1971 Lotus 7 series 4 hasn't run in 46 years

[stevehello]

Forty-six years ago I had purchased a used station wagon because I had needed a vehicle to carry tools and building supplies in for my home improvements. Since I couldn’t afford to pay for insurance on two cars, I placed my 1971 Lotus 7 series 4 into a garage. I then removed the dash board switches because they hadn’t been working reliably, but I had tried unsuccessfully to find new switches. Though I had labeled most of the wires in the car, the ink has faded since then so that I can’t read it anymore and, since I had purchased it assembled in 1972, I do not know exactly which wire goes where. Does anyone have the wiring instructions for the car? My wife has been angry that the car has been in her way and so I need to get it running again so that I can again register it with the California DMV. Because the negative wire in all circuits that I have ever seen before has always been connected to a black wire, I placed the black cable to the negative terminal of the battery. Although every other car that I’ve seen has had a red positive cable, this car has a blue cable so I connected it to the plus terminal of the battery. I was happy to see that the starter then could easily rotate the engine in the proper direction though the ignition coil did not produce a spark. I assumed that there is corrosion somewhere, but, when I started to follow the wires, I was surprised to see that, under the car, the blue battery cable is connected to the chassis at the rear of the car. I then downloaded the Assembly Guide (also labeled Owners Guide) from this website. For some reason, it does not show it does not have a wiring diagram of the whole car or a breakout of the wiring cable. I then became concerned when I saw that it does say that a Lotus 7 series 4 has a “negative earth polarity”, however, there is a separate download diagram at this website that shows that the positive terminal is connected to the ground (chassis) and it shows an electric fuel pump (which I don’t have) so perhaps it’s for another model. Now, I am 79 years old and unable to remember 46 years ago as to what color wire had been bolted to which battery terminal. Does anyone know where I can get the breakout diagram of my cars electrical cable or the cars schematic? Does anyone at least know if all Lotus 7 series 4 cars had a negative chassis ground or did the wiring change during the years that the series 4 had been produced (could it have been different depending on which engine was installed?). Though my engines valve cover says Lotus-Holbay on its valve cover, I do not have the twin cam engine shown in the owners manual so, perhaps the manual does not exactly apply to my car. Does anyone else have a Lotus 7 series 4 with a blue cable battery cable that goes to ground and, is it a connected to the positive battery terminal?

It was easy enough for me to buy modern tires and dashboard rocker switches but, the break and clutch cylinders have been left unused for so long, I believe that I should rebuild or replace them for safety reasons; does anyone know what parts I would ask for? Once someone had told me that I should see if 1971 Ford Cortina distributer points will replace the points in my car; is it possible the break parts from that car might also fit my car? This project has become a bit more complicated than I had expected so I would very much appreciate any help that you might be able to give me.

[Carz01]

Hi @stevehellosee if this helps you. @croc maybe add to files too. Thanks!

[SENC]

I believe the switch from positive earth to negative earth occurred with the Series 3, so should have been neg earth in an S4.  I'm away from my manuals at the moment, but will check later to see if I see any specific reference one way or the other.

 

Re other parts, check the Library section - there may be a  S4 parts list there that would be helpful.  If not, I'm pretty sure there are some Lucas catalogs and crossreferences from that time.

Edited Friday at 12:19 PM by SENC

[wdb]

5 hours ago, SENC said:

I believe the switch from positive earth to negative earth occurred with the Series 3, so should have been neg earth in an S4. 

 

That's what the wiring diagram indicates, but I don't know the date on that.

[San Augustine]

The Tony Weale book on the Lotus Seven has a chapter on the S4 with a lot information on the wiring and other mechanical components. It is out of print but copies can be found on Amazon and EBay.

 

https://www.ebay.com/itm/233981728724

 

Here is an article written by him on S4 restoration.

 

https://lowflying.lotus7.club/2006/2006_04_07_7story25.pdf

 

SJ sports cars has a very good selection of S4 parts.

 

https://www.sjsportscars.com

 

If you have a Twin Cam Holbay engine  (which was the top of line S4 offering in 1971) or even if it is a Holbay crossflow  I would check with Ken Gray at Dave Bean Engineering. He would be a good source for info and parts. 
 

https://www.davebean.com

 

More info 

www.lotus7register.co.uk/lss17.htm

 

Love to see some pics of your car. My S4 is a long way from being on the road. So much that I bought a Caterham to drive while I restore it! 

 

[EdWills]

Hello Stevehello.  The library on usa7s has the Caterham publication of the Lotus Seven 2,3 and 4 for reference, (or just the Series 4  at 'barnblinker.com'.), and a Series 4 owner by the name of Andrew Barron published what I would call a thesis on the Series 4.  It was originally under the 'Connexions' web site, for free download, but 'Connexions' closed down..  I did find a trace of it at 'sevener.fr'  (google: 'Lotus Seven Series 4 design analysis'.).   I originally printed off some pages that I was interested in, and these are numbered 131 to 134, and Chapter 5, so Mr. Barron really went into detail about the Series 4.  If you can find the article, it makes great reading.

 

A noted authority on the Lotus Seven Series 4 is Hajo Steffen in Germany.  He has a wealth of information regarding the Series 4, and was in contact with Alan Barrett of Lotus who provided him with photos and background about the car.  Hajo is on Facebook Germany.  

 

Good luck with your project.

 

Cheers W.

 

P.S. $229.95 U.S. for a book? Phew, wonder why it hasn't been republished?

[EdWills]

Hello again Steven.  I note that you already have the usa7s download - should have reread your post again- apologies.  W

[stevehello]

On 7/5/2026 at 1:16 PM, San Augustine said:

The Tony Weale book on the Lotus Seven has a chapter on the S4 with a lot information on the wiring and other mechanical components. It is out of print but copies can be found on Amazon and EBay.

 

https://www.ebay.com/itm/233981728724

 

Here is an article written by him on S4 restoration.

 

https://lowflying.lotus7.club/2006/2006_04_07_7story25.pdf

 

SJ sports cars has a very good selection of S4 parts.

 

https://www.sjsportscars.com

 

If you have a Twin Cam Holbay engine  (which was the top of line S4 offering in 1971) or even if it is a Holbay crossflow  I would check with Ken Gray at Dave Bean Engineering. He would be a good source for info and parts. 
 

https://www.davebean.com

 

More info 

www.lotus7register.co.uk/lss17.htm

 

Love to see some pics of your car. My S4 is a long way from being on the road. So much that I bought a Caterham to drive while I restore it! 

 

 

[stevehello]

Thanks for your effort in posting information relating to my car. I'm not sure how to reply to people here, but I was interested to hear that you also have a series 4 car. What year was it built? Could you tell me if it also has a blue and a black battery cable? Does the blue cable connect to the chassis like mine? Which cable goes to the Positive terminal of the battery?

[JohnCh]

41 minutes ago, stevehello said:

I'm not sure how to reply to people here

 

@stevehello, please see the help guides, which cover how to use various aspects of the forum, including how to reply:  https://usa7s.net/ips/articles.html/forum-help-guides/

 

If you have any questions or run into any issues, send me a PM and I'll try to assist (and yes, the help guides also cover how to send PMs  )

 

 

 

[San Augustine]

13 hours ago, stevehello said:

Thanks for your effort in posting information relating to my car. I'm not sure how to reply to people here, but I was interested to hear that you also have a series 4 car. What year was it built? Could you tell me if it also has a blue and a black battery cable? Does the blue cable connect to the chassis like mine? Which cable goes to the Positive terminal of the battery?

My car is a 1972 RHD crossflow. I had a similar problem but both my cables were black! I solved it by hooking up the battery and then using a multimeter to confirm the positive and negative wires on the turn signal lights. https://www.youtube.com/watch?v=ZZ-HIafxafA
 

Edited Tuesday at 02:28 PM by San Augustine

[IamScotticus]

sitting that long...

Clutch frozen to the FW, all brake cylinders rusted, freeze plugs eroded, Rings frozen, all rubber brake, clutch and coolant hose need replacing, carb pump diaphragms, steel fuel tank rust, dried crank seals, alternator water pump drive belt, tires, steering rack grease, A-frame center bush esp if its been soaking in oil.  Diff oil refresh.  Valve spring compressions because you've had a couple of them being squished for 40 years. front and rear hub bearing repacking.

Then we can talk electrics.

[pethier]

1 hour ago, IamScotticus said:

sitting that long...

Clutch frozen to the FW, all brake cylinders rusted, freeze plugs eroded, Rings frozen, all rubber brake, clutch and coolant hose need replacing, carb pump diaphragms, steel fuel tank rust, dried crank seals, alternator water pump drive belt, tires, steering rack grease, A-frame center bush esp if its been soaking in oil.  Diff oil refresh.  Valve spring compressions because you've had a couple of them being squished for 40 years. front and rear hub bearing repacking.

Then we can talk electrics.

If you have the Alfred and Alder trunnions a la Spitfire, and someone used grease instead of oil in them, the grease may have hardened.