2005 v70r NA stalled and won't retart, fuel pump?

[abscate]

ECM 926c cross references to a throttle body fault, but if it isnt running well stick with diagnosing that fuel system first.

[goldmandan]

The Rs had a TSB on the fuel pumps going bad. Mine has had 2 pumps put in already. If you have a scanner or fuel pressure gauge, check and see what pressures you have at the rail. Should be around 48 psi. When you first turn the ignition on, do you hear the fuel pump prime? You can have an assistant turn the key on, take the fuel cap off and listen if you hear it come on for a second or 2 when ignition is turned on.

[precopster]

To limp the car home you could try to bypass the PEM and supply power directly to the pump. Make sure this is fused and only connected when ignition is on.

The pump is on the passenger side of a LHD car however access to wiring for the pump will be on the driver's side going to the access port.

An auto electrician can do the above bypass work with a good margin of safety.

[view836]

update on this, had car towed to nearest dealer 100km way. They have had it all week, determined it was a fuel delivery problem they just replaced the fuel pump and fuel filter today and it still isn't running. The PEM is to be replaced tomorrow along with a piece of wiring harness corresponding to these components. What else should I have them look at? What happens if we bypass the PEM and just run the fuel pump full out all the time by powering the fuel pump externally whenever ignition is on?

[precopster]

Safety wise the fuel pump shouldn't run when the engine is stopped with ignition on. The dealer won't be involved in a rewire to accomodate this because of legal reasons.

A reverse circuit oil pressure switch can be used to safely provide chassis to the fuel pump circuit to prevent unwanted operation when the engine is stopped however this requires some modification and extra lines at the block.

If you were just limping home an auto electrician may have done this modification or with a disclaimer for safety he may have bypassed the PEM and wired directly.

The PEM should solve this issue. Good luck

[view836]

is there any sort of similar interlock built in to the ecu to cut power if sime conditions aren't met (like oil pressure) such that a failed sensor would cause it ro cut the fuel pump? just grasping for anything else to check if the new PEM doesn't cure the problem.

[view836]

maybe fuel pressure sensor? when these fail do they fail high or fail low? possible it thinks there is more pressure than there is and ecu calls for insufficient pressure?

[view836]

from what I gather new PEM has not fixed, and dealer has enlisted help of the volvo tech line and FSE (field service engineer I'm guessing?)

wish I had more details as to exactly what they have tested/observed/tried but they are not forthcoming.

[precopster]

The fuel pressure sensor would have pending codes to indicate being out of range.

It could fail in either way; high signal, low signal or no signal.
Vida is very accurate as a diagnostic software. I'm not familiar with the workings of the fuel pump circuit as a safety circuit with engine off nor has this been discussed here to my knowledge . I suspect a wiring issue that is difficult to trace in this imstance, perhaps a CEM or ECM problem. Keep us posted on this one as the outcome will be interesting if not helpful for future similar faults. Sorry it had to be you that has to endure the agony of a lifeless vehicle.

[view836]

Dealer still unable to figure out the problem.

On reflection I'm thinking that this can't be that complicated. If any of you who really know and understand the fuel system and engine controls on this car can look at my logic below, tell me what I'm missing about why this should be so difficult to diagnose.

The car fails to start or remain running every time. So the problem is readily reproducible.

Any connection that is digital i.e. ones and zeros, via a communication protocol, will result in codes if not working. We aren't seeing codes so the problem must be in the analog realm. This means either analog sensors, or wiring/connectors between analog sensors and digital modules, or the integrated circuit signal drivers and A/D or D/A converters within digital modules.

From what I understand the signal from the CEM to PEM may be in fact an analog signal. (*** is it? i.e. a pulse with a certain voltage and variable pulse width and or a voltage level that is not pulsed, either of which would be amplified or interpreted by the PEM, as opposed to a digital communication protocol to a digital circuit in the PEM that would translate to an analog output for the fuel pump?)

When the signal from the CEM to PEM is measured at the PEM, is it within spec? This really should have been determined before making the determination that the pump and/or PEM was bad, but just the fact that this has gone on so long makes me suspect that it wasn't checked. (*** Can it be checked? Shouldn't this be a basic diagnostic capability, if it's analog all you need to do is connect an oscilloscope to see what's going on, if it's digital surely the volvo diagnostic tools should be able to indicate?)

If the signal to the PEM is within spec, then presumably if there is in fact no or low fuel pressure when measured with instruments at the rail, the problem is still downstream of that with the newly-replaced PEM, pump, filter, any check valves that might be inline with the fuel line (e.g. for safety in a rollover), etc..

If the signal is NOT within spec, and again assuming an anolog signal between the CEM and the PEM, then the problem could lie anywhere from how much fuel is being called for by the ECU (meaning that bad information is coming from analog sensors that input to the ECU and it is making an inappropriately low call for fuel), to a problem in the CEM's analog output driver, the connection to the CEM for this wire that goes to the PEM, the connections at the PEM and any intervening connections or harnesses. I would think that a low call for fuel by the ECU could be read through volvo's diagnostic tools (*** is this a correct assumption?), which would provide a diagnostic dividing line between an issue with inputs to the ECU (fuel pressure sensor, crank position sensor, MAF, throttle body etc.etc.) and output from the CEM.

The CEM for this vehicle is in a location where drainage and water ingress issues could definitely affect connector corrosion or the CEM itself and this condition manifested after car was sitting out in rain for several days (had been operating perfectly prior to this). If the wiring to the CEM is shown to be good but signal is bad, CEM or corrosion on connectors to the CEM might be suspected, it could be removed, inspected, sent to Xemodex for corroboration and repair. I'm assuming that the connections between the ECU and CEM are digital ones and that a problem with that communication channel would result in codes.

It seems to me that Volvo's repair and diagnostic procedures for a start/won't continue to run condition must really be deficient for this to prove so difficult for a 100% reproducible no start condition. I don't expect that the dealer technicians would necessarily have encountered every possible failure nor being human to remember every bit of training, but I would expect Volvo's second tier support to be completely versed in everything required to diagnose this issue without resorting to replacing parts willy nilly without having proven that they are not functioning - the fuel pump and PEM that were replaced were most likely working fine.

Very frustrated, and now 2200km away from my car in another country as I had to book a full fare flight home in order to get back to my job on time.

Out of curiousity I looked into moving the car north and I can get it pretty much anywhere in the eastern USA for under $1000. So another option would be to hire a car mover and have it moved (non-operating) to someone that really knows what they are doing.