Rebuilding the 308 electronic ignition (SM805A distributor, Marelli AEI200 Ignition)

Sorry for the late reply, the tachs in the 308s with the AEI setup/VR sensor are 4 cylinder tachs expecting a coil kickback pulse (100-200 volts) from the negative terminal of the coil.
• If you are switching to an MSD per bank (two MSDs, one for each 4 cylinder) you need to modify the tach electronics to accept the 12V square wave signal coming from the MSD's tach output wire (grey), the frequency/RPM is the same.
• If you modify the single dist to have one king wire and distribute to both banks, then the output signals frequency needs to be divided by 2 and also the tach electronics modified to accept 12V square wave.

 

Thanks!!

 

I'm replacing the VR sensors on my car.
The usual suspects want almost £80 + Delivery + VAT for each complete unit - i.e. sensor and lead/plug
Or you can buy the sensors only for £30 + Delivery + VAT each and wire them into the existing lead.

Be warned though...
I opted for the cheaper option BUT the sensor is a different shape to the original and is set further back. Meaning that I am having to drill out the base plate so that the sensor can be positioned the correct distance from the wheel. This is a pain. I will then need to solder the cables up to make the join to the existing wiring.

I did some retrospective Googling and the complete units (i.e. sensor and lead/plug - all ready to go) can be bought for half the price listed above. The references I found were:

Brand: FACET
Manufacturer: FACET
Manufacturer Part Number: 8.4961/1
Original Part Number: 8.4961/1
Other Part Number: FAC849611
Part Manufacturer: FACET
Reference OE/OEM Number 1: FACET : 849611, ABARTH : 9939762, FIAT : 9934729, FIAT : 9939762, LANCIA : 9934729, EPS : 1.930.161/1, KW : 430 161/1, MDR : EPS-1930 161, EPS : 19301611, KW : 4301611, MDR : EPS1930161

 

Great tip Andy, too late for us though :-( I heard they are sensitive to EMI so use shielded cable.

 

In the UK, complete VR sensor and lead/connector for £29.95
https://www.ricambio.co.uk/electronic-pick-up-pulse-sensor-fiat-124-131-lancia-beta-croma-regata-lancia-prisma

I'm tempted to ditch what I have just bought and simply get a pair of these. They look exactly like the original.

 

Mr. Alhbln ~~
Back on the dist'y problem after going at carb. rebuilds.
Seems maybe I have a bad VR even though the resistance seems sort of OK on both (please see photo). Bunch of crud on where the 2 wires go into the disty.

Nervous about pulling the dist'y - I think because of a young, childhood bit of stupidity I did to my Mom's brand new car the day she brought it home.

So, thought I'd ask once more. Does this look like a suspect VR even though the resistance is high side but close to OK?
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And, if I need to replace a VR ... that's the one item (unless I missed something) you didn't give part numbers for. I'm in the USA (Texas); would be nice to find a source here.

 

Went ahead and removed the disty, marking things carefully. Good thing, that marking because I forgot you specifically said to mark the base plate vs body so it can be reinstalled in the exact same position. Shaking my head at myself. But I think, since I marked the rotor vs body, I can figure it out.

Attached: photo of the VRs. Rear bank sensor leads look "not so good"

Checked w/ Superperformance but they don't offer a clue as to what shipping to Texas would be. I guess step 1 is to figure out if the VR sensor is really bad.
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The sensors look original and not damaged, if you can measure 780-800 Ohms then the wiring and the coil should be fine. What are the symptoms, how did you find out that the sensors are bad? Did you verify the distance between the sensor and the reluctor yet, if that one is too big then you get a low or no spark.

The easiest way to check the sensor output would be connecting a scope and having a look at the waveform and amplitude (if you have access to a scope).

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Thank you, Adrian

SYMPTOM: Weak spark, rear bank. Good spark, front bank. Swapping the amplifier/coil packs does NOT shift the problem to the front bank.

I have no access to an o-scope.

Stopped everything when I remembered too late you said to mark the position of the bottom plate for identical re-install. Thought today I'd get out a magnifying lens and look for small scratches that would give a clue as to proper orientation. I **DO** (now) recall you warned against this ... but am surprised the orientation matters.

All that corrosion on the rear bank wires doesn't matter (attach #1)?

Will check the 2 gaps as soon as I figure out where the reluctor is. Presume it will be obvious once I pull the top plate.

Have never before had a 308 dist'y apart before, so not sure what to look for in excessive wear on the weights, etc. Anything jump out at you (attach #2)?
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Went ahead and removed the top cover w/ VR plate. See attached. Insulation is completely gone where wires fit into the plastic stay. Also it seems there was a crimp in the wire about mid-way. I'm thinking the factory would not have been this sloppy; this VR probably not OEM. I've owned this car since 1984 and can attest to first time opening the dist'y since then ...but not from '79 to '84.

Guessing you will recommend a new VR. Do you know of a decent supplier in the US (shipping cost)? Another person here recommended a FACET replacement, which is indeed 1/2 Superperformance price .. but do you know if it's OK to use?
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Dang it. "Out of Stock"

 

This "looks like" an equivalent, but is it electronically the same (same # windings, etc.)? Ohms seem OK ...

 

Hi All, just picking up this thread which is amazingly detailed, so thank you.

I have an intermittent fault, loss of power when the engine is fully warm and feel its down to a coil / amplifier. As the originals are no longer available, I've gone through Adrians preferred list of replacements but still not having much luck. I found the Hella amplifiers through www.123spareparts.co.uk at a fraction of the cost of other suppliers, but the code has an additional 1 at the end; HELLA 5DA 006 623-051. Is this still the same as HELLA 5DA 006 623-05? No products found when searching these codes on the Hella website.

Same issue with the coils in the UK. Superformance stock a NGK coil but no information on output or model no etc. Look on the NGK website, and no coil listed.

Any assistance is much appreciated.

 

As long as the wires are not broken, you can still apply insulation, silicone would be easy to handle, or PU coating to restore the wire insulation.

Regarding the weak bank, the first thing i always would check is the distance between the sensor metal tip and the reluctor ring. It should be less than 0.4mm, ideally between 0.25mm and 0.4mm to get the full spark output. Also check the king wires and make sure the distributor cap inside is clean and does not show cracks or damage.

Good luck,
Adrian

 

@Furryballer HELLA 5DA 006 623-051 is fine, this is the same module in a different packaging. There is a photo of the module in post #16.

 

Thanks for confirming. Any experience with the NGK coils? Looks like I can get the Pertronix coil through Amazon in the UK

 

That would be the NGK 48308 coil? It is listed as a replacement of the Bosch 0 221 122 334, but i haven't had one on the testbench yet. Might be worth a try though if you cannot source one of the tested coils, NGK used to have good build quality.

 

Great write up! I have a December of ‘79 (USA model) December 308 GT4 and it’s a points ignition.

 

OK, Adrian, I have perhaps the most basic question of all: how on earth to physically measure gap on these?? Please see photo

The disty is apart (have NOT taken advance mechanism or reluctor off the shaft; bottom plate also on shaft. But the top plate, with VRs, is separate. I am using the disty body as a stand (upside down) and have the bottom plate sitting on it. I then have the top plate nestled down on the shaft so the VRs are at "reluctor level".

But there is enough play in the bushing or bearing of the top plate that I can easily tilt the alignment so the VRs hit a reluctor leg ... and then tilt it in the other direction so the other VR hits. I can get the top plate to where the shaft spins w/o VRs hitting, but it's not at all stable - letting go again causes one or the other to hit.

So I don't see how I can figure out the actual gap for either VR in this way.

So how do you physically get a feeler gauge in there and measure what the gap really is when the top & bottom plates are parallel (like when back in the disty body)?
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They are showing now as 'In Stock' - but I'd check with them first.

https://www.ricambio.co.uk/electronic-pick-up-pulse-sensor-fiat-124-131-lancia-beta-croma-regata-lancia-prisma

 

THANKS, Andy!

I've been stuck on how to physically measure the gap - 2 weeks now. You have done this? Did you have to remove the lower plate & advance mechanism from the shaft (pressed on?)?

 

No idea how an expert would do this.

I used trial & error.
I simply kept moving the sensors closer to the vanes until they started to touch when the dizzy was assembled & rotated. Then backed them off a bit. When you rotate the dizzy you can feel the magnetic force at the 8 specific points.

A more technical solution would be to make a disc up equal to the outside diameter of the vane + the necessary gaps (2 x 0.4mm?) put this on a spindle that sits square in the base of the dizzy. The sensors could then be adusted to just touch this disc. An idea I had but never executed.

 

You apparently found a way to get a feeler gauge in there and get a measurement. I don't see how.

When the disty was all together the shaft spun freely, though I couldn't really feel the 8 'resistance points' you guys mentioned. Probably me not being sensitive ...

I now have the dist'y in 3 pieces:
1. TOP plate (with VRs)
2. Shell or body (empty)
3. Bottom plate, with shaft, advance mechanism, reluctor

So, with the shell set aside I put the shaft fixed to the bottom plate,etc into the top plate/VRs. OK, nice, easy access to measure gap. EXCEPT THAT there is enough wobble between the top plate & bottom plate that by pressing gently on one side the reluctor hits one VR; by pressing gently on the other side of the bottom plate the reluctor hits the other VR. By pressing JUST RIGHT I can get the shaft/reluctor to spin without hitting either VR, but it's not a stable positioning. And I sure don't know if it mimics the positioning of the plates (and thus VRs & reluctor) when installed back into the shell. So any measurements are meaningless.

So, I'm kind of stuck. Maybe if I take all the pieces of item #3 (above) off the shaft except the reluctor, maybe I'll get a stable positioning without all that mass? (and are they pressed on, or would rubber hammer tapping get them to slide off after the circlip is removed?) Maybe I have to cut a hole in the side of the shell, then put everything back together and use the hole to get a feeler gauge in)?

Stuck at this point; have no idea what to do. VERY uncomfortable cutting a hole in the shell ...

 

Daniel, you don’t need feeler gauges. Just get the sensors close but not touching, tighten everything up and spin by hand to check the pulses are triggering the coil. It’s a long time since I did mine but no holes are needed— the plates come off the shaft from memory.