4.3 not running like it should...where to start?

[CurrentObsession]

2001 4.3 EFI in 20 foot center console Alpha1 drive
​Engine # 0c86926


​Seems as though it is either not running on all cylinders or it is running really rich.

​I have recently changed the plugs, wires and distributor cap. Plugs that I took out where the wrong ones for the engine, I was shocked to see that they were 1/2" longer than the correct direct AC MR43T that I installed. Boat seemed to run ok right after I did these things a few weeks ago, but now it takes forever to get up on plane. The back of the boat at the waterline is now dirty with soot, which was never an issue prior.

​I thought at first that I may have missed getting the wires on the spark plugs properly as access is not good, but I have gone back and made sure they are on there snug as they should be, so that's not it.

​It always seems to start and run well in the drive on the trailer, but terrible on the water. Today on the water, I pulled the air cleaner to observe the carb/EFI in action. First off I was surprised to see what looks like a 2 barrel carburetor, as I thought I had an EFI engine. Upon further inspection, it looks like there are injectors mounted above the butterflies on the carb that squirt fuel down onto the butterflies in idle. Seemed to me that a large amount of fuel was shooting down just to keep it idling. When I goosed the throttle in neutral I was surprised to see how very little the butterflies would open up even with a hot engine and fairly high revs. I kind of thought that it must be like a choke stuck situation, but when I got home and looked at it while not running I was able to get the butterflies to open, but I remain surprised at how much forward throttle I have to give it to see them open at all.

​Any ideas on what I should be starting with?

 

[alldodge]

2001 4.3 EFI in 20 foot center console Alpha1 drive
​Engine # 0c86926

Being a 2001 EFI your serial number is not correct, the 0C is for motors with a carb from what I can find. Also it needs another digit, should be 6 digits after the letter

**​Seems as though it is either not running on all cylinders or it is running really rich.

​I have recently changed the plugs, wires and distributor cap. Plugs that I took out where the wrong ones for the engine, I was shocked to see that they were 1/2" longer than the correct direct AC MR43T that I installed. Boat seemed to run ok right after I did these things a few weeks ago, but now it takes forever to get up on plane. The back of the boat at the waterline is now dirty with soot, which was never an issue prior.

You put the wrong plugs in the motor, they should be MR43LTS which are longer, and are a hotter heat range for the vortec motor

​I thought at first that I may have missed getting the wires on the spark plugs properly as access is not good, but I have gone back and made sure they are on there snug as they should be, so that's not it.

​It always seems to start and run well in the drive on the trailer, but terrible on the water. Today on the water, I pulled the air cleaner to observe the carb/EFI in action. First off I was surprised to see what looks like a 2 barrel carburetor, as I thought I had an EFI engine. Upon further inspection, it looks like there are injectors mounted above the butterflies on the carb that squirt fuel down onto the butterflies in idle. Seemed to me that a large amount of fuel was shooting down just to keep it idling. When I goosed the throttle in neutral I was surprised to see how very little the butterflies would open up even with a hot engine and fairly high revs. I kind of thought that it must be like a choke stuck situation, but when I got home and looked at it while not running I was able to get the butterflies to open, but I remain surprised at how much forward throttle I have to give it to see them open at all.

​Any ideas on what I should be starting with?

What your looking at is the injectors and it does resemble a carb somewhat. It takes very little movement of the throttle plate to move to rev the motor up in neutral. Get the plugs changed back and let us know how its acting.

 

[CurrentObsession]

Okay
​Will do
Paperwork I have indicates a gap of .045"
​Can anyone confirm?

 

[Jcris]

Yes .045 is correct for the LTS plug

 

[CurrentObsession]

Update...

I changed plugs to the LTS version and fired it up on muffs....sounded good in driveway, will know tomorrow on the water.

​I was shocked and horrified while removing the back plug on Port side to find that it was not tight. Loose enough to remove by hand. Electrode that originates from the heart of the plug was completely missing so I doubt that it was sparking. Hope I didn't mess something up deeper in the engine by somehow neglecting to properly tighten it in the first place.

 

[alldodge]

One being loose isn't to bad, but the electrode missing in most cases means pre-ignition, maybe it was just a bad plug.

 

[Jcris]

Do you have a picture of that plug?

 

[Bondo]

It always seems to start and run well in the drive on the trailer, but terrible on the water.
Electrode that originates from the heart of the plug was completely missing so I doubt that it was sparking.

Ayuh,.... That sounds like detonation, probably from a lean condition,....

Change the fuel filter, 'n inspect the contents of the old one for water, 'n crud,....

 

[harleyman1975]

Think you will be fine once the right plugs are back in her. does not sound like anything else is amiss.

 

[CurrentObsession]

Update...
​Finally was able to get her on the water today.

Only thing I have done so far was to change the plugs to the LTS version. Seemed to be much better at first, got up on plane way better than recently, but still not as good as it was before I touched anything. I backed it down and gave her throttle several times till on plane and it seemed to be getting worse with each additional try. Sounded like a clicking or vacuum leak close to the EFI/carb, but I couldn't really be sure as I was alone and couldn't spend too much time at the engine and away from the controls.

​I have not checked the fuel filter yet. In light of my new experiences is that still the best coarse of action?

​Also, I can confirm the engine number on the plastic cover over the air filter/backfire screen says 0C869226, sorry I missed a digit earlier. Someone earlier said the if it is a 4.3 Vortex with EFI it should be a different number. The cover says its a "4.3/V6 Alpha One, Fluid Engine Mounts/Thunderbolt IV Ignition" The cover also is the reason I changed the plugs to "AC-MR43T" plugs at .035 gap. Now I am really questioning what I even have. Is there a motor number on the actual engine somewhere?

​Thanks

 

[CurrentObsession]

Removed the fuel filter and dumped the contents into an old glass pickle jar, so far it looks clean to me.

Do I need to cut it up to get inside of it to properly inspect the filter?

 

[Bondo]

Do I need to cut it up to get inside of it to properly inspect the filter?

Nah,.... Just try it with the new 1, 'n see if it's Better,....

If it's not, ya probably got another fuel delivery issue,....

 

[alldodge]

If your motor is serial number 0C869226 then it is a 1987 to 1992 motor, and is not a vortec, and should be using MR43T plugs. Your first post said the boat was a 2001 model, and that would be at least EFI. So with all this, the motor was changed and it has a carb, or someone put the wrong cover on the motor.

The way it's acting I'm thinking it does have a carb and the engine is flooding. Can you post a pic of the top of the motor showing the carb ?

 

[CurrentObsession]

I will try to post pics tomorrow.....I don't have the best luck with that kind of thing.

​I'm fairly confident its a Vortec, I recall seeing that on a stamping (I think on the valve covers or intake), the carb or EFI looks like a 2 barrel carb body with fuel injectors mounted directly on top of it. When I first turn the ignition key half way I can hear what sounds like a fuel injection pump charging up.

​Is there a tag on the engine somewhere that has an engine number for identification purposes?

 

[alldodge]

Pic of 2, 4 BBL carb and 2 BBL EFI Throttle body

 

[CurrentObsession]

No Title

The plot thickens..........

​The cover says:

Engine 0C869226
Transom 0D347824
Drive 0D39770

What is actually installed on the boat is:

Engine ??????
Transom 0M217979
Drive 0L924594

 

[alldodge]

That's an EFI setup called Throttle Body Injection (TBI) so my guess is someone replaced the plastic cover. So you had the right plugs in the first time and should be using MR43LTS, at .045 gap. Drive is an Alpha 1 Gen II, and I would guess your motor serial number is 0L or 0M series. Directly above the starter should be a plate with at Mec name and serial number.

 

[alldodge]

Take some more pics of the top of the motor, need to find out if you have cool fuel or VST.

 

[CurrentObsession]

No Title

Just got off the phone with Stingray.

​The motor number that was on the build sheet is 0M033507

​The stamping on the block looks like "GM 4.3LG.....14009090W"

​Not sure about that last character could be a W, X, * etc

 

[alldodge]

OK, you have an EFI with cool fuel.

Timing is set by grounding the purple/white wire coming from the distributer. I should be a signal wire with a female bullet connector. This is grounded and then started, which should cause the motor to idle at 1200 rpm. After it warms up a bit set timing at 8 BTDC. Shut motor down and remove ground. After restarting it should idle around 500 rpm

Fuel pressure 30 PSI