RAM 500 NOTES

After going through a lot of problems with my RAM 500, I thought my experiences might help others. I found there are a lot of simple things you can do to maintain your engine.

My engine (SN 113) never ran right from the start and I had to send it for repairs after RAM went out of business. The fuel manifold was replaced and shims were added to bring it to factory specs. After the repair the engine was shipped to my son in Arlington, Tx. There it was successfully flown in two airplanes. The last 13 flights were in my new Boomerang Intro. It was then shipped to Denver where I live and I think it has achieved the “Run” condition only once since arriving in Denver in approx. 30 attempts.

Besides the run problems I also had a starter problem. Currently I have adapted the new larger bendix to the old mount. I had to make a spacer ring to space the starter motor back to accommodate the longer bendix. It motor still fits in the original motor cover.

I finally decided to disassemble the engine my self. First I started to remove the exhaust nozzle and found most of the screws to only be hand tight. There was a lot of black carbon area around the case where the nozzle mates to the case. It was obviously leaking a lot.

Next I pressed the motor assembly out of the case. There is a large “O” ring that seals the case to the diffuser assembly. This “O” ring was leaking approx 1/3 of its diameter. I found a Viton “O” ring that was a perfect fit. I reassembled the engine and it still would not run.

I became suspicious of my fuel pump so I hooked my engine to another fuel pump, ECU and battery that was working good with a different RAM 500 engine. I made three attempts and once it went to 51K RPM and then stopped suddenly with a lot of flame out the back. The other two attempts would not light the kero.

At this point I was suspicious that I had plugged fuel needles. I disassembled again and this time I removed the nut holding the compressor on and then the shaft with turbine wheel slid out the back of the engine. Next I was going to remove the NGV and discovered 3 of the 4 screws were only finger tight. The forth took a slight twist with the hex wrench to move it. I don’t see any damage from the screws being loose. After removing the screws it was now possible to slide the combustion chamber off the back of the assembly. Visual exam revealed a lot of carbon build up on the inside of the combustion chamber front plate. Testing showed that the inside dia. of the fuel needles is .020 dia. so a piece of music wire was used to test for clogged needles and two were completely closed off and 3-4 more were partially clogged. Next I hooked a PowerMax bottle to the fuel in line and using a shutoff value turned on a small about of gas and lit the needles I now have a good even length of flame from each needle.

Next I decided to do a fuel flow test through the needles. I used a hookup where I could hook one nicad cell directly to the fuel pump and could also hook two nicad cells in series to the pump. Using my pump and one nicad cell gave a very small fuel flow with the assembly held so that the needles were all at approx. a 45 degree angle from vertical. I did not see much fuel coming out of the needles but it did drip off each needle. Next I hooked up the two nicads in series to the pump and the needles sprayed fuel out the ends about 1” long. Next I tried the second pump and with one nicad cell the stream was 1/8” long and with two nicad cells it was about 2 to 2 ½” long. The difference between the two pumps is dramatic.

On the RAM 500 there are three small stainless tubes the go through the diffuser, one for fuel, one for starting gas and one for lube fuel to the bearings. A 1mm x 1mm “O” ring is compressed around each of these tubes when you tighten the fittings that hold the external tubes to the diffuser. The stainless tubes are a very loose fit in the “O” ring even when the fittings are fully tight. I added a second 1.5mm x 1.5mm “O” ring on top the exiting one. I used this setup when I did the fuel flow tests and did not have any leaking. My engine has been continually wet on the front side of the diffuser and I think those fittings have been leaking.

In summary I would check the tightness of the exhaust nozzle screws about every 10 flights (we found loose screws on 3 other engines) until they prove they will stay tight. If you have to remove the front cover for anything check to see that the front of the diffuser is dry. If not your fittings are probably leaking. After I have run my engine for awhile I will know if adding the 1.5mm “O” is a good solution.