recent 350 conv. need help with ignition wiring.
 

I just installed a nice little chevy 350 into my 1977 XJ6L. Will start and run, but something is definitely wrong. The engine cranks when the ignition is in the "run" position, and will continue to run even in the off position with the key out. I stopped the engine by touching the negative and positive battery cables. In diagnosing, I discovered that just touching the hot lead from the coil to the + battery terminal, with the ignition in the OFF position, will engage the starter! What is going on, hahaha.

Heres is what I have now:
New Interstate battery.
- Battery cable grounded to engine block.
+ Battery cable to Right firewall post
Starter wire & RED/WHITE from right firewall post to large post on solenoid and to small solenoid inside post
Two Brown wires from the LEFT firewall post going to alternator.
Installed Pertonix electronic ignition
Straight wire from + batt terminal to + coil
+ coil to distributor
- coil to distributor

Is the Jaguar electric circuitry delicate and demanding of doing things a certain way to operate as it should? It didn't behave like this before I pulled the old 4.2 engine out 3 weeks ago.

I did notice that I got a slight shock feeling when i touched the coil while it was running. Have never experienced that before. Do I need a ballast resistor?

I am perplexed at this point. It feels like if I were working on a 1966 Chevelle, it would run perfectly. I swapped an ignition switch that I know is in good working order just to be certain I didn't have a faulty switch. I am doing something wrong and don't know how to move forward.

Thanks in advance for any suggestions or help here.

Basic electrical/wiring principles apply to Jags, and yes it is demanding of doing things a certain way to operate as it should, but that is more to do with electricity than the make of the car.

Where is the start relay in your set up? you dont mention it e.g. That red/white you mention is normally coming from the start relay located centre top of the firewall.

I dont think I can help that much with custom wiring at this distance. The approach I would take would be removing the wiring and starting again, building one system at a time and testing as I go

Yes,.. start over and try to understand :why you are connecting what wire, to where."

Remember there should be NO WHITE WIRES connected to the starter relay.

With key in "start" position, the white/yellow wire from ignition is hot - a trigger wire to energize the starter relay. Also,...You should have a large brown (12V +at all times) connected to the proper position on the relay. A black/green go to ground through the safety switch (P/N).

Do you have the S57 publication?

Your red/white should not be connected to firewall 12V .... It should be on the starter relay....IIRC -when white /yellow wire is hot -(key in start position) it energizes the starter relay and 12V is sent from starter relay on red/white wire to starter solenoid - activating the starter If the red/white gets 12V+ continuously (attached to firewall post)it will activate the starter solenoid continuously.

Diodes!!! I just went through that travail. Essential on the starter relay.
Just why and how, I'm a bit fuzzy. But, it is "back feeding"!!! The crank
wire is getting a signal when it should no longer need it...


Carl

Yes the crank wire is getting a signal when it is no longer needed,.. because the red/white (crank wire) is connected to the firewall post (hot at all times)

I know the care and feeding of Gen 1 Chev engines fairly well. It's really not complicated but must be done a certain way and no other. Here's a basic diagram, which presumes you've used a pre-1975 (non-HEI) distributor:

https://cimg8.ibsrv.net/gimg/www.jag...abba5ce45e.jpg






I don't know the colour or details of the Jag wiring system, but to interface with the Chevy stuff, there should be no unswitched wires going to the coil or distributor. The only constant 12V source would be the positive battery cable going to the large 'B' terminal on the starter (wire not shown in the diagram).

The 'pink' wire in the diagram should be live when the ignition switch is in the on position. The 'purple' wire should be live only when the ignition switch is in the start position. The resistor may/may not be required depending on which version of pertronix you have.

Hope this helps.

Nice artwork! :-) this would be a lot easier for many to understand than a schematic.

Just to clarify, I am not the author. I found it on the 'weeb many years ago.

Thank you to all who commented. To correct and clarify, my White/Red wire does not connect to the positive firewall post. It does come directly off the relay switch located on the inner and upper firewall.
I replaced that starter relay switch, and still have power to the solenoid when the ignition switch is in the run position. I am going to remove the starter and have it tested today, and will give an update as soon as I can.
Also, can any of you tell me if there is a wire coming from the 8 pin wiring loom located on the forward right firewall that would be designated to go to the positive side of the coil? And are any of these 8 wires designated oil pressure or water temperature sending units?
I have tried to keep the wiring so far very simplified, so there will most likely be a simple answer to this current mystery.
Any input is appreciated, and I will follow up with my successful results.

Did you use a Jaguar/Lucas type relay with the W1, W2, C1, C2, etc terminal designations? If so, tell us what wires you have going to which terminal


This would typically be a solid white wire coming from the LH side bulkhead/firewall connector

Yes

Oil pressure will probably be a White/brown wire
Water temp will probably be a Green/blue wire

I say 'probably' because I don't have a Series II diagram....but most of these things have followed a standard British pattern over the years

Cheers
DD

I just posted about pulling the engine management wiring (oil pressure, water temp, tach, etc) from the spot where they enter the front passenger side inner fenderwell. They have been positioned there by Jaguar because the sending units were all in that same general location on the Jag engine.

WIth the Chevrolet engine all of these wiring connections are now at the rear of the engine. So I pulled the ones I needed out of the inner fenderwell an ran them straight to the sensors.

***** ENGINE BACK
------------------------------------------------------------------------------

- Ignition 12V + lead ( hot in Start/Run ) ( WHITE)

"small WHITE at CF2 =extra wire" was originally the white RUN wire to the Jaguar coil

/// ( I am getting 12V + (in start& run) from original Jaguar White
that was at Jag Fuel Pump relay #30.) - ( repurposed wire) ///

/// This 12V power comes from Inertia Switch (and was used to run
to Fuel Pump relay) now diverted to GM MAIN relay --
WHITE (AND FUSED ) ///


**** ( run this wire from CF2 at firewall , across the back of
engine, terminate &cap)
----------------------------------------------------------------------------------------------------------------------


- Tachometer Feed at coil - ( WSU ) ( white/slate/blue)

connect to neg at coil

( run this wire from CF2 at firewall , across the back of engine, to
tach connection - coil wiring)
----------------------------------------------------------------------------------------------------------------------

- Oil Pressure Gauge On engine ( WHITE / BROWN)
Jag pressure sending unit

Use Jag sending unit on 350

( run this wire from CF2 at firewall , across the back of engine,
oil pressure gauge connection)
-----------------------------------------------------------------------------------------------------------------------

- Oil Idiot Light On engine ( BLACK / BROWN ) connect to
GM O/P switch (tan)


( run this wire from CF2 at firewall , across the back of engine,
to oil pressure switch)
------------------------------------------------------------------------------------------------------------------------

****** ENGINE FRONT

- Water Temperature Gauge On engine ( GREEN / BLUE)
Jag water temp unit in GM engine

( run this wire from CF2 at firewall , across the back of engine,
water temp sender)
------------------------------------------------------------------------------------------------------------------------

- Alternator Field Wire ( BROWN / BLACK )


( run this wire from CF2 at firewall , across the back of engine, along driver side of engine, to ALT)
-------------------------------------------------------------------------------------------------------------------------

- AC Clutch Control on compressor ( GREEN / BROWN)
Connect to GM ECM A/C pin

( run this wire from CF2 at firewall , across the back of engine, A/C clutch)
------------------------------------------------------------------------------------------------------------------------


The above are some of my notes to myself Hope they help you

Really thankful for the good information you guys have provided. I swapped another relay on the firewall and designated the correct pin to the starter solenoid. This time it works perfectly. No more starter in the run position, and it turns off with the key, as it should. I got the white wire from the original Jag wire harness in at the front of the right fender to power the coil, and all seems to be in perfect order. I have not tackled the oil pressure, tach, or water temp wires yet as I want to route them in a sanitary fashion. The latest information is so helpful to me as I am not good with diagnosing electronic issues, but once I know where to start, I can figure it out and do it correctly. Stay tuned for another update, and perhaps a few photos of how it comes together.
I really appreciate all your time and effort in helping "new guy".

Glad you got it sorted. Improves the mood to tackle the rest of it :-)

Yeah, the function of a GM ignitions switch and a Jaguar
ignition switch are similar enough, yet different so as to
get one in trouble.


Using the Jaguar S57 schematic to start, then the GM schematic
take one to a solution.


OP, coolant temperature connections, plumbing issues. Adapting Jag
sensors to GM threads.


The tach responds to pulses from the - post on the coil. EXCEPT
The GM is an 8 and the Jag was a 6. Translation required.


And the speedo, oh me.... not there yet.


Carl.

Conversion wiring document
 

I found this old document that shows the length and colors of the wires needed to adapt a GM engine to a Jaguar.