93 Omc 5.0 Efi Surges At > 3k Rpm

[azrag]

Please help.
1994 SeaSwirl 190SE, 5.0 EFI OMC Cobra
Boat has been running great all season. Uses 1/4 to 1/2 tank each outing and we go about every other week. So the fuel is fresh.
In the middle of our last lake trip... If I go WOT, she'll rev up to ~3K, then start to stall, recover, stall recover. Almost like someone is cutting off fuel or spark. I can ease her up to 3K, but once she starts to go past that 3K RPM it stalls, then recovers almost immediately, then stalls, recovers, until I back off the throttle to under 3k, she'll ran fine under 3K for rest of day. I had no choice.
Checked:
-limit switches on shifter that stumble engine are not interferring. actually disconnected them for troubleshooting and same issue.
-Fuel Rail Pressure with reg. is 36, without 42
-Ran engine checking fuel pressure guage, and at WOT when isssue occurs fuel pressure was constant 36.
-Fuel Leakdown test passed, only dropped 1 lb. in 3 minutes
-fuel regulator passed and shows no signs of fuel leaking.
-ECA reported 11, so system pass with no error codes
-Coil resistance was at top of spec but within limits. Spark seems bright and strong.
-Voltage > 13 when running near 3K.
-plugs, cap and rotor were replaced beginning of '06 season.
-new fuel/water seperator filter today.

I'm taking the alternator in to get checked, but I doubt that's it.
Gonna buy a coil too. But I hate to shotgun it.
Please help, any suggestions appreciated. Today would have been a great day... at the lake

 

[Don S]

Re: 93 Omc 5.0 Efi Surges At > 3k Rpm

Not sure why you took the alternator in. Use a DVM directly on the alternator and see what voltage it putting out at around 1200 rpm. Should show 14V or better.

Try this test and see what happens.
http://forums.iboats.com/showthread.php?t=167561

 

[azrag]

Re: 93 Omc 5.0 Efi Surges At > 3k Rpm

Thanks for the advice Don.
My fuel pressure guage didn't have vacuum. So in the "sprit" of your test, I substituted the entire fuel supply system by using a new 3/8 fuel hose and ran it from a 2 gallon gas tank of fresh fuel straight to the fitting on the fuel filter/water seperator bowl. This would provide an unrestricted leak free supply of fuel. same results, upon higher rpms, the engine rpm oscillates. It's as if someone was working the throttle back and forth.
What next? I'm leaning towards ignitoin sytem only because the fuel rail pressure was a consistent 36 psi. and 42 psi with regulator disconnected. I even tried WOT at 42 psi. same problem.
Oh and the alternator was a reach in that I read somewhere that the ECA would sometimes stumble if it wasn't getting the proper voltage.
Help!

 

[Reel Poor]

Re: 93 Omc 5.0 Efi Surges At > 3k Rpm

I would wager the injectors are stopped up with crud causing the engine to run lean. Pull the fuel rail and look in the top of the injectors.

 

[azrag]

Re: 93 Omc 5.0 Efi Surges At > 3k Rpm

Thanks for reply Real Poor,
I pulled the intake, and then the fuel rails. Shined a light down into the top of each injector, and the screen on every one was nice and clean. Now what? I haven't put the manifold back on as I now have a clear shot at the high pressure fuel pump. I don't think that's it though, again Pressure is steady at 36 psi.
Any other ideas guys? I appreciate the assistance so far.

 

[Don S]

Re: 93 Omc 5.0 Efi Surges At > 3k Rpm

Time to get an OEM service manual and follow the diagnostic procedures. With EFI, it starts getting really expensive to replace parts and hope.
I also don't recall checking injectors with a flashlight as being one of the tests.

 

[sa1me]

Re: 93 Omc 5.0 Efi Surges At > 3k Rpm

Hello,

my name is Johan and I am from Sweden.

I have the exact same sympthoms on my -94 Chris Craft Concept 21, I managed to google this topic, and I would do anything to find out what causes this anoying problem?

Please let me know, should you have found a solution.

 

[Don S]

Re: 93 Omc 5.0 Efi Surges At > 3k Rpm

Follow all the steps given above.
It's also best to start your own thread, not just add on to someone elses.

Welcome to iboats.

 

[Coors]

Re: 93 Omc 5.0 Efi Surges At > 3k Rpm

One question- have you checked what the coil is putting out during this?

 

[Don S]

Re: 93 Omc 5.0 Efi Surges At > 3k Rpm

Who are you asking coors? The original poster from Aug 07 or the new poster?

 

[a70eliminator]

Re: 93 Omc 5.0 Efi Surges At > 3k Rpm

Sounds fuel related, injectors are clean and fuel pressure @ 36/45 ok, what about the volume of fuel xx cc's per minute something like that, I'm thinking just cause you have pressure doesn't necessarily mean your getting the volume of fuel needed, even though you ran from a clean jug to eliminate in-tank problem you could still have a bad pump check the volume output. I'm no expert just shooting from the hip.

 

[Don S]

Re: 93 Omc 5.0 Efi Surges At > 3k Rpm

Same with you a70, who are you asking, the original poster or the second that opened this old post?

 

[a70eliminator]

Re: 93 Omc 5.0 Efi Surges At > 3k Rpm

I wan't asking anything, what am I missing here? I simply replied to the original posting.

 

[Don S]

Re: 93 Omc 5.0 Efi Surges At > 3k Rpm

I wan't asking anything, what am I missing here? I simply replied to the original posting.

That's what I mean, you were repling to the original post, but it is an old post that was opened up by a new poster asking a SIMILAR question. I ask him to start a new thread because most people only reply to the original poster. You just proved the point quite nicely.

 

[a70eliminator]

Re: 93 Omc 5.0 Efi Surges At > 3k Rpm

Oh.... I'm a doof, I gotcha now

Later.

 

[Coors]

Re: 93 Omc 5.0 Efi Surges At > 3k Rpm

Same with you a70, who are you asking, the original poster or the second that opened this old post?

I keep missing that they are old; can't they be archived, and not be ressurected, as a new one?