RV-3 - rotec tbi issue - O320

[tectweaker]

I am trying to diagnose a problem on a rv3 where a Rotec tbi was installed recently.

The engine stumbles and hesitates when it is cold around 1600 rpm; crossing 1600 rpm pretty mugh stalls the engine.

Once the engine heats up and oil temp is up after few minutes; the engine starts running better and the hesitation reduces and we are able to cross 1600 rpm and we are able to make full power.

The issue does not seem to happen in the air.

The rotec tbi was verified working by the rotec guys. This engine sat for few years and being flown much more regularly recently. It used to have PS5 carb before.

Any pointers on what to adjust or look for would be great.

[Christopher Murphy]

No accel pump?

How fast are you shoving the power up?

Cm

[Christopher Murphy]

No accel pump?

How fast are you shoving the power up?

Cm

[hohocc]

There are a couple of good Rotec tbi threads in the traditional aircraft engine section, would this question get better coverage there?
Sorry I'm unable to offer any troubleshooting advice other than that!

[Dragonfly]

I presume you changed your fuel pump from high pressure to low pressure?

[pitts flyer]

There are a couple things to check:

1. Make sure you have no water in the fuel. If it gets into the regulator you can have problems like you describe. You may have to flush or disassemble the regulator to get any water out.

2. Make sure there is no fuel in the little tube between the TBI and regular. If there is any fuel in that line, your diaphragm in the regulator needs to be fixed/replaced, as it is leaking slightly. This will also cause the same issues.

Also, it is not uncommon to have to adjust the idle mixture between summer and winter a little. This for both the Ellison and Rotec. However, I leave mine adjusted for the summer, and warm engine temps. And just live the the fact that it doesn't idle to well when cold. In cold weather, I just to keep the RPM up around 100-1200 until the engine warms up. However from what you describe this is not your problem at the moment.

I have had both the above problems, the first with an Ellison and the second with the Rotec TBI. I really like them and fly with them on my Pitts, but they do have a couple of idiosyncrasies.

[tectweaker]

Thanks for the tips.

Will check the line for fuel.

Currently also looking at the spray bar and potentially drilling holes in it.

There is no accel pump and throttle movement is pretty gradual and smooth.

Also; fuel pump pressure has been changed.

[pitts flyer]

I would suggest not drilling any holes in the spray bar unless you talk to Rotec. I run a stock Rotec TBI on my Pitts. It has an O-320 with 10:1 pistons. Runs very smooth and makes great power with that Rotec.

Another thought I had is to check your fuel screens, including the one in the TBI. If any junk clogs them, this could also cause fuel starvation at higher throttle settings. A good fuel filter is needed with these TBIs because of the small orifices in the spraybar.

Good luck. Hope to hear about your results and what you ultimately find.

[RetiredRacer]

Do not drill any holes at this point. Pitts other suggestions are also good. The fact that it improves when heat soak settles in suggests that it may be a little lean at that rpm. How are the EGT's at various rpm's? As the throttle slide travels along the spray bar it gets to a point where multiple rows of holes start to discharge fuel, that 1600 rpm could be just before those extra holes?? but your EGT's should show an indication if that is the case. Do you have data you can down load?