Intermittent Miss / Rough idle / Wont Rev - fuel related? UPDATED!!

[ShawnQ]

Re: Intermittent Miss / Rough idle / Wont Rev - fuel related?

Re: Intermittent Miss / Rough idle / Wont Rev - fuel related?

Reading back a bit, you say you watched the mechanic rebuild the carbs from disassembly to assembly. This implies that the mechanic didn't soak the carbs.

You may still have gunk in 'em.

Let me reiterate that statement -

I pulled them off and took them to him. He soaked them, and invited me over the next day to watch him reassemble them.

He's been an OMC mechanic for over 30 years, and SHOULD know his stuff. I suppose that something could've possibly passed by him but I would hope not.

OB, I will try to do what you said and see what happens. I haven't checked the crankcase hose yet, but will shortly. I'm thinking I may have a leak somewhere between the primer bulb and the carbs...as I have seen a little build of oily residue built up in the lower shroud.of the engine. But, it could just be water that got caught in there and what not...I'm not sure.

I've run the engine for over 30mins at 4800-5200 RPM with no trouble at all, not even a hiccup. Drop down into the idle/troll speeds, and you never know when it will act up.

Thanks,
Shawn

 

[Saskatoon2005]

Re: Intermittent Miss / Rough idle / Wont Rev - fuel related?

Re: Intermittent Miss / Rough idle / Wont Rev - fuel related?

Replace all fuel lines and fittings. If it is a fuel problem then that will solve it. If it isn;t a fuel problem then you will find that out as well. It possible could be something as simple as the fuel pump....If you have to prime to get it to run smooth....usually indicated fuel source problems...LOL!

Patrick

 

[shep75]

Re: Intermittent Miss / Rough idle / Wont Rev - fuel related?

Re: Intermittent Miss / Rough idle / Wont Rev - fuel related?

Hey Shawn check out my thread about my 1995 Johnson 88HP SPL, I might have fixed my problem. Let me know if this could be the same for you, Shep

http://forums.iboats.com/bbBoard.cgi?a=viewthread;fid=28;gtid=1268869

 

[ShawnQ]

Re: Intermittent Miss / Rough idle / Wont Rev - fuel related?

Re: Intermittent Miss / Rough idle / Wont Rev - fuel related?

Hey Shawn check out my thread about my 1995 Johnson 88HP SPL, I might have fixed my problem. Let me know if this could be the same for you, Shep

http://forums.iboats.com/bbBoard.cgi?a=viewthread;fid=28;gtid=1268869

Shep, I'll take a look at the wire and see what it does when I remove it. I've got an evinrude, not a Johnson, but it should be identical.

Thanks for the info, and let me know how yours does.

I hope to dig into it again this evening. It sure is frustrating! I almost dropped $12K on a brand new Etec 150hp...and decided I'd better try to get this one going first d

Saskatoon,

All fuel lines, hoses, clamps, fittings have been replaced or cleaned.

Thanks
SQ

 

[jenoble01]

Re: Intermittent Miss / Rough idle / Wont Rev - fuel related?

Re: Intermittent Miss / Rough idle / Wont Rev - fuel related?

You may consider removing some of the excess length from you primer bulb hoses. I was having a similar issue and everything pointed to the bulb, replaced it and the issue got worse. Could't get the bulb to hold pressure worth a darn. then when fiddling with it this winter decided to cut the excess length from the primer bulb, holds pressure great now. Been to cold to try on the water so don't know if it fixed it, but I don't think it could hurt. Remember getting pull to the motor depends on a vacuum, the pump could be having a hard time overcoming the extra length of hose at idle due to lower vacuum. That's my story and I'm sticking to it, until I get to test it on the water at least.

 

[tashasdaddy]

Re: Intermittent Miss / Rough idle / Wont Rev - fuel related?

Re: Intermittent Miss / Rough idle / Wont Rev - fuel related?

wondering if that fuel fliter is to small a micro, not allowing enough fuel to flow? there again it could be a kinked hose. try to borrow a portable tank, and fuel line.

 

[ShawnQ]

Re: Intermittent Miss / Rough idle / Wont Rev - fuel related?

Re: Intermittent Miss / Rough idle / Wont Rev - fuel related?

jenoble,

So you're saying I should shorten the hose between the engine and the primer bulb?

I guess I could give it a shot, as it wouldn't hurt anything. However, the line that is on it is that length from the factory. OMC sold it that way...so I would think it would work.

I've also seen the same boat as mine, with the primer bulb tucked all the way in the battery box where my fuel filter is at.

I'm going to check a few other things but will definitely keep that in mind.

Thanks again for the idea.

SQ

 

[ShawnQ]

Re: Intermittent Miss / Rough idle / Wont Rev - fuel related?

Re: Intermittent Miss / Rough idle / Wont Rev - fuel related?

wondering if that fuel fliter is to small a micro, not allowing enough fuel to flow? there again it could be a kinked hose. try to borrow a portable tank, and fuel line.

I am planning to run it on a portable tank this weekend - either on the hose or on the water, not sure if I can get to the lake.

I may have to buy one, but so be it.

I wouldn't think the filter is the problem, but I suppose it could be. It would support the fact that if I press the primer bulb, it will run correctly (because it forces fuel through the filter).

SQ

 

[jenoble01]

Re: Intermittent Miss / Rough idle / Wont Rev - fuel related?

Re: Intermittent Miss / Rough idle / Wont Rev - fuel related?

jenoble,

So you're saying I should shorten the hose between the engine and the primer bulb?

I guess I could give it a shot, as it wouldn't hurt anything. However, the line that is on it is that length from the factory. OMC sold it that way...so I would think it would work.

I've also seen the same boat as mine, with the primer bulb tucked all the way in the battery box where my fuel filter is at.

I'm going to check a few other things but will definitely keep that in mind.

Thanks again for the idea.

SQ

yeah, they it was extra long when I purchased mine as well. Before I shortened it, it wouldn't prime for an hour, after I shortened it it holds prime really well, I would say at least two months now since I shortened it, I did check it last night and if finally had went down a little, about 2 squeezes and it's full again, before it took 10-15.

 

[ShawnQ]

Re: Intermittent Miss / Rough idle / Wont Rev - fuel related?

Re: Intermittent Miss / Rough idle / Wont Rev - fuel related?

Went out there this afternoon and couldn't find a black/yellow wire going into the power pack.

I pulled the cover off of the power pack and it looks clean as can be, no melting or corrosion.

I did notice that it looks like I have a leak in my exhaust plate, lower left corner...would this cause my issue? I wouldn't think so, but possible...?

There is a small amount of oily residue (carbon) that has dripped down from the lower left corner of the exhaust plate and into the lower engine cowling area.

Where is the hose that goes from the crankcase to the fuel pump?

Thanks
Shawn

 

[perkdp]

Re: Intermittent Miss / Rough idle / Wont Rev - fuel related?

Re: Intermittent Miss / Rough idle / Wont Rev - fuel related?

I couldn't really tell by the pictures but the pickup tube inside the tank looks alot bigger than the fuel lines to the motor. Could it be that at idle, the pump and bulb are not strong enough to overcome the distance and small size of the lines to the tank and keep proper vaccum to hold prime on the large pickup tube ?

Also, the primer bulb should have a working check valve in it to prevent back-flow / lost prime. If the valve is not working correctly / always, the bulb will get soft and lose prime.

With the length of fuel line you have, your motor would idle a long time just by pulling the gas out of the line.
This may have something to do with the lug you get from idle to wot.

 

[ShawnQ]

Re: Intermittent Miss / Rough idle / Wont Rev - fuel related?

Re: Intermittent Miss / Rough idle / Wont Rev - fuel related?

I couldn't really tell by the pictures but the pickup tube inside the tank looks alot bigger than the fuel lines to the motor. Could it be that at idle, the pump and bulb are not strong enough to overcome the distance and small size of the lines to the tank and keep proper vaccum to hold prime on the large pickup tube ?

Also, the primer bulb should have a working check valve in it to prevent back-flow / lost prime. If the valve is not working correctly / always, the bulb will get soft and lose prime.

With the length of fuel line you have, your motor would idle a long time just by pulling the gas out of the line.
This may have something to do with the lug you get from idle to wot.

The pickup tube is roughly the same size as the fuel line.

The primer bulb has been replaced, but I could definitely swap it again as they aren't too expensive. But, I'm pretty sure it is fine. I went out there today and primed the heck out of it...and will go back out tomorrow to see if it held the pressure or not.

As for the expanse of fuel line. It's got about 12-14' from tank to engine. The engine will idle for 30 seconds or more if I un plug the fuel line from the engine. So, I would assume it would run for a few minutes on just what is in the line.

I don't ALWAYS get the lug when going from idle to thottle. ONLY when the engine is loading up and hesitating. In good running operation, there is no delay. I am on full plane in a little over a second and at full speed in 4-5 secs.

Thanks
SQ

 

[mikesea]

Re: Intermittent Miss / Rough idle / Wont Rev - fuel related?

Re: Intermittent Miss / Rough idle / Wont Rev - fuel related?

ok,read it,re-read it,slept on it,back again today.My opinion is.Fuel pump.You changed damn near everthing else,as another poster also said,yes it pumps well at high speed,problem is bad at low speed,at that point you squeeze the ball,the problem goes away.With the restriction ,theory in the tank solved,if it wre me.Id buy a pump, you asked where the pulse hose is.It would come off the bottom of the fuel pump,you have one line in from the tank,another that connects to the plastic fuel barb that feeds the carbs ,and the pulse is going to be hard to see,to work on it you would be best if not essential to remove the pump,I have seen the pulse hose and the inlet at intake (where the pulse originates)plugged up with gunk preventing a good flow of pulse.With respect I dont think the length of the hoses have anything to do with your problem,many boats have tanks up forward and feeds that run many feet,as long as there are no kinks ,you should be ok,remember,you say it runs great all day at wide open throttle(wot)and restrictions f any kind would be most prevelant then.I like the fuel pump ?pulse opinion at this point

 

[ShawnQ]

Re: Intermittent Miss / Rough idle / Wont Rev - fuel related?

Re: Intermittent Miss / Rough idle / Wont Rev - fuel related?

Mike,

I'll look into changing that out.

Is there any way to check one of these pumps before dumping the money into it?

Thanks!
shawn

 

[mikesea]

Re: Intermittent Miss / Rough idle / Wont Rev - fuel related?

Re: Intermittent Miss / Rough idle / Wont Rev - fuel related?

there are tests,most manuals will explain them.But would you have the pressure pumps etc.I recall you should only be able to blow through one way and not be able to suck,On the pulse,I dont think you should be able to do either,hows that for a solid tecnical answer.Sorry,cant help you with the test.I didn't think the pumps were that expensive,I'm sure you can buy one through this site.I do know the newer VRO pumps break the bank and many people have gone back to the type you have to save money

 

[ShawnQ]

Re: Intermittent Miss / Rough idle / Wont Rev - fuel related?

Re: Intermittent Miss / Rough idle / Wont Rev - fuel related?

Mike,

$62.39 is what the local dealer quoted, and not in stock (doh!).

How large is the pulse/crankcase line? I saw a small (maybe 1/4"?) line running from the bottom of the plastic fuel bar and headed towards the side of the powerhead. Wasn't sure what it was for, but it may be the one we're looking for.

I may go pull the fuel pump off, open it up, and see if I can see any obvious damage. May as well try rebuilding mine as opposed to buying a new one, as it is only $14 for the kit.

Thanks
SQ

 

[ShawnQ]

Re: Intermittent Miss / Rough idle / Wont Rev - fuel related? UPDATED!!

Ok Guys, here's another thing I found today that could be my problem.

I ran the boat on the hose again today to try and test my theory that pumping the primer bulb would cure the 'rough idle/starving' symtpoms I am having. I did this at least 15 times, and each time I pumped the primer bulb, my rough idle/loading/starving would go away..

Just before the rough idle would start, the engine would rev-up, like a typical engine does when it is getting more air then fuel (lean), and then it would drop from 2000rpms to 700rpms and buck/run rough/almost die until I pressed the primer bulb.

I also noticed that if I would remove the fuel line from the engine at the quick-disconnect, the rough idle would smooth out as well, which I thought was odd. It would only smooth out for a bit, and then roughen up again.

Take a look below and let me know if the symptoms I am having are likely caused by what you see.

From the advice above given to me by Mikesea, I decided to pull the full pump off and open it up.

The pump part # is 433387, first of all, is this correct? I can only find this part # referencing engines up to 55hp? Do I have the wrong pump?

I didn't ever find a crankcase/pulse hose or line. I assume the pump is mounted directly to the crankcase/pulse port, no line attached at all.

Here's what I believe is the 'pulse port', in lieu of having a line...the pump mounts directly to this. The seal looked good and the gasket was fine:

Here's what I found inside the pump:

Here's one of the 'rubber flappers', for lack of better term, that looks to be permanently flexed the wrong way, possibly worn?

The other 'rubber flapper' (I have no clue what to call it) appeared to be missing chunks, not completely covering the 'ports' that it is supposed to. What kind of trouble would this cause? Would this cause the symptoms I am having?

I also found an area that may have had a bit of a bad seal...not sure if it leaked or not, but it wasn't very clean and definitely could've been leaking air or fuel:

So, do you think I've found my culprit?

If so, do fuel pump kits come with the orange rubber pieces I'll need? It is a simple pump, should be easy to repair.

Also, can canyone explain exactly how this pump works? I have no trouble disassembling/assembling it, but I'm not sure how it is all working.

Thanks!
Shawn

 

[shep75]

Re: Intermittent Miss / Rough idle / Wont Rev - fuel related? UPDATED!!

Shawn the power pack should be sealed with no cover. It is bolted to the top of the engine and wires that come from under the flywheel go to the power pack. The balck with yellow stripe wire goes to the power pack it should have a black qucik disconnect on it.

 

[ezeke]

Re: Intermittent Miss / Rough idle / Wont Rev - fuel related? UPDATED!!

In your second photo the arrow is pointing to the pulse opening. It goes into the intake manifold after the reeds and gets the pulse from the action of the piston. The closed opening just below it is where you would connect the VRO if you had one. The gasket between the fuel pump and the engine is critical.

If the membrane(s) are damaged the fuel pump will not keep the float bowls filled properly, will not provide enough fuel to the primer solenoid, and may allow fuel to go directly into the engine, bypassing the carburetors. There are other undesirable possibilities, as well.

I wish I knew how to help you fix the pump. I have never rebuilt one and never knew anyone who did. We just got new ones and kept going.

 

[shep75]

Re: Intermittent Miss / Rough idle / Wont Rev - fuel related? UPDATED!!

That was how my fuel pump bolted up to the block when I rebuilt mine. I got the Sierra pump kit #18-7800 about $15.00