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- Mar 10, 2018
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I'm hoping this will ring a bell with somebody here.
I have a '66 260B. IO540-D4A5. Over the last couple of months I've been having more and more trouble with cold starts. This engine has always been reliable and started well in all conditions; I first attributed it to sloppy technique, but now I'm convinced there's something else wrong.
The symptom is that it just doesn't want to catch. It acts like a lean situation; I'll prime it, crank it, and nothing. No puffs or coughs at all. Usually I've been able to get it to start by continuing to prime, until I get to a flooded-start situation.
Last week I went through this again, trying to diagnose better what I was doing wrong. In cold weather I'll normally prime it 3-4 seconds, I did 1 second at a time, cranking in between, with no results. I tried over priming it, and tried the flooded start, again nothing. I checked under the cowl, there was a puddle of fuel in the bottom where it had leaked out of the air box. Let it rest and the fuel dry out, over primed it again, and flooded start eventually worked.
Today I tried again, but even the above didn't work. I tried pulling out a plug, and it was bone dry. Yet there was another puddle of fuel in the cowl.
Once I get it running, it works perfectly. Mag checks reveal both mags working find. Fuel flow in flight is right where it's always been. Hot starts are fine, 3-4 blades and off it goes. It's just cold starts which are not working right.
I have the feeling that there's some kind of leak in the fuel system, which affects only priming. My understanding is that the boost pump and mechanical pump drive into the same injector lines, and go through the same regulator. So it's a little difficult to see an obvious place for a failure.
I'll be calling my A&P tomorrow. I'm hoping somebody here may have seen a similar situation and have some idea.
Thanks in advance for the group's wisdom.
I have a '66 260B. IO540-D4A5. Over the last couple of months I've been having more and more trouble with cold starts. This engine has always been reliable and started well in all conditions; I first attributed it to sloppy technique, but now I'm convinced there's something else wrong.
The symptom is that it just doesn't want to catch. It acts like a lean situation; I'll prime it, crank it, and nothing. No puffs or coughs at all. Usually I've been able to get it to start by continuing to prime, until I get to a flooded-start situation.
Last week I went through this again, trying to diagnose better what I was doing wrong. In cold weather I'll normally prime it 3-4 seconds, I did 1 second at a time, cranking in between, with no results. I tried over priming it, and tried the flooded start, again nothing. I checked under the cowl, there was a puddle of fuel in the bottom where it had leaked out of the air box. Let it rest and the fuel dry out, over primed it again, and flooded start eventually worked.
Today I tried again, but even the above didn't work. I tried pulling out a plug, and it was bone dry. Yet there was another puddle of fuel in the cowl.
Once I get it running, it works perfectly. Mag checks reveal both mags working find. Fuel flow in flight is right where it's always been. Hot starts are fine, 3-4 blades and off it goes. It's just cold starts which are not working right.
I have the feeling that there's some kind of leak in the fuel system, which affects only priming. My understanding is that the boost pump and mechanical pump drive into the same injector lines, and go through the same regulator. So it's a little difficult to see an obvious place for a failure.
I'll be calling my A&P tomorrow. I'm hoping somebody here may have seen a similar situation and have some idea.
Thanks in advance for the group's wisdom.
