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FIXED Crank no start, no spark

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7 years 4 months ago #3579 by jonathandean
Hi borntoroll, Thanks for your input, I really hope to get this problem sorted, I have checked the power and ground is there during cranking but only by back probing the coil connector, yes the cam and crank sensor signal both go to 0v, the problem seems to be there is no control over the coil and I have been unable to make the coil fire either by touching the control wire with a 12v test light, and bi directional control over the coils fail to make them fire, but the injectors do fire, doesn't that rule out an input problem to the PCM?

Remember the car drove into the garage before the engine work so it would be unlikely that all 4 coils have failed, is it likely the ecu is at fault?

Thanks for every ones help I really appreciate every bodies thoughts and ideas ;)

Jonathan

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7 years 4 months ago #3584 by borntoroll
Replied by borntoroll on topic Crank no start, no spark
So if you have power and ground you should be able to bypass the pcm with incandescent testlight and get a spark. Check the control wire for short to ground.

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7 years 4 months ago #3587 by jonathandean
Thanks, I have tried to do the bypass test but without success. I am on my own so I can't crank it and use a test light, I have tried to power the coil via a scan tool and then use the test light, one end bat + the other end on the control wire to the coil, but no spark. What is the best way to check the control wire for a short to ground?

Thanks again for your help, the electronic side of cars is not my strongest point, I learn't on a Morris Minor!

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7 years 4 months ago - 7 years 4 months ago #3588 by borntoroll
Replied by borntoroll on topic Crank no start, no spark
If the signal wire is shorted it will be close to 0 Ohms resistance to ground and the testlight should light connected between signal and positive terminal of the battery.
Last edit: 7 years 4 months ago by borntoroll.

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7 years 4 months ago #3589 by jonathandean
Thanks, It is late here now I will try that tomorrow.

Jonathan

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7 years 4 months ago #3590 by borntoroll
Replied by borntoroll on topic Crank no start, no spark
Also maybe one bad coil shuts down the whole system. Don't know the system design and if it is possible but try to disconnect all the coils and try to connect one at a time. Sounds crazy though.. i know... )

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7 years 4 months ago #3593 by jonathandean
Thanks, funny you should say that but one coil is obviously an aftermarket one, it is a very slightly different colour to the rest, but the car did drive into the garage before the engine work, I can assume the coils were working then, although it has sat for a while now. Thanks for your help, It is worth trying anything

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7 years 4 months ago #3597 by ImBack218
Replied by ImBack218 on topic Crank no start, no spark
You should have multiple coil control wires on that car. If you had a short to ground it sounds like all the control wires would be shorted, and I'm not sure that this is likely to happen. Do you have any fault codes? Can you do a current ramp test on the coils with your scope, and post back with the results? Use the amp probe around the power feed to the coils.

The other thing I'm worried about is you not having power to the coils with just the key on. This may be absolutely normal but I think it's worth noting?

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7 years 4 months ago #3620 by jonathandean
Hi Thanks for your reply to my post,

Yes there are multiple control wires, one shared power and one shared earth, an amp test on the positive lead reads 0 amps all the time, the coils don't fire, no current flow?

Cranking the engine gives 12v to all coils, this is a common system with european cars.

The injectors fire when cranking, does this show correct timing inputs are there?

The bi directional scanner controls don't make the coils fire and touching a positive fed test light to the control wire doesn't make them fire.

Every other Bi directional controls for the car work, ie the injectors fire when commanded,so i have correct communication

My understanding is the coil turns itself on by switching a path to ground to allow current flow through the windings, i have tried to use a test lead straight from coil negative to battery negative to see if a better earth helps, but no difference.

No fault codes stored.

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7 years 4 months ago - 7 years 4 months ago #3621 by ImBack218
Replied by ImBack218 on topic Crank no start, no spark
Yeah, 0 amps means your coils aren't being switched to ground and there is no current flow. Lack of bi directional control is suggesting a PCM problem or an output problem, but you are unable to manually create a spark with a test light. Does the test light bulb illuminate when you are touching any of the control wires? Can you do a voltage measurement of the control wires?
Last edit: 7 years 4 months ago by ImBack218.

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7 years 4 months ago #3622 by jonathandean
Thanks again for your help. No I can't make the coil fire, maybe I am doing something wrong but no the test light doesn't illuminate when I touch it to the comtrol. There is some very low voltage on the control wire,it was below half a volt and not constant, i measured it with a scope but the voltage level seemed negligible to me, a very small amount. I hope this info helps thanks Jonathan

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7 years 4 months ago - 7 years 4 months ago #3628 by borntoroll
Replied by borntoroll on topic Crank no start, no spark
Half a volt and not constant on a control wire for what i believe must be a gate of a power mosfet looks strange. Is it connected to PCM? Is PCM connected to all it's grounds?
Last edit: 7 years 4 months ago by borntoroll.

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7 years 4 months ago #3629 by jonathandean
Hi Thanks again, do you mean has the pcm got all its connectors plugged in? if so yes it has, has it got all its earths, yes from what I can see there are no loose wires hanging anywhere, all the earths I can see are tight plus everything else seems to function ok, all the other bi directional controls work. I have even given the coils a separate ground direct to the battery and this had no effect.

I am still very confused as to why I cannot power the coils independently, do you know should it be possible, for example, to test the coil off the car with a power probe supplying power and ground and the test light supplying the control current?

Thanks for your help with all this I do appreciate it

Jonathan

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7 years 4 months ago #3633 by ImBack218
Replied by ImBack218 on topic Crank no start, no spark
I believe you shouldn't be seeing any voltage at all on the control wire.
Yes that is what I was going to suggest. Remove a coil from the car, give the appropriate pins a power and a ground, and use the test light on the control pin. Use an amp probe connected to the scope when you are doing this, and make sure you give the spark somewhere to go to ground, as it won't be in the car anymore.

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7 years 4 months ago - 7 years 4 months ago #3640 by borntoroll
Replied by borntoroll on topic Crank no start, no spark
Managed to find some wiring diagrams for peugeot 8fs which must be the same as 1.4 VTI. It shows that coils have ground all the time. Also they have power together with injectors from pin 5 of the PCM. It is not clear 100% from the diagram whether coil is ground controlled or power controlled. But looks like a ground control and there is a strange symbol of ground connection over control pins (in that case when you command it with scanner it should light the testlight connected to postitve of the battery and the control pin). But there is no such ground symbol if i open injectors diagram.
Were PCM connectors disconnected? Maybe some pins are bent?
[IMG

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Last edit: 7 years 4 months ago by borntoroll.

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7 years 4 months ago - 7 years 4 months ago #3641 by ImBack218
Replied by ImBack218 on topic Crank no start, no spark
Thanks for the diagrams. I'm pretty sure these are standard coil-over plugs with a transistor inside the coil housing. The transistor emitter circuits are constantly grounded. The collector circuits share a power feed with the fuel injectors. Since we verified power and ground to the coils,, all we need now is for the PCM to send a small voltage on the middle control wire, to turn the transistor on and allow current flow through the coils. The question is why cannot OP do this with a test light?
Last edit: 7 years 4 months ago by ImBack218.

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7 years 4 months ago #3644 by jonathandean
Thanks so much for everyone time and help here, the wiring diagram posted is almost identical to the one I have.

I have tried to manually power the coils off the car, referring to the diagram,
I put a 12 v source on pin 3
A constant ground on pin 2
I touched a test light connected to power to pin 1

I think that is the correct way to do the test?
I didn't get a spark

I thought the coils where power controlled?
The PCM has never been disconnected whilst I have had the car, I can check for bent pins.

The ground source is shared with another component, could the effect things? Although it would't affect the coil operation off the car.

The engine on this car was a joint design with peugeot and BMW it was used on the Mini One models, I can find a spec for the primary coil winding resistance check off a Mini, which says 0.3 ohms, all my coils read 0.8 ohms, does that help?

I really can't thank you all enough for your help here, if any of you are in the UK feel free to call in for a few beers :)
Jonathan

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7 years 4 months ago #3645 by borntoroll
Replied by borntoroll on topic Crank no start, no spark
Did you connect constant ground also to the spark plug?

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7 years 4 months ago #3646 by jonathandean
Hi, yes, sorry I forgot to say that, I had an incandescent test light connected to battery ground just outside the rubber boot of the spark plug, I used an led light to touch the control pin, should that test of worked,

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7 years 4 months ago - 7 years 4 months ago #3648 by borntoroll
Replied by borntoroll on topic Crank no start, no spark
We don't know if there is a power transistor inside the coil we just think it must be there.
1.First of all they must all be connected to one power source.
2. Connect battery negative to pin 2 and a spark plug.
3. Connect battery postitve to pin 3.
4. connect battery negative through a 10k resistor to pin 1. And then touch pin 1 with incondescent test light connected to battery positive.
5. If there is no spark disconnect pin 1. Use the same wire with 10k resistor now connect it from battery positive to pin 1 through a 10k resistor. Now touch pin 1 with incondescent testlight connected to battery negative this time.
6. Don't leave a pull-up/down resistor connected to pin 1 for too long as you can overheat the coil. I think no more than 10-15 seconds to check and then a little pause for a couple of minutes.
Check couple of coils.
Let us know the results.
Last edit: 7 years 4 months ago by borntoroll.

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