MPI  INTRODUCTION:

As any Jeeper who owns an older Jeep with the 258ci. engine running the stock Carter carburetor already knows, these engines usually run poorly. I know this from personal experience, I own a 1990 Jeep Wrangler which was the last year available with the 258ci. powerplant. My Jeep has approx. 90,000 miles on it currently and had never ran worse.

The problem started the day I got it. The continuos unsuspected stalling, occasional vapor locking, and just plain poor running. I researched several options such as the Howell TBI fuel injection conversion (est. price $1100.00). There's also the Turbo City's TBI (throttle body injection) conversion (again $1,100.00 - $1,400.00).

I also came across the Mopar MPI (multi port fuel injection) conversion. This is an actual Mopar designed product that is also California smog legal-unlike some other applications. I searched and searched for a descent price but everyone seemed to want anywhere from $1995.00 to $2295.00 for the kit, not including the vibration dampner (required). The dampner usually runs another $185.00 on top of the already expensive price.

I finally came across an unbelievable deal at Koller Dodge. They advertise in several off-road related magazines for a extremely low $1650.00 price on their complete Mopar kits. That's approx. $350.00 - $500.00 less than the others. I gave them a call and ordered one. For my application, I needed an automatic transmission version. (specify your preference when ordering)
Below I will be discussing my personal experiences I obtained while installing my MPI kit.

REMOVAL OF THE OLD INTAKE & CARBURETOR:

Before starting the removal process, I first removed the battery cables. I also pulled the plug on the radiator and began draining the coolant. From there I removed the air filter and assembly (including the million miles of vacuum hoses). You can set these items aside for resale or trash them. For me, I was so happy to get rid of them, I just trashed all the old parts.

Anyway, after removing the air cleaner I removed all the necessary vacuum and fuel lines connected to the intake manifold and Carter carburetor. Instructions specify what hoses not to cut or take off. I removed the throttle cable and added this item to the junk pile. The kit supplies you with the necessary throttle cable required to run the system properly.

The only other part you're going to have to remove before taking the intake and carb off is the power steering pump. The rear mounting bracket for the power steering pump comes factory attached to the 4.2L intake manifold. I was now ready to remove the intake manifold and carburetor together. I first opted to take the carburetor off first and then the intake manifold, but figured it would be easier to just pull it all out at once.

INSTALLATION PART 1:

This is important! The Mopar instructions clearly suggest not installing this kit on a older, tired engine. They don't specify why, but I'm sure it's because it might put to much strain on the lower end of a worn 4.2L engine. As shown in last month's article about the 4.0L head conversion, my engine appeared to be very clean and ready for the MPI kit. Below are some pictures from the previous article (4.0L head conversion) that shows the engine's condition.

(click on image for large view)

   

INSTALLATION PART 2:

After removing the old intake manifold, I was ready to start installing the new MPI kit. The MPI instructions suggest that you start by removing all the emission controls from the engine including the three solenoids located on the valve cover. After removing those items, I removed the pulse air valves and hardware. Again, these are all items you will no longer need. I then removed the mechanical fuel pump located on the passenger side of the 4.2L block behind the alternator. This pump was replaced with a cover and mount for the ignition coil supplied in the kit. See pictures below for detailed pictures.

(click on image for large view)