Dad's 1991 4.0L is hard to start cold. - Jeep Wrangler Forum
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Old 08-01-2009, 03:21 PM   #1
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Dad's 1991 4.0L is hard to start cold.

Hey Gang,


Dad has a 1991 yj with a 4.0L and an auto tranny. Hard to start in the morning after sitting overnight. The engine just cranks and cranks for several seconds before firing. once it fires, it runs great. AND will start for rest of the day. Hot starts and even Hot soak starts are no problem. Only "overnight" cold. Truck has had full tune up(ignition bits, filters, pcv, etc) and even has had the temp sensor near the thermostat replaced as well. No change. If anything, the cranking when cold is getting longer. Any ideas????


Here's the real funny part. During the winter, the jeep started instantly everytime. It didn't matter if it was 30, 10 or even -5 degrees. Nso problem. It's only been mid spring to present.


thanks for your time
Jake

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Old 08-01-2009, 04:15 PM   #2
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turn the key on for a couple of seconds before trying to start. let some fuel get up there. donno, just a thought.

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Old 08-02-2009, 08:51 AM   #3
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if you turn the key on for a couple seconds and repeat that a couple times, it primes the fuel. if it starts at that time its the fuel check valve that is supposed to hold pressure in the line when not running.
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Old 08-02-2009, 09:28 AM   #4
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I was having the same problem with mine. I thought it was the check valve in the fuel pump but it was actually a rubber o-ring/grommet where the fuel pump goes to the metal fuel line. Mine starts perfect now every time now. Put a fuel pressure guage on the fuel rail and see if the pressure drops when you turn the motor off.
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