This seems to be a more common problem and one i had not been aware of before my own experience with it. Mine may also be a little different but could be the same. The problem for me is the pump. An intermittant problem where after i did a line purge test to see why my engine wouldnt start. At first no fuel, then as i raised the test voltage it would "pop". Then work perfectly all the way down to very low voltage. And start and restart at low voltage. Then put it all back and no go. Repeat the routine and raise the voltage and it would work again. These are multi commutator motors, and it seems that not all commutators work, with a little friction setting in with the interval of time. Just recieved a new pump so will test it out tonight. Interesting to see this problem expressed by so many persons at one time.

I don't think these motors where ever designed to run on 0.2volts, I think they where designed to run on 6volts, perhaps a software upgrade to kick start the motor and then reduce the voltage is required, just a thought.

Mike

Sure thats not already the case ? I _think_ that when starting, you hear a very short burst of the pump, like it has a much higher voltage for a very short amount of time ?
I might be wrong though...

Fuel valves are mechanical device operated by a solenoid coil when energize, it's a simple magnetism with moving core provided as an actuator called plunger, so everytime it's energize it produce a clicking sound. If I'm not mistaken there's shouldn't be a clicking sound if there's no movement or opening of valve. If the coil is energized and the plunger is stuck the sound is not noticeable. As far as the attempts to start your engine, the periodic repetition of on-and-off signal should brake-in your valve immediately. Although these valves require small amount of current but these are strong more than enough to pull the plunger. I've seen some solenoid valves failed due to long years of harsh operation but most of them stuck due to burned coil not the valve itself but those are for high voltage application. Your test also shown that there's no obstruction in the valve and fuel line as there's enough flow rate at the end of disconnected line. The only thing that you didn't test due to no access was from the inlet of starting gas to the burner...

Interesting...

Based on your test run or diagnostic, the results are good. Since you slightly increase pump voltage and it works fine, then it's the pump or pump voltage. However, if you notice excessive flames coming out from the exhaust, then it was a brake-in of your pump motor as per airkiller and others mentioned. If after few completed starting, then might be at the burner if any. If for a long period of time there's no excessive flames or no high temp start then it could be fuel line flow resistance.

Sometimes issue on electrical characteristic of pump motor like resistance of coil could affect it, but because these motor are built and design in standard specific for that voltage range and rpm, therefore we can disregard it. But instead, I guess although this motor has a little amount of lube prior to packaging but variation in storage temps and lenght of time could sometimes affect it. So I believe as per indubitably posted resistance of brushes to commutator and the bushing could affect the first loaded running with very low voltage.

After re-reading the manuals .....

Jetcat kero versions during the start sequence are useing the Old propane valve
in line with the kero/burner igniter unit to
pulse inject the fuel in order to widen the "stoich point" for ignition. (dripping fuel not a stream)

After ignition it just slowly increases the fuel flow to get to idle.
Hence all that solenoid clicking on start.

On the propane versions, there was an ECU setting to increase the propane flow (solenoid clicking)
if you wanted more flow you adjusted the ecu setting for propane.... less clicking, more flow.
If you wanted less flow the valve opened and closed faster...hence even more clicking.

It seems there are two things regulating fuel flow to the burner/igniter....not just pump voltage.

So has anybody tried adjusting the old propane ecu solenoid settings which is now the ...
"new kero/burner solenoid"setting... increasing
the fuel flow to the burner...decreasing the resistance.........without upping the pump voltage?

(I did'nt know they were shipping with "newer batteries" but ... I have to admit the weak battery theory is toast..)

Upping the pump voltage would overcome a "restrictive ecu setting" on the "old propane valve"
now being used as the kero burner igniter valve....assuming no other restrictions are downstream.
This would also explain why upping the pump voltage is working to overcome the valve
resistance with greater pump pressure.

This was great learning....

This is a very interesting thread, as I have recently bought a S/H JC 120se, I had to buy a new pump as one of the terminal was broken on the original, and whilst installing the turbine I have converted it to Kero start, so some good pointers here as to when I run my engine, I'll certainly give the new pump a run-in.

Mark, be interested to find out your findings, whether you have found the cause, and/or cured the problem.

Vince.

Vinceyboy

Somewhere on the JetCat Forum I posted a thread on how to repair a JetCat pump with a broken terminal, have a look your busted one may be salvageable.

Mike

Hi Mike, thanks for that, have already sent it back to Mark V. for repair as it came from him and he said he'd repair it for me but I'll download the article for future reference.

Many thanks,

Vince.

Ok, after further tests here's an update.

Increasing the pump voltage is not the answer here now. That just led to fuel 'flowing' rather than dripping from the kero start line. Putting the voltage back to 0.2v returned the feed to a nice drip-drip-drip state.

I reconnected the line and it took 7 attempts before the engine started.

I think this now definitely proves there is an obstruction between the front mounted 3mm festo fitting and the kerostart plug? I need to get hold of a syringe to try and suck on the line but is there anything else a little more drastic I can check (ie take front of turbine off etc) without invalidating the warranty?

I really don't want to be sending it back right now as I'm starting to love this plane and want to fly it regularly through the summer....

Cheers
Mark

Hi Mark, I do have a syringe that I used to use to to inject cleaning fluid into my old printer, you are welcome to borrow it and give it a try, or you need to give the tube a good strong suck chap

I should also add that after the 7 start attempts last night, when it did finally start, there was no wet start scenario. In fact the start only just occurred on what must have been a tiny amount of fuel that had finally got through.

What's the best email address for an answer from JetCat??

Cheers
Mark

PS Might take you up on that Vince. Thanks

Mark have sent you message via what's app.
Read carefully.
Regards Mark Hinton. Ps Jetcat on holiday untill Monday.

Mark,
I use Udo Töpfer, he is very quick to answer, his email is at the front of their website (it requires ofcourse he is not on vacation )

I know this is several months old but I know how frustrating it is to find a thread that you think will solve your issue only to find it trails off with no answer!!

So, just a quick update. JetCat confirmed that my supposition of there being an internal blockage was correct. They suggested I apply 120-150PSI to the 3mm festo line and 'blow out' any blockage. Gave it a go and nothing obvious happened - just took compressor up to about 140PSI.

Tried a start and it started instantly. Never an issue since.

So there you go [8D]

Cheers,
Mark

Nice Mark [8D]

Mark... you had us like the guy waiting for the other shoe to drop !!!!!!!
Thanks for posting the end of the movie

Jack

Hi all
I just was going over all discussions just to get more info about jetcats and I have a small problem I hope u can help me with ……….

My p80 that I have for a 1 year’s already
I tried to run it and its propene start so when the sequence start after the ignition and engine go to 5000 rpm there is a fire in the Combustion chamber the engine dos not spoall up and I think it’s the fuel dos not go to the engine so I take the fuel bomb out and tray it its work only when the volte go’s 0.600 and up but lees than that it’s not working when u tray to test it from GSU ….. Is that normal or it should work from a lower voltage

Thanks in advance

Good Mark... Actually as per your diagnostic, it indicates that the system was working fine except at the burner side. “Your test also shown that there's no obstruction in the valve and fuel line as there's enough flow rate at the end of disconnected line.” If I’m not mistaken feeder inlet of starting fuel to the burner was the only thing you didn’t check. Now it's clear, thanks for feedback.

How long was the last time you run your engine? To answer your question at lower voltage less than 0.6V, yes, it should work with very low rpm. Did you got over temp alarm on your engine? Prior to that did you see preheating then followed by acceleration on your screen?

last time engine run was alomst 8 mintes.

and i didnt get over temp alarm. and no for the preheating

thanks

SAM

Ok Sam, considering your engine was run recently I can eliminate the possibility that your pump was slightly stuck. You mentioned on your test that it wasn't working below 0.6V, is the line disconnected?

About the sequence process, what are the readings shown on your GSU? Did you got acceleration delay? If you got no over temp alarm and the pump won't kick in, you have to check parameter setpoint like temp and rpm required to start the pump on. Also the computer will display the reason for shutdown, did you got time out?

yah i get acceleration delay

also its just run with propan only no fuel go to the engine

So it means that the pump is on and required to feed fuel. You can verify that also at pump running indicator. Usually runs at low rpm just to warm up this fuel and after that you should get increase in rpm. If you didn't see any flow in your fuel line and it works when you disconnect it, it mean you might have an internal blockage also otherwise it's on the pump side...