I have a 1987 4.0 that gets very little use. I have changed the o-rings 3 times each time once completed everything is sealed and no detectable leak. I drive it a short distance about every 2 weeks. After about 6 to 8 weeks a leak starts. I have had it leak at the head, fuel rail and not injector specific. The last time the Rukse was the brand, before that GP. I am mechanically capable. I have used motor oil and silicone grease to lube things up. Quality of the o-rings? Condition of the fuel rail? Injectors warn to the point that the seal breaks?
Thanks BR

Leaking air or fuel?
The original injectors were prone to leaking fuel from the body.

Fuel
I have ordered 746’s as mentioned on your site. Next step will be a new fuel rail if I can find one.

I have Renix fuel rails..

New, used… price?
Thanks

Used $75 plus shipping.

Going to give the replacement injectors a shot first.
Thanks

I would.

Installed rebuilt 746 injectors. These went in much easier then the original injectors. So far no leaks, but I have to give it some weeks before I will trust it.