2007 4.3L TKS Mercruiser starts and runs then dies after about 30 minutes.

[Rcantu2]

I am having a problem with my 4.3L Mercruiser engine. It starts on the cold start but after about 30 minutes loses power (RPM's) misses and sputters and dies. I have changed the fuel water separator, distributor cap, rotor, ignition sensor and the coil with and to no avail same problem. Please Help!!!

 

[JoLin]

Might be a restricted fuel tank vent. Remove the fuel filler cap and run it. If it doesn't die with the cap off, you have a vent restriction.

My .02

 

[Rick Stephens]

Probably a fuel problem, so like JoLin said, start with most likely and work inward. Tank vent plugged is also checked just by opening the filler cap when the engine bogs and seeing if it sucks air. Or, take the line off and blow through it.

Next most likely is something plugged like a filter or anti syphon valve and the electric fuel pump is getting hot while working harder.

It could also be something like the coil getting hot.

 

[Rcantu2]

Thanks JoLin, Ill try that.

 

[Rcantu2]

Thanks for the reply Rick. I'll check that out today when I get out of work. I replaced the the Coil but if the ignition sensor was bad will it cause the new coil to go bad? In my first post I forgot to mentioned I replaced the plugs and wires.

 

[Scott Danforth]

I wish I had a dollar for every coil that was changed that wasnt bad.... I would be a billionaire.

its never the coil. seriously, only about 3 coils out of a million changed were actually bad.

coils either work....or they dont. and when they go bad, the oil in the coil usually escapes out the cap as the internal windings short out.

what is your fuel pressure? is the oil pressure safety switch still functioning? is your fuel pump relay still providing power to the fuel pump?

 

[Rcantu2]

yes the relay is still supplying power to the pump got 12.1 V and I also tried using a jumper wire on the safety switch and still got the same results. I do have a new switch on order and i should pick it up today. As far as the fuel pressure i don't know how to test it.

 

[Bondo]

I have changed the fuel water separator,

Ayuh,...... Welcome Aboard,...... Did ya inspect the contents of the old filter for anything but clean fresh gasoline,..??

If not, you should have,..... important diagnostic clues live in fuel filters,.....

 

[Rcantu2]

Yes i did inspect the contents of fuel water separator i placed the contents in a Jar and waited 2 days to see if i had water in the fuel and it was clean and pure. I replaced it anyway..

 

[alldodge]

2007 4.3L TKS

after about 30 minutes loses power (RPM's) misses and sputters and dies.

Suggest rebuilding the carb. Being a TKS it takes about 30 minutes for the module to warm up and shut off the extra fuel. Once the extra fuel is shut off, then motor dies because its not getting enough

 

[Rcantu2]

That was going to be my next venture after a new fuel pump being that it is 11 years old.

 

[Rick Stephens]

I wish I had a dollar for every coil that was changed that wasnt bad.... I would be a billionaire.

its never the coil. seriously, only about 3 coils out of a million changed were actually bad.

coils either work....or they dont. and when they go bad, the oil in the coil usually escapes out the cap as the internal windings short out.

You're right, of course. I'll stop mentioning them. I have never in my long checkered mechanicing life replaced a coil.

 

[Scott Danforth]

If the oil pressure switch works and tested ok, why are you wasting money replacing it.

What is your fuel pressure?

 

[Rcantu2]

I don’t know how to check it.

 

[Rcantu2]

I didn’t think it would hurt to replace it since it was all corroded.

 

[Rcantu2]

Is there a procedure to check the fuel pressure.

 

[Rcantu2]

Is there a procedure out there to check the fuel pressure.

 

[alldodge]

Is there a procedure out there to check the fuel pressure.

You need a vacuum fuel pump tester and a Tee fitting. The fitting is placed between the carb and fuel pump. Merc has part number 91-18078 or can make one up from rubber hose and fittings found at the auto parts store

 

[Rcantu2]

Thanks I’ll get one set it up and check the pressure.

 

[Rcantu2]

I’m waiting on the fuel pump fitting to come in but in the meantime can someone help me out with finding a rebuild kit for my Mercarb and the impellor rebuild kit the number on the carb is 866141001 and the drive reads 1A226495. Thanks for the help in advance.