2002 f115 issues

[johnbruce]

I have a 2002 f115 with aprox 2500 hours compression is 195 on top 3 and 200 on #4 motor is in good shape on the out side ,has run in salt water probably since new.It cuts out when warmed up as if the ignition was cut momentarily , replaced the vst screen,it was a bit plugged but you could see light threw no problem,fuel filters are new, it's always had a racor plus the small primary,fuel pressure on the rail is 39 key on,39 at idle and up around 44 when running ,once it's warmed up it starts cutting out to the point where it won't get up on the step.it seems to be ok below 4000 and when cold wot is up at 5900.I haven't pulled the injectors as I'm sure the lower mounting bolt is going to twist off as a few of the bolts on the intake did,it seems to me as an electrical problem as the fuel pressure remains constant when the motor is pulsing on and off.The pulsing is erratic, the more throttle the quicker it cuts out.the pulses are instant off and on,like one off those shotgun shifts you can put on a Harley.plugs are new,fuel lines new ran on a small tank,whats next?? thanks john bruce gold river bc.

[pstephens46]

Have you checked all connections from battery back to engine. Look at the big ground wires carefully. Unbolt and clean them down to bare metal.

[johnbruce]

yes thanks cleaned all connections ,bat holds at 12 volts up to 14 when running grounds on motor pulled and clean

[pstephens46]

How did you check fuel pressure when under way and during the "cutting out"?

[fairdeal]

How did you check fuel pressure when under way and during the "cutting out"?

that's how I read it:

fuel pressure on the rail is 39 key on,39 at idle and up around 44 when running ,....it seems to me as an electrical problem as the fuel pressure remains constant when the motor is pulsing on and off.

[pstephens46]

I read it the same. Was curious to the actual method.

[99yam40]

my guess would be with a gauge

[panasonic]

When I think of something electrical getting worse after heating up..and causing trouble like you describe....I always think of ignition coils. I had an old mercury. and several motorcycles fail like that.

Been said on here many times that ignition coils rarely fail...but rarely don't mean never.

Have you checked plug caps and ignition coils for specs??

[johnbruce]

my guess would be with a gauge

yes I rigged up an fuel pressure gauge and watched it as I ran the boat,I'm just not to sure about the results as I had a 1 ft piece of fuel line on the set up.if the pulses were quick enough I'm not sure if they would show on the gauge as the hose could absorb the fluctuations??

[johnbruce]

I pulled the primary pump apart looks all ok,and pumping the priming pump when the motor is cutting out does nothing noticeable.

[johnbruce]

almost to the point of looking for a fuel leak with a match,lol

[fairdeal]

IMO, it the problem were loss of rail pressure, you would see that with the gauge, so its not a "fuel" problem, rather electrical.

Losing spark, or losing electrical control of the injectors? and is so, why?

bad connection to ECU? bad input to ECU? bad ECU? how would one diagnose?

where's Rodbolt on this?

[rodbolt17]

me?
I would use my CD-77 and monitor ign coil primary voltage and injector voltages and maybe pulser coil outputs. I would also watch the laptop and see what the various sensors and ign timing are doing.