So Your Gas Car Does Not Want To Start
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Having been involved in the RC Gas car scene for many years you soon grow accustomed to RC engines that just sound like they are talking to you when there is something wrong with them.
From repairing brakes, to repalcing bearings and rebuilding gear boxes, engine tuning is another important element.
One of those issues which is also common basically every day is an RC nitro engine that refuses to start.
An engine that starts today does not necessarily always mean it will start tomorrow, even though everything may be running like a tight ship.
When this happens it usually means atmospheric conditions are not the same as the day before and your mixtures will more than likely need some adjusting.
Outside of an engine not running well from atmospheric conditions, there could be a multitude of reasons of why a nitro engine will just not start.
One of those reasons that most do not understand has a lot to do with fuel pressure. I have to go out on a limb and be honest here and I have always said this in the past but most people who contemplate getting into the RC Car scene, immediately want to just straight into the Nitro powered gas car scene.
Yes, I get it, it is exciting hearing something rev, make sound, fry tires and go like the real thing but just like the real thing, if you do not have any mechanical aptitude and especially with engines, you will be in for one serious and time consuming learning curve as hobby shops just continue to rob you of your money while you continue to blow up engines because of the lack of knowledge or understanding of how they work.
They may be small engines but they are still real engines. They run on the concept of fuel and air mixtures and if you get this wrong, the motor either does not perform or it over performs and you blow it up.
One Common Problem Is Lack Of Fuel Pressure
Why Fuel Pressure Matters
When it comes to air fue ratios being set correctly, fuel pressure matters.
You could set your mixtures to a setting designed for your engine to run for the day but the minute there is an air leak, you are suddenly running leaner.
Gas car engines do not have fuel pumps. Because of this, the only fuel pressure they can develop is through fuel tank pressure which is provided by exhaust pressure.
That explains the little hose that goes from your exhaust pipe straight to your fuel tank.
When tuning any gas car, if there is a leak here, the tune will be much more challenging as the only source of fuel delivery left is for the engine to start and try and draw any fuel through the carburettor is with the aid of crank case vacuum.
This ultimately involves far richer running mixtures as you try to compensate for the lack of fuel pressure.
Checks To Be Done Before Any Tuning
Before you can tune any gas car engine, it must first be established that there are no fuel leaks, either by way of the carburetor, exhaust, fuel tanks or any crankcase leaks. These will all affect your tuning of your engine. The car presented here came in on tuning issues, and there were a couple. On first inspection, I discovered the exhaust was not even connected. That is an immediate fail for tuning with no exhaust pressure at all.
Second fault that I discovered was that the hose pressure line which goes to the exhaust was not connected either. Take these two out of the equation and you have serious tuning issues. Upon connecting these features, we then proceeded to tune the carby as we could not find other leaks anywhere.
Third issue was when I finally sorted the mixtures and got the engine running, as soon as I would touch the throttle the motor would just cut out. This is because of a weak glow plug on its way out. I replaced the glow plug and fixed all that as well.
We reset all the screws back to 0 and started again. Being no surprise at all we discovered the needles severely set to rich mixtures. As you can see from the video here, we got it running just nicely. Nitro engines that have healthy compression can always run well at low RPM.
I did run into other issues while trying to tune this. I also discovered it was only operating at half throttle due not no spacer to take up slack at the throttle end of the linkage and the drive shaft yoke fell off shortly after the unit was started.
The own had changed second gear a while ago and did not tighten the grub screw properly. Just because of this, the whole top chassis had to be removed together with the fuel tank just to get to the gear box.
Upon lifting the gearbox out, the shaft yoke just fell off. I put it back on, tightened the grub screw and got it running again. If you own a gas car and are experiencing issues with tuning, you must first establish if you have leaks anywhere on the fuel tank, exhaust pipe or engine. If these are intact, only then will your tunning efforts make a difference.
If on the other hand you are having problems you do not seem to be able to correct any tuning issues, please feel free to reach out on the number below for some tuning help.