25/30RH- long crank time when the motor is warm. - JeepForum.com
 1Likes
  • 1 Post By noise_maker
 
LinkBack Thread Tools
post #1 of 5 Old 03-11-2021, 02:27 PM Thread Starter
noise_maker
Registered User
 
noise_maker's Avatar
2000 TJ Wrangler 
 
Join Date: Nov 2007
Location: Jackson, MI
Posts: 588
2.5/30RH- long crank time when the motor is warm.

In my wife's 97 2.5 30RH it will fire right up first time every time if the engine is cold, regardless of how cold out it is.

If the engine is remotely warm it will long crank before it starts. It has done this since we got it 2+ years ago. It dosnt matter if you let it sit 5 mins or a hour if the motor is till warm it long cranks.

All of the normal reasons for long crank check out fine so im looking for what else to check.


Fuel pressure does NOT bleed off quickly when measured at the rail. It will still have ~45PSI on it before turning the key back on after it sits for 60 mins.

Once you turn on the key it goes right to 49 PSI and stays there

if you bleed fuel off at the rail after its been sitting it doesn't spirt like there are bubbles in the line.

Just to be sure - I did pull the fuel rail while the motor was warm leaving the injectors on the rail then jumped the fuel pump relay - the injectors do not leak.

I heat wrapped the fuel rail thinking it might be heat related but that did not make a difference.

New Plugs/Wires/Cap/Rotor did not change the behavior.

When i pulled a plug while it warm and test cranked it, it does has spark right away. Also the TAC moves as it should while cranking - so the crank sensor seems to be fine.

For ****s and giggles i cleaned the all the grounds which didnt change anything.

No current CEL or pending codes.

Once its running it's completly fine. It always starts, but sometimes you have to crank it like its 0 degrees out and its a 70s ear 350.

What else would you check?

noise_maker is offline  
Sponsored Links
Advertisement
 
post #2 of 5 Old 03-11-2021, 03:19 PM
mukluk
Web Wheeler
 
mukluk's Avatar
2000 TJ Wrangler 
 
Join Date: Oct 2010
Location: Clyde
Posts: 6,668
Will it start quicker if you hold the throttle open a bit while cranking?

2000 TJ SE
2005 LJ Rubicon
mukluk is offline  
post #3 of 5 Old 03-11-2021, 03:25 PM Thread Starter
noise_maker
Registered User
 
noise_maker's Avatar
2000 TJ Wrangler 
 
Join Date: Nov 2007
Location: Jackson, MI
Posts: 588
Quote:
Originally Posted by mukluk View Post
Will it start quicker if you hold the throttle open a bit while cranking?
Ill try that and try to pay attention. I do know a few times it did seem like it just wouldnt start and i gave it gas and it went.

Just not sure if me giving it some throttle actually did anything or was just my imagination

Are you thinking the IAC or TPS/MAP sensors? - it idles fine so i never figured those were really in play.
noise_maker is offline  
 
post #4 of 5 Old 03-11-2021, 03:38 PM
mukluk
Web Wheeler
 
mukluk's Avatar
2000 TJ Wrangler 
 
Join Date: Oct 2010
Location: Clyde
Posts: 6,668
That's precisely what I'm thinking: either something amiss with the IAC, the stored IAC pintle step count in the PCM, or the signal from the TPS or MAP. Often times the PCM will lose the IAC step count if supplied voltage to the PCM is low; this could be caused by increased resistance in the wiring/connections between the PDC and PCM from the heat of operating the Jeep.

2000 TJ SE
2005 LJ Rubicon
mukluk is offline  
post #5 of 5 Old 05-19-2021, 09:19 PM Thread Starter
noise_maker
Registered User
 
noise_maker's Avatar
2000 TJ Wrangler 
 
Join Date: Nov 2007
Location: Jackson, MI
Posts: 588
Quote:
Originally Posted by mukluk View Post
That's precisely what I'm thinking: either something amiss with the IAC, the stored IAC pintle step count in the PCM, or the signal from the TPS or MAP. Often times the PCM will lose the IAC step count if supplied voltage to the PCM is low; this could be caused by increased resistance in the wiring/connections between the PDC and PCM from the heat of operating the Jeep.

Haven't been out here in awhile and wanted to update this for anyone else who searches for something like this

It was totally the iac even though it idled fine once started.

Replaced it and the problem has been gone ever since

thanks !
mukluk likes this.
noise_maker is offline  
Reply

Quick Reply
Message:
Options

Register Now



In order to be able to post messages on the JeepForum.com forums, you must first register.
Please enter your desired user name, your email address and other required details in the form below.

User Name:
Password
Please enter a password for your user account. Note that passwords are case-sensitive.

Password:


Confirm Password:
Email Address
Please enter a valid e-mail address for yourself.



Email Address:
OR

Log-in











Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)
 
Thread Tools
Show Printable Version Show Printable Version
Email this Page Email this Page



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 On
Refbacks are On

 
For the best viewing experience please update your browser to Google Chrome