Coolant Temperature Below 210

Thanks all for the info! I’m about to head out camping for the weekend. Jeep will stay parked in the garage. I’ll start by testing the fuel pressure Early next week and follow back up.

Like Jerry and Pagey said, it’s likely both the regulator and fuel pump hushing by the symptoms I’m having


*edit* just did another test where it has been sitting for about an hour, turn the key on once, let the pump prime and then turned it over (didn’t turn the key off or on, just on and then crank). Took maybe 2 seconds to fire up. Then I shut it off, let it sit as if I was getting gas for a couple of minutes, then turned the key to on and then cranked it and it fired right up. So it may not be the regulator after all... but still don’t understand why it wouldn’t start after I did a 15 mile drive earlier today..?

Brianj5600 said:

How hot is it where you live? Is the no start condition only when the engine is hot?

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Upper 80s, lower 90s today. Today was the first time the Jeep wouldn’t start right up after running. But I’ve also only owned it for a week and only drive it every couple of days

To follow back up... this is a video of me cycling the key on and off a few times with a pressure tester hooked up. This was test #2. The first test, the pressure went up to about 10 PSI on the first key turn.

With the key in the on position, it will slowly lose pressure(as seen in my video, you may need to download it to view it). If I turn the key to the off position, it will still lose pressure but at a slightly slower rate then compared to the key in the on position.

Today I’ve been trying cold and warm starts all day without cycling the key on-off and the Jeep has been starting with little to no issue.

But after the same 15 mile drive I did last week, the Jeep does not want to start after I turn it off and then try to start it a few minutes later. After some reading I think it is vapor lock so I ordered some spark plug wire insulator boots and am going to try this trick (putting them over the injectors) to hopefully prevent vaporizing my fuel from heat soak. Unless you guys have a solution that is easier/better?

Hello All,

So while I don’t think the fuel pump is is top condition because pressure will slowly leak off, I don’t think it’s the main issue right now because it’s been starting lately when cold no problem. Also starts when warm no problem.

But after an extended drive (heat soak), and shutting off the Jeep and then starting it again, I think vapor lock is happening. So I bought the DEI fuel rail and injector insulator kit for $60 and installed it and tested it yesterday.

well after a 20 mile mixed driving loop, as I was backing into my driveway the Jeep actually died. Then I tried to start it with the same issue as before installing the insulation. It will crank like normal but not fire. I’ve tried cycling the key as many as 8 times before trying to start after a heat soak but no luck. I have to let it cool for 20-30min before it will start back up

I’m at a loss, any ideas what’s going on when it’s hot?

Just did another test drive. 6 miles at 60mph, coolant heated up to low 200s on the coolant temp, drove on a dirt road at 5-10mph for a mile or so and temp went down to 194. Then back 6 miles at 60mph and coolant went up to 205 degrees. This was with ambient air at 75 degrees. Then I parked it, let it heat soak for 3 min and then cycled the key on and as soon as the fuel pump shut off I cranked it over and it took a few cranks but it did fire up.

this is different then when I do this test in 95 degree ambient air. The Jeep has to cool 20-30 min after this run to get it to start again. This is after I installed the DEIfuel injector and rail insulation.

still not sure what my options are to reduce vapor lock during the hot days?

pagrey said:

Even though you think the bleed down isn't a big deal because it still starts easily sometimes it is the problem. The lack of pressure allows the fuel to boil. Until you prevent the bleed down you will have vapor lock. When the fuel pressure stays high that will prevent vapor lock by raising the boiling point of the fuel.

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I didn’t think about that... thanks! I’ll rent a tester again and test the fuel input line to see if I can determine if it’s the fuel pump check valve or a leaky injector
Only reason I say testing again is because the PO supposeably replaced the fuel pump 500 miles ago, likely with some cheap auto parts store brand