Crank no start...but then does...

[Ninj43]

ey up all

Bit of a weird one, 2017 CXEB (had a new engine 15k ago) couple of hour eventless drive today but got a crank no start after being sat for 5 mins. No EML. Left it for another 5 mins, still nothing.

Plugged it in to a diagnostic tool, suspecting timing belt. No related codes, but tried it again while connected and fired up instantly. Sat all day and started normally again. Drove 2 hours home and got same issue; after being turned off, back to the crank no start. Refused to start for about 15 mins, plugged it in again, although this time did clear DTCs, (only historic infotainment fault there) fired up again.

Diagnostic tool unplugged still good and starting normally.

So, definitely seems having it in diagnostic mode gets round the issue - is there anything different/inhibited whilst in diag mode?

• Battery is pretty new and seems to be having no problem cranking (will do a proper test tomorrow)
• I thought maybe a weak lift pump but surely that would struggle to start and not just suddenly work?
• Loose fuse/lift pump relay?

Whats a useful test in VCDS? Maybe one to check injectors are being commanded during crank? Still seems weird that its reset something by connecting to a diagnostic tool but maybe that makes sense to someone?
Cant see anything being mechanically wrong would allow it to not only start and run normally but drive fine for a couple of hours without a light on the dash.

Thanks in advance, my brain hurts

 

[Dellmassive]

They are some excellent tests that @mmi had detailed ..

Hpfp is a good one to start with. (Fuel to injectors)

.

Post in thread 'Start up fault'

11 Mar 2022

@mmi

start-up rail pressure build.

@850rmp Rail pressure @ 27700kPa

• Dellmassive

• 

 

[manfrotto]

Interesting- probably worth determining definitively if connecting the scanner makes a difference or not.
1 - Try starting it when hot and getting the crank no start issue, and then leave it for a lot longer so engine cools down and then try again
2 - connect the scanner straight after the crank no start issue and try starting without waiting.

I cannot think how connecting the scanner would "fix" the issue, but maybe @mmi has an opinion on this.

 

[Ninj43]

They are some excellent tests that @mmi had detailed ..

Hpfp is a good one to start with. (Fuel to injectors)

.

Post in thread 'Start up fault'

11 Mar 2022

@mmi

start-up rail pressure build.

@850rmp Rail pressure @ 27700kPa

• Dellmassive

• 

Thanks @Dellmassive haven't seen that thread so will have a good read. The trick is going to be catching the bugger in the act!

 

[Ninj43]

Interesting- probably worth determining definitively if connecting the scanner makes a difference or not.
1 - Try starting it when hot and getting the crank no start issue, and then leave it for a lot longer so engine cools down and then try again
2 - connect the scanner straight after the crank no start issue and try starting without waiting.

I cannot think how connecting the scanner would "fix" the issue, but maybe @mmi has an opinion on this.

Yep, good shout @manfrotto , we need to encourage the fault back and rule out heat. That was my first suspicion, I was thinking of a relay or something getting stuck when hot, or an air lock (released filler cap no hiss, no change).

Im of the same opinion; how can connecting to OBD possibly overcome the no start? 2 different tools aswell so kind of says it's just the action of going into diag mode and back that sorts it's logic.

Not only that but why would it continue to be OK for a so far undetermined time with it disconnected? ie it doesn't need to be connected to run immediately there after.

Time for a decent run today to encourage the fault back, and do some testing, thanks again all, I'll report back

 

[Cornish Boy]

May be worth trying another key as a quick and simple way to eliminate a key fob/immobiliser issue.

 

[Ninj43]

May be worth trying another key as a quick and simple way to eliminate a key fob/immobiliser issue.

Ah sorry, should have mentioned I did swap keys to rule out immob.
Went down the thought process that perhaps in diag mode the immob was somehow being bypassed but that's surely flawed as it wouldn't be much of an immobiliser if it was defeated by a scan tool

 

[Ninj43]

Heres some VCDS info - obviously logs are of a succesful start. I'm off out for a drive to try and get it to fault

 

[Ninj43]

So 40 min drive, uable to replicate the issue

 

[Dellmassive]

Keep vcds with you.....

Next time you get a crank no start, plus it in and start recording the data as per MMI test ..

Fuel rail pressure, rpm etc e to c

 

[Ninj43]

Yeh will do it's there ready....not got a lot of confidence to drive it far just now, just the nature of these transient faults though eh

I'm going to swap the fuel pump relay on spec as there's a few instances of this being the issue with no DTCs or dash lights

 

[Dellmassive]

Good call, the lift pump doesn't prime when the door opens.

Or starts when the engine is cranking...

Sticky relay, or iffy lift pump are possibilities.

 

[Ninj43]

Yep, I'm toying with putting a new lift pump on aswell when I imminently fit the diesel heater.

Seems to be one of the few faults that manages to present no EML or fault code

 

[DXX]

It would be simple to temporarily T into the lift pump line and fit a pressure gauge to monitor the fuel pressure.

 

[Dellmassive]

It would be simple to temporarily T into the lift pump line and fit a pressure gauge to monitor the fuel pressure.

You can get to the loom at the connection point under the passenger seat...

That's the rear loom.... Rear wheels, lights, PDC, etc. in fairly sure the fuel pump line is they too?

 

[JoshB_]

Was it a brand new crate engine? Just a block? Recon? Used engine?

If it was a petrol engine then I’d be going straight to the spark plugs… so check glow plugs maybe? But id expect a code as the circuit is pretty sensitive.

 

[Dellmassive]

Possibly one of the red connector wires?

Thread 'Ignition Live Under Passenger Seat - How Its Done -'

23 Mar 2019

Ignition Live Under Passenger Seat - How its done -



This question pops up fairly often so i thought i would look at it a bit closer. . . . .

If your van was factory fitted with the AUX battery under the seat, then your sorted. There is already a feed under there . . . . =]

BUT what if your van hasn't got the Factory option? . . . . Well there are two options for you.


Run (a new wire) the factory wire from the BCM under the dash/steering wheel

or

Run a (a new wire) from the ignition feed center-line of fuses in the under dash fuse panel...

• Dellmassive
• dellmassive fuse box sh how to guide ignition live solar
• Replies: 84
• Forum: Electrics, Lighting, ICE, Security

• 

 

[Dellmassive]

Looking at that scan data is a CXEB.

So a 2017 204 CXEB biturbo diesel.

 

[JDC]

Just an idea here. I had an issue similar to yours years ago on a Fiesta. It turned out it was a loose earth from the engine to the body. It would randomly fail to start either from cold or from hot. Luckily enough Fiesta engines are small and was easily found and cured by chance. It bugged me for weeks!!! If you've had a new engine there could be a wire somewhere thats worked loose??? Its an easy check.

 

[Ninj43]

Was it a brand new crate engine? Just a block? Recon? Used engine?

If it was a petrol engine then I’d be going straight to the spark plugs… so check glow plugs maybe? But id expect a code as the circuit is pretty sensitive.

Not sure, before my ownership I'm afraid.

I discounted a glow plug issue on the grounds it's not labouring to start....it just doesn't start at all and sounds different when cranking
I simulated a glow plug issue today, put the ignition on and leave it on then crank so the plugs have gone back off and the cylinders cooled down. It does labour for a couple of secs but fires as you'd expect.

When this problem is present it will turn over indefinitely and never sound like it's trying