2002 Mercruiser 4.3 MPI dies when running at 3500 RPMs Then runs fine at lower RPMs

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diver94

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Hello,

This is not the first time I post this problem. I?m just starting a new threat to avoid confusion. I initially though that it was an electrical problem, but after hours of checking, the electrical seems to be fine.
I have a 2003 Regal Comodore with twin 2002 Mercruisers 4.3 MPI (Bravo III). When I run the boat fast (over 3500 RPMs), the port engine beeps twice and then drops the RMP and dies. I think this is a fuel related issue (fuel starvation). I only know of the water fuel separator( it was replaced in March this year). This all started after I completely ran out of fuel in early July.
Is there an inline fuel filter for this engine(2002 MEcruisers 4.3 MPI)?
Symtopms:
-Engine starts right up with no issues (even after it dies when I run it at 3500 RPM for a few minutes)
-Idles fine at 700 RPMS
-Runs great for hours at 3,000 RPMS or under
-The other engine (starboard) runs fine
-Fuel is fresh

Thanks!

Lui
 
alldodge

alldodge

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Its always best to have as much info as possible to determine the issue(s). While some things may appear to be a non-issue to one, it can be a break thru for another. Previous thread
http://forums.iboats.com/forum/engi...-engine-dies-at-high-rpm-possible-vacuum-leak

the port engine beeps twice and then drops the RMP and dies
Click to expand...

I'm still of the opinion that it is electrical, because the motor doesn't start loosing power and then die, it "2 beeps" and dies. The EFI motor if the pump could not supply enough fuel it would just start loosing power and run slower due to lack of fuel pressure. If fuel pump relay shut the pump off, there would be 2 beeps and as the fuel was used up (maybe 1 to 2 seconds) it would die.

The beep means the ECM has received something that caused it to reset. A repeated 2 beep every minute or single beep is a fault. A 2 beep and die leans me to it lost power, regained it like ON/OFF the key.
 
Bondo

Bondo

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I only know of the water fuel separator( it was replaced in March this year). This all started after I completely ran out of fuel in early July.
Click to expand...

Ayuh,...... That canister fuel filter is an Important diagnostic Tool,....

Pull it off, 'n See what's in it,....

A brand new fuel filter yesterday is junk if there was crap in the fuel tank today,.... ;)
 
D

diver94

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[FONT=wf_segoe-ui_normal] [FONT=wf_segoe-ui_normal]THANKS All Dodge and Bondo, . I know these problems are hard to find the and I appreciate your help.
I will replace the fuel canister filter and keep trying the electrical (if that does not help).
So...there are no inline fuel filters in these 2003 Mercruisers 4.3 MPI?

[/FONT]
[FONT=wf_segoe-ui_normal]Here is why I feel this could be fuel or fuel pump/MPI related.[/FONT]
[FONT=wf_segoe-ui_normal]This only happens (last 4 times I went out) when Im running the engines at 3500 or higher RPMs for a few minutes (at about the same exact time/approximately 3 minutes after I push them engines to high RPMs). However, I can run both engines under 3000 RPMs for hours with no issues. No issues when idling or slow/no wake RPMs either. Also, I already checked most electrical (it took me hours). I can try to switch the starting switches to see if the starboard engine does the same.[/FONT]
[FONT=wf_segoe-ui_normal] [/FONT]
[FONT=wf_segoe-ui_normal] [/FONT]
[FONT=wf_segoe-ui_normal]1-the gear oil reservoir is full[/FONT]
[FONT=wf_segoe-ui_normal]2-the temperature is at 175 degrees
3-It happens under load (I dont let it run at 3500 for long when Im at the dock, but the engine runs fine when I reach 4k or over for a few seconds)[/FONT]
[/FONT]
 
Bondo

Bondo

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[FONT=wf_segoe-ui_normal][FONT=wf_segoe-ui_normal]I will replace the fuel canister filter [/FONT][/FONT]
Click to expand...

Ayuh,.... Don't just replace it,.... Examine it's contents for contaminants,...
 
alldodge

alldodge

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dont let it run at 3500 for long when Im at the dock,
Click to expand...

Your in neutral running at 3500 rpm at the dock, and it will die?

So...there are no inline fuel filters in these 2003 Mercruisers 4.3 MPI?
Click to expand...

Correct, there is only the one. There is a screen on the fuel pressure regulator but is not replicable

If its fuel then your loosing fuel pressure. Connect a pressure gauge on the rail and see what you have
 
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harleyman1975

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I'm thinking it could be a weak fuel pump. try switching them and see if problem follows the pump or stays with the same engine...that would rule out the pump at the very least.
 
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diver94

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AllDodge said:
Your in neutral running at 3500 rpm at the dock, and it will die?



Correct, there is only the one. There is a screen on the fuel pressure regulator but is not replicable

If its fuel then your loosing fuel pressure. Connect a pressure gauge on the rail and see what you have
Click to expand...


Sorry...I had a couple of hectic days at work!

No..it runs fine in neutral at 3500 RPMs..I just dont like running it in neutral at high RPM for long.


I dont have a pressure gauge, but I can wait for the mechanicto test the fuel pressure (hes on vacation now).

Thanks!
 
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diver94

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Bondo said:
Ayuh,.... Don't just replace it,.... Examine it's contents for contaminants,...
Click to expand...


Got it. Will pour the gas into a glass container/will do it tomorrow (already ordered the filter).
Thanks!
 
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diver94

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harleyman1975 said:
I'm thinking it could be a weak fuel pump. try switching them and see if problem follows the pump or stays with the same engine...that would rule out the pump at the very least.
Click to expand...


Got it. Good idea (I like ruling out probable causes)...I already googled how to remove/replace the fuel pump on the 4.3 MPI (way under the engine/port side). It seems hard to reach (I have twin engines and the one acting up is the port one...space is tight down there).

I will try to reach down there tomorrow.
Thanks!
 
alldodge

alldodge

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Many of the auto parts stores have loaner programs so you could check pressure
 
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kenny nunez

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You said in post 4 that the temperature is 175*, if you have fresh water cooling that would be good. However if these are raw water cooled that is high. If the pump pressure is too low that will throw a code and put the engine in Gaurdian mode. The Rinda will show what pressure the water pump is putting out.
 
alldodge

alldodge

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If the pump pressure is too low that will throw a code and put the engine in Gaurdian mode
Click to expand...

I'm pretty sure there is no fuel pressure sensor for this model year.

Edit: my bad your talking about water pressure not fuel
 
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diver94

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kenny nunez said:
You said in post 4 that the temperature is 175*, if you have fresh water cooling that would be good. However if these are raw water cooled that is high. If the pump pressure is too low that will throw a code and put the engine in Gaurdian mode. The Rinda will show what pressure the water pump is putting out.
Click to expand...
Ouch!
I do have a raw water cooling system (the water pump and impeller were replaced last May). I was not aware of that. I always thought that 175 degrees was the perfect temperature for these engines. BTW, I had this boat for a year now and thats the temp it reads when warm. Also, the starboard engine runs at 175 too with no issues.
Tks!
 
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alldodge

alldodge

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Your motors may have come that way from the factory. It won't hurt anything, and may not ever be an issue so long as you boat in cool waters. The chance of an issue goes up if your boating in the gulf and warmer type waters.

Could use your serial number to verify configuration, but note the closed cooled 170 degree thermostat (item 24), otherwise it would have a 160
http://www.mercruiserparts.com/bam/subassembly/31502/12839/180
 
D

diver94

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kenny nunez said:
You said in post 4 that the temperature is 175*, if you have fresh water cooling that would be good. However if these are raw water cooled that is high. If the pump pressure is too low that will throw a code and put the engine in Gaurdian mode. The Rinda will show what pressure the water pump is putting out.
Click to expand...

Maybe I should remove the port engine termostart to rule that out
 
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harleyman1975

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I don't think that is your problem. my 2003 305 runs at 175 as well. replace the water pump every 3 seasons always has run 175 since I owned it and when I contacted the place I bought it they said 175 is fine.
 
D

diver94

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AllDodge said:
Your motors may have come that way from the factory. It won't hurt anything, and may not ever be an issue so long as you boat in cool waters. The chance of an issue goes up if your boating in the gulf and warmer type waters

My engine serial is: OM619567

Could use your serial number to verify configuration, but note the closed cooled 170 degree thermostat (item 24), otherwise it would have a 160
http://www.mercruiserparts.com/bam/subassembly/31502/12839/180
Click to expand...

Serial is: OM619567
 
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