Problems with Lycoming O-320

We are rebuilding a Lycoming O-320 for use in an RV. We have noticed the following problems and don't know how to resolve them.

We have put on a remanufactured carborateur. At full throttle, the engine runs rough unless the mixture is leaned very much (over half of the mixture control). Is it normal for it to be this reach? If not, how would I adjust it?

In doing the mag check, the engine quit when the ignition switch was turned to R. We tried tracing the continuity of the p-leads through the ignition switch. We did not notice a problem. We switched the p-leads and the problem followed the p-lead. Also, when attaching a mag timing light, the light for the left mag was always on. Any ideas of what we need to check next?

We are also curious to know what the static rpm at full power would be?
Steve Will

Adjust your carb (pretty easy to do, but depends on which carb you have put on), replace the P-lead, and static rpm will depend on the prop you have. I don't mean to be "master of the obvious" or a wise-guy or anything. Just some simple suggestions I'm sure you've already thought of.

Welcome to VAF!

O-320 carb

Hi Steve,

Firstly, are you sure the carb you have is the correct model for the engine you have ? If so, is it in good condition ?

If that all checks out, then I would make sure that the float level is correct and that the needle & seat is shutting off the fuel effectively.

If that is ok, then check that you have the correct main jet for both the carb and your application. Let us know how you go.

Cheers

Martin in Oz

Which model?

Which model O-320 is it?

gil in Tucson

thekarateguy said:

We are rebuilding a Lycoming O-320 for use in an RV. We have noticed the following problems and don't know how to resolve them.

We have put on a remanufactured carborateur. At full throttle, the engine runs rough unless the mixture is leaned very much (over half of the mixture control). Is it normal for it to be this reach? If not, how would I adjust it?

In doing the mag check, the engine quit when the ignition switch was turned to R. We tried tracing the continuity of the p-leads through the ignition switch. We did not notice a problem. We switched the p-leads and the problem followed the p-lead. Also, when attaching a mag timing light, the light for the left mag was always on. Any ideas of what we need to check next?

We are also curious to know what the static rpm at full power would be?
Steve Will

Click to expand...

You got several variables going. Where'd you get the carb? A reputable source? Did it run before?

But regardless, with what info you've presented, it sounds like an ignition problem from out here in Internet world. Did the mags work before? They Slicks, Bendix? How old? You getting any backfiring? Did the key-switch work before? You sure all the plugs are working? Checked them recently to make sure they haven't fouled (bottom ones!) with oil?

Also, you sure the mags are timed correctly? It takes a little practice, the right tools and a pretty good understanding of how magnetos work. I recommend Sacramento Sky Ranch for a source on info.

If you have problems with the p-leads, try removing the questionable one and run the engine. Insulate the lead so it won't flop around and ground out intermittently with the engine running, or better yet rig up a remote means of grounding separate from the switch you can bring into the cockpit.

Note - the engine will be able to fire with the p-lead removed!! I.e., keep everyone away from the prop, and put a warning flag on it if you walk away from the plane. And don't run it with people around who aren't familiar with airplane engines and spinning propellers.

I'd work more on ruling out ignition problems before the carb.

Low Pass said:

Note - the engine will be able to fire with the p-lead removed!!

Click to expand...

I believe the mags have a spring steel clip that grounds the mags when the p-lead is not installed. This will NOT allow the mag to fire with the p-lead removed.

Mark

Mark Burns said:

I believe the mags have a spring steel clip that grounds the mags when the p-lead is not installed. This will NOT allow the mag to fire with the p-lead removed.

Mark

Click to expand...

Interesting. i don't recall that with my old Bendix mags, but could be. On my Slicks, there's a screw terminal as I recall that shouldn't know whether or not there's a wire attached.

Regardless, if you remove the wire from the ignition switch, it should be ungrounded and able to fire.

Low Pass said:

Interesting. i don't recall that with my old Bendix mags, but could be. On my Slicks, there's a screw terminal as I recall that shouldn't know whether or not there's a wire attached.

Regardless, if you remove the wire from the ignition switch, it should be ungrounded and able to fire.

Click to expand...

Low Pass,
Yep, you're right about the Slick mags with just the screw terminal. I'd forgotten that some are like that. I may be all wet about the spring clip. I may have it confused with something else. Seems like it would be a good idea though, until your p-lead backed out in flight.

Mark

Check both p-leads.

thekarateguy said:

We are rebuilding a Lycoming O-320 for use in an RV. We have noticed the following problems and don't know how to resolve them.

We have put on a remanufactured carborateur. At full throttle, the engine runs rough unless the mixture is leaned very much (over half of the mixture control). Is it normal for it to be this reach? If not, how would I adjust it?

In doing the mag check, the engine quit when the ignition switch was turned to R. We tried tracing the continuity of the p-leads through the ignition switch. We did not notice a problem. We switched the p-leads and the problem followed the p-lead. Also, when attaching a mag timing light, the light for the left mag was always on. Any ideas of what we need to check next?

We are also curious to know what the static rpm at full power would be?
Steve Will

Click to expand...

Steve, when the switch points to the right, the left mag should be grounded and when the switch points to the left the right mag should be grounded. When both is selected neither should be grounded.

When I first started my engine, one side didn't work and I traced it by to a bad crimp that grounded the p-lead all the time.

Kent

Bendix 20 series and 200 series mags that used the old style cigarette p-lead type had what was called a "dead man" spring in the mag. The spring would contact the mag cover plate when the cigarette style plead was removed, thus grounding the points. When the P lead cigarette was installed it pushed the dead man spring away fro m the mag cover un-grounding the points.
Good Luck,
Mahlon
"The opinions and information provided in this and all of my posts are hopefully helpful to you. Please use the information provided responsibly and at your own risk."

On the mag timing, you need to pull the prop past TDC to trip the impulse coupling, then back up to the timing marks.

Roberta