No Fuel Pressure

J

Jbjohnston1

New Member
Joined
Jun 14, 2021
Messages
4
Location
Amarillo, TX
Need some help!

2000 Jeep Wrangler Sport
4.6L Inline 6 Stroker (new)

Was driving just the other day, 97 degree weather here in Texas, jeep just shut down on me. Power on still, almost like it was out of fuel.
I had just filled up the tank with 91 octane (what i use for the stroker), so i had fuel.
Stopped on the side of the road and tried to start it about 15 min later and it fired right up. Got about a mile down the road and same issue, just stopped as though it lost fuel.
Towed it home, was able to start it up long enough to back it in the garage.
Hooked up fuel pressure gauge, no fuel pressure.
Decided to replace fuel pump even though previous fuel pump was less than a year old.
Replaced fuel pump, checked relay. All was good.
She started right up and i ran it until hot.
Decided to take it out for a spin, put it in reverse and same issue. Shut down as though it had no pressure.
Hooked up gauge and no fuel pressure again.
Listened to the pump and it sounded as though it was running.
At this point, i have no idea what the hell to do or think.
Any suggestions would be much appreciated!
Thanks!
 
If it's losing fuel pressure quickly I'd suspect, in this order, either the fuel pressure regulator or perhaps a leaky fuel injector
 
Hmm. Yea if the pump is running and no pressure then you need to work your way back to the pump. Are you checking the pressure of the fuel at the rail or directly on the line?
If it starts then you have the needed pressure to start.
But not the needed pressure to run and deff not enough to put load on it.
Did they upgrade your fuel system for the stroker kit?
 
When the Jeep is in a no start condition and you turn the key to run can you hear the fuel pump prime for about 2 seconds. Sounds more like a failing crank sensor which can produce similar conditions.
 
Well i know you shouldnt stroke something and not change all the fuel parts. Im not familiar with crank sensor and the fuel system. Is there some sort of saftey shutoff possibly also? maybe your fuel vent line is clogged and it shuts off the pump? that takes 15 seconds to check and fix.
 
Jeffseven777 said:
Hmm. Yea if the pump is running and no pressure then you need to work your way back to the pump. Are you checking the pressure of the fuel at the rail or directly on the line?
If it starts then you have the needed pressure to start.
But not the needed pressure to run and deff not enough to put load on it.
Did they upgrade your fuel system for the stroker kit?
Click to expand...
Checked pressure at the rail.
There was no fuel system upgrade.
it was a crate motor me and the old man put in!
 
TJ4Jim said:
When the Jeep is in a no start condition and you turn the key to run can you hear the fuel pump prime for about 2 seconds. Sounds more like a failing crank sensor which can produce similar conditions.
Click to expand...
I keep hearing about the cps. Its about a $40 part. May go ahead and replace just to see, but i guess I don’t see how that would relate to pressure? But i will check that out! Thank You!
 
Jeffseven777 said:
Hmm maybe you dont have enough pressure to run with the increased bore?
Click to expand...
If your compression ratio when down or up this could cause an issue but it only happens when its Hot? is it possible that when its hot its just enough of a compression drop to screw with it and kills the engine?
 
I have actually seen this issue before like 15 years ago. same exact issue i cant remember exactly how it was resolved i swear i remember there beeing a safety shutoff for the fuel pump when the engine gets to hot but cant remember if this was for a TJ or something else.
 
Do this. Hook up the fuel pressure gauge and film it from a cold start look at the pressure while you give it some gas what is the resting pressure at idle, what is the pressure on some good load? then sit there as its warming up see if you see the pressure going down slowly or if it just drops and dies.
 
There is a shutoff valve on the pump for if you flip over but you replaced all that so you should have it twice. If your fuel regulator is on the rail or something it may have an air diaphragm that uses vacuum, can you send us a picture of your regulator possibly on the fuel rail? if its vacuum powered could be an issue but still shouldnt mess up only with engine temprature.
 
K here you go about fuel shut off switch for jeeps. a 2000 probably is controlled by the PCM.

As computers systems on vehicles gained in intelligences, the auto manufacturers started using the PCM to control fuel flow, without inertia switches. The PCM monitors the engine speed and if it drops below a specific RPM value, the PCM will shut off the fuel supply.
Therefore, if you have a fuel line rupture, the pump will continue to pump until the engine starves for fuel and engine RPMs drop, at that point the PCM shuts down the fuel pump relay, thus, shutting off the fuel pump. Usually when starting a vehicle, the PCM will energize the relay, pressurizing the fuel system, then shut if off after a one or two seconds, until it sees engine RPM above a specified point, then it energizes the relay to allow the engine to run.
With an in-tank fuel pump, if you should roll over, the fuel would not be at the bottom of the tank where the fuel pickup tube is located; therefore, no fuel would be pumped, even if the PCM did not shut off the fuel system.

Now, if Jeep still utilizes an archaic device such as an inertia switch, it is not due to Federal law, it is due to the manufacturer not wanted to spend money in updating their PCM calibrations and functions.
 
Jbjohnston1 said:
I keep hearing about the cps. Its about a $40 part. May go ahead and replace just to see, but i guess I don’t see how that would relate to pressure? But i will check that out! Thank You!
Click to expand...
A fault in the CPS will prevent the pump from running and since you never confirmed the pump was running while trying to get a pressure reading. A failing CPS can happen intermittently behaving as you are experiencing. Don't buy any non OEM and stick with Mopar, NTK or Echlin
 
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