never use to have and issue starting my 520 and for the last several months it's giving me grief.......now I'm to the point of trying to hard I think. mixer in throttle in,,,,mixer out throttle in booster pump on for 1 sec booster on 30 sec....etc etc etc.
I'm a month away from annual so maybe the plugs need cleaning or replaced, so will start there. Battery seems ok.....anyway it stays up long enough for 3-4 attemps to start. The only other thing that I have notice is on shut down, every once in awhile when I pull the mixer all the way out it doesn't die right away....it will chug chug sputter then die......

So those of you that have lots of time with a 520 please feel free to comment and tell me how you do a

Cold start

Hot start

thanks

How much time on the spark plugs? First thing I'd do is pull them & check the resistance through them-- replace if 5,000 ohms or above. Bendix mags will spark old plugs long after Slicks quit, but even Bendix mags have their limits.

Here's how I start an IO 520 on a Cessna 185/206:

Mixture full rich
Throttle Idle
Boost pump low speed ON (yellow side of rocker switch)
Smoothly advance throttle to wide open--You SHOULD hear the boost pump increase to medium speed
Return throttle to idle
Activate Boost Pump on High (Spring loaded red side of rocker switch) and verify that the pump sound increases to high boost.
Throttle to approximately 1/2 inch open, boost pump switches OFF
Start engine

This does a couple things:

1) It primes the engine
2) It verifies that the mechanical connection between the throttle and the boost pump control is functional--if it's not (ie: the pump does NOT increase speed when the yellow side of the switch is ON and the throttle is advanced) DO NOT fly the airplane. If you were to lose your engine driven fuel pump, you'd have to rely on the emergency side of the pump switch, and there is a high probability that the pump will overheat fairly quickly at that speed. Having lost an engine driven pump while I was approximately 20 miles from shore over cold water, I can testify that this is an important check.
3) This follows the manufacturer's recommendations.

I do this for hot or cold. It's always worked fine for me.

It sounds like something else is going on, however. Maybe spark plugs, but I'd suspect something in your fuel servo, or screens..???

MTV

Pretty much the same as MTV's.

On a cold start, I advance the throttle after turning on Low-Boost and then watch the fuel flow. Once it shows mid range fuel flow I hold the throttle in that position for maybe 5 seconds, then retard the throttle to idle. Boost pumps off. Then for start, I crack the throttle as I hit the starter.

On a hot start, the same, except I may run boost longer to purge the fuel lines.

Gump

Pretty much the same as MTV and Gump other than after purging (flooding) I pull the mixture to cutoff for the "Hot" start.
Once it fires, I push the mixture in.
Old habit from the C-402 days in Vegas and Grand Canyon.
Cold starts I leave the mixture in.

Sounds like it might be a good idea to have maintenance setup your fuel system.
I've had to tweak mine a few times as linkages, adjustments, change with age/wear.
Keep us posted with your findings.

Thanks

Mark
'80 A185F

It verifies that the mechanical connection between the throttle and the boost pump control is functional--if it's not (ie: the pump does NOT increase speed when the yellow side of the switch is ON and the throttle is advanced) DO NOT fly the airplane. If you were to lose your engine driven fuel pump, you'd have to rely on the emergency side of the pump switch, and there is a high probability that the pump will overheat fairly quickly at that speed. Having lost an engine driven pump while I was approximately 20 miles from shore over cold water, I can testify that this is an important check.

I think my electric pump didn't quite work correctly!!
Same thing with an IO-470
Was damn lucky,(IF YOU CAN LOOK AT IT LIKE THAT) 35' from the end of the runway, and 300' short of the first of many houses!!
GT

My IO-520 has a one speed boost pump. On a cold start all levers forward. Boost pump on for 3-5 seconds then off. Bring throttle to idle then about two full turns in. Crank. Always starts in a few blades.

This is a 64 206 with the aux fuel pump on the firewall with 2 (high and low) rocker style switches. 1 is red the other is yellow The book says that the low side operates only when the switch is in the start position......any way of checking if the low side really is working with out unhooking the starter?

Bighorn wrote:This is a 64 206 with the aux fuel pump on the firewall with 2 (high and low) rocker style switches. 1 is red the other is yellow The book says that the low side operates only when the switch is in the start position......any way of checking if the low side really is working with out unhooking the starter?

I have a 63 205. Same setup. I forget about the low side and just use high. Full rich Full throttle while holding the switch for a couple of seconds. if it cranks over a few blades and doesnt fire then crack the throttle and keep cranking a little longer til it fires. Hot start about the same except prime a little longer then crack the throttle and about the time it fires be ready to give it another shot of prime (or two) if required.

I do it like this on 206's and 207's also turbo or not.

SE6601KF wrote:

Bighorn wrote:This is a 64 206 with the aux fuel pump on the firewall with 2 (high and low) rocker style switches. 1 is red the other is yellow The book says that the low side operates only when the switch is in the start position......any way of checking if the low side really is working with out unhooking the starter?

I have a 63 205. Same setup. I forget about the low side and just use high. Full rich Full throttle while holding the switch for a couple of seconds. if it cranks over a few blades and doesnt fire then crack the throttle and keep cranking a little longer til it fires. Hot start about the same except prime a little longer then crack the throttle and about the time it fires be ready to give it another shot of prime (or two) if required.

I do it like this on 206's and 207's also turbo or not.

Well I tried this one tonight and the 206 poped right off on second blade. I wanted to change oil so I wanted to warm it up good. Looking at the wind sock 260 at 12-14kts, good evening for a little cross wind down 18. afterwards to the fuel pump to top off the tanks and I thought ......good time to see if it works on HOT start.......sometimes I can be a knotthead but thinking 3-5 sec on cold start I'll go 10 sec on hot start...WRONG ...flooded what a dumbshit I can be, so mixter at cut off throttle at idle ..CRANK ...3 blade pop, mixer rich and away we go
Going to try the 3-5 on a hot start next time....don't over do it eh

Thanks guys

A small tip on starting hot 520's I learned in my days in Central America. If your stopping just to fuel or it will be a short time until you re-start the engine will heat the spider and the injector lines, so vaporized fuel will push the fuel out of the lines. You have to run a bunch of fuel into the system to prime and cool it off, risking flooding and fire. So if you take a shop rag and soak it in water and place it on top of the spider (through the oil fill door on top). Leave the door open to remind you of what you have done. The water soaked rag will keep the spider cool and not let it become hot enough to vaporize the fuel. Just remember to remove the rag and close the door.

If you have Slick mags, be sure to check the internal timing. It is very important to perform the 500 hr. inspection on them. I have seen the mag to engine timing be perfect, but if the internal timing is off, they can be extremely hard to start. It can be even more pronounced on a Lyc. with slick mags, but it also happens on TCM.