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Fuel Pump

Dayton Murdock

Well Known Member
Hi all
Yesterday I took off Carson City heading for Sacramento to see my friends.
As I leveled off at 10,500 feet I did a instrument scan in the fuel pressure was reading .6 pounds and blinking red at me , after a few moments it was reading zero .The engine was running smooth for a little bit then things got rough I turned on the boost pump and headed back to Carson. What a shame the air was smooth the snowfall on the Sierras was absolutely beautiful I could've continued on my boost pump but I thought better of that plan. I just thought I would share the experience. My new pump will be here on Tuesday and all will be better again.
 
more info please

Dayton,
Good Job.
Can you give us more info on age and TT on fuel pump?
Mine is 20yrs old and 1100+ hours since new and wondering if I should replace mine as preventative maintenance. To preclude what you just experienced.
Thanks
 
I did an autopsy on mine that failed last summer. The main diaphragm was intact, but there are 2 nickel sized rubber diaphragms that act as check valves. Mine were hardened and not sealing very well.

Glad your trip back was a non issue.
 
Hi all
Yesterday I took off Carson City heading for Sacramento to see my friends.
As I leveled off at 10,500 feet I did a instrument scan in the fuel pressure was reading .6 pounds and blinking red at me , after a few moments it was reading zero .The engine was running smooth for a little bit then things got rough I turned on the boost pump and headed back to Carson. What a shame the air was smooth the snowfall on the Sierras was absolutely beautiful I could've continued on my boost pump but I thought better of that plan. I just thought I would share the experience. My new pump will be here on Tuesday and all will be better again.

Thanks for the post. Great decision. Learning/reinforcing knowledge vicariously is good.

Last week, while doing my run up my TYCO electric fuel pump toggle breaker failed. That was a no go.

Not many good options at 10.5 over the snowy Sierra's. I'm glad you're safe!
 
Weak Fuel Pump

With 850 hours since new on a new Vans O320, I noticed my fuel pressure was reading about 0.6 psi, on climb out, after shutting the electric pump off. Since the fuel pressure came up to about 5 psi with the electric pump on, I assumed that the problem was with the mechanical pump. Replacing the mechanical pump was not difficult except for safety wiring the new pump.

Leland
RV-9A with 890 hours and 11 years of flying
 
Rubber Parts

I have done a fair amount of aviation maintenance consulting and pre-buys over they years and always tell clients that after 10 years a rubber part has lived its life & doesn't owe you anything. That's every seal, o-ring, hose, diaphragm, tire, tube ect on the plane. Engine driven fuel pumps are one of those parts that maybe should be replaced at 10 years to keep trouble to a minimum.

Don Broussard

RV9 Rebuild in Progress
57 Pacer
 
Fuel Pressure Variation ?

My low pressure pump was installed maybe 5 years ago ( previous owner ) and has about 120 hours on it. The pressure goes low sometimes and back to normal, about 2-3 psi fluctuation. Boost pump always raises the pressure to normal. What causes fluctuation in the mechanical pump?
Also, if I climb to 8,500 MSL, pressure drops to bottom of green and returns to normal at 500 MSL (airport) for either pump. The OP goes down 5 psi also . Reducing atmospheric pressure should increase the gauge reading assuming the fluid pressures are controlled by springs in the fuel pump and OP relief valve. What am I missing ?
 
I have seen lots of fuel pumps with 2000 or more hours on them.
I have no fear of a fuel pump with 1000 hours or more than 20 years old.
 
Last edited:
You do not say why you believe the low pressure was caused by the mechanical pump being defective. It could be caused by other phenomena, like ice or fod in the fuel system between the boost pump and the mechanical pump. In the case of ice the problem would disappear when warmed.
 
You do not say why you believe the low pressure was caused by the mechanical pump being defective. It could be caused by other phenomena, like ice or fod in the fuel system between the boost pump and the mechanical pump. In the case of ice the problem would disappear when warmed.

I don't think ice was a factor the OAT was 41 deg and the fuel lines are in the exit air stream. 10 years of operation makes me think it time for the pump to be changed :rolleyes: least-way I hope this will solve the issue
 
Good call Dayton,

Assuming the pump failed due to a diaphragm failure, I assume some fuel could come out of the pump's vent port due to pressure from the boost pump. Do you recall seeing any evidence of fuel coming out the port?

Bevan
 
I have seen lots of fuel pumps with 2000 or more hours on them.
I have no fear of a fuel pump with 1000 hours or more than 20 years old.

Certainly they can last that long and longer. I've also seen a higher incidence of problems after the 10 year point because the rubber doesn't last forever. They seem to be more sensitive to years than engine hours. My only point was if a guy chose to be proactive 10 years was a reasonable target to think about replacing the pump.


Don Broussard

RV9 Rebuild in Progress
57 Pacer
 
We should to an autopsy on the bad pump (unless , of course, you have a core charge and have to return it).
 
Wondering

Dayton,
Wondering here if the new pump fixed the problem?
Any more info on why or how yours failed?

Going to be proactive here and replace my 20yr old 1100 hr. pump.
I did appreciate others opinions on the topic....thanks.
Spec's say 4-6 psi...I had one hour local fight yesterday where it ran under 4psi the whole time....so thinking it is tired. I do so many other things pro-actively I feel remiss just waiting for a failure such as Dayton's to happen. Plus the thought of it happening at the start of a weekend trip or worse yet in the middle of a trip....

Which one to buy?
ACS:
Tempest OH 260.
Tempest new 299.
Lycoming new 369.
Opinions?
Thanks
 
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