Carver 400 MY engine RPM issue

[hausherrs]

I checked the anti-siphon and the vent tube and both were ok.

The anti siphon had some junk in it that was keeping the valve open. But it wasnt blocking. I dug it out and thats working now.

Im picking up a fuel pressure gauge today and will check that. Might also change the plugs, cap and wires while I am in there.

[hausherrs]

Both are the same. Right around 20. But watching the spray pattern on the bad motor it's intermittently pulling back fuel making the engine hesitate. I disconnected the map sensor hose and no change. Not really sure what to check next.

[km1125]

Source of the post But watching the spray pattern on the bad motor it's intermittently pulling back fuel making the engine hesitate.

What do you mean by that?

[hausherrs]

Source of the post What do you mean by that?

The fuel injector cone shaped spray pattern while it's ruining. For some reason it's cutting back fuel delivery and the engine rpm dips when it does.

[Viper]

Does the cone shaped pattern change or is it obvious that the pattern remains the same but the volume changes? Technically these are simply on or off and the volume shouldn't change. What changes is the length of time it's open during a cycle which isn't easy to determine by simply looking at it. If you hook up a timing light and shine it there while the engine is running, it'll make it much easier to see the pattern and any changes that are occurring. If an injector stumbles, you'll see it. I find it to be a useful check.

[hausherrs]

Source of the post Does the cone shaped pattern change or is it obvious that the pattern remains the same but the volume changes?

The cone pattern changes (It gets narrow) and the fuel pressure & idle drops a hair for one or two seconds. This is at the slip, not under way. I think that fuel pump is going out.

[bud37]

Source of the post

Source of the post What do you mean by that?

The fuel injector cone shaped spray pattern while it's ruining. For some reason it's cutting back fuel delivery and the engine rpm dips when it does.

Just a question for you as I don't have any experience with TB injection......in the pic there it shows the fuel filter and the fuel flow arrow on it, but is difficult to see the fuel lines, I am sure it is but as a double check , is it in the right way around ?

[hausherrs]

Source of the post is it in the right way around ?

I believe the threads are different on each end. But it's on correctly.

Thanks

[km1125]

Might be good to periodically recap what your symptoms are and what you've ruled out so far. Gets confusing looking at different threads and trying to go back through the earlier posts to see where things are at. Always a good step to do when troubleshooting too.

[hausherrs]

Good idea.

STBD engine has been weak and not keeping up with the port motor for the past month or two. This last weekend it started dying on me when I was trying to get the boat back into the slip. Yesterday at idle the fuel delivery into the throttle body was fluctuating enough to make the engine hesitate / miss.

Within the last 2 weeks I have:

Cleaned the Oberg
Replaced the Recor filter
Replaced the TBI metal filter
Repaired the broken oberg to fuel pump fuel hose (Ordered the factory hose for both engines)
Checked the anti siphon. It had something stuck in it but it was small. I could still easily blow through it.
Checked the fuel tank vent and it was free
Fuel pressure at idle is around 20 on both engines
No overheating
Oil pressure ~50 on both motors
Put 40 gallons of fuel in about 6 weeks ago. Time before that was about 6 months ago 40 gallons.

Cap and plug wires are less than a year old. Maybe 30 hours on them.

My thoughts are that maybe my fuel pump is going out. It normally runs ok for the first 30 minutes while I idle out to the bay. Once its time to open it up it starts failing. No power and rpm will go up and down. If I open it up all the way the rpm will go almost to zero. If I throttle down to zero it will idle at 500-700. But recently its been dying on me at idle.