350 MAG MPI Repower

[Barry Baadte]

Hey there, just pulled my starboard engine out of the boat to replace the block. Got new block and everything swapped over from original block and got it fired up in my drive way, but the issue I am having is with fuel pressure. When I first started the new engine up, it started straight away and ran well for about 4 minutes and then seemed to stumble and die. Looking into it further, I have great compression, (New block), great spark, but fuel pressures seems to be my issue. I have a pressure gauge connected to the schrader valve on the intake and when I turn the key on the Gen III Cool fuel pump will run for about 4 second, builds about 10 PSI of pressure, I repeat this process two more times and the pressure maxes out at 42psi. Turn the ignition off and the pressure holds steady. Here is where the problem occurs, I start the engine and it will fire right up and idle well and sounds great, but the fuel pressure drops to about 30 and then drops to 20 when the engine begins to stumble and stalls at about 15psi. The fuel pump relay is good (also new), I have 12.7vdc at the fuel pump connector when the pump primes during Ign-On, I have output on Pin 19 of connector A of the ECM during the priming process. What tells the ECM to turn on the Fuel Pump after the engine begins to crank? That appears to be my issue.

 

[JimG]

Can't help much with your problem... sounds like you have a pretty good handle on it.

Some reading for you:
http://www.clubsearay.com/index.php?threads/official-320-dancer-thread.1313/

Best of luck and welcome to CSR!

 

[Espos4]

Sounds like possibly a bad pump. There are 2 inside the CF3 housing.

can you rig up test equipment and verify that you have 12v and ground at the CF3 connector while the engine is running?

If you have power and ground while running and pressure drops, that’ll point to a bad pump(s).

Check the fuel pump relay itself. They go bad over time.

 

[hughespat57]

If you can provide the engine serial number it will allow me to be sure I'm looking at the correct wiring diagram.
So no relay signal to ground after start, but primes ok when switch is cycled.
You are correct something is not telling the ECM the engine is running

Since you have it in the driveway and not the boat how are you connecting the harness?
Just at the ten pin connector to "the boat" Any gauges hooked up?

Check all the connections on the engine harness to their sensors.
Since it runs will we can eliminate the crank sensor.
Check the oil pressure sensor item "c" below. Be sure it has the Blue/black wire.
Not sure if they are close enough to swap but the water pressure is the same style three wire. but blue/white.