GT6 only runs with the starter engaged

[Paul West]

Hi all,

The car stops running when I release the ignition key. Fires up but then dies. Plenty of fuel so must be electrical but what?

Is anyone familiar with this problem and if so, all suggestions gratefully received.

Many thanks

Paul West

[Wagger]

There are, at least, two answers here, depending upon whether you have a 6v coil with Ballast resistor, or the simpler 12v coil without.

In case of a 12v coil:-

If you have a voltmeter or a bulb with wires on it, connect it to the Fuse that is not permanently live. If you see volts when cranking which disappear when not, you have a faulty ignition switch. Fit another switch temporarily so that you can turn it off. If you use a piece of wire, you could overheat the coil should you fail to disconnect it.

The ballasted system is more complex, but first check that the resistor has not gone high or open circuit. Then it's refer to the diagram time. I'll let others chip in here as my car does not use a ballasted (Blasted) system.

[Pete Lewis]

2 thoughts   failed ballast circuit as said or  just a duff ignition switch its quite common the crank sweep contact wears out 

if you have a meter check there is voltage( around 6-8v) at the coil when just switched ign on .........and also  when you crank it          this seems to have failed 

there is a white yellow wire feeds 12v from the start solenoid to boost the coil  +ve when you crank   this is whats making it try to run when you crank it up

the main ignition feed to the coil is a pink /white built into the harness  it drops the normal ignition feed to the 6-8v 

the coil should have a primary resistance across the terminals of 1.5ohms 

if the coil has been ballast bypassed then the coil needs to be 3 ohm and the white /pink is made obsolete if a base 12v feed has been added 

back to the white pink its connected to a short white off the ign switch  terminal 3 

depends on age you may have a ceramic resistor by the coil rather that a built in wire 

Pete

 

[chrishawley]

Just so I understand the scenario:

Turn ignition to 'start' (position 4) , engine then fires and picks up, but on relaxing the ignition key to 'run (position 3) engine dies immediately. Hope that's correct.

Could be simple: Let's take a pre KE20,000 as the easy example. There are two 12v feeds to the coil. A white comes off the back of the ignition switch and after a journey through the loom is eventually attached the one side of the ballast resistor. This provides the continuous current to the coil (via the resistor) in the running condition. The second wire, white and yellow, comes off the back of the starter solenoid and runs to the other side of the ballast resistor; this provides power to the coil in the cranking condition (and only in the cranking condition). Implication is that the 'white' circuit is open which could be the ignition switch, the wire itself, corroded connections anywhere, or indeed the ballast resistor itself (the coil of resistance wire on the reverse side can fracture after decades of service.

On a post KE20,000 the same principle applies except that the ballast resistor was replaced with resistance wire hiden inside the loom. So now there is a white/yellow wire coming from the solenoid to feed the coil in the cranking condition but the wiring the 'run' condition is white from ignition switch to back of fuse box, then white into the loom where is joins with pink/white wire and the wire in joined to the white/yellow but the join is hidden inside the loom.

Simple diagnostic tests for this would be either;

a) with ignition switch in position 3 (run) check voltage present at +ve terminal of coil. Correct is any voltage 6v or greater.

b) take a fly lead from battery +ve to coil +ve and start car. If runs ok the diagnosis is open circuit as above. But if car runs ok turn off engine pronto (few seconds max) so as to not possibly a fry a 6v coil with 12v continuous.

All that's assuming that the system has not been modded for better or worse, but lets keep it simple for now.

[Paul West]

Thanks everyone.

Put the car back together after a rebuild and used a new Autosparks loom and have had real trouble with the fuse box ( terrible quality). The top spring loaded fuse holder keeps failing so that the windscreen washer motor and headlight flash work intermittently. I have no faith in the unit (as explained to Autosparks who seemed surprised at the failure) and will bypass it by the installation of a proper fuse box by an auto electrician. The earlier mention of the fuse box reminded me of it’s poor quality so I will start by removing and replacing the fuses to hopefully achieve a better connection and then, if ok, track down the fault.

Thankyou everyone for your helpful replies.

Rgds

Paul

[Paul West]

Hi all,

The problem was the fuse holder. I removed and put back the fuses and the car started and ran first time. I suspected this because of the earlier problems I had with it. Chinese made no doubt of poor quality clips. I will contact Autosparks but expect that there is little they can (will) do as the fuse holder is part of the loom. Top money paid for it so to expect it to work properly isn’t too much to ask.

Rgds

Paul

[NonMember]

2 hours ago, Paul West said:

The problem was the fuse holder. ... Chinese made no doubt of poor quality clips.

I don't know that the production quality is the issue here. The fuse holder is a dismally poor design and never worked very well. What's worse is that it's designed and used in such a way that even the unfused circuits (like ignition!) are only powered when the fuses are making good contact.

They can be improved significantly by gently bending the clips inward so they grip the fuse more tightly. This works better on new ones than the 50-year-old originals.