Distributor/timing issue?

[DaveMarcotte]

Hoping for some help.
The long and short of it:
Was running distributor-less ignition before and after engine rebuild for a total of about 5 yrs. Was running great until the Pentronix blew up this passed fall. Bought the 123 ignition and installed over the winter. Even after many emails with vendor and others to ensure I installed correctly, I could never get the car to start. There was weak spark at the plugs but would never start. Last week I ordered and receive from Vick's a new electronic ignition with coil, dizzy and ignition control module. Installed, and car started up!!! Little rough but was expected without the timing setup yet. Got the timing light on it. Set it up at 0 degrees. Seem to be ok. Took it out for a load test. Low on power, bogged down. also, tach doesn't work anymore (jump a couple times but that's it)?

[18Fiatsandcounting]

Is the ignition timing advancing the way it should when you rev the engine? It may be 0 degrees at idle, but it should advance to over 30 degrees when revving.

I know there are no timing marks for this, but I usually set my ignition timing to be 37 degrees BTDC at around 3000 rpm, and pretty much ignore what the timing is at idle. Unless it's way off, in which case there is something else wrong. And 37 degrees is just eyeballing it; it doesn't have to be exact.

If you don't want to try the above, try setting the timing at 10 degrees BTDC at idle and see if that makes any difference.

-Bryan

[RRoller123]

Hey Bryan, how about marking the 37 degree mark on the crank pulley? I have always wondered if the advance was working properly, i.e. going out far enough. There could be sticking, insufficient vacuum, etc. etc. On my 2L, there is "good" (subjective) vacuum at the line, and one can see the mark jump way out, but who knows where it is actually ending up unless we mark it?

On a related issue, I found the factory TDC mark on the new aluminum crank pulley that I abought to be a full 4 Degrees off! That may not sound like a lot, but holy moly, it sure is when one is adjusting at idle. I made a new mark and use that now.

Pete

[DaveMarcotte]

At 10 degree if I rev, it back fires through the carb. Any thoughts on why the tach isn't working? Going to try again after the F1 race.

[18Fiatsandcounting]

Hey Bryan, how about marking the 37 degree mark on the crank pulley?

I agree Pete, that would be great. By the way, what I use is one of those timing lights that you can electronically "retard" the flash with a knob on the timing light. I set the knob to 37 degrees, then adjust the timing so that the mark on the crank maxes out at 0 degrees when revved. When it returns to idle (and the knob on the timing light back at zero), the timing is around 12 oBTDC, about right for my older engines. I always assumed my timing light retard knob was accurate, but maybe not....

At 10 degree if I rev, it back fires through the carb. Any thoughts on why the tach isn't working? Going to try again after the F1 race.

If it's firing back when you advance it, maybe you're getting too much advance? Try retarding the ignition at idle rather than advancing it, and see how it runs. It does sound like you're not getting the right spark advance at various engine speeds.

The older tachs worked by essentially counting the electrical pulses from the points opening and closing and then converting that to a voltage that was displayed by the tach as rpm. The faster the engine speed, the more opening and closing of the points, and thus more voltage to move the needle higher.

With an electronic ignition, my guess is that the tach measures the on-off switching rate of the power transistor that is used in place of the points. I know the Fiat tachs can work with electronic ignition, but I recall a few instances on this forum and others where the tachs behaved erratically.

How do you have your tach wired up? I seem to recall the stock wiring used a brown wire to the terminal on the coil opposite the B+ terminal, the one that would have gone to the points. And definitely NOT to the high voltage plug wire of the coil.

-Bryan

[DaveMarcotte]

Hey
Hope you'll have a look at this video and see if you can see or heard something that can help you help me.
https://www.youtube.com/watch?v=WjHyhgCU8nk

[DaveMarcotte]

You'll is in these photos that it's set at TDC (confirmed through spark plug hole). See the cam pulley aren't quite lined up with the marks on the engine. Are the marking on the engine as accurate as pointers on the front under the cover? Could this be my problem? Thanks again for looking and any input is also appreciated. BTW, they line up perfectly when at 10 degrees on the came.
https://photos.app.goo.gl/yuWhKCMed9mepBGc7
https://photos.app.goo.gl/GhsSetcUrdDaW9Jf8

[18Fiatsandcounting]

Dave, I looked at the video, and it seems to me that your timing is right about 10 oBTDC at idle, but it increases only to 15 to 20 oBTDC when you rev it.

The bottom-most timing mark (the longer one) on the yellow plastic cover is 0 degrees, the one in the middle is 5 degrees and the top-most one is 10 degrees. All Before Top Dead Center (BTDC).

In theory, your idle timing should be around 0 to 10 degrees BTDC (depends on model year), increasing to about 35 degrees or so when you rev it. It doesn't look like you're getting anywhere near that amount of advance, and this is likely the source of your problems.

Advance happens two ways depending on model year: 1) Centrifugal advance only, up until about 1978, and 2) centrifugal plus vacuum advance 1979 and later. I think your 1977 would be centrifugal only, and it could be sticking, or you have the wrong distributor for this model year.

-Bryan