Deisel help wanted

I've got an MP Jet .040 diesel bought new a couple of months back, and I can't get it to keep running. It will start and run backwards briefly then just dies. I'm using fresh Model Technics D100 diesel fuel, and an APC 7X3 prop. Do any of you diesel boffins out there have any clues about the problem ?

Sounds like it might be over compressed and lean. Also try a prop at the larger end of the range i.e 8 x 4, these engines have very low rpm so need a good flywheel effect

Is the fuel fresh?

Is it new? Where did you buy it from?

Like Allan says Mel de-compress it slightly and richen it up slightly. Just like glow motors they can be quite finicky when new. They can be quite awkward in cold temperatures as well, when JB and I were team racing at winter meets I used to warm our motors with the car exhaust for the first start of the day.

It's almost a Mills .75, not allowed to be used in Salford MFC club starting competitions back in 1949.
try this
http://www.icare-rc.com/diesel.htm#MP_Jet .040 PB

Thanks for the help guys, I'll try reducing the compression and maby a bigger prop. I'll try and get hold of an 8X4. The fuel by the way was a new tin of MT D100.

Though this is unlikely, if it was a new tin and you broke the seal always check the level of fuel in the tin. If its low it means the seal was not perfect and the volatile ether content has partially evaporated. Something that can catch out the unwary

Having the compresion too high is not good at all for diesels. Starting up slobberingly rich and under compresed is fine. It will run in a burp.... burp... type manner and you can bring up the compresion from there. Keep it very rich if its new or not run in. If second hand treat as not run in

Enjoy!

I lived in Macclesfield for 25 years and was in PAW's works quite often with Gig, Tony and Paul Eifflaender.
They carried on with the diesels for many years, but today, as always, something newfangled (like LIPO) comes along and that era has gone except for the enthusiasts who are mostly at the nats etc..
Biggest break-through for PAW was to introduce a thrust bearing tucked in front of the the crank web.
The difference was a 40% power increase on the small engines.
These small engines run best on lots of castor oill, at least 30% and quite a lot of ether.
extra oil for the higher ratio of sliding parts to capacity
extra ether for the quick cooling of the higher surface area of the outside compared with bigger engines.
The bigger ones have twin ball races and much more paraffin because that is the true source of the power and duration of these comp engines.

BTW I've also got a new MP Jet .061 R/C which is ballraced and which has yet to be run.

The 061 looks like a very tidy little engine. And at a very good price too on the Icare website

Did you buy it from them? If so what did they charge for P & P ?

Sort of related question, but why are model diesel engines usually small little things? Why do we not see any 20 to 50cc diesel engines?

Andy

I flew my 10cc diesel Edge 540 w/e before last. Had several flights...

I answer to your question Andy - Dunno! The 10cc is very easy to operate. Perhaps a tad less easy than a 2-st glow as the compression cannot be finally set until its properly warmed up. It would be fairer to say its different to operate rather than harder or easier

One noticable point is that the engine can fire if turned over by hand, just like a glow with the plug energised, and catch out the unwary... Ask me how I know!

To answer your question Alan, I got both engines on Ebay from a trader by the name of Cosmic Flyer. As I recall I paid £75 for the Mills look alike and £80 for the 061.

Andy, one thing that might put you off a whopping great diesel is that I paid £12 for half a leter of fuel!

I think the issue with larger "diesel" engines is that the engineering becomes difficult to scale up, mainly the contra piston the device that allows the compression ratio to be manually varied. The engines are not true diesel engines but would be more correctly named "compression ignition" engines