Technical Ignition Problems - at wits end

[RDS]

Hello all

More ignition problems leading to me breaking down at "Wits End" with a red hot dry resin coil. Can anyone please shed any light on what's happening here:
1500 1987 car, s135 distributor.

Situation:
last night after 30 mins light town driving I had a misfire (again) then no ignition just having joined the dual carriageway. I pulled in and the new coil was red hot, again. After an hour's cool down I managed to move it with the recovery service off the road but engine sounded ropey.

Backstory and works undertaken:
Previously I had an overheating standard coil so replaced that with another standard oil filled coil, same problem occurred with me breaking down yet again after 20 mins driving.
First and second Coils had 3Ohm primary resistance and 7.5kOhm secondary resistance. Both coils test ok and can generate a spark on a bench test rig however.

I suspected the condenser so replaced it with another generic one of similar microFarad rating and tested it for producing a spark on the bench; it passed these tests. car ran fine on my driveway for about 15 mins before i switched off.

I have replaced the possibly weak battery because cranking was getting slow etc.
I have cleaned up engine earths and earth points on body
I have the brown wire mod
Ignition leads appear relatively new
Distributor cap (brown side exit type) no signs of tracking and relatively new, though you can get a shock if you hold it
Rotor (brown type) has clean contacts and relatively new
Coil and points and condenser are connected up properly, plus radio suppressor to +ve terminal
I had set the points gap to 0.16 per the book spec and timed the engine statically then dynamically to 5 deg BTDC using cyl 4 and checking on cyl 1
Dwell was perfect when set, at 55deg

(An ignition module was tried but without success - see other posts).

Possible contributing factors:
when statically timing, given the limited space, i had to set the points gap by loosening the diz clamp, rotating the body to get a convenient cam and set the gap using that before turning the diz back to its proper place and timing statically. During the static timing procedure, i was getting large sparks off the points as they opened and closed.
Last night, when recovery and I checked the points at the roadside there did not appear to be undue burning but the points faces did not look parallel nor square to each other.
However, the fact remains that surely the coil is getting too much power or for too long even thought the dwell was correct and i happened to check the charging rate as 13.5V just before i set off last night.

Diagnosis:
What's going on here??
Is it just a case of yet another duff condenser? I am not convinced given the problems with the ignition module also.
Some other cause?
Thoughts most welcome.....

Cheers

RDS

 

[NEG]

Your secondary coil resistance seems a bit low, just measured the Marelli coil that came off my 1500 and it measures 3 / 9.5k

55deg dwell is spot on.

Is the coil a 12v one? Not one that requires a ballast resistor? The dissipation at 13.5 volts is around 60w so the coil is going to get hot. Does you multimeter have a 10amp current testing option? Put it inline with the + feed to the coil and check the actual current draw.

How about the ignition leads, do they measure ok around 7k?

 

[RDS]

Hello Neg

thanks for the reply.

the previous coils were 7.5kOhm per the Haynes but the dry resin coil is 20,000Ohms ie 20kOhm and still the problem.

The coil is the correct primary resistance, the ballast one requires 1.5Ohm

Yes, I calculated 48W for the standard 12v 3Ohm resistance in fact but this was red hot.

will do re the ammeter later this week. I will also re-checked the resistance of the leads as i cannot recall the reading but i belive that they were around your figure.

I appreciate your input!

cheers

RDS

 

[NEG]

It’s very odd, check the real current draw and see...where is the coil mounted? Does it need to dissipate heat through a bulkhead or something?

Yes, sorry, dissipation is around 40w not 60w as the points are closed for 220deg of rotation.

 

[RDS]

ok check draw with engine running or stopped (ignition on)?

coil is on engine bay side wall: seems to have louvres on that body panel so I assume it is cooled there sufficiently? Is that the standard location?

 

[NEG]

You can check with engine off, it’s just to see if it’s drawing excessive current. Yes that’s the normal mounting position for the standard oil filled coils, I’m wondering if the resin filled coil needs extra heat sinking that’s all, what was the thinking behind using one vs an oil one?

 

[RDS]

Thanks NEG

ok engine off, ignition on but assume points closed for the measurement. Might try a clamp meter just to see if i get a good reading that way too.

I do not think the dry resin could need any special heat sink eg silicone paste but i have asked the supplier and will post the reply.

I went for the dry resin coil because:
1 the first two oil coils let me down even with a different capacitor and module
2 the price differential was very small between oil and dry resin
3 our friends on the Fiat 500 forum have move over to dry resin cols with good effect.

I really hate chucking parts at a problem to fix it but I felt I had no choice here because my tests were not throwing up a problem (except with one dry coil that had a resistance way beyond 20kOhm and another that just rotated within its own casing).

The trouble is you start to doubt the parts, the tools (multimeter) and of course the installation by yourself even if being methodical

 

[RDS]

Update and further info.

I'd like to change the title of this post from ignition (alone) to reflect the problem eg ignition and/or fuel problems - not sure if that is possible.

Anyway, I thought I’d write with the results of the tests on the Fiat x19 and its cutting out issues and the coil getting very hot.

I have tried many coils, many condensers and one electronic ignition unit. All have resulted in the same result: engine cuts out after 15-20 mins.

Before starting up this time, I re-gapped the points (0.4mm), checked dwell (52deg), idle (900 rpm) and ignition timing (5deg BTDC), re-gapped the plugs (0.7mm), checked plug leads for resistance (6.96 to 8.3 Ohm), checked battery at rest 12.75v. All the above is within spec.
As the points faces were not parallel or square, I re-positioned them to be so.
I checked for resistance between engine block and body: 0Ohms
Plugs are tan on outside pair, a little blacker inside pair but noting untward.
Plug lead connections are good.

I then measured current draw at coil with points closed, meter in series on the 10A terminal: 3.7A
With engine running the average draw was 1.6A , and so at 3.7a x 52/90 = 2.13A , but this is a little lower than expected mathematically but still acceptable.

I fitted another capacitor which I had bench checked and the car did start.

I fitted auxiliary ballast resistor between ignition switch and + coil terminal as the dry coil is rated at 2.7Ohm rather than the factory spec 3Ohm.

I started up and let the car idle with the bonnet up. It was not a hot day by any means but comfortable to be outside, so say 15deg. Again, at 15 mins the fan cut in and the idle became a little lower, but at 20 mins into the run the engine cut out and would not restart. A while later it did start again and ran for 10 mins and cut out again.

I failed to measure the current again (although the resistors were also hot, as I expected) but I think that the issue is not necessarily the coil/condenser. The following possibilities occur to me:
1 after 15-20 mins something is getting too hot that a connection is breaking by reason of a metal moving apart and then re-establishing contact when cooling
2 this is not an ignition or electrical issue at all but a fuel issue. Unfortunately, I cannot establish conclusively whether the cut-off is immediate (like a cut to the ignition) or with a little warning (like a waver upon fuel starvation or condenser failure). There is a waver when the fan cuts in however.

On my following session, I ran the following tests immediately after cut-out:
1 see if a spark is being made at the plugs - neon in line testers indicate that sparks are present even after the stall as seen by assistant when cranking
2 see if cooling the coil rapidly with a cold wet rag re-establishes sparks - did not work
3 see if cooling the fuel pump rapidly with a cold wet rag re-establishes fuel delivery - did not work
4 see if the fuel filter is the correct way round - filter moved round, same result: stall after 20 mins
5 see if the fuel cap has a blocked vent and run engine with cap off (listening for rush of air upon removal) ran car without cap, still stalled after 20 mins
6 see if the float bowl was empty - was lowish but not empty, fuel seen to pass through the filter quickly
7 check fuse box for any visible signs of poor fitting/connection etc - all seemed as it should be
8 fit an auxiliary earth from distributor body to body - not deemed necessary as the resistance between block and body was 0hm
9 apply easy start immediately after stall - car would not restart.
10 shorting out the carb fan operates it and i did test the sender a while back to be ok

Conclusion (false):
as we have sparks and we have fuel, there are not fuel or ignition problems. But that cannot be the case!!

I will re-route the fuel lines along the bulkhead in case there is fuel vaporisation (but fuel lines are not warm to touch and re-shield the coil against external heat soak but I think something else is happening here. What?
i will test the fan again as it did seem to coincide with the engine stalling:
1 disconnect fan but leave sender in place
2 connect up the second fan (hitherto not connected) instead
3 short out the fan sender
4 run a separate wire from battery to coil + in case the ignition switch is at fault.
Are the switches known to loose connection when current flowing?
5 the Moss alarm is somehow cutting current eg via immobiliser after 20 mins.
HOWEVER how can 4 and 5 be the case when i am seeing neon flashes in the inline plus testers?

all practical suggestions welcome (apart from "scrap it!")

cheers

RDS

 

[RDS]

Just tidying up this thread with the current situation as there is a possible correct diagnosis; though i have posted on another thread too:

Update:

stripping back the carb off the manifold reveals the previous owner or the garage (known to me) shows that again they are allergic to gaskets:
Not only the exhaust gasket missing (found out that a while back) but also
no gasket between the bakelite heat shield and manifold
no gasket between the carb base and the bakelite shield
carb retaining nuts finger tight.
yet there was no pick up when spraying engine start around the joints....

I sincerely hope this is the cause of the running for 20 mins then cut out, cool down for 30 minutes, run for 20 mins, repeat....?

cheers

RDS