2008 merc 350 Mag MPI won't start warm or hot

[Ken007]

[h=1]2008 MERC 350 MAG MPI NO START WHEN WARM[/h]
Will not start when hot very hard when warm, boat idles fine runs fine. Fuel system gone through good pressure at rails. Changed crank sensor, IAC, TPS, ignition coil, distributor and timing adjustments, cleaned MAP, I need help!!! I can idle the boat over tho fuel dock for 3 min and it barely gets to temp, try to restart and it acts like its not getting fire. Have to crack throttle and pump when it hits. If I run the boat hard and shutdown I'm there for 3 to 4 hours before I can get it to start.

 

[Fun Times]

Distributor and timing adjustments.

Hi, Could you give a bit more detail of how you did your adjustments to the distributor just to see if they seem correct with this engine model due the differences this system holds vs years past....Also have you tried a new cap and rotor too?

Have you pulled your spark plugs plus done a engine compression test yet to see how the plus look and cylinders are doing?

 

[Ken007]

Plugs have been changed all new wires and cap. I have not tn a compression check yet, the heads rework after I bought this boat 2 years ago. I've always had this issue, the funny thing is it doesn't do it when on the hose pipe. I can close the hatch get the boat up to temp, run for 5 to 10 min shut it down and it will restart in after ten min. I'm getting ready to pull it out again and see if it still performs the same way. When I changed the plugs this weekend all where a little black in color, some looked a little oily or wet looking.
The distributor was cracked where the cam screws on so I changed with used one. Mine has the cam sensor I believe inside. When I timed it I brought to tdc on #1, placed distributor in and bottom was a little ahead of #1 pin, I didn't think this was correct but that where it was. The boat started right up but after I ran it same problem. So I tried moving thought maybe they have dis off by one tooth, dropped it in again, pin lined up this time with button, still same issue.

 

[alldodge]

Reset the distributor as shown in pic below and use the info as guided by Volvo Penta's way of installing it....https://forums.iboats.com/filedata/fetch?id=7001823

 

[Ken007]

Thanks, I'll check, I think I'm correct. This morning it fired up perfectly. Only when warm or hot.

 

[Fun Times]

New cap.

And Rotor I'd hope.

I have not done a compression check yet, the heads rework after I bought this boat 2 years ago. I've always had this issue,

It did this before or after the head work?

the funny thing is it doesn't do it when on the hose pipe. I can close the hatch get the boat up to temp, run for 5 to 10 min shut it down and it will restart in after ten min.

Just a thought but possibly some-sort of exhaust blockage some-wheres to where the water is causing extra blockage creating issues.

When I changed the plugs this weekend all where a little black in color, some looked a little oily or wet looking.

Start checking for excessive blow-by, flame arrestor clean, pcv valve (positive crankcase ventilation) working, clean, installed in correct location?
Engine oil clean during engine running?
Connect a fuel pressure gauge and always monitor fuel psi until you solve the issue....What are the psi numbers? Are they fluctuating a lot?
Sounds like it's time to install a temporary engine vacuum gauge too.

The distributor was cracked where the cam screws on so I changed with used one. Mine has the cam sensor I believe inside. When I timed it I brought to tdc on #1, placed distributor in and bottom was a little ahead of #1 pin, I didn't think this was correct but that where it was. The boat started right up but after I ran it same problem. So I tried moving thought maybe they have dis off by one tooth, dropped it in again, pin lined up this time with button, still same issue.

You'll want to follow all the information inside AllDodge's post above for resetting the distributor just to be sure the distributor is set correctly including the added Volvo Penta's way of doing it as that guide is the most helpful way to this procedure for the marine literature side of things.

So technically you have a different CAM sensor installed now with the new to you distributor or did you reuse your old/original CAM sensor?

You mentioned you don't think you have spark during the issue.....Do you own a timing light? If so connect the light up to the main coil wire and crank the engine and watch the light flash...The light should be very consistent to where it looks like it just stays on even though it's flashing......If good then move the light wire to each plug wire and look for a consistent flash during the engine rotation?

If you loose spark on the coil wire then maybe an Crank Shaft Sensor issue.

 

[Ken007]

First thanks a lot for the help! Let me recap a few things, yes when I bought the boat it didn't start to well and felt under powered. Marine shop to compression check and said valves getting blow by, caused by lean coundition. So heads reworked good compression afterwards, went to shop boat fired up nice. I took boat back to the a month later told the I had the slow start issues after it was warm. That were a little stumped because the went through the cool fuel box, regulator, ingectors and all new wires plugs, cap and button. They said we found a loose connection on the distributor should be good. Back to the lake same problem, they a son said I had a slow / weak starter and the engine was struggling to get up oil pressure so the computer would not let start. So I changed the stater, boat cranks over great, put it in lake, go for a 20 min ride and it want start up. Then I had to winterize it, fought through last summer try to get some use out of it. That's when I changed IAC and throttle position sensor. 3 weeks ago my high side fuel pump failed, I thought great that may have been my issue. Wrong! The distributor had a crack that I found two weeks ago, the boat was running on plane and pretty rough water and died, fail flat, that's when I found the cap was loose. Replaced the distributor new plugs cap and button, boat started up and ran very smooth shut it off and same thing won't start. Here's a few things I know, oil pressure runs around 24 when ideling around, at speed 40 to 45. Water temp 157 to 167, water pressure is running around 1.5 but I seam to have good pressure, I pulled the boat to go check the impeller. I'll check vacuum, fuel pressure reading and compression and get back with you all!

 

[Mr Manouche]

Ever figure out what happened?

 

[QBhoy]

Is this the classic MPI vapour lock issue ? Sounds like it.

 

[lgf]

vapor lock? quits or wont start after warm? tried everything else?
If you have the newer fuel pump module with the integral raw water fuel cooler?
mine was clogged with salt deposits
remove the 2 raw water hoses and run water thru the module .. mine didnt flow thru
i put a stiff pencil brush on the end of a drill and cleaned out the top and bottom ports until water flowed freely thru the fuel cooler
runs perfect now & saved $1200 on new fuel pump