4.5hp Evinrude fuel pump problem..?

[fishguy]

I posted before, but found out a bit more and thought maybe someone could help me out.<br />1983 4.5hp Evinrude, Integral fuel tank adn electronic ign.<br />It will take to bogging down for no reason....<br /><br />Ex: Fired it up and headed out to the island on a local lake..me and a friend, ran it WOT, trip took 15-20 minutes. Worked fine.<br />Had a swim, sat on a rock, jumped back in the boat, it went fine for about 3 minutes, then took to acting up.<br />It runs great, not a hitch, then all of a sudden the rpm's drop to idle...sharply. I hold the throttle in the wide open position, it stays at idle for about 3 seconds and then takes off again. No sputtering when it takes off again, just like I twisted the throttle from idle to wide open. <br />After that happens, it will go fine for about a minute, then drop again. Happens over and over once it starts happening. It will keep happening all the way back to the dock.<br />Once in a blue moon it will stall when the bottom falls out, but it will start right back up with one or 2 pulls.<br />If it was a bad/broken whatever, it would act up all the time... Not run fine for a ride one way, then run like a dog on the way back....<br />The popular feeling is that I'm starving for fuel....I've run it with the gas cap off and it still does it. I've checked the fuel lines and replaced the filter. I've also borrowed my buddy's external tank and removed his fitting at the motor end of his hose. I hooked that right to the fuel inlet on the carb.<br />Then ran up and down the coast with him holding his fuel tank higher than the carb...not an easy task. Still did it.<br />Soooo...I have a carb problem, or an ignition problem.<br />The carb's been off (more times than I care to count) and cleaned...no dirt, corrosion, water....<br />Jets are clear.<br />Now, when I remove the bowl, there is some kind of a spring dealy with a one way check valve....<br />Someone told me the name of it, but wasn't sure on it's purpose or operation. Some kind of a pump. But it's gravity fed..right?<br /><br />Is there an ignition component that could cause one cylinder to drop off, then come back a couple seconds later? (Heating up, then cooling down..)<br /><br />There must be someone out there familiar with this carb....any hints? Seen it before?

 

[fishguy]

Re: 4.5hp Evinrude fuel pump problem..?

Sorry, but just thought of a couple other things...<br /><br />Tis is not just a WOT problem. It seems to only rear its ugly head at WOT, then will continue doing it even if I run at 1/2 or 1/4.<br />Also, once it does it once, it keeps doing it. Runs good, dies off. a couple seconds after, comes back up. Then dies off again, then comes back again....will go on all day.<br />It takes about one minute to complete a cycle.<br /><br />I saw a couple posts from member with 25hp Evinrudes with what seems to be the exact same problem......last I saw obe guy had replaced a fuel pump and all seemed okay. but, I have no fuel pump, integral tank, gravity fed...<br />Perhaps I'm boating in no-gravity zones?

 

[Xcusme]

Re: 4.5hp Evinrude fuel pump problem..?

OK, before you start looking for an ignition problem, look again at the carb. The "some kind of a spring dealy with a one way check valve...." is the "float valve' for the carb. That needle valve (controlled by the float) allows more or less fuel into the carburetor bowl. If it sticks closed, your motor is starved for fuel. If it sticks open, your motor floods. A carb kit for your motor will eliminate all questions about a sticking float valve. The kit has all of the replaceable parts including gaskets etc.<br /><br />Only after I was sure I rebuilt the carb, and still had the problem, would I go on to the ignition system. A failing powerpack can heat up and cut out, only to cool a bit and start working again. This cycle can continue until it goes out completely. Intermittent ground connections can cause this behavior too. Bad electrical connections cause all kinds of weird symptoms.

 

[fishguy]

Re: 4.5hp Evinrude fuel pump problem..?

I should have been a bit more specific...<br />I'm familiar with the needle valve and float.<br />On this motor, the float bowl is the regular 'bowl' shape, but in a rectangular housing. Off to the side of the housing is the item that I was refering to. I posted in another forum and got a response back from someone -<br /> "In that carburetor, behind the fuel inlet fitting is a "bladder" which is simply listed as "bladder fuel pump", also on that engine, there is another fitting and hose that is listed as simply a "pulse line". Frankly, I don't ever recall working on the 1983 4.5hp engine and I do not have any idea of the functions of these two items.... but with the problem you're having, I think it's something that should be looked at."<br /><br />I read that a lot of outboard fuel pumps use engine vaccuum to move a diaphram and thusly pump fuel....that would go along with the 'pulse line' (the vaccuum line) and the bladder fuel pump, but why would these items be used on an engine with an integral tank (Gravity fed)?<br /><br />A carb kit was going to be my next step, but I was hoping that a tech would say, "Oh yeah, that's the foofoo valve...they go on every 4.5 and they act up exactly like that.."<br />Wishful thinking, I guess.<br />I've had the needle valve out and done a close visual with a magnifying glass..I can't see any evidence of wear or irregularities on it that may cause it to bind, but the up and down rpms would go hand in hand with a float bowl running dry of gas. Except that it does it at 1/4 throttle too...and at the same frequency...I'd think it would take a few minutes to burn a bowl full of fuel at 1/4 throttle...or at least way more time to burn it at 1/4 than it would at WOT...<br />Off to try a carb kit tomorrow, I guess.

 

[Chinewalker]

Re: 4.5hp Evinrude fuel pump problem..?

The intermitancy of it leads me to believe it's an ignition problem, likely a coil going bad. Shut the motor off, pull the hood and then pull one of the wires off. Restart the motor and see if the motor sounds the same or doesn't start at all. If it sounds EXACTLY the same, you've got an ignition problem and it's only running on one cylinder part of the time. Listen for arcing of the coil to the block, possibly it's cracked? Maybe a wire got kinked and cracked? Try pulling the other plug wire and reconnecting the first pulled one and restart again. Being that it's intermittent, it may start, may not. If you can localize which one isn't firing, try swapping the coils top and bottom and see if the problem follows the coil. If it does, then it's a bad coil. If it doesn't, then it's a bad switchbox. A bad trigger usually results in BOTH cylinders not firing...<br />- Scott

 

[fishguy]

Re: 4.5hp Evinrude fuel pump problem..?

^ Bump ^<br /><br />Waiting for the darn rain to quit so I can get out and test a few things.....looking for feedback still