XJ with 93 5.2 V8 swap

NICK-TJ

NICK-TJ

"Si Vis Pacem, Para Bellum"
Joined
Jul 30, 2013
Location
Granite Quarry
I picked up a 89 XJ a few months back that has a motor swap. The 5.2 V8 came out of a 93 ZJ.

It runs like a top, but when you try to accelerate quickly it sputters. If you roll out of the throttle a little then it takes off like a rocket.


The previous owner, that had the swap done told me that during the swap they left a sensor/ connector or something of the sort out. And that because of this it's sending a default fuel pressure that is higher than what it needs and is flooding the motor.

I'm not 100% sure what to think. I ran some seam foam through the vaccumn line and put a can in the tank as well. My next step is to change the fuel filter and if that doesn't work change the fuel pressure regulator and then fuel pump.

Can anyone offer any insight? I'm use to the I6 4.0. Could really use some ideas.
 

Attachments

  • IMG_1243.JPG
    IMG_1243.JPG
    184.8 KB · Views: 2,068
  • IMG_1218.JPG
    IMG_1218.JPG
    137.2 KB · Views: 585
Check the fuel pressure with a gauge and if it's to high you could run a aftermarket adjustable regulator I don't know if the factory pump can keep up with a v8 when you Matt it does it smoke

Sent from my Z963U using Tapatalk
 
I was told that the fuel tank and the fuel pump came from the grand cherokee. Don't smoke at all, sounds great other than trying to quickly accelerate. I'll see if I can get my hands on a gauge, and start looking at some options for an adjustable regulator.


Bhudgins said:
Check the fuel pressure with a gauge and if it's to high you could run a aftermarket adjustable regulator I don't know if the factory pump can keep up with a v8 when you Matt it does it smoke

Sent from my Z963U using Tapatalk
Click to expand...
 
Sorry for neglecting the post, I put a new fuel filter and TPS on it this evening. No noticeable changes. Stupid me forgot to get the fuel pressure gauge. Going to pick one up tomorrow. Any ideas on where I could look for the adjustable fuel pressure regulator?
 
hurt4x4 said:
I had a 96 grand cherokee that was doing the same as you described and ended up being a bad TPS. it might be worth checking it out.
Click to expand...
Bhudgins said:
Check the fuel pressure with a gauge and if it's to high you could run a aftermarket adjustable regulator I don't know if the factory pump can keep up with a v8 when you Matt it does it smoke

Sent from my Z963U using Tapatalk
Click to expand...


So after replacing the fuel filter and tps and having no change I went to the parts store and picked up a fuel pressure tester ($150) to rent. After a hour I realized the tester was garbage took it back and got a new one. Jeep is reading around 36psi running. Which if what I found is correct it should be closer to 39psi. Not a huge deal, what got my attention is when I cut the jeep off it took no time for the gauge to drop from 36 psi down to 20psi or below. So I'm guess I have a leaky injector. Do either of you think that could be my hesitation problem? Thanks again for the advice.
 
Could be injector or pump bleeding, or regulator bleeding. Block return hose and check. Pressurize and block supply line. Those two tests will tell your leak source. Perform volume test, engine off, and pressure test under load hot.
 
Oh if it's a zj tank, it's a returnless fuel system. You can still block off the supply line and see if it's injector or pump/regulator
 
a_kelley said:
Could be injector or pump bleeding, or regulator bleeding. Block return hose and check. Pressurize and block supply line. Those two tests will tell your leak source. Perform volume test, engine off, and pressure test under load hot.
Click to expand...
Bhudgins said:
What he ^ said I had a bad regulator that gave me the same semptoms

Sent from my Z963U using Tapatalk
Click to expand...
a_kelley said:
Oh if it's a zj tank, it's a returnless fuel system. You can still block off the supply line and see if it's injector or pump/regulator
Click to expand...


Thanks for the help, I put a new regulator on it yesterday as well. I know I know, quit throwing parts at it and find the problem. I'm guessing it would be the injector bleeding, since I tested the fuel pressure after putting the new regulator on.

I hate that I bought this jeep with the swap done, only because there is so much I don't know about it. I was told it is the zj tank and fuel pump.

If anyone is near mount pleasant (between Salisbury and concord) and wants to help trouble shoot I will supply the pizza and beer
 
What year is the ZJ pump and tank?
The 93-95, maybe 96 too, had rail mounted regulators. You can test for injector leaks and pump leaks like @a_kelley said. Just by blocking return and feed lines.
 
a_kelley said:
If the regulator is tank mounted I would've put in a whole sending unit with pump. More money but better warranty.
Click to expand...
Jody Treadway said:
What year is the ZJ pump and tank?
The 93-95, maybe 96 too, had rail mounted regulators. You can test for injector leaks and pump leaks like @a_kelley said. Just by blocking return and feed lines.
Click to expand...


The FPS is rail mounted. The motor tank and fuel pump are from a 93 ZJ. When I did the leak down test it dropped very quickly once I cut the jeep off. I didn't know I was suppose to block return lines and such since all the videos I watched basically said hook the gauge up and start the jeep, cut off and watch gauge.

Also, I found some info from another forum (don't remember where) that said the early model zj's tank or tank liner would start detioratuing and contaminate the fuel pump and sock. Any of this sounds possible?
 
ZJ tanks could come apart and clog up the pickup sock. But if yours hasn't done it by now, it ain't gonna.
By building pressure and then blocking off either the pressure or return side, you are eliminating 1/2 of the system as the culprit. Meaning if you have 39 psi and block off the pressure side and the pressure still drops, you know it's on the return side and vise versa.
 
Jody Treadway said:
ZJ tanks could come apart and clog up the pickup sock. But if yours hasn't done it by now, it ain't gonna.
By building pressure and then blocking off either the pressure or return side, you are eliminating 1/2 of the system as the culprit. Meaning if you have 39 psi and block off the pressure side and the pressure still drops, you know it's on the return side and vise versa.
Click to expand...

Mostly makes sense to me. I consider myself a certified parts changed when it comes to the motor. Anything else I'm very comfortable with on the jeep.

How would I "block off" the pressure and/ or return side? Thanks for the help it is greatly appreciated.
 
take the line off the tank sender, insert a section of hose with a quick connect off a trashed fuel rail or something and crimp the rubber section with vice grips/line clamps,
 
Back
Top