Technical Distributor alignment w/o points

[marcus550]

I replaced the points with a Pertronix kit long ago. Recently, I had to replace the pistons/cylinders and could not get it to run on two cylinders. New plugs, wires, cap and coil and no change. It does fire both spark plugs when I've got them out, but will not run #2 when installed. I replaced the Pertronix with a Hot Spark kit and...no change. Great compression on both cylinders, spark, and fuel so the only thing left is timing.

I've been chasing this for weeks now and I'm fairly certain it's how I installed the distributor. The inductive pickup inside the distributor is attached to the body, so alignment of the body to the shaft pointing at #1 is critical. But where? How do I know the distributor body orientation? I can see the rotor pointing at #1, and the cap and wire for #1, but I just don't know the orientation of the distributor body. What's the trick?

 

[bugsymike]

I replaced the points with a Pertronix kit long ago. Recently, I had to replace the pistons/cylinders and could not get it to run on two cylinders. New plugs, wires, cap and coil and no change. It does fire both spark plugs when I've got them out, but will not run #2 when installed. I replaced the Pertronix with a Hot Spark kit and...no change. Great compression on both cylinders, spark, and fuel so the only thing left is timing.

I've been chasing this for weeks now and I'm fairly certain it's how I installed the distributor. The inductive pickup inside the distributor is attached to the body, so alignment of the body to the shaft pointing at #1 is critical. But where? How do I know the distributor body orientation? I can see the rotor pointing at #1, and the cap and wire for #1, but I just don't know the orientation of the distributor body. What's the trick?

Can you stick your finger in No1 Plug hole and feel it coming up on compression, then when it is near TDC make sure No1 lead is in line to rotor etc.

 

[the hobbler]

Can you stick your finger in No1 Plug hole and feel it coming up on compression, then when it is near TDC make sure No1 lead is in line to rotor etc.

Easier to use a piece of thin stiff wire instead of the finger---it would be a real bugger if you got your finger stuckin the plug hole! Get the number one piston to TDC--align the rotor-arm to number one on the distributor cap---you will be close enough for the engine to start---with electronic ignition you will have to do the final timing adjusment with a timing light. If the compression is good and fuel is supplied, the timing being out would affect BOTH cylinders, not just one; there is something else wrong. Check your tappet settings---on the 500 they are (according to the "book of words") 4thou--COLD.

 

[the hobbler]

Easier to use a piece of thin stiff wire instead of the finger---it would be a real bugger if you got your finger stuckin the plug hole! Get the number one piston to TDC--align the rotor-arm to number one on the distributor cap---you will be close enough for the engine to start---with electronic ignition you will have to do the final timing adjusment with a timing light. If the compression is good and fuel is supplied, the timing being out would affect BOTH cylinders, not just one; there is something else wrong. Check your tappet settings---on the 500 they are (according to the "book of words") 4thou--COLD.

Sorry, 4thou tappet clearance is for the EARLY 500s----on the 'D' onwards it should be 6thou (0.15mm)--still COLD

 

[bugsymike]

Easier to use a piece of thin stiff wire instead of the finger---it would be a real bugger if you got your finger stuckin the plug hole! Get the number one piston to TDC--align the rotor-arm to number one on the distributor cap---you will be close enough for the engine to start---with electronic ignition you will have to do the final timing adjusment with a timing light. If the compression is good and fuel is supplied, the timing being out would affect BOTH cylinders, not just one; there is something else wrong. Check your tappet settings---on the 500 they are (according to the "book of words") 4thou--COLD.

The reason for the finger was to feel the compression, my fingers are too fat to fit down the plug hole . Otherwise the piston could be coming up on the exhaust stroke. A piece of wire will not tell you this.
We also use a hose with a whistle to do the same, but I figured keep it simple.

 

[the hobbler]

The reason for the finger was to feel the compression, my fingers are too fat to fit down the plug hole . Otherwise the piston could be coming up on the exhaust stroke. A piece of wire will not tell you this.
We also use a hose with a whistle to do the same, but I figured keep it simple.

I would of course remove the rocker-cover so that at the same time as checking the compression, I could check the tappets--no1 cylinder rockers both 'loose'--No1 on compression. Don't forget---on the Fiat No1 clinder is at the BACK of the car--Front (timing-chain end) of the engine.

 

[bugsymike]

I would of course remove the rocker-cover so that at the same time as checking the compression, I could check the tappets--no1 cylinder rockers both 'loose'--No1 on compression. Don't forget---on the Fiat No1 clinder is at the BACK of the car--Front (timing-chain end) of the engine.

I agree a much more accurate method though more time consuming. As you say on the firing cylinder both rockers should have clearance.
When I was at college the lecturer taught us how to time an engine with no markings at all including valve timing. This involved having the valves on the opposite cylinder where the piston had reached TDC (No.2 on a twin or 4 when timing No. 1etc. on a 4 cyl.) on the "rock" i.e. inlet one just opening and the exhaust just closing as more exact than both loose. By this method it was possible to time a basic engine from scratch, mind you this was 53 years ago before variable valve timing etc.

 

[Toshi 975]

When I have set up that type of ignition on a 126 engine I get the engine at TDC on the no 1 cylinder firing stroke, have the low tension input in the approximate position that you have and the rotor arm pointing in the same direction. Assuming you have both fuel and spark if the engine will not fire up I try slight advances or retarding the ignition until it fires up then set with a strobe light.

 

[marcus550]

Toshi, I agree. This was my tactic, and I should be able to get this to work! I have had the engine purring and then it dies and won't restart. All new ignition and still, same problem. If I pull the plug on #2, it's wet with fuel and the exhaust is cold. #1 is working as best it can. I rebuilt the Dell'Orto FZD anyway (good thing, the float was totally set wrong.) No difference. Swapped plugs front to back, and then for a new set. Compression is 90psi (new pistons/cylinders/rings/head gasket.) I've second-guessed the valve lash five times now, but I don't see how this could be wrong. I tried loose and tight and landed on .008" intake, .010" exhaust. I'll keep at it since this seems to be the right path. It may just be a bad combination of my guess at timing and my idle setting on the carb. Otherwise, I'm out of ideas.

 

[bugsymike]

Toshi, I agree. This was my tactic, and I should be able to get this to work! I have had the engine purring and then it dies and won't restart. All new ignition and still, same problem. If I pull the plug on #2, it's wet with fuel and the exhaust is cold. #1 is working as best it can. I rebuilt the Dell'Orto FZD anyway (good thing, the float was totally set wrong.) No difference. Swapped plugs front to back, and then for a new set. Compression is 90psi (new pistons/cylinders/rings/head gasket.) I've second-guessed the valve lash five times now, but I don't see how this could be wrong. I tried loose and tight and landed on .008" intake, .010" exhaust. I'll keep at it since this seems to be the right path. It may just be a bad combination of my guess at timing and my idle setting on the carb. Otherwise, I'm out of ideas.

Surely whatever the timing or carb setting would affect both cylinders.
I don't have the compression figures but to me 90psi after a rebuild seems on the low side, though if both cylinders the same, but only missing on one that kind of rules that out?
I know this may sound odd, but with both plugs out, on each cylinder in turn with valves closed can you detect more or less "suction" when turning the engine with a socket on the crank pulley by hand from TDC to BDC, either with a vacuum gauge or basically finger covering the plug hole .
My logic for this is if "suction" poor on one cylinder it may have trouble drawing in the correct fuel/air mix.
A more accurate test would be a "cylinder leak test" or it may be possible with manifold off to check using a Mityvac or similar on the ports.

 

[Goldnrust]

While I appreciate its not likely, you could always try swapping the spark plugs and leads over, there’s always the chance of a dud from new?

 

[marcus550]

Repeated my compression test.
Dry: #1=129psi, #2=116psi
Oil: #1=120psi, #2=131psi
So, adding oil brought #2 up 13psi (no explanation why #1 dropped 9!) This is a new p/c set from FD Ricambi. Of course, yours truly installed them so all bets are off with respect to the quality of installation. Maybe a ring has broken? I swear it ran great for about 5 minutes and then it didn't, and I keep thinking it's something outside the engine that caused it. Because I don't want to tear it apart. Again.

 

[the hobbler]

Repeated my compression test.
Dry: #1=129psi, #2=116psi
Oil: #1=120psi, #2=131psi
So, adding oil brought #2 up 13psi (no explanation why #1 dropped 9!) This is a new p/c set from FD Ricambi. Of course, yours truly installed them so all bets are off with respect to the quality of installation. Maybe a ring has broken? I swear it ran great for about 5 minutes and then it didn't, and I keep thinking it's something outside the engine that caused it. Because I don't want to tear it apart. Again.

Knowing what I experienced with elecronic ignition, I would be tempted to (if you still have the parts) re-fit the 'points' ignition and see if the problem still exists. Static timing can very easily be set up with 'points' by use of a little test lamp. Electronic ignition, of ANY sort, does not like heat, and unique to the 500/126 engine, the distributor is in direct line of the 'cooling' air coming from the engine----usually in excess of the 100C that is the 'wilt-point' for electronic ignition (and condensers). You seem to have carefully gone through all the 'logical' possible caused, so now we have to look at the obtuse.

 

[bugsymike]

Repeated my compression test.
Dry: #1=129psi, #2=116psi
Oil: #1=120psi, #2=131psi
So, adding oil brought #2 up 13psi (no explanation why #1 dropped 9!) This is a new p/c set from FD Ricambi. Of course, yours truly installed them so all bets are off with respect to the quality of installation. Maybe a ring has broken? I swear it ran great for about 5 minutes and then it didn't, and I keep thinking it's something outside the engine that caused it. Because I don't want to tear it apart. Again.

Compression readings better apart from the discrepancy, it is always possible a broken ring or the ring gaps becoming aligned together, hopefully not. Though I can't see those readings causing total failure of No.2 cylinder.
Regarding contact points, I have had distributors give different gaps at different lobes and of course a worn distributor bush/bearing can alter gap as the the revs change so on some makes of vehicle we preferred a dwell meter reading, however I believe you mentioned the problem happened with the electronic ignition set up also and even with contact points unless gap went to almost zero unlikely to cause total misfire on one cylinder.
A vacuum test at the individual inlet and exhaust ports can show a poorly sealing valve or a weak or broken valve spring which may not show on a compression test as the pressure is forcing the valves tighter, that is why I mentioned trying to test, if as the piston goes down comparing the "suction" between cylinders.
I know this pic shows a slightly different test on a cylinder head, but it is the tool I was referring to and if used against the individual inlet and exhaust ports with the cylinder head still on the vehicle, it would be possible to compare readings on both cylinders.
The Mityvac is an American made tool so should be readily available for you, I have used one many times.
As the hobbler says, "you have tried the logical" so now..........
I always say if fixing cars was easy I would have been out of a job for 50 years.

 

[the hobbler]

Compression readings better apart from the discrepancy, it is always possible a broken ring or the ring gaps becoming aligned together, hopefully not. Though I can't see those readings causing total failure of No.2 cylinder.
Regarding contact points, I have had distributors give different gaps at different lobes and of course a worn distributor bush/bearing can alter gap as the the revs change so on some makes of vehicle we preferred a dwell meter reading, however I believe you mentioned the problem happened with the electronic ignition set up also and even with contact points unless gap went to almost zero unlikely to cause total misfire on one cylinder.
A vacuum test at the individual inlet and exhaust ports can show a poorly sealing valve or a weak or broken valve spring which may not show on a compression test as the pressure is forcing the valves tighter, that is why I mentioned trying to test, if as the piston goes down comparing the "suction" between cylinders.
I know this pic shows a slightly different test on a cylinder head, but it is the tool I was referring to and if used against the individual inlet and exhaust ports with the cylinder head still on the vehicle, it would be possible to compare readings on both cylinders.
The Mityvac is an American made tool so should be readily available for you, I have used one many times.
As the hobbler says, "you have tried the logical" so now..........
I always say if fixing cars was easy I would have been out of a job for 50 years.

The thinking behind trying 'points' again is that ALL the electronic ignitions, when they fail, do so fairly immediately---often running for a few minutes then failing again. Mine would work after it had been allowed to cool down, fun for a few minutes then cause VERY poor running and backfiring---allow it to cool and it would go through the same scenario. Took me 4 hours to get home froma trip that had taken me 45 minutes to go (and the engine had run beautifully)

 

[bugsymike]

The thinking behind trying 'points' again is that ALL the electronic ignitions, when they fail, do so fairly immediately---often running for a few minutes then failing again. Mine would work after it had been allowed to cool down, fun for a few minutes then cause VERY poor running and backfiring---allow it to cool and it would go through the same scenario. Took me 4 hours to get home froma trip that had taken me 45 minutes to go (and the engine had run beautifully)

I agree with the hobbler, I am not a great fan of after market electronic ignition systems as when they die you are screwed, but a set of contact points and a condensor can usually get you going again in minutes and for much less expense, plus no tow truck!
Generally a new set of points fitted correctly every 6000 mile service gave reliable use for much less outlay.

 

[fiat500]

I agree with the hobbler, I am not a great fan of after market electronic ignition systems as when they die you are screwed, but a set of contact points and a condensor can usually get you going again in minutes and for much less expense, plus no tow truck!
Generally a new set of points fitted correctly every 6000 mile service gave reliable use for much less outlay.

I agree. After the unreliability and short lifetime of the supposedly, more sophisticated 123 setup, I reverted to original points ignition. At least with that system you can precisely set a baseline timing point. The contact less ignition systems seem to have no way of being sure of static ignition.....or am I missing something?
All of these aftermarket systems still rely on mechanical components, often the original distributor. That carries over the potential for timing inaccuracies even if you may be more certain of a powerful spark. It's nothing like the electronic ignition on modern cars.

 

[marcus550]

I've talked myself out of the distributor rotation as being the primary issue. The cap is notched, so location of #1 contact is fixed to the body of the distributor. The inductive pickup is also fixed to the body of the distributor so these are locked together regardless of how I rotate the assy. Back to my original setup, I can get it to run on #1 only still. I'll pull the engine out and see what I can find. Hate doing a job twice!

 

[bugsymike]

I've talked myself out of the distributor rotation as being the primary issue. The cap is notched, so location of #1 contact is fixed to the body of the distributor. The inductive pickup is also fixed to the body of the distributor so these are locked together regardless of how I rotate the assy. Back to my original setup, I can get it to run on #1 only still. I'll pull the engine out and see what I can find. Hate doing a job twice!

While it is still in one piece have you been able to do any of the tests we mentioned to help pin point the direction.

 

[marcus550]

1. Going back to points. I don't have any of these parts. Points failed me the first week I owned the car 8 years ago. They were the first thing to go.
2. Faulty induction pickup. I tried my original first without any changes, and then bought a different one, both with the same result.
3. Checking for suction at the plug. I can try this next. I have a mity-vac. Haven't attempted to vacuum down a cylinder before, but it's worth a shot. If it leaks, the head is coming off. If it doesn't...the head is coming off anyway as I'm out of ideas.

The big thing I changed from a perfectly running engine to now running on one cylinder is the pistons/rings/cylinders/head gasket. The most likely culprit is there somewhere. I just doubted everything else first, as that's a lot easier to get to.

The whole reason for this endeavor is the 'Sport' 650cc engine I bought from a prominent U.S. supplier was built without snap rings on #1 wrist pin. It bounced back and forth and scored the cylinder down both sides. Oil leaks by and starts oozing out the weep holes in the head. I thought it was just a head gasket.