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simon a-b

engine misfire/poor running/coolant issues?

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Thanks Wilf

Was it the coil you replaced or the lumenition?

When I got the car the po had fitted points for some reason. I put lumenition back in so the unit is new.

So when I tested the coil by measuring voltage across the coil I got 6v when running. This suggests to me that there is a ballast resistor in the circuit, do you agree? I couldn't identify the resistive wire particularly but the test result is pretty conclusive I think.

I am tempted to fit a replacement coil to see if that fixes the problem.

The car has a history of coil issues... when it had points the coil exploded (I think because the condenser failed). This prompted me to re fit the lumenition. With lumenition it ran fine on this new coil (including a run from west London to Cardiff). Since then until now the car has been off the road and imported into Australia.

I will do the experiment above to get an indication on fuel delivery too today.

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Ok so this morning I bought a new coil, needing ballast (as the previous one was, it was in fine print on the label). Didn't fix the problem, this one also gets too hot to hold.

So connected to the coil are:

+ve

two from the car loom, I assume the ballasted feed and the full voltage feed. I will do some multimeter testing to determine which is which.

The red wire from the lumenition

-ve

The purple wire from the lumenition

a thin black and red wire that feeds the tacho

I thought that this might be the problem somehow but with it disconnected the missfire still is present.

I dont believe fuelling is the issue, I ran the car to where the problem is very evident, shut it off and then turned the ignition on again. The fuel pump barely ticked, like it does when the carbs are fully primed.

It also seems to be related to the coil in that the problem comes quickly with spirited driving, lots of revs, and more slowly if I take it easy, as if it's the number of sparks delivered that determines when the problem hits.

I will try running the car tonight in the dark to see if there's anything to be seen, but with the coil overheating like this I feel that it must be either the full problem or a contributing factor, it should not get that hot.

Cheers,

Simon

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Well both wires going to the +ve have 12v on them. With either one connected and the car running theres 6v across the coil.

I may have the starter solenoid not connected correctly, both wires giving 12v all the time maybe the problem...

Investigations continue!

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I replaced both after trying both ballasted and non ballasted coils, swapped the lumenition out for another (old) amplifier and still had the issue.

One wire to the coil should be via the ballast, the other is via the starter solenoid which bypasses the ballast but only whilst cranking. Lumenition were reasonably helpful when I queried if there was a known failure scenario that cooked coils but were of the opinion the amplifier part tends to either work or not. They are rather pricey to buy based on the off chance as well. My test ignition came from here http://www.simonbbc.com and seemed too cheap to be any good but has been on for a couple of years now.

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so today...

I established that I wasn't supplying resisted 12v on either connection. And neither of them went anywhere near the starter solenoid.

So I made a wire that went from the other pole of the starter solenoid to the positive of the coil. Tested it with the voltmeter and it delivered 12v when the starter was cranking, but nothing when it wasn't. Looks good.

Then I connected one of my 12v supplies to the coil and tried it. Bollocks, the 12v shorts across to the other wire, down to the pole of the solenoid and to earth. Melted wire... hopefully I caught it before too much damage was done! I realise now that this supply has to come from the 12v that actuates the solenoid... feel like a real idiot.

That happened at the end of the day, when I thought I almost had it cracked. I had a spare bulb holder acting as the ballast resistor (it measured 1 ohm, the real deal should apparently be around 1.5 ohms according to the web) and was very hopeful that I would get a good result.

So next I need to strip back the loom around the melted wire (it's in a branch with the tacho feed only) and make sure it's OK or replace it if it's not. I suppose it would have got hot along the whole length of the wire, not just at the visible end so that might be a real bugger.

Once i've done that, then get hold of a ballast resistor and try that out.

Progress of a sort!

Cheers,

Simon

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So after that bit of bad news:

 

I stripped the loom back and the heat damage isn't too bad.  Since I had two +12v supplies to choose from I've terminated the overheated one to make it watertight and used the other one. 

 

I fitted a 1.6 ohm ballast resistor and a relay to supply 12v when the starter is turning.  With the motor running the voltage is around 8.5v after the ballast resistor, coil only gets warm with extended running.  All good. 

 

I've also burped a bit more as I don't think the coolant circuit is clear of airlocks, I'll keep my eye on this one. 

 

The problem is still there, so I've turned my attention to fuelling.  Although the pump ticks away as I'd expect, I took the hose off at the carbs and diverted it into a fuel cannister.  Fuel is barely trickling out.  The manual states that the pump should be capable of pumping 100l/hour. That's 1.6l/minute.  I don't think the pump is supplying anything like that.  I did a little experiment simulating the rate of flow in the kitchen into a calibrated jug and reckon I'm getting below 750ml/minute, maybe as low as 500ml. 

 

The pump has a regulator mounted to the engine cradle, mine's a S3 not the turbo so the manual is often a bit vague on what the arrangements are. It doesn't have a return pipe to the tank as is described for the turbo cars, so I guess it's more of a restrictor. I've only checked downstream of this device so far, I'll try upstream of it tomorrow. Does anyone have any experience with them? 

 

I've also noted a lack of filters (or not located them), from memory this is a hot issue so I'll fit one somewhere in the system. 

 

So tomorrow I'll check out the points above.  If the pump is still not performing (i.e. it turns out the regulator/restrictor isn't the problem) I'll drain the tanks, remove the pump and see what's what. 

 

From a bit of reading on the forum it seems that the pump uses points to actuate a rod that pushes a diaphragm in and out, and a couple of one way valves.  If the pump has stopped it's normally the points needing cleaning.  Mine's not stopped but isn't pumping as much as I'd expect... I wonder if I have a ruptured diaphragm, are they replaceable? 

 

Cheers All

Simon

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Just a thought but have you tried the pickup unit in the distributor and/or the wire which goes from the pickup to the coil. Mine were failing and replacement cured all my misfire/breakdown problems.

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Full rebuild kits are available for su pumps including points and diaphragms, I think you can get solid state conversions too. I thought su pumps were low pressure and did not need regulators though?

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Agree with jonwat above... Dad took this lot out of my pump..

P1010012-1_zps551f7b29.jpg

I think from inside the pump itself.

Where is the regulator mounted on your engine cradle? I don't recall anything like that on mine, though I do have what I believe to be a non-return valve followed by an inline filter up on the RHS.

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I'll post a pic later, could be a non return valve.  It's a small barrel like metal unit on the right hand side mounted above the top tube of the engine cradle. 

 

All wires to the dizzy and lumenition are good/checked/replaced so I don't think they are the issue, always happy to be proven wrong with a clean running car!

 

Cheers for thoughts and comments

Simon

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So today's work:

 

Removed and stripped the pump.  Some crud but not too bad.  All rubbers/gaskets in good shape.  Rebuilt and refitted, cleared up irritating weep of fuel so a legitmate job off the list. 

 

No change to flow rate.  So then to the unit that I thought to be a restrictor/reglulator, actually a solenoid fuel shut off valve.  Completely non functioning, full of crud.  Removed and bypassed, great fuel flow now. 

Not sure about re-fitting, the S3 has rigid pipe from the pump to this valve, with no chance to insert filters pre pump (you might get one into the supply from the rhs tank but no room for a filter from the lhs tank).  This means any crud passing through the pump will get gathered by the solenoid valve. 

 

Anyway, the problem is still not solved.  So along the way I've corrected an overheating coil, and regained correct fuel flow. 

Next possible culprit is the lumenition.  I fitted this 6 years ago when I got the car, replacing a retro fitted set of points done by the PO.  6 years and if you're lucky 500 miles.  So the unit and its wiring is pretty new.  There was some mention of distributor internals maybe being suspect so I'll read up on that and investigate before I just buy another Lumenition block, but I can feel that coming on!

 

Any other theories?  To recap:

 

Recently set timing, balanced carbs, good fuel flow, coolant circuit looking settled and reasonably bled (good heat out of heater, coolant out of bleed at top of radiator), new plugs/leads...

 

Symptoms are: easy start, good running for a couple of minutes/ 1 k or so, then it feels like running on two cylinders.  clears after sitting for a couple of minutes, then repeat. 

 

This is after a honeymoon period of a couple of weeks when I got it officially back on the road of gorgeous running, pulling clean through the rev range!

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Simon, do you have a clourtune plug? It would establish which cylinders were not firing (no blue flame), if both cylinders are off the same carby you could diagnose further.

 

Another bit of diagnosis is to clip the indicative clamp of a timing light on each lead one at a time. The spark triggers the timing light to strobe; if there is no spark, the light should not go off. 

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No I don't have colourtune, I've heard a lot about them on the forum, I'll look into that.  Problem with the timing light idea is that it's only under load, no missfire when idling...

Cheers,

simon

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A misfires under load conditions is classically related to an ignition fault, something electrically breaking down. In older cars with dizzies, it's usually the coil followed by bad leads or cracked plugs. Sometimes it's a cracked dizzy cap with a nice carbon trace where the crack is.

 

To simulate load, there is a trick to use an old (working) plug and widen the spark gap to about twice the gap and check for a spark on each lead to isolate a bad lead or a bad plug. Ground the plug on the engine and wear gloves / insulated pliers - don't get zapped!

 

Iain

 

Oh I forgot to say - you do realise the blocked fuel shut off valve is designed to energise in an impact to stop the fuel pump spraying fuel from an open line in an accident, just in case you weren't aware. :)

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Simon, do you have a clourtune plug? It would establish which cylinders were not firing (no blue flame), if both cylinders are off the same carby you could diagnose further.

You can do that by pulling the plug leads off one at a time :-)

I also agree with Iran S2 that missing under load is normally due to a fault in the ignition high tension system where the spark finds an easier route to earth because of the increased cylinder compression.

Edited by jonwat

Cheers,

John W

http://jonwatkins.co.uk

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As I said earlier classic symptom of failing distributor pickup and or lead from pickup back to coil.

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Thanks for all the input.  I've just been reading up on other fora with lumenition issues, couple of things to try... apparently the pins on the loom from the dizzy might be a little thin, splaying them very slightly might help.  I'll test the reistance of the coil (new one) to see if it's within the lumenition specs.

 

Does feel to me to be ignition related, but I've clearly not got to the bottom of the problem!

 

Yes I'm aware of the fuel solenoid purpose... if I could get a filter in line between pump and solenoid it would be a no-brainer to replace.  As it is I'm not so sure!  I'll have a think about that one...

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I have a fuel filter each side directly under the tanks straight after the banjo bolt outlets.  On my later n/a esprit the flowlock valve is not to shut of fuel in the even of an accident but to shut it of when the ignition is off to stop it flowing back to the tank or out of the carbs( can t remember which).

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Yes from reading the solenoid valve is actuated by ignition, I'll have to see if I have to wait long for the pump to pressure without the valve in circuit.  Having said that I don't think it was functioning at all!

Have you got a pic of your filters?

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So after some searching on lumenition problems I came across a triumph stag forum post saying the connector between the dizzy and the lumenition box can cause issues.  The reported issue was the connectors not being very positive, suggesting giving them a 'tighten'.  Mine was pretty oily after the oil pressure sender hose split, so I cleaned it all with terminal cleaner spray, and gently eased the female side tighter. 

Went for a drive and really thought I had it sorted, ran really nicely for 60 miles or so.  Good fun. 

Then the missfire was back!

I took the opportunity to pull leads to see if I could isolate anything, and it appears to be caused by the rear cylinders.  Interestingly this coincided with the coolant circuit not running as normal.  When I say as normal, I've replaced the steel expansion bottle with a plastic one, and I can see the feed coming from the little hose on the top of the aluminium pipe.  This issue coincided with the bottle filling up (had been around half full), and the circulation apparently stopped. 

I do think that this problem is being caused by more than one issue... I did wonder if I had to swap out the lumenition ignition box, but now I'm not so sure. 

What should I be looking for in the rear carb? 

Cheers all

Simon

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Hi Simon, have you seen this thread?

http://www.thelotusforums.com/forums/topic/68136-elite-running-rough-breaking-down/

With the exception of the cooling thing, Marks problems seem very similar to yours, like you he seems to be seeing the light at the end...An in depth read may be of benefit

Dave

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Thanks Dave, a good read.  There's no way to be sure about my fuel pump, I suspect that the rear two cylinders may have not been running through lack of fuel as the float bowl appeared to be empty.  Not easy to just try a different/generic pump either with the tapered fittings used on the Esprit. 

 

I've had the pump out and stripped and cleaned it, no way to know if it's failing intermittently apart from swapping it out I guess.  I will look at the connections, from memory they were good positive spade females. 

 

The cooling thing is really pissing me off.  I wonder if I've got the hoses not connected correctly.  I have used a different radiator, which required me to cross over the hoses (the high and low radiator connections are reversed) and used a different header tank, so I may have caused some problem with those additions.  It had been running fine, with the top tube from the aluminium pipe showing good flow back to the reservoir, then the flow just stopped, and the bottle filled up. 

 

Once I got home I put it back up on the ramps with the back high, and cracked the bottle lid.  About a litre of coolant spewed out, and I actually boiled... plenty of coolant in the radiator, fans on at the radiator (not very hot air coming from the fans) and temp still climbing, so no circulation I think. 

 

This is all on top of a good 100kms/60miles of great running!  Oh well.

Cheers,

Simon

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