Hard starting when hot

[Brian Bolick]

There is another potential culprit for this problem.

Our Jeeps seem to be infamous for the anti-drainback valve in the fuel system going bad. This makes for a long crank, or having to try a second or third time to get it to start.

Next time you go to start your Jeep, turn the key on, shut the key off, then turn the key on again. Do this a few times to let the fuel pump prime. It should start right up after cycling the key a few times! Did the same thing on my old XJ.

I’ve even tried that and a shot of starting fluid. It only happens when it’s hot, never a cold start. That’s why it’s so weird to me.

 

[Chris]

So priming the fuel pump doesn't work at all, even when you turn the key on and off multiple times (and when I say that, I don't mean cranking the engine, I mean turning the key to the on position so all the electronics turn on, but not so that you're cranking it).

 

[Brian Bolick]

So priming the fuel pump doesn't work at all, even when you turn the key on and off multiple times (and when I say that, I don't mean cranking the engine, I mean turning the key to the on position so all the electronics turn on, but not so that you're cranking it).

Correct, even cycling the fuel pump it wont resolve, i have gotten it to start off fluid but will only while getting the fluid and then die. keeping it alive so to speak for about 45 sec resolves it, but that also is not a one person job. But cool off time always resolves it. Its so weird.

 

[Chris]

Correct, even cycling the fuel pump it wont resolve, i have gotten it to start off fluid but will only while getting the fluid and then die. keeping it alive so to speak for about 45 sec resolves it, but that also is not a one person job. But cool off time always resolves it. Its so weird.

I'm stumped. Usually in this kind of scenario you'd at least have a check engine light throwing some sort of code.

It might be time (if you haven't already) to do a basic tune up. New spark plugs (gapped correctly), and make sure you get the right ones (see here: What are the best spark plugs for my Jeep Wrangler TJ 4.0?), fuel filter, (cap and rotor if yours is an older TJ that has a distributor), etc.

I suppose it could potentially be a failing fuel pump too.

 

[Gus]

2004 TJ 4.0 with same issue, no start or rough idle when engine hot. Did the tsb bulletin, and also use DEI isolation kit, but still not working. Any other suggestions? Please and thank you !

 

[dbbd1]

Have you replaced your spark plugs?

 

[Gus]

Yes, sparks plugs was done.

 

[ndaddy]

I would. It commonly affects these engines, and Jeep even has a TSB about it on the 4.0 engines I know.

You can get it with adhesive back like this:
https://www.amazon.com/dp/B00029KC2K/?tag=wranglerorg-20

Or without adhesive back like this:
https://www.amazon.com/dp/B00029KC2A/?tag=wranglerorg-20

I'd probably go for the latter of the two personally. Then you can cut it to fit the area you want it to.

The end result looks something like this:
View attachment 8580

old post, but probably still relevant. When I look into this wrap, it says 97-04 Jeeps. I have an 06, does that have a different heat response? I see I have an old, weakened blackened wrap on the engine, but I still have these symptoms and I want to redo it, but only if it makes sense!

 

[Chris]

old post, but probably still relevant. When I look into this wrap, it says 97-04 Jeeps. I have an 06, does that have a different heat response? I see I have an old, weakened blackened wrap on the engine, but I still have these symptoms and I want to redo it, but only if it makes sense!

I'm not sure what they changed as I've never owned a pre-2005 Jeep, but it would be worth a try.