Fuel Diverter.

[Scottishflyer182]

Hi All,

I had planned to go flying today. However I could not get my engine started. I have a 2007 C182. Usually when the fuel pump is activated for the usually 8 secs a fairly large fuel flow is show. However, today this was much lower than usual. Too low to feed the carburetor with enough fuel to start.

This is the second time I've had this problem. The local engineers told me last time the fuel diverter had failed? Is this a common problem with fuel injected engines?

The local engineers can't look at this for at least a week, commercial aircraft get priority:ugh:

Is this something I could fix with the help of a FAA Engineer?:ok:

If the answer to the above is Yes and your an FAA Engineer or suitably qualified please IM me. (Perth area)

Thanks

SF

[SNS3Guppy]

Fuel flow divider, perhaps?

The fuel flow divider is the fuel spider at the top of your engine...a round metal object with each injector line going to the cylinders. It should have one inlet line, and one small injector line to each cylinder, and one overboard vent line. Inside the divider is a diaphram and a spring. If the diaphram ruptures, it leaks, and fuel should be found draining from the overboard port on the fuel flow divider, of from the drain line (if one's attached to it). If you don't have a drain line (you should...it's a fire hazard), you may see blue or green stains under the fuel flow divider...a sure sign of leakage.

Failure of the fuel flow divider diaphram can cause engine failure...on the ground, or in flight. If you're boosting it the engine isn't starting check for any discharge at all in drain line or port...if you see any fuel there at all, you have a problem and should not operate the aircraft.

[AC-DC]

Scottishflyer182

Your post is a bit confused. If you have a carburated engine you do not have a fuel flow gauge and the other thing is 'diverter', what is it?

From thefuel pump the fuel flows into the fuel servo which sometime is also called 'injector servo' or 'metering unit' and from there it continues towards the 'fuel distributer' or 'spider',I believe that you refer to this part.

Inside the Spider there is a valve that is attached to a Diaphragm loadedat the top by a spring. The fuel reachs to the underside of the Diaphragm and pushs it against the spring, the valve opensand fuel flows to the cylinder's injectors.

There can be 2 faults that willprevent the spider from fully open.
1. Bridged Diaphragm - The spider has to be opened and the part has to be replaced.
2. The air vent at the top (on the side) of the spider got blocked which prevents the Diaphragm and the valve from opening. In order to remove the blockage you need to push a wax wire into it, NEVER USE A LOCK WIRE as you will cut the Diaphragm.

Good luck

[fernytickles]

Before you go getting all technical, have you considered the ambient conditions? I keep reading about "arctic conditions" being reported in the UK yesterday. A noticable drop in temperature can make for a noticable increase in the amount of priming required to start the engine, whether primed by an electric fuel pump, or a manual primer. It can also make for an increased chance of an engine fire due to over priming, so lots of things to be cautious about.

Good luck, hope you get back in the air soon.

An add-on after reading smarthawke's post. I've found that a really good way to get to know my aeroplane was to be there when maintenance work was done, especially the annual. I'm am very fortunate to have a great engineer who encourages me to be there, infact grumbles if I'm not. I'm allowed to do the really hi-tech things like remove and replace the inspection panels (!), but am there to observe and learn while he does serious stuff. I'm still not comfortable doing even basic maintenance work on the plane on my own, but I feel I have a much better understanding of my aeroplane (tho' others may disagree....) and can, occasionally, describe any issue to him in quite technical detail...instead of "its making a funny noise".... :\

Books are great, but hands on experience can't be beat.

[smarthawke]

If it's a 2007 182 then it is fuel injected. I've known of other new Cessnas having (intermittent) starting problems related to fuel supply issues.

Two points:

1. Your aircraft is still within warranty if a 2007 model so to mess about with it will more than likely cause warranty issues.

2. If you intend putting your and other's little pink bodies in the aircraft for the purpose of flight and you don't know whether your aircraft is carburated or injected then may I respectfully suggest that you aren't the person to try and fix it. Best to leave it to a qualified engineer and if you aren't happy with the service you are receiving, best get in contact with another engineer.

[SNS3Guppy]

I keep reading about "arctic conditions" being reported in the UK yesterday. A noticable drop in temperature can make for a noticable increase in the amount of priming required to start the engine, whether primed by an electric fuel pump, or a manual primer. It can also make for an increased chance of an engine fire due to over priming, so lots of things to be cautious about.


Cold conditions may require additional prime for a good start, but shouldn't result in low fuel flow.

[fernytickles]

Thats true, Guppy.

I don't know how long Scottishflyer182 has had their aeroplane, but it has also been my experience that until you've lived with your aeroplane for a full year, in all the various climatic conditions which that year brings, everything is new - settings, indications etc. The aeroplane I had at home in Scotland took 6 primes and would start without fail in the warmer months. When the temps dropped to about 10'C, then it was 8 or 10 primes. When it was down to freezing and lower (in WI when we moved here), it was a case of 10 or 12 primes, and keep pumping the primer whilst pressing the starter (fire extinguisher at the ready). Lots of puffs of smoke and grumbling, then it would start, and run like a dream. But it was a round engine after all, so that was to be expected :}

[SNS3Guppy]

We used to put a 5 gallon bucket under the supercharger drain on the R2600's and pump untl there was a steady flow draining out of the supercharger before we cranked with mixtures at cutoff. Once it fired and began chugging, we'd watch for less and less smoke and as the speed increased and the roughness decreased, we'd bring it into operate off the mixture rather than a flooded supercharger.

You're quite correct that one must respect the character and changes that may takes place with a given engine's operation from one season to the next. In many cases, particularly in a light piston installation, resetting the idle mixture seasonally is a very good idea.

[Karl Bamforth]

Cessna have had some well documented problems with flow dividers.

We need to be very wary of what is apparently displayed on an instrument, they often measure one thing and display another.

Fuel flow instruments on older Cessna for instance do not measure fuel flow they measure fuel pressure and display it as fuel flow.

Most ppl would expect an excessive high fuel flow to show a leak, in fact in a cessna it shows a restriction, normally a blocked injector.

Equally (all esle equal, fuel on, mix open, pump running)a low fuel flow will often indicate a leak, either a damaged injector pipe or diaphragm.

[smarthawke]

Talked to my friendly Cessna maintainers today. Apparently a number of 'new' Cessnas have had intermittent problems with the flow divider. Precision Airmotive (the manufacturer) used some form of goo on the diaphragm shaft which rather than lubricates causes the opposite - it doesn't allow the diaphragm to lift to allow fuel through, hence no start.

[Scottishflyer182]

hi All,

Thanks for your help. I posted this thread in a bit of a hurry, I do know that my Fuel Injected engine does not have carburetter (not much more though) :p I was not sure where the fuel went from the Fuel Pump. I now know it goes to a Diverter. Thanks to you lot.

Talked to my friendly Cessna maintainers today. Apparently a number of 'new' Cessnas have had intermittent problems with the flow divider. Precision Airmotive (the manufacturer) used some form of goo on the diaphragm shaft which rather than lubricates causes the opposite - it doesn't allow the diaphragm to lift to allow fuel through, hence no start.

Thanks for above, :ok: I also spoke to my local Engineer and he described the same as above. The aircraft is still under warranty so I will be able to reclaim the cost's of fixing this. However if it is a recurring problem I will need to speak to Cessna.

Smarthawke, thanks for your assistance.:ok:

SF.

[smarthawke]

Pleasure! Hope you're back in the air soon.