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Weird breakdown story....what are the chances of this - Esprit Chat - The Lotus Forums Jump to content
Peter H.

Weird breakdown story....what are the chances of this

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The big question..... did you pair manage to fix it?

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Only here once

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Thanks Barry, just looking at it now. I may have to put a separate post up for some help. 

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Should be simple surely - James racked some miles up in that car

Is the fuel pump running? Has the cut off switch tripped off??


Only here once

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Thanks Barry

Yes, fuel pump is running when ignition turn.

Other tests I've done (please bear in mind I am pretty much a novice)

TEST 1: No spark at the plugs

TEST 2: No spark at top of the coil.

TEST 3:  When ignition is ON, power goes to +ve side of the coil (tested with multimeter grounded to engine)

TEST 4: The earth on the coil bracket works (tested with a multimeter against the +ve side of the coil with the ignition ON)

TEST 5: Nothing at the -ve side of the coil, even with the engine turning over (tested with multimeter connected to the +ve side of the coil). 

That's as far I got last night.

 

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Thanks Alan, have just done this.

I'm getting 1.5 ohms across the +ve and -ve terminals, which seems within the 0.2 to 4 ohm range suggested.

I'm getting 5,000 ohms across the +ve and the high voltage output, which is just below the 6,000 to 10,000 ohms suggested.

I also tried an old coil I had sitting around...no joy.

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That's one less thing then, good.

I'm not that familiar with NAs, but does it have distributor points or is it electronic? If you've got volts on the +ve coil terminal then that would suggest that the -ve side is not switching to produce a spark. Try taking the -ve lead off, pull the central distributor lead out and put the bare end near an earthing point (engine block will do) with a few mm gap, turn the ignition on then earth the -ve side of the coil a few times. You should get a big fat blue spark at the end of the lead. If you don't then that means the points or ignition pick up are not working correctly.


I tempted fate...now my Esprit V8 IS in bits...(sob)

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Thanks Alan, really appreciate the help.

I always thought it was electronic igniotion. I'll try your test this evening.

I am just wondering if my Test 5 is a pointless test........ i.e measuring voltage across the +ve and -ve terminals of the coil. 

Edited by Peter H.

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5 minutes ago, Peter H. said:

Actually, I am just wondering if my Test 5 is a pointless test........ i.e measuring voltage across the +ve and -ve terminals of the coil. 

Try the above to prove the spark first but if you have no voltage on the -ve at any time that sounds as though it is permanently earthed...


I tempted fate...now my Esprit V8 IS in bits...(sob)

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Actually, just realised I did this test last night....not sure I did it correctly though.  I put a spark plug in the end of the central high tension lead and held it against the engine. No spark.

I did not however disconnect the negative side of the coil. Would this negate the test?

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It doesn't negate the test completely, but does mean that the problem is up-stream of the HT part of the dissy. So, could be any of:

Pick-up in dissy

LT lead between dissy and AB14

AB14 unit (amplifier)

Coil

Wiring between  coil and AB14

Rev Limiter

King HT lead

 

 

Look for the rev limiter and disconnect it ten repeat the test of looking for a spark at the king lead.

. It's a black plastic device, wit the word "Lucas" moulded into it. It has a flat row of terminals, you can trace it by the wires from the coil . In cases of overly-high engine speed, it permanently earths the -ve side of the LT coil, so suppressing the spark generation. They can and do fail (as do AB14s), but have that easy test of when disconnected the car should be able to run (unlike testing an AB14 which is a PITA).

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1 hour ago, Peter H. said:

Actually, just realised I did this test last night....not sure I did it correctly though.  I put a spark plug in the end of the central high tension lead and held it against the engine. No spark.

I did not however disconnect the negative side of the coil. Would this negate the test?

It's not the same test. Do the above but disconnect the negative side and then repeatedly make and break the negative side to earth with a spare wire or a long screwdriver etc. Sparks will rule out the coil, +ve feed and distributor HT lead problems.

Thanks Andy for the more detailed diagnostics, agree that it could be any of those. Methodical Peter, methodical!


I tempted fate...now my Esprit V8 IS in bits...(sob)

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If there isn't any spark, one of the first things I'd do is to disconnect the engine overspeed limiter. It works by earthing the coil.

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Ok, thank you all for this. Really appreciate it and I'll get onto it this evening.

The speed limiter is already disconnected, but out of interest where is the AB14 unit (amplifier) located?

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The AB14 is probably mounted on the body in the driver's side of the boot (My S3 was VERY non-standard), unless you have a box with it and the coil in. 

You can easily find it, look at the dissy and locate the twin wires (blue and orange /brown IIRC) that come out of the ali body near the dissy cap and go to a connector that's a few inches along those wires, they then lead to the AB14 which is a black (painted) metal box approx 4 x 5 inches and 1.5 inches tall.

 

As per Alan's post, you need to be methodical. You  can  start at either end of the cycle (pick-up or the spark plugs,) and work logically to the other end,  you can start in the middle and then keep deciding where to go based on the result, but having ruled out one of the most common component failures the best way is to follow the Lotus diagnostic chart.

https://lotusmarques.com/info/technical/30-lotus-esprit/883-lotus-esprit-s3-electronic-ignition-system

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This is indeed useful. Just a query though, it seems to suggest a maximum 1volt at the +ve side of the coil with the ignition on?!?

image.png.e77a6fbb5ac6a9e2a97604e676c10638.png

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It's not well phrased, it means :

Voltage at 2 (and at 3) should be at least (voltage at point1 - 1v). The full stop after "max" isn't end of a sentence, it's end of the abbreviation, so  written in long hand would be "1volt maximum below voltage at 1"

So, if the battery reads as 13v, then points 2 ans 3 should be  at least 12v.

Edited by andydclements

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Just by way of an update to this story and hopefully a happy conclusion.

I found there was no -ve supply coming back from the distributor and went in search of the AB14 Ignition Amplifier. Could not find it anywhere, so contacted the previous owner who is being extremely helpful. 

Turns out the the AB14 was replaced in favour of an Electronic Distributor which has the electronic ignition incorporated inside it.

The lack of a -ve coming back from this suggests it is faulty and the previous owner is sending a replacement.

By the way, I purchased one of these Power Circuit Testers....brilliant.

Thanks for everyone for all your help.

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