Jump to content

Priming a dry fuel system


BMcCand - N248CT

Recommended Posts

I'm completing the 5yr Rotax service. I had drained all fuel, and the plane was dry for about 10 days.

Yes, I'm slow... but careful. Upon re-assembly and re-fueling with 10 gal, I tried to drain at the

gascolator and got a small dribble. Checked hoses for kinking, fuel valve operation, all Ok.

I finally had to 'prime' the fuel system. I taped off one wing cap vent, then applied shop

air to the other vent. I did it loosely with a cupped hand and the air nozzle.

I have the metal fuel filter and the metal pipe for the tight bend under the panel.

After priming, the fuel flow out of the gascolator was normal. No particles found in the

gascolator screen.

 

Has anyone else seen this problem?

Link to comment
Share on other sites

You guys should never have to prime anything. I have drained more tanks and pulled more engines than I can count. I pour the fuel in, open the fuel shutoff and if you want let a dribble come out the gascolator, but every engine will fire over in a second or two . I have never once had any issue on starting. As soon as you crank the engine the pump will do its job.

You do not need to get a flow of fuel out the gascolator for it to start.

Link to comment
Share on other sites

I wanted to avoid an extended cranking period, so wanted good fuel first.Its about 40 deg up here, and I had not pre-heated since I just put the oil backand purged the system. Starting up here in Hillsboro can take a littlelonger than in Tucson.. even in normal fuel conditions.Happy Holidays Roger !

 

Link to comment
Share on other sites

You guys should never have to prime anything. I have drained more tanks and pulled more engines than I can count. I pour the fuel in, open the fuel shutoff and if you want let a dribble come out the gascolator, but every engine will fire over in a second or two . I have never once had any issue on starting. As soon as you crank the engine the pump will do its job.

You do not need to get a flow of fuel out the gascolator for it to start.

 

Excellent point. Phase lock in the fuel line is not uncommon and I have dealt with it a few times and spent >1 hour to "unlock" it.

 

Next time I will be smarter thanks to Roger!

Link to comment
Share on other sites

I forgot to mention the carb bowls were totally dry, too. Those Transitional Bushings, the aluminum ring to adapt the SEET hose

to the carb air intake are a pain to remove. I had both carbs off and drained so I could hold them down on a workbench

while using large channel-locks to remove those adapters. How do other people do that ?

 

I considered machining a notch to clear the banjo bolts, but unscrewing the adapter seemed better.

I cleaned up the edges where the channel-locks bit into the aluminum.

 

For starting, my first crank 10sec on ; 2 min wait didn't start. Second crank did.

 

No fluid leaks after first start, so things are going well. I have yet to lean on the rockers to

make sure there is no air in the lifters.

Link to comment
Share on other sites

Hi Bill,

 

Why did you take the aluminum adapters off the carbs?

There isn't a reason I can think of that a CT would need to pull those off. You just change the CEET tubing.

After you re-fill the wings with fuel open the fuel shut off and then open the gascolator until you get a tiny flow. When I do a hose change the wings, fuel lines, gascolator and carb bowls are always drained.

Link to comment
Share on other sites

Hi Bill,

 

If you are talking about the red cross over fuel tube that supplies the carbs fuel that is an on condition hose only and doesn't need the 5 year change. The nuts that secure this or the stainless steel lines will unscrew without removing those rings.. In all the carbs I have ever worked on I have never had to remove that ring. There isn't a lot of clearance for sure, but I have never had one I couldn't get to with w wrench.

Link to comment
Share on other sites

Hi Bill,

 

If you are talking about the red cross over fuel tube that supplies the carbs fuel that is an on condition hose only and doesn't need the 5 year change. The nuts that secure this or the stainless steel lines will unscrew without removing those rings.. In all the carbs I have ever worked on I have never had to remove that ring. There isn't a lot of clearance for sure, but I have never had one I couldn't get to with w wrench.

 

Roger, where does Rotax say this? I've heard this mentioned before and ask about it with no responce. Tom

Link to comment
Share on other sites

I interpreted the 5 year paragraph 2.1 in the Line Maint. manual as requiring

all fuel lines to be replaced, and I have the red rubber coated one.

I m using Edition 2/ Rev 1, dated Jul 1 2010. Pg 05-10-00 pg 8.

So, I bought that hose plus the copper crush washers and replaced the line.

 

I also replaced the fuel pump with integral hoses ,but then had to

change the hose to the gascolator anyway. Have yet to route the

drain hose and firesleeve. I think I'll go under the cylinders, above

the pushrod pipes, back to the firewall and down.

 

Maybe I spent too much... and maybe I'm too literal at reading manuals.

I'm also going to an FD service center to do the engine pull and mounts

replacement, per manual.

 

Apparently I didn't try hard enough to remove the bolt and banjo w/o removing

that darned aluminum ring. I think the torque can be measured with an open-end

wrench and a spring scale in lieu of socket and usual torque wrench.

Next time (when I have new washers) I'll try again.

Link to comment
Share on other sites

When I remove those banjo bolts I first take off the starting carb. Then you can get a wrench in there. When going back together I use a crows foot to torque. I read the manual the same as you that the fuel hose needs to be replaced. I think there would need to be some sort of written documentation saying that it doesn't need to be replaced. It is somethint I will ask about at Sebring. Tom

Link to comment
Share on other sites

Hi Guys,

 

I have heard back from Rotax. First I want to say I have heard two versions of this from different distributors. One says change it the other on condition only, but here is the final word. The red Teflon hose that comes off at the fuel assembly block on top of the carb cross over tube does in fact need to be replaced at the 5 year hose change. The price on this hose assembly is $338.

 

 

I will post in the next few days a fuel hose video from a 6.5 year old Rotax fuel hose I think you will find very interesting.

Link to comment
Share on other sites

Here you go for the document.

It is in the Line Maint manual. It is the third item down under all rubber hoses and says it includes "all Teflon hoses". Those two red fuel supply hoses that feed both carbs are the Teflon hoses. The CT's from 2006 usually have the stainless steel lines, but the 2007 CT's and up had the Teflon hoses installed. I don't know the exact time they were changed.

Teflon hose change.pdf

Link to comment
Share on other sites

Thanks Roger and Tom for the research and feedback. I didn't cut open the red hose to see if was Teflon !

I did buy a new one for my CTSW, it is serial 06-12-15, so the new hoses started in late 2006.

 

Also thanks for the advice about removing the choke valve assembly to get at the fuel banjo bolt.

I love what I can learn here.

Happy 2012

Link to comment
Share on other sites

Archived

This topic is now archived and is closed to further replies.

×
×
  • Create New...