1800: What does this damaged capacitor do??

[142 Guy]

So many possibilities!

Option 1:

Your B 20E / F should have a capacitor that looks like this mounted on the outside of the distributor.

https://vp-autoparts.com/en/artiklar...0a_b-b30a.html

The black plastic 'plug' fits into the body of the distributor and the points connect to the inside terminal and a wire from the coil negative terminal connects to the outside terminal. If at some point the original capacitor failed and it was not possible to source an exact replacement somebody might have fitted a generic capacitor and just mounted it up by the coil in which case it would have been connected to the negative terminal of the coil.

If you are missing the capacitor mounted on the side of the distributor then the capacitor at the coil would be the replacement. The fact that it is disconnected would result in bad operation and rapid wearing of the ignition points. Replace and re gap your points, install correct capacitor and dispose of the capacitor mounted at the coil.

Option 2:

Just like Option #1 except somebody has installed the correct capacitor on the distributor. Since the coil mounted capacitor is no longer required they just disconnected it. The absence of a proper terminal on the wire and a length of stripped wire makes me think it was a temporary bodge. If you have the correct capacitor mounted on the distributor feel free to dispose of the coil mounted capacitor.

Option 3:

Somebody tried a noise suppression bodge which obviously did not work. Relegate the offending capacitor to the dust bin.

Option 4:

Has your car been retrofitted with electronic / non point (I don't like to say pointless because that has two meanings) ignition system. If so, there is no need for a capacitor and you are free to relegate it to the dust bin.

You have the correct

[Laird Scooby]

Originally Posted by 142 Guy

So many possibilities!

Option 1:

Your B 20E / F should have a capacitor that looks like this mounted on the outside of the distributor.

https://vp-autoparts.com/en/artiklar...0a_b-b30a.html

The black plastic 'plug' fits into the body of the distributor and the points connect to the inside terminal and a wire from the coil negative terminal connects to the outside terminal. If at some point the original capacitor failed and it was not possible to source an exact replacement somebody might have fitted a generic capacitor and just mounted it up by the coil in which case it would have been connected to the negative terminal of the coil.

If you are missing the capacitor mounted on the side of the distributor then the capacitor at the coil would be the replacement. The fact that it is disconnected would result in bad operation and rapid wearing of the ignition points. Replace and re gap your points, install correct capacitor and dispose of the capacitor mounted at the coil.

Option 2:

Just like Option #1 except somebody has installed the correct capacitor on the distributor. Since the coil mounted capacitor is no longer required they just disconnected it. The absence of a proper terminal on the wire and a length of stripped wire makes me think it was a temporary bodge. If you have the correct capacitor mounted on the distributor feel free to dispose of the coil mounted capacitor.

Option 3:

Somebody tried a noise suppression bodge which obviously did not work. Relegate the offending capacitor to the dust bin.

Option 4:

Has your car been retrofitted with electronic / contactless ignition system. If so, there is no need for a capacitor and you are free to relegate it to the dust bin.

You have the correct

Option 5: It was a bona fide attempt at RFI suppression, correctly fitted and a problem occurred due to another ignition component failure. Driver at the time ripped the cable out to prove it wasn't the RFI cap at fault and never bothered refitting.

Also a subtle suggestion for a word different to "pointless" for your approval ^^^^^

[Ron Kwas]

CD;

Good info from all, especially 142g who presented multiple possibilities.

I can add that there is plenty of noise in an automotive E Sys...both Ign, which that Cap was likely installed to quiet down, as 142G suggests, as an Ign Points Cap) and also from sparking brushes in the Charging Sys. If you are getting Ign "singing" into your Sound sys, you can try connecting it to the + terminal of Ign Coil...it won't hurt anything, but will help quiet the Primary down if anything.

Sometimes Ign noise can get into sensitive circuits (like the Tach of an 1800) and cause problems. See: https://www.sw-em.com/electical_circ..._1800ES_Solved!

If interested in noise suppression, see also: https://www.sw-em.com/Radio_Notes.ht...o_Interference

Cheers

[ChasesDragons]

142 & Laird,
The Distributor does carry a shiny capacitor.

I the capacitor on the coil was attached until it came back from a multitude of garages - I would think it got damaged by mistake.

If this carries on winding me up, I might call it a day and just install something like a megasquirt system.

[Laird Scooby]

What exactly are the symptoms, does the engine being cold or hot make a difference, does it start doing whatever after it's been used a while or is it after a short drive, switch off and then restarted? Any other circumstances you can think of (relevant or not) would be helpful.

Just to clarify, it's the D-Jetronic injection and not twin carbs?

[142 Guy]

Originally Posted by ChasesDragons

142 & Laird,
The Distributor does carry a shiny capacitor.

I the capacitor on the coil was attached until it came back from a multitude of garages - I would think it got damaged by mistake.

If this carries on winding me up, I might call it a day and just install something like a megasquirt system.

Then I suggest that you feel free to ditch the capacitor that is currently stranded on you coil bracket.

I have Megasquirt Extra on my B20E and I would never recommend that people rush off to replace their D jet system with Megasquirt. I have been witness to a number of badly done Megasquirt implementations. Aside from badly done home made wiring harnesses, Megasquirt introduces a huge pile of unknowns associated with configuring the fuel system to get the car to run.

I generally advise that if you have a stock or minimally modified engine, stick with the D jet. It was a remarkably well designed system. Most of the problems that occur on D jet equipped cars are due to deterioration of the wiring, dirty contacts in the throttle switch, incorrect adjustment of the throttle switch or dirty fuel systems. A review of Volvo's Fuel Injection Trouble Shooting manual should allow you to diagnose just about any problem with the D jet.

As far as I am concerned, the only game stopper for a D jet system on a stock engine is a failure of the MAP sensor. Absent finding a salvage sensor, the only vendor that I am aware of that offers a rebuild for the sensors is Mercedes Classic and the cost of that would motivate me to convert to Megasquirt or some other system.

[Laird Scooby]

Originally Posted by 142 Guy

Then I suggest that you feel free to ditch the capacitor that is currently stranded on you coil bracket.

I have Megasquirt Extra on my B20E and I would never recommend that people rush off to replace their D jet system with Megasquirt. I have been witness to a number of badly done Megasquirt implementations. Aside from badly done home made wiring harnesses, Megasquirt introduces a huge pile of unknowns associated with configuring the fuel system to get the car to run.

I generally advise that if you have a stock or minimally modified engine, stick with the D jet. It was a remarkably well designed system. Most of the problems that occur on D jet equipped cars are due to deterioration of the wiring, dirty contacts in the throttle switch, incorrect adjustment of the throttle switch or dirty fuel systems. A review of Volvo's Fuel Injection Trouble Shooting manual should allow you to diagnose just about any problem with the D jet.

As far as I am concerned, the only game stopper for a D jet system on a stock engine is a failure of the MAP sensor. Absent finding a salvage sensor, the only vendor that I am aware of that offers a rebuild for the sensors is Mercedes Classic and the cost of that would motivate me to convert to Megasquirt or some other system.

I don't suppose you happen to know the characteristics of the MAP sensor do you? THere are some good generic ones around and also some that can be found in other cars and retrofitted.

Sound advice on the D-Jet too, it's a basic but effective system and usually works very well.

[c1800]

Rebuilt sensors are available. Costly, but weigh that against converting to a new system, in money, and time.

http://irollmot.ipower.com/oscom/adv...Sensor&x=0&y=0

[142 Guy]

If by characteristics you mean the resistance test values on the windings those numbers are in the service manual. I do know that there are different D jet MAP sensors for the different versions / applications of D jet so you cannot pick up any D jet MAP sensor that you find listed on EBay and use it, even if the electrical plug matches up fine and it looks the same. The part number has to match up with your original part number if you are looking for a replacement. I have a link to a website which lists the different D jet sensor part numbers and their applications someplace. If I find it I will post it.

I am not aware of any generic D jet MAP sensors. The MAP sensors on modern EFI cars all tend to be similar being semiconductor devices that typically generate a voltage signal between 0 and 5 volts over their rated pressure range. They may have slightly different slopes to their response line; but, they are all generally linear devices and on aftermarket ECUs like Megasquirt you can pick from lots of different sensors because you can program in the characteristic of the sensor.

I did briefly mull over the idea of using an off the shelf modern MAP sensor to emulate the D jet MAP sensor. It is definitely not easy to do. The modern map sensor gives a linear DC output voltage proportional to manifold pressure. The D jet sensor is a totally different animal. The MAP sensor is actually a transformer with two windings and the transformer core is attached to the sensor diaphragm which causes the core to move back and forth between the two windings altering the coupling between the two windings. The D jet controller applies an alternating excitation voltage to the one winding. The current in the second winding changes as the core moves back and forth and that is the signal that the controller uses. If the D jet controller just sensed an AC output voltage it would be relatively easy to have the output voltage for a semiconductor MAP sensor control the output amplitude of a fixed oscillator to get an AC voltage proportional to pressure; but, it is actually the secondary current that the controller is sensing and designing a variable amplitude AC current source was a little more of a challenge. The final obstacle was that from the circuit diagram it was not clear (at least to me) what the output characteristic was supposed to look like ( the current versus manifold pressure relationship). Not being a D jet engineer or spectacularly good at analog circuit design I think I would have to set up a D jet system on the bench, power it up and measure the actual sensor output as I used a mity vac to change the MAP signal. It was more than I wanted to take on particularly since I no longer had a D jet system which eliminated any potential need.

[Baxlin]

Originally Posted by powen1

Nothing if not connected !

Love it! It reminded me of once taking a broken item into the Parts Dept and naively asking if they had one like it. “If I had, it’d go in the bin” was the response, followed by “but I have a new one if you want it....”