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Pump Limit Reached

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Old 11-10-2010, 01:00 PM
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Default Pump Limit Reached

Got this blinking error message on the HDT for my Rhino (which has 15 flights) after my last flight last week (left message on your work phone, no reply). Can't find any info in the instruction book as to why it occurred or how to fix it.

Roy
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Old 11-10-2010, 07:13 PM
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Default RE: Pump Limit Reached

Roy, few things I would check. If you are reaching pump limit, you may have a restriction somewhere in your fuel system. Check everything, UAT, fuel lines, fuel filter, etc...

Have you noticed if it take longer to refuel or pull the fuel out of the jet?

I am sure Eric will chime in sometime soon.
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Old 11-10-2010, 07:23 PM
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Default RE: Pump Limit Reached

Hello Roy

The most common reasons for “Pump Limited Reached” alarm:
Low battery voltage
Clogged fuel filter or UAT
Fuel line tubing pinched or bend anywhere between turbine and fuel tank clunk, (it can also be inside the turbine front cover
Fuel tank vent obstructed
Defective fuel pump

In other words, fuel pump is working too hard to get the necessary fuel to get the top RPM
I suggest trying to bypass some elements and see if you have a significant (100 point) PW reading reduction
Hope this helps
Juan
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Old 11-10-2010, 08:19 PM
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Default RE: Pump Limit Reached

Thanks for the replies. That is what I thought, also. This is my first Jet Central, but all turbines should react the same. My PST's show a voltage increase when they get clogged. So, I checked all the lines, except the one under the engine cover, and then cleaned out the filter. I did a restart and slowly advanced the throttle one click at a time and found the message pops up at the very last click of throttle input. As long as I don't use the last click of throttle, I don't get a message. I managed a couple of additional flights that day but did not peg the throttle stick and the message did not show again. The PW shows 75 at idle and over 800 at almost (one click short of) WOT giving 116,000 RPM. I should have checked the original WOT PW reading when I first got the engine, but neglected to do so. I don't have a baseline for the WOT. I also charge the battery every flight.
I will check under the engine cover and re-clean the external filter and give it another try. Thanks.

Roy
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Old 11-10-2010, 08:39 PM
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Default RE: Pump Limit Reached

Roy,
This is the reply I got from Eric with a question about my Super Eagle:


ORIGINAL: BluFox

Mark:

Pw range can vary considerably depending on installation of fuel systems. Just checked mine and it is in low 100's at idle and high 300's at wide open throttle.

I always check temp, rpm and PW the first run of the day. I enter this in a log book so I have a bench mark for comparison.

High PW is upper range of 600. If you reach the high 7oo's or get into the 800's look for a restriction or fuel pump issue.

Regards,
Eric
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Old 11-10-2010, 08:51 PM
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Default RE: Pump Limit Reached


ORIGINAL: Molar mender

Thanks for the replies. That is what I thought, also. This is my first Jet Central, but all turbines should react the same. My PST's show a voltage increase when they get clogged. So, I checked all the lines, except the one under the engine cover, and then cleaned out the filter. I did a restart and slowly advanced the throttle one click at a time and found the message pops up at the very last click of throttle input. As long as I don't use the last click of throttle, I don't get a message. I managed a couple of additional flights that day but did not peg the throttle stick and the message did not show again. The PW shows 75 at idle and over 800 at almost (one click short of) WOT giving 116,000 RPM. I should have checked the original WOT PW reading when I first got the engine, but neglected to do so. I don't have a baseline for the WOT. I also charge the battery every flight.
I will check under the engine cover and re-clean the external filter and give it another try. Thanks.

Roy
Eric will confirm, but my understanding is that the PW is roughly the ratio of the total voltage available that the ECU has to supply to the pump to maintain the requested RPM. I have several Rhinos and at full throttle, they all read in the low 500's, or roughly half of the voltage available. If you reach 1000, that means there is no more voltage available and the pump can't maintain the requested RPM, thus the error message. As has been explained here, poor battery condition that leads to an excessive drop in voltage under load and fuel system blockage are typical causes. I have had this condition twice and traced the first to a blockage in the little red fuel filter supplied with the engines (looked like grease) and the second was a faulty fuel pump.

If the batteries maintain voltage under load and the plane fuels and defuels normally, replace the fuel filter, check the fuel solenoid for proper operation and make sure there are no kinks or wire ties that could constrict fuel flow. You might also pull the fuel line at the engine connection and run the pump in test mode to make sure you get a good steady flow of fuel.

I would guess Eric will contact you shortly.
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Old 11-10-2010, 09:39 PM
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Default RE: Pump Limit Reached

Mark and Keith

Since this is a new engine, 15 flights 18 starts, I wouldn't expect any problems with the battery but have had initial pump problems with some of my other engines. My LiIon battery takes between 300-400 mAh each flight and holds good voltage under 1 amp load. I have not had any problems with fueling/defueling. I went out to the shop and checked the fuel line from the pump to the motor and no kinks. I checked the fuel line as it enters the engine cover and it is free moving. I checked the UAT and the internal bag appears to be clear but it has 200 flights on it with my old PST 1300R. It might be worth replacing it. My fuel is filtered four times before it reaches the UAT and those filters are replaced quite often.
As I recall, in the back of my mind, I remember that my PW value when I did the initial bench run was around 450 at WOT. Great suggestion about the log for parameters at the beginning of the day. I have a log, but it is for run time and flight times. I will have to expand that to include voltage and temps.
It may take a couple of days to do some pump checks as our weather takes a dump tonight and the rain returns.

Roy
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Old 11-11-2010, 08:18 AM
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Default RE: Pump Limit Reached

I had the same Error message a couple of weeks ago on my Rhino and it would not get above 1/2 throttle.
I opened up the Uat and found Algae inside clogging the filter. Drained all fuel and discarded.
Fueled with a new can and it's been running like a champ since.
If its not in a tank or the UAT Check the filters and valves.
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Old 11-11-2010, 12:44 PM
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Default RE: Pump Limit Reached

Just ordered another UAT. Might as well eliminate all the potential problems since this UAT has been around a while.

Roy
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Old 11-11-2010, 01:14 PM
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Default RE: Pump Limit Reached

Roy:

Sorry for being "Ghost like" for the past few days. . .FLU . . .and it really knocked me on my backside.

I just went through this with Lewis. . .by process of elimination Lewis concluded and I agree, the fuel pump solenoid was in the process of failing. bypassing it brought the turbine to life.

High PW is indicative of only one thing. . .a fuel restriction within the system. Since you have or will replace the UAT if the problem persists, next, bypass the fuel pump solenoid,(CAUTION, open the ON/OFF valve slowly during preheat) run and verify. If the problem still exists, change the Festo On/Off unit, run and verify. Last, connect the pump directly to a fuel source which is not part of the aircraft fuel system, run and verify.

If this is a new jet, please check to see if the brass fuel tubing used in the assembly of the fuel tank is cut clean and not "knurled in" which can happen when the mfg. of the jet kit may have used a tubing cutter. I experienced this with a FBJ MB-339 kit. The Super Eagle simply could not get the fuel needed.

Give me a call anytime to further discuss, or order a replacement part. We can work together to eliminate the issue.

Regards,
Eric
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Old 11-11-2010, 01:58 PM
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Default RE: Pump Limit Reached

Eric

Sorry to hear you got the "Crud". Hope you are feeling better now. I went and got my flu shot early this season because there are quite a few folks around here getting the flu. I just don't want to mess with getting sick this year. Too much to do.

Thanks for the diagnostic recipe. I did order a new UAT which should be here the first of the week. When I swapped out my PST1300R for the Rhino, I converted all my tubing to 6mm except for the feed line from the pump to the turbine that comes with the Rhino. I also make it a habit to hog out all my brass tubing after cutting to insure the inside diameter is restored. Then I clean my brass like you would a hand gun or rifle to make sure there are no particulates hanging around inside the tubing to foul the fuel system.

Since the weather is taking a dump this weekend I will work on it in the next day or so and post my results.

Thanks again for pointing me in the right direction.

Roy
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Old 11-20-2010, 04:54 PM
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Default RE: Pump Limit Reached

Eric

Got my UAT yesterday morning, installed last night and run this morning. All batteries charged, filter re-cleaned, and all tubing replaced. First start, UAT cleared of bubbles and PW readings taken. The UAT bag had a very noticeable black color so it was time to replace it.

Idle PW=74
WOT PW=810

Better, but nothing to shout about. The UAT produced almost a 200 point drop as I was getting the error message when it went over 999.

Took solenoid out of loop and big difference. Noticed a 10 point drop in idle immediately.

Idle PW=64
WOT PW=540

Spool up was noticeably faster also. So it looks like it was the solenoid.

Weather takes a real dump this weekend with up to 4" of snow so I won't be doing much flying in the next few days. Anything else I need to check?

Roy
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Old 11-20-2010, 05:39 PM
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Default RE: Pump Limit Reached

Roy:

Send me your address via email @ jetartessales@aol.com

I will send you a replacement fuel solenoid. Please install, run and compare figures. I apologize for the temporary difficulty. BTW, attended the adoption ceremony for Boli, Ann and daughter Marley. . .They are a family for sure !

Cheers,
Eric
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Old 11-20-2010, 07:04 PM
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Default RE: Pump Limit Reached

Eric

Address has been sent.

That's great about the adoption being final for Boli and Ann. Our oldest son has adopted all eleven of their children, some with special needs and it is always up in the air until those final papers come through. So we know about the waiting. Great news!!

Thanks for the help diagnosing the fuel problem. I will recheck the readings when the new solenoid is installed.

Roy
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Old 11-20-2010, 07:17 PM
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Default RE: Pump Limit Reached

Ta daa!

Thanks for the kind words Doc...see you in July if not sooner!

Beave

PS: Eric, Dave (Father in law), me, Anne, Marley, Judge, our lawyer, Dick (close family friend and the Warbird guy I fly with). When the Judge asked who Eric and Dick were, we responded "Honorable Grandpas".
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Old 11-20-2010, 08:37 PM
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Default RE: Pump Limit Reached

Boli

That looks like a most memorable occasion, congratulations!!!! Thanks for sending the info and photo.

Roy
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Old 11-20-2010, 11:49 PM
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Default RE: Pump Limit Reached

Doc,

We found out last night that yesterday was National Adoption Day. Kinda neat having our adoption finalized on that day.

Beave
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Old 11-21-2010, 12:09 AM
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Beave

What a perfect memory day. She looks contented. From the looks on all the faces in the previous photo, what a great family she will have to grow up in.

Roy
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Old 11-26-2010, 09:11 PM
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Default RE: Pump Limit Reached

Got the fuel solenoid valve this afternoon and did some testing this evening. The values are as follows:

Idle PW=75
WOT PW=710 It would only allow the turbine to spool up to 112.2K RPM It's down 100 from the old valve but no where close to no valve in-line.

I swapped out the solenoid with a just a Festo connector and got:

Idle PW=65
WOT PW=566 with 116.8K which is the normal RPM

I did not screw down the solenoid in its normal position thinking I might have crimped the tubing on one of the test start-ups but got the same high readings. It seems the turbine runs fine without the valve, goes to max RPM and has a good spool up time. Put the valve in and it takes a lot of voltage, does not reach full RPM and takes about a full second longer to reach max RPM.

Here is a photo of the install. I'm stumped.

Roy
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Old 11-27-2010, 08:03 PM
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Default RE: Pump Limit Reached

Did some additional testing this afternoon. I did find the rated voltage on the valve was 7v. I put a voltage meter in line with the pump to see what voltages are being sent to the valve. I first did a no load test, valve was bypassed so no fuel, and the following values were noted.

Idle 7.11v PW = 65 RPM 31.2K
WOT 6.55v PW = 560 RPM 116.2K

Then I put the valve back in service and the new values are noted.

Idle 7.04v PW = 76 RPM 31.1K
WOT valve voltage went to 6.44v and continued down to 6.23 as the PW increased from 760 to 850. The RPM stalled at 109K for a few seconds but slowly climbed to 112K. During that time the valve voltage decreased and the PW continued to increase.
I am sure the ECU was increasing the PW to try to get the RPM up to 116K but I backed the turbine down to idle as the PW hit 900. It never got higher than 112.8K on the RPM.

Roy
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Old 11-29-2010, 09:27 AM
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Default RE: Pump Limit Reached

Roy. . .

I don't think it is an ECU or Solenoid issue. I know it looks like it but we can replace ECU or solenoid (as we already did) and the problem won't be solved.
The ECU can not partially open the valve; it ether opens or closes it. We replaced the suspected solenoid for last generation one without any changes in the performance of your turbine.
PW of 566 is too high for a Rhino with solenoid bypassed. It is completely normal with the solenoid installed, the PW reading increases. We think the problem is the pump is cavitating.
There can be only two things that can provoke the symptoms you experience; a defective pump or an installation with a yet unfound problem.
Please confirm you have 6 mm lines from the clunks all the way to the fuel pump with no restrictions like small hole clunks, small tanks vents etc.
Next, we want you to bypass the fuel system and connect the pump directly to an external tank, run and see if the problem is resolved. If so, then by process of elimination work back to the tank, checking everything.
Let us know what your results are.

Eric
(as discussed with and relayed by Juan Ramon, Service Engineer)

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Old 11-29-2010, 10:57 AM
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Default RE: Pump Limit Reached

Eric

Sounds good. The only thing I haven't checked is the tank plumbing. It is the large custom Boomerang tank from Dreamworks so I will check the clunk and pickup and enlarge openings on both. If no change, I will put the 6mm line directly into the kerosene tank and see what happens.
Thanks.

Roy
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Old 11-30-2010, 11:49 AM
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Default RE: Pump Limit Reached

Eric

After an afternoon, yesterday, of tinkering, the tank plumbing has been redone. Test run this morning with on board fuel system made no change. So I bypassed the on board fuel system and went straight to the kerosene tank with 6mm tubing. The PW went straight to the blinking “Pump limit reached” at almost full throttle. So, I have run out of your instructions.

Roy
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Old 11-30-2010, 12:42 PM
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Default RE: Pump Limit Reached

Hello Roy
Just one last question,what kind of battery are you using?
We will ship you some spares tomorrow (too late to ship them today)
Juan
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Old 11-30-2010, 02:07 PM
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Default RE: Pump Limit Reached

I am using the supplied Duralite that came with the Rhino and a pair of 5 cell 1700mAh NiCad run in parallel for my receiver. I am using an Electro Dynamics Power Bus Pro that optically isolates all my digital servos on two separate 5 cell 4200mAh NiMH in parallel. My Rx batteries and the supplied Duralite battery is charged after every flight.

Roy
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