Not joined yet? Register for free and enjoy features such as alerts, private messaging and viewing latest posts and topics.
Diagnosing long crank on cold start N52 engine
-
- Senior Member
- Posts: 1103
- Joined: Sat Aug 08, 2009 5:33 am
- Location: QLD, Australia
- Contact:
Diagnosing long crank on cold start N52 engine
Hi all,
My 3.0si has been getting progressively worse on cold starts (first thing in the morning or leaving work in the afternoon). It one day started the behaviour of cranking for an extended period (say 4 seconds), spluttering and then stalling. On second crank it would fire immediately. If I crank for just 2 seconds (so it doesn't fire), stop and then try again it fires immediately. Again, this is only on cold starts.
So it's obviously a problem with the fuel system not retaining pressure when the engine is off. I picked up a fuel pressure tester and did some investigation. The troubleshooting guide in the TIS is for a fuel return style system (not the returnless system used in Zeds) but indicates that the fuel pressure should not drop by more than 0.5bar in 30 minutes. I did this test and it seemed to drop by exactly that amount, which I'm pretty certain indicates an issue. Left overnight the fuel pressure dropped to 2 bar (from the initial 4.5bar the engine operates at).
So there are two potential causes of this problem: the fuel pressure regulator and the fuel pump nonreturn valve. The problem is that I don't think there's any way to determine which one is the cause! Such a problem would likely be caused by gunk stopping the regulator or nonreturn valve from sealing closed. As a diagnostic I did think I could simply remove the pressure regulator and attempt to clean it out. It just sucks that accessing the fuel system components (inside the fuel tank) is such a headache!
Does anybody have wisdom to impart on this topic?
Edit:
The plot has thickened, so here's a new overview of the symptoms. I'm starting to think this is not a fuel pumping/regulation issue but perhaps electronic.
- On cold starts (before and after work) the car won't start on first crank. Starts immediately on second crank.
- If cranked for long enough the first time the engine will fire and then immediately stall. The sound it makes at stall is the kind of sound you get when fuel is cut off.
- Fuel pressure test shows everything to be perfect at 4.5bar, even during cranking. Fuel pressure does bleed off over time when the engine is off but the pumps primes when ignition is switched off and immediately comes up to pressure.
- Waiting a few seconds with the key in position 2 makes no difference.
- No fault codes in the DME. Will check for any other modules like the EWS tonight.
My 3.0si has been getting progressively worse on cold starts (first thing in the morning or leaving work in the afternoon). It one day started the behaviour of cranking for an extended period (say 4 seconds), spluttering and then stalling. On second crank it would fire immediately. If I crank for just 2 seconds (so it doesn't fire), stop and then try again it fires immediately. Again, this is only on cold starts.
So it's obviously a problem with the fuel system not retaining pressure when the engine is off. I picked up a fuel pressure tester and did some investigation. The troubleshooting guide in the TIS is for a fuel return style system (not the returnless system used in Zeds) but indicates that the fuel pressure should not drop by more than 0.5bar in 30 minutes. I did this test and it seemed to drop by exactly that amount, which I'm pretty certain indicates an issue. Left overnight the fuel pressure dropped to 2 bar (from the initial 4.5bar the engine operates at).
So there are two potential causes of this problem: the fuel pressure regulator and the fuel pump nonreturn valve. The problem is that I don't think there's any way to determine which one is the cause! Such a problem would likely be caused by gunk stopping the regulator or nonreturn valve from sealing closed. As a diagnostic I did think I could simply remove the pressure regulator and attempt to clean it out. It just sucks that accessing the fuel system components (inside the fuel tank) is such a headache!
Does anybody have wisdom to impart on this topic?
Edit:
The plot has thickened, so here's a new overview of the symptoms. I'm starting to think this is not a fuel pumping/regulation issue but perhaps electronic.
- On cold starts (before and after work) the car won't start on first crank. Starts immediately on second crank.
- If cranked for long enough the first time the engine will fire and then immediately stall. The sound it makes at stall is the kind of sound you get when fuel is cut off.
- Fuel pressure test shows everything to be perfect at 4.5bar, even during cranking. Fuel pressure does bleed off over time when the engine is off but the pumps primes when ignition is switched off and immediately comes up to pressure.
- Waiting a few seconds with the key in position 2 makes no difference.
- No fault codes in the DME. Will check for any other modules like the EWS tonight.
Last edited by Mangozac on Sun Jan 24, 2016 11:37 pm, edited 2 times in total.
Current: 06 E85 M Silbergrau
Previous: E85 3.0si Silbergrau, 03 E85 2.5i Maldives Blue.
Mods: Gaptech OTH+R, Dension Gateway 300 with USB, CDV-, clear side indicators, euro tails, stubby, MFSW retrofit, OEM Bluetooth/VR
Previous: E85 3.0si Silbergrau, 03 E85 2.5i Maldives Blue.
Mods: Gaptech OTH+R, Dension Gateway 300 with USB, CDV-, clear side indicators, euro tails, stubby, MFSW retrofit, OEM Bluetooth/VR
-
- Lifer
- Posts: 5277
- Joined: Wed Feb 19, 2014 3:01 pm
- Location: NW London
Re: Diagnosing fuel pump or fuel pressure regulator fault on N52 engine
When you start how long do you leave the key in pos2 before starting?
3.0si Sport: F10 Illuminated ZHP, Retrofit Cruise, OE Stubby, Gaptech RCH+, Kenwood BT73DAB + Handsfree, HIDs, LED Sidelights, OE LED Number Plate Lights, Custom LED strip bootlight.
-
- Senior Member
- Posts: 1103
- Joined: Sat Aug 08, 2009 5:33 am
- Location: QLD, Australia
- Contact:
Re: Diagnosing fuel pump or fuel pressure regulator fault on N52 engine
Not for any deliberate/appreciable amount of time.
Current: 06 E85 M Silbergrau
Previous: E85 3.0si Silbergrau, 03 E85 2.5i Maldives Blue.
Mods: Gaptech OTH+R, Dension Gateway 300 with USB, CDV-, clear side indicators, euro tails, stubby, MFSW retrofit, OEM Bluetooth/VR
Previous: E85 3.0si Silbergrau, 03 E85 2.5i Maldives Blue.
Mods: Gaptech OTH+R, Dension Gateway 300 with USB, CDV-, clear side indicators, euro tails, stubby, MFSW retrofit, OEM Bluetooth/VR
-
- Lifer
- Posts: 5277
- Joined: Wed Feb 19, 2014 3:01 pm
- Location: NW London
Re: Diagnosing fuel pump or fuel pressure regulator fault on N52 engine
Try leaving in pos2 until all the lights go out - might help. I'm not up to speed on the fuel system but assume that as the ign comes on fuel is primed. Worth a shot to see if it helps.
3.0si Sport: F10 Illuminated ZHP, Retrofit Cruise, OE Stubby, Gaptech RCH+, Kenwood BT73DAB + Handsfree, HIDs, LED Sidelights, OE LED Number Plate Lights, Custom LED strip bootlight.
-
- Senior Member
- Posts: 1103
- Joined: Sat Aug 08, 2009 5:33 am
- Location: QLD, Australia
- Contact:
Re: Diagnosing fuel pump or fuel pressure regulator fault on N52 engine
I connected the pressure tester again to check the priming. It's definitely priming correctly - as soon as the key goes to position 2 the fuel pressure immediately comes up to spec.
The really frustrating thing here is that I'm unable to duplicate the fault when I have the fuel pressure tester connected. Even if I use the tester to completely drain the fuel line during priming the fuel line comes back to operating pressure and the car starts immediately. This is starting to make me wonder if maybe I'm barking up the wrong tree. The fuel pressure leakdown test from the TIS mentioned a pressure drop of more that 0.5bar and my pressure drop was almost exactly that, so maybe it is actually in spec? It's possible that the 0.5bar test value isn't even valid for the returnless fuel system design. I was going to clamp off the fuel supply line to check for injector leaking but it that line seems pretty rigid so I'm not certain that it's safe to clamp...
Any other ideas?
The really frustrating thing here is that I'm unable to duplicate the fault when I have the fuel pressure tester connected. Even if I use the tester to completely drain the fuel line during priming the fuel line comes back to operating pressure and the car starts immediately. This is starting to make me wonder if maybe I'm barking up the wrong tree. The fuel pressure leakdown test from the TIS mentioned a pressure drop of more that 0.5bar and my pressure drop was almost exactly that, so maybe it is actually in spec? It's possible that the 0.5bar test value isn't even valid for the returnless fuel system design. I was going to clamp off the fuel supply line to check for injector leaking but it that line seems pretty rigid so I'm not certain that it's safe to clamp...
Any other ideas?
Current: 06 E85 M Silbergrau
Previous: E85 3.0si Silbergrau, 03 E85 2.5i Maldives Blue.
Mods: Gaptech OTH+R, Dension Gateway 300 with USB, CDV-, clear side indicators, euro tails, stubby, MFSW retrofit, OEM Bluetooth/VR
Previous: E85 3.0si Silbergrau, 03 E85 2.5i Maldives Blue.
Mods: Gaptech OTH+R, Dension Gateway 300 with USB, CDV-, clear side indicators, euro tails, stubby, MFSW retrofit, OEM Bluetooth/VR
-
- Senior Member
- Posts: 1031
- Joined: Fri Feb 15, 2008 6:03 pm
- Location: UK
Re: Diagnosing fuel pump or fuel pressure regulator fault on N52 engine
Have you had the codes read?
Z4MC Imola red
- Smartbear
- Lifer
- Posts: 13685
- Joined: Wed Feb 05, 2014 6:54 pm
- Location: a barn in Somerset
Re: Diagnosing fuel pump or fuel pressure regulator fault on N52 engine
The symptoms sound as though they could be ignition related, have you plugged the car into a scanner?
Crankshaft position sensor could make the car splutter & cut out for example.
Regards
Crankshaft position sensor could make the car splutter & cut out for example.
Regards
e89 Sdrive 20i, plenty of mumbo & good economy-the thinking bears z4
e89 Sdrive 30i, this ones busted, pass me another...
e85 3.0si sold
-
- Senior Member
- Posts: 1103
- Joined: Sat Aug 08, 2009 5:33 am
- Location: QLD, Australia
- Contact:
Re: Diagnosing fuel pump or fuel pressure regulator fault on N52 engine
I should have mentioned that in the first post. Yep reading codes was the first thing I did, using INPA. Nothing at all flagged by the engine ECU. Everything looked fine.
Current: 06 E85 M Silbergrau
Previous: E85 3.0si Silbergrau, 03 E85 2.5i Maldives Blue.
Mods: Gaptech OTH+R, Dension Gateway 300 with USB, CDV-, clear side indicators, euro tails, stubby, MFSW retrofit, OEM Bluetooth/VR
Previous: E85 3.0si Silbergrau, 03 E85 2.5i Maldives Blue.
Mods: Gaptech OTH+R, Dension Gateway 300 with USB, CDV-, clear side indicators, euro tails, stubby, MFSW retrofit, OEM Bluetooth/VR
-
- Senior Member
- Posts: 1074
- Joined: Thu Aug 20, 2015 1:17 pm
Re: Diagnosing fuel pump or fuel pressure regulator fault on N52 engine
I am still a novice with these cars but I always start with the simple things first. Like what is the air filter like, are there any cracks in the plastic/rubber breathing system, when were the spark plugs changed, have you removed the plugs to see what condition they are in, are they soaked in petrol.
I am sure you will find it is something simple
I am sure you will find it is something simple
-
- Senior Member
- Posts: 1103
- Joined: Sat Aug 08, 2009 5:33 am
- Location: QLD, Australia
- Contact:
Re: Diagnosing fuel pump or fuel pressure regulator fault on N52 engine
Thanks Mike. I did check the spark plugs early on and didn't see any issues. Air filter is relatively new and I while craked intake components is definitely something to be aware of, I just can't see how that would be causing this issue...
Current: 06 E85 M Silbergrau
Previous: E85 3.0si Silbergrau, 03 E85 2.5i Maldives Blue.
Mods: Gaptech OTH+R, Dension Gateway 300 with USB, CDV-, clear side indicators, euro tails, stubby, MFSW retrofit, OEM Bluetooth/VR
Previous: E85 3.0si Silbergrau, 03 E85 2.5i Maldives Blue.
Mods: Gaptech OTH+R, Dension Gateway 300 with USB, CDV-, clear side indicators, euro tails, stubby, MFSW retrofit, OEM Bluetooth/VR
-
- Senior Member
- Posts: 1031
- Joined: Fri Feb 15, 2008 6:03 pm
- Location: UK
Re: Diagnosing fuel pump or fuel pressure regulator fault on N52 engine
Have a look at some threads where the ews unit was at fault.
I did have a case where the car would turn over but not start until I tried it for a second time. It did throw a code though and was slightly different from your problem, but could worth looking into?
I did have a case where the car would turn over but not start until I tried it for a second time. It did throw a code though and was slightly different from your problem, but could worth looking into?
Z4MC Imola red
-
- Senior Member
- Posts: 1103
- Joined: Sat Aug 08, 2009 5:33 am
- Location: QLD, Australia
- Contact:
Re: Diagnosing fuel pump or fuel pressure regulator fault on N52 engine
EWS is a good suggestion too, but I don't think it would the the problem here for 2 reasons:
1. No error codes reported
2. On the long cranks it will eventually fire and then immediately stall. My understanding is that the EWS will prevent any fuel supply.
I will tonight see about checking the EWS module for any errors (rather than just the DME) though, just to be thorough.
1. No error codes reported
2. On the long cranks it will eventually fire and then immediately stall. My understanding is that the EWS will prevent any fuel supply.
I will tonight see about checking the EWS module for any errors (rather than just the DME) though, just to be thorough.
Current: 06 E85 M Silbergrau
Previous: E85 3.0si Silbergrau, 03 E85 2.5i Maldives Blue.
Mods: Gaptech OTH+R, Dension Gateway 300 with USB, CDV-, clear side indicators, euro tails, stubby, MFSW retrofit, OEM Bluetooth/VR
Previous: E85 3.0si Silbergrau, 03 E85 2.5i Maldives Blue.
Mods: Gaptech OTH+R, Dension Gateway 300 with USB, CDV-, clear side indicators, euro tails, stubby, MFSW retrofit, OEM Bluetooth/VR
-
- Senior Member
- Posts: 1103
- Joined: Sat Aug 08, 2009 5:33 am
- Location: QLD, Australia
- Contact:
Re: Diagnosing long crank on cold start N52 engine
Update: I did a full error code read and nothing relevant came up (just some things in the airbag and radio modules). As per no_fit_state's advice it could theoretically be an issue with the ignition socket coil antenna but it would be a bit of a stretch. I might try reseating the coil antenna connector just to be certain.
Current: 06 E85 M Silbergrau
Previous: E85 3.0si Silbergrau, 03 E85 2.5i Maldives Blue.
Mods: Gaptech OTH+R, Dension Gateway 300 with USB, CDV-, clear side indicators, euro tails, stubby, MFSW retrofit, OEM Bluetooth/VR
Previous: E85 3.0si Silbergrau, 03 E85 2.5i Maldives Blue.
Mods: Gaptech OTH+R, Dension Gateway 300 with USB, CDV-, clear side indicators, euro tails, stubby, MFSW retrofit, OEM Bluetooth/VR
-
- Lifer
- Posts: 5277
- Joined: Wed Feb 19, 2014 3:01 pm
- Location: NW London
Re: Diagnosing long crank on cold start N52 engine
A real pickle, sorry I can't help and I hope you manage to figure it out.
3.0si Sport: F10 Illuminated ZHP, Retrofit Cruise, OE Stubby, Gaptech RCH+, Kenwood BT73DAB + Handsfree, HIDs, LED Sidelights, OE LED Number Plate Lights, Custom LED strip bootlight.
-
- Senior Member
- Posts: 1103
- Joined: Sat Aug 08, 2009 5:33 am
- Location: QLD, Australia
- Contact:
Re: Diagnosing long crank on cold start N52 engine
No worries, I appreciate the attemptScooba_Steve wrote:A real pickle, sorry I can't help and I hope you manage to figure it out.
Will keep you posted!
Current: 06 E85 M Silbergrau
Previous: E85 3.0si Silbergrau, 03 E85 2.5i Maldives Blue.
Mods: Gaptech OTH+R, Dension Gateway 300 with USB, CDV-, clear side indicators, euro tails, stubby, MFSW retrofit, OEM Bluetooth/VR
Previous: E85 3.0si Silbergrau, 03 E85 2.5i Maldives Blue.
Mods: Gaptech OTH+R, Dension Gateway 300 with USB, CDV-, clear side indicators, euro tails, stubby, MFSW retrofit, OEM Bluetooth/VR