CD-155 Engine Startup

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mrusk
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CD-155 Engine Startup

Post by mrusk »

Hello all,

we have some startup issues with the CD-155 engines in two of our DA40 especially (but not only) in cold weather. The engines do not ignite easily, sometimes it takes 15 seconds, sometimes it does not start at all even on second attempt. One of the engines has some single ignitions, the other one none at all until it finally starts (or doesn't...).

Interestingly with ground power attached there is no problem - it seems that a bit more voltage is helpful but the batteries are fine.
Anybody any ideas?

Regards,
Martin
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Colin
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Re: CD-155 Engine Startup

Post by Colin »

Martin, in very cold weather I have done two cycles of the glow plug, on the advice of the ferry pilot who dropped off my DA42.
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Re: CD-155 Engine Startup

Post by Karl »

Check the fuel hoses from the bulkhead to the Engine driven fuel pump. Inspect the cone inside the open end of hose for small cracks.

We had a similar issue where small cracks in the cone opened up when the union was tightened, the fuel pressure is negative during operation due to the fuel pump sucking the fuel through the pipe so no fuel leak is visible.
Once the engine is shut down air leaking into the pipe allows the fuel to return to the tank by gravity leaving the pipe empty. It then takes 2 or 3 cranking attempts to suck the fuel back up from the tank. Replacement of the pipe resolved the issue.

It's important to fix this ASAP as the HP fuel pump relies on the fuel as a lubricant which is why engineering should always prime the fuel line after maintenance and before the engine run.

Using external power probably means you can crank the engine faster and therefore prime the fuel line faster than on internal battery.
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mrusk
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Re: CD-155 Engine Startup

Post by mrusk »

Colin, I did try two glow cycles on my last attempt without success. After some failures we believe it might be better to invest the battery power into the starter.
Karl, thanks, I will discuss with our mechanics. As far as I understood they examined the fuel system already but I will check.
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Re: CD-155 Engine Startup

Post by Karl »

mrusk wrote: Thu Dec 30, 2021 9:28 pm Colin, I did try two glow cycles on my last attempt without success. After some failures we believe it might be better to invest the battery power into the starter.
Karl, thanks, I will discuss with our mechanics. As far as I understood they examined the fuel system already but I will check.
We have had it twice, probably caused by overtightening of the hose.

The cracks are tiny and difficult to see only opening up after the hose is fitted.

Remove the hose and look inside the open end, looking for any small cracks in the cone face.
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Re: CD-155 Engine Startup

Post by Colin »

Times that it has been cold ("wicked" cold here near Boston), or times that I have let the plane sit too long (six weeks was the longest), I have heeded my mechanics advice and pulled the "GEAR" breaker before tuning on the master. That meant that the pressure pump didn't rob the battery of a bunch of power right before I was trying to get the glow and spin the engines. Once I have one engine started then I turn on the avionics and push in the GEAR breaker.
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Re: CD-155 Engine Startup

Post by mrusk »

Karl wrote: Fri Dec 31, 2021 12:23 am We have had it twice, probably caused by overtightening of the hose.
The cracks are tiny and difficult to see only opening up after the hose is fitted.
Remove the hose and look inside the open end, looking for any small cracks in the cone face.
Some update on this:
We had the hoses checked and in one plane there was indeed a small crack in one hose. Engine starts now as it should.
Thanks for the tip, it really helped!!!
The other plane had a weak battery. It was exchanged and we hope that solves it for now.

Best Regards
Martin
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Re: CD-155 Engine Startup

Post by Karl »

Excellent, thanks for the feedback Martin.

Glad I could help.
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Re: CD-155 Engine Startup

Post by mrusk »

For the record - I just got some photos from the workshop.
WhatsApp Image 2022-02-23 at 20.54.05.jpeg
WhatsApp Image 2022-02-23 at 20.55.05.jpeg
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Re: CD-155 Engine Startup

Post by da50speed »

mrusk wrote: Wed Feb 23, 2022 9:29 pm For the record - I just got some photos from the workshop. WhatsApp Image 2022-02-23 at 20.54.05.jpegWhatsApp Image 2022-02-23 at 20.55.05.jpeg
Those tiny TINY defects prevent an engine from starting? Holy cow, that is temperamental!
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