Vauxhall Zafira 2011 poor starting

Ask for and share advice on using the PicoScope kit to fix vehicles here.

Vauxhall Zafira 2011 poor starting

Postby GRUSS » Thu Mar 29, 2012 7:03 pm

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...
ZAFIRA a18xer NEW PUMP.psdata
(304.35 KiB) Downloaded 254 times


compared both the original and new
Zafira A18XER new fuel pump BLUE vs Old GREEN.psdata
(632.15 KiB) Downloaded 286 times


The new pump/pressure reg certainly has a smoother waveform.

What do you guys think? :D
GRUSS
Guru
Guru
 
Posts: 119
Joined: Tue Dec 27, 2011 11:16 pm

Re: Vauxhall Zafira 2011 poor starting

Postby Liteace » Thu Mar 29, 2012 8:55 pm

Dont know Mate, Ive just looked at the waveform and belive me I am no expert, Ive not even put the batteries in me Pico current clamps yet.

EDITED, didnt want to look more of a Div than what I already am !!!!!!!!!!


I would have thought if the old pump was working harder to deliver the fuel it would have be using more amps. As I say Im no expert and I hope someone will help us both out

Thanks
Last edited by Liteace on Mon Apr 02, 2012 11:54 pm, edited 3 times in total.
DONT SHOOT YOURSELF IN THE FOOT
Liteace
Guru
Guru
 
Posts: 152
Joined: Fri Jan 27, 2012 12:25 pm

Re: Vauxhall Zafira 2011 poor starting

Postby Kev » Mon Apr 02, 2012 11:16 pm

Hi Gruss,
Thanks for uploading the ps data files, it's a great way to share info and to help in resolving problems. First of all I would like to point out that the new pump was demanding greater current draw which is what I expected to see. If you go back to your original pressure tests you stated that you got 2.1 bar KOEO but it quickly dropped away, other than having a major leak in the line somewhere which was unlikely on a 2011 Model year car (but not impossible), it was most likely that this pump was returning too much fuel inside the tank, thus the pressure drop, and most importantly the low fuel pressure readings. You will notice that the new pump is in fact working 'harder' because it's not dumping excess fuel in the tank, that's the reason that you got the lower amperage readings on the bad pump. If the fault is mechanical and dumps excess fuel, then the demand from the fuel pump is less, this can be seen in your readings, for example average dc (Amps) for bad pump was 4.372 Amps, the average current draw for the new pump was 4.913 Amps. The new pump is working harder because it is now 'maintaining pressure' at a value of approx 4 bar. the less effort on the pump the less Amps, the more effort on the pump the greater the Amps. Hope this helps you and anyone else testing

Kev
Last edited by Kev on Tue Apr 03, 2012 12:11 am, edited 2 times in total.
Kev
User
User
 
Posts: 36
Joined: Sun Mar 11, 2012 7:23 pm

Re: Vauxhall Zafira 2011 poor starting

Postby Liteace » Mon Apr 02, 2012 11:21 pm

Thanks for pionting that out Kev, it's pretty obvious when we think about it, Ive should have know that, for for example when the end fall off the pressure washer I can hear the pump change tone because it not working so hard, I so wish I wasnt so much of a Div

Thanks Again
DONT SHOOT YOURSELF IN THE FOOT
Liteace
Guru
Guru
 
Posts: 152
Joined: Fri Jan 27, 2012 12:25 pm

Re: Vauxhall Zafira 2011 poor starting

Postby Kev » Mon Apr 02, 2012 11:33 pm

It's not a problem Liteace, that's what it's all about! Nobody is infallible!

Kev
Kev
User
User
 
Posts: 36
Joined: Sun Mar 11, 2012 7:23 pm

Re: Vauxhall Zafira 2011 poor starting

Postby Robski » Tue Apr 03, 2012 10:04 am

Did no-one measure the pump speed as well as current draw ?

Flow test ?

Dead head ?
User avatar
Robski
Advanced User
Advanced User
 
Posts: 602
Joined: Tue Sep 14, 2010 6:36 pm
Location: Yorkshire

Re: Vauxhall Zafira 2011 poor starting

Postby Liteace » Tue Apr 03, 2012 6:42 pm

Robski wrote:Did no-one measure the pump speed as well as current draw ?

Flow test ?

Dead head ?



No because we \ I cant think of things like that, its only when we \ I ask then I think "OH Yer" why didnt I check that, I think in about 5-6 years my brain would have absorbed the info its needs :oops:

Thanks
DONT SHOOT YOURSELF IN THE FOOT
Liteace
Guru
Guru
 
Posts: 152
Joined: Fri Jan 27, 2012 12:25 pm

Re: Vauxhall Zafira 2011 poor starting

Postby GRUSS » Wed Apr 04, 2012 5:18 pm

Kev,
Thanks for the explanation :D

So just to confirm... The messy waveform is due to the fuel pump or fuel pressure regulator dumping the pressure which is creating the erratic waveform. I pretty much knew I had a issue with the pressure readings but was nice to look the current draw of the pump with the scope.

Also scoped a few corsa's and their waveform was nice and steady. The pressure reg is on the fuel rail.
GRUSS
Guru
Guru
 
Posts: 119
Joined: Tue Dec 27, 2011 11:16 pm

Re: Vauxhall Zafira 2011 poor starting

Postby Kev » Wed Apr 04, 2012 10:15 pm

Hi Gruss,
Your welcome, and 'thank you' for posting originally. The waveform was slightly erratic on the bad pump which was almost certainly a result of pressure differences as the pump dumped the fuel then tried to build back up again. But I think what was more important than that was the average current draw, from both the old pump, and from the new one. That really is valuable diagnostic information, I'm just glad you posted it! That now sets a bench mark for that particular car/pump.

Thanks again Gruss Kev
Kev
User
User
 
Posts: 36
Joined: Sun Mar 11, 2012 7:23 pm

Re: Vauxhall Zafira 2011 poor starting

Postby GRUSS » Thu Apr 05, 2012 7:33 pm

No worries kev!
If I had more time I would upload loads of vauxhall waveforms but it's hard in a main dealer :cry: The only time I get is when I have a problem job, but that's when I need to compare to a known good one.
GRUSS
Guru
Guru
 
Posts: 119
Joined: Tue Dec 27, 2011 11:16 pm


Return to Diagnostic discussion

Who is online

Users browsing this forum: No registered users and 0 guests