Engine Stalls When Started - Fuel Pressure

[OntheNumbers]

Looking for some suggestions as to possible cause here.

The symptom is the engine starts the normal way, then after a couple of seconds it stalls. If I re-engage the ignition it starts up again, then dies the same way. This has happened twice, once to me and once to my buddy who flies my plane. Both times it was cold out - around 0 Centigrade. My buddy had the presence of mind to look at the fuel gauge and noted low pressure, flipped on the boost pump and she ran OK.

In my case, I got her started and she kept running. I let her get warm, did a thorough run up and a quick jump to full power, everything was fine. We both went flying.

Engine is O-360 A2F, installed in a Cardinal. Has been running fine for the 1.5 years that I've owned the plane. Starts right away and usually stays going.

Fuel pump may be due for a replacement, was replaced at last overhaul but that was many years ago. Definitely not trying to cheap out here, but looking for suggestions on how to troubleshoot this a little before taking the leap. My AME suggested just keeping an eye on it and don't forget the boost pump if the mechanical gives out. It's only happened twice, like I say so early days yet. But I found one web posting that said if the diaphragm gives out the engine compartment can get sprayed with fuel with bad results - hence this post.

Cheers,

OTN

[cgzro]

don't know about the continental, but the lycoming pump has two diaphragms with a bleed line between them. So if either one gets punctured you see oil or gas in the bleed line.. Also the lycoming pressure comes from a spring releasing and not the engine, which only compresses the spring, so as the spring ages the pressure drops.

i believe the bleed line should go outside the plane to avoid spraying fuel in the engine compartment.

[photofly]

Forgive my ignorance, but why does a normally aspirated engine in a high wing have a fuel pump? Inadequate fuel supply without?

[Colonel Sanders]

The same thought occurred to me. I suspect it is a fuel-injected RG:

http://en.wikipedia.org/wiki/Cessna_177 ... ssna_177RG

the 177RG had a 200 hp Lycoming IO-360 engine

which has both mechanical and electrical fuel pumps.

[zulutime]

if this were a car the first thing I would look at is the fuel filter.

[jamesel]

So it's a '69 with the fixed Pitch (and fixed gear)? Personally, I would dig into Why the engine quits before going flying again.

Do you belong to Cardinal Flyers Online? There's a lot of accurate information on that site, and would be the first place I'd ask for help...... [url]http://www.cardinalflyers.com/[url].

[cgzro]

Some fuel filters in the engine are spring loaded so that if it gums up the fuel flow will push it open and avoid starving the engine. Perhaps the filter is gummed up and opening at higher pressure / rpm but closing at very low/start rpm, in any case checking all the fuel filter points is a good starting point.

Could also check the idle mixture, should give a 50 rpm increase before the engine dies when you pull the mixture. If it rises more its too rich and if it does not rise its too lean.

[Colonel Sanders]

If you really have a carburetor - which I doubt - you
might simply need to slightly enrichen the idle mixture
setting for the cold temps, to compensate for the low
density altitude (and extra O2).

If your Lycoming is fuel-injected, see SIL RS-67.

[OntheNumbers]

Thanks for all the tips and help.

I forgot to mention, it's Lycoming engine, but I guess that's obvious given the model. BTW, @jamesl - wow you got it, a 1969 C-177A, FG/FP. Yes, I'm a member of CFO, will send them a message too. But a fuel issue seems general enough and not specific to type, no?

@Photofly - not sure why the Cardinal has an aux fuel pump but it might be because Cessna had plans to make them somewhat aerobatic maybe. The checklist has you test it just prior to take off but generally the thing stays off.

I've been looking at the diagram of the fuel system in the POH looking for things that could be intermittent. @Peter, I didn't know about the internals of a fuel filter so thanks. And the filters are a cost-effective place to start the search. I always check the vents by blowing into them and dip the tanks after a flight and NO loud woosh of air as it inrushes to equalize the pressure in the tank. I've had that on a rental before, though. Those problems would tend to worsen the more you tried to run the engine until it probably wouldn't run at all (might take a while to get to that point, though).

Another possibility is that fuel is leaking out somewhere before it gets to the carb. But wouldn't I be able to smell it? I've smelt no fuel in the air before or after a flight. The plane was in for an annual inspection in November and the very first time I took it for a flight was the first time the problem occurred. I'll drop in on my AME and ask him if he routinely does anything to the fuel system as part of the annual - doesn't show up in the work logs, though.

I appreciate all your feedback,

OTN

[photofly]

@Photofly - not sure why the Cardinal has an aux fuel pump but it might be because Cessna had plans to make them somewhat aerobatic maybe. The checklist has you test it just prior to take off but generally the thing stays off.

I'm not asking about the aux pump - I'm asking about the engine driven one. C150/172/182 manage without one (and hence no need for aux pump at all), the fuel is gravity fed. Just curious.

[Heliian]

You have engine troubles, talk to an engineer. This is not something to play around with

[Colonel Sanders]

Check your vents and check valves. Anything
with moving parts should get close scrutiny,
after all these decades.

It could be that you have a sticking valve that
is opened up when you flip on the electric boost
pump.

Does the behaviour change depending upon
how much fuel is in the tank? ie if this happens
when the tanks are full, but is not noticeable
during start when the tanks as 1/4 full, that
would point towards the complicated venting
plumbing of this fuel system.

[OntheNumbers]

Thanks Colonel - I'll spend some time this weekend reviewing the flight notes and putting together the information. Surprising how often that can point to specific areas to look at. But I hadn't considered that the fuel tank levels themselves might be a factor.

@heliian - actually, I am an engineer. Just not an aviation one It's my plane so I want to be clued into the causes here even if I don't end up being involved in their repair. Maybe I can avoid this happening again, etc.

A propos my point above about collecting information, since posting this I started remembering some other details. I'd be interested in how far-fetched anyone thinks this is:

Observables:
[*]Hard starting on 2 occasions (engine dies, noted above)
[*]Spray of "oil" accumulating on left ldg gear strut. This was a very thin layer of what I thought was oil leaking out from a specific place on the underside of the cowling. Now I'm wondering whether there is a fuel leak under the cowling and, fuel being a solvent, is mixing with oily parts and spraying out during flight.
[*]Perceived increase in fuel consumption since the last annual


Possible Scenario:
If all three of these are related then maybe we have a fuel leak under the cowl which has the effect of:

[*]Reducing pressure in the carb
[*]sprays around inside the cowl causing oil to dissolve and be blown out during flight
[*]increases fuel consumption

The last two points are impressions - I have enough flight records to run the numbers and see if fuel really has increased. Maybe this is out to lunch, you would think fuel randomly flying around under the cowling would be more noticeable in other ways.

Anyhow, that's enough of a theory for me, I'll be visiting the AME next week. I'll keep y'all posted.

[GyvAir]

I think if you had a fuel leak large enough to be washing the oil out of the engine compartment, you would be smelling it at some phase of the flight, and you would be seeing blue dye residue somewhere. If your paint isn't white or some other colour that will contrast with the blue, give the belly or wherever you suspect fuel/oil to be tracking with a white rag and see if it comes up with some blue hues.

Good attitude!:

It's my plane so I want to be clued into the causes here even if I don't end up being involved in their repair. Maybe I can avoid this happening again, etc.

The plane is probably going to be working just fine the day you call the AME over to look at it, so understanding the system and making note of anything happening that's actually abnormal about its operation should help expedite a resolution to the problem.

[Heliian]

Could be anything from ice to internal carb issues. Its good that you want to be knowledgeable about your aircraft especially if its an old beater. If there is a mysterious fluid coming out of my cowl id be checking that too. What kind of fuel are you using? What kind of time is on the engine? When was your last annual?

[OntheNumbers]

Could be anything from ice to internal carb issues. Its good that you want to be knowledgeable about your aircraft especially if its an old beater. If there is a mysterious fluid coming out of my cowl id be checking that too. What kind of fuel are you using? What kind of time is on the engine? When was your last annual?

Hi HI,

Using 100LL from Alpha Aviation - never had a problem with that before. Never saw water in a preflight, either, but I always check. 1000 hours on the engine, 32 years since last overhaul (I know - but that's a different subject). Last annual was right before I started noticing the problem.

Not really a beater, though, it's been loved by previous owners and conservatively, I'd rate her as 7/7.

@gyvair - thanks for the feedback. The residue on the cowling and gear strut was gray, didn't feel oily, maybe two molecules thick compared to the usually greasy belly we usually see and unusual in that regard. I might have a look under the cowling myself before I pay the AME a visit. Paint is original blue on white and the stained part was all white - didn't notice any blue there, will take a very close look.

I never considered the carb. as a possible source. Since a major symptom of the problem is related to fuel pressure, I've been thinking it must have been a fuel pump or plumbing problem. Is there a failure mode in the carb. that would affect pressure readings?

[black hole]

Oh for christs sake! If you knew what a choke was for. I'd tell you to give it a little more choke. But alas: this is aviation modern days. And the new dweebs don't know a cold engine if it fell on them. And the instructor's today don't know enough to tell them.-------You just figure out how to give it a little more fuel when its cold. Maybe around your airport; there is an "old guy" he'll fix you up.

BH

[OntheNumbers]

Oh for christs sake! If you knew what a choke was for. I'd tell you to give it a little more choke. But alas: this is aviation modern days. And the new dweebs don't know a cold engine if it fell on them. And the instructor's today don't know enough to tell them.-------You just figure out how to give it a little more fuel when its cold. Maybe around your airport; there is an "old guy" he'll fix you up.

BH

BH, I sense your exasperation. If cold starting is all it is, I will be very happy. However, the engine is behaving differently post-annual compared to the entire 12 months before that, plus there are other circumstantial clues I've noted above which - to this dweeb - are hard to ignore and better safe than sorry I always say. Too bad I wasn't recording OAT on days when I flew, otherwise it would be another data point. We engineers love analyzing data!

I am relatively new at ownership. Maybe once I'm an old dog flying I'll be more relaxed about things like this. Meanwhile, I'll continue seeking education on forums like this to maximize the chance I actually get to adopt a venerable moniker such as "old dog flying".

I appreciate your reply, though - thanks!

OTN

[cgzro]

What was done on the engine during annual? Ive had a number of problems after annual such as idle speed set too low, idle mixture wrong, timing set 5 degrees earlier than spec, non grounded mags, mag leads loose, pump missing bracket and hitting/making hole in gas tank, screws too long and pierced gas tank, screws too loose and went into wing cutting rib lacing , internal wing damage that was not spotted ... Etc.

Really pays to learn how everything works and how to diagnose problems.

[OntheNumbers]

Observables:
[*]Hard starting on 2 occasions (engine dies, noted above)
[*]Spray of "oil" accumulating on left ldg gear strut. This was a very thin layer of what I thought was oil leaking out from a specific place on the underside of the cowling. Now I'm wondering whether there is a fuel leak under the cowling and, fuel being a solvent, is mixing with oily parts and spraying out during flight.
[*]Perceived increase in fuel consumption since the last annual


Possible Scenario:
If all three of these are related then maybe we have a fuel leak under the cowl which has the effect of:

[*]Reducing pressure in the carb
[*]sprays around inside the cowl causing oil to dissolve and be blown out during flight
[*]increases fuel consumption

Well I had a real adventure, removing the cowling for the first time myself and having a good look around for evidence of fluids gone wild inside the compartment. Nothing on the inside opposite the mysterious mess on the exterior underside of the cowling; no sign of excessive oil there or anywhere else compared to what I recall from attending the first day of the annual with the AME. Noted signs of blue dye on:

- Fuel pump around the perimeter
- Metal fitting of the air intake at the bottom of the Marvel Schebler
- Small blue oily stain on the nose gear fairing, possibly an artifact of over priming

And no blue on the inside of the bottom cowling that I could see - no blue or discoloration (except the usual grime) of any kind on the zinc chromate green finish.

I taxied away from the hangar to the apron for better light; engine started right away (48 F OAT) pressure came to about 4 psi, no problems. Engine ran like a top. Watched the RPM as I pulled the mixture to cutoff and noted a momentary jump. Engine had been running several minutes by this time compared to only about 2 or 3 for the taxi back - that time the mixture test revealed a flat RPM until she died, no jump.

Found the bleed line from the fuel pump and noticed two thin pieces of what looked like rubber sandwiched between metal on the pump. The bleed line fed into the pump right between those rubber sheets and is vented to the outside right next to the fuel strainer outlet. Very cool.

I went through 2013's worth of flights with a spreadsheet and calculated the fuel burn. Lots of variation which I attribute to inaccuracies reading the dipstick and a couple of mistaken readings. Generally fuel burn is 9 or 10 GPH for most of the year. The perception of higher burn right after the annual appears to have been a mistake I made either dipping the tanks or recording the amount - 20 GPH for that one flight where it was back to 10 GPH the flight before and the flight after. So I drop that data point from the investigation.

So far, looks like a good case of paranoia which prompted this post. I've been reading up on how a choke works and applying that knowledge to the Lycoming. BH, I don't know if you know this but my O-360 doesn't have a choke. Many don't, apparently. Instead of that, the technique, according to my old Quebec pilot friend, is to have the primer ready with a charge as you start cranking and slowly feed in the extra fuel to enrich the mixture until the engine catches. Here in Vancouver it's usually not cold enough to worry about that. Still, your theory, BH, that a choke (or my friend's primer technique) might have fixed the problem seems to be the most likely cause.

That would mean that the engine died because it was too cold and not enough fuel was atomizing. The dying engine would account for the drop in fuel pressure. One piece of evidence that doesn't fit the cold engine scenario is my pal's claim that he switched on the boost pump when the engine died and that seems to have fixed the problem. More fuel pressure from the boost pump shouldn't cause more fuel to enter the carb. If anyone can explain how that is possible then maybe I have my explanation.

So far looks like this post was prompted by a dose of paranoia.

[OntheNumbers]

For the record, image of the fuel pump and carb intake. with signs of blue dye. I think this is normal.

Fuel Pump Dye.JPG (153.69 KiB) Viewed 4880 times

ScheblerIntakeDye.JPG (175.67 KiB) Viewed 4880 times

[hoptwoit]

The blue stain at your carb is most likely from the accelerator pump (moving the throttle with the engine off will produce a spray of fuel each time the throttle is advanced when the engine is running it us sucked into the engine and burnt. When it is not running the fuel runs out of thee carb and into the airbox). This is considered normal. Bad practice but normal. The blue staining around the fuel pump is not normal. There should be no fuel seeping in the area of the rubber diaphragms. Check the outlet of the small 1/4 inch ridged line in the right of the picture. there should be no fuel or staining from it. If there is then your diaphragm is torn. I have seen these styles of pump lose pieces of rubber down the outlet lines yet still work. 4 psi is the low side of spec. I seem to remember 4 to 6 psi. but it depends on the application. See if you can find out how old the pump is my bet its fairly old 10 years plus. The diaphragms get brittle with age and the pumps are cheap to replace considering what they do.
Once the engine is started don't use the primer to add fuel. If you must give the throttle a quick pump or two but only if the engine is turning. This will avoid the raw fuel dripping out of the carb and into the cowl.

[Colonel Sanders]

The blue staining around the fuel pump is not normal.

+1

If it were mine, I would change it / rebuild it.

IIRC there was an AD against those fuel pumps a few years
back. Was it applicable against yours?

http://wwwapps3.tc.gc.ca/Saf-Sec-Sur/2/ ... -23-03.htm

Also a laundry list of SB's ... here are just a couple:

http://www.lycoming.com/Portals/0/techp ... cement.pdf

http://www.lycoming.com/Portals/0/techp ... cement.pdf

Remember that YOU - not your mechanic - are responsible
for AD compliance. You must also be aware of the applicable
MSB's, SB's, SL's, SI's, etc which may or may not have a
corresponding AD.

This is very different than in the USA where an A&P/IA is
required to verify that all AD's are complied with, to sign
off an annual inspection. There is NO SUCH REQUIREMENT
in Canada. It is NOT your AME's job to worry about AD's,
etc - it is yours.

It has been my experience that very few owners in Canada
fully comprehend this tiny detail.

[Colonel Sanders]

PS Looking at your picture of your engine-driven fuel
pump above, I am willing to bet $10 that the screws
on the bottom are loose and need to be re-torqued.

Read this:

http://www.ntsb.gov/aviationquery/brief ... 041&akey=1

an in-flight fire erupted in the left engine nacelle while on approach...

The engine examination disclosed that the area which exhibited the most fire damage was behind the engine driven fuel pump. The fuel pump was attached to the test stand's fuel supply and pressurized. The fuel pump began leaking at 8 pounds pressure per square inch (psi). The leak was coming from the area where the relief valve cover mated with the fuel pump body. The fuel pump was removed, and the safety retaining wires securing the screws on top of the relief valve cover were inspected. The safety wiring was intact. The safety wires were removed, and the screws were found to be only finger tight. The screws were replaced and torqued to the recommended torque value of 25 inch pounds. The pump was pressurized to 20 psi (the maximum available at the test stand), and no leaks were observed.

I would not fly your aircraft any more.

Take your time and carefully clean the fuel pump,
ensuring that you remove all 100LL blue dye using
a toothbrush and your favorite solvent.

Remove the lock wiring from the screws on the
bottom and re-torque them and lock wire them.

Also, take a close look at the fitting in the center
of the picture. Is it leaking? Did someone over
torque it and crack the housing?

Run the engine again on the ground and check
for leaks. If you see more blue dye on the pump
housing, or any fluid venting, or any abnormal
pressure indications, time to dig deeper.

[cgzro]

I would not fly your aircraft any more.

Agreed, that line of blue die on each side of the output fitting is very troubling. If somebody overtorqued the fitting it would crack like that on each side.

Dont fly like that!