Cold Start Problems 5.7

[Oskarol]

Hi All,

Looking for some help here. Have an issue with cold starts on my 97 5.7GL.

After the boat has sat for a day, I cannot get it started without putting fuel into the carb. The carb is a holley 2bbl. It will crank and crank but never catch.

The choke is closed but when I look down the carb and advance to full throttle, I do not see any fuel being squirted or get any strong smell of gas. I should right? I also don't see any leaks to indicate gas is leaking externally out of the bowl. This issue just started a few days ago and I'm not quite sure what to try that isnt a carb rebuild. Any thoughts?

Once you get it started for the day, it will run and restart without a problem for the rest of the day.

 

[Oskarol]

Just to add my starting procedure has always been to set the choke with one wot pump, bring it back to fast idle and crank. It has always started right up so something has changed.

No other symptoms when running, no stumble on acceleration, nothing. Just a painful cold start.

Should I try pumping the throttle while cranking?

 

[Oskarol]

Okay, I've been messing with this all morning.

Narrowed it down to the accelerator pump. The accelerator pump arm was stuck in the down position. I can manually lift and lower the arm, which causes gas to squirt, BUT it does not return to its neutral position once throttle is let off. What I mean by this is the arm goes down, which squirts gas, but will not return back once I remove pressure on the arm.

What causes that arm to return to its position? Is it the diaphragm that pushes it back or is there some sort of spring?

 

[jimmbo]

Easy Carb to work on, I have it on my 5.7 in my Avatar.
You are probably on the right Track, looking at the Accelerator Pump.
Is the lever sticky/slow to respond? It might just need Cleaning, if that doesn't help...
It is quite simple to take apart. Remove the Fuel Line from the Inlet on the carb. Remove the 4 Screws that hold the Fuel Bowl to the Carb. You don't even have to remove the Carb from the Engine, but put rags under it bowl to catch the gas that will spill out. You can also remove the Metering block and clean it out, spraying a good Carb Cleaner in all Passages. The Accelerator Pump is easy to take apart, and there is just the Cover(with the Lever) a Diaphragm/Gasket, and a Spring that pushes the Diaphragm away from the Fuel Bowl. In the Fuel Bowl part there will be either a neoprene Check Valve
or a check ball

either of these are what prevent the Pump from pushing the Fuel back into the Fuel Bowl.

There is one thing you need to check upon reassembly. Sometimes a New Diaphragm is a little thicker/thinner than the old one. There has to be some Clearance between the Lever and the Cam follower that activates it, when it reaches Full Throttle. When the Throttle is Wide Open, the Lever needs to be able to move about 0.020" more after WOT. This to prevent the Accelerator Pump from being the WOT Stop, which will result in bent Linkages and possibly broken Parts. Do Not confuse that with Clearance at Closed Throttle, there you want none. Adjust this only if needed to get the Clearance at WOT

 

[Oskarol]

Okay, so spent a bit of time on this. Removed the accelerator pump, cleaned everything up. Diaphragm looked ok. Spring may be a little tired, however, it turns out the tuning of the pump was way off and I was at the bottom of the pump stroke. Readjusted as indicated and the pump now works well, squirting gas as soon As throttle is applied. Gave it a cold start and it fired right up.

Not sure how it got so out of whack but either way, I think it's good now. And a diaphragm and spring are likely needed in my near future. Thanks for the help.