P80 starting problems
04-29-2011, 12:41 PM
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P80 starting problems
Hello,
I have a P80 and recently it is getting hard to start. It is aborting startup with ACCEL LOW error when it reaches the 30000rpm. Pump U-accel1=0.200 and U-accel2=0.850.
I tried up to U-accel1=0.3 but it helped a little. I also put U-accel2=0.875 but no success. When the engine starts it works OK and it can get up to 1200000rpm.
EGT startup temp is about 650 to 700C and average temp is 520C.
I noticed a small flame coming out at 3 to 5’oclock and red cone at startup, idle and up to 50000rpm. Increasing more then 50000rpm the flame disappears.
Any ides what could be the trouble?
Many thanks
Vince
I have a P80 and recently it is getting hard to start. It is aborting startup with ACCEL LOW error when it reaches the 30000rpm. Pump U-accel1=0.200 and U-accel2=0.850.
I tried up to U-accel1=0.3 but it helped a little. I also put U-accel2=0.875 but no success. When the engine starts it works OK and it can get up to 1200000rpm.
EGT startup temp is about 650 to 700C and average temp is 520C.
I noticed a small flame coming out at 3 to 5’oclock and red cone at startup, idle and up to 50000rpm. Increasing more then 50000rpm the flame disappears.
Any ides what could be the trouble?
Many thanks
Vince
04-29-2011, 03:26 PM
#2
RE: P80 starting problems
Assuming a powermax/propane start engine, possibilities to consider:
1. My experience is that weak fuel pumps can stagnate in that rpm region (30K to 45K) and cause a failed start. Solution is to try another pump. Check the Max Pump Voltage after a successful run at full power. If it's at around 3.0v (maybe higher on an SE engine), it's a tip off the pump is not so good.
2. 30K rpm is in the rpm range (higher in some cases) where the starter motor disengages. Possible the bendix is sticking and the starter remains engaged dragging on the shaft causing the engine to fail to start. You can either watch it during start or put your finger on the starter motor housing or front case and feel it disengage.
The flame coming out the back is pretty normal if its a short blue flame. If you do a start at dusk or night, the exhaust area becomes bright orange.
You don't need to change Uaccel1 if the pump starts and you get an immediate acceleration with kero. As far as Uaccel2 goes, look for a pause or sag in engine rpm when the propane turns off. If so, then change Uaccel2 by .050 or .075. If it continues to sag or hesitate bump it up a little more. If you get yellow flames out the back, you went too far. The engine should continue to accelerate thru that region as though the propane was never there.
1. My experience is that weak fuel pumps can stagnate in that rpm region (30K to 45K) and cause a failed start. Solution is to try another pump. Check the Max Pump Voltage after a successful run at full power. If it's at around 3.0v (maybe higher on an SE engine), it's a tip off the pump is not so good.
2. 30K rpm is in the rpm range (higher in some cases) where the starter motor disengages. Possible the bendix is sticking and the starter remains engaged dragging on the shaft causing the engine to fail to start. You can either watch it during start or put your finger on the starter motor housing or front case and feel it disengage.
The flame coming out the back is pretty normal if its a short blue flame. If you do a start at dusk or night, the exhaust area becomes bright orange.
You don't need to change Uaccel1 if the pump starts and you get an immediate acceleration with kero. As far as Uaccel2 goes, look for a pause or sag in engine rpm when the propane turns off. If so, then change Uaccel2 by .050 or .075. If it continues to sag or hesitate bump it up a little more. If you get yellow flames out the back, you went too far. The engine should continue to accelerate thru that region as though the propane was never there.
04-30-2011, 12:18 AM
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RE: P80 starting problems
Thanks for your reply. The max pump voltage at 120000rpm is 2.5v. Re the sag when propane is off, there is no sag, and the starter motor seems to be disengages OK.
I noticed the following:
1. There is a sag of rpm at 30K, at this time the engine will shutoff or continue accelerating.
2. Time between accelerating mode up to 30K is about 10seconds, I noticed if it is 9 or 8sec it will run, but if it exceeds 10sec it will shutoff.
Attached is an image that show the graph during failure of rpm and pump voltage.
Regards
Vince
I noticed the following:
1. There is a sag of rpm at 30K, at this time the engine will shutoff or continue accelerating.
2. Time between accelerating mode up to 30K is about 10seconds, I noticed if it is 9 or 8sec it will run, but if it exceeds 10sec it will shutoff.
Attached is an image that show the graph during failure of rpm and pump voltage.
Regards
Vince
04-30-2011, 01:50 AM
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RE: P80 starting problems
Vince
Have had the exact same problem with my P80 the past few weeks. It is 5yrs old and has 34hrs run time all on origional pump and 1250mA battery. Made the adjustments and checks you have done with no effect or result. Finally changed the gas setting to 80% from 60 and connected a 2200mA lipo. Have now done 3 starts with no failures or sagging rpm at the 30k point.
Hope this is of some help.
Phil
Have had the exact same problem with my P80 the past few weeks. It is 5yrs old and has 34hrs run time all on origional pump and 1250mA battery. Made the adjustments and checks you have done with no effect or result. Finally changed the gas setting to 80% from 60 and connected a 2200mA lipo. Have now done 3 starts with no failures or sagging rpm at the 30k point.
Hope this is of some help.
Phil
04-30-2011, 05:16 AM
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RE: P80 starting problems
I think that I solved the problem at least for now. I changed the U-accel1 from 0.3 to 0.35v and reduced U-accel2 to 0.8v from 0.85v. With this setting I had 5 good start-ups, but I think the pump is sagging at 30K and was close to startup failure.
Attached is an image showing graph of a good startup. Notice that flat area of rpm at 30K, the pump voltage is still increasing but rpm remains near 30K for about 2sec. I think if this flat area had persisted a little more, the startup would be aborted.
I do not know how this flat area is there and is not keeping accelerating. My best shot is the pump is sagging at 30K as “Thud Driver” suggested.
Regards
Vince
Attached is an image showing graph of a good startup. Notice that flat area of rpm at 30K, the pump voltage is still increasing but rpm remains near 30K for about 2sec. I think if this flat area had persisted a little more, the startup would be aborted.
I do not know how this flat area is there and is not keeping accelerating. My best shot is the pump is sagging at 30K as “Thud Driver” suggested.
Regards
Vince
04-30-2011, 10:13 AM
#6
RE: P80 starting problems
A couple years ago, I got a dozen or so "bad" pumps from JetCat and tested them on a P-80. About half would stop accelerating the engine in the 30-45K rpm range, as I stated above, and fail to complete the start. Some of the rest wouldn't get the engine to max rpm.
Looking at everything else said, my best suggestion is to replace the pump. You are basically just barely (or not) staying ahead of the required acceleration ramp. Increasing the gas % is one I hadn't thought of and maybe that will keep you in business for awhile. 2.5v max pump isn't bad at all.
Looking at everything else said, my best suggestion is to replace the pump. You are basically just barely (or not) staying ahead of the required acceleration ramp. Increasing the gas % is one I hadn't thought of and maybe that will keep you in business for awhile. 2.5v max pump isn't bad at all.
