Distributor Voltage Falling Due To Heat?

[davemar 16]

I'm running an Mi16 engine with the 8v Jetronic setup with the distributor adaptor arrangement. I recently replaced my dizzy as I found the pick-up voltage signal was decreasing while the engine heated up. Eventually the signal got so weak it would only run for a couple of minutes. The replacement unit has been fine for a few months now, but a couple of days ago the ignition cut-out after a longish drive on a warm day. I lacked tools to check anything, but I removed the dizzy to let it cool for 1/2 hour, and sure enough she started up again. I measured the peak-to-peak voltage when I got home (warm engine) and it was 4v. I checked it again the next morning when it was cold and it was 20v, so much higher. So I suspect this dizzy is starting to suffer from the same problem.

 

Has anyone else experienced this problem? I don't want to keep replacing the dizzy every few months, and now I've hard wired a cheapo multimeter across the pick-up connections so I can monitor the voltage in the car. Could the dizzy adaptor be transferring to much heat from the head, or is it just the coils going off? I was also wondering whether the expansion on the rotor/stator (can't remember which) causes the gap to increase making the voltage drop?

 

I'm almost tempted to make a signal booster for the pickup to ensure the ignition amplifier has enough signal.

[Miles 331 1 Cars]

Yes I've seen this a few time's now, Again it's all down to age so buying new is the only route really

[davemar 16]

Yes I've seen this a few time's now, Again it's all down to age so buying new is the only route really

Just checked the price for a new one from Peugeot on servicebox, and it's £370. Ouch!!

 

Is there anywhere I can just buy the pick-up coil inside the distributor on it own? The Bosch website is useless and contain very little useful information.

 

I've been monitoring the rms voltage from the pickup while driving this morning. It started out at 10-15Vrms when cold, but after 5 minutes or so,

it dropped suddenly to around 3Vrms and stayed in the 1.8-3.8V range over the rest of the 40 min drive. I imagine when it gets below 1.3Vrms or so

it'll cut out. So I guess the coil is getting partially shorted after some heat gets in there.

[dani959 0]

I've got a dizzy for spares if you want it. It was working ok (the coil, this is) when I removed it.

It is not complete, I remember I took the springs and the advance weights dry bearings out. Apart from that, everything was fine.

 

yours for, let's say, a fiver plus whatever postage it is.

[davemar 16]

I've got a dizzy for spares if you want it. It was working ok (the coil, this is) when I removed it.

It is not complete, I remember I took the springs and the advance weights dry bearings out. Apart from that, everything was fine.

 

yours for, let's say, a fiver plus whatever postage it is.

I've ordered one off eBay before I read your message, so hopefully that'll be OK. Don't throw your's out though, I might be still interested if this one isn't so good.

 

I've also managed to track down where new coils can be bought: Ignition Parts (third item from the bottom).

 

I'm trying to see how the thing comes apart to get at the coil, but there seems be a circlip that's virtually impossible to remove just below the 4-pointed rotor thing hidden behind the coil. Has anyone every removed one of these?

[davemar 16]

I managed to buy one of those new replacement coils, so I managed to fit in my distributor eventually. It was a bit of a faff getting the thing apart so I could get the coil out, involving rotating a circlip and punching out the pin on the rotor. So I got the thing all fitted and back on the car....and it was still a weak voltage. Only 0.8Vrms on cranking, not enough to fire the amplifier. So could this new coil be designed for a lower voltage output? I checked the waveform both at the end of the connector and right on the two pins on the pickup and they looked fine in waveform shape, but generally a bit on the low side (so it appears the screened cable is OK). I'm really at a loss now to what is going on. Has anyone else got a reading of the signal from the dizzy pick-up, as I'm getting puzzled now?

[mercury 0]

sorry noob question but coul dit be your coil? Are you using an aftermarket coil? If a coil has had it the rings expand during heat and may lose contact with one another.

 

Again dont take this as any experienced mechanic advice, but im about to do the same thing from other advice from other peeps.

 

cheers,

Merc

[davemar 16]

I think the pick-up coil was the original problem as the voltage output it produced did drop suddenly when the engine warmed up. I suspect a winding expands and shorts out reducing the number of turns. The new coil I hoped would solve this problem, but the voltage is still too low. Maybe the new coil is just the wrong specification, rather than broken. I'm not sure whether it is aftermarket or not, whether anyone other than Bosch would bother making something quite so specialised. The two connector pins did need a bit of trimming to get the thing to fit, though the former it was would on was clearly the right one. I might still the various coils I have on an LCR meter to see how their inductances compare. I might even try winding my own coil, as I've discovered a hand-winding machine at work.

[mercury 0]

The two connector pins did need a bit of trimming to get the thing to fit, though the former it was would on was clearly the right one.

 

which 2 pins are you refering to?

 

Cheers,

Merc

[davemar 16]

which 2 pins are you refering to?

 

Cheers,

Merc

 

The pair which the black screen cable connector attaches to the side of the distributor. Unscrew and pull off that connector and you'll see two flat connectors in the oval hole. Those are the connections on the pick-up coil.

 

Unfortunately I'm lacking the dizzy and a camera while work, so can't show you with pictures.

[mercury 0]

The pair which the black screen cable connector attaches to the side of the distributor. Unscrew and pull off that connector and you'll see two flat connectors in the oval hole. Those are the connections on the pick-up coil.

 

Unfortunately I'm lacking the dizzy and a camera while work, so can't show you with pictures.

 

oh you mean this thing?

[davemar 16]

That's the fella, though mine (and all the others I've seen) look different to that. The first picture in the other thread has a picture of the connector. Maybe they make them differently in Oz.

[davemar 16]

Just unwound one of the old coils. 2190 turns - phew. Thanks god for counters on coil winding machines.

 

Started to wind some new wire on, and it snapped 1000 turns in. Bugger.

[davemar 16]

Finished winding the coil, got 2000 turns on there, measured inductance 160mH (the original was 180mH, so not bad).

 

Fitted it back in the dizzy and in the car ... and nothing. Wouldn't fire. The signal at turn-over was about 1.2 Vrms, so I thought that would be enough to kick it into action. There was no signal on the output of the ignition amplifier, so either that has thrown a wobbly, or the signal is still too weak. Next step is the check the wiring and the amp. Grrr.