89 90hp Rude missing on one cylynder

[iwombat]

Re: 89 90hp Rude missing on one cylynder

What you're looking for is a fuel leak from the fuel pump into the hose (fuel pump is part of the VRO). When you pump the bulb does it stay hard? If not you've probably got a torn diaphragm in the pump.

 

[Dennisanoka]

Re: 89 90hp Rude missing on one cylynder

ok, so the VRO has the gas in hose and in my cas a gas out hose and the hose to the crankcase. You are saying to look for an air leak on which one or more than one? (Obviously no leaks are correct but should I focus one one or the other) And if I pump the bulb till it's hard should it stay hard indefinitely?

 

[Dennisanoka]

Re: 89 90hp Rude missing on one cylynder

ReelDutch or someone else, please explain why an air leak in the pulse hose could make the #4 any more rich than the others. I understand #4 gives the pulse but the VRO feeds both carbs(upperand lower) The signal just comes from #4. I hope you are right but I want to understand the "how come".

I have not run the engine for 3 days and the bulb was still reasonably hard. I was only able to squeeze it maybe a 1/4 squeeze 2 times and it was hard again.

I just checked the fitting going pulse fitting going into the VRO and it was not exactly tight. I put a new clamp on it and it is tight now. I'll look forward to replys to my question above.

Thank you

 

[iwombat]

Re: 89 90hp Rude missing on one cylynder

Lesse if I can shed some light here.

The fuel pump is run on pulses from the engine (#4 cylinder specifically). The pulses move diaphragms inside the pump. Those diaphragms are tensioned by springs etc. Anyway, the pulse line is only supposed to contain air from the engine. If a tear in one of the diaphragms internal to the fuel pump develops, the fuel pump can leak fuel straight into the #4 cylinder bypassing the carburetor and all that. This creates a rich condition in #4. If the fuel pump has a tear in a diaphragm it can often be detected by the bulb not staying hard (fuel is leaking out after all). You'll only find the bad diaphragm by taking apart the fuel pump. Visual inspection of the assembled pump won't spot it at all.

Alternately, if there is an air leak in the pulse line, air can get sucked into the #4 cylinder. This can create a lean condition in #4.

Either one of these could be causing a problem. However, the rich condition is more likely to cause the cylinder to not fire at all. The lean condition would probably cause it to run hot, and sputter.

 

[Dennisanoka]

Re: 89 90hp Rude missing on one cylynder

iwombat- you have shed suffecient light so that even I can understand it. I do believe you may have hit very close to the issue quite possibly right on the head. What makes sense now to me is how fuel could get only into the #4cylinder. Since when I inspect the VRO pulse input connector , it did appear to be wet and when I pulled it off before I re-clamped it, I could tell there had been some fuel present. So I do think you found it. I'll have to do some research to see if it can be re-built or just replace it with a new fuel pump. Would one approach be any better than the other? I will continue to post until this is brought to a successful conclusion. I have often been disappointed when these posts don't conclude what was finally found to be the solution.


Thank you for responding when you saw my issue.

 

[iwombat]

Re: 89 90hp Rude missing on one cylynder

No problems. I'm not familiar with VRO units, but I think the fuel side has a rebuild kit for it. Other than that, you can pick up a rebuildable fuel pump on ebay for well under $50.

Keep us posted on what you find. I get annoyed by people running out before posting the conclusion too. You'd think that's the least they could do for what they paid for the help they're getting.

 

[Dennisanoka]

Re: 89 90hp Rude missing on one cylynder

I did replace the clamp on the VRO pulse hose fitting since it was not snug. I took the boat out and it ran really well the issue was not detected. #4 was firing at low RPM's. Here's the BUT, when I pulled the plugs at home #4 and #3 were a little wet, not fouled. The electodes were wet but the center porcelean appeared pretty dry. I then disconnected the pulse hose and a drip of fuel came out the bottom of the vro pulse hose fitting fitting right at the VRO. Is that at all acceptable or does the pump need rebuilding or replacement. I do not use the oil pump section of the VRO.

 

[Walker]

Re: 89 90hp Rude missing on one cylynder

Check the recirculation valves. Their job is to remove excess fuel from behind the intake.

 

[reeldutch]

Re: 89 90hp Rude missing on one cylynder

sorry i couldnt get to you earlyer.

if i may make a sugestion?

this could be the scenario for your motor.

this is what i would do.

remove Vro pump and install the 88 fuel system.

plug the pulse limiter.
open the 88 fuelpump fitting.
put the regular style fuel pump on with the fuelrail and hoses for it.

you will be fixed for total of about $65 dollars.
new pump, T,hoses, clamps.

make realy realy shure the pulslimiter is airtight closed off.

thats what i would do to get rid of your problem.sinse your mixing your fuel yourself.


good luck.

 

[reeldutch]

Re: 89 90hp Rude missing on one cylynder

and do what walker said check the resirc system.

 

[Dennisanoka]

Re: 89 90hp Rude missing on one cylynder

Reel dutch,

I really appreciate your help on this. I was really headed off in the wrong direction before your post. I am going to pick up a fuel pump tomorrow but I would have thought that it too would run off the same pulse hose as the VRO, apparently not according to your post. My Cylmers manual does not show me where the 88 fuel pump fitting(s) is. Is there any chance you can enlighten me a bit more regarding that?
Walker- I did make sure the recirculation valves were functioning when I did the rebuild last year, but I will make sure none are pinched when I have things opened up tomorrow.
Iwombat- you can be assured I will post a final when all is fixed. I absolutely agree with you regarding getting advice. I have learned a great deal through this and saved $100's and the most important part I will KNOW it's fixed right when I'm done and why.

 

[iwombat]

Re: 89 90hp Rude missing on one cylynder

The fuel pump will run off the hose too. Reeldutch suggests plugging the pulse limiter. I'm not sure, but believe that's a different animal than the pulse port & hose. Again, I'm not familiar with the VRO units.

I'm gonna go peek at a parts diagram now though.


Edit: Looks like the pulse limiter (part# 0174404) sits between the pulse port and the hose. It also looks like the '88 fuel pump bolts up directly to the (another?) pulse port instead of using the hose. I think I'll drop off at this point and leave the details to someone more familiar with the specifics of this motor.

 

[Dennisanoka]

Re: 89 90hp Rude missing on one cylynder

I read:
"If your motor is older than a 1993, make sure it has the blue colored pulse limiter to protect the air motor and the check valves in the pump. Follow the pulse line from the VRO to the engine block and look for a hex shaped fitting threaded into the crankcase."

I know where that is, mine is the original black one but Reel dutch is saying, I think to plug it and get the pump pressure from somewhere else.

 

[iwombat]

Re: 89 90hp Rude missing on one cylynder

You could use the hose given the right fuel pump. But the '88 pump, (the "correct" pump) according to the diagram, has the hole in the back and the direct mount gasket.

 

[Dennisanoka]

Re: 89 90hp Rude missing on one cylynder

The local marine suggests the pn 438559. I have found that that one was used on a 70hp. It appears to be a 3 leg device 1 for pressure and two for the fuel. I assumed I would be connecting it to the same pulse hose as the VRO was. They did not tell me much over the phone and I didn't want to assume anything at this point. It is about a $60 part which is great.

 

[Dennisanoka]

Re: 89 90hp Rude missing on one cylynder

are you looking at diagrams at http://www.evinrude.com/en-US/Accessories/Literature/Engine.Diagrams.htm ? I can't get the site to work for me tonight.

 

[iwombat]

Re: 89 90hp Rude missing on one cylynder

The local marine suggests the pn 438559. I have found that that one was used on a 70hp. It appears to be a 3 leg device 1 for pressure and two for the fuel. I assumed I would be connecting it to the same pulse hose as the VRO was. They did not tell me much over the phone and I didn't want to assume anything at this point. It is about a $60 part which is great.

The diagram on the site (same one you link to) calls out p/n 0398387 for the same year '89 88hp. That three fitting model will work I think. Just be sure it mounts up on the engine someplace in a reasonable fashion.

 

[Dennisanoka]

Re: 89 90hp Rude missing on one cylynder

Ok I found the diagram for the 88 fuel pump and I see what ReelDutch meant about having to plug the pulse limiter if that exact pump were used because it was mounted directly on the crankcase and therefore is a two fitting pump. The pressure comes directly into the back. I think it might be easier though I am not yet sure to use the fuel pump # 438559 and run it from the pulse limiter hose. Can someone verify if this is a viable solution?

 

[iwombat]

Re: 89 90hp Rude missing on one cylynder

I have a sneaking suspicion it's the pulse limiter itself that's going to determine the answer to that one. Can you remove it and attach a regular fitting?

 

[Dennisanoka]

Re: 89 90hp Rude missing on one cylynder

Iwombat I see you're pretty sure the alternate fuel pump will work. If anyone has reason to beleive it won't or that it would sacrifice proformance in any way please let me know. Just for my own satisfaction I plan to disassemble the vro in the AM just to see if I can tell what the failure mode was. If you're curious I'll post my findings.