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1994 Jeep Grand Cherokee Laredo Start Problem

Last winter I experienced start problems at 40 degrees and below. The problem increases as the temp. decrease. Here is what I see. I turn the key and all dash warning lights come on except the CHECK ENGINE light. While waiting, with the key in the on position, the CHECK ENGINE light begins to blink on and off in sync. with a fluttering relay under the hood. Once this action stops the CHECK ENGINE light goes off and a noise like a vacuum valve throwing is heard and the car starts.

I have been driving all spring and summer (start) trouble free: so this problem is all due to temperature drop. If the air temp goes below 30 degrees I may have to wait 15 to 20 minutes before the CHECK ENGINE light stops blinking so I can turn the key and start the car. It just won’t start otherwise.

Can someone please help me to address this problem before winter hits. I don’t want to have to go though another winter sitting and waiting for my CHECK ENGINE light to faintly appear on my dash, blinking in sync with a relay (which I did replace).

When was the last time you replaced the battery and cleaned the battery posts? This really sounds like a battery problem.

battery is brand new, i am start problem free right now because it is summer. Do you think the new battery will have solved my problem. I hope so, but not sure. When winter comes it could start happening all over again.

Could you possibly name that relay? If you can, there’s no need for us to re-invent the wheel.

hellokit: the relay I replaced is the STARTER RELAY.

hellokit, you got any Ideas

The starter relay will chatter when the voltage to it has fallen too low. Your battery can be good (12 3/4 volts); but, voltage can drop from the ignition switch before it gets to the starter relay. Disconnect the yellow wire from the starter relay. While someone holds the ignition key to START, hold a voltmeter to the end of the yellow wire. If the voltage isn’t 12 volts, trace the circuit all the way back (with the voltmeter) to the fuse, to check for where the voltage drops. Here’s the wiring diagram. Click on Fig. 33.

After looking at some wiring data on the vehicle I would guess the trouble is due to either the ignition switch or in the connector to it.

You say that you heard the buzzing of a relay when the trouble is occurring and that you replaced the starter relay. I have to wonder if you really found the relay that was buzzing while the ignition was ON. That relay should only energize when the key is turned to the START position. Regardless, the ignition switch or the connection to it seem to be your best bet here. Relays usually buzz when the voltage supply to the load drops as the load tied the the relay is swtiched on. The voltage drop is usually due to a faulty connection in the power supply lead to the relay. In this case, the ignition switch area appears to be the source of trouble.

hellowkit and couqar: thanks for all your help. The trouble with this whole problem is low air temperature, (40 degrees and below) is the only time I get this happening. So frustrating. Right now I can’t try chasing it cause everything is working fine. Starts up every time. First turn of the key. Check engine light comes on with all the rest and goes right off like it should and she starts right up. Something I noticed or actually tried while this was happening last winter was I held the power windows and door locks switches in the on position and it speed up the fluttering of the relay and my wait time for the Check Engine light to finally go off so I could try starting it. Another thing affecting it was certain positions of the crank, I could flip the key to position the crank into a spot that would brighten the Check Engine light and speed up my wait. Do you think there may be a sensor or something affecting the ground of this circuit. This whole thing is really strange.

Yes, I understand the trouble only happens in cold weather. The other things you stated last still point to the ignition switch or the wire connection to it as the problem source. Before replacing the switch I would check the connections to it for signs of trouble. If that is good then the switch is the next step. You could purchase a can of circuit coolant in a spray can and spray the electrical section of the switch to test the switch for a problem. It may show up the gremlin. I really think though that just replacing the switch section will solve the trouble.

Thanks guys, I’ll give it a shot. Here is hoping!

after all is said and done, I asked a Jeep expert and he called it. The car’s computer was the problem. He said it was common with jeeps and he was correct.