91 YJ with a 98 cherokee engine, fuel pressure question - JeepForum.com
Search  
Sign Up   Today's Posts
User: Pass: Remember?
Advertise Here
Jeep Home Jeep Forum Jeep Classifieds Jeep Registry JeepSpace Jeep Reviews Jeep Gallery Jeep Clubs Jeep Groups Jeep Videos Jeep Events Jeep Articles
Go Back JeepForum.com > Models > Jeep Wrangler Forums > YJ Wrangler Technical Forum > 91 YJ with a 98 cherokee engine, fuel pressure question

Metalcloak's Black Friday & Small Business Saturday SaNEW!! HMF 50"-52" light bar mounting brackets!! NEW JK WRANGLER GRAB BARS NOW at ROCKRIDGE4WD

Reply
Unread 09-01-2013, 08:58 PM   #1
D0T-C0M
Registered User
2002 TJ Wrangler 
 
Join Date: Jul 2013
Location: Tracadie, NB
Posts: 484
91 YJ with a 98 cherokee engine, fuel pressure question

My friend bought a YJ with a 4L 98 cherokee engine in it. He has a fuel pump problem and wants to change it but I told him that I believe the YJ 4.0L uses the old injector that run at 39psi. The 98 4.0L should run at 49psi as per the service manual. What does he have to do in order get the proper fuel pressure, adjustable regulator? TJ swap tank?

D0T-C0M is offline   Reply With Quote Quick reply to this message
Unread 09-01-2013, 09:48 PM   #2
stenyeart
Member
 
stenyeart's Avatar
1990 YJ Wrangler 
 
Join Date: Sep 2007
Location: Lewiston, Idaho
Posts: 195
Is he running a return line fuel rail or a return less?

I would assume it is a return line and he would just buy the yj pump. Up front you just need to find the correct FPR to keep the rail at 49 psi. The yj pump will keep up just fine with the higher pressure. This is how I did my obd2 4.0 swap. If you need the info on the what FPR to buy, let me know and I can look it up.
stenyeart is offline   Reply With Quote Quick reply to this message
Unread 09-01-2013, 10:28 PM   #3
D0T-C0M
Registered User
2002 TJ Wrangler 
 
Join Date: Jul 2013
Location: Tracadie, NB
Posts: 484
I think he told me that there were 2 pipes coming from his tank. I'll ask him tomorrow to see what he has to make sure?

He did say that there isn't a regulator on top up the tank like my TJ. Where is the fuel regulator located on a YJ?

By all means if you have the info on which proper regulator he needs please post it so I can pass the info along to him.

Thanks a lot
D0T-C0M is offline   Reply With Quote Quick reply to this message
Unread 09-01-2013, 11:17 PM   #4
stenyeart
Member
 
stenyeart's Avatar
1990 YJ Wrangler 
 
Join Date: Sep 2007
Location: Lewiston, Idaho
Posts: 195
The regulator is on the front of the fuel rail. This is the regulator you need. http://www.naxja.org/forum/showthread.php?t=1043808

Buying one of these will be a lot cheaper than a hesco adjustable regulator and it is a direct bolt in.


Look at the fuel rail. There should be two lines connecting to it at the front of the engine and the FPR located on the same end as the hoses. Of course this is assuming he has the return system. Look at the pic in post #7 here. http://www.jeepforum.com/forum/f12/w...4-0-a-1198259/
stenyeart is offline   Reply With Quote Quick reply to this message
Unread 09-02-2013, 07:34 AM   #5
Que89YJ
Web Wheeler
1989 YJ Wrangler 
 
Join Date: Apr 2008
Location: Detroit, Michigan
Posts: 15,608
It sounds like he is just doing a block swap and he already had it setup for the fuel injection. What year yj is it and did he change out any electronics?
Que89YJ is offline   Reply With Quote Quick reply to this message
Unread 09-02-2013, 07:55 AM   #6
D0T-C0M
Registered User
2002 TJ Wrangler 
 
Join Date: Jul 2013
Location: Tracadie, NB
Posts: 484
Quote:
Originally Posted by Que89YJ View Post
It sounds like he is just doing a block swap and he already had it setup for the fuel injection. What year yj is it and did he change out any electronics?
His yj was already fuel injection and he swaped his 91 fuel injection 4.0L for a 98 cherokee engine 4.0L . Everything else is the original wiring.
D0T-C0M is offline   Reply With Quote Quick reply to this message
Unread 09-02-2013, 09:12 AM   #7
Que89YJ
Web Wheeler
1989 YJ Wrangler 
 
Join Date: Apr 2008
Location: Detroit, Michigan
Posts: 15,608
So the only thing he did is swap the block, then the fuel system is the original as well as the electronics. Did he use the 91 fuel rail? The regulator is on the fuel rail on the YJ. Did he put in a temp sensor for the ecu? The 98 block only had one and used it for both the gauges and the ecu. The 91 YJ had a sensor for both and it is important for the ecu to have both. What is his exact issue with the fuel pressure?
Que89YJ is offline   Reply With Quote Quick reply to this message
Unread 09-02-2013, 03:40 PM   #8
D0T-C0M
Registered User
2002 TJ Wrangler 
 
Join Date: Jul 2013
Location: Tracadie, NB
Posts: 484
He had told me that the PO had changed the complete engine but I drove over today and it would seem that he only changed the block and is using fuel rail of the 91 so no changes to the regulator is needed. Below is the pics of one of the injectors closeup. Its a
'91-'93
part#33007127
Color:Brown,
Running pressure:39psi,
fuel flow: 21.0lb/hr



Here is his header



The problem he is having is he suspected a bad pump but found that his regulator was faulty because he wasn't getting enough pressure. He wanted to change it but then I asked him if he had the 98 fuel injectors or the 91. He said that they were the 98s. This is where I told him that he would need a different regulator and the stock one wouldn't work. After checking myself, he was wrong.

Sorry for wasting everyone's time.
D0T-C0M is offline   Reply With Quote Quick reply to this message
Unread 09-02-2013, 05:23 PM   #9
Que89YJ
Web Wheeler
1989 YJ Wrangler 
 
Join Date: Apr 2008
Location: Detroit, Michigan
Posts: 15,608
No waste of time. The regulator was bad and the pressure was low? Usually the diaphragm rips and the pressure goes high. It's not a waste for the next person searching for a fuel pressure problem. Thanks for posting the fix.
Que89YJ is offline   Reply With Quote Quick reply to this message
Unread 09-02-2013, 07:12 PM   #10
D0T-C0M
Registered User
2002 TJ Wrangler 
 
Join Date: Jul 2013
Location: Tracadie, NB
Posts: 484
Where is the check valve in the fuel system of the 91 YJ? In the pump and/or regulator?
D0T-C0M is offline   Reply With Quote Quick reply to this message
Unread 09-02-2013, 07:25 PM   #11
Que89YJ
Web Wheeler
1989 YJ Wrangler 
 
Join Date: Apr 2008
Location: Detroit, Michigan
Posts: 15,608
It's integrated into the fuel pump. I don't know if you checked it bit you should maintain 20 psi for 20 minutes after shutdown.
Que89YJ is offline   Reply With Quote Quick reply to this message
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.
Note: All free e-mails have been banned due to mis-use. (Yahoo, Gmail, Hotmail, etc.)
Don't have a non-free e-mail address? Click here for a solution: Manual Account Creation
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






Jeep, Wrangler, Cherokee, Grand Cherokee, and other models are copyrighted and trademarked to Jeep/Chrysler Corporation. JeepForum.com is not in any way associated with Jeep or the Chrysler Corp.