Engine won't start after oil change

[Stewartb]

Another thing to consider, the 390 uses 20° advance instead of the more common 25°, but mag timing shouldn’t be messed with during a normal oil change.

 

[Ed Haywood]

Could be he fiddled with the fuel settings and it's causing your starting procedure to be less than optimal. Experiment a bit with the duration of your prime and how far you open the throttle when starting. For a long time I thought I was flooding my IO-360 when I actually wasn't priming it long enough.

 

[midwestpa24]

I really doubt the fresh oil has anything to do with it. But I'm assuming like most aircraft the cowl had to come off to do the oil change. Go back step by step through that process, every screw that had to come out, every wire that had to be disconnected, air intake, etc. Possibly somewhere in that process something else was bumped, blocked, shorted, or disconnected. Could be as simple as a rag blocking an air intake.

 

[Dan Thomas]

Engine wouldn't start. He drained the oil and went back without the Camguard and it started fine.
Apparently the mix was too slippery for the starter adapter, or at least that's what he said.

Smaller Continentals use a slip-clutch in the starter Bendix. That gear is engaged all the time and spins with the crankshaft, and the clutch lets it do so without wear. But as the clutch wears a bit from normal starting, it develops flat spots on the engagement dogs that spread out the pressure on them, and slipperier lubes won't let them grab the shiny shaft they need to so as to turn the crankshaft.

I'd start with timing, impulse coupler and spark plug wire connections at mag and plugs. That all assumes it's spark related.

If it started at all, that stuff is all probably OK.

Run up ok makes impulse coupling more likely, but my money is still on a mag getting bumped and shifting

If the mag was shifted, the runup would NOT be ok.

WAG is mag was bumped out of timing some how.

Guessing is no way to repair an airplane.

Could be as simple as a rag blocking an air intake.

It would not have started at all.
_______________________

P-leads have been known to get worn and fray, and the shield wires contact the core wires and short the mag. Their terminals at the mags have been known to get bent and short out on the mag housing. Mechanics have been known to disconnect P-leads to make filter access easier (or even possible), and if they get the leads crossed and reconnected to the wrong mags, the switch shorts the impulse mag and the occasional weak spark from the other mag then has to fire the engine, and it doesn't do that well at all. Once the engine starts, the misconnected leads will not affect the runup.

The P-leads are the most vulnerable things back there near the filter. They need checking first, and their proper connections confirmed.

Very often problems like this are due to extremely simple stuff, yet everyone goes chasing ideas much farther from being likely. Based on guesses, most of it. I can see this one ending up with a new injection servo, a new starter, a new battery, new cables and contactors, new ignition switch, and lastly, two new mags, at which point the shorted P-lead will be noticed, finally, and fixed with a dollar's worth of parts and ten minutes of labor.

God gave us education in aircraft maintenance and repair, wiring diagrams, and tools like multimeters and mag timers to help find the gremlins. Guessing is expensive and unproductive.

 

[Bell206]

After 24 hours on engine I asked mechanic to drain the oil and he refilled with AEROSHELL 100 SAE 50 MINERAL OIL and camguard, 1.6 oz per quart.

Tried to cold start the plane following same instructions as the last 34 months and it failed.

So on the 1st start immediately after the oil change it did not start? Or was there a leak check ground run in between your attempt and the oil change?

And every failed started flooded the engine as evidenced by fuel dripping out?

 

[Stewartb]

My 390 drips some fuel through the sniffel valve pretty much every time I prime it. That's not an indicator of flooding.

 

[Magman]

If it consistently cranks but does not light off the culprit may be

left magneto internal “ e-gap”. The Cam for the Contacts wears and causes

the point. to open later. This gives a weaker spark and retards timing to

the engine. Often checking for spark at leads is good and run up ok if it

starts.

 

[hindsight2020]

Guessing is expensive and unproductive.

Yah well, so is "credentialed" people learning at your own expense, literally. Tis' a two way street, just ask @Jim K . Now if you're saying extend the EAB mx regulatory largesse onto spam can world in support of your thesis, then I'm with ya.

 

[JOhnH]

God gave us education in aircraft maintenance and repair, wiring diagrams, and tools like multimeters and mag timers to help find the gremlins. Guessing is expensive and unproductive.

Surely you are not suggesting that we should not ask questions and share thoughts?
If that's the case, then we might as well shutdown POA and almost every other aviation board I visit.

Just on this thread alone I learned a few things. That learning cost me nothing.

And besides, FPK1 said:

Hope to get on the mechanic schedule for this week, any ideas?

So what's your beef with asking questions and offering opinions. It's not like we are telling him to pour jello in the crankcase and go fly.

 

[Daleandee]

Guessing is expensive and unproductive.

A slight clarification if I may ... guessing is free and the cost of repairs could be minimal, if the first guess is correct. The cost comes from implementing guesses that are completely wrong over and over ...

 

[FPK1]

So on the 1st start immediately after the oil change it did not start? Or was there a leak check ground run in between your attempt and the oil change?

And every failed started flooded the engine as evidenced by fuel dripping out?

Immediately after the oil change it did not start following normal start procedures for a cold start. No leak test ground run prior. My mechanic helped me start it making adjustments to mixture and throttle. No fuel came out.

Next three subsequent normal cold start attempts failed and I noticed fuel on the ground so I tried flooded starts. First two worked, the last one I finally gave up...

 

[Ed Haywood]

IMO a lot of "flooded" engines are actually fuel starved. I finally got frustrated and read the Lycoming guidance for my IO-360. Once I understood the process better, I almost always get a cold start on the 2nd or 3rd blade. I also learned why turning it over for more than a few seconds is pointless.

 

[FPK1]

For 34 months I've had no problems starting the engine. I follow the cold start instructions in the POH with slight modification. It says to open the mixture control for 3-5 seconds but I had to open it for about 6 seconds as that was the sweet spot for my engine.

The engine came back after Lycoming warranty work and no issues. Again, follow the POH with my slight modification and everything worked fine.

24 hours later I have my mechanic change the oil and now the plane won't start. Extra fuel extra throttle finally got it started. Next three times my normal procedure failed. I tried extra fuel and extra throttle until excess fuel came out onto the ground. I then tried a flooded start and was able to start the engine twice but the third time it just did not want to start so I aborted and here we are today.

I'm a new airplane owner and appreciate the input above. I have learned a lot from some of your posts. Tomorrow morning I meet with the mechanic and I try to start in his presence, and we go from there with several things to check as you have suggested above. I'll certainly let you know what happens ;-)

 

[Dana]

A weak spark can often make starting very difficult, but then it seems to run OK once it does start. If a spark plug wire was stressed to the point where it's sorta sometimes making contact, that could explain it. Or a partial / high resistance short in the P-lead.

Was the airplane parked outside in the rain while waiting for the mechanic to work on it? Wet wiring, water in the fuel...

 

[Skip Miller]

The "starter adapter"?? "Too slippery"??

????

Yes that is a known problem. I’ve heard of that before. Could you hear the starter motor cranking? Did the prop rotate? This occurs when oil that is too slippery is used with an adapter prone to slipping. It only occurs with certain brands of starters and adapters, and oils. Your A&P should know this.

-Skip

 

[Hang 4]

God gave us education in aircraft maintenance and repair, wiring diagrams, and tools like multimeters and mag timers to help find the gremlins. Guessing is expensive and unproductive.

Dan, I respect your ability a lot. Having said that, no one suggested the parts cannon, and for darn sure it's not the oil itself. OP was suggesting draining perfectly good oil to "fix" it. Hopefully he's off that ledge. Most obvious explanation is something got disturbed during oil change. It would be a heck of a coincidence if it was not that. So, what's in the area of the filter on a Lycoming? Mags, P-leads (as you suggested), plug wires etc.
Only other thing I suggested was the OP ask if anything was done besides the oil change? That might be another clue.

 

[Hang 4]

Yes that is a known problem. I’ve heard of that before. Could you hear the starter motor cranking? Did the prop rotate? This occurs when oil that is too slippery is used with an adapter prone to slipping. It only occurs with certain brands of starters and adapters, and oils. Your A&P should know this.

-Skip

Only an Continental issue, OP has Lycoming

 

[FPK1]

A weak spark can often make starting very difficult, but then it seems to run OK once it does start. If a spark plug wire was stressed to the point where it's sorta sometimes making contact, that could explain it. Or a partial / high resistance short in the P-lead.

Was the airplane parked outside in the rain while waiting for the mechanic to work on it? Wet wiring, water in the fuel...

Always indoor and the annual did include new spark plugs which he plans to check tomorrow...

 

[FPK1]

Only an Continental issue, OP has Lycoming

Motor was cranking and propeller was spinning... Yes Lycoming, good. Thank you.

 

[bonefishpete]

In for the cause. Also I've had my share of A&P that guessed at problems. Sometimes they were right sometimes not.

 

[NoHeat]

Engine cranks just fine, just never fires up...

Motor was cranking and propeller was spinning.

So all it needs is combustion, which requires three things: fuel, air, spark. (Oil has nothing to do with it.)

It's not getting one of those three things, so process of elimination:
- Air is an unlikely issue on the ground (unlike flight, with induction icing).
- Fuel is getting to the engine when you were able to flood it.
- So that makes it sound like spark. Which has been much mentioned here: mags, wires, plugs. Sounds like maintenance-induced failure, with at least one of those.

 

[FPK1]

- So that makes it sound like spark. Which has been much mentioned here: mags, wires, plugs. Sounds like maintenance-induced failure, with at least one of those.

I can't help but wonder when the mechanic's student reached up into the engine compartment area to attach the drain hose and open the oil drain valve, he may have grabbed something else by mistake first... This was prior to the cowling coming off.

But I did have a successful warm start! So why just cold start issue...?

 

[AV8R_87]

But I did have a successful warm start! So why just cold start issue...?

As a few of us mentioned, you probably have a weak spark. Through P-lead damage, contamination or something else, some of the spark energy gets shorted to ground. A cold engine will need a stronger spark to start.

 

[FPK1]

As a few of us mentioned, you probay have a weak spark. Through P-lead damage, contamination or something else, some of the spark energy gets shorted to ground. A cold engine will need a stronger spark to start.

Thank you, I didn't know a cold start needs a stronger spark...

 

[Magman]

Spark alone is not enough.

You must spark occur at the correct time to be effective.

Note I’m not talking of mag/ engine timing.The concern is where the piston

is when the impulse coupling is triggered. This normally takes place with

the piston at Top Dead Center. If the impulse is firing past that point many

engines will crank and crank but not start. While the Impulse Coupling is not

adjustable the procedure of adjusting e-gap synchronizes the components.

Note the comment that this engine is timed to fire at 20 degrees unlike

most Lyc’s that fire at 20. When the Starter spins the engine it further

retards the “ Cranking Timing” ( my term). Lycoming has a chart that

illustrates the effect.


By advancing the timing about 5 degrees ( GROUND TEST-LOW POWER ONLY)

you may find the the engine starts better. If so; remove the mag and have

the e-gap adjusted. When done; reinstall with engine spec timing.


Component wear and “drift” is addressed at the 500 Hour Service.

Some mags need it earlier.

 

[Ed Haywood]

Fuel and air are also not enough. They must be in a mixture that supports combustion. Too rich or too lean and ignition will not occur. This is why priming and starting procedure matters.

 

[Dana]

While the Impulse Coupling is not

adjustable the procedure of adjusting e-gap synchronizes the components.

e-gap has nothing to do with the impulse coupling's timing; it synchronizes the rotation of the rotor magnets past the coil to the points opening. Nothing a mechanic would do during an oil change would affect that.

There's a long list of things that could cause an engine not to start, but there's a shorter list of things that might have been caused a mechanic mucking about the outside of the engine during an oil change. There's also a shorter list of things that would make the engine hard to start but let it run fine afterwards. The problem is probably in the intersection of those short lists.

 

[Magman]

And the IC just happens to be fastened to the end of the rotor magnets.

In 300 hrs the the Contact Cam wears and retards the magneto e-gap

which in turn produces as less powerful spark. The mag/ engine timing

can be reset but the IC cannot and will be triggered late.


IMHO I don’t think the oil change has anything to do with the issue.

My opinion is based on the OP’s description of crank and crank and no start.

Improper lube of the Contact Cam would cause premature wear and upset

the internal timing. There are mags that don’t go 500 before having a

problem. I think this one just picked it’s time.


If all plug leads are removed and found to have good spark you can check

when the IC triggers and causes “ starting spark” by observing the timing

marks on the Support ( flywheel ) as the click occurs. Past TDC =

hard starting. Early 152’s had a lot of hard starting problems. Crank and

crank and no start. Hand propping and it comes to life. This was addressed

by changing the IC Lag Angle to provide less retard and starting improved.

A slow speed Starter also helped.

 

[Capt. Geoffrey Thorpe]

This was prior to the cowling coming off.

But I did have a successful warm start! So why just cold start issue...?

Cowl came off because?

(I am not an A&P, but I have been spinning wrenches for over 50 years and spent more than 30 years working on automotive powertrain controls and diagnostics - from carburetors to direct injection - so, FWIW...)

Cold starts are harder than warm starts - harder to ignite the mixture because there is less fuel evaporation. Wimpy spark tends to show up during cold starts.

The type of oil is irrelevant WRT the issue at hand. Issue is most likely air/fuel mix or spark.

The fact that the problem turned up at the oil change may be due to something getting finger poked, or could be just coincidence. That may seem unlikely, but it wouldn't be the first time.

Mags have points and rubbing blocks inside that wear. Condensers can also go bad. Those all can effect the timing and how hot the spark can be.

Just under 300 hours on the engine.

I wouldn't usually expect the mags to wear out in 300 hours, but it's not like they are fresh and I suspect that they have not been looked at.

I follow the cold start instructions in the POH with slight modification. It says to open the mixture control for 3-5 seconds but I had to open it for about 6 seconds as that was the sweet spot for my engine.

So, you had a pre-existing starting problem that required extra fuel to cover it up?

 

[Bell206]

My mechanic helped me start it making adjustments to mixture and throttle.

So, the engine was starting normally up to the recent oil change and on the subsequent 1st start attempt it did not start using your normal procedure?

And to correct that issue, your mechanic adjusted the mixture and throttle until it started? Was this using your normal start procedure?

So as it stands, the carb adjustments are different than prior to the oil change?

 

[FPK1]

So, the engine was starting normally up to the recent oil change and on the subsequent 1st start attempt it did not start using your normal procedure?

And to correct that issue, your mechanic adjusted the mixture and throttle until it started? Was this using your normal start procedure?

So as it stands, the carb adjustments are different than prior to the oil change?

He adjusted the controls inside the cockpit, kind of a modified flooded start... Settings unchanged into the cowling.

 

[FPK1]

Cowl came off because?



So, you had a pre-existing starting problem that required extra fuel to cover it up?

Replace the oil filter...

Yes, maybe 30 months ago. The plane just seemed to start better with a little more fuel... So I added mixture open one additional second.

 

[Bell206]

He adjusted the controls inside the cockpit, kind of a modified flooded start... Settings unchanged into the cowling.

You may want to revisit those cockpit adjustments. In general, the cockpit controls are adjusted to give proper movement of the carb levers and stops, and secondly, to ensure full control cable movement to achieve/maintain those carb lever/stop settings.

 

[Dan Thomas]

Early 152’s had a lot of hard starting problems. Crank and

crank and no start. Hand propping and it comes to life. This was addressed

by changing the IC Lag Angle to provide less retard and starting improved.

A slow speed Starter also helped.

The O-235 is used in the 152 and a bunch of other airplanes, and it has always had a reputation of being hard to start. Many, if not most, have two impulse mags on them because of that.

Yes, the e-gap might be off, and it might be the reason the OP has been using more than recommended prime to get it going. The cold-start failures after the oil change might be a coincidence and might not. I don't remember seeing anywhere which mags are on the OP's engine, Bendix or Slick, and whether they were new or overhauled, but as you say there is no guarantee that any "new" mag will go 500 hours before acting up. Slick, especially, has had QC issues for years, and field overhaulers often mess things up, too. Just a bit too much grease on the cam can foul the points. Using a feeler gauge on the points instead of the proper e-gap setting tool on the rotor will result in less-than-ideal spark. Slick's manual mentions points gap. They should not have done that. Some will use that number instead of the proper rotor positioning gauge. From the manual:



The .008-.010" is with the points at max opening, not at e-gap, of course.

 

[FPK1]

I cannot thank you all enough for your responses. I bought this airplane brand new in 2022 and before that all I did was rent airplanes. I really don't know much about maintaining them, or engines, etc, I'm more of a electrical, Heath kit kind of guy I have learned much from your responses above.

This morning the mechanic opened the cowling checked the spark plugs which were fine. He then checked the timing and it was a perfect 20°. And then replaced the cowling and we gave it a shot.

It appears my problem was user error. My mechanic noticed I was opening the mixture for too long. This morning, while watching me, he suggested I close the mixture as soon as the fuel flow peaks. POH says 3-5 seconds I was doing 6, now he recommends peak fuel flow. I tried peak fuel flow and the engine immediately started!

Hopefully this is not a case of taking your car into the shop to show them a problem and only then does it work. I'll try it again tomorrow morning without my mechanic at my side...

 

[Magman]

There have been several suggestions for OP to pursue.

In #66 I described a technique regarding mags.

Another technique I’ve used is:

Prime engine.

FULL Throttle

Ignition in start position

Crank engine. If no start after a few seconds slowly move throttle

towards closed while continued cranking.

When the engine fires IMMEDIATELY retard the throttle.

The rpm should not exceed that of a normal start.

In full open you are providing lots of air to the engine.

As you close the throttle you are reducing airflow and effectively

RICHENING ( edit) the mixture. If you suspect flooding repeat with mixture ICO

but you ready to richen if it starts.

If you are unsure as to what IMMEDIATELY entails my suggestion is

do not do it.

 

[Magman]

Glad all is well.

Didn’t see #75 till after posting.

 

[NoHeat]

Glad you found the problem.

It would be so much easier if our fuel systems were more like those of our cars - without the mixture knob, prime, and boost.

 

[Ed Haywood]

Glad you sorted it out. I kinda figured it was a technique issue. These engines can be a bit finicky to start, as all the suggestions illustrate. Sounds like you have a good A&P.

 

[Dan Thomas]

It would be so much easier if our fuel systems were more like those of our cars - without the mixture knob, prime, and boost.

https://www.lycoming.com/engines/ie2

https://www.aviationconsumer.com/uncategorized/lycoming-ie2-incremental-technology/

Available for 15 years or so already. Why isn't it in new Cessnas? Cost, probably. The airplanes are already too expensive. But Tecnam is using it in their new airplanes:

https://www.flyingmag.com/tecnam-makes-progress-on-p2012-traveller-program/