2004 4.3GXI-E running rich

[stouchton]

Just looking for some thoughts before I dig into this - I think I have the basics covered but wanted to double check.

I have twin 4.3's and independent gas tank for each engine. Noticed my starboard engine seems to burn more fuel than the port. Also noticed starboard exhaust smells rich. Engine runs fine, starts fine, idles fine and reaches max RPM just fine under load. At first I thought it was just difference in tank volumes and level senders (ignoring the rich smell). But now I have installed flow meters and think I can see it. Starboard engine wants to draw a steady 0.8 GPH at idle where the Port engine periodically draws 0.8 GPH, then drops back to zero for 15 seconds or so, rinse and repeat - this seemed to make sense with low pressure pump periodically refilling reservoir. I have not checked GPH under load yet, just idling in slip.

So I checked fuel pressure (all good) and looked at leak down of rail after shut down. Both engines were very similar - nothing stood out.

Both engines have the original MAP sensors from 2004. Figured changing that was part of the plan - just a major pain to reach. Anything else besides the MAP sensors? Dizzy caps, plugs, wire are all new.

Thanks for any thoughts you might have.

 

[alldodge]

Starboard engine wants to draw a steady 0.8 GPH at idle where the Port engine periodically draws 0.8 GPH, then drops back to zero for 15 seconds or so, rinse and repeat

Need a scanner to watch what the sensors are seeing. Starboard running rich is the one issue, port should draw a steady flow even if it's only 0.1 gph

Measure the voltage at the MAP and TPS

 

[stouchton]

I do have MefiScan, so I can do that. I wonder if the fuel flow sensor on Port engine is defective?? It is new. I could swap the flow sensors and see if the behavior follows the sensor.

 

[stouchton]

Need a scanner to watch what the sensors are seeing. Starboard running rich is the one issue, port should draw a steady flow even if it's only 0.1 gph

Measure the voltage at the MAP and TPS

Alldodge - I'd like to pick your brain a little more, but keep in mind I tend to overcomplicate things!

I have seen a sheen on the water's surface around this engine/outdrive. Always assumed it was from the trim, but now realize it is not and it smells like gas. Seems raw fuel is working its way thru??

Also - I smell gas near the fuel pump low pressure body, and actually near the 2 small water cooling lines. You have to have your nose right up against them to smell it. Can't smell a thing at the other engine. I did look around very carefully for a leak and saw nothing. But I sure can smell it when real close (an inch or 2 away).

I am curious (over complicating....) if the low pressure fuel chamber is leaking into the cooling water??? I would think if it was getting into a cylinder I would have some rough idle/operation issues - engine runs perfect.

So - trying to think how to check this, if just to eliminate as a possibility. Simple thing seems to be to simply watch the pressure in the low pressure tank on shutdown and compare to port engine. Was also thinking of removing one of the small coolant lines and run it into a jar to look for/smell gas? I would assume it fills from the bottom and empties from the top??

Can this failure mode even happen??

Curious as to your thoughts.

 

[alldodge]

Don't think it's the fuel pump right now with info provided. Fuel lines over time can start to degrade and a slight smell can start, but in most cases unless the line is cracking it's of no issue (being your under 2 inch away)

I have seen a sheen on the water's surface around this engine/outdrive

This is helpful, I would look at having the injectors cleaned and flow tested, I'm thinking one or more are leaking

 

[stouchton]

Don't think it's the fuel pump right now with info provided. Fuel lines over time can start to degrade and a slight smell can start, but in most cases unless the line is cracking it's of no issue (being your under 2 inch away)


This is helpful, I would look at having the injectors cleaned and flow tested, I'm thinking one or more are leaking

Thanks - the injectors will be fun, buried under the deck! Luckily I am small framed, just might fit.

 

[alldodge]

Pull the plugs and see if there are any that look real white or black

 

[ESGWheel]

Here is a good video on how you pull out the injectors (link) if you are not familiar with that...

 

[stouchton]

Thanks, that is a good video. I have done this before, but had access! Boat is a Monterey 282, engines are under deck not hatch. So have about 10" of clearance.

Here is a good video on how you pull out the injectors (link) if you are not familiar with that..

 

[stouchton]

Pull the plugs and see if there are any that look real white or black

They were all tannish in color. Nothing obvious jumped out.

 

[stouchton]

Wanted to post a quick update. The Port fuel flow sensor is defective - vane did not want to rotate reliably. So this explains funky/pulsating readings.

I did a leak down test on the Starboard fuel rail. Applied power to pump, read 54 PSI on fuel rail. Shut down pump and waited till PSI dropped to 50. Took over 10 minutes. Scoured the web and manuals but could not find a spec on this. Based on the volume of the fuel rail, this seemed fine to me - so I am thinking the injectors are shutting off and not leaking.

Next will be MEFISCAN and see what sensors are saying.

 

[alldodge]

Fuel rail spec is 50 to 60 psi so your ok there.

Try this, turn key on and let it pump up, don't turn key off and watch pressure.

Could even try nut a short time, turn off and back on (no restart) and watch

What I'm testing for is an intermittent ground on one or two injectors. With key on 12V is applied to one side, the ECM applies ground to fire

 

[stouchton]

Fuel rail spec is 50 to 60 psi so your ok there.

Try this, turn key on and let it pump up, don't turn key off and watch pressure.

Could even try nut a short time, turn off and back on (no restart) and watch

What I'm testing for is an intermittent ground on one or two injectors. With key on 12V is applied to one side, the ECM applies ground to fire

Sounds good - I will give that a try. Thanks