Help Understanding how this Setup solves air in the FI system of a 2-stroke engine
Help Understanding how this Setup solves air in the FI system of a 2-stroke engine
(OP)
Greetings,
We've been experiencing some problems with Fuel Injected 2-Stroke (3-cylinder) engines. Mainly starting the engines after the fuel lines have been purged or emptied (i.e. disassembly, shipping, fuel exhaustion.etc) The engines must be setup as shown in my sketch... They use a non-priming fuel pump.
After having the engine designers/mfg investigate the problems they confirmed our suspicion that air is being trapped in the FI system in the fuel rail. They said the air will not go out of the injector and is very difficult to get out. Their solution was shown in the top portion of the attached sketch and it does seem to be working.
I'm trying to understand what exactly this setup is doing and how it works in getting the air out of the lines. I'm thinking that on the return side of the jet there will be low pressure (lower pressure than the trapped air) and the air will find the path of least resistance --- and since the injectors are high pressure (higher than the air that is trapped) it will not expel through the injector.
Does this make sense? Once we understand it better we're thinking of buying or designing something a little simpler, more practical & aesthetically pleasing to do the same thing.
We are not the biggest fish in the sea with our engine vendor, who has more problems than time to solve them, so there was not a great effort to find a 100% fix. More of a "quick fix" if you will.
Any input understanding how this Setup solves air in the FI system of a 2-stroke engine will be greatly appreciated.
Thanks,
VS
We've been experiencing some problems with Fuel Injected 2-Stroke (3-cylinder) engines. Mainly starting the engines after the fuel lines have been purged or emptied (i.e. disassembly, shipping, fuel exhaustion.etc) The engines must be setup as shown in my sketch... They use a non-priming fuel pump.
After having the engine designers/mfg investigate the problems they confirmed our suspicion that air is being trapped in the FI system in the fuel rail. They said the air will not go out of the injector and is very difficult to get out. Their solution was shown in the top portion of the attached sketch and it does seem to be working.
I'm trying to understand what exactly this setup is doing and how it works in getting the air out of the lines. I'm thinking that on the return side of the jet there will be low pressure (lower pressure than the trapped air) and the air will find the path of least resistance --- and since the injectors are high pressure (higher than the air that is trapped) it will not expel through the injector.
Does this make sense? Once we understand it better we're thinking of buying or designing something a little simpler, more practical & aesthetically pleasing to do the same thing.
We are not the biggest fish in the sea with our engine vendor, who has more problems than time to solve them, so there was not a great effort to find a 100% fix. More of a "quick fix" if you will.
Any input understanding how this Setup solves air in the FI system of a 2-stroke engine will be greatly appreciated.
Thanks,
VS





RE: Help Understanding how this Setup solves air in the FI system of a 2-stroke engine
I would think it is going to hurt normal starting/restarting as the rail is always going to bleed down in pressure as soon as the engine stops.
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The Help for this program was created in Windows Help format, which depends on a feature that isn't included in this version of Windows.
RE: Help Understanding how this Setup solves air in the FI system of a 2-stroke engine
RE: Help Understanding how this Setup solves air in the FI system of a 2-stroke engine
So once the engine is running and the Pressure Regulator Diaphragm is working, allowing fuel to Bypass, would this not "purge" the system as you describe? Or is there something that will prevent the air from moving through the Pressure Regulator? -- Obviously air will not move through the Pressure Regulator or otherwise we wouldn't need this extra bypass.
RE: Help Understanding how this Setup solves air in the FI system of a 2-stroke engine
RE: Help Understanding how this Setup solves air in the FI system of a 2-stroke engine
Even better than that would be an air bleed from the very top of the fuel rail.
Mike Halloran
Pembroke Pines, FL, USA
RE: Help Understanding how this Setup solves air in the FI system of a 2-stroke engine
Instead of having the orifice, why not substitute it for an isolation valve?
You could then open the valve, fire up the fuel pump and purge the air from the rail back into the tank, then close the valve, prime the system and fire it up?
RE: Help Understanding how this Setup solves air in the FI system of a 2-stroke engine
If this is just a simple purge, I can find better ways to do it, such as Tuckabag's suggestion. Is everyones conclusion that this is just a crude purging system? I had the impression that there was something a bit more complex going on. Otherwise, I can understand why the air wouldn't purge through the pressure reg. We know there isn't a ton of air in the system otherwise it would not run.
No, the tee is facing down as shown in the sketch. All orientations are relatively accurate.
We've never had any injector problems because of this, they seem to be rather robust.
Thanks,
VS
RE: Help Understanding how this Setup solves air in the FI system of a 2-stroke engine
RE: Help Understanding how this Setup solves air in the FI system of a 2-stroke engine
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The Help for this program was created in Windows Help format, which depends on a feature that isn't included in this version of Windows.
RE: Help Understanding how this Setup solves air in the FI system of a 2-stroke engine
RE: Help Understanding how this Setup solves air in the FI system of a 2-stroke engine
RE: Help Understanding how this Setup solves air in the FI system of a 2-stroke engine
He got the answer he was looking for re what function the orifice performed.
RE: Help Understanding how this Setup solves air in the FI system of a 2-stroke engine
RE: Help Understanding how this Setup solves air in the FI system of a 2-stroke engine
The fuel pump is switched on first for about 5 seconds before the engine is started. It must warm up before it really starts running good anyway. And air will only get in the system following disassembly, shipping, fuel exhaustion or pro-longed storage.etc So it is not a major issue all the time.
I still do not understand how this system works. Why will air not purge through the regulator when the pump is turned on before starting? It produces the 3+ bar required to operate the regulator, as fuel comes out the return.
RE: Help Understanding how this Setup solves air in the FI system of a 2-stroke engine