1987 225 Evinrude VRO Pump rebuild question (now pump isn't working)

[DRCrowe]

I just rebuilt my VRO pump with a fuel side rebuild kit on my 1987 Evinrude 225. When I took the pump apart I found a torn diaphragm. I replaced all of the parts that the kit included except a small blue o-ring, large o-ring and duplicate parts (because they sent me 2 different kits and each kit had a duplicate part). The manual states that a plunger o-ring should also be replaced but I didn't see it in the kit unless it is the little blue o-ring that I didn't use (it didn't look like the right o-ring)

I put everything back in the boat, bought new snap clamps and hoses. I pumped the ball and fired the boat up. The only problem is the pump isn't pumping. The boat will run as long as I pump the ball but dies after about a min or so when the float bowls empty. It worked better before with the torn diaphragm!

I confirmed that everything is back where it is supposed to be with before and after pictures!
I am attaching pictures of
1. The parts I got (with notations)
2. The plunger o-ring in question that I did not get and am wondering if it should be replaced (with notation)
3. The current installation of my VRO Pump
4. The torn diaphragm just for fun!

Any suggestions would be appreciated!

 

[daselbee]

What about ref #6 on the drawing? That is easily missed.

 

[DRCrowe]

Thanks Daselbee! I didn't replace it as it wasn't in the kit but i did confirm that it was in good condition when I reassembled it.
I am going to swing by the closest service center and pick up parts that I didn't replace the first time tonight and rebuild the pump again. Can you think of anything else I might need?

I'm just surprised that it failed! I like to think of myself as a pretty handy guy and really felt good about this little project! I've had all kinds of fun on this motor! (flywheel magnets, stater, CDI's, Tilt trim motor, lower unit rebuild and I'm sure there is more! I got the other projects on the first try though!!!!)

 

[daselbee]

When pump is working, it has a very distinct audible click every few seconds at idle speed. So, I guess it follows that you could listen for that click on your non-working rebuild. If you hear no click, concentrate on the air motor side looking for leaks. If you do hear clicks, but no gas is pumped, then look at leaks (possible check valve) in the fuel diaphragm side.

Anyway that is the way I would go about it. I doubt the o-ring on the plunger shaft that you did not replace will have anything to do with the problem. It looks like that is on the oil pump side.

By the way, what is that glass looking tube on the input oil hose to the pump? Never saw that before.

 

[daselbee]

I guess you have seen this?

http://www.outboardmarine.co.nz/catalogues/VRO-pump-tests.pdf

 

[Rustywrench]

The little tube is called a sight tube. You could see if oil was present at the pump. Later OMC service manuals have test procedures for testing these pumps. Since your pump was working makes me wonder if you did just miss something? The parts replacement is pretty straight forward. As mentioned the pump is divided into three chambers. Largest is air motor, middle is fuel pump, & then oil pump. The wires on the end are the no oil sensor. Added in 1986. Everything works on one common shaft. If the air motor doesn't drive the fuel pump/oil pump motor runs out of fuel. Pretty fool proof as long as you don't become the pump! Prime the bulb without adding oil to the gas. Pumping the bulb does not make the pump work.
The part you failed is what we called the flapper. It seals the fuel pump diaphragm on its return. Lots of those failed as a result of the materials they are made of. Now made of Viton (brown ethanol resistant). The little o-ring you didn't use is for the oil pump piston. Would not effect this problem.
On a normal functioning VRO pump the reset spring (air motor should reset every 15 to 20 seconds at idle). This will be greatly sped up if the fuel supply side sees air or is restricted.
Things you could have missed: Been a while since I have done one so I am sure I will forget something.
Small reset spring on air motor in the center. If it is not in place then pump will not reset.
Air motor diaphragm is not caught all the way around outside diameter of housing. You will see this when you take it back apart. Later models have an o-ring to help seal diaphragm.
Fuel diaphragm assembled out of order? Flapper on wrong side. DUH! I've seen it done.
Fuel pump diaphragm also has to be caught around outside diameter. Again you will see this on disassemble.
If this is not original pump look at cylinder oil pump piston goes into. Has it moved out of its hole? Should be flush with plastic housing. If it pulls out it jams the fuel pump diaphragm & VRO can't pump. This happened a lot, but on later pumps. Similar to what test procedure is taking about, but cylinder for piston actually comes out of housing. That part can't be bought.
You will have to use test procedures for the bodies of the pumps. They have o-rings & check valves that go bad.
Last but not least don't forget to check your pulse limiter on the lpowerhead. On this model it screws into the crankcase. This protects the VRO from backfires in the crankcase. You can blow thru the device from each end, but a quick blast of air (compressor) from the motor side should make it quack like a duck! This squelches the pressure so it doesn't destroy the air motor. Hope some of this helps.

 

[DRCrowe]

Rustywrench, Your reply inspired me! I took the pump back off and slowly and carefully disassembled it and can confirm that when I pulled apart the air side I found that the inner return spring was not seated correctly. I thought I was really careful when I rebuilt the pump but somehow the center small spring was not seated as you said it might not be. I rebuilt the pump again and carefully tightened everything up including the snap hose clamps. I ran the motor for 20 min on muffs. I know this doesn't mean much but its 18 min longer than it did before and gets me on the lake for a formal test!!!

I was ready to throw in the towel and just buy a new pump, but am glad I read your post and took another shot at this. We are heading to the lake tomorrow. My twin 15 year old boys thank you too. We get to go to the lake now!

Daselbee, I tried listening for the click but couldn't hear a thing with the engine on muffs, it's just too darn loud! I will try listening again at the lake with the boat in the water. I have heard that if it clicks too often that it indicates an air leak on the supply side. I haven't had this kind of issue in the past but always enjoy educating myself and appreciate your efforts!

Again Rusty wrench and Daselbee, thank you so much for taking the time to reply to my post. I really enjoy working through issues and efforts like yours are invaluable to guys like me! I plan on monitoring this forum on the off chance I can help a guy like me like you have!

I will report back tomorrow after a day at the lake!​