VRO pump change

[bonz_d]

Hey folks looking for info of help.

I have a 1987 Johnson 50hp that has been sitting in my garage for awhile now that I'm finally going to get to. The history on this one is that I'd picked it up as a parts motor because it had a complete working tilt and trim unit on it that I wanted. It had a blown out clutchdog in the lower unit and was also told it had low compression on one cylinder. Paid what I thought was a fair price for a working tilt unit.

After removing the tilt n' trim I had this on a stand and curiosity got the best of me. So I hooked up a battery and did a compression test on it. Top cylinder was marked with a paint pen as 140 and the bottom was marked as 130. What I got was 142lbs on both! So I then proceeded to connect some fuel to see if she'd fire up. Low and behold, 1st try and it was running but wouldn't stay running.. Run 3-5 seconds then it was like it was out of fuel. I also noticed the VRO was disabled. Anyways that was that and I started watching for a lower unit.

Well I finally got my little fingers on a nice lower for it and have it installed. Tried running it again today and same results. Like it runs out of fuel. I've got the top carb off and the gas that came out of it reeked. So I will be rebuilding both this weekend. Removed the VRO pump and the gas looked fresh and didn't smell but and uncertain if it's functioning.

The question I have is will a fuel pump from an 1980 50hp fit? I know there are conversions out there and that it can be done but can it be done using this pump? I've been searching the internet and seem to come up with many conflicting ideas as to what will work and what wont. OR I'm just confused and am not following correctly.

Right now my intention is to just get it running so I can go thru it more thoroughly and then to replace the VRO to functioning again.

 

[racerone]

There is only one way to do this.--Find the part # for a 48 hp model.---Remove the pulse port plug on the side of the top cylinder and install that pump with 2 screws and a gasket.----Plug the pulse port for the VRO.-------Mix at 50:1

 

[bonz_d]

Thanks racer, already have that part number and have located the plug on the top cylinder.

I have looked at the 48hp pump and cannot see or tell a difference between that one and the one from the 50hp. Any clue what the difference is?

 

[Bosunsmate]

There is only one way to do this.--Find the part # for a 48 hp model.---Remove the pulse port plug on the side of the top cylinder and install that pump with 2 screws and a gasket.----Plug the pulse port for the VRO.-------Mix at 50:1

????...................... Looks like the same pump to me as the 50hp, same part #s

 

[bonz_d]

Well here's were I'm at. Cleaned and rebuilt both carbs on it yesterday and then cleaned/flushed all the old fuel from the VRO pump. Then through all the hoses and checked them for cracks or deterioration. Cut back a few of the hose ends that looked distorted from being on the fittings and then reassembles everything.

Engine started right away but still doesn't idle very well and then cuts out after a few minutes. Again like it runs out of fuel So at that point I wasn't sure if there is a loose fitting and am sucking air or if the fuel pump part of the VRO pump isn't working correctly.

Today I pulled the VRO pump and replaced it with another old style pump from another 50hp and everything fit together very nicely.. Plugged up the pulse port and then tried again to run it. Again started right up but still will not idle long and still shuts down only now I find that the must be a leak somewhere as the primer bulb will not stay hard. I did notice a little more exhaust smoke with the old style pump.

Back to the drawing board!

 

[Bosunsmate]

might be a pick up leaking air in the tank

 

[bonz_d]

might be a pick up leaking air in the tank

I doubt that because I use this same tank on other engines w/o a problem.

 

[racerone]

Facts, primer bulb does not stay hard once motor starts and it does not need to be hard when motor is running !!!-----Fuel pump does not affect amount of smoke from a motor !!

 

[Bosunsmate]

So the corollary of that, if you keep priming it will it stay running?

 

[bonz_d]

OK, maybe I misstated that. When I quits the bulb is completely soft as if there is no fuel in it. It will pump up though. I mentioned the smoke because this is the same fuel I was using yesterday and the only change made was to the fuel pump. So I don't know why I was noticing more exhaust smoke.
I hadn't tried pumping the bulb other than after it has quit and then again it starts immediately back up.
I did also leave the large inline fuel filter in place from the VRO pump. Maybe I should remove it?

 

[Bosunsmate]

Maybe that crankcase compression/vacuum is down so you arent getting a good pump, which might be what they meant by low compression.
Id take off that filter at least for the time being

 

[pn]

let me get this right, once you prime the primer it gets hard, motor starts no problem and then dies, then bulb goes soft. well after it shuts off check your float bowls to see if the got gas or not, i'm guessing it's going to be empty meanings pump not working or something in-line is causing a restriction, gas tank venting, primer bulb check ball stuck or backwards(strange but it happens), air leak somewhere in the line , gunk in filter, etc. note:sometimes a diaphram leak is hard to see, very small, or in the grooves, hold it upto the light... also, burried vro in garden helps the vegetables grow.

 

[bonz_d]

Haven't had a chance to get back outside to work on it as the weather has turned to crud.

Had already check fuel to the carbs and that is good. It was running better on the VRO fuel pump than on the regular pump. So I don't know yet if there is a problem with that pump. May have to reinstall the VRO pump and start over.. I do believe there is a vacuum leak somewhere in one of the lines.

 

[rolmops]

I would replace all the fuel lines with new ethanol resistant hoses. The 1987 VRO is NOT what you want on that engine. These are the old ones that will change their mix and go to 1:100. They are responsible for a lot of set up engine blocks. You should either use a regular pump and mix your own or buy a 1993 and up vro replacement which will keep your mix at 1:50. My suspicion is that you have a pin hole in the fuel line before the pump. This will cause air to be sucked in instead of fuel.Make sure that the diaphragm in the pump is in good condition.For sh**s and giggles, try and run it with the cover off. If it runs good without shutting off after a while,you probably have a leak in your exhaust system and exhaust fumes fill the cowling. When that happens,there will be no oxygen to go into the carbs.
The engine running better on the VRO pump, means that there is something wrong with the other pump or that you did not close off the vro crank case hole.

 

[bonz_d]

Thanks rolmops,
All work is being done on a stand, on muffs and with the cover off. I have seen the kits for the upgrade to the VRO system and that may be something I'll look into if and when I can ever get this straightened out and running smooth. Also seems that what I've read so far about the VRO system is that there are 3 generations of pumps. The 1st being for 1985-86 and there was no electrical to them, Then the 3 wire and now the 4 wire and from what I've read the new ones are supposed to be able to be rebuilt.

As stated earlier I did go through all the hoses and they looked real good. Some I just cut off .25" because they felt loose because of the hose barb.

Now thinking about this a had read in the manual about using the snap clamps on all the fittings and most of these were put on with zip ties which is what I used to replace the ones I'd cut off. The manual states that zip ties will not tighten properly to seal the hoses so I now wonder if this could be part of the problem and why I may be sucking air?

Another thought on this engine, from everything I've read and seen over the past few years is that when these engines have compression problems it is normally the top cylinder because of heating issues. Well on this one it was supposed to be the lower cylinder that was low. Yet when I 1st started on this the compression readings I got were almost even between the two. Then after starting on the VRO I realized that the pump on these is pulling vacuum from the bottom cylinder and not the top one like the non-VRO engines do. So it now makes me wonder if that is the cause of the low reading the PO got. Thoughts?

 

[rolmops]

Pinholes in hoses are invisible.The clamps and pinholes may be sucking air. Replacing them is cheap and takes one possible problem out of the equation
The VRO is not really pulling vacuum. It just pulses the air that is in that little piece of hose. The pressure in the cylinder is created in the cylinder by the piston.
Often after the engine has run and is warmed up,the compression numbers are different from cold testing and they are more accurate. Try compression testing again with a warm engine that may solve that question and eliminate another of the possible problems.
Did you make sure that the cap on the fuel tank is loose?

 

[racerone]

The VRO pump " airmotor " uses a + pressure pulse directed to one side and a weak - pulse directed to the other side.-The rectangular piece under the airmotor uses check valves to do that.---Operation of the VRO does not effect compression readings in the cylinder.-----Low compression in the cylinder may mean that you get a weaker + pulse and a weaker - pulse in the crancase.-That does have an affect on how the VRO pump works.

 

[bonz_d]

Thanks racerone,
I got thinking about that compression question after I posted it and then realized that the two are on opposite sides. Either way the compression readings I got were even so I don't know how they got a low one.
As this is the 1st VRO engine that I've owned and worked on so I'm still learning and any education is always greatly appreciated! What's your impression on using the factory hose clamps? Is there really that big of a difference?

 

[racerone]

Ty-wraps are easy and work just fine.--------Those fancy plastic clamps do not last.

 

[sumocomputers]

bonz_d

Not disagreeing with racerone on the longevity of the snap clamps, since I don't know how long they last.

My manual specifically states that for the oil supply system connections, they must NOT be tiewraps or worm clamps, but must be snap clamps. They even have a little picture of the former with an "X" through them. See photo here: https://dl.dropboxusercontent.com/u/2466418/Uploads/2015-04-22 07-40.pdf

I ended up using the snap clamps for all the fuel and oil connections, into and out of the pump. Once it goes into into the carb/primer solenoid tee thingy, I used tiewraps, since the manual showed these as the correct type of connection.

Up to you if you want to follow the manual or not.

I found the "snap clamps" or "snapper clamps" hard to find online or locally, so went on eBay and got them for about $1 each (in a pack of 10), and now have a bunch of sizes for whatever comes up (I think I have sizes #4-12, but most of this stuff will use size 6 or 8). They are easy to over tighten and break, so just squeeze them until they are tight; you will know when you have reached the limit. Also, I like that they are removable and reusable, to a point.