set timing

[rumb]

Ok, I looked all thru my engine manual can could not find how to set the ignition timing, or more exactly where the timing mark is located.

I know it is suppose to be TDC at 600 rpm, but I do not know where the pointer is located.  Is it the top of the TDC sensor bracket or somewhere else?

[daantjie]

On the 6.9 the pointer is very hard to see.  You need to stick your head way low next to the battery and shine your timing light at the damper. The pointer is way up at roughly the 11 o clock position. Watch out for the cooling fan

[rumb]

Ok, found the little pointer. was on 10 deg BTDC, I moved it up to 0. That was with the vacuum lines attached, which is noted several web sources.

When I revved engine up, I only got about 10+ degree total advance, is this correct?  I though it should be @33.

About the only other  instructions I found was this: http://www.m-100.cc/forum/topic.asp?TOPIC_ID=3085



1) To adjust ignition timing pull off both vacuum lines. After setting the firing point test specified firing point at idle with vacuum.

2) TDC with vacuum at idle of < 800 rpm

3) 9-16 degrees BTDC without vacuum @ 1500 rpm

4) 27-33 degrees BTDC without vacuum @ 3500 rpm

5) Effects of retard and advance vacuum functions

6-10 degrees RETARD with vacuum @ idle of < 800 rpm
8-12 degrees ADVANCE with vacuum @ 3500 rpm


So is the above the correct procedures for a euro 6.9?

[rumb]

I just set according the instructions I posted above.

Also found I had the vac advance line hooked up incorrectly according to http://handbook.w116.org/Engine/107/M117_45/1975/14-050.pdf

Now it looks more like 20-25 total advance without vac lines attached, though I did set intial value to @5btdc instead of 0 as some have done.  Also because I am at 5000 ft elevation and I tend to advance a little more on all my cars to compensate for that.

Seems to run a bit smoother, though now I need a test drive.

[rumb]

alright, got my first real drive in the car.  previous runs lacked power, now I can actually feel power of this engine!

I still get a backfire when the engine is cold and you start from a full stop. After it is warm no issue. Richen slightly?

Still seems the total advance is a little low.

[rumb]

I'm posting this chart since it was so hard to find.

Though common opinion on the forums to set to 0 at idle with both vacuum lines attached, this indicates that you should set it to 30 btdc at 3000 rpm. This value takes into account your mechanical advance. Note that the AC should be turned off while setting timing.

You then use the test values to insure that your mechanical and vacuum components are actually working as they should.

After setting to 30 btdc at 3000 rpm, then connect the vacuum lines and you should be at 0 +/-3 at idle. with vac lines attached total timing at 3000 rpm  should be 38-42 degrees. If you are not, then something is not working. (edit - though that is what is says on the chart, I dont think you could actually measure that unless you were driving down the highway under certain conditions
)

Disconnect the vacuum and test at 1500 and 3000 rpms for the values specified. Again if off the something's not working.I would suspect the mechanical advance since the adjusting value and the test values are both done without vacuum attached.

Now figuring out what is not working to me is the hard part to decipher.

Seems to me that from the chart that the vacuum advance and retard lines both pull opposite that same amount of 8 -12 degrees. So you should be able to disconnect each  line and see the appropriate movement of each one's effect. Turning on the AC should increase the timing and engine speed. I believe this is accomplished by REMOVING the vac retard thru the valve on the firewall.



The often quoted set to 0 at idle w/o vacuum is only valid if everything else is working, so that is why the test values and recommended process should be used instead.

Several sources indicate that the timing should be advanced 5-8 degrees if you operate at a high elevation, though they caution that this changes the operating conditions of when advances occur over the operation range. The ignition could advance too early in the curve.


Any comments appreciated, especially regarding determining if each component is working.(mechanical, retard and advance)

[rumb]

today's testing:

used mitivac to confirm that advance and retard both work on the disti diaphragm.  they both work fine.


Set timing to 30 at 3000 rpm, but at idle is at 12-15.

Checked to see if there was any vacuum on the line coming the A/C valve on the firewall. There was not any vacuum there.

The source point of this line is/was the nipple/port on top front of the air flap.  Hooked up vac gauge there and there was no vacuum. Isnt there suppose to vacuum from the port on top by the air flap? -  though I would think not as it is above the throttle plate.


My earlier engine originally did not have 2 vac ports as shown on this hose, it had 1.  I hooked up the retard vac source line to the 2nd hole and that seems to get the retard working correctly now.

The test values are good now except that the idle timing is now at 15btdc instead of 0. All the other values work. If I disconnect the advance line to the disti the timing drops to almost 0. I think this is correct function.  However disconnecting the retard line doesnt seem to do anything even though the line has 15 in of vacuum in it.

The advance line comes from the front port below the throttle plate. at idle it has 15 in vac, but drops quickly to zero as you accelerate as it is suppose to do.

The retard line at the disti has 17 at idle and drops some as you accelerate, but depending in throttle to 5-10 and rebounds quickly.

I like everything now except the idle advance seems to high.

[raueda1]

Hey Rumb,

Confirming my ignition setup will be the next project and I found your excellent thread.  Is it working well and is there anything more to add? 

BTW, over the course of my 6.9 adventures I found and fixed a few vacuum leaks.  My vacuum still seems low though, about 5-8 in  Hg at idle.  What's your vac at idle?  We're at about the same altitude and that surely plays a role.  Thanks and Cheers,

[rumb]

The amount of  vacuum depends on where you pull it from.

measure from the vac line that goes to all the inside the car vacuum lines above the fuse box.  that should be pure engine vacuum.

there may be 2 ports on the front side of the throttle body. one is above the plate and one below, so they have totally different characteristics.

also there is suppose to be a little blue plug in the hole where you adjust the FD mixture. it is often missing. a lot of air will get pulled into the engine if it is missing. I put a tiny screw into mine so I can grab it with pliers to easily remove it when needed.

[raueda1]

The amount of  vacuum depends on where you pull it from.

measure from the vac line that goes to all the inside the car vacuum lines above the fuse box.  that should be pure engine vacuum.

there may be 2 ports on the front side of the throttle body. one is above the plate and one below, so they have totally different characteristics.

Thanks, I'll experiment with these.  I measured off the tube going to the vacuum enrichment port on the WUR.  The WUR responds properly to whatever it "feels" from that so I'm not too concerned.

also there is suppose to be a little blue plug in the hole where you adjust the FD mixture. it is often missing. a lot of air will get pulled into the engine if it is missing. I put a tiny screw into mine so I can grab it with pliers to easily remove it when needed. 

You speak of the hole between the FD and sensor plate with the adjusting hex screw inside the hole, right? Mine has a screw in place there (some cars had the plug others had the screw?), so also not a problem.

Happily my list of problems is getting smaller.   That WUR thing was making me nuts.

[raueda1]

The picture is getting clearer.  Before messing with timing I did closer inspection of all the tubes and connections. 

1. The red advance line was OK.  I noted that at idle it does NOT pull any vacuum at all, but it DOES when throttle is just slightly opened and thereafter.
2.  the white retard line had a totally cracked rubber tube.  I replaced it.  Behavior was opposite of the red line line: vacuum at idle but no vac beyond idle.  This presumably means that at idle the retard line will retard the timing back from it's "mechanical" setting.

Timing settings BTDC, AC off:
                                          idle          3000rpm   SOTP* Performance
1.  vac lines disconnected:    ~10°         ~28°          Didn't drive car
2.  Vac lines connected:        ~10°         ~40°          Very, very strong
*Seat Of The Pants

This suggests that the advance is advancing OK but the retard isn't retarding right.  It should be retarding the timing at idle, which would put the timing at idle closer to 0° TDC.  This is exactly the same thing that Rumb reported above if I understand right.  Incidentally, I did try setting >>idle<< timing to 0° TDC.  As one might expect, that reduced all the figures above by about 10°.   Performance was very noticeably reduced. Fortunately I never heard any pinging during any of this.

So, this leads me to believe that the vacuum advance unit isn't working and needs replacement.  Does this make sense or am I missing something?  The adventure goes on....   Thanks and cheers,

[rumb]

do you have a mitivac?  try it on the retard and advance lines to the disti and observe how the timing changes.

The black curved hose make sure the port you use is open, I seem to recall having to drill it open.


you are correct, do not set timing to 0 at idle, set it at the 3000 rpm value. then observe what the other values are to confirm things.

[raueda1]

do you have a mitivac?  try it on the retard and advance lines to the disti and observe how the timing changes.

The black curved hose make sure the port you use is open, I seem to recall having to drill it open.

you are correct, do not set timing to 0 at idle, set it at the 3000 rpm value. then observe what the other values are to confirm things.

Great minds think alike, more or less.  The respective vac lines to the distributor both seem to pull about 10-12 in. Hg when they're pulling.  As noted above, they resound to throttle in different ways.  Vacuum on the advance line is negligible at idle but builds as the throttle is opened.  This is reflected in the total advance at 3000 rpm, as it should be.  The retard line seems to work in reverse - it pulls at idle and vacuum goes down as throttle is opened.  I'm assuming that this is also as it should be.  Regardless, it's clear that the advance is indeed working and responding as it should.  Of that I have no doubt.

Here's the great minds part.  I don't have a Mitivac, but I do have a small electric vacuum pump (as for evacuating an AC system).  I set it up on the retard port with a T going to a vac gauge so I could see what was going on.  With engine at idle even 20 inches of vacuum on the retard port didn't budge the timing, it stayed put at 10°.   I similarly put the gauge in a T with the retard line and distributor port and know that at idle the distributor is getting seeing vacuum on the port.  So, again, the retard line is working (no leaks and AC swtiching works as a well).  The distributor itself just isn't responding to vacuum on the retard port, whether vacuum is supplied by the engine itself or the pump. 

It's not clear what the cause would be other than a bad advance unit.  It advances but doesn't retard.  I guess I'm looking for confirmation of the logic here.  If it's sound then the solution is to either fix or replace the advance unit, no? 

[rumb]

At this point it sounds like the retard diaphragm is good but the mechanism is stuck. Time for some exploration into your distributor.

[raueda1]

At this point it sounds like the retard diaphragm is good but the mechanism is stuck. Time for some exploration into your distributor.

Thanks.  Before getting too deep I'm reassured when somebody else reaches the same conclusion.  I just pulled it.  Now searching around for disassembly tips . . . . .