Idle Problems

[qystan]

Re: Idle Problems

I had a recent bout that is similar. Engine ran ok, later would stall out intermittently, then idling became difficult, sometime idle will fluctuate, finally exhibited the same symptoms you are having.

Turned out to be the hose between the tank and the filter. Its an outboard engine fuel hose (can't make out the manufacturer). It has 2 layers and the inner core layer disintegrated into small bits choking up the filter and the fitting barbs.

Some the stuff melted somewhat and found its way all the way to the carb inlet screen and settled into a film, choking off the supply.

Remove the fuel filter, blow through the lines to clear. Remove the carb inlet filter and clean it. Install a new fuel filter and try again.

Another possibility is an air leak in the fuel lines & components between the tank and the pump. This will cause loss of suction. Replace the flex hose, check line connections, filter tightness, fittings.

 

[Zero Balance]

Re: Idle Problems

OK this is going to be a rough guess but I just went through the same issues. You say that you had to change your intake when the boat was purchased. Did you use the same carb/intake gasket? Are you sure that the gasket is right for the intake? Is the gasket the type that have four holes, two large two smaller then a larger block toward the front? Look at the intake with the carb off. If there are two valleys running from the front of the throat toward the intake holes and the gasket when installed covers these valleys then there is a good chance it's the wrong gasket. You say the carb was rebuilt? There are several gaskets to choose from in the kit. you'll want to choose the gasket that is illustrated as good for all models. Before pulling the carb run the boat and spray WD40 around the carb base and intake gaskets to assure no leakage. Second I'd check the gasket. If these dont help check the rebuild or rebuild the carb use carb boil and clean the idle screws. check your manual for initial adjustments and set the adjustments as indicated.

Good Luck

 

[Brandma]

Re: Idle Problems

Here is the deal guys. I tested the mechanical pump with a hose going into a spare tank of gas at the input. I had the output going back into the spare tank as well. I primed the carb so the engine would run when I turned it over.
The pump did the same damn thing. At initial startup it pumped one or two strong shots of fuel and then nothing while the engine idled on the fuel in the carb. What was really weird was that I thought I was about to run out of fuel in the carb so I poured some more in the carb tube. This flooded the engine and almost bogged it out. Suddenly I get a few more strong blasts of fuel out of the pump. The engine recovered from the flood, the RPM's came up again and the nothing out of the pump again. So this is it, I have a mechanical pump that will run the motor at higher RPM's on the water, (+1800) but will not keep the motor running for more than 30 seconds at (-1800 to 0) RPM's. The reason why it starts again fairly quickly is because the carb gets a shot or two of fuel right before the engine dies.

I took the mechanical pump off and hand tested it (pumping the lever by hand). It works fine. I checked the push rod length against a new one and it's the same. As strange as it seems I believe the problem is on the cam lobe. As I said earlier for 3 years this has been a problem. Since I don't idle much or for very long, I got by. But I think the motor has had a cam lobe issue since day one. That's what eventually burned my valves this year, blew the head gasket...

Screw it. I change it over to a Holley electric fuel pump this weekend. Problem solved. It ran fine after the switch to electric. I now have a $120 dollar mechaical pump for sale if someone is interested. Thanks for all the help. I learned allot, but what a freaking pain this has been. I'll be interested when this motor finally needs a complete rebuld to see what this cam looks like. See ya!

 

[Coors]

Re: Idle Problems

You could still have a suction leak in the hose from the tank to the pump; the electric might be stronger than the mech. pump. The higher rpm/faster spinning mech pump might be over-coming the leak, but still running you lean at wot.

 

[hullofalottatrouble]

Re: Idle Problems

scratch that

 

[capecodder116]

Re: Idle Problems

You do not mention if your new electric fuel pump is for marine applications ....As I found out myself, the marine pumps require an additonal safety switch which needs to be mounted in conjunction with your oil pressure sending switch. Without this additional switch, if your engine stalls, and key is in the on position the pump will continue to pump fuel into the carb/bilge and you don't want this to happen....BOOM...!!!!!

 

[John_S]

Re: Idle Problems

Do you have a roller cam?