Cut out and now wont start

27 posts / 0 new
Last post
wiltsathome
wiltsathome's picture
Offline
Last seen: 1 week 5 hours ago
Joined: 03/08/2016
Cut out and now wont start

Help and ideas please.

I have a 2006 Roadsport with 1.6 K. Last Sunday it cut out and wouldn't restart. An hour later it did restart and I then did 200 miles in the afternoon without a snag. It cut out initially about a mile into a drive just after id washed it. When it eventually restarted I assumed something had dried out!

However, I went to use it on Monday morning and it wouldn't start and still wont. Turns over fine but no attempt to fire.

I have checked the following:

Fuel pump doesn't prime at all when ignition is turned on.Hard wiring the pump proves it to be fine

Bypassing the Inertia switch makes no difference

Key fob battery changed in case alarm wasn't disarming

Obvious wiring plugs disconnected and re connected

Fuses checked

Any ideas please??????

Jonathan Kay
Jonathan Kay's picture
Online
Last seen: 14 sec ago
Joined: 17/04/2014

What's the battery voltage at rest and when attempting to start? 

Fuses checked

Has it ever blown the ECU fuse, and what value do you have in there?

When it eventually restarted I assumed something had dried out!

Is it all dry around the plugs?

Fuel pump doesn't prime at all when ignition is turned on.Hard wiring the pump proves it to be fine

More on that please... you can hear the pump when it's jump wired but not when it isn't? Does that jump wiring affect it firing?

...

But I think you're getting close to removing the plugs and having a look at them.

...

Do you have a wiring diagram?

Jonathan

Wrightpayne
Wrightpayne's picture
Offline
Last seen: 40 min 41 sec ago
Joined: 17/04/2014

On my car a crimped joint on the fuel pump wire within the loom in the engine bay failed. Fixed by classic carriage so dont know where it was exactly but I understand work backwards from the inertia switch into the loom.

Try wriggling loom it to see if you can get it to connect.

Ian

wiltsathome
wiltsathome's picture
Offline
Last seen: 1 week 5 hours ago
Joined: 03/08/2016

Thanks Johnathon,

Battery is fully charged and spins the engine over no problem

It has never blown an ECU fuse in my time with the car and that has seen 10.5k miles in 14 months, all faultless

I cant imagine there is any water around the plugs after a couple of hundred miles on Sunday after its wash. But I will check to eliminate that one

I didn't try starting it with the fuel pump hard wired, but wanted to hear that the pump worked OK an dwasnt the source of the isse. The test proved that it works, but isn't getting a priming signal

I don't have a wiring diagram, but feel the need creeping up on me!

 

Thanks for your thoughts and ideas

Wilt

wiltsathome
wiltsathome's picture
Offline
Last seen: 1 week 5 hours ago
Joined: 03/08/2016

Thanks Ian,

I have done a bit of wriggling anything that looks like a wire, more needed im sure!

 

Wilt

Jonathan Kay
Jonathan Kay's picture
Online
Last seen: 14 sec ago
Joined: 17/04/2014

I didn't try starting it with the fuel pump hard wired, but wanted to hear that the pump worked OK an dwasnt the source of the isse. The test proved that it works, but isn't getting a priming signal

Same thought as Ian: how about running those jump wires again and seeing if it then fires?

Battery is fully charged and spins the engine over no problem

It probably isn't the problem but I'd still want to see the voltage as you try to start. Some 7 electronics seem very sensitive to low voltage.

I don't have a wiring diagram, but feel the need creeping up on me!

:-)

Please send me a Private Mail with the year, model, engine and dash and your email address.

Jonathan

revilla
Offline
Last seen: 42 min 34 sec ago
Joined: 17/04/2014
ECU fuse would prevent the engine cranking as it is actually the fuse for the supply to the whole engine loom and MFRU ... so carries the starter solenoid current. I've seen two cars with intermittent cut out and starting issues with ECU earth problems. You're looking for either a single thick black wire or a bunch of black wires exiting the loom either close to the ECU (usually if it's a bunch of wires) or under the throttle body (usually if it's a single wire) which should be crimped into a ring terminal and bolted to the bulkhead. Make sure that the wires are secure in the terminal and that the terminal is securely bolted to a clean metal contact point to make a good earth. One car recently had it bolted to the plastic heater, another looked fine until the owner wiggled the wires and they fell out of the terminal.

SV VVC 170 - 170.4 bhp @ 7100 rpm - 142.4 ft.lb. @ 4900 rpm

Jonathan Kay
Jonathan Kay's picture
Online
Last seen: 14 sec ago
Joined: 17/04/2014

I've seen two cars with intermittent cut out and starting issues with ECU earth problems.

Could that stop the fuel pump from running normally?

Thanks

Jonathan

revilla
Offline
Last seen: 42 min 34 sec ago
Joined: 17/04/2014

Yes it could ...

Fuel pump is supplied from MFRU output plug Pin 4. This has 12V switched to it by a relay in the MFRU from output plug Pin 1. The relay coil is connected to input plug Pin 2, which is connected to 12V when the ignition key switch is turned on, and input plug Pin 1, which is pulled to ground by the ECU when it wants to run the fuel pump.

If the ECU ground connection is bad, the ECU won't be able to pull anything to ground ... in fact it probably won't be doing much at all.

Do you get any "chatter" from the IACV (Idle Air Control Valve, cylindrical valve bolted to the side of the plenum chamber just in front of the throttle body, which normally makes a characteristic ticking or chattering sound just after switching on or off)? If not, it's further evidence that the ECU isn't up and running.

SV VVC 170 - 170.4 bhp @ 7100 rpm - 142.4 ft.lb. @ 4900 rpm

revilla
Offline
Last seen: 42 min 34 sec ago
Joined: 17/04/2014

Very crudely highlighted:

The yellow wiring is the current path from the spade connector that ultimately comes from the ECU fuse through the relay contacts inside the MFRU to the grey plug at the front end of the right hand engine bay rail, then it runs through the main vehicle loom from there via the inertia switch to the pump.

The green wiring is the current path from the ignition switched 12V white wire at the same grey plug as above, through the relay coil inside the MFRU to earth via the drivers in the ECU.

The immobiliser won't stop the fuel pump priming; in fact it will normally even let it run for a couple fo seconds before killing the engine; this is becuase the handshake between the immobiliser and ECU is very slow, so it allows the engine to start if the driver just jumps in and turns the key right round and allows a couple of seconds to get clearance from the immobiliser.

Do you have a multimeter? If no, prepare to be in trouble with Jonathan. If yes, you can probe those pins on the MFRU (hint: without disconnecting the the plugs, it's quite easy to slip a long pin or a needle down the side of the rubber seal around each wire to make contact with the terminal behind it). The pins are drawn on that wiring diagram looking from the the wiring side, so exactly as you see the MFRU looking at it from the front.

Let us know if you want to know exactly what to test. We can walk you though it step at a time.

Edited to add detail on those plugs as the website as usual has mangled the resolution of the image I posted!

SV VVC 170 - 170.4 bhp @ 7100 rpm - 142.4 ft.lb. @ 4900 rpm

Wrightpayne
Wrightpayne's picture
Offline
Last seen: 40 min 41 sec ago
Joined: 17/04/2014

Its more chunky part of the loom thats in a plastic fluted sleeve.

Ian