fuel delivery question

[TheBlitz]

I am trying to troubleshoot my problem. I have a 1993 135 black max. Bought it used and so far its been a great motor. Only recently the last couple of outings I have been having some issues with fuel delivery. After about 4-5 min the engine will just slowly stall out like it ran out of fuel. If I accelerate it also will die. I am thinking its probably the fuel pump because in order to keep the motor from stalling I can simply manually prime the bulb and it will continue to run.

Someone on here suggested that I unplug the fuel line from the motor and prime the bulb and see if it holds firm. I tried it tonight and it does not hold exactly firm it starts to lose pressure and simply by squeezing it again it gets full quite quickly.

Do you think it could be as simply as a bad primer bulb with the valve stuck open? What do you think?

 

[ondarvr]

If the bulb becomes hard its done it's job, slowly losing pressure won't cause the motor to die, it only means the valve leaks a little, once the motor is running the valve does nothing. It could be an air leak or the fuel pump, fuel line connectors are a frequent place for air leaks.

 

[Chris1956]

The fuel pump can easily be rebuilt. Pick up a rebuild kit and service manual as you may need it. I e., after you install the fuel pump check valves, you need to break off the stems, which is a bit strange.

 

[gm280]

^+1

 

[444]

My bet is your fuel pump needs a kit.

 

[TheBlitz]

just an update. I know I am probably fixing this problem with a bit of over kill but I purchased a new fuel pump, new primer bulb with new lines, and a check valve for the gas tank autally removing the check value and just going with a straight line so I dont restrict any fuel flow.


The comment above about having to break off the check values on the fuel pump im not sure I follow?

 

[TheBlitz]

The fuel pump can easily be rebuilt. Pick up a rebuild kit and service manual as you may need it. I e., after you install the fuel pump check valves, you need to break off the stems, which is a bit strange.

sorry for the 20 questions chris. Do i have to do this if i do the rebuild kit route nly cause i ended up just buying the whole unit new and pretty sure i shouldn't break anything off correct?

 

[Xerveras]

Recently I was troubleshooting an outboard and my neighbouring tech provided me a tip when it would stay running (I assumed a carb issue) and he told me to keep priming the bulb - if it doest die out it would indicate the pump is starting to go. But its a good thought when troubleshooting the fuel system and thats what you are doing. My trade schooling was very keen on pushing for techs to really troubleshoot the system thats faulty, as the issue could be one or more than one things. You could swap/rebuild the pump, but maybe its the carb or fuel connections? Maybe its a combination? Ideally you would measure the fuel flow from the pump and into the pump to determine if its within spec and not faulty.

But you definitely covered your ass by doing/getting all that. If you bought a whole new pump you wont have to worry about breaking anything off, its for the rebuild kit, but i would ensure the manual says to do it lol.

 

[TheBlitz]

Hey Xerveras thanks a lot for your post. I would call my mechanical skills average. I am a fantastic youtube learner, but unfortunately I cannot find anything online. The manual that came with the pump has a variety of setups so they gave me a ton of spare parts depends on my setup. When I heard break something off I went...wow wait stop im not going to break anything off my new pump setup so thanks for clarifications.

I would assume once I pull my engine cover off and locate the old fuel pump i should be able to disconnect old fuel lines, unbolt old fuel pump, bolt on new fuel pump, reattach existing fuel lines and call it a day? I dont want to underestimate the swap so thought I would run it by you guys first before diving in.

Does this logic make sense. It came with a bunch of rubber lines would you guys both cutting and using the new lines or just use the existing ones from the old pump?

 

[Chris1956]

Since you are installing an entire new pump, you should not need to address the internal parts. Inspect the fuel and pulse lines and see which ones are bad and replace them.

Just to be clear, when you are rebuilding the fuel pump on that motor, the check valves are secured by plastic rivets. After the rivets are installed, there is a piece of the plastic rivet "stick" which protrudes. This needs to be broken off.

 

[Dekker500]

Not familiar with that engine, but since you are doing a complete replacement instead of rebuild, ensure that when you take off the old pump, if there is a gasket between the pump and carb, that you install a new gasket (did your pump come with one?) or carefully remove the old one and install it in exactly the same orientation on the new. Sometimes gaskets seal/stick so perfectly to old parts that it is easy to forget to remove them.

 

[DavidMoore]

Also the fuel pump is operated by pressure changes withing the crankcase, you will see the pulse hole when you remove the old pump. For optimal performance of the new pump make sure the hole is not partially blocked.

 

[TheBlitz]

install went well. Replaced, fuel pump, check valvue, new fuel lines, and primer bulb. Not sure which one was bad but installing them all resolved my issue. Thank you again for all your help!