4.3L omc stalls/stumbles at acceleration

[illini]

Is there really a difference between the ac delco MR43T that the boat calls for and a regular R43T plug? I have also been having problems with the engine wanting to stall when I give it gas. It idles fine. It has sat since last year because of a bad fuel pump wire I never replaced until now. When I first fired it up it ran OK as long as the jumper cables from my truck were hooked up to it. As soon as I pulled them off it started to act sluggish. The plugs are black, and have a minor smell off gas but are not wet at all. By the way the motor is in a 1992 19foot Seaswirl. The motor is a 4.3L OMC (GMC) Thanks for any advice you can give me.<br />What should the timing be set at?

 

[jlcjtc]

Re: 4.3L omc stalls/stumbles at acceleration

i have just replaced my plugs, the guy that had the boat before me had autolite plugs in there. it seems to me that things run better if you use the marine grade stuff. it may cost a little more, but i think it is worth it in the long run, also you made need to check your battery and alternator for the current output. my recommendation on the plugs is champion.

 

[magster65]

Re: 4.3L omc stalls/stumbles at acceleration

illini, It sounds like your battery is toast... or at least in need of a good charging. Your plugs are black because your ignition is running on too low of voltage. Before you do anything else get your battery fixed up. That may fix your 'stumble' off idle too.<br />I've never had much luck with Champion plugs... I use bosch

 

[illini]

Re: 4.3L omc stalls/stumbles at acceleration

I have pulled the battery out and plan on charging it overnight. The alternator is putting out plenty of voltage, so I hope this helps. I bought the Marine grade plugs and will put them in tommorow. I also plan on removing the gas and starting from fresh. I hope to set the timing also as I found out it is 6 degrees BTDC.

 

[illini]

Re: 4.3L omc stalls/stumbles at acceleration

Charged the battery, changed the plugs, and set the timing. I even took the bowl off the carb to make sure I didn't have a float sticking. Problem still there!!! If I pump up the carb real good before I start it I can rev the engine for about 5-10 sec before it starts to run sluggish and want to stall unless I go back to idle. I notice a huge difference in the volosity of the fuel entering the carb while it is reving and while it is running rough. I think the accelerator pump is OK so I am starting to question the fuel pump. It is an external electric pump and am wondering if it is weak.

 

[joeG]

Re: 4.3L omc stalls/stumbles at acceleration

Have you changed your fuel filter on the electronic fuel pump? Also, a good way to check if your accelerator pump is bad is to have one person at the throttle and the another person looking directly into the carb. With the motor off, have the person at the throttle push it down fast (as if you want to accelerate) you should see two good streams of gas being dumped into the carb. You also might want to try some gas treatment in your tank, you may have water in the tank or carbon build up in the carb. <br /><br />93 Four Winns 180 Freedom<br />4.3L OMC Cobra

 

[illini]

Re: 4.3L omc stalls/stumbles at acceleration

I have put new fuel in the tank and still have the same problem. The accelerator seems to put out 2 good streams when the throttle is moved. I am wondering if the volocity of the pump is enough? The local marina keeps telling me that they think I need my carb rebuilt at $320. It is a 2bbl Holley. Seems like I could by a new one for that price. Hard to find a mechanic in San Antonio, TX that is not a dealer and one I trust.

 

[Solittle]

Re: 4.3L omc stalls/stumbles at acceleration

Before you go nuts replacing this & that or adjusting all kinds of things, check your battery with a hydrometer.

 

[illini]

Re: 4.3L omc stalls/stumbles at acceleration

I will go get one tommorrow and check it, or take it to the parts store and have them check it. Just so I feel a little more enlightened, how can the battery cause it it want to die if the voltage reads fine when it is running? Doesn't the electronics run off the alternator at that point? It reads 13.9 and 14.3. Still does not want to run better even while putting fuel straight into the carb when trying to accelerate. Thanks.

 

[illini]

Re: 4.3L omc stalls/stumbles at acceleration

Battery checked good and so did the fuel pump. At a loss now. Any more suggestions?

 

[akriverrat]

Re: 4.3L omc stalls/stumbles at acceleration

if it still runs ok with jumpers on i would be looking for loose/corroded conections and high resistance in battery cables from internal corrosion/breaks.