TSIO360-MB fuel re-circulation to tank and hot starts

[231MJ]

I started a previous discussion about trouble I was having with hot starts.  I got good advice and have had less trouble recently.

In that thread it was suggested that using the high boost pump to fill the fuel lines will not flood the engine because the fuel is recirculated back to the fuel tank...but that's not how my set-up works.  Here's what I'm seeing:

1. With the fuel lines empty (hot start conditions) and at idle-cutoff, it takes about 15 seconds to fill the lines with high boost
2. After 15 seconds of high boost and still at idle-cutoff,  fuel begins to run out the drain lines (its a healthy stream)
3. Adjusting the idle-cutoff in by about 1/4 to 1/2" does not stop the fuel from running out the drain
4. My engine is the MB version.  The fuel pump has been rebuilt twice under my ownership (17 years)

So what's going on here?  I'm trying to understand how the system is working so I don't start messing up the hot-starts.

 

Thanks

[kortopates]

[mention=12096]231MJ[/mention] It was the case with the original TCM pumps that with the mixture at ICO and the aux fuel pump engaged that no fuel was allowed exit the outlet port to the servo and was instead sent back to the tank. But in the latest generation of pumps with newer model numbers, a galley hole was added that does allow fuel to go to the servo with the mixture at ICO. So most likely, one of your pump rebuilds includes a model change to TCM latest configuration and therefore that's why yours will allow fuel to go to the servo and on to the cylinders.

That said, for priming purposes, its safest to use the priming circuit that pumps fuel into the induction system tubes. This eliminates the risk of a fire from over priming with fuel dripping out. The priming circuit was only added to meet Mooney's cold temp starting requirements (which were over stated) which is why you won't find them on the later IO-550's and TSIO-550's since it added significant cost. But pilots love the high boost option for priming because it pumps fuel directly into the cylinders for an easy start, as long as it not over done. So be careful. I prefer the priming circuit and the waiting for 30 seconds before engaging the starter. 

 

Edited September 27, 2017 by kortopates

[Jim F]

That's a big motor TSIO-5550. I bet it hauls ass. Can I get the STC number. Lol

[kortopates]

That's a big motor TSIO-5550. I bet it hauls ass. Can I get the STC number. Lol

LOL's, Thanks Jim, I corrected the typo.


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[231MJ]

Thank you, Paul.  Your insight is always helpful.

One of these days I want to talk to you about flying to Mexico.  It's on my bucket list.

 

August