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Jaguar Repair/1973 E-type not starting

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QUESTION: Howard,

 I just replaced my original starter with a modern, gear reduction starter.  It turns the engine over quickly and the engine starts, but as soon as I release the key from start, the engine shuts off.  I know I have ignition because the tailpipes are hot and if I touch the gas while cranking, the engine speeds up.  When I release the key I can hear a clunk, clunk, clunk from the right rear of the trunk, don't know if that's a relay related to the fuel pump but there seems to be gas getting to the engine since it revs so long as the starter is turning.  I should also mention while I was waiting for the starter to be shipped I replaced the spark plugs, ignition wires and distributor cap.  I also lightly filed the end of the rotor.  I've triple checked the firing order of the plugs and their connection to the distributor cap.  Could I have loosened a wire somewhere while I replaced the starter ?  I though about jumpering a wire to the coil positive terminal ?

Thanks again,

Steve

ANSWER: Look at your old starter solenoid to see if it had two small terminals and two large terminals. If it did you had a bypass system to supply a full 12v to the ignition coil and by putting in a different starter it may not have that system.

It is simple to test. Put a 12v test light on the (+) terminal of the coil and turn the key to "ON" (not "Start") and note if you have power with the key in just the "ON" position.

If you do have power to the coil in the "ON" position you need to look at a wiring diagram of your car to see if the fuel pump relay is powered when the key is in the "ON" position and test it.

It sounds like either the fuel pump or the ignition is dropped when you release the key back to "ON".

Let me know,

Howard

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New starter bypass terminal
New starter bypass ter  
Old starter solenoid terminals
Old starter solenoid t  
QUESTION: Howard,

  Your first suggestion was true, there is power to the coil when the starter is cranked but it stops when the key is released to On.  I tried a test light and also put on a jumper from battery positive to coil positive and then the car ran fine.  My old starter only had 2 cables attached to the solenoid but it does have other terminals.  The big top stud held the battery positive and the right phillips held the signal from the relay. See photos.  The new starter does have a 'bypass' terminal - a small phillips screw but I don't know how I would use it ?

 Thanks again,

 Steve

ANSWER: Hi Steve,

The way the bypass system worked is when an ignition system used a low volt coil like a 6v coil and ballast resisotr on a 12v car was that the ignition switch supplied power to the ballast resistor and from the resistor to the 6v coil in the just "ON" position. When you hit the starter (Start position of the sw) the extra small treminal on the starter supplied direct 12v to the 6v coil, bypassing the resistor.
Normally if you applied 12v to a 6v coil it would sooner or later over heat and damage the coil and any electronic ignition system. However while the starter is engaged there is not 12v available. It is usually only from 9v to 11v available so the 6v coil can operate for as long as it takes to start the car. Once the key is released to the "ON" position the starter no longer supplied the 12v to the coil and now the ignition switch was supplying power to a ballast resistor which in turn powered the 6v coil.

With your car I would look at the car and a diagram of your car to see if it had a ballast resistor at one time. Also test that bypass terminal on the new starter to see that it only supplied power while the starter is engaged and as soon as the started is off the bypass terminal is no longer powered.

Now you need to locate the ignition power to the coil (or resistor) when the key is just in the "ON" position. And look at the markings on the coil to see what voltage it is. Also, do you have electronic ignition or points and cndenser (Kittering ignition)?

I will dig through my stuff to see if I have a 73 E-Type wiring diagram. In the mean time look at the coil to ID it and the ignition system inside the distributor to see what you have. It is rare to find a 73 car that is all original.

Let me know,

Howard

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Coil
Coil  

Ignition drawing
Ignition drawing  
QUESTION: Hi Howard,

The coil has 12V marked on the bottom, 13C12, 45234B and perhaps a date of 08 73 !  It sits on top of the 'ballast resistor' as per the stock specs, the coil positive is connected to a White/green wire going to the bottom amplifier side of the resistor aluminum housing - see photo.  According to the manual there should be 3 wires that side but I don't see the top one.  But it may have always been like that - not sure.  The distributor looks stock, electronic ignition, no points, uses the timing rotor and pickup.  I tested the bypass terminal of the new starter - it only lights up when cranking as expected.  The middle red/black wire from the amplifier side of the resistor goes to a harness than runs through the valley and splits to the distributor and then the amplifier near the radiator.  I have the manual, I've attached a copy of the ignition diagram.  I don't see how changing the starter caused this problem since old and new just had 2 wires - to battery positive and start signal from the relay, I must have damaged a wire or caused a short somewhere when I changed the distributor cap or plugs...

Thanks again,

Steve

Answer
Your loss of power with the key in the "ON" position has nothing to do with the starter solenoid or starter.

You must have power to the (+) side of the coil as soon as you turn the key to the "ON" position. Since you have a 12v coil the power must come direct to the coil and not through a resistor wire or a ballast resistor.

Part of the problem is that when a car is as old as the E-Types are now, many people have been changing things.

It sounds like all you need to do at this point is to locate a 12v power wire close to the coil that is powered when the key is in the "ON" position and dead when the key is "OFF" and connect a jumper from there to the (+) side of the coil and that should fix the problem.

Howard

Jaguar Repair

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Howard M. Fitzcharles III

Expertise

Jaguar from the XK 120 to XJ-6 ser. 3 1987

Experience

Dealership line mechanic on MG, Triumph, Jaguar for 15 years, Instructor in commercial mechanics school 2 yr. Product information manager for piston and valve manufacture, Instructor & hotline answer man for import car parts importer 15 yrs.

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Associate member SAE EAA member

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Import Car magazine

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ASE Master Auto with L-1 certification up to 2000

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