Suspected a problem with some used injectors I picked up and needed a way to test and clean them. Had just about everything I needed laying around in the garage so I put this test stand together. Ran some SeaFoam injector cleaner through them and back flushed the injectors using the stand. The 502 runs like a champ now, problem solved.

Figured I would share this with you guys since it was cheap, easy and effective. It pressurizes the fluid using an air compressor. I activate the injectors with a doorbell switch hooked to a 12v battery. I used a welder for some of the tasks because I picked one up earlier this year and I'm always looking for practice, but this project could be accomplished without one.

To get started, I dug an empty Coleman propane bottle out of the trash can and drilled holes in each end. On one end, I welded a 1/4" NPT internal thread fitting to the tank and screwed in an air hose fitting. On the other end, I welded a steel -8AN to 3/8" NPT 90 degree fitting. I screwed the 90 degree fitting into one end of an extra fuel rail I had sitting around and then plugged the other end of the fuel rail with a 3/8" NPT brass pipe plug. I tapped the bottom of the rail for a couple of bolts to attach it to a stand I put together with 3 pieces of angle iron I had in the scrap pile. I welded a couple of pieces of flat stock to the bottom of the angle iron to make the stand more stable and stuck some drawer cushions on the "legs" so the stand won't tear up tables when it gets moved around.

Picked up 4 jars with metal screw top lids from the "ethnic aisle" at the grocery store for about a $1.30 apiece. Dumped that horrible gravy that came in them down the drain and glued the lids to some 2" aluminum with Liquid Nails. Drilled 1/2" holes for the injectors to squirt through, and another hole between them to fasten the jar assembly to the fuel rail with some long machine screws and a nut. I used full length threads so I can use the tester/cleaner with standard length injectors as well as stubbies.

Picked up a momentary contact/doorbell switch ($4) from the hardware store and bottle of compressor oil that I needed. The oil came in a plastic bottle with measurements on the side and a flip up spout that allows me to mix up the cleaner in the right proportions and easily fill the propane tank though the air fitting.

Wired up the doorbell switch between a cigarette lighter plug and a partial injector harness I had in my junk box. The pink wires go to the center pin (positive) of the cigarette lighter plug.

To run the cleaner, install the injectors in the rail, fasten the jars, fill the tank with fluid, set the regulator on the compressor to 50 psi and attach the air hose to the air fitting. Plug the lighter plug into a 12v portable power supply/jump starter. Press the doorbell, and watch the injectors spray into the glass jars. They should fill equally with a uniform spray pattern. Install the injectors upside down, then run some fluid through them to backflush and clean out the baskets. You can test/clean them individually by not plugging the other injectors into the harness.

You could use wood for the stand and come up with a different pressure vessel with fittings to avoid welding if you don't have access to a welder. I didn't want the wood soaking up fluids and I had the tank and metal laying around, so this was the route I went.

The only thing I would add would be a low volume, cleanable fuel filter between the tank and the rail. I carefully flush the tank and rail before I put in injectors and make sure the fluid I'm using doesn't contain particles.

If you wanted to "take it up a notch" you could use graduated cylinders instead of jars, and you could swap out the doorbell switch for a microcontroller that could pulse the injectors for a specific number of milliseconds. I've got a Basic Stamp I'm planning to use to control a VNT turbo I picked up. It wouldn't be too hard to set it up to perform this task. You could take unknown injectors and figure out their flow ratings. You could also measure their output, observe spray patterns, and check their function (like opening and closing properly) at higher fuel pressures by adjusting the air pressure with the regulator.

This thing coupled with a microcontroller and I'm 7 of 10 steps to fuel injecting my lawn tractor.

 

I don't mess with injection myself, but I am highly impressed with the pictures, write up, explanation and everything.
That's a VERY slick setup. Welcome to TGO torqued !

Think this might be more of a 'fabrication' thing, vs a general engine thing though? Five7 could always move it for you if you want...

thumbs up!

 

Feel free to put this post wherever it belongs. I've learned a ton from the knowledgeable guys on this forum. Glad to contribute.

 

Had a guy mention he uses a tester/cleaner that has a "rattler" feature that switches the polarity every pulse. Says it sometimes brings dead injectors back to life. Wouldn't be that hard to do, especially if you added a microcontroller.

 

Shoot that sure would be nice to have. Thanks for the info on the system.