'91 4.3 hard start/dieseling

[boatnut74]

I have a '91 4.3 with 2 barrel carb. When cold it starts up just fine. After it is warmed up I will shut it off to load/unload tubers or skiiers and it will diesel for a few seconds before shutting off. When trying to start it back up I have to crank it for 5 or 6 seconds to get it to start. I pulled the plugs and it looks like it's running a little rich. Checked the timing and it's dead on. I'm thinking either idle mixture needs adjusted or possibly a float setting.

 

[boatnut74]

Re: '91 4.3 hard start/dieseling

Well I adjusted the idle mixture screw a little and it seemed to have smoothed out the idle. Gonna take it out tomorrow and see how it runs.

 

[boatnut74]

Re: '91 4.3 hard start/dieseling

Took the boat back out and there wasn't really any change. It really seems to load up when giving it gas. It has spark on all 6 and timing is right. I think I will check the choke operation next.

 

[boatnut74]

Re: '91 4.3 hard start/dieseling

I noticed the motor never really gets above 130 degrees. I think I'm gonna change out the thermostat (if there's even one there) and see what happens. I know if the motor doesn't get up to temp it won't burn all the fuel. It would be a cheap, easy fix anyway.

 

[boatnut74]

Re: '91 4.3 hard start/dieseling

I pulled the flame arrestor off and looked down into the carb at idle. The venturi's are dripping fuel about 1 drop every 2 seconds from each one. If I remember right they aren't supposed to. Looks like I'm in for a carb rebuild.

 

[Mahoney]

Re: '91 4.3 hard start/dieseling

You are on the right track, do a carb rebuild and make sure you get the float height set right when you rebuild and hopefully you will be good to go. Use an air compressor and carb cleaner and make sure you got all the passages cleaned out good.

 

[boatnut74]

Re: '91 4.3 hard start/dieseling

Thats the plan for now......I've been thinking about putting on a 1409 edelbrock and aluminum intake but have been putting it off due to worries about intake corrosion.

 

[boatnut74]

Re: '91 4.3 hard start/dieseling

Does anyone know what carb kit I would need. I'm thinking about getting a Sierra kit as I had good luck with the ones I used on my Evinrude. Looks like the kit I would need is 18-7098. The number on the carb is 33049565. Napa wants $70 for the kit. According to their book this is a 205hp engine.

 

[mastercylinder63]

Re: '91 4.3 hard start/dieseling

I believe you hit the nail on the head. 130* is not hot enough for proper operating temp. Your engine will run rich and you will get run-on. Forget the carb rebuilding for now. Change the thermostat and install new sparkplugs. You mentioned your timing is spot on and assuming you have a strong blue spark, give the engine a good run and then recheck the plugs. I bet your plugs will be a nice tan color.

 

[WILSONS88]

Re: '91 4.3 hard start/dieseling

$70!!!!!!!!!! Seems a little high. I had to rebuild mine twice and didn't spend that much. I ordered mine from Oreilly auto parts. It was a Sierra kit and was like $23

 

[cr2k]

Re: '91 4.3 hard start/dieseling

Don't forget to use the spring off your old accelerator pump as the automotive ones are weaker and can give you a bog on acceleration.

 

[boatnut74]

Re: '91 4.3 hard start/dieseling

I believe you hit the nail on the head. 130* is not hot enough for proper operating temp. Your engine will run rich and you will get run-on. Forget the carb rebuilding for now. Change the thermostat and install new sparkplugs. You mentioned your timing is spot on and assuming you have a strong blue spark, give the engine a good run and then recheck the plugs. I bet your plugs will be a nice tan color.

I actually had it back out the other day and it was running 150-160. I'm not sure why it was only running 130 that day. I'm not so certain the gauge is working correctly. I did find the screws on the air horn were loose so I tightened them up and it seemed to stop dripping fuel at idle. I'm going to take it out tomorrow and see how it runs before I spend money on a carb kit.

 

[Volphin]

Re: '91 4.3 hard start/dieseling

I believe you hit the nail on the head. 130* is not hot enough for proper operating temp. Your engine will run rich and you will get run-on. Forget the carb rebuilding for now. Change the thermostat and install new sparkplugs. You mentioned your timing is spot on and assuming you have a strong blue spark, give the engine a good run and then recheck the plugs. I bet your plugs will be a nice tan color.

Bad advice. The carb should never drip fuel! Your floats are sinking, misadjusted and almost certainly the needle valve needs replacement. Now would be the time to do the 1409 Edelbrock and aluminum manifold. I ran a 2111 for 6 years before I upgraded to Vortec heads. There is no corrosion on the manifold at all. And remember, when a thermostat opens is not the operating temp of the engine.

 

[boatnut74]

Re: '91 4.3 hard start/dieseling

Thanks for the feedback Volphin. I really want to do the edelbrock 1409 and aluminum manifold but funds are kind of limited right now.