GT6 that won't start (sometimes)

[patscat]

Hello there you lovely lot, I'm really hoping that the hive mind can help me out.

I have recently bought a GT6 (1974 mk3) that I adore but it is being a bit of a pain.  It keeps cutting out and often won't even start, and I mean not even try to turn/crank the engine.

The details: Bought it from a lovely chap in London and drove it back to Cardiff, that resulted in two unplanned stops on the side of the motorway (in heavy queuing traffic) after a brief cut out before we got to the motorway.  Once cold it started up again fine, just refused to while hot (and in lane 3 of the M4). It's been sitting for a few weeks due to the weather (all covered up) and now won't start at all.  I tried it the weekend before and got the same response from it.  On the dashboard I get a green light and a red one, oil and ignition I think.  I get a tick, that's it, no sign of life from the starter, no attempt to turn the engine.   I'm going to get the battery tested but if we assume the battery is good where do I start? Basically what I need is a 'do this, then try this, then this' list of how to find the issue.  I have a digi multimeter and basic electrical kit.  I also have a new starter solenoid that I haven't had chance to fit yet, the current one is the square type, no rubber button to test the connections. The starter is the standard basic cylinder type (not the new uprated ones).  The distributor cap looks good, pretty new I think but I haven't had chance to check spark plug condition or anything else yet.  

I am a welder and used to be a DT teacher so I'm not daft but do assume that I need things explaining clearly please.  I have owned a few classics in my time (spitfire, capri, lancia beta, allegro (stop laughing now please)) so know my way generally around an engine.  I'm hoping that between you all and the haynes manual I can fix it.  Please could you point me in the right direction?

Thanks in advance,

Jess

[Nigel Clark]

Don't assume the battery is okay just because the oil and ignition lights come on. It could still be a weak battery or poor connections on the battery or engine earth cable. I would get the battery tested and clean the connections before tightening thoroughly. 

That said, while the above would prevent the car from starting, they would not normally cause it to cut out once running. I would be looking carefully at the ignition circuit. The switch works as warning lights come on but try checking all the wiring and connections on the low tension side. Also replace the coil and condenser as these can cause intermittent cut outs. 

Good luck. 

Nigel 

[JohnD]

Pat,

Several problems, I'd say:

1/ Just a click.   Either the starter solenoid, or the battery, as you suspect.    Try shorting the big terminals on the solenoid with a jumper lead, or else direct from battery to starter motor.  If the starter works that points to the solenoid.

2/ no start.    Many more possibilities.   If the starter will turn, then some "Start Ya Barstard" spray can tell if its a fuel or ignition  problem. If it fires with the spray, even for a moment, it's fuelling.

John

 

[dougbgt6]

As john says, jumper leads +ve and -ve. The earth strap, battery to engine may look fine, but be surprisingly non conductive.

You may have to go to Oz to get a can of "Start Ya Bastard!" but there's a pale UK imitation called "Easy Start"

Doug

[Pete Lewis]

two other ideas   battery posts can get a highly insulative coating they need mechanical scouring to clean up what looks like a nice shine  when it needs to be clean lead

check the coil leads are polarity ok  white to pos   black to neg  or the coil gives up at odd intervals just when you dont want to.

the culprit  of many stops  then it starts    and so on till you tear  your hair out 

and do as said  short the solenoid posts with an old screwdriver ...does it crank  ??

Pete

[Paul H]

Suggest  adding a suitable rated cable from the negative terminal on the battery to the solenoid 

Paul 

[patscat]

Thanks for all the replies, it's giving me a good list of things to check. The battery test gave the response 'bad battery, replace' so that's where I'm starting. I think I'll replace the solenoid while I'm at it as I have one.  One other thing I didn't mention as I didn't think it was relevant but one of the sealed beam unit headlights has blown, could that be relevant? I've got new modern headlights to replace the old ones that I'm hoping to do this weekend.

I've attached a photo of the distributor and another part that I don't know what it's called but it's part of the ignition system, it says 6V ballast on it. Could someone explain what that means please? 

Thanks, Jess 

[Gully]

Someone has written 6v Ballast on the ignition coil bracket - that suggests the coil is paired to a ballasted ignition circuit. Essentially, 12v supplied for starting, but 6v feed through a ballast resistor or resistor wire when running. 6v coils are typically c.1.5ohms resistance, whereas 12v coils are c.3ohms.

Gully

[johny]

57 minutes ago, patscat said:

I think I can see at least one of your problems Jess and its a common error with the wiring of the electronic ignition unit you have inside the distributor cap. You have a ballast system which means the coil used works normally at 6v instead of the usual 12v. This is to allow a full 12v to be used when starting the car to compensate for the voltage drop due to the effort of the starter motor turning the engine (especially on cold days). Then once running and with system voltage back to normal the coil is fed through a ballast resistor to only get the required 6v. The yellow/white wire on your coil is the supply wire and as explained only has 6v when running but the previous owner has used it to supply the new electronic ignition unit (red wire) which MUST HAVE 12v. As you can see in the coil (and probably ignition unit) suppliers info the red wire is connected before the ballast resistor to get the correct voltage....

[patscat]

Amazing Johny, what do I need to do/change to get it wired up correctly? Is the ballast resistor essentially wired up the wrong side of the coil? 

[johny]

No I think the ballast resistor side of things is ok but to complicate matters theres two types of resistor. One is a white block with terminals, bolted somewhere (usually the coil) as shown in the info I posted and the other is a resistance wire embedded in the car wiring somewhere so harder to find. If you cant identify the resistor then you wont be able to connect the red wire to the correct side of it (12v side) and will have to find somewhere else to take the supply from. Have a look around and post photos if you like - one inside the distributor would be useful as well...

[patscat]

Will do, thanks. Just so I don't get it totally wrong the coil is the blue cylinder isn't it? I'm off to buy a new battery! I'll keep you posted. 

[johny]

Thats it, the components are in the picture I posted although your wiring is a little different👍

[Pete Lewis]

first observation it this is accuspark  most elec units do need a 12v supply not a ballasted 6v  then have you got the bypass wire from the solenoid 

to beef up the ballaset 6v to 12v when cranking , with a poor battery state you are probably reducing the electronics with less tha 6v  its wont start

your  yellow is the ballasted supply you need to add a12v feed to the guts in the dizzy 

(who's are they)???

Pete

Edited Friday at 15:56 by Pete Lewis

[Ian Foster]

4 hours ago, patscat said:

I'm off to buy a new battery!

Jess

Make sure you don't get one that is too high as the battery clamp and terminals can foul the bonnet reinforcing bars...ask me how I know.

I changed the one I bought for with one having a recess on the front side in which the terminals are located.  The clamp sits over the lowered front edge. See photo.

Ian

 

 

Edited Friday at 20:01 by Ian Foster
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