Is it the Fuel Pump or Carbs????

[Pokertrampp]

I purchased a 1988 120hp Johnson Outboard abou 2 months ago, it ran great when I first used it then it started running a little rough and now it will only run if I rev the throttle up. is this the fuel pump or do the carbs need to be rebuilt. I do not know when the carbs were rebuilt last or anything else about the history of the motor, but I dont want to mess with the carbs if this sounds more like a pump issue. can I connect an electric fuel pump to test it or will this do more harm than good? thanks

 

[ondarvr]

Re: Is it the Fuel Pump or Carbs????

Start by cleaning the carbs, you need to know they're in good shape anyhow and its not hard.

 

[Pokertrampp]

Re: Is it the Fuel Pump or Carbs????

Start by cleaning the carbs, you need to know they're in good shape anyhow ands it not hard.

While I agree with your suggestion and it was my first thought , there are four carbs on this and at $20 a piece plus the time to link & sync, I dont want to just start throwing money and parts at it hoping I get lucky. but I do plan to rebuild the carb soon I was just hoping the symptoms were tell tale of something specific. any other ideas?? thanks

 

[crherman]

Re: Is it the Fuel Pump or Carbs????

Always obey your captain! Really what Ondavr says is right on. You could try a rebuild kit for the pump if ones available (they are fairly inexpensive) but if you start with the carbs you will be zeroing in whats usually at fault in fuel related problems. To be the wisest with the money go with the percentages. Just scroll through all the posts about troubleshooting rough running or stalling engines. No one will be able to tell you with 100 percent accuracy, so imagine you only have (ask the audience) lifeline left. What do most all the posts say about fuel related problems????????

 

[Pokertrampp]

Re: Is it the Fuel Pump or Carbs????

Always obey your captain! Really what Ondavr says is right on. You could try a rebuild kit for the pump if ones available (they are fairly inexpensive) but if you start with the carbs you will be zeroing in whats usually at fault in fuel related problems. To be the wisest with the money go with the percentages. Just scroll through all the posts about troubleshooting rough running or stalling engines. No one will be able to tell you with 100 percent accuracy, so imagine you only have (ask the audience) lifeline left. What do most all the posts say about fuel related problems????????

well since I can not find the fuel pump kit or new pump here on iboats i guess ill go with carbs and see what happens. thanks

 

[5150abf]

Re: Is it the Fuel Pump or Carbs????

Disconnect a gas hose after the pump and crank the engine, if gas comes out it is your carbs ,obviously have a fire extinguisher handy and use some common sense when doing this but it is the easiest way to find your problem.

For whatever reason the put the high speed jet in the bottom of the float bowl so it gets clogged pretty easy, any dirt that goes into the carb gets in that jet.

While you are working on it change all your 21 year old gas line too, from the tank to the carbs, when it gets old the inside starts flaking off and it will clog your carbs over and over.

You don't actually need a carb kit just pull them apart and clean the jets and passage ways

 

[kenmyfam]

Re: Is it the Fuel Pump or Carbs????

As said above. Run your pump output line to a container. Disconnect or remove plug wires. Put the muffs on if not in the water. Prime the bulb. Crank motor and watch the output into the container.
Continuous strong spurts = healthy pump
Strong spurts tapering off as you continue = pump starting to fail.
Dribble or nothing from pump = failed pump.

Do Not use an electric pump !!!

Great time to do a carb service as well.
While you are at it how is the water pump and lower unit oil ??
My 2 cents

 

[kenmyfam]

Re: Is it the Fuel Pump or Carbs????

Here's a link to the "Top Secret Files"
Well worth the time to read.

http://forums.iboats.com/showthread.php?t=299680