Wont start without pouring gas

[ross_larter]

Hi,

My friend has 1994 PCM 5.7 v8 in a supra ski boat, it won't start in the morning without spraying gas down the carb from a spray bottle, once its started it runs fine and you can turn it off and on ok, but if you leave it for 20 mins it won't start again without more spray bottle action.
Any Ideas?

Cheers
ross

 

[tashasdaddy]

Re: Wont start without pouring gas

i would say a check valve is failing, and siphoning the gas off the carb. or and air leak in the system.

 

[Chris1956]

Re: Wont start without pouring gas

Ross, Is that a carborated model? If so, when first starting the motor, the choke plate should close and stay nearly closed when the motor cranks. Also, check that the accelerator pump squirts gas into the carb throat, when the throttle is pumped.

 

[Silvertip]

Re: Wont start without pouring gas

I suspect incorrect starting procedure such as not setting the choke and giving it a little throttle. Of course a malfunctioning or inoperative choke is certainly a possibility. Amazing how many people don't know how to start a carbureted engine anymore.

 

[ross_larter]

Re: Wont start without pouring gas

Its not the starting procedure, hes had the boat for a few years and its only started happening lately, where would the check valve be?

 

[Pst76]

Re: Wont start without pouring gas

Should be a fitting at the gas tank.Where the gas line goes to the fuel pump. There is a threaded fitting on the tank, then a fitting that the hose connects to. That fitting should be the antisiphone valve. Mine had gotten stuck over the summer. Same symtoms.

 

[Don S]

Re: Wont start without pouring gas

That check valve in the tank is not the problem. A symptom, but not the problem. The fuel pump itself is the check valve. Beside that the fuel inlet to the carb is ABOVE the level of the fuel, not below it, so there is no way for the fuel to pull out of the carb. IF fixing that valve cures the problem, it just covers up the problem of a bad fuel pump
If there is fuel in the carb, then the accelerator pump is probably bad. It's a common problem.
Even if the valve was bad or not in there at all, and the fuel leaked back to the fuel tank out of the fuel pump and the lines because the fuel pump was bad also, the engine would still fire and start with the gas in the carb, but die till the lines filled again.

 

[bruceb58]

Re: Wont start without pouring gas

I had a similar problem. It was the accel pump like Don said.

 

[Pst76]

Re: Wont start without pouring gas

MY Bad...Did not read correctly, the valve term through me. Don you are correct as usual. Mine was running dry under load. Accelerator pump in the carb had already been replace. The gas was not getting to the fuel pump. Spring and Ball were stuck restricting fuel through antisiphon valve..

 

[Zackman]

Re: Wont start without pouring gas

Ross, first of all be really careful with spraying gasoline especially with a hot engine. I have seen numerous times, where people have added gasoline directly to the carburetor and have caused a fire through the carburetor.

Based on your comments, it does not seem that the accelerator pump or your choke is your problem. To check the choke operation, do the normal startup procedure with the flame arrestor off so that you can see the carburetor. On top of the primary portion of the carburetor there will be a piece of metal that acts like a butterfly valve. At first this piece of metal should be perpendicular to the carburetor. After the normal startup procedure, this should close and only expose about ¼” inch of the throttle body. This will be the choke position. Don’t try to start the motor. If the choke plate is close to being closed use your finger to open the choke plate. Push the throttle lever quickly to the full open position while looking down the throat of the carburetor. As the throttle is pushed to the full open position you should see a squirt of gasoline, just a short stream near the top of the throttle body.

If these items look okay, then I would suspect that the carburetor is allowing gasoline to flow from the bowl into the engine when it is not running. If this is the case, the easiest solution might be to have the carburetor replaced with a rebuilt carburetor.

 

[Zackman]

Re: Wont start without pouring gas

Ross, let me add one more comment...

The 1st recommendation is based on the motor not running or attempting to start for an extended period of time.

After performing the above with a cold engine, trying cranking the engine for a number of seconds (not more than 5 seconds of so). Then try the above recommendations again. If you still don't see any gas squirting as you push the throttle level to the full open position you might have more than one problem.

During cranking, a good fuel pump should provide adequate gasoline to the carburetor to fill the bowl in short order.