Hi All,

First time posting as I'm at my wits end with my car, apologies for the long post. I have owned my car for 2 years with no major issues, kept up to date with regular maintenance as i want this car to last a long time. Took my car in for a service in February and went a bit overboard, getting almost every service item changed even if it only had it done last year (as the previous owner missed services). Now onto the issue:

4 days after getting the car back from its service, the engine started but sounded like it had a misfire, shut the engine off immediately and then restarted with no issues. Suspected this was due to the fuel filter being replaced and left it at that. A week later, the fault happened again, same process, turn off, then back on and all ok. This would only happen when the car was left for a long period of time e.g. overnight. Took it back to the service centre, they examined the car but could not find anything wrong and no DTC's active or stored. The start up issues were not present when they started the car the morning after dropping it off. Got the car back from them and low and behold, the fault was back!

Tried using premium BP fuel, no difference made. Bought a Carly scanner to see if any fault codes would show up when starting the car at home, but nothing obvious was showing up (i have a retrofit apple carplay system fitted so shows audio faults). Tried starting the car up in a different way, usually i would get in the car, foot on the brake then press the start button. I swapped to pressing the start button twice without my foot on the brake, leaving the ignition on for 10 seconds before starting, and could not get the fault to come back up (this was trialled over 6 days). The morning after, i tried starting the car "normally" and the fault came back. Was advised by another garage to point the engine downhill overnight then try starting the car normally - the fault did NOT come back. Had the fuel filter replaced by the service centre to see if it was a dodgy filter but this did not resolve the issue.

Tried checking the battery to see if there was a drain, causing the battery voltage to drop after longer periods of time. After being left stood overnight for 13 hours, the battery dropped down to 9.0Vdc when cranking. Decided to change the battery as a precaution but the fault still persists.

The only other thing I've seen online is to try replacing the Auxiliary Battery (capacitor), however im not sure if i should spend another £160 on something that potentially wont fix the issue. Cant seem to find anyone else that has had similar issues.

Any advice would be appreciated, thank you.

 

Perhaps a problem with residual fuel pressure? Left overnight, the pressure bleeds down and causes the stumble on the first start of the day. Once the engine has run, the fuel pressure is good, and subsequent starts are problem-free. I would check the fuel pressure after the vehicle has been sitting for a prolonged period and compare this with the pressure after the engine has been running.

 

Thank you for the reply Alynch

Do you know how I would go about doing this?

I can see fuel pressure using the Carly scanner, however to get this working I have to turn the ignition on and when I do it then runs the fuel pump. Which in turn causes the car to start fine and the first fuel pressure I can see is at the correct standing pressure.

for the pressure to be leaking back, would I expect to see a small amount of fuel somewhere under the car? Or could it be the fuel pump?

Tia

 

With your foot off the brake pedal, press the start button once to turn on the power. This should allow you to use the Carly scanner to look at the fuel pressure. If you press the start button twice, this turns on the ignition including the fuel pump. It would be better to connect gauges to the fuel pressure rail in the engine compartment. You could look for leaks in the engine compartment and underneath the vehicle, but especially with diesel, there would be a strong smell outside the car if there is a leak. It could be the fuel pump, although the vehicle runs properly the majority of the time. It could also be a leaky injector.

 

I’ll give this a go in the morning and see what pressures I’m getting. Thanks.

There has been no smell of diesel so suspect it isn’t leaking out of the car.

I have had the injectors tested and I am told they are ok. They also checked compression and signs of leaks from anywhere on the vehicle.

I’ll update tomorrow with the findings of fuel pressure.

 

Checked the fuel pressure last night using the Carly scanner and it showed a pressure of 0.9 bar. Started the car and found the pressure jumped to 4.5 bar. Once the engine was off, the pressure fell back to 0.9 bar.

Got to the car this morning and the fuel pressure still read 0.9 bar.

However, the car did not misfire on startup but did take longer than usual, sounding as if it was starved of fuel.

im going to check the fuel lines near the fuel filter housing for any signs of leaking, and also replace the clips holding the lines onto the filter filter to see if this makes a difference.