YJ doesn't want to start when engine's hot. Backfiring. - Jeep Wrangler Forum
Jeep Wrangler Forum

Go Back   Jeep Wrangler Forum > YJ Jeep Wrangler Forum > YJ Tech Forum

Join Wrangler Forum Today


Reply
 
Thread Tools

Please support our sponsors and let them know you heard about them on WranglerForum.com
Old 03-31-2012, 12:24 PM   #1
Jeeper
 
TwoPointFiveLiter's Avatar
 
Join Date: Feb 2012
Location: Central Massachusetts
Posts: 33
YJ doesn't want to start when engine's hot. Backfiring.

I had some issues with starting awhile ago, and thought I had it all fixed after replacing almost the entire ignition system, but I guess not.

What happens is, when the engine in cold, it will crank like 5 or 6 times and start. But once the engine is warmed up and I turn it off, if it is left sitting for more than like 5 minutes, it won't want to start again.

I'll need to floor the gas to get it to start, after a few backfires. Usually it will either catch the starter before it's started and grind, backfire, try to start but bog down before it's going, or actually start.

I'm a pizza delivery boy too, so it's super annoying!

I pretty much just replaced the MAT sensor, the ignition coil, the ignition module, the spark plugs, the cap and rotor, the ECM, the fuel filter, and a couple of other things that I can't think of right now.

Also, I dunno if it's worth mentioning, but when I go to get gas, when I take the filler cap off, despite it being alot higher than the tank, there will be gas below the cap and on the inside of the cap. Like yesterday, I got gas the night before, let it sit all night, drove it for a couple hours the next day and when I went to go get gas, there was visibly wet mark below my gas cap. That means it's climbing up and leaking out somehow. It's just a little, but I'm still wondering if that's maybe my problem?

[EDIT:] It idles perfectly fine. and runs perfectly fine. It's just the starting that's an issue.

TwoPointFiveLiter is offline   Quote Quick Reply
Old 03-31-2012, 01:10 PM   #2
Jeeper
 
Master4th's Avatar
 
Join Date: Mar 2012
Posts: 341
What year and engine does your Wrangler have?

Master4th is offline   Quote Quick Reply
Old 03-31-2012, 02:57 PM   #3
kik
Jeeper
 
kik's Avatar
 
Join Date: Dec 2008
Posts: 4,079
Images: 1
Quote:
Originally Posted by Master4th View Post
What year and engine does your Wrangler have?
This. Plus, in general, when there are problems of this nature with fuel injection systems most times it's a weak fuel pump/pressure regulator. That's why you have to floor it when it's hot. The one thing you or a tech can do when it's hot is to check the pressure to make sure you're getting the proper amount of fuel being pushed through. If it's weak, again, could be the regulator or the fuel pump itself.
kik is offline   Quote Quick Reply
Old 03-31-2012, 03:23 PM   #4
Jeeper
 
Tyewilly's Avatar
 
Join Date: Dec 2010
Posts: 551
Sounds like the fuel pressure regulator is bleeding off fuel into the vacuum line, or an injector is leaking. Pull the vacuum line off the regulator and check for gas.

Edit: since it's an '89, nevermind about the regulator. I'd look into a leaky injector. If it's leaking, it'll bleed off your fuel pressure causing long cold starts because the pump has to build the pressure back up. It will also cause flooding on hot starts because of the gas puddled up in the intake manifold. Flooring it while starting clears out the flooding.
Tyewilly is offline   Quote Quick Reply
Old 03-31-2012, 03:31 PM   #5
Jeeper
 
DILLIGAF's Avatar
 
Join Date: Sep 2011
Location: Cortland NY
Posts: 595
He should have included the year in his user name..lol
DILLIGAF is offline   Quote Quick Reply
Old 03-31-2012, 04:20 PM   #6
Jeeper
 
89JEEPYJ's Avatar
 
Join Date: Oct 2010
Posts: 967
From my experience when that happened i had a clogged CAT converter and it was restricting it too much
89JEEPYJ is offline   Quote Quick Reply
Old 03-31-2012, 09:48 PM   #7
Jeeper
 
TwoPointFiveLiter's Avatar
 
Join Date: Feb 2012
Location: Central Massachusetts
Posts: 33
Quote:
Originally Posted by 89JEEPYJ View Post
From my experience when that happened i had a clogged CAT converter and it was restricting it too much
Haha, sorry guys, what a newbie mistake.

'89 YJ, 2.5 TBI.

The CAT had a ton of acorns in it that I found while redoing the exhaust system, but it seemed fine...

Quote:
Originally Posted by Tyewilly View Post
Sounds like the fuel pressure regulator is bleeding off fuel into the vacuum line, or an injector is leaking. Pull the vacuum line off the regulator and check for gas.

Edit: since it's an '89, nevermind about the regulator. I'd look into a leaky injector. If it's leaking, it'll bleed off your fuel pressure causing long cold starts because the pump has to build the pressure back up. It will also cause flooding on hot starts because of the gas puddled up in the intake manifold. Flooring it while starting clears out the flooding.
This sounds like it.

It takes alot more cranks to start cold than when it's warm and hasn't been sitting too long.

Also, I didn't mention it, probably dumb of me, but I forgot. Sometimes what will happen is, when I am cranking it, and it should start or stumble or whatever, sometimes nothing will happen except a loud "TSSS" noise, like a high pressure amount of air escaping somewhere. Then it will just crank for days unless I give it some gas. Or leave it for a little while I guess.

Sometimes it will do that, so I'll try again and give it gas and it will backfire or stumble or a mix of all before it will start. It's a real mess.

TwoPointFiveLiter is offline   Quote Quick Reply
Reply

Tags
'89 , backfire , problem , start , starting

Quick Reply
Message:
Options

Register Now

In order to be able to post messages on the Jeep Wrangler Forum forums, you must first register.
Please enter your desired user name, your email address and other required details in the form below.
User Name:
If you do not want to register, fill this field only and the name will be used as user name for your post.
Password
Please enter a password for your user account. Note that passwords are case-sensitive.
Password:
Confirm Password:
Email Address
Please enter a valid email address for yourself.
Email Address:

Log-in

Human Verification

In order to verify that you are a human and not a spam bot, please enter the answer into the following box below based on the instructions contained in the graphic.



Thread Tools

Posting Rules
You may post new threads
You may post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
How many of you just love to clean your Wrangler everyday? redirysae JK General Discussion Forum 55 04-24-2012 10:00 PM
new to this forum. hi tatemonkey1 WF New Member Check In 11 04-02-2012 10:23 AM
So I made it to Co. from Hi. Need a (class A) driving job now. Muddy Bob Colorado Jeep Forum 2 03-31-2012 07:20 PM
Follow up to JK 5th wheel removal and easy filler kit. wmwhitey JK General Discussion Forum 10 03-31-2012 12:49 PM
MN: MINT YJ half doors & upper softs! Rony Classifieds Archive 0 03-31-2012 10:16 AM



» Network Links
»Jeep Parts
» Featured Product

All times are GMT -5. The time now is 07:39 AM.



Jeep®, Wrangler, Liberty, Wagoneer, Cherokee, and Grand Cherokee are copyrighted and trademarked to Chrysler Motors LLC.
Wranglerforum.com is not in any way associated with the Chrysler Motors LLC