2011 Vauxhall Zafira A18XER with approx 15000 miles. Been to another dealer but they couldnt 'fault' the car. I looked at this monday morning and it would struggle to start, crank over for about 5 seconds before spluttering into life. Turned off and restarted better but still not 100%.
Diaganostic check with no DTC's stored, checked fuel trims, fuel pump relay,tank vent valve,coolant temp sensor on live data, all looked in spec.
Carried out a battery test which passed ok. Carried out a compression check on the engine from cold (pushed into the workshop and not started) which returned 175psi on all 4 cylinders.
I suspected fuel pressure as once it started it would stumble and would idle rough for a few seconds before evening out.
Fuel pressure test. KOEO the gauge would flick to 2.1 bar then fall to zero. When cranking the pressure would slowly rise to around 2.8 bar with the engine spluttering into life around the 2 bar mark. At this point i hooked up the scope and used the amp clamp to monitor the fuel pump..
I'm no expert but the waveform didnt look right at all. The fuel system is a non return type with the pressure reg living in the swirl pot. I know from experience and confirmed with another vehicle that the fuel pressure should be 3.8-4bar KOEO and KOER.
Could somone explain whats going on with the waveform, i suspected the the pressure reg was sticking/faulty dumping the pressure with the fuel pump working harder to retain the correct pressure?
I removed the tank and swirl pot with nothing obvious to the eye, replaced the full swirl pot in which lived the pump and regulator as seperate parts werent available.
Rebuilt and retested first with the gauge. 4 bar KOEO and KOER. started the engine and it ran fine and started like it should. Hooked the amp clamp back up...
compared both the original and new
The new pump/pressure reg certainly has a smoother waveform.
What do you guys think?