4.0L vapor lock fix with a heat shield on the fuel rail

[K2]

After putting in my stoker with the 99+ intake manifold I was getting a misfire when it got hot. Mostly if I tried to use the a/c, but even without it I was having trouble. A friend of mine who is a Jeep tech came by with the DRB and found nothing wrong. After inspecting my Jeep he noticed it was missing the "debris shield" on the intake manifold. Apparently in warmer climates the 4.0s were getting vapor lock with the new intake and there was a tsb for it. He said some were fixed by simply as putting a wooden clothes pin on the #3 injector. That acted as enough of a heat sink to stop that problem. Here is my one step further:

I bought this for $15 at AdvanceAuto. It is .75" diameter 3' long fiberglass heat shield tube.



I then cut small pieces to fit over each injector.



I removed the fuel rail and installed my pieces.



After I reinstalled the fuel rail. The remaining piece was almost exactly the same length as the fuels rail. I cut it length wise, cut holes for the injectors and wrapped it around the fuel rail. I finished it off by zip tying it on.

[AgitatedPancake]

This is awesome, I've thought about doing this to the WJ. I've heard the same stories on the 4.7 and the fuel in the rails getting superheated and vaporizing/vapor locking. I've always noticed it takes a couple extra cranks when my jeep is completely heat soaked and I think this is the problem. I think I'll be doing this very soon!

[K2]

I will also mention this happened mostly highway/around town driving, when I would hit only 210deg. It didn't happen often on the trail. When wheeling, if I didn't pop the hood when I stopped it would vapor lock as well. But crawling it did fine.

[TN_WJ]

Over the past 6-8 months my '99 wj 4.0 had developed these exact same symptoms. I tried this heat wrap fix about 2 weeks ago and my misfire/vapor lock issues have since vanished (knock on wood). I still had my factory heat shield on the manifold but when I moved it around a little to install the heat wrap it was basically crumbling apart so I'm guessing it was less than effective. Thanks for posting this!

[1ABrian]

huh this is pretty interesting. Never thought of this on my ride. I'm pushin 240K on my 97. I should take a look. Just for gigles, what if I wrapped the plastic with tin foil? besides looking stupid, do think that would work also?

[K2]

TN you're welcome.

Brian, I dunno. I am guessing it will as long as you can keep a bit of a gap, depends on how bad your vapor lock is and how hot the engine gets.

I should take a pic, I added another one, the whole 3' length, on the fuel line down toward the tank. This should block header heat before it gets to the fuel rail.