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young-blood 03-23-2011 12:41 PM

Hard start, fuel line issue.
I'm new to this forum, but really hope the experienced members can help me out here.
I have to prime the 2004 LJ 3 times to charge the fuel line before start.
After some searching on this forum I have come up with a few causes for my hard to start LJ.
Cause 1. The fuel check valve (either in the regulator or pump itself, which one is the one responsible for maintaining fuel line pressure?) is letting fuel drain from the line. I have learned from this forum that I cannot simply install an inline check valve.
Cause 2. A leaky injector is draining fuel into the cylinder head, which is then being blown out the exhaust.

Here is why this thread may be unique regarding this problem:
My catalytic converter is throwing a 420 code and likely is burnt out. It does not rattle much, so perhaps the ceramic core wasn't shattered. Cause 2 (above) may be causing fuel to drain out the exhaust and fry the cat.
Has anyone had this problem?

I want to solve this issue before I buy a $700 cat and possibly burn it out too. (The damn thing is basically the whole header with three separate cat chambers. WHY JEEP?! The old ones were $200 and dirty simple to replace).

Now, I know there are ways to check if it is one or the other of those things. Cause 1: It'd be great if someone could walk me through the steps, rather than suggesting I buy a fuel pressure tester. It'd be really nice if someone had photos or at least a step by step on HOW to use the tester, or if I even need it (by saying I just need to replace a specific part instead).
Cause 2: Ho do I check for a leaky injector? I have NO IDEA.

Side NOTE: If I do have to replace the pump, is there a better one I can upgrade to?

Thanks for all your help in advance, this really has me worried as my inspection is out and I am in an emissions county.

rrich 03-23-2011 01:44 PM

I know you said not to, but these are lots cheaper than buying the wrong parts.


I bought one, works fine.

A leaky injector usually only drips when you shut it off. that's not going to be enough to hurt the cat.
it it was a major leak, you'd have driveability issues.
The pump - you can get them at the cheap stores that sell Chinese knock-offs. You'll have the opportunity to replace it in about a year or so. Get one from NAPA or the dealer - more expensive but last much longer.

The cats - the small ones near the engine are just screens (you can see right through them) - when you take the entire assembly apart you may find the screens are OK, just plugged. Remove the carbon with lacquer thinner and re-use. Soak it, brush what you can reach, blow it out with air. (Lacquer thinner will dissolve carbon slowly.)

The big Cat - call around to independent muffler shops - not chain stores. They have OEM direct replacement Cats at nice prices. Or call smog shops - they usually know where the deals on Cats are.

Chain stores like Midas, Advance etc are way overpriced.

young-blood 03-23-2011 04:03 PM

rrich, you are very knowledgeable, thank you. I'll get on checking the cat "screens" and will pick up the fuel tester. (I was trying to say earlier that I don't know how to use one yet mostly, so I was looking for advice on how).
Odd thing is, my O2 sensors seem to be before and after the "screens." Not after the actual cat under the skid plate. So that worries me a little bit about the possibility of cleaning them.
Will post how it goes.

young-blood 03-23-2011 04:04 PM

I still have the question of whether to replace the regulator, or the whole pump if the check valve is the problem. Have heard they both have one.

rrich 03-23-2011 05:13 PM

Replacing the entire module is best. If the regulator or check valve has failed, the pump's not far behind.
Plus you don't have to disassemble all those small parts and get it wrong, then get to do it again.

Price difference is not that much more.

Doing it right you soon forget the extra cost -
But doing it half way and having more trouble you forget forever how much you saved.

young-blood 03-25-2011 10:47 AM

Looks like it may be the pump. Still unsure what caused the cat to fry. Not looking forward to $700 bill on a part I don't even want.

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