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2008 XC70 fuel pressure numbers specifications

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2008-2016 V70
2008-2016 XC70
2007-2016 S80

mrscullini
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Volvo Repair Database 2008 XC70 fuel pressure numbers specifications

Post by mrscullini » Tue Feb 14, 2017 6:00 pm

can somebody with vida/dice please provide observed fuel pressure numbers/specs at both the rail and overall system? i'm interested in readings both at idle and after engine shut down.

or maybe there is an online resource for these numbers?

thanks.

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Re: fuel pressure numbers specifications

Post by oragex » Tue Feb 14, 2017 7:18 pm

Turbo engine? I believe it should be around 45psi at idle.

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Re: fuel pressure numbers specifications

Post by mrscullini » Tue Feb 14, 2017 7:51 pm

oragex wrote:Turbo engine? I believe it should be around 45psi at idle.
thanks. not turbo, n/a 3.2. that's about what i have at idle.

when the engine is shut off, it pretty quickly bleeds down to 0. trying to diagnose a hard cold start with excessive cranking.

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Re: fuel pressure numbers specifications

Post by jimmy57 » Tue Feb 14, 2017 9:40 pm

The fuel pressure will be bout 56 on start when hot and then drop to 45 ish after 45 seconds or so. The fuel pressure should not drop below 29 psi within 20 minutes post shutdown. On that system it can only leak back through fuel pump check valve, leak through overpressure valve, or drop out of a leaking injector. Injector causes it to be flooded if you attempt restart after it has run and shutoff for a bit. If it is the FP check valve or overpressure valve then no black smoke when it starts. Overpressure not serviced and the FP check valve is part of pump. Best to put the whole assembly. When fuel drains out of lines on that system then it will take lots of starter time. That is a dead end system with no return line so to purge air to allow fuel to reach injectors takes injector cycling during cranking.

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Re: fuel pressure numbers specifications

Post by oragex » Wed Feb 15, 2017 6:27 am

Don't know for the 3.2. On the 2.4 non turbo the psi is higher than on the turbo one, by about 10psi. But the 2.4 non turbo and 3.2 are not the same engines

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Re: fuel pressure numbers specifications

Post by mrscullini » Wed Feb 15, 2017 8:14 am

jimmy57 wrote:The fuel pressure will be bout 56 on start when hot and then drop to 45 ish after 45 seconds or so. The fuel pressure should not drop below 29 psi within 20 minutes post shutdown. On that system it can only leak back through fuel pump check valve, leak through overpressure valve, or drop out of a leaking injector. Injector causes it to be flooded if you attempt restart after it has run and shutoff for a bit. If it is the FP check valve or overpressure valve then no black smoke when it starts. Overpressure not serviced and the FP check valve is part of pump. Best to put the whole assembly. When fuel drains out of lines on that system then it will take lots of starter time. That is a dead end system with no return line so to purge air to allow fuel to reach injectors takes injector cycling during cranking.
thanks jimmy. i suspect the fp, however, i have doubts. check this thread for more detailed pressure numbers.

viewtopic.php?f=31&t=79950

my fuel pressure basically drops to 0 after shutdown. however, an immediate restart or even within hours, there is no problem. but in the morning, let's say after sitting overnight, there is excessive cranking, 5 seconds before start up.

the fuel pressure, whether in the morning or an immediate start up is basically the same at 0.

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Re: fuel pressure numbers specifications

Post by jimmy57 » Fri Feb 17, 2017 12:07 pm

Fuel pressure after sitting overnight on a car that starts immediately will usually be zero but there will be fuel in the rail. There is a difference bwtween zero pressure due to the contraction of fuel as it cools and a seepage at FP check valve versus some large leak and the rail draining. That difference is long crank cold due to having to purge air out of injectors via multiple injector cycles. The fact your pressure goes away so quickly is a huge problem. You have not listed black smoke on start with very rough running until the engine runs 15 seconds +/- so I will take injector leak off the list. That would leave fuel pump/sender assembly as the cause. As I said in another post, the cause could be fuel pump check valve which is a prt of the pump or it is the PVV as Volvo calls the max pressure relief valve. Technically there are two valve serving this purpose. The one buiilt into pump is there as an energency overpressure and is there on that model pump for the dozens of different make that use that pump. The one I am referring to is not part of the pump but looks like s fuel pressure regulator on the pump module and is there as the maximum pressure controller in the event the FP sensor fails and the ECM goes to full pump current. Then the ECM knows the pressure will be the approx 600kpa of the PVV for "limp home" or failure mode effects manamgement (FMEM). The PVV could have some piece of something stuck in it and there is no source of the part and the disassembly needed to change it is likely to break plastic housing it is inserted into.

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Re: fuel pressure numbers specifications

Post by mrscullini » Fri Feb 17, 2017 12:32 pm

jimmy57 wrote:Fuel pressure after sitting overnight on a car that starts immediately will usually be zero but there will be fuel in the rail. There is a difference bwtween zero pressure due to the contraction of fuel as it cools and a seepage at FP check valve versus some large leak and the rail draining. That difference is long crank cold due to having to purge air out of injectors via multiple injector cycles. The fact your pressure goes away so quickly is a huge problem. You have not listed black smoke on start with very rough running until the engine runs 15 seconds +/- so I will take injector leak off the list. That would leave fuel pump/sender assembly as the cause. As I said in another post, the cause could be fuel pump check valve which is a prt of the pump or it is the PVV as Volvo calls the max pressure relief valve. Technically there are two valve serving this purpose. The one buiilt into pump is there as an energency overpressure and is there on that model pump for the dozens of different make that use that pump. The one I am referring to is not part of the pump but looks like s fuel pressure regulator on the pump module and is there as the maximum pressure controller in the event the FP sensor fails and the ECM goes to full pump current. Then the ECM knows the pressure will be the approx 600kpa of the PVV for "limp home" or failure mode effects manamgement (FMEM). The PVV could have some piece of something stuck in it and there is no source of the part and the disassembly needed to change it is likely to break plastic housing it is inserted into.
thanks jimmy for the thorough explanation. no black smoke or rough idle, so i too kinda ruled out leaky injectors.

based on what you said, all signs point to the fp.

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