1.9 DG miss fire

An alchemy of sparks, copper wire and earth

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T25Convert
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1.9 DG miss fire

Post by T25Convert »

Vans got a bit of a stutter.

Started with the basics (plugs, leads, cap and rotor arm) but no change. It also has a new ignition amplifier fitted by previous owner.

However, using the timing strobe connected to the king lead I noted that there were semi regular missed flashes, which corresponded with the small miss fire coughs.

Earth leads have been off and cleaned, as have all terminals. Dizzy vacuum canister works, and holds vacuum.

So by process of elimination I reckon it can only be either the hall sender or the coil. Coil resistance seems about right. Any other tests I can do to confirm, before I end up committing cash?!
RIP - George - 1.9DG '85 AutoSleeper Trident - rusted away

George Second - 1.9DG '89 Caravelle

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itchyfeet
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Re: 1.9 DG miss fire

Post by itchyfeet »

yes
try a 12v feed direcy to coil to rule out bad wiring on the 12V side.
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T25Convert
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Re: 1.9 DG miss fire

Post by T25Convert »

Cheers, I will make up a fly lead and give it a go.

Is there an obvious point to take the 12v from - back of the alternator +ve output?
RIP - George - 1.9DG '85 AutoSleeper Trident - rusted away

George Second - 1.9DG '89 Caravelle

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itchyfeet
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Re: 1.9 DG miss fire

Post by itchyfeet »

yes or stud in black box

Also don't rule out a dirty plug on the ignition amp or hall sender, you say earth leads off both the one to the engine head and the ones under coil yes?
1988 DG WBX LPG Tin Top
1989 DJ digijet WBX Holdsworth Villa 3 Pop Top
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T25Convert
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Re: 1.9 DG miss fire

Post by T25Convert »

Right, I'm an idiot.

I have spend some time polishing the earth on the head, as it appears from the loom with the dizzy connector, so I assumed this was the earth point for the ignition system .

A quick check in the dark now suggests that I have over looked the rusted lump holding some oxidised wire to mud that sits below the coil and is the actual earth.

I will go and clean this, and see if this is my problem..... If its not the actual issue its really not helping.

Off to hide in a darkened room now.
RIP - George - 1.9DG '85 AutoSleeper Trident - rusted away

George Second - 1.9DG '89 Caravelle

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Ant-t
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Re: 1.9 DG miss fire

Post by Ant-t »

That should do the trick :D
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bigherb
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Re: 1.9 DG miss fire

Post by bigherb »

T25Convert wrote:Right, I'm an idiot.

I have spend some time polishing the earth on the head, as it appears from the loom with the dizzy connector, so I assumed this was the earth point for the ignition system .

It is, the earth under the coil is for the rear lights. The ignition system must always earth to the engine.
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itchyfeet
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Re: 1.9 DG miss fire

Post by itchyfeet »

bigherb wrote:
T25Convert wrote:Right, I'm an idiot.

I have spend some time polishing the earth on the head, as it appears from the loom with the dizzy connector, so I assumed this was the earth point for the ignition system .

It is, the earth under the coil is for the rear lights. The ignition system must always earth to the engine.

mmm Haynes is a bit confusing on this one, can't really recall.
1988 DG WBX LPG Tin Top
1989 DJ digijet WBX Holdsworth Villa 3 Pop Top
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T25Convert
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Re: 1.9 DG miss fire

Post by T25Convert »

I'm not an idiot after all (well maybe I am, but not in regards to this)….

The earth below the coil is for my rear lights (as per BigHerb's advice) so they are brighter now. No change to the running though!

Everything still looked fine, so I chopped the ends of the positive feeds to the coil and remade them, as well as getting another new set of leads and new cap (last set were less than 6 months old). King lead on the old leads broke off in the cap, not sure if it was a faulty or if I was heavy handed.

Not sure which bit of this helped, but the strobe on the king lead now shows constanat pulses with no gaps and the miss fire has gone at idle. Just need to give it a proper test run now.
RIP - George - 1.9DG '85 AutoSleeper Trident - rusted away

George Second - 1.9DG '89 Caravelle

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T25Convert
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Re: 1.9 DG miss fire

Post by T25Convert »

Hmm, still not right. Thought it as the carb (did another post about that), but now think it is electrical.

I have fitted a cheapy aftermarket rev counter which works fine, until over 3000 rpm. Then it bounces around all over the place, when the van stutters.

So, I reckon the stutter is therefore ignition related, as that's where the rev counter is picking up its pulse.

Seems to be worse when the coil has been running at over 3000 reeves for a while, or after a short stop when engine bay temps are up. After time cruising at less than 3000 revs for a while it improves again.

I'm thinking the coil is knackered, can't hack the discharge rate over 3000 rpm, gets warm, then gets worse a step a result of getting warm.

Only thing is, coil does seem to be in spec.

Before I buy a new coil, anyone else got any thoughts? It's got good 12v supply, clean connectors and earth, new ignition module.
RIP - George - 1.9DG '85 AutoSleeper Trident - rusted away

George Second - 1.9DG '89 Caravelle

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T25Convert
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Re: 1.9 DG miss fire

Post by T25Convert »

Or thinking it about it again, is it more likely to be the hall sender??
RIP - George - 1.9DG '85 AutoSleeper Trident - rusted away

George Second - 1.9DG '89 Caravelle

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itchyfeet
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Re: 1.9 DG miss fire

Post by itchyfeet »

can't you borrow a coil off somebody?

if it comes to swapping parts try coil first in my opinion.

worse after running over 3000 rpm implies coil getting hot and breaking down
coils take more current the higher the revs so more heat generated.
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1989 DJ digijet WBX Holdsworth Villa 3 Pop Top
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Re: 1.9 DG miss fire

Post by davidoft1 »

I would suspect the distributor first, but before doing anything runnit at night and see if you can see any sparks jumping

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T25Convert
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Re: 1.9 DG miss fire

Post by T25Convert »

Cheers gents!

Tried the dark trick already, it's worked well in the past for me but this time there is no handy sparks to show me where the problem is.

I'll probably change both out (and then find it's neither!)
RIP - George - 1.9DG '85 AutoSleeper Trident - rusted away

George Second - 1.9DG '89 Caravelle

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T25Convert
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Re: 1.9 DG miss fire

Post by T25Convert »

For my own interest, would this cheap and nasty tool from far far away have any chance of measuring the on-off pulses from the hall sender if I connected it across the coil:

https://www.ebay.co.uk/itm/Portable-Ass ... 0005.m1851" onclick="window.open(this.href);return false;

I assume it would, as only looking to confirm regular on-off switching at around 4 to 20kHz I think - is that right?
RIP - George - 1.9DG '85 AutoSleeper Trident - rusted away

George Second - 1.9DG '89 Caravelle

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