2008 xc70 cold hard start battles

mrscullini · Post by **mrscullini** » 10 Feb 2017, 07:14

i'm sorry, i know cross post from swedespeed.

96k on the clock. battling the hard cold starts. thinking it was the fuel pump, however, before dropping ~$1500 digging a little deeper.

the symptom is hard cold start by excessive cranking before eventual start. the excessive cranking takes a few seconds. seems to happen after sitting over night. does not seem to be an issue after sitting for a couple of hours or immediate restart.

some fuel pressure readings;

after sitting for a few hours
rail pressure- -11 kpa
fuel pressure- 71 kpa

immediate after start up
rail pressure- 420 kpa
fuel pressure- 500 kpa

at idle (minute or 2 after start up)
rail pressure- 380 kpa
fuel pressure- 460 kpa

after engine shut off, the pressure will drop to the "after sitting" numbers above within about 5 minutes. i have not checked the pressure in the morning. however, i don't think it can drop much more. -11 kpa is -1.5 psi, i assume this is relative pressure. i'm at 6000 ft and absolute atmospheric pressure is approximately 12 psi, so at the rail, i'm pretty close to atmospheric pressure at my elevation.

where i'm going with this i'm beginning to question the fuel pump and/or pressure drop off being the issue. i've got a "fuel pump check" error in vida, no code. however, drilling down in vida, it does indicate corrosion/loose pin on the cem, #c2:76. so a few questions,

1. does anybody have fuel pressure numbers documented for comparison to mine?
2. has anybody had an issue with pins on the cem?
3. how do you remove the cem in this model?

mrscullini · Post by **mrscullini** » 10 Feb 2017, 11:36

new observation, check pressures this morning before start up,

rail pressure- -8 kpa
fuel pressure- 74 kpa

basically a 3 kpa rise. i attribute this to the car being parked on an inclined driveway with the front down. 3 kpa is 1' of h2o, that is close given the density of gas to water.

the car started right up this morning, no excessive cranking. making me question the issue of a check valve in a fuel pump.

can somebody with a p3 and no starting issues check your fuel pressures? this would be great to compare. thanks.

mrscullini · Post by **mrscullini** » 19 Aug 2017, 06:37

for those of you that may be battling this issue, stepping on the brake will cycle the fuel pump. you can hear the pump run and you can hear the relay cycle under the glove box. seems to be a bandaid.

perhaps old news, thought i would share.

hornetv6 · Post by **hornetv6** » 25 Oct 2018, 13:04

If you hear the fuel pump running when you first step on the brake. It means the fuel is being sucked back into the tank when the car is turned off. It is only an inconvenience. The cure is a new fuel pump.

Astrit · Post by **Astrit** » 02 Dec 2021, 01:02

Hi I have a p3 2008 xc70 and have been suffering from long crank times and also have a code for low rail fuel pressure. I used a cheap scan tool to observe readings on the fuel pressure and they seem to be within spec around 380 kpa or 55 psi. It doesn’t seem to drop while driving and I haven’t checked how much it has dropped after shutting off. I don’t think my scan tool can make any readings when the car is off but I will have to check. I’ve digged deep and I’ve heard that if the pressure is good it can be a fuel pressure sensor issue which is located on the rail. Would anybody be able to give me some advice on this ?

Post by **RickHaleParker** » 02 Dec 2021, 05:11

Astrit wrote: ↑02 Dec 2021, 01:02 Hi I have a p3 2008 xc70 and have been suffering from long crank times and also have a code for low rail fuel pressure.

Turn on the car on and wait for 10 seconds before you crank. If the fuel pressure is bleeding off this will give the pump time to bring the pressure back up and the car will start. That is if fuel pressure is the problem.

Where there any other codes like P0116 Temperature sensor. We get a rash of no start / hard to start every year because of temperature sensors. Here is another discussion that covers this issue.