.020 Pee Wee won't start (solved!)

thomaslowery Sat Jun 25, 2022 2:10 pm

(solution in the comments!)

A tale as old as the internal combustion engine itself, the bloody thing won't start!

So I've recently purchased my first ever model ice engine, a .020 Pee Wee. It looked used but clean and the price was right.

I took the whole thing apart, soaked everything in nitro fuel, cleaned it off and put it back together with brand new official cox;

- glow head and gasket
- crank case gasket
- fuel tank O ring
- reed and clip
- fuel tank tube and spring

I am using Optifuel's Optimix RTR 25 fuel (25% Nitro, 15% synthetic oil) mixed with pure castor oil at a ratio of 9:1
my glow head glows very bright (using a 1.5v D battery), and burbles away when in contact with the fuel
There seems to be good compression (but I have very little experience with such things), there is no bubbling between the glow head and cylinder or anything

Starting procedure I have been using;

- Brim the tank
- Turn tank needle all the way clockwise until it stops, then turn three full turns anti-clockwise (as a starting point)
- Inject a small quantity of fuel into the exhaust port, then turn the engine over a couple of times
- Attach the power clip to the glow head
- Wind the spring starter back one full rotation and release

Now, the very most I've gotten out of the engine is a short burst (about a second), which was actually the very first time I tried starting it (I don't know if that means anything, but it's a bit of a coincidence). A few more attempts after that I got one even shorter burst, and maybe a dozen attempts after that I got a couple of pops.

I have tried setting the fuel tank needle at different positions, one full turn in each direction in 1/4 turn increments from the starting position. I also tried winding the spring back further, as well as hand starting. I have tried injecting more and less fuel into the exhaust port. All with no luck.

Basically I am now out of ideas, is it possible to reassemble the engine incorrectly that wouldn't be obvious? could the fuel be the issue? Do I just have a dud engine? Or am I just making an obvious mistake I am missing?

The strangest part to me is that I'm not even getting any pops after priming, even if the fuel isn't being delivered properly by the needle valve etc, surely the initial priming fuel would ignite?

Any advice, ideas or feedback would be greatly appreciated!

Thanks in advance,

Tom

Marleysky Sat Jun 25, 2022 2:49 pm

Tom, from what you've done it should be a "like new" engine! Now it gets down to the small items on the checklist.
1-Is your fuel filtered before putting into tank?
2-Is the reed valve free to move under the retaining ring?
3-Is the retaining ring leg angled away from the reed?
4-Does the assembled tank/reed/clip pass the suck/blow test? Air sucks in, compression closes reed on seat.
5-SOP: Close NV, fill tank, open NV then try to start. Filling with NV open may flood engine or force dirt particles into clog fuel flow.
6-Get a good Orange glow on the glow head. Fresh battery(s) short wires, firm connection, for good glow. A Warm head is just draining the battery power.
7-May have too much oil mixed with fuel? Not sure what the 15% synthetic and a 9:1 ratio of castor equals out to. Try a prime of the RTR fuel without the castor to see if it'll give ya a short burst of running.

https://www.coxengineforum.com/t15340-does-old-fuel-work-because-my-new-49-with-spring-start-won-t-start

thomaslowery Sat Jun 25, 2022 3:34 pm

Marleysky wrote:Tom, from what you've done it should be a "like new" engine! Now it gets down to the small items on the checklist.
1-Is your fuel filtered before putting into tank?
2-Is the reed valve free to move under the retaining ring?
3-Is the retaining ring leg angled away from the reed?
4-Does the assembled tank/reed/clip pass the suck/blow test? Air sucks in, compression closes reed on seat.
5-SOP: Close NV, fill tank, open NV then try to start. Filling with NV open may flood engine or force dirt particles into clog fuel flow.
6-Get a good Orange glow on the glow head. Fresh battery(s) short wires, firm connection, for good glow. A Warm head is just draining the battery power.
7-May have too much oil mixed with fuel? Not sure what the 15% synthetic and a 9:1 ratio of castor equals out to. Try a prime of the RTR fuel without the castor to see if it'll give ya a short burst of running.

https://www.coxengineforum.com/t15340-does-old-fuel-work-because-my-new-49-with-spring-start-won-t-start

lets see,
1- No I have not filtered the fuel, as I assumed 'RTR' means that is not necessary? How should I go about filtering it if that is required?
2- I couldn't say for sure, I didn't think to check!
3- When you say angled away from the reed, what exactly do you mean by this?
4- Yes I tried blowing through the hole when I was reassembling it and it seemed to be functioning as a one way valve as it should.
5- Will keep this in mind!
6- Glow does appear to be good, and is doesn't get especially warm either.
7- Ok so cox say that the fuel must be at least 10% castor oil and 10% synthetic oil, so mixing the 15% synthetic oil nitro fuel at a ratio of 9:1 with the pure castor oil gives me mixture that is 10% castor (0.1*100) and 13.5% synthetic oil (0.9*15), 23.5% total. This doesn't sound as if it should be an issue, however I will try the straight RTR fuel and see what happens.

Thanks for the tips!

Ken Cook Sat Jun 25, 2022 5:16 pm

It sounds to me like it's not getting fuel . The leg that Marley references, isn't flat like the rest of the circlip, it's bent up slightly and the clip can be installed either way in the tank. The problem occurs when the clip is installed and leg is pinching down on the reed. The leg of the clip is to be installed with the leg away from the reed. Once installed, carefully take a X-acto and make certain the reed rotates under the circlip.

The backplate of the Cox Bee is made of crap material essentially pot metal which oxidizes. With the needle removed, carefully insert a small pin or wire down through the needle valve seat to insure it's not blocked with oxidation. Feed the wire back through the nipple into the needle valve seat and looking down the needle valve hole you can see the tip of the wire or pin.

Another thing you can do using a syringe is to pressurize the tank by placing a finger over the overflow and pressurizing the other side with fuel in the syringe as this will push fuel into the crankcase. This is a small engine and little fuel is needed to prime. The common mistake is that they get flooded. Just a little pressure, prime the cylinder and the engine should start quickly. I generally go with 3.5 turns of the needle which is usually rich but it stays running until i can adjust it.

706jim Sun Jun 26, 2022 1:04 am

"Close needle valve and open 2 1/2- 3 1/2 turns".

Possibly not the best advice despite it being in the manufacturer's instructions.

REALLY easy to break the tip of the needle valve off in the backplate by overtightening it and then you will be getting NO fuel.

thomaslowery Sun Jun 26, 2022 4:48 pm

Ken Cook wrote: It sounds to me like it's not getting fuel . The leg that Marley references, isn't flat like the rest of the circlip, it's bent up slightly and the clip can be installed either way in the tank. The problem occurs when the clip is installed and leg is pinching down on the reed. The leg of the clip is to be installed with the leg away from the reed. Once installed, carefully take a X-acto and make certain the reed rotates under the circlip.

The backplate of the Cox Bee is made of crap material essentially pot metal which oxidizes. With the needle removed, carefully insert a small pin or wire down through the needle valve seat to insure it's not blocked with oxidation. Feed the wire back through the nipple into the needle valve seat and looking down the needle valve hole you can see the tip of the wire or pin.

Another thing you can do using a syringe is to pressurize the tank by placing a finger over the overflow and pressurizing the other side with fuel in the syringe as this will push fuel into the crankcase. This is a small engine and little fuel is needed to prime. The common mistake is that they get flooded. Just a little pressure, prime the cylinder and the engine should start quickly. I generally go with 3.5 turns of the needle which is usually rich but it stays running until i can adjust it.

I think you were right about the needle! I used a pin to feel around and when I pulled it out the tip was covered with a brownish reddish sludge, so I wiped it off and repeated until it all seemed to be gone and then washed it out with some fuel. It was a bit reluctant to start, and initially I had to open the needle to almost 4 or 5 turns to get it to run. It was running a bit rough to begin with, but began to smooth out and run richer. I assume this was the last of the dirt and gunk going through the system. After about a minute it was running quite smooth and I had turned the needle back down to a more reasonable 2 or 3 turns.

The second run started much easier, and with a much more reasonable 3 turns on the needle. Once running it was very smooth and I leaned it out to about 2.5 or 2.25 turns where it seemed to be happiest.

Fingers crossed this is my issue solved, although I will probably still double check my reed valve at some point!

Thanks for your help, I greatly appreciate it!

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Manufacturer's instructions possibly not the best?

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