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Unread 07-11-2013, 02:34 PM   #1
SubLim3
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Jeep TJ Fuel Pressure Regulator bypass

The new 5.7 Vortec V8 now starts for about a second and then immediately dies and it will do this over and over again. I'm almost certain its not getting enough fuel. although the pump on a Jeep is capable of about 90 psi it is regulated to 49 PSI back at the in tank regulator. I have to figure out how to bypass that. Supposedlyt 05-06 TJ's came with stock pumps that could put out 60 PSI so I may look into swapping the regulator or the entire fuel pump from my 04 for an 06. Not sure whats compatible yet. My other option is Novak(1997-2004 TJ, XJ Fuel System Integration for GM Gen III+ Engines) but the CNC part I need to bypass the regulator is on back order until they get their lathe up and running.
I can't use an in line pump if the FPR is located before it. Anybody have any knowledge of whats compatible between 04 and 05/6 or other options to bypass my existing FPR and still utilize the in tank pump?

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Unread 07-11-2013, 05:28 PM   #2
Jeepsr4me
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That issue does not sound fuel related.
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Unread 07-11-2013, 06:39 PM   #3
Jerry Bransford
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That doesn't make me think of a fuel pressure problem, that sounds more like a security key issue where the computer you're using is looking for the right igntion key which has a transponder chip in it.
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Unread 07-11-2013, 09:39 PM   #4
SubLim3
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I think youre refering to VATS which Howell ensured me they bypassed before they sent me the PCM. I'm working on upping the fuel pressure for now and then if the problem continues I will send the PCM back to Howell.

Does anyone know if a factory fuel pump from an 06 TJ will fit in an 04 TJ tank?
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Unread 07-12-2013, 05:12 AM   #5
Jeepsr4me
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If the engine will crank and run then the pressure to run it is OK. Not saying it is the right pressure. Just at idle you need very little fuel. So your issue is going to be in that computer or the pump is not staying running.
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Unread 07-12-2013, 05:37 AM   #6
kloppk
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See if she'll keep running if you spray starting fluid in the TB. If it does you have a fuel problem. If not it's a spark problem.

If it looks like a spark problem I'd suggest watching the spark when you start it and see if the spark stops just as it starts to stall.
Use a noid light or other means to watch the spark.
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Unread 07-12-2013, 11:11 AM   #7
tbburg
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Have you done any diagnostic work, or is the fuel pressure problem just a guess? Before spending money on a pump/regulator(about 300 bucks, I think) put a pressure gauge on the fuel rail. Have someone start it and watch for a pressure drop. If you see a big pressure drop, but it doesn't drop to zero, it's a feed/pressure issue. If the pressure drops to zero, the pump is shutting off/not supplying fuel with the key in the "ignition on" position.

A low pressure condition usually allows the engine to idle but it bogs down/cuts out when you rev above a certain throttle position.
My bet is either pump not running or the above mentioned SKIM module not disabled.
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Unread 07-12-2013, 03:38 PM   #8
SubLim3
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It turns out to be a fuel problem but I'm not entirely convinced that its not VATS killing the injector pulse. The Jeep may have something called SKIM but that's irrelevant considering I'm using a Chevy PCM which has VATS. It turns out(I'm no Chevy expert) Vats will let your motor run for about 3-4 seconds and then stop giving the injectors pulse(anti-theft). I have now installed the 06 fuel pump and run a PSI test at the motor. I'm getting 55PSI with the key on which drops to about 53 once I start the motor. I also noticed the motor will keep running if I spray carb cleaner in(Fuel Pressure still steady). This means to me that it has steady fuel pressure but the injectors are not firing. Why else would it continue to run depending on the carb cleaner?

More importantly: I haven't seen the 04-06 fuel pump compatibility issue answered anywhere so after realizing how hard it would be to bypass the 04 fuel pressure regulator on my 04 fuel pump assembly- I made an attempt but I didn't like my sloppy work. I decided to buy an 06 fuel pump off Amazon for 140$. Now, did it fit? No. Not at first but w very minor mods it worked just fine. I want to put a few photos for other people who want to avoid spending 200+ dollars for the Novak FPR bypass.
Here's a description of the photos you're looking at.
1. The stock 04 fuel tank
2. The Fuel pump assembly from an 04 TJ. I attempted to make a temporary bypass until Novak shipped me the FPR bypass. I wasn't pleased with this idea and I purposely made sure I only altered the FPR which can be replaced.
3. Both the 04 and 06 fuel pump assemblies side by side.
4. The 06 Fuel pump assembly top which has to be ground down a minor amount to get the proper diameter for the screw on plastic top to be able to hold down the assembly into the tank. Pay attention to the wiring before putting the pump in the tank. Takes out the guess work.
5. The 06 pump after modification ready for mounting.

This mod got me 53-55PSI at the fuel rail which is still low for a 5.7 Vortec V8 but considering the FPR is closer to 60PSI on the 06 I will add an inline if necessary.

Hope this helps everyone!
photo2.jpg

image1.jpeg

image3.jpeg

photo.jpg

image2.jpeg


Last edited by SubLim3; 07-12-2013 at 03:58 PM..
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Unread 07-12-2013, 07:27 PM   #9
Jeepsr4me
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computer is shutting those injectors off then,. And thats the computers doings.
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Unread 07-18-2013, 10:38 PM   #10
SubLim3
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I finally have the engine idling and my issue seems to have been mostly vacuum related. I'm working on getting the stock gauges to work now. I have the PCM for the Chevy motor and 4l60 from Howell and it works great but it is specific to the 5.7 and in no way tailored to a Jeep install. I spoke with Howell and the only way to get my stock gauges to work is to run the Jeep OE PCM as well. I need to use the Jeep six cylinder sending units retro fitted into the V8 in order to fool the Jeep OE computer into thinking it is still reading the six cylinder vitals still. I found out the hard way that you can't simply wire directly to the gauges because they get their data after it's been processed and decoded by the Jeep OE PCM. I've plumbed the water temp sensor and the oil pressure sensor into the motor and then wired them to the OE PCM and neither are working my stock gauges. I'm beginning to wonder if this is because I have removed the Air Bag computer. Does anyone know if you need to keep the air bag computer in line in order to run the OE PCM properly?? If so I'm screwed because I made the mistake of chucking it along with the plugs that attached it to my original Jeep OE harness.
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Unread 01-06-2014, 06:38 PM   #11
Hd60mike
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I know this post is 6 months old.but I received my Novak bypass kit as I thought overpriced for what I received.if I had removed the cartridge and looked at it before hand I would have realized the easy answer.remove the factory regulator place in a bench vise cut in half remove the guts re-weld and replace .get a brass or stainless 90 for a return and done for about 20 bucks.

Just an update Novak has changed their kit from the one a friend ordered almost 2 years ago .it used to offer a billet aluminum bypass with a barb on the bottom and a section of line to attach to the pump after they had you hack up your stock cartridge.the one they offer today is a drop in replacement billet piece which requires no modification to the cartridge .

If their directions didn't suck so bad and I didn't jump the gun and go to hacking up my cartridge looking between instructions two years apart trying to make a 170.00 **** kit work I would have sent it back and modified the the stock regulator my damn self!

In all fairness to Novak they were more than happy to make the problem right .they have 2 day aired the old style bypass and have realized they have a serious problem with their instruction sheet

Last edited by Hd60mike; 01-06-2014 at 06:41 PM.. Reason: Fairness
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Unread 03-15-2014, 12:09 PM   #12
theblackbox
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Quote:
Originally Posted by Hd60mike View Post
I know this post is 6 months old.but I received my Novak bypass kit as I thought overpriced for what I received.if I had removed the cartridge and looked at it before hand I would have realized the easy answer.remove the factory regulator place in a bench vise cut in half remove the guts re-weld and replace .get a brass or stainless 90 for a return and done for about 20 bucks.

Just an update Novak has changed their kit from the one a friend ordered almost 2 years ago .it used to offer a billet aluminum bypass with a barb on the bottom and a section of line to attach to the pump after they had you hack up your stock cartridge.the one they offer today is a drop in replacement billet piece which requires no modification to the cartridge .

If their directions didn't suck so bad and I didn't jump the gun and go to hacking up my cartridge looking between instructions two years apart trying to make a 170.00 **** kit work I would have sent it back and modified the the stock regulator my damn self!

In all fairness to Novak they were more than happy to make the problem right .they have 2 day aired the old style bypass and have realized they have a serious problem with their instruction sheet
so what all do you have to do to modify the stock regulator then exactly?
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