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Engine problems

J

Jim garrett

Member
I just completed my RV-12 and have 14 hours on it. I have the skyview touch installed. Everything is normal on first flight but after landing and shutting down for up to 30 minutes, the engine is hard to restart but it will start after running the starter more than it should. I realize this is vaper lock. The real danger however is when I go to take off. About halfway down the runway ( short runway) the skyview indicates a warning about fuel and the indicator (amount of fuel) turns red and indicates around 11 gallons per hour. I also sometimes smell a gas smell. It then settles down to the normal 6 to 7 gallons per hr and everything is normal about the end of the runway. I noticed only one time -- with top cowl off and aux pump on that fuel was coming out the plastic overflow tube with engine turned off. I took carb off and noticed that float was sticking the first time I moved it. I also checked the valve that the foot shuts off when full and it was clean.
Has any one had this happen to them and any thoughts on how to repair
 
I live in Southern Arizona and see similar issues when restarting the engine in the summer after sitting on the hot tarmac for any length of time.
What I do to help it a little is to run the electric fuel pump for half a minute before restarting the engine (I added a switch for my electric pump). Do not use any choke on restart, play with the throttle a bit if needed to get it fired up. It usually runs a bit faintly when it comes up and I let it run until I feel that it runs as usual before doing anything else to it. Once it's running I have not seen any delayed vapor issues, like high fuel flow.
Your fuel smell indicates that there is something else but vapor lock going on. It should be a problem with the floats in your carbs as you had already seen. You might want to clean hem out thoroughly and also check that the spring valve in there is working ok.
 
Hey (former) neighbor - welcome to VAF!! Glad to hear you have the -12 flying.

So Polly hasn't gotten any longer, huh? ;)
 
Jim garrett said:
I noticed only one time -- with top cowl off and aux pump on that fuel was coming out the plastic overflow tube with engine turned off.
Click to expand...

Fuel exiting the vent tube could be caused by debris preventing the needle valve from fully closing, floats sticking (as you thought you saw already), or sinking floats (have you inspected the floats in accordance with the recent S.B.?)

Fuel being vented would also align with a higher fuel flow indication.

I would say that high fuel flow, along with fuel smell some of the time, is a strong indicator that you are venting fuel... something that you should definitely get resolved.
 
Just to add what others have already said, there is also a recall on some of the fuel pressure sending units. Check on the Dynon web site for the particulars. This is just to make sure you are getting an accurate fuel pressure reading.
 
Well , the same thing happened to us today. Returning to KCLW, we had to divert to X39 because the runway was closed. It was mid-afternoon and hot. We waited an hour, got the all clear, jumped in the airplane and took off. A run up would have helped. Anyway the engine quit right after applying full power and we had a strong gas smell. We got off the runway, checked everything, did a full run up, everything was still green, and took off. We climbed out ok. The engine ran a little rough at 5000 rpm but as soon as we went up to 5400 rpm, everything smoothed out. We did not have any problems in the pattern, throttling back was smooth and the engine was smooth during taxi at low rpm, with no fuel smell. So, vapor lock or the start of a float problem, or maybe both. The float checks have been fine so far. We have 85 hours on the plane.
 
A couple of further points - a lot has been made about using winter formulation auto gas when the temps warm up....

(see http://www.vansairforce.com/community/showpost.php?p=545927&postcount=19)...amongst others....

(older article, but interesting none the less...)

http://www.eia.gov/todayinenergy/detail.cfm?id=11031

Also I was draining my tank thru the gascolator and noticed low flow - there was some debris on the gascolator screen (I mean how many times have I had to tear apart that tank now...despite my best efforts at cleaning up everything multiple times with everything from a microvac to duct tape). So cleaned the screen and re-wired the gascolator and the flow improved substantially...food for thought.
 
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cactuspilot said:
So cleaned the screen and re-wired the gascolator and the flow improved substantially...food for thought.
Click to expand...

I know this will sound like a dumb question, but how do you clean a gascolator screen? I checked mine recently and luckily it looked fine, but I couldn't see any easy way to remove it for cleaning - assuming you're supposed to remove it that is, or is there some other trick to it?
 
I couldn't figure out an easy way to remove the screen without compromising it's sealing function, so I ordered a few extra screens from Van's and just replace it with a new one if needed.
 
rgmwa said:
I know this will sound like a dumb question, but how do you clean a gascolator screen? I checked mine recently and luckily it looked fine, but I couldn't see any easy way to remove it for cleaning - assuming you're supposed to remove it that is, or is there some other trick to it?
Click to expand...

I just use a small screw driver to carefully pry out the screen, rinse it out, let it dry out and inspect it and replace it.
 
Thanks guys,
My first thought was to prise it out with a screwdriver, but that looked like a good way to damage it so I left it alone. I might order a couple of spares anyway, so I have a choice of replacing or re-placing.
 
I have had luck - -

putting a finger on it lightly near the outer edge, and slightly spin it. Seems to start it moving down. Has worked so far anyway.
 
Someone asked if my engine problem has been resolved, yes and no. I have not had the high fuel flow problem like before but lately have had low fuel pressure announcement right at lift off. Pressure goes down to aBout 2 .5 PSI briefly then goes back up to 4 to 5 PSI. Stays that pressure for rest of flight. I have checked all hoses for any leaks- none, noticed I have pressure from aux pump without engine running and have pressure with engine running without aux pump on. Usually around 4 psi. I now have 21 hours on aircraft.
Some of the other troublemaker I have encountered are:
1: No OAT indication and no wind direction or velocity-- found the 1 OAT wire pin backed out of the black small plastic cannon-plug. Was able to reset it

2: the right EGT UNIT ( inserted in the exhaust) was defective and gave very high readings in flight- red indication at cruise settings. Normal when throttled back in traffic pattern. Dynon is replacing. ( I switched wires with other one and problem followed it.
 
Jim garrett said:
Someone asked if my engine problem has been resolved, yes and no. I have not had the high fuel flow problem like before but lately have had low fuel pressure announcement right at lift off. Pressure goes down to aBout 2 .5 PSI briefly then goes back up to 4 to 5 PSI. Stays that pressure for rest of flight. I have checked all hoses for any leaks- none, noticed I have pressure from aux pump without engine running and have pressure with engine running without aux pump on. Usually around 4 psi. I now have 21 hours on aircraft.
Some of the other troublemaker I have encountered are:
1: No OAT indication and no wind direction or velocity-- found the 1 OAT wire pin backed out of the black small plastic cannon-plug. Was able to reset it

2: the right EGT UNIT ( inserted in the exhaust) was defective and gave very high readings in flight- red indication at cruise settings. Normal when throttled back in traffic pattern. Dynon is replacing. ( I switched wires with other one and problem followed it.
Click to expand...

There is a recall on some of the fuel sensors:

http://www.dynonavionics.com/docs/support_bulletin_120414.html

Mine was not in the date range covered by the recall (slightly before) but I removed the purple gasket anyway and the problem went away. In my case the fuel pressure was fine until the tank was around 1/2 full and had been flying for a while and then I would notice a drop to around 2 psi - engine ran fine however.
 
where is the OAT cannon-plug

John,

I have the same OAT--- on my Skyview. Where is the cannon-plug you found the issue on (at the ADHARS or.....?)?
 
Fuel problems can be a real pain. What finally solved mine, was finding the jet in the fuel return line - here's a picture of it sitting on top of the engine:

330cl7m.jpg


nyff9i.jpg


It is easy to get to, and, a little carb cleaner and a blast of air will clean out the jet.
 
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