hard starting IO520

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JOhnH

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An IO520 w Gami injectors in a Bonanza V35. Less than 200 hrs on engine.

I have always heard these are hard to hot-start, but we always have trouble restarting the engine even if it has only been running for a few minutes and the OAT is ~45degrees. When that happens, we are usually successful, eventually, by using the hot start procedure.

Occasionally, I have heard a single backfire during startup, but no other problem indications other than hard starting. I'm not sure how serious that is, but it is in the shop now for some other things and I asked them to check that out.

It usually starts up ok on the first try for the day, but sometimes it catches for a few seconds then quits. Then the chances of starting, without going through the hot start procedure decreases.

Question: Normally, we run the aux fuel pump till the needle stabilizes prior to first start. Should we do that for each attempt, if it doesn't start properly the first time?
 
I'm gonna go with not enough spark after the first start event. Since your engine uses shower of sparks (SOS) for starting....it requires a strong battery and a properly functioning vibrator.

A weak battery will not provide enough spark to restart.....even though your engine is cranking. Open the vibrator box and clean those contacts....also clean the extra points for starting in the left mag.....rinse and repeat.
 
This is my procedure for the 520 in a V35.

No prime.
Throttle idle.
Mixture cutoff.
Start.

The engine usually kicks over within a blade or two. At that point, it's:

Mixture 50% (rough position for a leaned taxi) and boost pump on immediately.
Let it stabilize.
Boost pump off.

You have to bring the mixture up and throw the pump on almost at the exact same time and definitely AS SOON AS the first cylinder fires.
 
I know what you mean, easy to start on the first of the day then it gets touchy. My theory is that if you have any problem, including an afterfire, on subsequent starts it's usually because of too much fuel. What works best for me is to just set it up for a fast idle--1200 rpm or so, and hit the starter then the boost pump quickly if it fires then starts to stumble. I've never had to use the whole hot-start routine; I think it actually has to be really hot for it to be necessary.
 
JOhnH said:
An IO520 w Gami injectors in a Bonanza V35. Less than 200 hrs on engine.

I have always heard these are hard to hot-start, but we always have trouble restarting the engine even if it has only been running for a few minutes and the OAT is ~45degrees. When that happens, we are usually successful, eventually, by using the hot start procedure.

Occasionally, I have heard a single backfire during startup, but no other problem indications other than hard starting. I'm not sure how serious that is, but it is in the shop now for some other things and I asked them to check that out.

It usually starts up ok on the first try for the day, but sometimes it catches for a few seconds then quits. Then the chances of starting, without going through the hot start procedure decreases.

Question: Normally, we run the aux fuel pump till the needle stabilizes prior to first start. Should we do that for each attempt, if it doesn't start properly the first time?
Click to expand...

Always be ready to blip the fuel boost. If it starts to quit a quick blip of the boost will keep it alive.

As to hot starting, I would prime normally, all levers toward. Start cranking and smoothly pulling the throttle back, not too fast, not too slow. When it fires you can quickly reduce throttle. Be ready to blip the fuel boost to keep it running if needed.

With a little practice this can be done without starting at a high rpm.

I've found this technique to work well on all fuel injected continentals. I've found other techniques to be very airframe specific. Might work in a bo but then not work in an acclaim, etc. why? I have no idea. I stick with the above. I regularly fly behind IO-470, IO-520, TSIO-550 across Beech, Mooney, Piper and Cessna. Works in all of them nicely.
 
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JOhnH said:
An IO520 w Gami injectors in a Bonanza V35. Less than 200 hrs on engine.

I have always heard these are hard to hot-start, but we always have trouble restarting the engine even if it has only been running for a few minutes and the OAT is ~45degrees. When that happens, we are usually successful, eventually, by using the hot start procedure.

Occasionally, I have heard a single backfire during startup, but no other problem indications other than hard starting. I'm not sure how serious that is, but it is in the shop now for some other things and I asked them to check that out.

It usually starts up ok on the first try for the day, but sometimes it catches for a few seconds then quits. Then the chances of starting, without going through the hot start procedure decreases.

Question: Normally, we run the aux fuel pump till the needle stabilizes prior to first start. Should we do that for each attempt, if it doesn't start properly the first time?
Click to expand...

Why don't you two fly down to FXE for lunch and I'll show you how to hot start the easy way. Yes, you use the pump on high to prime for every start.
 
Too much fuel. When the engine is cold it needs more fuel. When it's been shut down hot, the fuel still in the injector lines gets hot and boils and ends up in the intakes. There it sits, making lots of fuel vapors, waiting for the next start. Lots of fuel for the start. The pilot comes along, shoves the mixture full rich, hits the boost pump, and pushes even more fuel into the intakes, enough that the cylinders are getting a mixture that is way too rich to fire.

I think the old guys who grew up driving cars and trucks that had chokes were able to understand this and didn't have much trouble with hot starts. Younger folks have grown up with computers that figure it out for them, and modern injected cars have solenoid-operated injectors that don't dribble raw fuel into the intakes after shutdown anyway.
 
JOhnH said:
An IO520 w Gami injectors in a Bonanza V35. Less than 200 hrs on engine.

I have always heard these are hard to hot-start, but we always have trouble restarting the engine even if it has only been running for a few minutes and the OAT is ~45degrees. When that happens, we are usually successful, eventually, by using the hot start procedure.

Occasionally, I have heard a single backfire during startup, but no other problem indications other than hard starting. I'm not sure how serious that is, but it is in the shop now for some other things and I asked them to check that out.

It usually starts up ok on the first try for the day, but sometimes it catches for a few seconds then quits. Then the chances of starting, without going through the hot start procedure decreases.

Question: Normally, we run the aux fuel pump till the needle stabilizes prior to first start. Should we do that for each attempt, if it doesn't start properly the first time?
Click to expand...


I have the same engine, IO520D in my amphib, which is a instance where you need to be able to start up quick, push her off the dock with a current and can't start, no bueno.

So first start,
Throttle and mixture forward, boost pump till stabilized, pumps off, throttle back and crack the throttle a little, start, typically within a couple blades.

Hot engine start 1

Pumps off, Mixture rich, crank as you slowly advance the throttle, once she catches bring her back to idle. Typically works within one full rotation or two

Hot engine start 2

Mixture rich, throttle in, pumps on till stabilized, pumps off, throttle all the way back, mixture all the way forward to full rich, crank till she catches, throttle to idle as you push the mixture rich.
 
or....if you know you'll be shutting down for a few minutes for fuel.....turn "off" the engine using the key switch.....and don't touch a thing.

On start up....don't touch a thing. Begin cranking with the low boost pump on....with an occasional high bump. After it starts......leave the low boost on as required.

That's my trick for the TSIO-520.....
 
jesse said:
Always be ready to blip the fuel boost. If it starts to quit a quick blip of the boost will keep it alive.

As to hot starting, I would prime normally, all levers toward. Start cranking and smoothly pulling the throttle back, not too fast, not too slow. When it fires you can quickly reduce throttle. Be ready to blip the fuel boost to keep it running if needed.

With a little practice this can be done without starting at a high rpm.

I've found this technique to work well on all fuel injected continentals. I've found other techniques to be very airframe specific. Might work in a bo but then not work in an acclaim, etc. why? I have no idea. I stick with the above. I regularly fly behind IO-470, IO-520, TSIO-550 across Beech, Mooney, Piper and Cessna. Works in all of them nicely.
Click to expand...

You're welcome. :)
 
Cod or warm - the IO-520 in a Bo should be an easy start. One blade cold and maybe three blades hot. Certainly no more. See end comment about mags affecting starting.

There are very different procedures for cold versus hot. Extend the starter and starter adapter as these are expensive to repair.

I would also ask - have you had your fuel system calibrated recently? Suppose to be done every annual, but many, many, skip this procedure. You need to make sure your fuel pump is pumping the right flow. Also make sure fuel screen is cleaned annually.

Cold
- mixture rich
- full throttle
- boost pump on - run till fuel pressure peaks. Leave run for 2 seconds after it peaks. Then boost pump off.
- throttle 1/4 open
- crank engine - should start immediately

Hot
- idle cut off
- mixture rich
- run boost pump for minimum 60 seconds, and be prepared to run for 90 seconds in a very hot situation
- with boot pump running, open throttle fully for 5 seconds
- adjust throttle to 1/4 open
- crank motor - turn boost pump off - engine will start

You have to get the vapors out of the fuel system. That is what is causing hard starts most of the time.

If your mags have not been checked, the impulse coupler could be broken and this will also contribute to a hard start.
 
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We had a hard-start condition on a 300hr engine this year. Timing was fine, SOS system was fine, turned out that two spark plug leads had failed.
 
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