4.3L mercruiser idle problem possible water in system

[b0horman]

i have a 1993 4.3L Mercruiser with a new Edelbrock Carb. Here's the deal. When i get the engine started of course after adding staring fluid / brake clean. i can only keep it running above 2000-4000 RPM when it goes below that it just dies and can't restart until i add some brake clean. also when i put the muffs on and run it i can have it at WOT and then it will die. i pull all the plugs and no water is in the cylinders. I replaced the plugs and they are burning just fine. Could i have a timing issue or a fuel problem? i just replaced the fuel pump as well. i can't get it started without adding fuel to the system. could my new fuel pump be bad and when i put a load on it (water in system) its too much? the harmonic balance has been painted over and i cant find the mark to TDC. is there a way i can find the mark to check the timing? Compression also checked out fine above 150 in all cylinders. please help

 

[havasuboatman]

Re: 4.3L mercruiser idle problem possible water in system

Did this problem start immediatly after putting on this new edelbrock carb? If it did, you need to look there first. float levels, idle mixture, etc.
You said you have to add fuel to the system to start the engine. Where are you adding the fuel? to the carb? If so, again, check the float adjustments, if they are correct, check your fuel delivery starting with the water separating fuel filter. Pull the old one out and dump it into a clear container. If there is a bunch of water in it, that could be your problem. Replace the filter either way. If no water, check fuel pump pressure and volume.
Find the timing marks for the engine. You must know the timing is correct or you are wasting your time. Look in your engine service manual for where the marks should be. If you don't have a manual, look for the link in the adults only section for the free manual downloads.

 

[b0horman]

Re: 4.3L mercruiser idle problem possible water in system

to be honest i have never had it started before yesterday. i did check the float levels and all that for the carb. the fuel filter is brand new. i will check again though. i am adding fuel to the carb. could this be a choke problem?

 

[tagolf2000]

Re: 4.3L mercruiser idle problem possible water in system

My question's to you would be is it a factory Edle carb straight out of the box? Is your choke closed when attempting a cold start? How old is the gas? With the throttle cables off of the carb you should be able to look down into the carb to see if it is spraying gas in when you move the throttle back. Have you made any adjustments to your idle mixture screws?

 

[b0horman]

Re: 4.3L mercruiser idle problem possible water in system

O.K got a little more headway last night. i took a fuel sample. everything was good to go. i replaced the carb gasket. The choke and everything seems to be working fine. i adjusted the idle air screws. turned them all the way in and then backed off 2 turns. So i went to check the timing after finding the mark on the harmonic balancer that was painted over. well at first i couldn't see it. probably because it was about 20 degrees BTDC. its hard for me to keep her running and set the timing at the same time. i still cannot get it to idle to set the timing. also i noticed when i increased the RPM's the timing was advancing. Is this normal? when i tried to put the timing at 8 degrees the engine didn't like it. but it was good at about 12 degrees but this is at about 2000 rpm. the book says 8 degrees. i am still not sure why it won't idle. any other suggestions?

 

[Bondo]

Re: 4.3L mercruiser idle problem possible water in system

also i noticed when i increased the RPM's the timing was advancing. Is this normal?

Ayuh,... That's how it Works,... Which is Why timing has to be set at Idle...

 

[gadget73]

Re: 4.3L mercruiser idle problem possible water in system

try spraying around the base of the carb with oil, carb cleaner, whatever. If the idle changes, you have a vacuum leak. Same along the edge of the manifold where it bolts to the head.

How is it dying at idle, with black/grey smoke, or does it seem to starve? Could be you have too much or too little fuel. I seem to recall Eddy carbs wanting around 1 1/2 turns out on the idle mix, but it always varies depending on the motor and the jets and such in the carb.