2006 Mercury 4-stroke EFI 90hp stalls at idle/no wake

Serial # 1B797016
194 hours

This may me more information that what is needed, but here is my situation:
Preseason:

• New impeller
• Oil change
• New fuel/water separator
• New high and low pressure fuel filters
• New air filter
• Fresh gas

1st use:

• Higher RPMs (2k-4k) ran OK, every few minutes, would drop 200 RPM and recover
• Idle/no wake 700-1500 RPM, after ~10 minutes, shake and stall. Would restart after a few minutes.

Troubleshooting

• Replaced plugs and pencil coils, now runs fine in high RPM range (no surge/RPM loss). Good acceleration, WOT at 5600 RPM.
• Fuel pressure 40-45psi, during shake/stall sequence drops to 20, then 0
• Connected Vessel View, oil pressure, water temp, voltage look good
• No codes in Vessel View
• Removed and cleaned FSM (thanks to http://www.bbcboards.net/showthread.php?t=296491)
• Bench tested both pumps - both seem OK
• Float switch had no continuity - replaced it

Still stalling at low RPM
It's clear that the FSM is emptying. If I pump the primer 10-20 times when it starts to shake and stall, the engine recovers.
Where do I look next? IAC valve, fuel regulator?

Thank you

Steve

Engine should not have, and does not require, a Primer Bulb.

I would recommend trying a totally separate, portable fuel tank, connected directly to the engine with it's own fuel line. See if the problem continues, or ceases. Quick, easy way to determine if the problem inside the cowling, or outside.

Low pressure (lift) pump could be weak, and it's also possible that a replacement float switch is within the "new does not necessarily mean good" category.

Thank you for the reply.
I (finally) was able to run through 2 tanks of gas with a portable fuel tank.
I have 2 observations:
1) Engine continued to intermittently ran rough at idle
2) Engine still stalled at low RPM, but it took longer

After burning through the second tank, I noticed that the fuel connector on the cowling side looked wet.
This connector only had a zip tie, so I added a clamp (see attached - its the line on the right)
Attachment 457712
After adding the clamp (this may be a coincidence) low idle seems to be OK - no stalling, so far.
Now, when I start the engine, I get a fuel vent switch error 1112-23.

Thank you for your help!

Steve

Guessing you're running on a portable tank on which the fuel cap "clicks" when you tighten it really tight? Use of this type of tank REQUIRES (mandatory) a FDV (Fuel Demand Valve) to prevent tank pressurization from flooding the fuel system on the engine.

Gray line should have a plastic (full-round) clamp, such as 816311T Radius-Head Tie Wrap. It also should be heated in piping hot water (about 30 seconds, then shake off water) before installing, so as to prevent stretching or distorting the liner.

Sounds like you found a potential air leak which might have contributed to both complaints... if portable tank is as I suspect, properly connect back to the boat's system , purge the excess fuel from the vent switch and purge canister and see if the problem persists.

Thank you for the fast response,
The tank I used was an older metal one that had a screw-type vent on top of a 1/4-1/2 turn cap.
I did switch back to the boat's fuel system.

After doing so, I purged the vent switch by disconnecting the blue quick connect at the bottom of the vent switch and depressed the pressure relief valve under the green cap.
I let it empty completely.

I still get the 1112-23 fault at every start-up, despite this, the boat seems to run reliably at low RPM.
Do I need to have the codes cleared, or do I need to do something else to purge the canister?

Steve

You may need to physically disconnect that line lower down in the system, remove the cannister and drain it completely (manually).

While faults can be cleared, that is not the reason you see it at start-up. The PCM is still receiving a signal that the cannister is full.

Hello again,
After removing the vent line at the FSM and draining, the error persisted.
I replaced the vent switch and purge vent assembly.
Still get 220 vent float switch high.
Do I need to look into the FSM or live with the error?
the boat seems to be running fine.

Need to test the switch and the harness- that signal is coming from somewhere. New or not, something is wrong.

It’s in the FSM for sure…
I disconnected the vent line from the top of the FSM and attached a clear line.
Turn key to the on position and fuel flows through the line.
Start motor, fuel continues to flow; no code (because vent line is disconnected).
Ill keep you posted!
Attachment 463353

.

From my experience:
1) the FSM has a low pressure pump designed to draw fuel out of the tank (similar to a car)
2) priming can force too much fuel into the FSM an throw a vent switch fault

Primer bulb is not used on FSM models that have no needle valve to halt flow.

JT2012- Please open a separate thread for your separate engine (see Forum Announcements). Thanks!