Simplified Starter Circuit?
 

Allow me to preface this post by stating that as far as electrical issues are concerned; I'm an idiot.

As some of you know, I'm upgrading many areas of my 1984 XJS (JagZilla) using parts from a wrecked late-year 1989 convertible, which had roughly $30,000 worth of low mileage performance upgrades. The plan seemed pretty simple at the time: I would simply swap out the stock stuff for the go-fast goodies, and wham-bam-thank-you-ma'am, I'd have a faster, better car in about two weeks. Five years later, I'm finally closing in on that goal.

One of the last areas of the conversion has to do with wiring in an Electromotive TEC-1 ECU to replace the Lucas distributor and ECU for handling both the fuel and the ignition duties. As with other areas of this project, the build differences between an 84 and an 89 have come into play - especially in the area of wiring.

The 12 cylinder wiring diagram included with the TEC-1 manual is misleading in it's oversimplification of the task at hand. Even using custom wiring harnesses which the previous owner created for his setup, I have encountered problems with each area of wiring this, and have fought my way through each problem, up to this final issue.
Attachment 73317

The TEC-1 requires the addition of a relay to serve as it's own Main Power Relay in order to fire the 6 coils, and, just as the previous owner had done, I used the stock Main EFI, and fuel pump relays in the trunk (boot) to send a signals to the TEC-1 ECU. So far, when I turn the ignition key I have a fuel pump that comes on and pressurizes the fuel lines, and TEC-1's Main Power relay clicks, which tells me that it is energizing the coils. However, the starter circuit from the 89 won't work for the 84, so no power flows through the starter relay to the starter. Also, there are other things I want to eliminate in the starter circuit.

The starter circuit of the 84 includes a feedback inhibit relay which must be energized before it will send a signal to the starter relay. That arrangement isn't part of the scheme on the 89, but, for good measure Jaguar threw in things like a EFI Main Switching relay, in addition to the EFI Main Relay in the trunk (boot) for the 89 (I guess it was part of the Marrelli arrangement). Both schemes include an inertia switch, and a neutral switch, although they are wired into the schemes differently in each case. I want to eliminate the neutral switch, because a manual transmission doesn't require one. I also want to eliminate the inertia switch, and bypass the differences between having a feedback inhibit relay and an EFI Main Switching Relay, as well as any other unnecessary complications in what I think should be a fairly simple circuit.
Attachment 73315

After studying the schematics for the circuit for both models, I saw that the differences revolved around which relays, components, and switches were connected to the W1 pole of the starter relay. I further noticed that in both schemes, whatever was connected to W1 eventually led to a ground. I figured I could bypass all the complications by simply grounding the W1 pole, so I hooked a jumper wire between it and a good ground & turned the key.

I made smoke :icon_saywhat:

Attachment 73316

Actually, I made heat and smoke in both the neutral "power" lead connected to the C2 pole, and the White/Red wire leading from the C1 pole of the starter relay to the stater itself. However, the starter didn't turn over. Not a click. Not a jiggle.

At least that tells me I had power going to the starter in that configuration. I see that as progress.

Did I create a viable, simple starter circuit, or did I omit a few steps and key components somewhere?

The starter worked when I started disassembling the 89 donor 5 years ago. Other than the possibility that it froze up in that time, why else might it not have turned?

EDITED -- Also, does he fact that the wires heated up indicate that I somehow sent too much voltage through the circuit?

The weather is going to be favorable here this weekend, so I thought I would tap the brain-trust of the forum before having another go at it.

mmmm, this is on a known working starter that is wired properly?

As I stated in my post, the starter worked when I last cranked the motor, 5 years ago. Anything could have happened to it in that time, so I'll be removing it, and having the boys at Autozone check it this weekend.

my bad, I saw that you had been working on it for 5 years, but didn't know if that meant that you hadn't started it at all in that time.
taking the starter out is a pain, let us know how it goes.
If all else is fine your simple circuit should be totally viable

Nah, it's not such a bad job. The hardest part is getting the downpipes off. I've done it a few times, and have all the socket extensions and u-joints I'll need for the task. Pneumatic tools help quite a bit too. Plus, the engine and transmission are clean & grease-free, so that's half the battle right there.

Jagzilla
In principle, a starter circuit needs only a push button switch to feed current to the starter solenoid. If you really want to simplify matters, just wire up a relay circuit that comes live with the ignition key and fit it with a starter button which when pushed activates the relay that energises the solenoid on the starter itself.
Greg

Greg,
I thought about doing that several years back, and I looked into what would be required to add push-button starting. However, it actually complicates things a bit more, because, I would then have an additional relay & associated wiring added to the existing circuit. Also, it occurred to me that if I already have to put the key into the ignition and turn it, why would I want to add the extra step of having to then push a button in order to accomplish the same thing I could once do by simply turning the key?

The modern OEM systems use a proximity switch which is activated whenever the key fob is within a certain distance of the car, and that eliminates the steps of having to insert and turn a key. This was a cool concept 10 years ago, when it was a feature found only on kustoms and exotic supercars, but, now, even the lowly Toyota Corolla offers it, telling me it's pretty played out.

yeah you already have to "push" the key "button".

i suppose you are right scott, I haven't ever taken my exhaust off so just thinking about it makes me cringe. If its all clean and has come off before i guess it isn't too much of a chore

Not to worry. If your pockets are as shallow as mine, and you keep your XJS long enough, you'll be able to do it in your sleep.

Just an update on this project.

I finally got around to pulling the starter today. Took all of maybe 45 minutes.

I took it to Autozone, for testing, and it passed the 1st time, but, the touchscreen on the tester locked up, so, the guy ran the test a 2nd time, and it failed all three portions of the test. The store was out of stock, and their system wouldn't let to special order a rebuilt starter from them, because, their vendor was out of stock.
I took the starter to O'Reilly Auto Parts. Just for grins and giggles, I had them test the starter too. The results were identical to Autozone. It passed with flying colors the first time, but, when I told them to test it again, it failed miserably. They too, had a problem ordering the starter, so had to resort to the internet, and finally purchased one from Rock Auto for less than I could find it locally.

Hopefully, I'll have the new starter by next weekend, and I can test my simplified circuit at that time.

Hi Scott

If I were you I would buy a reduction gear started way smaller, easier to get in and out and sounds great.

Also with your wiring you need to keep the diodes in the relay circuit, these damp the back EMF (spikes) as the relay switches.

Thanks Warren. I did get the gear reduction starter. The engine in JagZilla is from an 89, so the original starter was a gear reduction. I have a perfectly good old stye starter from JagZilla's original engine, but, I would rather spend money on the better starter than to mount that underpowered, slow-spinning boat anchor on the side of my engine.

My jumpered test circuit didn't include the inline diode. I wonder if that had an effect on the demise of the starter motor, or, if the diode simply prevents current from flowing backwards through the circuit. The last thing I need is to short circuit that TEC-1 ECU.

JagZilla, The 'why' an owner would want to install an auxiliary starter switch could be because the switch key circuit quit working as it did on my '96. Another reason would be that no thief could start the engine unless they found the aux switch.
RagJag

No it would not have any contribution to the demise of the starter. The diode is for spike suppression on the relay coil. Without the diode the coil can put high voltage spikes on the 12v supply (it acts just like an ignition coil). So it would be more likely to take out your stereo or ECU.

We can't have that. I could by a dozen or more starters for the replacement price of either of those components.