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Discussion Starter #1
I was given an Alfa 33 1.5 ie last year, the car is tatty but very restorable, the only thing I cant sort out is that I have no spark at the plugs, so ive been working through it, replacing components, to date that included distributor, coil, ignition amp, ecu, but still no spark, so then I started testing voltages and resistances etc. My question is: What voltage readings should I have at the distributor 3 contacts when the ignition is on, I appear to have 12volts at the + - and 0 pins, but that seems wrong to me. If it is I know those 3 wires feed straight from the ecu, which I cant test as I cant find any info on it, the ignition amp seems to be doing what its supposed to as does the coil. Also if anyone has any data for testing the ignition system that would be greatly appreciated, I really want to get this car sorted.
934455
 

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Hi,

When the Hall-Effect sensor is disconnected you may get strange readings at the connector.
You've mentioned: "I appear to have 12volts at the + - and 0 pins "
are these measurements referenced to the chassis / ground?

Would it be possible to measure the "0" pin while the plug is connected to
the distributor?
When turning the engine over by hand (while the ignition is on) you should
see as the voltage fluctuates between zero and 5V (if I remember correctly)
when the magnetic flux becomes interrupted/restored in the Hall-Effect sensor.
When this happens the fuel pump should engage also for approx one second.
 

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Discussion Starter #3
"Would it be possible to measure the "0" pin while the plug is connected to
the distributor?
When turning the engine over by hand (while the ignition is on) you should
see as the voltage fluctuates between zero and 5V "

Can i also do this by pulling the distributor out and turning that by hand?
 

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Discussion Starter #4
Would it be possible to measure the "0" pin while the plug is connected to
the distributor?
When turning the engine over by hand (while the ignition is on) you should
see as the voltage fluctuates between zero and 5V (if I remember correctly)
Can i also do this by pulling the distributor out and turning that by hand?
 

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Well yes, but personally I'd avoid that, because you'll need to set the ignition timing
(basic advance) again, plus it is often a pain in the @ss to align the rotor shaft into the right position again in order to fit into the oil pump grooves.

If you engage the 5th gear it is relatively easy to turn the engine over by pushing the car back and forth a bit.
 

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Discussion Starter #6
Hi mate, ok pulled the dizzy before you replied, ignition on, connector on, cap off turned the dizzy, negative probe on battery neg, put positive prob on each contact + - 0 and had around 12v on each and no change when shaft was rotated... im a points and carb guy, this is just way over my head at the moment.
 

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Well this doesn't sounds good...
At least on the "-" terminal you should measure 0V.
This may suggest two things:
1. the wiring between the distributor and the ignition controller unit is
damaged somewhere and shorted to 12V
2. the ignition controller unit has blown (or at least the Hall sensor supply circuitry within)

To test the 1st theory you can disconnect the ignition controller unit connector
and the connector at the distributor. Check continuity (shorts) between the three terminals
of the distributor facing connector on the loom.
If there's no continuity between any of the + - 0 connections the
harness is OK and this suggests failure of the control unit.

If you find short between the + and 0 then the Hall-Effect sensor may be damaged as well.
 

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Discussion Starter #8
Well this doesn't sounds good...
At least on the "-" terminal you should measure 0V.
This may suggest two things:
1. the wiring between the distributor and the ignition controller unit is
damaged somewhere and shorted to 12V
2. the ignition controller unit has blown (or at least the Hall sensor supply circuitry within)
Ok right so i can easily check continuity, can i just ask, when you say ignition control unit do you mean the little 6 pin ignition amp or the ignition ecu on the firewall? and is the Hall sensor supply circuitry the name of the wiring inside the distributor?
 

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This diagram fits.
Under ignition control unit I meant the unit in the intermediate bulkhead area,
behind the battery * it's a black box with Bosch label.

*at least on a LHD 33s, probably the unit is moved to the other side on RHD models together with the battery.

It has a two row connector with 15 pins and marked as "N23" in the diagram.
 

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Discussion Starter #11
Ok, ive already bought a replacement one of those and yes its behind the battery on mine. Is there anyway I can check it out, a specific diagram?
 

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Do you mean specific diagram for the ignition control unit?
Or something else?
(As far as I can tell there's no publicly released service manual / schematics available for the control unit.)
 

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Discussion Starter #13
Ok mate, will have to do some continuity testing first and see where that leads me and do a visual check of the PCB in the ignition control unit.
 
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