2007 75hp Optimax - Stumper

[CruisinGA]

a few weeks ago was dragging limbs away from my dock, first real usage of the year, motor started stalling while idling and acting funny. Noticed that if I engaged trim it would cause engine to stall but as soon as I let off trim it would come back.

Reading online looked like that was usually indicative of clogged or failing pumps so I replaced the fuel hose and bulb and then replaced both electric fuel pumps. At first seemed better then worsened again to where it won't even start now.

I just checked fuel pressure at the rail and it rises to 88-90 psi while cranking. I checked #1 cyl for spark (very strong) and the resistance of the #1 fuel injector (4ohm) as well as voltage to the fuel injector while cranking (digital multimeter so can't read exactly but averages about 2volt).

So it appears the engine is getting spark and fuel. Where do I look next? My understanding from local mechanic is that even if air compressor was dead boat should still start and run (poorly) so haven't gotten into air system yet.

HELP!

[silvertalon]

Try a new battery of 800 cca or higher. Could be cranking too slow to fire? Sounds like a power management issue. Low amps to the ECM when you are trimmimg .

[CruisinGA]

Installed new battery, engine cranks very quickly. Did a little more diagnosis tonight. Found that if I pulse each injector a few times with a 9v battery and then crank it will start like it should and immediately quit (like using starting fluid. So it is definitely a problem with triggering the fuel injectors, but spark is OK. I checked every ground and had 12.7V from each to the positive post of battery. I’m going to pull and clean each ground and after that I am leaning towards a PCM issue.

[CruisinGA]

I removed lower cowling and cleaned every ground connection (top of PCM mount, the three at the bottom of PCM mount and the two on the block forward of the PCM mount.) All connections were already clean and no corrosion but cleaned anyway. No change.

What is best way to diagnose injectors not firing? They are receiving 9-12V while cranking and I already proved that 9V will fire the injector by using the 9V battery

[silvertalon]

I'd bring it to a dealer and have them test fire the injectors with a DDT. This will also tell you if there's any codes stored, faulty sensors or possibly if the ECM is faulty. Could also have a wire harness issue- open or break at a pin connection etc. Teedious work with an ohm meter and a good wiring diagram can help with this. Maybe bribe a service manager to slide you in for a DDT workup, lol.

[JOE54]

+1^^^^^ prob have to be big bribe right now though