Cuts out when hot at idle and difficult to restart.
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simon.williams
- Senior Member

- Posts: 197
- Joined: Mon Jan 20, 2025 11:30 am
Re: Cuts out when hot at idle and difficult to restart.
excuse my french but are these things made of GOLD!
1973 Carmine red 2500PI (work in progress)
1975 Mk 2 Stag (white)
1975 Mk 2 Stag (white)
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2500-Dreamer
- Newbie

- Posts: 19
- Joined: Tue Aug 20, 2024 5:54 pm
- Location: Netherlands
Re: Cuts out when hot at idle and difficult to restart.
Still a lot of money:
https://www.leboncoin.fr/ad/equipement_auto/2144201679

MANOMETRE TEST PRESSION ESSENCE :
Triumph TR5-TR6-2500 PI
Pour tester et régler correctement la pression
d'essence à l'entrée du doseur injection "Lucas MK2".
Mise en oeuvre aisée.
Fourni avec notice très explicite en français.
Prix : 150€ port inclus ( Mondial Relais )
Prix Rimmerbros = 362€ mais indisponible.
https://www.leboncoin.fr/ad/equipement_auto/2144201679

MANOMETRE TEST PRESSION ESSENCE :
Triumph TR5-TR6-2500 PI
Pour tester et régler correctement la pression
d'essence à l'entrée du doseur injection "Lucas MK2".
Mise en oeuvre aisée.
Fourni avec notice très explicite en français.
Prix : 150€ port inclus ( Mondial Relais )
Prix Rimmerbros = 362€ mais indisponible.
2500 MK2 P.I.
1300 T.C.
1300 T.C.
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simon.williams
- Senior Member

- Posts: 197
- Joined: Mon Jan 20, 2025 11:30 am
Re: Cuts out when hot at idle and difficult to restart.
Thanks - might take a punt if coil doesn’t cure it!
1973 Carmine red 2500PI (work in progress)
1975 Mk 2 Stag (white)
1975 Mk 2 Stag (white)
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simon.williams
- Senior Member

- Posts: 197
- Joined: Mon Jan 20, 2025 11:30 am
Re: Cuts out when hot at idle and difficult to restart.
Have removed what look like two pointless capacitors and a black resistor. I had some kind of white brick attached to alternator with a massive spring in it. Assume this is the ballast. Amazed the car runs at all!
Taken the coil off. Was getting 12 volts across it.
I’m hoping that with a new ballast coil I can do away with all of this…
Taken the coil off. Was getting 12 volts across it.
I’m hoping that with a new ballast coil I can do away with all of this…
1973 Carmine red 2500PI (work in progress)
1975 Mk 2 Stag (white)
1975 Mk 2 Stag (white)
Re: Cuts out when hot at idle and difficult to restart.
Hello Simon,
buying a ready made set up will always be expensive.
Pressure gauges come in different quality and hence price.
The pipe work is 1/4" BSP so shop around for a tee with 1/4" male and female ends that you can screw a pressure gauge to.
Yes the white brick is the ballast, if it is in circuit it is probably working. It is easy to make a mistake measuring coil voltage, it will always be battery voltage if the points are open. You need to ensure the points are closed for an accurate reading, i.e. the circuit is under load.
Alec
buying a ready made set up will always be expensive.
Pressure gauges come in different quality and hence price.
The pipe work is 1/4" BSP so shop around for a tee with 1/4" male and female ends that you can screw a pressure gauge to.
Yes the white brick is the ballast, if it is in circuit it is probably working. It is easy to make a mistake measuring coil voltage, it will always be battery voltage if the points are open. You need to ensure the points are closed for an accurate reading, i.e. the circuit is under load.
Alec
0465
MK1.5 2.5 P.I.
Jaguar MK 2 (Long term restoration, nearing completion.)
MK1.5 2.5 P.I.
Jaguar MK 2 (Long term restoration, nearing completion.)
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simon.williams
- Senior Member

- Posts: 197
- Joined: Mon Jan 20, 2025 11:30 am
Re: Cuts out when hot at idle and difficult to restart.
Thanks Alec,
Starting to understand it all. Still not sure if I need a ballast resistor as well as a ballasted coil…but will put one in initially.
Starting to understand it all. Still not sure if I need a ballast resistor as well as a ballasted coil…but will put one in initially.
1973 Carmine red 2500PI (work in progress)
1975 Mk 2 Stag (white)
1975 Mk 2 Stag (white)
Re: Cuts out when hot at idle and difficult to restart.
Hi Simon,
For what it’s worth I bought a small fuel pressure gauge (£30) and plumbed it in using some oil pressure gauge tubing and fittings.
It’s permanently in place in the boot and is small enough that it’s a push fit into the finger hole to lift the section of boot floor over the fuel pump. Consequently I only have to lift the boot carpet to check the fuel pressure. The oil pressure gauge plastic tubing I used is actually long enough for me to fit the fuel pressure gauge on the dashboard but I was a bit concerned about having fuel at 105psi in the cabin.
For what it’s worth I bought a small fuel pressure gauge (£30) and plumbed it in using some oil pressure gauge tubing and fittings.
It’s permanently in place in the boot and is small enough that it’s a push fit into the finger hole to lift the section of boot floor over the fuel pump. Consequently I only have to lift the boot carpet to check the fuel pressure. The oil pressure gauge plastic tubing I used is actually long enough for me to fit the fuel pressure gauge on the dashboard but I was a bit concerned about having fuel at 105psi in the cabin.
Current fleet - 2.5 pi, Jaguar XJ Supersport, Rover 75 Tourer, Lambretta SX200 and Bultaco 350 Sherpa.
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Mike Stevens
- Site Admin

- Posts: 3638
- Joined: Mon May 08, 2006 9:50 pm
- Location: South Oxfordshire, UK
Re: Cuts out when hot at idle and difficult to restart.
Hi Simon,
Even with a 'ballasted' coil you will need the white block resistor. It goes in the wire from the ignition switch to the coil and there should be another wire from the starter motor to the junction between the ballast resistor and the points. That wire provides the full 12V to the coil while the starter is cranking, the theory being that on a really cold morning the battery volts while cranking will drop, maybe even to ~8V! Thus the coil (which is really a 6Vish one) will give a good fat spark. One the engine is running the coil 12V power comes via the resistor which drops the volts down to what the coil is expecting.
I think it's a good system, designed to help starting in a really cold environment.
The 15C6 coil is, I think, a 6V coil, to be used with the ballast resistor. DLB102 looks like the modern equivalent, 1.5Ω primary resistance, for use with a 1.6Ω ballast resistor. see - https://simonbbc.com/Genuine-Lucas-DLB1 ... 8dRBk2Np-Y
ALl the capacitors there are probably to reduce electrical interference to the ICE (in Car Entertainment) - assuming it has one!
Fuel pressure measurement. We plan to be in Normandy at the beginning of March. If that does happen, I could take my gauge with me and post it to you?
Cheers, Mike.
Even with a 'ballasted' coil you will need the white block resistor. It goes in the wire from the ignition switch to the coil and there should be another wire from the starter motor to the junction between the ballast resistor and the points. That wire provides the full 12V to the coil while the starter is cranking, the theory being that on a really cold morning the battery volts while cranking will drop, maybe even to ~8V! Thus the coil (which is really a 6Vish one) will give a good fat spark. One the engine is running the coil 12V power comes via the resistor which drops the volts down to what the coil is expecting.
I think it's a good system, designed to help starting in a really cold environment.
The 15C6 coil is, I think, a 6V coil, to be used with the ballast resistor. DLB102 looks like the modern equivalent, 1.5Ω primary resistance, for use with a 1.6Ω ballast resistor. see - https://simonbbc.com/Genuine-Lucas-DLB1 ... 8dRBk2Np-Y
ALl the capacitors there are probably to reduce electrical interference to the ICE (in Car Entertainment) - assuming it has one!
Fuel pressure measurement. We plan to be in Normandy at the beginning of March. If that does happen, I could take my gauge with me and post it to you?
Cheers, Mike.
(South Oxfordshire)
Register Member No 0355
1971 2.5PI Saloon Sapphire blue
1973 2.5PI Saloon rust some Honeysuckle
1973 Stag French blue
(1949 LandRover which is now back to its original light green!)
Register Member No 0355
1971 2.5PI Saloon Sapphire blue
1973 2.5PI Saloon rust some Honeysuckle
1973 Stag French blue
(1949 LandRover which is now back to its original light green!)
