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Engine quit on takeoff rollout

Toobuilder said:
But you do mount the gascolator after the boost pump...
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Where you mount it makes no difference. Pressure and flow are two different measurements, like amps and volts. Just because you're pulling doesn't mean there is no pressure. Just like you in the wind tunnel, the gascolator can't tell the difference between a fuel pump before it or after it.
 
Toobuilder said:
But you do mount the gascolator after the boost pump...
Click to expand...

No. You mount the gasculator, on the firewall, from the fuel valve / tank. There's is no pressure. From the output of the gascolator it feeds the backup pump, from there to the mechanical pump. At this point you can collect any contaminants before it enters the pumps.
 
FasGlas said:
No. You mount the gasculator, on the firewall, from the fuel valve / tank. There's is no pressure. From the output of the gascolator it feeds the backup pump, from there to the mechanical pump. At this point you can collect any contaminants before it enters the pumps.
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My boost pump is before the gascolator.
 
bjohnson1234 said:
Where you mount it makes no difference. Pressure and flow are two different measurements, like amps and volts. Just because you're pulling doesn't mean there is no pressure. Just like you in the wind tunnel, the gascolator can't tell the difference between a fuel pump before it or after it.
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So, if you disconnected the fuel line from the gacolator and let the fuel pour out, you're saying there's high pressure?? That is less fuel then the pump is FLOWING though it.
 
FasGlas said:
So, if you disconnected the fuel line from the gacolator and let the fuel pour out, you're saying there's high pressure?? That is less fuel then the pump is FLOWING though it.
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No, I'm saying that any amount of flow means there is some pressure. The peak of that pressure is the pump. In any case, it's irrelevant because the Usher gascolator can handle the pressure whether it comes from the mechanical fuel pump after it or the boost pump before it.
 
Since this thread got a bit side tracked.. The question is???? Did you get your problem solved??
 
FasGlas said:
Since this thread got a bit side tracked.. The question is???? Did you get your problem solved??
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I think so, but I'm not 100% sure yet. It seems pretty likely that the engine quit because there was water in the air box. To fix that I drilled a hole in it and used filter grease to get a better seal on the bottom. I haven't ruled out a problem with the servo yet and I know I have a fuel boiling issue, but it's always been a minor issue at low rpm and has never caused the engine to quit.
 
FasGlas said:
No. You mount the gasculator, on the firewall, from the fuel valve / tank. There's is no pressure. From the output of the gascolator it feeds the backup pump, from there to the mechanical pump. At this point you can collect any contaminants before it enters the pumps.
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That may be how you plumb your system, but that's not the norm in this world. Most boost pumps in this world are well inside the firewall, as close as practical to the fuel source. Boost pumps work much better pushing than pulling.
 
bjohnson1234 said:
Where you mount it makes no difference. Pressure and flow are two different measurements, like amps and volts. Just because you're pulling doesn't mean there is no pressure. Just like you in the wind tunnel, the gascolator can't tell the difference between a fuel pump before it or after it.
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Perhaps I'm not following this closely enough, but there is a big difference between pulling and pushing fuel through something. Yes, the pressure drop is only a function of flow and geometry, but the absolute pressure along the system will be different in your scenario. It is very desirable to keep the minimum absolute pressure along the path as elevated as possible.

At sea level pressure, 100LL boils at around 140F. Pull a little on it, as in the line upstream from the boost pump, and the boiling temperature goes down. The best place for the boost pump is right next to the tank. Indeed, cars put the pump inside the tanks.
 
Walt said:
You should ground the aircraft and find someone qualified to help you sort this out before you become a statistic :eek:
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This is still the best advice you have received to date. Dust off your cheque book and get some professional assistance.
 
Captain Avgas said:
This is still the best advice you have received to date. Dust off your cheque book and get some professional assistance.
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I don't have a problem paying someone, but at this point what are they going to do? Tear the plane apart trying to diagnose a problem with no current symptoms? I just had a conversation with Don at Airflow Performance about the engine quitting, the water in the airbox and the cleaning and at this point I feel pretty comfortable with it. On the ground the engine runs great from idle to full throttle hot and cold.

I have not been able to replicate the low fuel pressure with the mechanical pump, but the boost pump restored normal pressure so that's not an emergency issue. No problems with the ignition system and no symptoms of issues with the fuel controller. Tearing apart the plane looking for a problem can potentially create a problem. I know this fact is largely lost on the GA community, but most failures occur soon after maintenance or overhauls. There is a very reasonable explanation for the engine quitting, albeit an impossible one to confirm. I very much appreciate everyone's input and concern, but at this point I feel like the potential downside of messing with a plane that is running great outweighs the small possibility that something else is wrong.
 
bjohnson1234 said:
Also, servo is precision model RSA-5AD1/2576535-A Serial #70242209
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My Precision servo install instructions say to put a cleanable 30 micron filter either immediately before or after the mechanical fuel pump. Does your Usher gascolator have a screen and if so, what size is the mesh?

The Precision servo also has a very fine filter in the inlet but it has very small capacity. Considered to be a "last resort" filter. Have you checked this filter?

I don't see why the gascolator has to be on the firewall where it will pick up heat.

Bevan
 
bjohnson1234 said:
I don't have a problem paying someone, but at this point what are they going to do? Tear the plane apart trying to diagnose a problem with no current symptoms? I just had a conversation with Don at Airflow Performance about the engine quitting, the water in the airbox and the cleaning and at this point I feel pretty comfortable with it. On the ground the engine runs great from idle to full throttle hot and cold.

I have not been able to replicate the low fuel pressure with the mechanical pump, but the boost pump restored normal pressure so that's not an emergency issue. No problems with the ignition system and no symptoms of issues with the fuel controller. Tearing apart the plane looking for a problem can potentially create a problem. I know this fact is largely lost on the GA community, but most failures occur soon after maintenance or overhauls. There is a very reasonable explanation for the engine quitting, albeit an impossible one to confirm. I very much appreciate everyone's input and concern, but at this point I feel like the potential downside of messing with a plane that is running great outweighs the small possibility that something else is wrong.
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This might be some more information for you. A friend of mine came in from Indiana last night and we got to talking about fuel injection systems. He builds and fly Pitts. Pitts having a metal fuel tank with a flop tube have a problem with very small metal particles getting into the fuel from the flop tube end hitting the metal tank. These particles are small enough to get by the servo filter and get stuck in the fuel divider. They cause the plunger to stick ( either open or closed ), the clearance is said to be .002. During their yearly inspection they disassemble every divider, clean and inspect them. He also says the Bendix dividers are less of a problem then the AirFlow dividers. Might be somewhere to look for your problem.
 
Bevan said:
My Precision servo install instructions say to put a cleanable 30 micron filter either immediately before or after the mechanical fuel pump. Does your Usher gascolator have a screen and if so, what size is the mesh?

The Precision servo also has a very fine filter in the inlet but it has very small capacity. Considered to be a "last resort" filter. Have you checked this filter?

I don't see why the gascolator has to be on the firewall where it will pick up heat.

Bevan
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I have a filter before the electric fuel pump, not sure if it's 30 micron or not and not sure about the Usher gascolator screen.

As far as the placement goes, I guess maybe no one wants to cut a hole in the floor for the drain inside the cabin.
 
Just an update - I have had no further issues and I believe the issue was ingesting water from the filter box. I have added a drain hole to prevent any future pooling.
 
What size hole? If I recall, the plans call for a 3/16 hole and often thought water wouldn't drain through such a small hole unless there was some pressure (vertical accumulation) but may not drain the last of the water. How much water in the filter bowl is too much?

Bevan
 
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