MPI problems again??? - Off-Road Forums & Discussion Groups
Jeep-Short Wheelbase All discussion of short wheelbase Jeeps: CJ, TJ, YJ and JK

 
LinkBack Thread Tools Display Modes
post #1 of (permalink) Old 03-06-2001, 01:39 PM
Robert87yj
Guest
 
Posts: n/a
MPI problems again???

Having problems/doubts with my MPI. Wrote an email to Hesco. Please tell me what you guys think. Am I off base here or do I actually have a problem?

--------------
I just put on a new fuel pump and hesco 4.0 head on my 4.2 block on my 87 wrangler. I have run the MPI system for about a year with a different 4.0 head that I just couldn't get to stop leaking antifreeze. I started it up last night after about one and a half weeks with the battery disconnected and it had normal rmps, about 650-700 or so, like it did before I disconnected the battery. Is the computer supposto reset its self if the battery wire is disconnected? I remember reading somewhere that if the computer needed to re-learn the rmps would be high until I put a few miles on the engine like it did when I first put the MPI system on.

Is there something wrong with the computer if the rmps won't increase if the battery is disconnected for an extended period of time?
Thanks,
Robert Smith
----------------

Thanks in advance...I'm getting frustrated with this MPI system. It runs great, but the computer is the second one I've had on there. The first one was defective, hesco sent a new one, now I'm wondering if this one is defective also because it won't reset.


Robert87yj[img]/wwwthreads_images/icons/tongue.gif[/img]
4.2 w/<font color=blue>(4.0 head & MPI)</font color=blue> (jeep is down need a new head)
Process of a moonguy after beer
[img]/wwwthreads_images/icons/mad.gif[/img] [img]/wwwthreads_images/icons/frown.gif[/img] [img]/wwwthreads_images/icons/crazy.gif[/img] [img]/wwwthreads_images/icons/wink.gif[/img] [img]/wwwthreads_images/icons/smile.gif[/img] [img]/wwwthreads_images/icons/blush.gif[/img]
Sponsored Links
Advertisement
 
post #2 of (permalink) Old 03-06-2001, 02:15 PM
Old Hand
 
Join Date: Sep 1999
Location: San Diego, CA
Posts: 900
Thanks: 0
Thanked 0 Times in 0 Posts
 
Re: MPI problems again???

Robert,

Here are a couple of things to think about:

* There are two power wires. One is switched and the other constant. Are you sure you disconnected the constant power?

* If the constant wire has been interuppted for more than a few minutes, the computer will lose the memory of what it learned while running. It should start over like it did the first time you started it. Even when I have disconnected the power (both wires) mine seems to run better than it did the first time it started up.

* The high RPMs are definitely programmed for the first minute or so, but I don't remember mine having higher rpms during the computer's 'learning period'.

* How does it run? Is it missing at any RPMs, or is it smooth and strong through the whole power band?

* If you are experiencing any performance loss at higher or lower RPMs it could be the gap on the crank sensor. The first one I got didn't have the paper button. I set it at the recommended gap and it wouldn't start. Hesco recommended increasing the gap to something like .070". It started, but missed at higher RPMs. I decreased the gap to around .050" and it is perfect. The crank sensor is extremely sensitive. You may play around with that to see if it is the problem.

-raymo
Scrambler
258 4.0 Head/MPI,NV4500,D300,4.10's,HS9500
raymo is offline  
post #3 of (permalink) Old 03-06-2001, 02:59 PM
Robert87yj
Guest
 
Posts: n/a
Re: MPI problems again???

I removed the battery complety. So there is no way it still had a power wire connected.
All cylinders were runing rich before so I wanted the computer to reset, it should have if I disconnected the battery right?

Robert87yj[img]/wwwthreads_images/icons/tongue.gif[/img]
4.2 w/<font color=blue>(4.0 head & MPI)</font color=blue> (jeep is down need a new head)
Process of a moonguy after beer
[img]/wwwthreads_images/icons/mad.gif[/img] [img]/wwwthreads_images/icons/frown.gif[/img] [img]/wwwthreads_images/icons/crazy.gif[/img] [img]/wwwthreads_images/icons/wink.gif[/img] [img]/wwwthreads_images/icons/smile.gif[/img] [img]/wwwthreads_images/icons/blush.gif[/img]
Sponsored Links
Advertisement
 
post #4 of (permalink) Old 03-06-2001, 03:30 PM
Old Hand
 
Join Date: Sep 1999
Location: San Diego, CA
Posts: 900
Thanks: 0
Thanked 0 Times in 0 Posts
 
Re: MPI problems again???

Have you run the error codes by hooking up a check engine light? That would be the first thing I would try. It sounds like it could be something like an oxygen sensor. I don't know what other things might be affecting it, but I doubt it is the computer.

As far as taking the battery out, that would definitely reset it.

-raymo
Scrambler
258 4.0 Head/MPI,NV4500,D300,4.10's,HS9500
raymo is offline  
post #5 of (permalink) Old 03-06-2001, 03:41 PM
Way Outta Control
 
Join Date: Sep 1999
Location: The Palouse
Posts: 13,432
Thanks: 1
Thanked 3 Times in 3 Posts
 
Re: MPI problems again???

I'm going to butt in where I know nothing and make a remark so take what I say with a grain of salt... the size of a water softener pellet....

1. If the battery was disconnected, the ECM should show that disconnect within the last 50 on/off cycles. That's a consistant code for Chrysler products.

If it's not showing the disconnect... that alone would raise red flag. The process of the re-learning... Yep, that's the second red flag raised. I vote for a bad ECM unit.

As a double check, force an error, such as uncoupling a sensor and see what the computer will and what it will not pickup.

2. If the engine was running rich after the new fuel pump, it may be delivering more fuel than the regulator can handle. Check the input pressure and the return line pressure.

3. Or... the return line from the regulator may be too small. If you've used an OEM dia. vapor return line as a fuel return line, this could be the problem.

On my Howell TBI I had replaced the return line with a 3/8" line to move the fuel back to the tank fast enough not to raise the pressure at the regulator. This prevented clouds of black smoke from following me. That OEM line enriched the fuel mix because the regulator could not handle the pressure given the smaller OEM return line diameter.


LEVE
LEVE is offline  
Sponsored Links
Advertisement
 
Reply

Quick Reply
Message:
Options

Register Now



In order to be able to post messages on the Off-Road Forums & Discussion Groups 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 email address for yourself.

Email Address:
OR

Log-in










Thread Tools
Show Printable Version Show Printable Version
Email this Page Email this Page
Display Modes
Linear Mode Linear Mode



Posting Rules  
You may not post new threads
You may not 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 On
Pingbacks are On
Refbacks are On

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