1992 Cherokee 4.0 starting but not running

Hello all!

This is my first post to . I was referred to this website by my mechanic in South Lake Tahoe, CA. First off, i have a 1992 Jeep Cherokee 4.0. Its the first jeep I've ever owned. I bought it from a mechanic in Reno, NV. It had a rough country lift on it with new tires and 187k on the engine. I got it for 2000, which i thought was a steal. Everything worked fine when i first got it. Then i started running into problems. It started throwing codes for the MAP and TPS sensor, which i replaced both. I do my own basic work on it (oil changes, air filter, drain and refill coolant, etc) however living in a town that has recently received 10 feet of snow, its a little hard to work on a car with no garage. After driving it to and from work for a few months, it developed a nice crack in the intake manifold. I decided that job was too much for myself so i took it to my mechanic. They finished the work and did a great job (i think). However, after a few weeks, and one of the worst rain storms in recent Tahoe history, it decided to die on me while i was driving to the store. I just started losing power and it eventually died when i rolled into a gas station. Now it was raining very hard, but i was not romping on it, nor did i go threw any puddles or anything like that. I got it towed to my house where my friends and I tried to diagnose the problem. The jeep will fire up and run for a couple seconds then just die out. We checked for spark in one of the plugs which was good. We also checked the fuel in hose to the rail and it had good fuel coming out. I can hear the fuel pump turn on when i turn the key. We also checked that all the vacuum hoses were hooked up and not clogged. i disconnected the battery for a night and still the same problem. We took the air filter off (which is an aftermarket) and checked the throttle body which looked clean. I checked all the fuses and made sure everything was hooked up, couldn't find anything not connected. It isn't throwing any codes besides the battery disconnect. Oil was just recently changed and looks good. It smells like gas when i try to fire it up. It sounds normal when i start it, but just dies out within seconds. all my gauges look normal when i start it. I also replaced the neutral safety switch last month. I am in a pickle, since i am without my main mode of transportation to work, which sometimes requires a nice jeep like mine to even get to work. not to mention the fact i love driving in the snow, its like driving a mini tank. thank you in advance for any and all help/suggestions.

-Jordan

Sounds like the ballast resistor may be bad. The ballast resistor is bypassed when cranking, when the motor starts the fuel pump power goes though the resistor.

I agree. Make a jumper wire out of a short piece of wire and 2 spades and attach the wire together. If it runs after that, you know the ballast resistor is your problem. After that, you can leave the jumper there, or just clip the ends off and couple the two wires together.

The ballast resistor's only purpose was to reduce voltage to the fuel pump to cut down on that high-pitch buzzing noise. If the noise bothers you, you can find one at the parts house, but I myself have heard a lot of reports that those ballasts drop the voltage too low... could try one from a junk yard, but it's any man's guess as to whether or not those are going to be any good (and for how long, if they are good).

thank you for the responses! unfortunately tahoe is about to get hammered with 6-8feet of snow. i will hopefully be able to do these checks on tues/weds after the storm and i report back. thank you again.

-jordan

well i got a couple buddies to help me dig it out and try jumping the ballast. and it worked!!! thank you guys for the help!

on my 90 the connector to the ballast resistor looked connected but was apparently not. may just need cleaning or just jump the resistor.