Greetings, all,
I'm getting ready for some scheduled time with my xj, and I'm hoping to maximize the time

As my signature indicates, I have a 350 Olds-powered '74, and it's had an interesting conversion (I would have guessed SBC power, my preference - former Chevy tech), including the original positive ground. It has a GM alternator that won't excite/charge until 2500 rpm - too high, in my opinion. It has a GM block mounted fuel pump as well as twin electric fuel pumps in the trunk going into a tee. No fuel switch valve, just power to one pump or the other. Can't tell exactly how much of this was factory and how much was conversion, but one of the changes I was planning (to take advantage of modern electronics down the street) was to convert it to negative ground. Just trying to figure out how much needs to be touched, especially in light of the conversion, and hoped I could get some feedback from you all.

I wonder if the positive ground setup it currently has is playing part to the sluggish running I've experienced so far. I really wish it had a small block Chevy in it, but I've considered an LS with twins, so until I get that up and financed (and located), I'll make due with Olds power. Always loved the grunt of BOP!

Except for two rust spots on the wheel wells, this is a very clean car that hopefully the prior owners had sorted regular Jag issues. I can handle the GM issues I'm also planning to convert it to modern door locks with a remote, which will be made easier with a negative ground system.

The distributor plug I haven't checked to see if wires were reversed, nor many of the systems also likely needing polarity changes. With the fuel pumps issue, I may simply remove them from the circuit for testing/time being, and see if the factory mechanical pump can pull fuel to the engine by itself. That'll take care of the fuel leak problem it has now. I do want to see if converting it to negative ground will help the ignition system and give it some better performance.

Is there a checklist of things I should change before connecting positive to positive for real?

Thank you,
Joe

 

Something very strange is afoot. Jaguar began using alternators.....and *negative* ground..... in 1964-65. When your '74 was born it was negative ground.

Anyhow, I agree with your idea of taking the e-pumps out of the plumbing. The mechanical pump should do the job OK.

Cheers
DD

 

That's good news, thanks for the input!

 

Ok, yesterday I had one of those "I'm a moron" moments.

Doug - you're absolutely correct; it's a negative ground system. I can't fathom how I got that confused I guess that's why i no longer get paid to fix cars

I removed both pumps and replaced all the line and installed a universal fuel filter. Once I got the system primed, it worked fine with just the mechanical pump. I drove it for about five miles, and except for a little hesitation off-idle (hopefully cured with an accelerator pump adjust), it seems to work fine. I will, however, be replacing that alternator with something that excites a little sooner. The local parts store has a couple that will work. For future electronics installs, I'll replace this alternator with a 100amp model.

The next thing on my list is to get the central locking system working. Instead of troubleshooting the factory system, I'm going to remove it entirely and install an aftermarket system with wireless remote. If I can find one locally, I should be able to get it completed this weekend. Then there's a small list of things that need attention before this could be considered a 'driver', including getting all seat belts to function (the driver's seat belt latch is broken.

I'm excited to get this finished. I need the garage space to remove the transmission in my son's Cougar. Wait, maybe I should milk this for a bit longer...

 

Most GM alternators need the idiot light to be hooked up and working for proper field excitement. Perhaps someone didn't hook up the idiot lamp circuitry properly. The fact that you have to rev it to 2500 RPM suggests you are running is as a 1 wire alt and there is no ignition switch based field excitement.

this page offer a great explanation
Delco SI Alternator 1-Wire vs 3-Wire Explained