GTC 374

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Post by scimjim » Mon Dec 30, 2019 2:21 pm

I suppose any 40 year old loom can cause issues, particularly if it’s getting hot as a eureka wine does (I had one go on a GTC) - but they are still available new from the club traders and probably cheaper than an aftermarket system?


Jim King

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Post by gtcse8 » Mon Dec 30, 2019 5:57 pm

Ian I will pull out my old invoice for the Ten I bought to get a decent discount many years ago.
It should have a cross reference listed.
Bloody good price if it fits, last one my Ford dealer had quoted over £100 + vat.

Yes, that`s the correct unit for 2.8 :clap:
Mark


Mark Wilson. See the Beast on youtube under" RELIANT SCIMITAR CONVERSION LOL.,Three Se5a, Se6a, Two Se6b`s,1 & 1/2 GTC`s & not a lot of sense
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Post by monkey135 » Mon Dec 30, 2019 6:32 pm

Great, thanks Mark.


Ian

'83 GTC

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Post by alan.wells » Mon Dec 30, 2019 8:50 pm

Hi Ian,
This info may help you re your 38 DGMS Weber, please not that the jet sizes etc are for a 2.3.
mods please move to technical if you feel necessary.
Regards
Alan
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Post by monkey135 » Sat Jan 04, 2020 11:15 am

Right, got and fitted new ignition module and started first time!! Great news and was super smooth, best since I got the car.

Turned engine off and rolled it out side to get it warmdd up and set up carb properly in better light. Turned ignition back on, started first turn but now running rough, like its missing badly. Is this Eureka wire symptom?

Coil good (tried 2), plugs new, getting spark now, new leads, new ignition module.

Ian


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'83 GTC

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Post by monkey135 » Sat Jan 11, 2020 7:21 pm

Hi, still really struggling so could do with some help.

My main issues are that the engine appears to be missing, I'm pretty certain its electrical as it appears quite random. It's definitely getting fuel etc. It also occasionally seems to not want to start, turns the engine over fine but no spark.

Apologies now for the long post but the history might help someone help me.........

The not starting seems a bit random, I thought it was the ignition module (see previous posts) so I fitted a new one and it started first time and ran incredibly smooth for a very short while. Then literally all I did was turn it off and push it out of the garage to start again in better light and setup the carb a bit better.

When I restarted, it was running very rough again but it did start ok. I ran it up to temperature to see if this sorted it out but it was just as bad warm. Its running really rough like a couple of spark plugs are out or something.

I convinced myself it might be a wiring issue so replaced the ignition loom with a new one from qrg. Started fine but still rough. It stalled as I was messing around with the carb again and then wouldn't restart at all (again no spark).

So to recap from the very beginning..........

Wanting to eleminate a fueling issue right at the start of all this I replaced the fuel filter, emptied the tank and refilled. There was a tiny amount of water in the bottom and a tiny bit of dirt but nothing to worry about. Carb has been off and cleaned, new jets etc. This appears to have made little difference to the way it runs. I also replaced gaskets and put new plugs on all unused vacuum take-offs to eliminate an air leak.

I have put on a new coil, new plugs, new leads, new ignition module, and new wiring loom. These have been one at a time and each time I have substituted back in the old one to confirm no difference. None of this appears to have made a difference to the way it runs, although the ignition module did initially seem to get it starting again. Occasionally and randomly it has seemed to start ok, then not again. As I said above, it once ran very smoothly but this appears unrelated to any specific change made (unless the new engine module fixed all issues then immediately failed again!?!).

So does anyone have any ideas? I'm really struggling now.

I'm left with the only thing I can think of is the ignition switch or something with the distributor?

Could a dodgy ignition switch cause both intermittent starting issues and rough running, misfire?

Ian


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'83 GTC

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Post by Old and Slow » Sat Jan 11, 2020 8:47 pm

Here's a couple of ideas:
The eureka wire probably has its ends crimped onto copper wires, as it is almost impossible to solder to.Could be a loose joint here, although you say you've fitted a new ignition loom.
Is the earth wire between the baseplate and the case in the distributor OK? These can fray/break and cause poor earths, especially as the vacuum advance/retard moves the baseplate back and forth, possibly resulting in intermittent conduction.
Rig a headlamp bulb in circuit in a couple of lengths of wire (to "duplicate" the eureka wire) and then run the wire direct from the battery to the coil and see if this overcomes the problem. Don't run it for any length of time, and to stop the engine you'll need to disconnect the wire with some care, as you will have bypassed the ignition switch
Hope this makes sense, and leads to a solution.
Good luck.


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Post by AJL Electronics » Sat Jan 11, 2020 10:27 pm

Distributer chopper. Do you have access to an oscilloscope?


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Post by gtcse8 » Sat Jan 11, 2020 10:50 pm

Big note to everyone offering advice.
This is Hall/magnetic effect dizzy, no chopper or other "breaker" system and does not even have a Eureka wire as such.
It is a low voltage system and is far more robust/reliable than other systems.

Assuming it`s still on the standard wiring, Ian please confirm ?? then there is little to go wrong, ie no eureka wire, ballast resistor, snake oil etc etc etc :?


Mark Wilson. See the Beast on youtube under" RELIANT SCIMITAR CONVERSION LOL.,Three Se5a, Se6a, Two Se6b`s,1 & 1/2 GTC`s & not a lot of sense
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Post by monkey135 » Sat Jan 11, 2020 11:33 pm

First of all apologies if I say anything stupid as we have now officially reached the limit of my electrical knowledge.

Mark - yes it is on original wiring. Although in the manual I have and the wiring diagram I found linked in this forum there is a reference to a Eureka wire. There is a thick white wire running from module to coil that I assumed was this and I'm sure it's a ballast coil.

AJL - I don't have an oscilloscope.

Is the ignition switch likely to be the problem?

Ian


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Post by AJL Electronics » Sun Jan 12, 2020 7:32 am

In my lexicon, the term "chopper" covers every device that chops the feed to the coil. Magnetic, optical or whatever. Think "Hoover or Biro". :mrgreen:

I think that is most likely where the issue is going to be, the problem is how to test it. Without a sillyscope, your options are limited to substitution really. You can put a strobe onto the king lead and watch that, but it doesn't isolate it down to the chopper alone. you *may* see something useful if you put an analogue meter on the input to the ignition amplifier and rotate the engine by hand or remove the distributer and do it that way.


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Post by monkey135 » Sun Jan 12, 2020 10:23 pm

I didn't have much time today for further diagnosis but couldn't resist trying to start the gtc as I passed it in the garage. Started first time, no need for any throttle at all. Ran it to get warm (still running rough), turned it off. Then same problem, wouldn't start again. Weird.


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Post by French Coupé » Thu Jan 16, 2020 5:35 pm

If the problem is still there, have a quick look at the hall effect trigger inside the distributor. We had a similar problem on Dad's GTC two years ago, it turned out to be wear in the distributor allowing the rotor and the stator to touch, but only when hot.
Unfortunately the only cure we found was a second hand distributor!

The whole story is here: http://www.scimitarweb.co.uk/sgwrs/view ... 4&start=60


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Previously: 1968 Scimitar Coupé, 1972 SE5a.
Now: 1971 MG BGT, 1950 Royal Enfield G, chief mechanic for Dad's GTC.

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