Car died while driving now won’t start

[18Fiatsandcounting]

Ok…you mentioned earlier a “match book “ measurement….is this the gap between the lobe and the magnetic pick up coil?

Yes, but keep in mind that it's just a rough measurement to get you in the ballpark. One of those shade-tree mechanic tricks of the 1950s through 1970s, mostly a way of getting the ignition point gap roughly correct, but you have an electronic ignition which doesn't have points.

As Spider2081 pointed out, this air gap measurement likely isn't critical. As he noted, you don't want the gap to be too small and run the risk of contact between the lobes and the magnetic pickup, and you don't want it so large that the lobes don't trigger a pulse in the pickup as the lobes sweep by. I don't have much of a feel for this myself, but if you do have a set of feeler gauges (no pun intended), it can't hurt to set it to the spec (0.020" to 0.024").

-Bryan

[Pescado]

Ok…you mentioned earlier a “match book “ measurement….is this the gap between the lobe and the magnetic pick up coil?

Yes, but keep in mind that it's just a rough measurement to get you in the ballpark. One of those shade-tree mechanic tricks of the 1950s through 1970s, mostly a way of getting the ignition point gap roughly correct, but you have an electronic ignition which doesn't have points.

As Spider2081 pointed out, this air gap measurement likely isn't critical. As he noted, you don't want the gap to be too small and run the risk of contact between the lobes and the magnetic pickup, and you don't want it so large that the lobes don't trigger a pulse in the pickup as the lobes sweep by. I don't have much of a feel for this myself, but if you do have a set of feeler gauges (no pun intended), it can't hurt to set it to the spec (0.020" to 0.024").

-Bryan

Hey Bryan…I’m not sure how I would make this adjustment as the magnetic pick coil (MPC) bolts down in a fixed location inside the dizzy and from what I see the lobe isn’t adjustable in that manner either….also how do I get the lobe to line up perfectly with the MPC to take this measurement?

I picked up a timing light today so will do some testing tomorrow and post my findings.

[Pescado]

Good morning,

Below are two links to videos I took showing the issues. Sound quality isn't great but should be helpful.

https://www.youtube.com/watch?v=iLir5Qilrd0

https://www.youtube.com/watch?v=n5nfboVRY6o

[Nut124]

The size of the gap is not all that critical. I think the purpose of the gap is to prevent contact under all circumstances including some future wear on the bushing. The pickup screw holes usually allow for some movement for adjustment.

My guess is that the timing light will show ignition retarded significantly. Wit the light, set timing to 36BTDC at anything above 3500-4000.

[18Fiatsandcounting]

After listening to the videos a few times, I agree with Nut as it does sound like the ignition timing is off. The backfiring through the carburetor is one sign of an ignition timing that isn't advanced enough. So, it could be that the timing is set wrong, or it could be that the ignition advance mechanism is not working.

Try this simple test: Loosen the hold-down nut on the distributor base, and turn the distributor counterclockwise just a bit (as you're looking at it from the top). Perhaps just a 1/4" or 1/2" at the outer circumference of the distributor cap. Retighten the hold-down nut. Turning the distributor counterclockwise advances the ignition timing. See if the engine runs any better. If it is better, try advancing a bit more. If it's worse, try turning in the clockwise direction, but be careful not to go too far in either direction, and it would be a good idea to mark where you started from.

Good on you for getting a timing light, as this is one of those basic tools that is pretty much a necessity. Perhaps that will shed some light (so to speak) on what's going on. Let us know if you need help using it.

From the videos, it also sounds like you might have an exhaust leak at the exhaust manifold/downpipe, but let's start with the timing first.

On the plus side, your engine does have a nice burbling sound!

-Bryan

[Pescado]

Hey guys...so before I start making adjustments here is where I'm at with the timing. Below is a picture I took while shining the light, you can see the timing mark above the top notch. Just realized that this was done with the vacuume hose still connected to the advance on the dizzy and check hose was pinched close.

[18Fiatsandcounting]

Ah-ha! Thanks for that picture. It looks to me like the timing is too retarded. If I am looking at the picture correctly, the triangle mark is TDC, the first mark slightly below it is 5 degrees before TDC, and the second mark below that is 10 degrees before TDC. Depending on the year, the timing can be anywhere from TDC to 10 degrees BTDC, although most people find these engines run best at around 10 degrees BTDC at idle.

Does the timing advance when you rev the engine? The notch on the crankshaft pulley should move as you rev it, maybe a total distance of two inches or so. That's not very precise, but you want the maximum advance to be around 36 or 37 degrees BTDC at 4000 rpm or so, and you just have to estimate this since there are no marks.

I forget the exact procedure with the vacuum distributor advance setup, but I seem to recall that you disconnect the vacuum tube to the distributor and cap it off as you measure the timing at idle.

-Bryan

[Pescado]

oh my! what tool could possibly loosen the dizzy mounting nut...nothing fits in there. I guess I need a right angle 17mm wrench?

[18Fiatsandcounting]

Yes, that lock-down nut is 17mm, but I'm surprised you can't get a normal wrench in there. Open ended, not the box end. If you have the tool kit that came with the Fiat, the 17mm wrench in that also fits.

-Bryan

[Pescado]

Hey guys...happy to report that the car is driving much better . The details...so the first picture is at idle the second is at 3000rpm. The first time I went out the car did sputter at 3500rpm in second gear and also in third. The second time out the car ran better with no sputtering even at 4000rpm. When looking at the pictures the timing mark doesn't appear to advance much...should I still be making adjustments?

[Pescado]

Hey guys...happy to report that the car is driving much better . The details...so the first picture is at idle the second is at 3000rpm. The first time I went out the car did sputter at 3500rpm in second gear and also in third. The second time out the car ran better with no sputtering even at 4000rpm. When looking at the pictures the timing mark doesn't appear to advance much...should I still be making adjustments? So far have turned the dizzy ccw a total of 1/4".

[18Fiatsandcounting]

When looking at the pictures the timing mark doesn't appear to advance much...should I still be making adjustments?

Progress, Pescado! There should be a definite difference between idle and 3000 rpm in terms of the timing, so it appear that your advance mechanism inside the distributor is not working. It could be that the mechanism is frozen, or it could be that the vacuum advance unit is stuck and preventing the mechanism from advancing. An engine with an ignition timing that is stuck in one place will work, but it will be far from optimal in terms of power, smoothness, fuel economy, etc. Not where you want to be.

Just for reference, it appears that your timing is around 16 degrees BTDC, which is high for idle (but OK for now) and low for higher rpms. At 3000 rpm, it should be in the low 30s BTDC, which would be about twice the distance from the large triangle pointer as it is now.

When you rev the engine while shining the timing lights on the marks, the crankshaft pulley mark should move smoothly counterclockwise as you rev, then settle back down to the original spot when the engine returns to idle.

-Bryan

[Pescado]

When looking at the pictures the timing mark doesn't appear to advance much...should I still be making adjustments?

Progress, Pescado! There should be a definite difference between idle and 3000 rpm in terms of the timing, so it appear that your advance mechanism inside the distributor is not working. It could be that the mechanism is frozen, or it could be that the vacuum advance unit is stuck and preventing the mechanism from advancing. An engine with an ignition timing that is stuck in one place will work, but it will be far from optimal in terms of power, smoothness, fuel economy, etc. Not where you want to be.

Just for reference, it appears that your timing is around 16 degrees BTDC, which is high for idle (but OK for now) and low for higher rpms. At 3000 rpm, it should be in the low 30s BTDC, which would be about twice the distance from the large triangle pointer as it is now.

When you rev the engine while shining the timing lights on the marks, the crankshaft pulley mark should move smoothly counterclockwise as you rev, then settle back down to the original spot when the engine returns to idle.

-Bryan

Ok ill do some more testing, i did notice the mark advancing but it did then settle back at which point I snapped the picture...thanks again to everyone for helping.

[18Fiatsandcounting]

Nut knows a lot more about this than I do, but I looked it up for a '79, and it should be:

10 degrees static advance (at idle with the vacuum advance disconnected)

10 to 15 degrees or so of vacuum advance (if your vacuum advance was connected, maybe that's why you were seeing around 16 degrees). The reason for the variation is whether you have a carbed California engine, carbed 49 state engine, or fuel injection.

28 degrees of centrifugal advance (depends on engine speed)

Try again at idle, but make sure the hose to the vacuum diaphragm on the distributor is disconnected and plugged. Turn the distributor until you get it at 10 degrees BTDC. Test to make sure the timing mark moves around as you rev the engine. Don't forget to retighten the distributor hold-down clamp when done.

By the way, idle should be 850 rpm for a manual transmission car.

-Bryan

[Nut124]

Pescado, what kind of a timing light did you get? Some allow you to dial in an advance in the light so that you always just look at the TDC marks.

From what I read and your pictures, it seems that your dizzy is not advancing timing as it should.

If you remove the dizzy cap and examine the rotor, what do you find?

The rotor should turn easily by hand some 45(?) degrees. This is the mechanical advance. The two springs should then always return the rotor to the position where the counter weights are all the way in. This position should be the idle timing. As rpm increases, the counter weights swing out and advance the rotor some 27 deg (crank deg) from the idle position.

The springs may be missing or out of shape.

When working correctly, at idle, timing w/o vacuum hose is about 10BTDC. It then increases to 36-36 by somewhere 3500-4000. Never exceeding 38. The idle timing is not critical. The 36-38 max is. Less than 30 and the engine feels sluggish. Timing is set at idle assuming that the dizzy is in good working order and provides 27deg mech advance as rpm rises. The combustion event takes time to the point that at higher rpms the combustion must start 36deg before TDC in order to develop max pressure on the piston on the down stroke.

If your springs are weak, then I would set 4000rpm, max timing to like 34 so that low rpm timing is not excessive. If you feel ping/knock at low rpm, reduce timing and/or fix the springs. The springs are hard to find. A new or rebuilt dizzy would be good.