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Cut out and now wont start


wiltsathome

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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??????

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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

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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

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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

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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.
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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.

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FuelPumpWiring.png.013238ed966bf564b7fab7970a9b80ad.png

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!

SumitomoPlug.png.c50c9b24eb8ecdc08f5058ae02882d43.pngMFRUPlugs.png.733ba8a5583b783fb4131759a2808796.png

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  • 4 weeks later...

Sorted the problem after much ferreting around with a multimeter and many cups of tea. Tracked it down to an inconsistent earth where the loom earths pick up on the ECU location bolt. Having cleaned it up and put a wire on the short run from here to the battery negative terminal directly it is fine. An inconsistent reading on the multimeter depending on electrical load was the only clue as it certainly wasn't completely dead. 

Many thanks to Ian, Revilla and Jonathon (and emailed wiring diagram) for their suggestions and help. Cheers Guys. 

Tony. 

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  • 2 weeks later...
  • 2 years later...

Hi Guys

I'm having same sort of problem as detailed above on a 1992 ECU2 1400 Supersport – and found this on archive (through google search in the end). Seem only to be getting around 8v's if anything at all to the fuel pump on volt meter (seems to vary sometimes nothing or under 1 volt and  sometimes up to 8v, although slowly climbs to this if at all) and pump will not prime – same on cranking the engine post priming phase.

Have tried fly wires (both live and earth) straight from battery and pump works fine (should do a new pump) - Reconnected the normal earth wire and leaving live fly wire and again works fine, so would appear to be the live side of circuit.

Battery is circa 12.85v before cranking and on normal ignition switch on 

On cranking drops to 8-9 volts

At FIA key:- 12.85V both sides so no drop there

MRFU - Input pins Pin 2 12.65V, Pin 1 – 0 at Pin 2 which I think is correct

MRFU - Output pins Pin 4 and pin 12.6V

Tried both a new MRFU unit (YWB 001022) and a spare and same results with both

At fuel inertia switch seems to be 12.4V on the brown and blue wire entering the inertia switch – Other wire is a white and purple, which seems to lead off into the loom.

At fuse box between nothing and 8v, with the volts slowly climbing during the usual priming stage and also on cranking the engine post priming stage

The problem I’m having is the “Grey” ecnoseal plug per the diagram attached above (I’ve been using) -  same as Reviila’s on the Technical Guides section (EU2 Non-VCC), but that doesn’t show the inertia switch

https://www.lotus7.club/sites/default/files/images/docs/guides/WiringDiagrams/WiringDiagramNonVVC.png

I’ve also looked at an older version by Shaun-E which includes the inertia switch

https://www.lotus7.club/sites/default/files/images/Docs/Guides/YSB104490%20Engine%20harness%20K-series%20EU2%20non%20VVC.pdf

Basically cobbling my thoughts together between the 2 

The sequence I am working to is - MRFU to Inertia Switch to main engine loom plug to fuse box to pump

The problem I have is locating the main loon plug C162 per Revilla’s diagram  – where is it – I have a fairly large black plus which seems to be coming off the loon at back of the engine (circa 1 feet away from the MRFU and EMU) which I assume iss it, but this only has circa 9 connector pins and on separation looks nothing like the C162 plug detailed in the revilla’s diagram, although does not look dissimilar to the main engine loom detailed in the 1992 handbook on separation (big black location plastic bit in the middle of plug. The purple and white wire seems to be coming in/out on pin 4 on the top row of wires on this plug

Unfortunately time ran out today, but assuming my understanding of the sequence in the wiring diagrams, and the 1992 wiring is not dissimilar , it would seem to me to date I’ve located the problem to be either

  • the main loom plug itself (on separating the plug, their did seem to be quite a lot of scorching on the yellow plastic on both sides on the inside of the plug around the pin 4 so that may be it and also all the wiring looks a bit mucky both sides of the plug), or
  • the wire from the inertia switch to the main loom plug
  • or the wire from the main loom plug to the fuse box.

Now the questions:-

  1. Is the sequence I using above the correct one
  2. Do you think I’m on the right track or is there anything else I need to consider/missed
  3. The main loom plug – given the convoluted wiring (I’m not brill on electrics and certainly some of the wire colours don’t seem to tally – may have had some rewiring in it’s life – certainly has the separate starter motor relay), I’m confused given the wiring to/from the main loom plug come in/out of the sheaved sections of loom which side of the main loom plug is coming from/going to where – the black main loom plug has male pins in the side of the smaller black outer and  fits into the female pins in the larger of the black outer shells – Wires sizes to me seem smaller on the former side Which side is from the inertia switch, which side to the fuse box (may help me track which side is the problem).
  4. My main concern is that sometimes I’m getting nothing and sometimes up to 8 volts – can’t help but think there is something I’m missing if its swinging around like this.
  5. Given the comments on the main loom plug (grimy and scorching inside), do you think I should just change the plug anyway (difficult to see what state the female pins are in anyway)

As ever guys, any help/advise much appreciated

Many thanks in advance

 

 

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Thanks EEK

Seems like the Ecnoseal plug on yours (mine has scorching too) - may try an locate a new plug (Redline maybe) and do a complete new refit of all connectors and clean up of all the wiring round it

I've also PM'd Karl H whose thread you kindly attached to see what in end his loss of voltage was down to - hopefully he's sorted his by now.

I'm also charging up the battery after checking acid levels (Jonathan advised the the voltage on cranking was low, although that wouldn't explain the pump not priming on ignition switch on) 

Still welcome any other ideas from others too in my quest to find a solution.

Next weekend's work

Bloody electrics !!!

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Toby S - just to reiterate, cleaning the contacts resolved the problem for me, if root of your problem is in this connector then I would expect a careful clean would, if only temporarily, resolve it so confirming likely problem source. 

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Hi Toby,

I'll try to answer as many of the questions as I can, and give you a few quick pointers. Sorry I didn't respond earlier, I've been a bit snowed under work-wise lately.

The various voltages you are measuring at the FIA key and the MFRU, FIA key etc. that are 12.5V+ ... are you measuring these whilst the fuel pump is trying to run (e.g. during the couple of seconds of priming after switching on)? The voltage drop across something will depend on its resistance but also on the current flowing, so you need to look for the voltage drops with the circuit under load. But having said that, the main supply connections and through the FIA switch are common to all the circuits and there will be some load from the ECU etc. so if there really is very close to zero drop there they should be OK. If you want to prove it with a load that last for more than two seconds, put your headlights on (but obviously that will only load up the main supply connections and nothing further down the fuel pump circuit!).

They grey plug you are looking for is here on my car:

IMG_20200428_133737.thumb.jpg.a50ed82b59d68f4a824bfcd9697da19e.jpg

Not where you would expect it, but the engine loom was based on a Metro loom and the engine got turned round through 90 degrees so what would have been on the driver's side bulkhead ended up at the front and everything now goes on an illogical detour to the front and back again. Here's a close-up.

IMG_20200428_133746.thumb.jpg.e312e1da92d09163876ce32102e8a981.jpg

It's a Sumitomo connector, not an Econoseal. There's a lock you need to squeeze on the side before you can pull it apart (and sometimes you need to squeeze the lock quite hard and pull the connectors apart very firmly as they can be tight).

I think you were looking at this behind the engine:

IMG_20200428_133755.thumb.jpg.80ac24dd6c3bbb6906fe4c72c6029cbb.jpg

That's between the engine loom and injector sub-loom and not relevant to this problem.

The inertia switch is usually part of the main vehicle loom rather than then the engine loom. There's a high-resolution, corrected, full colour, easy(er!) to read redrawing of the main vehicle loom on my own website here: http://andrewrevill.co.uk/Downloads/Wiring%20Diagram%20-%20Main%20Vehicle%20Loom%20-%20Corrected.png

The circuit for the fuel pump basically runs as follows (you can trace it through the two wiring diagrams). I've mentioned the standard wire colours but from what you've said, some of yours may be different:

Vehicle Loom:

  • Brown from Battery +ve to Fuse 14
  • Purple from Fuse 14 to Engine Loom Supply Spade Connector

Engine Loom:

  • Brown/Slate from Engine Loom Supply Spade Connector to MFRU Pin 8/6
  • Yellow/Green from MFRU Pin 8/4 to Grey Plug, Pin 9, Engine Loom Side

Vehicle Loom:

  • Yellow/Green from Grey Plug, Pin 9, Vehicle Loom Side to Fuse 13
  • Yellow/Green from Fuse 13 to Inertia Switch
  • Yellow/Green from Inertia Switch to Fuel Pump
  • Black from Fuel Pump to Earth Point

If jumping +12V into the pump gets it working fine, you could simply try working backwards jumping +12V at various points back up the circuit until it starts to misbehave. Working backwards from the pump until you get to the engine loom, the wire terminates at the N/O switch terminal of a relay inside the MFRU. When it's not priming or cranking, this will be effectively disconnected, so you won't do any harm jumping battery voltage into the circuit at any point. If you wanted to be really safe you could unplug the large plug on the MFRU while you test the downstream bits.

Start by unplugging the inertia switch and connecting +12V to the two end terminals. One of them should run the pump properly (the other one goes back to the MFRU, it won't drive the pump but it won't do any harm as described above). If that doesn't work properly there's a wiring fault between the inertia switch and the pump. If it does ...

Connect 12V onto Fuse 13. Try both sides of the fuse. If one side works and the other doesn't there's a problem with the fuse. They can become corroded and develop significant resistance even if they're not "blown". If both sides don't work the pump there's a wiring fault between Fuse 13 and the inertia switch.

... etc. Keep working back up through the grey plug into the engine loom until you are putting +12V into Pin 8/4 if the unplugged large plug on the MFRU. If that still works the pump correctly, the fault is either in the MFRU (which you've already swapped) or in the supply to it.

Anything upstream of the MFRU isn't going to run the pump when you put +12V on it as the relay in the MFRU will be turned off. You've therefore got two options for testing stuff further up:

  1. Look at the voltage at each point in the circuit WHEN IT'S TRYING TO RUN THE PUMP, looking at voltages when it's just sitting there will tell you nothing useful.
  2. Unplug the big MFRU connector and carefully bridge Pin 8/4 to Pin 8/6 with a short length of wire. Just be careful as that should end up connected to the battery +ve so you don't want it shorting to anything earthed. If you're careful yu can prise the white plastic "secondary lock" piece off the face of that plug which makes it easier to poke bits of wire in. Alternatively if you are handy with a crimper, crimp tow male spade terminals onto a piece of wire and plug them straight into the connector pins.

In theory, as soon as you bridge those two pins the pump should run. If it was running when you fed +12V into Pin 8/4 and doesn't run when you bridge those two, you've definitely go a problem between the battery and Pin 8/6. That circuit goes through a single spade connector on the bulkhead somewhere where a feed from the vehicle loom plugs in to feed the whole engine loom. It's a bit of a favourite for getting corroded, dirty or loose so well worth looking at closely.

Hope that helps.

Andrew

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Hi Andrew

Many thanks for you reply.

I think the one of the problems I seem to have is the wiring colours don't seem to match anywhere once you're past the fuel pump

  •  Fuel pump - yellow/green and black - tick
  •  Interia switch - brown/grey and white and purple - hmmm
  •  Fuse box - both purple and white - hmmm

Seems I have a car wired by a colour blind electrician !!

Re what I thought of as the main loom plug, on mine this sits on the main bulkhead/shelve (same bulkhead the ECU,and MRFUsit on) directly on top of the heater blanking plate under the the heater bypass hoses (I guess when the car had a heater it may have been dropped into engine bay). I may have got confused by the sight of white and purple wires in there (interestingly no green/yellow) and in the 1992 handbook wiring diagram it describes the wire going to fuel pump as purple/white

Re the plug you refer to at front on drivers side, there is no large grey plug but there is however a smaller black plug (circa 6 pins) which sits along side a thick sheaf of wires (I assume the engine loom) and a much smaller sheaf of wires. Now interestingly the smaller sheaf comes out of the sheaf which goes on to the black plug, by passes the plug and then returns back into the sheaf coming out of the other side of the black plug - I wonder if at sometime in its history the original plug was part replaced and the by pass put in on some of the wires (I can definitely feel a join connection under this smaller sheaf of wires). Certainly seems worth investigating 

The only other plug around there seems to be under the throttle body and all wires from that seem to be linking to the throttle body itself (I guess the stepper motor/throttle bodies) and I can't see that being linked

Excellent tip on connecting a fly wire at different points on the system by the way and seeing where I can pick up the other end, and certainly should help locate wires in the circuit. I think disconnecting the MRFU big plug (and the main leads off the battery as well I guess) and connecting the fly wire from battery to the pump and then going hunting will be the trick disconnecting at various points - definitely want to see what is under that smaller sheaf of wires referred to above - wouldn't surprise me if I find a colour change of wires !!.

Probably will be this weekend's work if dry, but I'll keep everyone posted - You never know Andrew, you might find yourself with a completely alternative wiring diagram for the fuel pump circuit !!

Thanks again for all you help guys

 

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P.S Andrew

Re voltages - I shared the following with Jonathan over a PM yesterday

Nothing on - 12.95v

Ignition on 12.95v

On crankng engine - initial drops to just under 10v for a moment and sits at 10.3 - 10.4 during continued cranking

Fuel pump doesn't prime before cranking

Back to 12.95 after cranking (ignition on only as not started)

We agreed that this is unlikely to be the main problem but will clean up all battery connections whilst I'm at it and recheck

 

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