Rough Starting my 4.3L

[hostage]

When I start my 4.3L Mecrusier 190hp engine from cold I do the following: I prime/pump the throttle 2 or 3 times. Then attempt to start the engine. At first I just hear the started turning for a few seconds. Then the engine starts to come to life, though it sound a little rough. Then it dies out. I then start the engine again and and when I put it in neutral and give it some gass, it caughs and pops a little then sometimes starts or spatters out. It sounds good at about the 3rd attempt and I am off. For the rest of the day it is a key turn from for starting, even after sitting for an hour or two. Am I not priming it enough? I am only taking the PO advise on priming (twice) and finding the answer on the www isn't as easy as I thought.

Sparks and Dist Cap were changed last year.

Thanks in advance,

Hostage

 

[mxcobra]

Re: Rough Starting my 4.3L

take a look at the electronic choke....
see if its operatng

 

[joewithaboat]

Re: Rough Starting my 4.3L

Mine does the same thing.

achris who posts here and is very sharp sent me the following explanation....seems plausible and he saved me many hours because i would have had the carb on and off doing all of the same stuff. Now I just live with it.


Chris says...

I investigated this problem for months. Even had a completely new carby supplied by Merc. The original was a 9600 and the new one was a 9666S, still the same problem.

I took the old one apart and set it up on a bench, filled the float chambers with fuel, then blow compressed air through one of the primary venturis, The air flow pulled fuel up through the passages and into the venturi cluster and emitted as a spray, just like when the engine is running. I then refilled the float chamber with fuel to be at exactly the same level as the other one and left it for a few hours. I also put a sheet of white paper under the carby.

When I returned the paper had fuel stain on it and the float chamber for the barrel I had blown though was half empty and I could still see droplets forming on the venturi cluster.

My only conclusion is that the passages are so small that the fuel continues to flow after the engine is shut down due to 'capillary action'. Same way a tree gets water up to the top leaves. Short of opening up all the passages and then having to recalibrate for new jets and emulsion tubes there is little that can be done to fix the problem.

I had come up with 2 possible solutions.
1. replace the carby with a quad-r-junk (Merc ran them on previous models of the 4.3l)
2. replace it with an Edelbrock 1409, but as that is also a Carter AFB copy (same as the Weber) I was unsure if that carby didn't dribble too...

In the end I replaced the whole engine for a new 2006 4.3MPI, and I am having so much trouble with that, I wish I had just lived with the dribbly Weber!!!

Cheers,

Chris.........

 

[Don S]

Re: Rough Starting my 4.3L

Here are the procedures from an owners manual. From your discription, I think you need to give it some throttle while cranking. It sounds like you leave the throttle lever at idle while cranking.



4 Place control handle in NEUTRAL.

5 Push THROTTLE ONLY button and position throttle setting as follows:
COLD ENGINE - Move control/throttle lever to full throttle, then return to about 1/4 throttle. In extreme cold
it may be necessary to pump lever more than once.
WARM ENGINE - Move control/throttle lever to 1/4 throttle position.
FLOODED ENGINE - Move control/throttle lever to full throttle. Be prepared to decrease engine speed to
1000-1500 rpm as soon as engine starts.

6 Turn ignition key to START. Release key when engine starts and allow switch to return to RUN position.

7 Carbureted Engines - Move control/throttle lever back to decrease engine rpm to 1000-1500 rpm if necessary.

8 Check oil pressure gauge immediately after engine starts. If oil pressure is not within specified range (see
SPECIFICATIONS), stop engine immediately and determine cause.

9 If engine is cold, run engine for 1 or 2 minutes at fast idle (1000-1500 rpm).

 

[hostage]

Re: Rough Starting my 4.3L

Here are the procedures from an owners manual. From your discription, I think you need to give it some throttle while cranking. It sounds like you leave the throttle lever at idle while cranking.



4 Place control handle in NEUTRAL.

5 Push THROTTLE ONLY button and position throttle setting as follows:
COLD ENGINE - Move control/throttle lever to full throttle, then return to about 1/4 throttle. In extreme cold
it may be necessary to pump lever more than once.
WARM ENGINE - Move control/throttle lever to 1/4 throttle position.
FLOODED ENGINE - Move control/throttle lever to full throttle. Be prepared to decrease engine speed to
1000-1500 rpm as soon as engine starts.

6 Turn ignition key to START. Release key when engine starts and allow switch to return to RUN position.

7 Carbureted Engines - Move control/throttle lever back to decrease engine rpm to 1000-1500 rpm if necessary.

8 Check oil pressure gauge immediately after engine starts. If oil pressure is not within specified range (see
SPECIFICATIONS), stop engine immediately and determine cause.

9 If engine is cold, run engine for 1 or 2 minutes at fast idle (1000-1500 rpm).

Don,

Thanks for the tip, after posting this I came across a couple of suggestions and that made it start the first time. I pumped the throttle 3 times then, put it in neutral and put the throttle about 1/4. It started right up after not being used for almost 2 days. I did let it idel for a few and I had no more issues. Now I don't have to feel like my boat has issues and I feel smarter.

I will try it pumping once + 1/4 throttle to see it starts up. This is great info!