XC90 V8 Intermittent fuel pressure cutout (kinked fuel pump line) Topic is solved

[SHOCKWAVE]

So, I was able to drive the car hard this weekend on a few trips. The issue did not arise while doing so. However, before one of my trips (1-27-18) I started the car and exited the car to pick something up (let it idle). When I returned, the check engine light was on but it was running fine. I proceeded to drive to the store and back without issue.

The next day, I took the laptop and DICE unit out and checked on the code. The readings were a little confusing and the check engine light was no longer on. However, the record indicated the code was signalled on (1-20-18) . The MIL/DTC did not signal on the dash until 1-27-18. As I was looking at different info in VIDA at idle after about 20 minutes, it started to act up. I captured the outputs shown below. See SHOCKWAVE_XC90_PEM_FAILURE_04 for results with the ECM-Fuel rail pressure. Unfortunatly, I did not get ECM-Fuel rail pressure on the other readouts.

Here are my comments and questions (please confirm or deny):

• The ECM-Fuel pressure started to "bounce" and I could feel the change in the engine response.
• The fuel pressure value was bouncing from about 300 to max (650+)
• The ECM-Fuel rail pressure VALUE closely followed the bounce, but you can see in the GRAPH that the value is zero (scale is zero to zero for ECM-Fuel rail pressure)... Am I interpreting the graphical display incorrectly? The graph seems to indicate the pressure sensor is not responding (or reading zero). I'll have to get more results with the fuel pressure at the ECM and rail.
• The bouncing pretty much indicates the PEM is freaking out and is faulty. Not shown, but the pressure was reading a constant 480 kpa.

No codes were thrown during this cycle...but the computer shows one on 1-20-18...DTC printouts attached for the two that remain in the computer.

[abscate]

On edit...the PEM Is not on CANBUS, see diagram above


I thought the PEM had a CANBUS connection onto the CEM when I did my 2005 troubleshoot?

will confirm

I have a spare, working PEM I can send to people to try a swap strategy, btw

[SHOCKWAVE]

Thanks again and for putting the spare idea out there...It would be nice if we could come up with a pass/fail electrical test for the PEM other than swapping one in.

From what I could find the ECM sends a direct signal to the PEM (yellow) (not CAN). I'm not sure if the CEM is reading that signal (blue, I've shown it in aqua). I'm not certain because that line branches to the ejector pump. Maybe that is the duty cycle measuring both pumps...(power in). The PEM varies the voltage to the pump based on what the ECM tells it to do from my understanding.

I was able to get a plot of the vehicle acting up. Seems to happen at idle after 20 minutes and is fairly repeatable. The issue started, went back to normal for a few seconds, and then it kept "blipping".

1) ECM-Fuel Pressure
2) ECM-Fuel Rail Pressure
3) ECM-Fuel Pump, duty cycle

When it starts, pressure drops (1) and (2) and fuel pump duty cycle goes up (3), then stays constant at higher than normal value. Then pressure goes way up and duty cycle goes down.
The subsequent blips have the duty cycle going down with pressure (1) and (2).

I'll most likely get to replacing the PEM this week.

[SHOCKWAVE]

I replaced the PEM this morning, and drove into work. It drove fine. Hopefully, the problem does not reoccur, but I'd still like to figure out a way to determine if the PEM is faulty. I'll post if I find a way to test.

[SHOCKWAVE]

From 372: CEM-3F90 Fuel pump relay. Open circuit or short circuit to ground.
The following applies to vehicles with fuel pump module (PEM): Central electronic module (CEM) checks the voltage feed to the fuel pump module. The Central electronic module (CEM) activates the voltage supply to the fuel pump control module after the checks carried out by the function for the immobilizer have been approved. If Central electronic module (CEM) detects that the voltage on the output to the fuel pump module (PEM) is too low, the diagnostic trouble code is generated. The diagnostic trouble code (DTC) can be diagnosed when the fuel pump is activated.

Fuel pump (FP) control module
The fuel pump control module powers the fuel pump and regulates the output of the pump. The fuel pressure changes with the output of the pump. The fuel pump (FP) control module is supplied with battery voltage by the fuel pump relay and grounded in the car body. The fuel pump relay is controlled by the central electronic module (CEM) at the request of the engine control module (ECM). The engine cannot be started if the power supply to the fuel pump control module is faulty because the fuel pump will not then be powered. The fuel pump control module is controlled by the engine control module (ECM) via serial communication.The fuel pump control module then controls the fuel pump by transmitting pulse width modulated (PWM) voltage on the ground lead for the fuel pump. This means that the voltage drop across the pump changes, and with it the output of the fuel pump.
See also:
There are no diagnostics for the fuel pump control module. The engine control module (ECM) has diagnostics for fuel pressure regulation and the associated components.

See also:
Fuel pressure regulation, diagnostics
The pulse width modulated (PWM) signal from the engine control module (ECM) to the fuel pump control module can be read off. The fuel pump control module is on the outside on the right hand side of the fuel tank.

Fuel pump
The function of the fuel pump is to ensure that the pressure is correct at the delivery lines for the injectors when requested by the fuel pump control module.

The fuel pump consists of:
1. An electrical pump with an integrated safety valve
2. A pressure equalization valve. This valve equalizes rapid pressure peaks which occur, for example, when the injectors close during engine braking. It also contains a non-return valve which ensures that the pressure in the system does not drop when the engine is switched off
3. Fuel level sensor
4. Fuel filter, cannot be replaced separately
5. Relief valve, releases fuel into the pump housing
6. Ejector pump, continuously fills the pump housing with fuel. The fuel always flows from the fuel pump through the ejector and back to the pump housing. The fuel pump is supplied with battery voltage by the fuel pump control module and is grounded in the car body via the fuel pump control module. The engine control module (ECM) has diagnostics for the fuel pump function to ensure that the pressure is correct.

See also:
Fuel pressure regulation, diagnostics
The fuel pump can be activated and its status can be read off. The pressure in the fuel rail can be measured by connecting a manometer to a nipple. This nipple is on the right-hand end of the fuel rail.

Fuel pressure sensor
The pressure sensor is a Piezo resistive type resistor, the resistance of which changes with the pressure. Depending on the pressure in the fuel rail, an analog signal of 0 - 5 V is transmitted to the engine control module (ECM). Low pressure results in low voltage, high pressure gives high voltage. The engine control module (ECM) then uses this signal to adjust the pressure in the fuel rail using the fuel pump control module.
See also: The pressure sensor is supplied with 5 V and grounded in the engine control module (ECM). The pressure sensor transmits a signal indicating the fuel pressure to the engine control module (ECM) on a separate cable. Note! The absolute pressure is displayed when using parameter read outs to read off the fuel pressure. If there is no pressure at the fuel rail, the atmospheric pressure will be displayed.
Hint: The relative pressure (absolute pressure minus atmospheric pressure) is displayed when reading off the fuel pressure via a manometer connected to the fuel rail.

Fuel temperature sensor
The temperature sensor is an NTC sensor. The sensor is supplied with voltage (signal) from and grounded in the engine control module (ECM). The resistance in the sensor changes according to the temperature of the fuel. This provides the engine control module (ECM) with a signal of between 0 - 5 V. Low temperature results in high voltage (high resistance). High temperature results in low voltage (low resistance). The engine control module (ECM) uses the signal to calculate the volume of the fuel.

[SHOCKWAVE]

Fail! After replacing the PEM the issue is still here. Starting stumbling after getting off the freeway and idling at the light. Shut it down and restarted to get control..I shut it off at stops, and was able to make it home. I sat for about 90 seconds at one light, and it seemed to not have the stumble after that. Idled at home, and it was doing fine with one noticeable stumble while I was looking under the hood. I’ll have to consider taking it in for a Volvo evaluation at this point... quite frustrating! I was really hoping to love the Volvo car, but my patience is wearing thin!!

[abscate]

Well the PEM is the expensive thing - only other things are fuel pressure sensor and fuel pump itself.

Why do not do them both and save the Volvo labour bill?

[SHOCKWAVE]

-Fuel pump was replaced twice last year by previous owner. The second time was by Volvo in June.
-I replaced the FPS along with spark plugs, fuel filter (old one was cut open and was like new as it was also replaced with the pump), and air filter.

I ran the car a few time this weekend, and connected VIDA for about +25 minutes with no odd behavior. I can tell something is not right even though it runs "fine". It seems to have infrequent micro-second blips in power, but it is difficult for me to tell since the car is newer to me. It also just feels choked. That may just be my bias though.

Questions/comments:

1. Is ECM- fuel pressure the value calculated by the ECM?
   If so, that should drive any changes in the system. For some reason, the desired pressure falls. That to me seems to be the issue. Things are just wacky from there. The pressure sensor (ECM-fuel rail pressure) closely follows the ECM- fuel pressure signal telling the ECM it is getting what it wants. That phenomena occurs regardless of what the duty cycle of the pump looks like. The fuel pump duty cycle goes up at the same time which is not expected if the ECM wants a lower pressure. And how can the pressure sensor follow the ECM command so closely regardless of pump duty cycle?
2. Does it have to due with violating the thresholds below? The blips on the plots seem to happen about every 5 seconds.
3. The behavior is periodic indicating a software or electrical signal issue, not a mechanical issue. Electrical response is fine most of the time, so no open circuits.
4. Maybe the ECM needs to be "reset" for the new fuel items...?
5. What other parameters can I check that may be out of range? I guess the ECM would throw a DTC if something was awry...

I'm going to try to get some videos up and hopefully someone who knows the engine well will detect something out of sorts...

[abscate]

Have you backplaned the voltage at the PEM from the CEM to see if it is getting B+ +- 0.1V?

[SHOCKWAVE]

No electrical testing yet...Haven't done much of this on an auto so I'll be learning a new skill here. I need to get some backprobes first...However, the CEM would generate a code if the voltage is too low from what I understand of the description I posted ..."From 372: CEM-3F90 Fuel pump relay. Open circuit or short circuit to ground."
(B+ = BL ?)
Test like this?