bassmaster86

I am stumped at this issue, if the jeep has been sitting for a while (like during my shift at work or overnight in the driveway) it'll start right up, if I've been driving and for example shut it off and go in the store for a few minutes it'll start right back up. But if it sits for an hour or so it'll crank longer than normal, like 5-8 seconds or so but will always start.

I've replaced the fuel pump, TPS, spark plugs, starter, battery, and i upgraded to 4-hole injectors. It always has good fuel pressure when it's acting up and priming the pump over a few times before starting doesn't make any difference

Does anyone have any tips on what else I could check

97grand4.0

crank position sensor?

bassmaster86

I always figured the crank sensor just goes bad, not just act up. I could be wrong though I've just never had one "act up" before, they've just always gone bad all at once

Rockhead

It could be heat soak; mine gets this regularly. After a hard start, does it run rough? I really don't know what to do to beat "heat soak". I've insulated all of the fuel lines that are under the hood, and the injectors.

jordan96xj

I don't have a direct answer. But if you can reproduce the problem under specific conditions like you described, I have another test for you to do.

Next time you think the conditions are right to produce a "hard start" do the following.

1. Press the accelerator pedal to the floor
2. Turn the key and crank the engine over 3-5 times (it should not start)
3. Release the key, and take your foot OFF the accelerator
4. Attempt a normal start

Pressing the pedal all the way down will put the computer into clear-flood mode during start, which will basically shut off the fuel injector commands while cranking. If you find you typically get clean normal starts after doing this test, it can point to fuel injectors that are leaking when they are hot, and leaving you with a bit of a flood to clear the next time you start.

Do it a few times over the next few occasions and report back.

If that test produces no difference in behavior then....

Get an inductive spark tester. They sell them at auto parts stores, and they are about the size of a pen. They can test for spark by simply placing them next to the coil wire or a spark plug wire. These are VERY handy to have in your go bag.

Then, when able, have someone else start the vehicle under the likely "hard start" conditions and place the spark tester on the coil wire or a spark plug wire while you attempt a "hard start". This will help determine if the spark comes in early, but the start takes several additional seconds. Or whether the spark is absent until the start up happens. This can really help narrow things down.

Good luck.

bassmaster86

Thanks a lot man, I'll give those test a try tomorrow, I can pretty much pin point when it's going to act up, I'll report back after I give those test a try

limproved

If it IS heat soak, some jeeps inexplicably have a nice factory insulator under the intake, where most do not. It seems like a good idea since the exhaust is right under the intake runners; you might find one in the junkyard. I'm still looking for one. There are pics of this in one of build threads here but I can't recall which one, if anyone else can help out...