Vanos Rebuild Start Hesitation

[sapote]

“I had kind of thought that my OBDLink MX+ dongle that I leave plugged in all the time would be causing the battery drain, but it is supposed to go to sleep after a short period of no connectivity. Also kind of confused why I didn't see a drop in draw when pulling fuses when I should have pulled the fused for the OBD port somewhere along the line.”
Remove the dongle and see if drainage lower.

[jamesfoley]

The battery voltage is still low, but I'm not sure its the cause as it did still start on 11.7v without any hesitation at all this morning on a stone cold engine. A 20 minute drive bought the battery up to 12.7v and coming back to the car 10 or so minutes later it had come down to 12.2v which I'm assuming is it loosing some form of surface charge, but it hesitated to start this time.

11.7v engine off, 8.6v cranking, between 13.9v and 14.1v idle and driving, cold engine, perfect start
12.2v engine off, 9.2v cranking, warm engine, hesitated to start.

Pattern does look like its warm engine related, but sometimes its the other way around, hesitates when cold and perfect when warm.

Unsure if voltage fluctuations are causing something to be upset, like an injector or a coil, but would have thought they'd be classed as misfires and would increase the misfire counter, which it doesn't.

I had kind of thought that my OBDLink MX+ dongle that I leave plugged in all the time would be causing the battery drain, but it is supposed to go to sleep after a short period of no connectivity. Also kind of confused why I didn't see a drop in draw when pulling fuses when I should have pulled the fused for the OBD port somewhere along the line.

[jamesfoley]

You are stalking about a start hesitation. During crank and for a small time initially it's essentially all battery though which is your problem isn't it?

Kind of, the car has a healthy first and partially second rotation, then as it catches it sort of stumbles into life. Doesn’t do it every time.

Battery obviously has enough cranking amps to turn the car over fine, but wondering if the low voltage as the engine starts is upsetting something.

You really pulled every single fuse?

Yea. Initially I was going through some common known systems like the radio, air conditioning, and central locking, but after seeing none of those made a difference I just pulled each fuse one by one and checked the current draw each time.

No idea how I managed to set the alarm off doing that though.

I’ll check the voltages at each fuse today to see if I can spot anything.

[Shonky]

Yeah spec is <40mA. Typical is more like 20mA. I'd definitely be looking into that.

You are stalking about a start hesitation. During crank and for a small time initially it's essentially all battery though which is your problem isn't it? What happened with starting after leaving battery on charge over night i.e. fully charged and ready to go?

There are very few things that are unfused at least at some level. You really pulled every single fuse? The only things not going through a fuse is starter and alternator.

Note, you can measure voltage across the fuse to look where curernt is going. Down at that 50-100mA level it's quite small voltages but measurable and sometimes more helpful than pulling fuses since that can wake up a lot of things.

[sapote]

Parasitic draw test didn't seem to clear much up, after waiting the 16 minutes for everything to sleep I was still seeing 50mA, with it occasionally jumping to 90mA. Apparently this should be around 40mA or less to be "normal".

Pulled every fuse individually and none of them made a difference to the draw on the battery. Occasionally it'd drop to 10mA but returns to 50mA or 90mA.

Only thing I managed to achieve was setting my alarm off which was nice.

Battery was testing at 11.7v but cranked and started the car fine other than the slight hesitation before catching.

I start to think the low batt affects the hesitation.

50 to 90ma is higher than normal sleeep current.

[jamesfoley]

Parasitic draw test didn't seem to clear much up, after waiting the 16 minutes for everything to sleep I was still seeing 50mA, with it occasionally jumping to 90mA. Apparently this should be around 40mA or less to be "normal".

Pulled every fuse individually and none of them made a difference to the draw on the battery. Occasionally it'd drop to 10mA but returns to 50mA or 90mA.

Only thing I managed to achieve was setting my alarm off which was nice.

Battery was testing at 11.7v but cranked and started the car fine other than the slight hesitation before catching.

[jamesfoley]

Sat 2 days and down to 12v is kind of low, even at 14C.

Charge the batt overnight set at 5A or higher. Crank next day to see it's better. Drive 5 miles or more, park overnight and measure batt posts next day.

Hmm I see your point, 12v is pretty flat. Though with 14v+ when running it should be charging, right?

I've never had the car not start because it's been too flat, or had any lights on the dash to suggest low voltage, but I'm assuming thats because when its running its seeing the 14v+ it needs.

Other than an issue with the battery itself. would there be any other reasons why the battery isn't accepting a full charge?

I have another multimeter I'll try also just to rule out the multimeter being wrong.

Edit: Just to add to the confusion, battery is at 11.8v this morning after another day of sitting. Obviously have a parasitic draw somewhere...

[sapote]

Sat 2 days and down to 12v is kind of low, even at 14C.

Charge the batt overnight set at 5A or higher. Crank next day to see it's better. Drive 5 miles or more, park overnight and measure batt posts next day.

[jamesfoley]

`12.02v is low for a battery. What was the ambient temperature and when it was last driven and how far?

14.01 and 14.03v shows that the big cables have good connection.

Battery is a 6 month old Bosch S5 which I fitted as part of troubleshooting this issue. The battery it replaced was also a Bosch S5 and there wasn't a change in behaviour when I fitted the new one.

Car was sat for two days before I took those readings, averaging around 14°C ambient at a guess. I can drive the car for 2 hours, turn the car off and then try and start it again and it would still hesitate. But it will also happen first thing in the morning sometimes after being sat overnight. It's completely random.

[sapote]

12.02v across battery terminals.
12.00v from positive jump post to block.

14.01v across battery terminals with engine running.
14.30v from positive jump post to block with engine running.

No accessories running.

`12.02v is low for a battery. What was the ambient temperature and when it was last driven and how far?

14.01 and 14.03v shows that the big cables have good connection.

[jamesfoley]

Yes

12.02v across battery terminals.
12.00v from positive jump post to block.

14.01v across battery terminals with engine running.
14.30v from positive jump post to block with engine running.

No accessories running.

[sapote]

Yes

[jamesfoley]

Maybe the starter is weak due to cable resistance or weak batt.
Do this: first thing in early morning, measure batt voltage with engine off. Then run car at idle, measure voltage at batt posts directly (not on cable clamps), then measure from the fender jump post to engine body and see the difference.

I'm 95% sure the starter is okay, the car has never had an issue cranking, even way back when I had long cranking issues.

Can certainly check voltages though, battery neg to battery pos, and then jump post pos to engine block right? Both with engine off and then engine running?

[sapote]

Intermittent start hesitation is my main issue really. Sometimes it doesn’t just crank and fire, it sort of stumbles into life. 60% of the time it starts normally, and there are a handful of times where it feels like it starts too fast with barely any engine rotation before it fires up.

Maybe the starter is weak due to cable resistance or weak batt.
Do this: first thing in early morning, measure batt voltage with engine off. Then run car at idle, measure voltage at batt posts directly (not on cable clamps), then measure from the fender jump post to engine body and see the difference.

[jamesfoley]

Is your main concern about the status 8, or other problems? Mine also has fuel status 8 ocationally but I think my engine is normal.

Intermittent start hesitation is my main issue really. Sometimes it doesn’t just crank and fire, it sort of stumbles into life. 60% of the time it starts normally, and there are a handful of times where it feels like it starts too fast with barely any engine rotation before it fires up.