I have an old kit built, manual start, Wren 54. The engine worked perfectly but was removed from a model a couple of years ago and wasn't used again until recently.

I have refitted the engine in another model and am now having problems with the start. The engine appears to flame out on start (but doesn't stop completely as it is still running on the gas) and then it ramps again. After a couple of these cycles it gets up to idle and is then perfect. I have had about 20 flights like this and in the air it is perfect. It just struggles to get through the start.

It was suggested to me today that it might be a dodgy pump (Hausl 280). I can't see the old trick of running fuel through it for a couple of hours helping as it has now had a couple of hours run time in the air. Is there anything else I can do to help 'free up' the pump or is it likely to be shot. I'm a bit wary of spending £120 on a new pump for this old engine, especially if it turns out to be something else.

Has anyone seen a similar problem during start that goes away once the engine is running?

Darren

Because the pump start voltages are so low you can get this as the brushes are "clogged", at higher voltages it will over come this and have enough torque to turn the gears. Brushed pumps can die between a good run/flight as the brushes are constantly wearing. Approx how many hours on pump?

Dave

Cheers Dave, that sounds plausible.

The pump has about 40 run cycles on it and the ECU is showing about 9 hours but, being a FADEC, I'm guessing that the engine run time is quite a bit less than this. I wonder if being sat on my shelf for a couple of years hasn't helped[&o]

I assume that it's not possible to fit a new motor to the pump? I might have to relegate this one to smoke/fuel can use and try a new pump.

Sounds low hours, but I have seen pumps die at various hours, lots affect this, starting with a ball tap closed/blocked system, fuel with excess moisture leads to corrosion and tight gears. Not easy to change as the drive gear needs removing. Like you say you can use it for other uses.

Dw

I once tried to change the motor on a pump as its just a simple brushed motor but I found it impossible to get the mesh of the gears correct so I ended up having to buy a new complete pump

I just caught this!

First thing to check : If there is too much propane on the initial start cycle , the rpm and temp will build quiclky, which will fool the ECU and slow the first fuel ramp. Check also that the EGT probe is inserted in to the cone to feel temp rise correctly

Go into the start menu and check to see what the setting for pump start ( Auto +1 recommended) and ramp (006 to 008)

If you have the Fadec software, you can also go into the autostart menu and reduce the rpm at the first fuel ramp.

If it is an older version (MK2 ??) there may be a restrictor installed after the pump ( 3mm piping with a small brass -needle) if this is present, try removing it.

Just a couple of suggestions.


let me know how you get along!

Thanks Ron,

Propane level is fine, EGT is reading correctly, Pump Start is at Auto+3 but the engine converts from gas to kero quite easily, Pump ramp is at 007.

I should have mentioned that the engine is a Mk3.

The first part of the start is generally fine. The problems occur at about half way during the start and even after the starter motor has been disengaged. Once running it seems to be fine.

The engine was fine until it was removed from a model and left unused for a while. I'm wondering if something (the pump or something inside the engine) has become gunged up somewhere. It just seems a bit odd that the problems only happen during the start cycle and not even at the beginning of the start.

Last time out I sprayed a bit of lube into the pump motor can just in case but I only had one start due to the weather so need to try again when it has had time to soak in. I can get the engine running at the moment so can just about live with it. If it gets any worse then I'll have to take it to the Wren factory for them to have a look at.

If it is a full autostart, try manually turning on and off the propane (bypass the solenoid)...could be that the autostart parameter for the "start gas off" is occuring at to low of an rpm to get it up to ramp..