts but may idle and run fairly well.

A faulty coolant temp sensor can make it difficult to start too. You’ll need some special equipment to read that.

Can you take it for a ride?
See if your WOT rpm and top speed are where they normally are.

If WOT rpm and/or top speed are lower than normal, I’d have a compression test done.
That “skipped a beat” description could (emphasize COULD) be one or more cylinders with low compression.

 

[Ben Levitt]

I have my mechanic coming out the end of the week. Will discuss the fuel pressure test and coolant temp sensor thoughts.
We did take it for a ride last night. Did not go WOT but did get to 3500 (34mph) for a minute. Ran great. Sounded fine at all speeds. I think the idle is weak - was at 530-540 - should be more like 600-630, I think. Mechanic is going to change out the IAC valve as an easy thing to try.
Thanks so much for all the advice!

 

[Espos4]

Is yours a DTS motor? If you have a Digital throttle there won’t be an IAC.

 

[Espos4]

I have my mechanic coming out the end of the week. Will discuss the fuel pressure test and coolant temp sensor thoughts.
We did take it for a ride last night. Did not go WOT but did get to 3500 (34mph) for a minute. Ran great. Sounded fine at all speeds. I think the idle is weak - was at 530-540 - should be more like 600-630, I think. Mechanic is going to change out the IAC valve as an easy thing to try.
Thanks so much for all the advice!

 

[Ben Levitt]

Not digital. Replaced the IAC and made all the difference! Thank you.