MOONEY WOULDN'T START TODAY!!!

[N6784N]

so i had my oil changed today in my 1968 m20c ranger and when i got to the airport this morning i did a cold start and the plane started right up. btw it has a brand new battery. anyway once we were finished with the oil change i tried to start it and although the engine was turning over it would not start for anything. it seemed as though the spark plugs were fowled. i tried to warm start it first then tried to cold start. then thought maybe it was flooded and tried to start it with mixture out and throttle out. i finally let it sit for 30 minutes tried again to no avail. i had the mechanic try to start it then he killed the battery. so we take the cowl off and start charging the battery. the mechanics check the mixture cable, spark plugs, vibrator and some other stuff and didnt see anything that would prevent the plane from starting. finally i tried to start it again and it finally started!!!! we never did figure out what the problem was but when i was taxing back to my parking spot i noticed the ameter was showing a positive charge and i decided to taxi around and idle for awhile to let the battery charge. i did this for around 20 minutes but the charge never neutralized. has anybody else had this problem? and if so what was the cause??

[N6784N]

it shouldnt have been a hot start since it took 2 hours to change the oil and when i previously started it, i only had it running for 5 minutes. ive owned the plane for 8 months now and have always had a problem when i start it for the first time of the day but heck this was the second time.

[skyking]

I only have that problem if the plane is cold.

Before i got my hanger if it was below 35 degrees F i always had to pre heat or there was no way that plane would start.

[eaglebkh]

Even though mine is IO-360, some principles may be universal on 360's.  I usually have a tendancy to underprime during start-up, and have only overprimed a time or 2 in my 3 years of ownership, and those were only during hot starta.  It just seems cold natured and whenever it wouldn't start on the first attempt, more primer was usually the ticket.  Don't hesitate to feed a few more seconds of primer whenever it doesn't start.  You'll smell fuel if the egnine becomes flooded.

I didn't pre-heat on my last flight and it was about 32F outside - gave 10 seconds of primer on first attempt, then immediatley gave 3 more seconds, and then it started right up.  These birds can just be cold natured...

[Hank]

     My '70-C does that sometimes, but only when it's cold. If I run the oil pan heat for 30-45 minutes if the temps are around freezing, or 1 hr or so if in the 20's, I have few problems.

     Something I learned at the MAPA PPP is to run the electric fuel pump only until the fuel pressure maxes out, then turn if off. Next, push the mixture to rich, and pump the throttle several times [twice if temps are comfortable, 3-4 if cold, and 5 or 6 times if very far below freezing] and sit there for a minute while the fuel vaporizes before cranking. If all else fails, pull it into a heated hangar for 30-45 minutes while freshening the battery.

     If you want to recharge your battery without removing the top cowl, I find a half hour or so at 2400 or 2500 RPMs works really well, and I get to sightsee at the same time. There's no need for high power [20" or 21" should do the job], but you'll still cover a lot of ground. Practice some maneuvers, timed turns, do an approach or two, and the battery should be pretty well charged, assuming it starts in the first place.

     Again, this is only a problem in the winter, and bit me in my 4th month of ownership. Since then, I've only had two times it wouldn't crank--once when heat wasn't available, and last week when the temps were in the teens and the oil preheat had been plugged in overnight. Never did figure that one out, but charged the battery and it fired right up the next day. My coldest departure was 8F, with overnight oil preheat, and hand-turning the prop 3-4 revolutions immediately before boarding, and it cranked just fine.

     Good luck with yours. Sometimes it's a challenge to find enough cockpit duties to kill 60 seconds between pumping throttle and cranking. Winding and setting the clock just doesn't take long enough. Sometimes I just wish it had a priming function!

                                 --Hank

[N6784N]

yea hank that makes sense on the best way to start it. its a little harder to just take off and charge the battery since im in maryland i have to jump through hoops just to take off due to the tfr and frz here.

[N207LS]

I echo Hank's starting advice from MAPA...  My G (O-360) has only been in cold weather a few times.  Being based in Florida we rarely have to think about cold start procedures, but a couple of weeks ago it was in the 40's here and the cold start procedure was essential.  As far as hot starts go, I have not had any issue as long as you do not leave the fuel pump on and do not pump the throttle. 

On the other hand, your symptoms sound like a possible voltage regulator issue (given that the ammeter never went back to zero).  Take a look at your aircraft log book and see how old your voltage regulator is.  When I had a similar issue I found out that it was my voltage regulator.  With a little detective work in the log books, I also found out that it had never been changed and it was original to 1968.  I guess that you can't complain about a electrical part that is 35 years old and finally breaks.  It's a fairly cheap part from Aircraft Spruce and takes just a few minutes to change. 

Aaron

[Guest Anonymous]

One thing you did not mention in the list of things your mechanic checked.  Did he verify that the primer pump in the carburator was working?

On O-360s, the prime does not come from the electric fuel pump,  The electric pump is used only to fill the carburator fuel reservoir.  The actual prime takes place at the end of the throttle stroke when you firewall the throttle.  Pumping the throttle all the way in causes a small plunger type pump in the carburator to shoot a jet of fuel upward into the manifold.  Each time the throttle is pumped, another measured amount of fuel is pumped up.  If the seal in the primer pump fails, the carburator will not shoot the prime upward.  In hot weater, a failure may not be detected if a partial prime is sufficient to provide the air/fuel mix required with the several strokes used or if the suction caused by cranking is sufficient to move vaporized fuel into the manifold.  In cold weater without a preheated engine and with a failed, or partially failed seal or blocked jet on the primer pump, no amount of throttle pumping will get the engine to fire.  The primer fuel is all sitting unvaporized in the carburator and not in the manifold.

RFB