Novak Conversions Jeep Wrangler TJ radiator

Fuel Pump Replacement

ALASKANMADMAN

ALASKANMADMAN

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Ok not looking for 44psi pump as it seems 49.2 psi is standard operating pressure give or take 5psi. My current one runs at just about 44psi steady if accelerating or just idling. 1999TJ with fresh 4.0 and seems to be running lean as after break in swapped plugs and after a few hundred miles plugs are still pure white. My check valves do not seem to be doing their job as psi drops after shut down a few minutes so going too replace pump but best I can find is 44psi max


Thanks much
 
ALASKANMADMAN said:
Ok not looking for 44psi pump as it seems 49.2 psi is standard operating pressure give or take 5psi. My current one runs at just about 44psi steady if accelerating or just idling. 1999TJ with fresh 4.0 and seems to be running lean as after break in swapped plugs and after a few hundred miles plugs are still pure white. My check valves do not seem to be doing their job as psi drops after shut down a few minutes so going too replace pump but best I can find is 44psi max


Thanks much
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Running lean can definitely be a sign of fuel delivery issues, and the drop in pressure after shutdown points to a potential problem with the check valve in your pump.

For your TJ you want to look for a fuel pump that can provide at least the standard operating pressure of around 49.2 psi. While the 44 psi pumps you've found might work, they could lead to further lean running conditions. Brands like Bosch, AEM, or Delphi typically have options that can deliver the necessary pressure and flow rates without needing a lot of modifications.

Good luck with the replacement, and let us know how it goes!
 
Chris said:
Running lean can definitely be a sign of fuel delivery issues, and the drop in pressure after shutdown points to a potential problem with the check valve in your pump.

For your TJ you want to look for a fuel pump that can provide at least the standard operating pressure of around 49.2 psi. While the 44 psi pumps you've found might work, they could lead to further lean running conditions. Brands like Bosch, AEM, or Delphi typically have options that can deliver the necessary pressure and flow rates without needing a lot of modifications.

Good luck with the replacement, and let us know how it goes!
Click to expand...

Thanks much. Sadly Bosch for older then 05 are non existent and the Delphi that fits is max 44psi sadly. The search continues.
 
ALASKANMADMAN said:
Thanks much. Sadly Bosch for older then 05 are non existent and the Delphi that fits is max 44psi sadly. The search continues.
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I didn’t realize that about the Delphi unit. I could have sworn others have had success with the Delphi unit on the forum. Maybe someone will chime in with feedback.
 
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Chris said:
I didn’t realize that about the Delphi unit. I could have sworn others have had success with the Delphi unit on the forum. Maybe someone will chime in with feedback.
Click to expand...

I replaced my OEM pump with a Delphi when the check valve went bad. Has been running like a top (or as close as a TJ can get to a top) ever since (2 years or so).
 
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Have you verified your fuel pressure tester with another tester to verify you're reading correct numbers?

My older Bosch pump couldn't put out more that 33 psi and I could see it in the fuel trims but it never ran lean.

After messing around with rebuilding several OEM fuel pump frames using the forum instructions in the resources section...using Bosch Brazil pumps and 2 new regulators...I gave up and bought a Brute Power assembly from Rock Auto... almost the cheapest pump they had. About $85 shipped.

That pump has survived about 10k miles...driving from Oregon to the Rubicon and Moab over the last couple of years and a lot of fuel tank pounding and scraping. YMMV.

I've seen way too many horror stories with Delphi pumps...one after another failing and failing and failing.

-Mac
 
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ALASKANMADMAN said:
Thanks much. Sadly Bosch for older then 05 are non existent and the Delphi that fits is max 44psi sadly. The search continues.
Click to expand...
For what it's worth , In 2012 I replaced my fuel pump in a 99 TJ 4.0 with a Airtex pump from Advance Auto. No issues in performance or codes .
I know that's against the forum picks , however it has done great fuel pump kinda things for 13 years . ;)
 
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Delphi are great pumps and fairly reliable and your rig will run ok from my research but put a fuel pressure gauge on the rail and see your just getting 44psi while the rig craves 49.2psi +/- 5psi So imo 52psi would be optimum. I found a carter that minimum psi is 49.2 and anticipate improved function being I also have the 62mm throttle body and the upgraded injectors. I will update if anyone sends request.
 
macleanflood said:
Have you verified your fuel pressure tester with another tester to verify you're reading correct numbers?

My older Bosch pump couldn't put out more that 33 psi and I could see it in the fuel trims but it never ran lean.

After messing around with rebuilding several OEM fuel pump frames using the forum instructions in the resources section...using Bosch Brazil pumps and 2 new regulators...I gave up and bought a Brute Power assembly from Rock Auto... almost the cheapest pump they had. About $85 shipped.

That pump has survived about 10k miles...driving from Oregon to the Rubicon and Moab over the last couple of years and a lot of fuel tank pounding and scraping. YMMV.

I've seen way too many horror stories with Delphi pumps...one after another failing and failing and failing.

-Mac
Click to expand...

Yep checked with another meter. Went with the carter fuel pump and we will wait and see. Thanks man
 
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ALASKANMADMAN said:
Ok not looking for 44psi pump as it seems 49.2 psi is standard operating pressure give or take 5psi. My current one runs at just about 44psi steady if accelerating or just idling. 1999TJ with fresh 4.0 and seems to be running lean as after break in swapped plugs and after a few hundred miles plugs are still pure white. My check valves do not seem to be doing their job as psi drops after shut down a few minutes so going too replace pump but best I can find is 44psi max


Thanks much
Click to expand...

I’ve never seen a fuel pump advertise its psi?where are you getting this?
 
Moglocker said:
I’ve never seen a fuel pump advertise its psi?where are you getting this?
Click to expand...

Need to check in the specs and other data. Lots don't reference tho so LOTS of cross checking diffrent distributor sites. Also lots of calls to places like summit etc etc and you'd be suprised how many do not have the info either sadly. Spent about 18 actual hours reseacing.....what a pain
 
Moglocker said:
I’ve never seen a fuel pump advertise its psi?where are you getting this?
Click to expand...

Here are screenshot from the manufacturing company and next is from ebay. I brought unit off anazon as was cheaper but they didn't have specs but since I researched I already knew what I wanted.

Screenshot_20250515-205443.png


Screenshot_20250515-205246.png
 
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Fuel pumps do not do pressure regulation, they just pump. While it is important that the pump can supply at least a minimum of the intended pressure, most should supply much more (100psi or higher).

The TJ fuel pump assembly has a pressure regulator at the top. It regulates pressure in the fuel lines by returning any excess over the design 49 psi back down into the tank.

If you have installed a pump that can deliver at least 49 psi but still have a pressure issue, the regulator may require replacement.
 
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ALASKANMADMAN said:
Here are screenshot from the manufacturing company and next is from ebay. I brought unit off anazon as was cheaper but they didn't have specs but since I researched I already knew what I wanted.

View attachment 616144

View attachment 616145
Click to expand...

ALASKANMADMAN said:
Here are screenshot from the manufacturing company and next is from ebay. I brought unit off anazon as was cheaper but they didn't have specs but since I researched I already knew what I wanted.

View attachment 616144

View attachment 616145
Click to expand...
Which one did you buy?would like to see the pressure when installed
 
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Correct and I purchased a pump that will supply a minimum of 49.2psi. as well as a minimum of 20gph. The maximum is 150psi and the regulator will componste for these pressures. After lots of research I found a majority of pumps would on provide 44psi MAXIMUM pressure and while your 4.0 will function adequately it will indeed be lacking in performance. Thank you for your reply.
Brimstone said:
Fuel pumps do not do pressure regulation, they just pump. While it is important that the pump can supply at least a minimum of the intended pressure, most should supply much more (100psi or higher).

The TJ fuel pump assembly has a pressure regulator at the top. It regulates pressure in the fuel lines by returning any excess over the design 49 psi back down into the tank.

If you have installed a pump that can deliver at least 49 psi but still have a pressure issue, the regulator may require replacement.
Click to expand...
 
Here's a stupid idea from left field: How about an old fashioned external lift pump? Feasible? Pros? Cons?

Just wondering...
 
Zorba said:
Here's a stupid idea from left field: How about an old fashioned external lift pump? Feasible? Pros? Cons?

Just wondering...
Click to expand...

Of course you can ..... but there are considerations, external pumps are noisy , they get hot because they aren't cooled with fuel , packaging is a little harder in a TJ. to stay clear of drive line and exhaust , etc...

That said it could be real good , you could run a nice pressure regulator and return fuel line and a easy to get to filter ( not really sure this is needed as much as it once was ) . You could easily adjust the pressure to change performance and play with the tune .

However , you still shouldn't install a GMC 305 in your TJU... :LOL:
 
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