BMcCand - N248CT Posted January 2, 2012 Report Share Posted January 2, 2012 I've replaced the fuel pump with the new 893-114 type, which has a drain fitting. Where are people routing the drain hose? I've considered straight down to behind the radiator & oil cooler. However, I can envision fuel spewing backward over a hot engine and causing a fire. I think fire sleeve is required. Another route is under the 1 & 3 cylinders on the right, and back to the large engine frame. So, what have people done? Is there an LOA for this, is LOA required ? I think no LOA since FD says follow Rotax, and Rotax says replace the pump at 5 yr if it has integral hoses. Thanks, Bill Mc. Link to comment Share on other sites More sharing options...
Roger Lee Posted January 2, 2012 Report Share Posted January 2, 2012 Hi Bill, No LOA is required since Rotax doesn't even sell the old pump any more. This is the only pump you can buy now. No fire sleeve should be required for a drain hose. You can route it any way you want, but should be away from hot spots like the exhaust tube and then down to the bottom of the cowl. One route: Back up along the coolant hoses under cyl. 3&4 to the engine mount then down to the bottom of the cowl. Do not place it out in the air stream. Use wire ties to hold it in place along its route and don't tighten them to the point of pinching off the tubing. Take the plane out and test run it up to 5000 rpm and check the fuel pressure, it should be 5.8 psi max or below. If it is more than that send it back under warranty and get another one. They had some that produced to much pressure in the beginning and there could be a few still out there. Link to comment Share on other sites More sharing options...
BMcCand - N248CT Posted January 2, 2012 Author Report Share Posted January 2, 2012 Thanks, Roger. I'll route that tube today, do a carb balance, and then sign off the logs. 5yr is almost done. Now to get in queue for chute repack. I have a spreadsheet for dates. There are reasons I wish I had a D120.... like now with a new pump. I could add a temporary analog gauge. I did that once at Corning while debugging a rough engine problem. That was ultimately carb contamination from flaky floats. Again, having a D120 with separate EGT would have been nice while understanding the rough engine in flight. Is it $2400 +installation of nice .... hard call. But knowing things that may cause damage to an $18,000 engine is also good. I did get the CPS special price on the pump that Jeremy noted. So the new folks (Kevin) are helpful. Link to comment Share on other sites More sharing options...
Darryl Posted January 29, 2012 Report Share Posted January 29, 2012 I have a CTLS and I followed the Rotax recommendation to install a new fuel pump. To make a long story short it was a mini fiasco. It took four tries by two competent shops - one near Seattle the other in Las Vegas - names omitted. Finally, after a couple of months, I have a new fuel pump. But now I am getting a "High Fuel Pressure" alarm on my Dynon EMS. This occurs when I throttle back for descent and at low idle speeds after landing. When the alarm set off, the readout on my Dynon EMS was 6.0 psi. The mechanic who installed it said to recalibrate my Dynon EMS so that it won't set of the high fuel pressure alarm. This sounds a little dicey. Any ideas? Link to comment Share on other sites More sharing options...
Jim Posted January 29, 2012 Report Share Posted January 29, 2012 I have a CTLS and I followed the Rotax recommendation to install a new fuel pump. To make a long story short it was a mini fiasco. It took four tries by two competent shops - one near Seattle the other in Las Vegas - names omitted. Finally, after a couple of months, I have a new fuel pump. But now I am getting a "High Fuel Pressure" alarm on my Dynon EMS. This occurs when I throttle back for descent and at low idle speeds after landing. When the alarm set off, the readout on my Dynon EMS was 6.0 psi. The mechanic who installed it said to recalibrate my Dynon EMS so that it won't set of the high fuel pressure alarm. This sounds a little dicey. Any ideas? I was talking to my friend with a StingSport this afternoon and he had exactly the same thing happen. His would go up to 6.2 psi and alarm. On final. He had the mechanic put the old pump back on and return the new one. Link to comment Share on other sites More sharing options...
marty.santic Posted January 30, 2012 Report Share Posted January 30, 2012 I was talking to my friend with a StingSport this afternoon and he had exactly the same thing happen. His would go up to 6.2 psi and alarm. On final. He had the mechanic put the old pump back on and return the new one. I and two friends have also replaced the fuel pump on the Rotax 912 in the RV-12. After the initial installation, all of us noticed higher than expected fuel pressures near 6 psig. After a few hours, (call it a break-in period). all of our pressures are now near 4.5 psig. A datapoint. Link to comment Share on other sites More sharing options...
Roger Lee Posted January 30, 2012 Report Share Posted January 30, 2012 I was wondering about all the high fuel pressure readings on the new pumps, that given a little time (i.e. an hour of flight or run time) if the diaphragm in the new pump would loosen up a little and have lower pressure? Link to comment Share on other sites More sharing options...
Darryl Posted January 30, 2012 Report Share Posted January 30, 2012 Thanks for your replies fellow CT Fliers! I had heard that there is a break-in period for the new fuel pumps. I just might keep my eye on the fuel pressure and see if that works out. I sent an email to my mechanic in the greater Seattle area saying that my Dynon EMS registers 6.0 psi - vs. the 5.8 limit. I said I am concerend that there could be fuel leaks and a subsequent engine fire. His reply to my email is below. He is a good guy and I am leaving his name out of it. I don't necessarily disagree with what he says. I would, however, like to see something official from Rotax saying this slightly higher PSI is OK. My mechanic says to reset the Dynon EMS to set off the alarm at a higher PSI. This reminds me of when I was taking flying lessons and my instructor told me to get back up or down to the altitude he wanted. Rather than making all the effort to climb or descend to the proper altitude, I would just twist the knob on the altimeter. Problem solved! Darryl ========================== Hi Darryl, Unless the fuel pressure gets over 7 or 8 psi and you are in extreme turbulence there is no way fuel would exit the carbs. Even with extremely high fuel pressure the excess fuel would dump into the intake manifold causing a very rich mixture but not overflow unless maybe you were inverted. In the event of a overflow because of a carb failure there is a drip tray under each carb with a drain line out the bottom so the chance of a fire because of high fuel pressure is nil. I have never heard of an in flight engine fire on a Rotax engine. As I explained the fuel pump has been tested and certified at 5.8 psi. That is the maximum this fuel pump is capable of putting out. What you are seeing is the tolerance deviation with your Dynon. The pump is actually putting out 5.8 psi which is still in range but the Dynon is recording 6 psi which sets off the caution alarm. We will reset the tolerance on your Dynon to 6 and that should take care if the issue. That should take about 5 minutes next time you're in the area. Signed Darryl's mechanic - Name omitted on this forum. Link to comment Share on other sites More sharing options...
Roger Lee Posted January 30, 2012 Report Share Posted January 30, 2012 Hi Darryl, 5.8 is the Rotax max, but 6 should be acceptable and the diaphragm may relax and the pressure come down a little with time (maybe). The other issue is many of the fuel pressure senders are anywhere from .3 to .8 psi off. When you turn the plane on the next time and before you turn the key take a look at the fuel pressure and see if it is zero. Many have a small reading just sitting. Link to comment Share on other sites More sharing options...
Darryl Posted January 30, 2012 Report Share Posted January 30, 2012 Will do. Thanks, Roger. Darryl Link to comment Share on other sites More sharing options...
Runtoeat Posted January 30, 2012 Report Share Posted January 30, 2012 Throwing in my 2 cents. My oil pressure reading is almost 20psi low on my analog gage. Installation of a mechanical oil pressure gage showed the pressure to be 20psi higher than the gage reading. The Dynon is digital but it still relies on the oil and fuel senders to transmit pressure data. I would go with the mechanic's logic in that the new fuel pump is not going over the max pressure of 5.8psi and the higher indicated at the Dynon is the downstream variances. Or, as others have suggested, the fuel pump is at the top end of it's limit during the break-in period. There are tolerances to all things manufactured and I would imagine that top end 3 sigma pressure may be 6.0psi for a pump that is manufactured to be a max. of 5.8psi. The best way to definitively determine pressure would be to install a mechanical gage in the fuel line. Link to comment Share on other sites More sharing options...
Darryl Posted January 30, 2012 Report Share Posted January 30, 2012 I just talked to Dave Armando on the phone. He is a tech advisor at Flight Design Connecticut. He said that fuel pressure of 6.2 or even a 6.4 psi is fine. The carbs are tested up to 14.0 psi. He said that it is OK to adjust-up my Dynon EMS so the high fuel pressure alarm doesn't go off when it surpasses 5.8. Also, he said that higher fuel pressure is generally a good thing. Darryl Swenson Seattle WA CTLS N172LM Link to comment Share on other sites More sharing options...
Roger Lee Posted January 31, 2012 Report Share Posted January 31, 2012 Hi Darryl, I believe you got incorrect advice. I have talked directly to Rotax on this. Rotax thinks they will hold up to 6.2 and maybe a tad higher and there is a reason why Rotax set the max limit at 5.8 psi. Each carb will be a tad different , depending if the float level is set correctly and if the needle valve with an internal spring is fully up to par as to what it's final pressure hold will be. The carbs will puke fuel out the vent tubes and the engine will run like trash from flooding. . Why do you think everyone else in the industry has been sending the carbs back. Rotax distributors built a special test station for new or returned carbs and why do you think Rotax has admitted to intermittent high fuel pressure issues and are covering all of them under warranty. For me I wouldn't run one in my personal plane over 6.0 and then I would have to prove that it wasn't flooding. A slight change in pressure at 6 during a flight and your flooding. I'll be in Rotax school Feb. 14-23 and I'm sure this will be a hot topic. Link to comment Share on other sites More sharing options...
Darryl Posted January 31, 2012 Report Share Posted January 31, 2012 Thanks, Roger. This begs a couple more questions: When might flooding occur? In flight? If so, could this result in engine failure? Also, does higher fuel pressure pose an engine-fire risk? Darryl Link to comment Share on other sites More sharing options...
Roger Lee Posted January 31, 2012 Report Share Posted January 31, 2012 Hi Darryl, High fuel pressure can occur at anytime. Rotax recommends with each new fuel pump that you test them up to 5000 rpm. Flooding won't shut the engine down, but it will run rough. Depending on where a person had his fuel vent lines it could present a risk. If fuel flows onto the hot exhaust it usually evaps so fast it isn't a problem. I have seen many a CT with carb float bowls leaks and it drips into the drip tray then down very close to or on, depending on how bad the leak is, right on the hot exhaust. I have seen many a client come into my shop with live fuel in the drip trays. As far as Rotax operating or mechanical parameters goes always trust the manuals unless they have published something different in writing. Sometimes there may be a fudge factor and sometimes not. Link to comment Share on other sites More sharing options...
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