Electrical problem 940

[Ammorack]

Originally Posted by TonyS9

FYI the fuel pressure regulator is not fully eliminated, the leak test is just a basic test. You need to measure the pressure during the fault condition. (I think you measured it before but maybe in normal condition?)

BTW I think you have 2 fuel pumps, do you know if that is correct, and have you tested either of them in any way? Its possible the lift pump is failing.

Another random thought, adding everything together, feels like a ground problem on one or both of the ECUs. There is a buch of ground points in a big matrix beside the fuel ECU, all these should be connected.

Yes I have measured it before when the car decides to idle fine. Showed 2.5-3.0bar

I have checked ground points around both ECUs

I have two fuel pumps I believe. The one with the filter is renewed and delivers 3 bar. The intank is probably the original one. I haven’t been digging inside that tank. But I do have an Intank pump laying around

[Ammorack]

Originally Posted by TonyS9

Ok interesting video, mainly the idle + rev counter one.

The rev counter is not showing the correct rpms, its like doubling the rpms and really intermittent, its an untrue repesentation, jumping irratically NOT according to actual RPMS. Do you have a after market rev counter to check this with? Either the rev counter is faulty or the signal driving the coil is bad, normally the ignition amp, but I understand you have changed this. Definately give the wiring a good wiggle there (between AMP - coil -Ignition ECU).

It would be good to see if there is double the sparks pulses too. We are getting into scope requirement terratory.

I see why Dave was suspecting the CPS signal. Did you check the shield continuity to ground for the CPS?

When everything is good, do the rpms show the proper idle around 750rpm?

What happens when you squeeze shut the idle air bypass valve pipe (with your fingers)? Does it stay the same or completely die?

And other times its idles normally?

I don’t understand what you mean with “Shield continuity” if it’s Resistance it’s 160ohm. But shield continuity?

If I squeeze the idle hose the car stalls. And the tachometer is still bouncing.

When everything is functioning. It’s 650-750rom I believe
I don’t have an aftermarket rev counter.

[Ammorack]

Sometimes when I turn on the ignition, the tachometer bounces 1mm or so slightly upwards.

[TonyS9]

The shield continuity is just to check it is well connected to ground. The signal is small and is amplified so any noise from ignition system can be amplified into a fake signal. The shield keeps the electrical noise out.

When you unplug the connector for the CPS, put 1 probe on the shield pin (connected to the computer side) and the other on the chassis and check the resistance is near zero (maybe a few ohms).

You can do the same with the CPS cable aswell if you can find a way to connect to the shield near the sensor end. That maybe more difficult.

Additionally the 5V trigger signal going ignition amp from the computer is also shielded. The high voltage spark system needs to be kept away from the delicate computer signals.

[Ammorack]

Originally Posted by TonyS9

The shield continuity is just to check it is well connected to ground. The signal is small and is amplified so any noise from ignition system can be amplified into a fake signal. The shield keeps the electrical noise out.

When you unplug the connector for the CPS, put 1 probe on the shield pin (connected to the computer side) and the other on the chassis and check the resistance is near zero (maybe a few ohms).

You can do the same with the CPS cable aswell if you can find a way to connect to the shield near the sensor end. That maybe more difficult.

Additionally the 5V trigger signal going ignition amp from the computer is also shielded. The high voltage spark system needs to be kept away from the delicate computer signals.

Black cable on CPS loom to chassis is 1.9ohm
Red cable on CPS loom to chassis is 2,9ohm

And on the CPS cable itself? So you mean from the tip of the sensor to chassis?
When it’s grounded to the engine of course

I get no readings on the end of CPS sensor to chassis

[Ammorack]

Or I did this test wrong 🤔

[Laird Scooby]

I've just watched your first video Ammo. Have you got a timing light? As in for checking the igniton timng with the engine running? If so, can you connect it up and let us know (preferably with a video) what it's doing please?

I was thinking this over earlier and i've thought of something definite that would throw everything out and cause this. It's a known fault butwe need to tst for it to make sure.

[Ammorack]

Originally Posted by Laird Scooby

I've just watched your first video Ammo. Have you got a timing light? As in for checking the igniton timng with the engine running? If so, can you connect it up and let us know (preferably with a video) what it's doing please?

I was thinking this over earlier and i've thought of something definite that would throw everything out and cause this. It's a known fault butwe need to tst for it to make sure.

I have actually done a timing light test. When idling it’s out of specs, really far out from 0-15DEG. And on 4000rpm it’s in between 0-15deg. The timing light is not here with me though. So I cannot so a tear with it for now. As it isn’t my tool.

So I have to get a timing light and see

[Laird Scooby]

Originally Posted by Ammorack

I have actually done a timing light test. When idling it’s out of specs, really far out from 0-15DEG. And on 4000rpm it’s in between 0-15deg. The timing light is not here with me though. So I cannot so a tear with it for now. As it isn’t my tool.

So I have to get a timing light and see

Ok, i thought that might be the case. That's probably causing your rhythmic misfire on idle.

These engines have a reputation for the timing pulley (crankshaft) to distort and that causes things like the cam timing to be out.

Do you know how to find TDC using a screwdriver, bolt or rod in the spark plug hole?

If not, i'll explain tomorrow unless someone else can now, had a long, busy day and the brain cell is jelly so not thinking straight enough to explain properly.

Once you find TDC, you need to recheck the cam timing, i'm pretty sure it will be 2-3 teeth late which in turn will make the timin late and try and fire #2 when it should be firing #1, trying to fire #1 when it should be #3 and so on.

[Ammorack]

Originally Posted by Laird Scooby

Ok, i thought that might be the case. That's probably causing your rhythmic misfire on idle.

These engines have a reputation for the timing pulley (crankshaft) to distort and that causes things like the cam timing to be out.

Do you know how to find TDC using a screwdriver, bolt or rod in the spark plug hole?

If not, i'll explain tomorrow unless someone else can now, had a long, busy day and the brain cell is jelly so not thinking straight enough to explain properly.

Once you find TDC, you need to recheck the cam timing, i'm pretty sure it will be 2-3 teeth late which in turn will make the timin late and try and fire #2 when it should be firing #1, trying to fire #1 when it should be #3 and so on.

Super 👍🏻👌🏻

Well i have a cylinder stopper that’s fitted in the spark plug. But it’s originally bought to use on motorcycles. Finding TDC turning the crankshaft and unscrew a plug and check with a tool.

Stupid question - if sometimes it idles fine. Wouldn’t that not be a a timing failure? I don’t kNow. Just a question.

I have changed timing belt and tensioner. But it could have slipped when this problem occurred. so we shall see 👍🏻

I have already marked the timings and 1-2 months ago I checked timingmarks and it were correct. But hey! I’ll check it anyways. Gotta be sure.

Later 👍🏻