1997 4.0 XJ behaves like running out of fuel

[vaco]

Hi again!
It took some time to get fuel pressure tester but I got it now, still waiting for fuel pump.
I tested the fuel pressure, I get proper results all the time (46-48 PSI), whether the issue shows up or not. I also pressed the pressure release button on the tester while the engine was stalling, I expected that if the engine is starving for fuel then pressing the button will increase stalling effect, but it did not make any difference at all. I also noticed another thing that I did not expect, procedure is:
- I turn ignition on without starting the engine to start fuel pump
- I get proper fuel pressure
- I press the tester release button and now I can get two different results:
1. If I perform this procedure after the engine was working properly the pressure goes to zero in one second or even shorter, only small amount of fuel goes out of the tester, like teaspoon or something like that
2. If I do that after the engine was stalling it takes much longer time (I did not measure that, but like 10 seconds or more) to get the pressure to zero, also it sounds and looks like there was gas and fluid going out of the tester. I get something like 1/4 liter of fuel after that. It looks that compressed gas pushes much more fuel out of the lines in this case

Now I have two questions:
1. If for some reason the fuel is boiling in fuel lines and it evaporates then would the evaporated fuel be a problem for the engine or should it run normally while supplied with gas instead of liquid?
2. Is there a simple way to check whether the gas is air or evaporated fuel?

Thank you in advance.

 

[vaco]

Hi all!
I finally found the source of the problem. It is the upstream O2 sensor. As far as I understand what is happening is: when sensor does not work then ECU thinks that there is too much O2 in exhaust, it increases fuel dose step by step to the moment when it is too rich and engine starts stalling. You can check it by disconnecting the sensor, the connector is on the driver side of engine block and you can reach it from the bottom.
What's interesting: I would expect to get "Check Engine" light when the sensor is broken, but it does not show up, it does not show even when I disconnect the sensor. I checked and the light itself works.

 

[Anak]

Thank you for posting the solution.

Interesting that OBDII does not see the problem and trigger the CEL. Have to file that tidbit away for future reference.

 

[vaco]

I have no idea how should CEL work. I used ELM327 to read error codes and I could see error P0132 after disconnecting the sensor, but I have not seen CEL on at all during problems described in this thread. I would expect it to light when any error occurs, but maybe it shows only more serious errors. I assume CEL works because I have seen it on some time ago when I accidentally disconnected coolant temp. sensor, maybe it broke in the meantime, I will check that.

 

[XJ_ranger]

CEL should flash on then off with key on engine off as a self test.

 

[vaco]

Sorry, I am an idiot, it does, so it works.

 

[Anak]

Just to confirm, the CEL works, but it does not illuminate/flash for this particular O2 sensor problem.

 

[vaco]

Exactly.

 

[gosser66]

I assume the pump you meant is Bosch 67658, but it seems that it is not available, is there any other make that you can recommend?
I searched for 4874173AB and the only pump I found is Airtex E7154 (pump itself, without filter and some other stuff).

I recently replaced my fuel pump in my 98 XJ with a Delphi, DFG1076 from Autozone. I replaced it in December 2023 and no issues so far. My issue was slow starting to where I had to prime the system 2-3 times (turning ignition on & off) before it would send enough fuel to the fuel rail before starting. It starts like a champ now.

 

[vaco]

I recently replaced my fuel pump in my 98 XJ with a Delphi, DFG1076 from Autozone. I replaced it in December 2023 and no issues so far. My issue was slow starting to where I had to prime the system 2-3 times (turning ignition on & off) before it would send enough fuel to the fuel rail before starting. It starts like a champ now.

The Delphi pump has about 25% of 1 star reviews on Amazon, mostly saying that pump died after year or even shorter period.