Electromotive JFI^® (fuel injection) Kit

The following describes my first hand experience with the Electromotive JFI fuel injection kit in 1996. The kit was purchased for a '90 Jeep YJ equipped with an AMC 258 I6 engine. My hopes (also) were to cure all the off-road problems that occur with carburetors: flooding, rough idle, hard starting on hills, stalling, etc.. The following describes the kit, installation, adjustments, and issues for the Electromotive product.

• The Kit
• Installation
• Initial Starting and Adjustments
• Fuel System
• Electrical System
• Problems
• My Jeep Today
• Back to Fuel Injection Kit Review
• DirtFirst! Technical Page

Purchasing the kit is the easy part. All you need is a local dealer or you can order direct. I ordered direct. The kit is very complete, "I was impressed". Just about every thing you need to install the product is included with the exception of fuel line and some small parts.

• Throttle body
• Computer Module
• Fuel Pump
• Wiring harness
• Direct fire ignition system (no points)
• Temperature sensor
• O2 sensor
• installation instructions
• CARB EO and emission decal for under the hood

At the time I purchased the kit, it was about $1800 plus tax.

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• The installation was relatively simple, but requires a lot of pre-installation preparation and installation time. I read the installation manual at least five times before opening the hood on the Jeep. Doing so made the installation easy and it worked correctly on the first try.
  
• Also, you must use high pressure fuel injection rubber hose, at more than a $1 a foot, this could be a hidden cost you did not plan for. You have to remove your gas tank to replace all existing rubber fuel lines with the good stuff.
  
• The second most difficult part of the installation was finding an appropriate location for the fuel pump. The installation instructions require the pump to be located at or below the bottom of the fuel tank. On a four wheel drive like mine, this would be a mistake because it would be damaged or ripped off by the first rock, stick or large clump of mud it came in contact with. So, I located mine in front of the fuel tank on the inside the driver side frame rail. This means that the pump will have to be primed all the time, which is hard on the pump.
  
• The next step was to remove the carburetor and almost every pollution control device under the hood. The kit greatly simplifies the engine wiring and plumbing. It is 50 state smog legal, too. Next, I bumped the engine over so number one was at top dead center and pulled the distributor. I installed the new trigger system in its place. I bolted the throttle body in place and completed the plumbing. The computer mounts to the valve cover (a design I don't care for due to heat and vibration). The computer has three direct fire coils built into the mount. This thing really stings the spark plugs. I finished the wiring in the engine bay. I removed the old wiring and was left with a clean looking engine compartment. The next step is to install the mass air flow sensor and air filter to the fenderwell. Now install a check engine light inside the jeep (you have to buy one). I used a Linwood Jumbo 12VDC diode and made a legend plate.
  
• I completed the rest of the installation according to the manual. It took about twelve hours to complete the installation.
  
• The next step is to replace the oxygen sensor with the heated style from the kit. Older jeeps without an O2 sensor will have to add weld a bung in the exhaust system for the new sensor.
  
• Next you need to replace the coolant temperature sender with one in the kit.
  

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• For the initial starting of the engine with the newly installed JFI kit, I verified the throttle position sensor (TPS) for the correct volt reading with the key set to run. When you turn the key to the run position you should hear the electric fuel pump run for about three seconds, then shut off. This is also typical for factory fuel injection. Since the fuel line is not primed, I suggest that you turn the key to off and then to run again (several times) to make sure the line has good fuel pressure (about 40 PSI). A fuel pressure gauge is necessary to test the fuel pressure. With pressure in the fuel lines, I checked for fuel leaks before attempting to start the engine, every thing was fine. After a short prayer, I turned the key to start with my foot off the gas peddle, and the engine fired easily. I was very excited!
  
• The timing was adjusted and away I drove.  It ran well but seemed hot. I didn't know that a coolant sensor was bad already. I ran the jeep a couple days but did not like how hot the exhaust manifold seemed to be getting. I called electromotive and they said the computer would learn the motor and that the 4.2 motors were "dirty" and I should drive it awhile. I did, one month later on the freeway - the engine backfired and began to stumble. I had cooked the valves in number 1 and 6 cylinders. Read on for more details. Please understand that these are my personal experiences with this product. In addition, I personally know three people with the kit that have suffered similar problems. Two of them returned to carburetion and the third is still struggling to make it work. He says "when it works it's great, but…."

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• For a bolt on product, it is fine, but there are some overall shortcomings in the fuel system that you should be aware of. The first thing is that my fuel tank was not setup for fuel injection. With a carburetor, it does not matter if the fuel pickup sucks some air from time to time because the carburetor gets its fuel from its own built-in fuel bowl. This is not the case with fuel injection. If the fuel pickup in the tank sucks some air, your engine will stall. A fuel injection tank has a sump in the bottom, which provides fuel for the fuel pickup at all times, even when you are low on gas. Without the sump, the fuel pick will suck air when you are low on gas, especially when going around corners and all the time when off-road. I was running out of gas with 5 gallons still in the tank. I also experienced vapor lock on hot days
  
• The next fuel issue is the location of the fuel pump. The best location for the fuel pump is in the fuel tank. This is where it is located on nearly all fuel injected cars and trucks. The fuel keeps it cool, it is located right at the fuel source eliminating the line priming problem, and it is away from the elements that could damage it. The disadvantage is that the fuel tank must be removed to service the fuel pump. I switched to a 1991 fuel tank and in-tank pump for the 4.0 liter engine and my fuel pump problems were solved.

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• Your electrical system must be in excellent condition to support fuel injection. If you have a shaky alternator, a battery that always needs to be recharged, and a lot of old wiring that has been spliced and crimped 10 times to many, you will not be happy with your new fuel injection kit. While you are installing this kit it is the perfect time to clean up the old wiring and upgrade your charging system.
  I have dual Optima batteries in the Jeep and a Wrangler Power Products 160 amp alternator and felt my power capacity was more than adequate.
  

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• One problem involved the trigger assembly which failed twice and left me stranded. I had the vehicle trailered home once and flatbedded home the second time. The sensor used to detect crank position failed both times. Both times they were replaced under warranty.
  
• Wiring harness woes. I had wires break inside their wiring loom on one occasion, at the mass air flow sensor once and at the computer twice. All three times killed the vehicle immediately. Carry your schematics and a meter. I was able to repair the wires each time. I don't know why they failed and neither did Electromotive.
  
• The computer module failed three times. The jeep began to run rough and stumble at first and then finally stopped altogether. The ECU was replaced and the problem was solved temporarily. The next failure began as an intermittent shutdown. The jeep would just quit. Wait 10 minutes or one hour or the next day and it would run normally. Finally it failed altogether and I had it trailered home and replaced the computer again. Problem solved temporarily. The third time it would stumble and cut out but keep running. It happened infrequently but seemed to happen most on the freeway. Replaced the computer again. Problem solved.
  
• Another problem involves the availability of parts. Each time the system failed I had to get parts from Electromotive or one of their reps. It meant a wait.
  
• The final problem involves the sensors and the computer firmware. I had the temperature sensor fail twice. The first time was about a month into the retrofit. The computer leaned out the motor thinking it was cold. Guess what happens when... lean fuel supply, warm motor, freeway speed, long uphill pull. Yep, you guessed it, cylinders 1 and 6 fried. I had to rebuild my motor twice.
  

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• Well, it has been over two and 1/2 years since I purchased the JFI system which is no longer installed in my jeep. After the second engine rebuild I just didn't trust it. So I sold the motor and the fuel injection along with the old carb setup.
  
• Don't get the wrong impression! After experiencing the JFI kit on its good days, I still had a huge desire for a fuel injected Jeep. So, I installed a "factory stock" fuel injected Chevy engine and have been very happy ever since. It is smog legal, too! (more on this in a future article)
  
• I consider this a very expensive ($5000+) and frustrating lesson and have learned that the only way to go is to use FACTORY, FACTORY, FACTORY products that run on thousands of cars and trucks.  Parts that can be purchased and replaced nearly anywhere.  Parts that have been proven by the test of time and designed by competent engineering.
  
• At this time the only retrofit fuel injection kit I would even consider for the 258 is the "Jeep OEM" kit and it is expensive. However, it uses the electronics and fuel system from the 1995 4.0 liter motors (-factory parts-).
  
• Update '99 - the 5.7 liter LT1 is still running flawlessly.  It was the best thing we ever did! (looking back on it)  The fuel economy and performance are well beyond expectation.  We have had no problems at all since startup over two years ago.

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