QD21 Fuel Pump #377927

[64osby]

I know these are obsolete and can be replaced with a 18-7351, possibly others.

I look at the pump I have to wonder if there is a way to make or use another diaphragm to get this running / pumping.

There are rebuild kits / diaphragms that look similar in size.

It appears to be a really simple fuel pump, was there a problem with it?

 

[kfa4303]

Re: QD21 Fuel Pump #377927

Hi 64osby. I had an old QD-22 that was great. I'm not sure if they make a rebuild kit for its fuel pump, but here's a link to an OMC fuel pump rebuild for other/similar style pumps. You can also buy one that may work, if need be, from the link below.

http://www.sschapterpsa.com/ramblings/Rebuilding_fuelpump.htm

http://www.aircraftspruce.com/catalog/eppages/mikunifuelpump1.php

http://www.sschapterpsa.com/ramblings/johnson_QD.htm

 

[64osby]

Re: QD21 Fuel Pump #377927

Would the Mikuni df44 single work on this motor, it's rated at 14 liters per hour.

Shown first pic upper left http://www.mikuni.com/c-fuel_pumps.html

 

[HighTrim]

Re: QD21 Fuel Pump #377927

Yup, Ive used it on a QD

 

[kfa4303]

Re: QD21 Fuel Pump #377927

High Trim, would you have to remove the back nipple to mount it flush to the power head, or is there another way? There may also be other pumps on that site which may be more appropriate. I just posted it as a place to start. They seem to have them for way cheaper than a lot of other retailers.

 

[64osby]

Re: QD21 Fuel Pump #377927

Thanks HT, going experiment and to see if I can mount it in a creative manor.

 

[HighTrim]

Re: QD21 Fuel Pump #377927

I hmmmed and hawed for a while and found under the carb as the best option for me. I found it used the least amount of fuel line (ideal) and was out of the way. Most importantly, the cowl still shut

 

[Arctic 33]

Re: QD21 Fuel Pump #377927


Mr High Trim was right on the money with under the carb. It is a little tight.
Just finished this up a couple weeks ago.

 

[64osby]

Re: QD21 Fuel Pump #377927

Arctic, nice pictures. Thanks

 

[64osby]

Re: QD21 Fuel Pump #377927

So I have a Mikuni df44 -211 fuel pump in hand to convert to over to a newer tank.

I was thinking that the pump could be made to work by using the nipple on the manifold, the check valve has been removed and one side plugged. The more I read it seems this method is only used on the 5.5hp motors.

Will this provide the desired pulse to run the pump?

Tapping into the bypass cover is the other method and I understand how and what to do if the above listed plan doesn’t work.

 

[HighTrim]

Re: QD21 Fuel Pump #377927

Im not smart enough to know why, but for some reason the larger hp motors seem to like having the bypass cover tapped for the conversion rather than modifying the manifold. Maybe F_R can shed some light on why. Try it and let us know how it works for you, just personally for me I have found they ran better the other way.

 

[64osby]

Re: QD21 Fuel Pump #377927

To clarify, this Mikuni is going on a 1958 Johnson 10hp QD19. Not the QD21 as the title says, the 21 provided parts for this.

 

[64osby]

Re: QD21 Fuel Pump #377927

I ran a test today with the Mikuni pump hooked to the manifold nipple. I ran lines to 2 open containers for fuel in and fuel out. Used a very old 1/2 horse drill to turn the motor.

It took about 30 seconds to pump about 1/2 cup of gas.

I consider this a successful test and will using the pump hooked up to the modified manifold, not the cylinder cover.

Once I get it all together I'll let you know how it works.

 

[64osby]

Re: QD21 Fuel Pump #377927

Here is a couple pics of the Mikuni pump installed

Did a test run today and it work great at idle. Didn't test high RPM's because I need a prop.

 

[dkonrai]

Re: QD21 Fuel Pump #377927

when you did the bypass cover, did you simply replace the existing baffled cover with a flat / tapped one? or is the cover "stacked" over the old one?

 

[64osby]

Re: QD21 Fuel Pump #377927

dkonrai ^^^ The title on this says QD21 - Actual motor is a QD19 - the QD21 provided parts for this.

The QD19 used the manifold to pressurize the fuel tank. It had solid bypass covers, no holes for a fuel pump. So there was no need to cover, fill or block the outlet on the cover.

If you are going to use the manifold to provide the pulse to the fuel pump, the easiest thing is to find a solid bypass cover. If that's not an option others here have made a plate to go over the cover. When doing this most will also fill the void created so the block pressure will be consistent, use JB Weld or Marine Tex.

If you're going to use the bypass cover to provide the pulse, then there a couple options I have seen. One is to remove the cover, tap the hole and fit a proper sized nipple.

Others have made a plate and the nipple is attached. Then the void should be filled and the plate needs to seal to the cover, (gasket and sealant).

Hope this helps, kind of an old thread. I will be messing with another 10 hp that has been fixed up. Just need to figure out my plan for fuel. I'm also looking to convert an 18hp from 2 to 1 line fuel.