Pascal B Posted December 22, 2023 Author Report Share Posted December 22, 2023 As stated in the beginning of this thread, fuel vent was one of the first obvious issues that I checked. There was absolutely no obstruction there. I tend to agree with Tom Baker that there is a restriction somewhere in the lines of the fuel system that allows a trickle to refill the gascolator but not enough to run the engine at power. And I intend to proceed more or less as anticept suggested, except that i will be using a funnel with a chamois strainer into a jerrycan, to make sure i do not miss any telltale residues Quote Link to comment Share on other sites More sharing options...
Anticept Posted December 22, 2023 Report Share Posted December 22, 2023 Did you throttle back at all? It really doesn't take much fuel at minimal power settings. Quote Link to comment Share on other sites More sharing options...
Pascal B Posted December 22, 2023 Author Report Share Posted December 22, 2023 I throttled back to idle to restart, tried getting some more revs but engine started coughing from presumably fuel exhaustion immediately. I then pulled the throttle back to idle because I did not want a destabilizing burst of unpredictable power on final. Thinks happen a bit quickly, I was quite low by then and did not have much time ( or mental capacity) to experiment with throttle settings… Quote Link to comment Share on other sites More sharing options...
Anticept Posted December 22, 2023 Report Share Posted December 22, 2023 What type of electric fuel pump? Part number? I am curious if debris could "jam" it. Quote Link to comment Share on other sites More sharing options...
Pascal B Posted December 22, 2023 Author Report Share Posted December 22, 2023 Fuel pump make is Pierburg, originally for carburetted cars. I do not have a parts number handy. Remember that microlights where i fly are not bound to use certified parts. The same pump is in use in hundreds of microlights as a back-up or just to fill the carb bowls before cranking. It has originally an internal tiny inline filter, which tends to clog, hence a bypass circuit whith a non-return valve. Anyway my pump worked fine (delivering a gallon an a half per minute off the aircraft). And nothing suspicious dropped out when I unbolted it. Also, I think if it had been jammed, it would have blown its circuit breaker. Quote Link to comment Share on other sites More sharing options...
Madhatter Posted December 22, 2023 Report Share Posted December 22, 2023 It has to be fuel, replace all fuel lines, fuel pump, fuel valve, clean out fuel tanks, remove and inspect the gasculator then you know everything is correct and new. Trying to isolate an intermittent problem is not worth it when the cost of replacement is minimal. Quote Link to comment Share on other sites More sharing options...
Anticept Posted December 23, 2023 Report Share Posted December 23, 2023 Pierburg electric backup pump? Or Mechanical? As for popping the circuit breaker if it jams: it may or may not pop it. A jammed pump doesn't guarantee breaker popping; remember that breakers are to protect wiring, not necessarily devices. Not all brushless motors that stall will draw enough current for example. Quote Link to comment Share on other sites More sharing options...
ct9000 Posted January 3 Report Share Posted January 3 Re reading this incident I remembered when my LS was first assembled. The fuel hose at the tank connection takes a right angle bend because there is not much room for a gentle curve so the hose is very prone to kink at that point. The symptom was good flow at the gascolator but a long time to fill the header tank when drawing from one tank but the other was ok. Can't remember which was the bad tank. Problem solved by careful repositioning of the hoses. The hose end is molded to a bend so is really hard to see if it is kinked. Hope this is food for thought. Quote Link to comment Share on other sites More sharing options...
FlyingMonkey Posted January 3 Report Share Posted January 3 You mentioned the airplane was disassembled and trucked out of the field you landed in. You must have drained the tanks to do that...was that done by opening the gascolator valve? If so you would have seen the flow for all the remaining fuel in the tank. Quote Link to comment Share on other sites More sharing options...
Pascal B Posted January 7 Author Report Share Posted January 7 I dismantled the complete fuel system, pulled out and replaced all the fuel lines,filters and fitted a new mechanical pump, just as a precaution,because i found no fault with the old one. Wings should go back on next weekend and then I will test how much fuel flows to the gascolator on gravity alone, before running the engine at cruise settings on the ground. I tend to agree with Ct900's suspicion about a potential kink in the right angle bend of the hose at the tank connection being the likely culprit. When we took off the wings to take the plane out of the field, we first tried to drain the fuel via the gascolator, but the flow was quite slow. But then again, we had to push the plane several hundred meters to get near an accessible track and there it was sitting with the nose uphill and right wing (the full one ) low, so not optimal for draining. We plugged the exit, pulled the wings and then drained the tank directly, off the aircraft. Before that we did a visual inspection for obvious kinks but found none. The fuel lines had been undisturbed since renewal a year and over 55 flight hours ago. But then again, as somebody said in this thread, things work until they don't...As a future precaution, I have now fitted rigid 90 degree connectors at the tank exits so the flexible line is mostly straight and does not have to follow any tight radius. Expect an update after my first tests. Quote Link to comment Share on other sites More sharing options...
GrassStripFlyBoy Posted January 7 Report Share Posted January 7 Depending on what brand hose and diameter (metric or englsih), pushing the hose over the barb / bump can be a chore. I've heard of people using a bit of grease to aid here, I'm not a fan of that. A heat gun warming the rubber helps a bunch. Being 90 degrees you may be hating life trying to pull that hose v/s the angle allowing for some push aspect? Also use Hylomar on the fittings for sealant. Quote Link to comment Share on other sites More sharing options...
Pascal B Posted January 14 Author Report Share Posted January 14 The wings are back on the bird and GrassStripFlyBoy was right, the 90 degree rigid bends were a pig to fit because you now have two additional collars fighting for space. But a few bloody fingers later, they sit snugly and the rubber hose (8mm Gates) is definitely kink-free and has no tight bend to negotiate anymore. First gravity only flow tests with approx 5 gallons in each wing give 17 gph at the gascolator for the right tank, 17.1 gph for the left and 24.1 gph if both tanks are switched on. Which is at least 3 times more than the engine can digest, so I am happy with the result. Engine runs will have to wait because of the weather. -5 C is a bit cold for outside work... Quote Link to comment Share on other sites More sharing options...
Roger Lee Posted January 14 Report Share Posted January 14 Just like FD did on some you can install a 90 degree aluminum tube in the hose or even easier you can install a spring and no more kinks. I use springs in bad spots. Never failed me since 2006. Quote Link to comment Share on other sites More sharing options...
Pascal B Posted January 31 Author Report Share Posted January 31 First test flight today. Half an hour more or less circling the airfield as a precaution. Both tanks feed as they should, separately as well as together. Fuel pressure in the green, 0,3 bar on the mechanical pump, 0, 44 on the electrical pump. So the problem seems to have been solved by using solid fuel lines for every unavoidable sharp bend. But before that, Murphy's law had yet one more strike against me: the new mechanical pump I installed as a precaution was a dud right out of the box...what are the odds? At idle, it was ok, but above 4500 rpm, pressure dropped into the red. The flying school on the airfield ( Comco C42 Ikarus) had 2 original Rotax pumps displaying the same symptoms. Makes you wonder about parts quality control... Quote Link to comment Share on other sites More sharing options...
Tom Baker Posted January 31 Report Share Posted January 31 SB-912-063UL Check paragraph 3.6.1 . Quote Link to comment Share on other sites More sharing options...
Pascal B Posted January 31 Author Report Share Posted January 31 I am well aware of the above mentioned SB. But there is a difference between allowable temporary fluctuations such as when the carb bowl float needles open and a constant downward trend. At 5000 rpm the pump just could not keep up, with pressure dropping below 0.1 bar and not recovering... Quote Link to comment Share on other sites More sharing options...
Pascal B Posted January 31 Author Report Share Posted January 31 Just to complete the reply. The pump issues experienced by the flying school at my airfield resulted in loss of power and were not just "allowable temporary fluctuations". When they complained to Comco, they got the reply that there was a bad batch of pumps in ciruclation and that these things happen... Quote Link to comment Share on other sites More sharing options...
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