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Engine tough to start after annual

J

josh937

Member
I have a RV7A with a carbureted o-360 with about 500 hours on it. I am the second owner and it has been a dream aircraft for the past 18 months- no issues at all UNTIL my annual finished last month. After my annual the engine really struggles to get started, and there has been a few time I had to give up and fly another day (and I tried to fly to see the northern lights last night but it wouldn't start, which has brought me here today).

Here are some observations I have noticed that are different- I won't draw the conclusions if any or all of them matter:
1. This was a big annual with a prop and mag overhauls, but I don't think that the problem...
2. My engine won't start. If it does start I have been using the flooded technique: mixture back and full throttle, then flip both once it fires. This happens even without using the boost pump or any movement of the throttle.
3. I can hear the *tapping* sound after I attempt to start like it is flooded. This is after the plane is just sitting for days/weeks. How could it be flooded after sitting???
4. The boost pump doesn't sound like it is pressurizing. It sounds the same for however long I run it.
5. The two times I couldn't get it started and walked away, the throttle didn't want to move and was locked in place after one or two priming pumps. It felt like a lot of pressure was keeping it in place. I could try to move it, but felt it would get harder the more I did. (And I know better than to use too much muscle to make it work when it's not right). Yet after it was started the throttle could move freely again- so I don't think it's a cable issue but the actual throttle sticking.
6. I have seen fuel dripping out of the fuel vents before I start the plane up-simply sitting on the ground, idle for days/weeks. It's spring in Ohio so it could be anywhere from 40-80F on a given day. If it's below 50 I usually preheat, but I have had the same issue at warm/ cold temps and preheated or not.
7.One odd thing about my annual was the A&P put WAY too much lubricant on the KN air filter, it was running down the front cowl for days. As a amateur when it comes to these engines, I wonder if some of that got injected into the carb and is causing some of this issues.
8. Once it's flying it has seemed normal. I even did the Savvy GAMI and mag check which came back with good results. It just feels like a starting issue.

I appreciate your help! Going from an extremely reliable machine, to one that won't start os frustrating.
 
Ask the mechanic if he made any adjustments to the carburetor. If no, then sounds like you need to double check the timing of the new magnetos as well as the wiring. The wiring is simple, but if it’s wrong and your impulse coupler isn’t working, you would have a difficult time starting the engine.

You do need to figure out why you are having trouble moving the throttle. Thats not a problem you want to deal with in the air.

Sounds like you also need to double check that your auxiliary pump is working. It sounds like it would be prudent to do a fuel flow test. A simple hose into a gas can with a stop watch will help determine how much fuel it’s pumping. Also check that it develops the correct fuel pressure.

Fuel out of the vents is normal if you keep the tanks full and the fuel warms up and expands, that doesn’t sound like it’s related to your starting problem.
 
Take it back to that A&P and ask him to demonstrate his starting technique, and if it doesn’t… get him to fix what ever he did to it. (Probably mag setup).

5. I’d consider the plane grounded till your stiff throttle cable issue is addressed.

4. Easy enough to diagnose if boost pump is pooched or not. (Or fuel supply restriction)
 
josh937 said:
I have a RV7A with a carbureted o-360 with about 500 hours on it. I am the second owner and it has been a dream aircraft for the past 18 months- no issues at all UNTIL my annual finished last month. After my annual the engine really struggles to get started, and there has been a few time I had to give up and fly another day (and I tried to fly to see the northern lights last night but it wouldn't start, which has brought me here today).

Here are some observations I have noticed that are different- I won't draw the conclusions if any or all of them matter:
1. This was a big annual with a prop and mag overhauls, but I don't think that the problem...
2. My engine won't start. If it does start I have been using the flooded technique: mixture back and full throttle, then flip both once it fires. This happens even without using the boost pump or any movement of the throttle.
3. I can hear the *tapping* sound after I attempt to start like it is flooded. This is after the plane is just sitting for days/weeks. How could it be flooded after sitting???
4. The boost pump doesn't sound like it is pressurizing. It sounds the same for however long I run it.
5. The two times I couldn't get it started and walked away, the throttle didn't want to move and was locked in place after one or two priming pumps. It felt like a lot of pressure was keeping it in place. I could try to move it, but felt it would get harder the more I did. (And I know better than to use too much muscle to make it work when it's not right). Yet after it was started the throttle could move freely again- so I don't think it's a cable issue but the actual throttle sticking.
6. I have seen fuel dripping out of the fuel vents before I start the plane up-simply sitting on the ground, idle for days/weeks. It's spring in Ohio so it could be anywhere from 40-80F on a given day. If it's below 50 I usually preheat, but I have had the same issue at warm/ cold temps and preheated or not.
7.One odd thing about my annual was the A&P put WAY too much lubricant on the KN air filter, it was running down the front cowl for days. As a amateur when it comes to these engines, I wonder if some of that got injected into the carb and is causing some of this issues.
8. Once it's flying it has seemed normal. I even did the Savvy GAMI and mag check which came back with good results. It just feels like a starting issue.

I appreciate your help! Going from an extremely reliable machine, to one that won't start os frustrating.
Click to expand...
Some things to ponder....
Fuel dripping from vents - I assume your referring to tank vents & as others pointed out likely normal if full tanks & warmer Wx
Fuel pump never sounds like pressurizing - so when 1st turned on thumping or bumping sound (tap tap?) quickly until pressure builds, then slows to very slow thump or bump sounds (tapping?) at full pressure - from your description possibly fuel is flowing freely somewhere... could be a stuck float allowing bowl to overfill & dump fuel overboard. Check for ANY signs of fuel dripping from carb or air cleaner box (need to remove cowling).
Throttle cable - sounds like an interference has been created, possibly where heim joint connects to carb throttle arm.... Look very carefully around where air filter attaches to carb entry.
Good Luck.
 
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Since it is a carbureted engine, if you are using the correct starting technique (pumping throttle only while cranking), you should never have to use a flooded engine technique because it shouldn’t never be able to get flooded.
Regardless, if it wasn’t like this before someone did your condition inspection, and now it is a solid issue, why isn’t the person that did that inspection involved in troubleshooting the issue they induced with their work?
You, an inexperienced owner, shouldn’t be wading through this on your own with just input from an Internet forum.
 
josh937 said:
My engine won't start.
Click to expand...
We need more specifics here….

first question in my mind is related to how the engine behave in the cranking cycle - does it spin with vigor, or is it labored? And is this new behavior?

second - when you flip on the boost pump prior to start attempt, does the pressure build and stabilize on the gauge? This indicates the float bowl in the carb has filled, the float has shut off the inlet, and the pump is pressurized against a closed valve to maximum pump pressure. If you have a cube type “rattle” pump, this will manifest in furious rattling as it fills the carb, a slowing as the valve closes and then stop, followed by the odd click now and then to replace pressure lost to internal leakage. it does not sound like this is happening at all in your description.

Also completely lost on the “tapping” sound you describe. Ive been around little airplanes my whole life and if there is a “tapping sound” that’s associated with a flooded condition I’m not aware of it. More description would be extremely helpful.

the frozen throttle movement is a total non starter. This is a hard grounding issue until resolved. This could be a million things, many very bad.
 
Tapping could be the impulse coupling as the motor was spinning without starting.

Sticking throttle, check throttle lock. And also see if the routing is close to the exhaust.

Join the nearest EAA chapter and learn about your RV.
 
As others have clearly said, please dig into these issues to make sure all is well. You need a good mechanic that you can trust who is comfortable with EAB aircraft. It's not a Cessna, and if the mechanic doesn't really understand this, then you could have serious issues. There are some excellent A&Ps on this forum that specialize in EAB, perhaps there is one near where you live. Another option to find a good A&P near you is check with the Savvy aviation guys. Good luck, and take care!
 
I think I would begin with the air filter. Not sure what he put on it, but it could be restricting air flow. I would remove the filter and try starting it. If that's the problem, get a new filter. If it still has issues, go back to the A&P for his input on what his did to the fuel system.
 
How about electric instead of fuel? New plugs at condition inspection? Not gapped correctly?
 
josh937 said:
I have a RV7A with a carbureted o-360 with about 500 hours on it. I am the second owner and it has been a dream aircraft for the past 18 months- no issues at all UNTIL my annual finished last month. After my annual the engine really struggles to get started, and there has been a few time I had to give up and fly another day (and I tried to fly to see the northern lights last night but it wouldn't start, which has brought me here today).

Here are some observations I have noticed that are different- I won't draw the conclusions if any or all of them matter:
1. This was a big annual with a prop and mag overhauls, but I don't think that the problem...
2. My engine won't start. If it does start I have been using the flooded technique: mixture back and full throttle, then flip both once it fires. This happens even without using the boost pump or any movement of the throttle.
3. I can hear the *tapping* sound after I attempt to start like it is flooded. This is after the plane is just sitting for days/weeks. How could it be flooded after sitting???
4. The boost pump doesn't sound like it is pressurizing. It sounds the same for however long I run it.
5. The two times I couldn't get it started and walked away, the throttle didn't want to move and was locked in place after one or two priming pumps. It felt like a lot of pressure was keeping it in place. I could try to move it, but felt it would get harder the more I did. (And I know better than to use too much muscle to make it work when it's not right). Yet after it was started the throttle could move freely again- so I don't think it's a cable issue but the actual throttle sticking.
6. I have seen fuel dripping out of the fuel vents before I start the plane up-simply sitting on the ground, idle for days/weeks. It's spring in Ohio so it could be anywhere from 40-80F on a given day. If it's below 50 I usually preheat, but I have had the same issue at warm/ cold temps and preheated or not.
7.One odd thing about my annual was the A&P put WAY too much lubricant on the KN air filter, it was running down the front cowl for days. As a amateur when it comes to these engines, I wonder if some of that got injected into the carb and is causing some of this issues.
8. Once it's flying it has seemed normal. I even did the Savvy GAMI and mag check which came back with good results. It just feels like a starting issue.

I appreciate your help! Going from an extremely reliable machine, to one that won't start os frustrating.
Click to expand...
In addition to the other comments, re: 7. …. Are you *sure* it’s filter oil coming off the K&N ? Could it be fuel ? Your other symptoms suggest the carb bowl could be leaking (or floats misaligned) which could manifest as fuel dripping onto the filter and out of the cowl. Beyond flooding the engine this is a fire risk in the event of a backfire and should be corrected immediately.
 
I appreciate everyone's comments. The a&p and I did some troubleshooting and right now signs are pointing towards the carburetor, but before sending it out, I'm going to let it simmer for a day or two to see if we have any new good ideas.
The stuck throttle line simply needed some cleaning and then it's back to moving very smoothly.
The boost pump was tested by taking off the fuel line and confirmed that we're getting fuel to the carburetor. The carburetor fuel screen was removed and was confirmed to be clean.
We checked the mag timing and it was good.
We also checked the Sparks and they were confirmed.

When attempting to start the engine, the prop spins well and it is not laborious. For the previous two years and roughly 200 hours it has always started right away and so this is a brand new issue.
There were many attempts made with the boost pump on without it starting. There are also attempts made with mixture Rich and standard throttle, with no starting. Then finally mixture out attempted a few times in a row is the only way I can get it to start. This is not a good starting procedure so I think I'll be forced to send the carburetor out to get inspected and or/fixed.

I'm open to any good ideas that could save me from sending it in, but right now I think that's where I am.
 
josh937 said:
I appreciate everyone's comments. The a&p and I did some troubleshooting and right now signs are pointing towards the carburetor, but before sending it out, I'm going to let it simmer for a day or two to see if we have any new good ideas.
The stuck throttle line simply needed some cleaning and then it's back to moving very smoothly.
The boost pump was tested by taking off the fuel line and confirmed that we're getting fuel to the carburetor. The carburetor fuel screen was removed and was confirmed to be clean.
We checked the mag timing and it was good.
We also checked the Sparks and they were confirmed.

When attempting to start the engine, the prop spins well and it is not laborious. For the previous two years and roughly 200 hours it has always started right away and so this is a brand new issue.
There were many attempts made with the boost pump on without it starting. There are also attempts made with mixture Rich and standard throttle, with no starting. Then finally mixture out attempted a few times in a row is the only way I can get it to start. This is not a good starting procedure so I think I'll be forced to send the carburetor out to get inspected and or/fixed.

I'm open to any good ideas that could save me from sending it in, but right now I think that's where I am.
Click to expand...
Huh................ Was this the same A&P that did the inspection? Not finding the sticking throttle cable during the inspection would concern me a little, among other things. Has he inspected EAB aircraft before, specifically RV-7s? I would be blunt with him and ask why it started so easily before and, since he worked on it, doesn't start like it did before he messed with it. To suspect the carburetor is reasonable, I suppose, but, again why would it 'suddenly' go bad? Did he do any adjusting to it? The suction of a O-360 would only be slightly annoyed by too much oil on an air filter. Did he use the RED oil that is specific for the K&N filter? Did he wash the filter before spraying it? How? How old is the filter? Did he use Proseal to seal the area around the accelerator pump housing (if that is done in your aircraft; some don't need that)? I would pull the air filter and take a look up the throat of the carburetor to make SURE the 'sticking throttle cable' is not something stopping the butterfly valve in the carburetor from moving.:oops: I suppose throttle cables can suddenly be sticky but..... New or overhauled mags (or installing after removal) need to be 'timed' before installation on the engine with a small pin that locks the mag temporarily in place in order to get it meshed with the drive gears correctly. If that was not done properly, that would likely show up in the timing. What was the timing? Both mags the same? It's 25 degrees BTDC in an O-320; not sure about an O-360. Some mechanics get fancy and time them differently than Lycoming specs. The timing should be marked on the engine data plate.

I agree: this should be a hard ground until this is figured out ON THE GROUND, not discovered in the air. Your mechanic needs to FIX whatever he messed with to cause this. And this should be on his nickel. :mad:
 
josh937 said:
Then finally mixture out attempted a few times in a row is the only way I can get it to start.
Click to expand...
This is a possible indication the engine is severely flooded during the start attempt.

so again, does the boost pump run, slow, and then stop once pressure builds? This is before any crank attempt. If the fuel pump continues to run after a few seconds, then that’s an immediate sign the float valve is not closing. If that’s the case, the bowl will overflow and cause a very rich condition on start. Left a little longer, fuel will out of the bowl and drip on the inside of the cowl, creating a substantial fire hazard.
 
My Facet cube will run full time if left on.... A better way to check stuck float is to watch fuel pressure as you turn on boost pump before start. Watch pressure build, when it peaks, shut off pump and watch for a pressure drop. It will drop slowly after several seconds. That is normal. If it drops right away, the float is stuck.
 
On my lightning with the bing carb, it just started flooding all by iself, no warning. Would not run properly (idle) then saw fuel pouring out the air filter onto the ramp. When I rebuilt it, there was no obvious damage to the needle or seat, nothing wrong with the float. Of course Arion wanted $450 for a carb rebuild kit. I was able to get one from a motorcycle shop for $200. After rebuilding it worked perfect again, go figure.
 
Still stumped....
My A&P and I double checked the mag timing, and it was still good. He pulled the mags and doubled checked them on a lathe- and they seem good.

Even though the carb wouldn't start unless I did the flooded procedure, it never actually flooded enough that fuel dripped out. I disengaged the fuel line to the carb, checked for flow with the boost pump, and checked the fuel strain into the carb. At that point we couldn't think of anything besides pull the carb. So we pulled the carb and it definately had fuel in it that leaked out once it was removed from the engine. So I sent it out, and we just heard back that it checks out fine- they didn't see any issues with it.......

We are stumped. Besides putting it all back together and hoping for the best- anyone have any other insight.
 
josh937 said:
We are stumped. Besides putting it all back together and hoping for the best- anyone have any other insight.
Click to expand...
I can't recall if you tried running without the air filter - did this get tested?

Earlier suggestions were to take it to another A&P - perhaps a different set of eyes will help.
 
josh937 said:
Still stumped....
Click to expand...
Still sounds very rich for some reason. Can you describe the behavior of the boost pump when starting with a dry fuel bowl or first start attempt of the day? Need you describe the sound and the behavior of the pressure on the gauge.

Master switch on: Fuel pressure should be zero and the pump silent
Boost pump on: fuel pump will rattle furiously and pressure will build on gauge. As fuel pressure peaks, pump will slow or stop . This behavior will be very obvious to the ear. What is the pressure reading at peak?
Boost pump OFF: pressure should SLOWLY bleed down. If pressure bleeds off rapidly, then you likely have a bad needle and seat. does it bleed quickly until a certain pressure then slow? That might indicate that the pump is overpowering the needle a bit, and the float only closes off once the overpressure is removed.

Your initial post indicates the rattle pump sounds the same in all phases of the fuel pressurization/bowl fill process. If you are SURE of this, then that’s where you need to look, because that is wrong in my experience.
 
Confirm that the mags were overhauled but the carb was not tampered with until after the starting problem occurred. If that is correct I would suspect a mag problem. Bendix or Slick Mags? Impulse coupling on left mag?
When you did get it started how was the mag check. What r/m for mag check?
The mag timing pin applies only to Slick mags. For the Bendix mags the impulse must be snapped, the mag gear rotated backward slightly past the point opening and then forward again to where the points just start to open. Usually no means to lock the mag in that position, so very easy to move the gear while installing the mag. The key is that there should be a red mark on the gear and you should be able to verify after the mag is installed that the red mark is near the center of the inspection hole. Then connect the mag timer and fine tune the timing by rotating the mag slightly.
 
Boost pump check: When I run the boost pump it sounds the same throughout. I then removed the fuel line from the carb to release the pressure, and when I hit the boost pump I could hear a change within about a second. It's not as drastic as normal, but there was something.
The pressure gage went up quickly with the boost pump on, then slowly reduced once it turned off.

Last time it ran the mag check looked fine, roughly 50 rpm drop (I can't remember specifically).

I have not tried to run without air filter- I will try that when the carb gets back.
 
My money is on your impulse magneto. It was either not serviced properly, or it was installed/wired incorrectly. Some ignition switches kill the non-impulse magneto until you release the key after starting. If the impulse magneto was installed on the wrong side it will make starting as you describe. The impulse magneto is typically installed on the left side, but being an experimental the wiring could have been set up either way. If your mechanic blindly installed it o the left without verifying that is how the ignition is set-up then that could easily be your problem. Also, How was TDC verified when timing the magnetos? Since the plane is relatively new to you; you can't assume the timing marks are correct on the flywheel. On Experimental's it is not unheard of to have the flywheel installed out of time.

1. Remove the grounding lead from the impulse magneto and see if it starts properly?
2. Remove both magnetos and verify the internal timing.
3. Verify TDC with a dial indicator on the piston.
4. Reinstall the magnetos and re-time/synchronize with a squawk box.

Does your plane have a primer of any type? If so Do Not pump the throttle at all. On a carbureted engine you only need the boost pump if the plane has a solenoid primer. In that case it is used to supply fuel pressure to the primer. The boost pump is there as a back-up to the engine driven fuel pump. The fuel pump only moves fuel from the wings into the carburetor bowl. It has nothing to do with how well the engine runs or starts.

I am very worried that your mechanic thinks it is a carburetor problem. Was it touched during the annual? If not, the guy flat out sucks at troubleshooting. Carburetors don't break on their own. However; you do need to find out why the throttle cable is binding before further flight. Are you sure it is not the friction lock?

It is not hard to over-lubricate a K&N filter. It has happened to all of us and comes with experience. Certified planes come with the filters pre-oiled, so your A&P may have very little experience lubricating them properly. Since you have already run the engine and flown it, the excess oil has been pulled from the filter and is not your problem.

The fuel dripping from the vents is normal for the vent design. It has nothing to do with your hard starting problem. Fuel gets trapped in the bottom of the vent bend and then gets forced out the vent by expansion in the tank.
 
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