Mercruiser MPI vapor lock

[dcg9381]

I had our 454 hesitate this weekend while skiing... About 1/2 hour later, we shut down, I let it sit for 30 minutes. I tried to restart. It started, had no power, wouldn't come off idle, and fell on it's face. Eventually wouldn't restart.

I raised the sundeck, had a look - nothing obviously wrong. It's MPI, so there really isn't that much to see. Nothing leaking, no obvious disconnects, throttle cables working.

I pulled the cap off the schrader valve on the fuel rail, pressed the valve in.
I got about 6 seconds of solid air.

I went through the process a few times: turn on ignition (run fuel pump), turn off ignition, bleed schrader valve, turn on ignition - until I got mostly fuel out of that valve... . Started it up and headed out.

For the rest of the day I raised the hatch just a bit to vent the motor area.

This is the 2nd MPI motor I've had a vapor lock problem on - both motors were "Mag" version - one a 350 and this on a 454.....

 

[Don S]

Re: Mercruiser MPI vapor lock

You could have an air leak between the fuel tank and the engine. What year 454 do you have. Was it very hot in the engine compartment?

 

[dcg9381]

Re: Mercruiser MPI vapor lock

We set a record for high temperature this weekend and I'm in TX. Outside air was probably 95-98. I'm sure I heat soaked the thing leaving the engine enclosed and not running the fan.

The 454 is 1998.

Both boats would do this if run hard (pulling skiers), and then shut down quickly without venting the engine area. I know there was a service bulletin on the 350 in regard to the issue....


Once I bled out the valve, got more fuel to the motor, I didn't have another problem, but I took greater care to ventilate the engine compartment when turning off.