Need CIS help... of course

[McGalliard]

Originally Posted by mikedsilva

The machine shop found that the valve guides were SO worn, that the valves had so much movement in them, that the seats were concave. Pretty sure this was the source of my white smoke. New guides, new valves and new seats.

AfWhen the muffler got hot, it made the oil smoke... I changed to a known good muffler and the engine never blew smoke. So in the end, I tried to flush out the old muffler, and then I just ran it and ran it till all the oil was burned out of it!

Neither of these prospects sound particularly appealing. But I'll take option 2 over 1 if I have a choice.

[McGalliard]

Originally Posted by PeteKz

The crank pulley has marks 120 degrees apart that indicate when the pistons are at TDC. The remaining question is when each piston is at TDC at full compression. That will become obvious when you hook up the leakdown tester.

Next item: The leakdown test may not tell you where the oil is coming from. Specifically, if the intake valve guides or seals are leaking oil, you will measure more or less normal leakdown numbers. But let's see what the test shows.

This was useful info. Thanks. I found a diagram that labelled all of the crank pulley marks for a 2.7L so that expedited things. I also watched a vid of a kooky lady in a sun visor starting the breakdown of her 3.2L engine. She had a good explanation of the methods and using the pulley marks.

Before I relay the leak down test results, let me say I believe the testing situation is less than ideal. If there is a consensus to repeat it properly, I will do my best to do so, but I'll need a little more time. Suboptimal conditions include that the engine was not warmed up AND for whatever reason I could not get the leak down tester to pressurize more 30 psi while keeping the leak down % gauge in range. I'm tempted to get my own that has pressure in and pressure out and calculate the % loss myself. Anyone have recs?

The results:
#1 - 25%
#2 - 20%
#3 - 15%
#4 - 25%
#5 - 30%
#6 - 37%

Regardless of the conditions, I don't like #6. Of the old plugs I removed #6 and #4 were the most wet and gunked.

Relatedly, since I had a pin spanner on hand for the fan pulley rotation, I took the opportunity to start the exchange of a new belt, because the old is cracked. Anyone have any tricks for getting the spacers and nut back on, aligned, and appropriately tightened????

If it's not one thing, it's another...

[McGalliard]

I think I need a new gauge setup and repeat testing.

[PeteKz]

Yeah those results are pretty bad. Try another gauge and repeat the testing. Also listen for whether leak-down is coming out the exhaust (indicates bad exhaust valve), out the intake (bad intake valve), or through the case breather (bad ring seal)

[dedyplay]

The fuel pump delivery test is measured at the return line to the tank.

[McGalliard]

Originally Posted by PeteKz

Yeah those results are pretty bad. Try another gauge and repeat the testing. Also listen for whether leak-down is coming out the exhaust (indicates bad exhaust valve), out the intake (bad intake valve), or through the case breather (bad ring seal)

That’s one of the problems with the low psi. Any leak was so wimpy in volume, I could hear it but not localize.

[dedyplay]

Quite sad.

[fanaudical]

Originally Posted by McGalliard

I think I need a new gauge setup and repeat testing.

Suggestion: Post a pic of the leak-down tester you used and your compressor. You need a compressor with decent flow capability for a good test.

I've seen some leak-down tests that were not valid due to insufficient air flow from the compressor.

And there is some variability in leak-down test definitions. Lycoming recommends doing the test at 80psig supply pressure (and this is the reference that I've used for testing my stuff). The one difference is that I do calculate a percentage drop.

https://www.lycoming.com/sites/default/files/attachments/Cylinder%2520Compression.pdf

[McGalliard]

Originally Posted by fanaudical

Suggestion: Post a pic of the leak-down tester you used and your compressor. You need a compressor with decent flow capability for a good test.

I've seen some leak-down tests that were not valid due to insufficient air flow from the compressor.

And there is some variability in leak-down test definitions. Lycoming recommends doing the test at 80psig supply pressure (and this is the reference that I've used for testing my stuff). The one difference is that I do calculate a percentage drop.

https://www.lycoming.com/sites/default/files/attachments/Cylinder%2520Compression.pdf

The compressor shouldn’t be the problem. I think the gauge, which is 30+ years old, is out of calibration. I’m aiming to get the type that requires one to calculate the percentage drop. And I had also heard a supply pressure of 80-90 psi is the target.

[AndrewCologne]

It also depends on the type of the leak down tester. Common Chinese cheap ones work with pressures of about 1 bar for measuring, which results in higher percentage results where these are still within specs.
The higher the pressure for testing the smaller the tolerance window gets. Means with 100 Psi a result of 8% can already mean an almost non acceptable pressure loss.
Those professional Hazet testers i.E. with only one gauge work internally with 4 Bar towards the combustion chamber:

https://nineelevenheaven.wordpress.com/leak-down-tests-on-a-911-sc/

[McGalliard]

Originally Posted by AndrewCologne

It also depends on the type of the leak down tester. Common Chinese cheap ones work with pressures of about 1 bar for measuring, which results in higher percentage results where these are still within specs.
The higher the pressure for testing the smaller the tolerance window gets. Means with 100 Psi a result of 8% can already mean an almost non acceptable pressure loss.
Those professional Hazet testers i.E. with only one gauge work internally with 4 Bar towards the combustion chamber:

https://nineelevenheaven.wordpress.com/leak-down-tests-on-a-911-sc/

That link certainly explains the need to know which variety of tester one is using. In my instance, I had the first version using very low pressure. However, at baseline the right gauge shows no greater than 80% leak down, and so I'm not confident that I trust it fully. I have ordered one similar to the last version described, so I think I have the most flexibility. Stay tuned...

[McGalliard]

Here’s the latest update:

I decided to skip the leak down test and just put some fuel in it to go. The smoke cleared up quick enough. There are a few bursts here and there, but nothing I’m worried about for now. On cold start it would catch right away, but kind of lumber around and hunt a little bit in the first 3-5 min. Once driving, that goes away. But then I noticed mild surging when cruising just somewhere between 2000 and 2500 rpms. That goes away when adding a throttle load or immediately upon engaging the clutch. Was going to get into some mixture adjustment thinking that was running rich and then… it just died after 30 seconds of idling one evening. I’ve lost spark and I think it’s probably the CDI box.

[HarryD]

Originally Posted by McGalliard

Here’s the latest update:

I decided to skip the leak down test and just put some fuel in it to go. The smoke cleared up quick enough. There are a few bursts here and there, but nothing I’m worried about for now.

Good. Sounds normal.

On cold start it would catch right away, but kind of lumber around and hunt a little bit in the first 3-5 min. Once driving, that goes away. But then I noticed mild surging when cruising just somewhere between 2000 and 2500 rpms. That goes away when adding a throttle load or immediately upon engaging the clutch.

CIS does not like driving under 2500 rpm. 3000+ much better.

Was going to get into some mixture adjustment thinking that was running rich and then… it just died after 30 seconds of idling one evening. I’ve lost spark and I think it’s probably the CDI box.

Leave the mixture alone. Search my handle for "Telegraph test" to determine if you have an ignition problem.

[McGalliard]

More update...

Spark was lost, so I guessed and sent out the CDI box to be rebuilt with new electronics. Got it back, installed, and after a little effort it started up again... then died. Then started and then died. Did that a few times, then ran for a few minutes. Noticed that the tach needle was erratic so I thought the rebuilt CDI was bad because I didn't have that problem before. Guessed again and got a used, not-rebuilt CDI box and... no spark. Turned out my points had gone bad. Now, this is where it gets interesting...

Temporarily fixed the points with 1200 grit sandpaper as a stop-gap measure and for troubleshooting purposes. Reinstalled and set the gap with a feeler gauge at 0.014" because I didn't have a dwell meter. Everything was running and even better than before! Super exciting, until...

NOS Bosch points come and get installed. Again, set by feeler gauge but to 0.012", which I had read somewhere. Adjusted the timing, which I hadn't done before. It was WAY ahead of what it should be (if I recall correctly). Car didn't run as well as before. A little hesitation and sluggish here and there. I figured this would be fixed with proper dwell angle setting. So, got the dwell meter in hand and discovered the dwell angle was way high, like upper 40s. Spec book says 38 +/- 3. So I open the points gap to drop the dwell. Get it down to 41, so upper limits of spec. Then I started having popping at idle (out the exhaust (99% sure)). Messed around with points, setting and resetting, and timing and I can't get that to go away now. It's reduced, but still there with throttle.

So, who's got a foolproof order of operations to setting these things and returning to normal performance?!

[HarryD]

Originally Posted by McGalliard

More update...

Spark was lost, so I guessed and sent out the CDI box to be rebuilt with new electronics. Got it back, installed, and after a little effort it started up again... then died. Then started and then died. Did that a few times, then ran for a few minutes. Noticed that the tach needle was erratic so I thought the rebuilt CDI was bad because I didn't have that problem before. Guessed again and got a used, not-rebuilt CDI box and... no spark. Turned out my points had gone bad. Now, this is where it gets interesting...

Temporarily fixed the points with 1200 grit sandpaper as a stop-gap measure and for troubleshooting purposes. Reinstalled and set the gap with a feeler gauge at 0.014" because I didn't have a dwell meter. Everything was running and even better than before! Super exciting, until...

NOS Bosch points come and get installed. Again, set by feeler gauge but to 0.012", which I had read somewhere. Adjusted the timing, which I hadn't done before. It was WAY ahead of what it should be (if I recall correctly). Car didn't run as well as before. A little hesitation and sluggish here and there. I figured this would be fixed with proper dwell angle setting. So, got the dwell meter in hand and discovered the dwell angle was way high, like upper 40s. Spec book says 38 +/- 3. So I open the points gap to drop the dwell. Get it down to 41, so upper limits of spec. Then I started having popping at idle (out the exhaust (99% sure)). Messed around with points, setting and resetting, and timing and I can't get that to go away now. It's reduced, but still there with throttle.

So, who's got a foolproof order of operations to setting these things and returning to normal performance?!

I do the following:

1-Gap points to spec.
2-Start motor, set dwell.
3-Set timing. Check for proper advance to 36 degrees at 4000+rpm.

FWIW Dwell affects timing.

[McGalliard]

I'm hoping I figured out at least one of the issues. I was loaned 2 dwell meters and they apparently do not read the same. In fact, they are off by about 10 degrees from one another. So, while I set the dwell initially to the first meter and got it to the upper limits of spec, which felt like a major change from where my baseline starting point was, the second meter reads that I'm now way under spec for dwell angle. So, I'm hoping that the first meter is out of calibration and the second meter is correct. I will reset the dwell using the second meter, then readjust timing hoping that it clears everything up back to normal and confirms the problem was the tool, not the car.

[McGalliard]

Reset the dwell with the second meter, which meant closing the points gap, so now it's dead on 38 deg. Adjusted the timing. Still get exhaust pops, but now on early decel or as soon as I come off the throttle. In reading some other threads it sounds like this is not so terrible. However, I will not accept it. I do not like the sound and most importantly, it didn't do it 48 hours ago. I have only touched the points, dwell angle, and distributor timing.

I am running out of heavy sighs.