Injector wiring loom

[MisterTee]

Thinking about it, none of the plugs were wet when I took them out, which could also suggest fuelling.

Other than changing the injector loom, what else could I try?

Many thanks

Andy

[GreenV8S]

MisterTee said:

Other than changing the injector loom, what else could I try?

Investigate along the lines I described. It will probably not be difficult to diagnose since the symptoms are consistent and obvious. It may be a fault in the loom, but I wouldn't assume that yet.

[Penelope Stopit]

MisterTee said:

Thinking about it, none of the plugs were wet when I took them out, which could also suggest fuelling.

Other than changing the injector loom, what else could I try?

Many thanks

Andy

Penelope Stopit said:

RayTVR said:

Hi Andy,

Do you know if its definitely the loom at fault? I have a 'star tester' box which can be useful for doing a wiggle test to help isolate intermittent connections which you'd be welcome to borrow

This is the way forward
You could make a test lamp using a 60 Watt headlamp bulb which will draw 5 Amps through a circuit

• *Disconnect Injectors and ECU so as not to burn anything out***

Supply injector cables (or any other circuits cables) with a fused positive and earth their other ends through the 60 Watt test lamp bulb, you should get a fully illuminated bulb and can even measure the voltage with a multimeter while the cables are under the 5 Amp load

Most good/new injectors will draw less than 1 Amp and I doubt any good/new injectors will draw 2 Amps or more

If the loom you are using is breaking down when carrying less than 1 Amp injector current, the loom will definitely break down when attempting to carry 5 Amps test lamp current

Good luck in finding the fault.....they're a pain

[chiefyo]

Use a noid light to test the feed to your injectors and then work from there. Google noid light and it will be explained if needed

[MisterTee]

Thanks chiefyo, might give them a try!

Andy

[Penelope Stopit]

Don't get A Noid if it doesn't help much

[MisterTee]

I’m already pretty annoyed ....spent a fortune getting the engine and gearbox rebuilt and haven’t even driven it yet!

[Penelope Stopit]

MisterTee said:

I’m already pretty annoyed ....spent a fortune getting the engine and gearbox rebuilt and haven’t even driven it yet!

Good luck in getting it sorted

[MisterTee]

Well, after how many Sundays of rain, I finally managed to get the car out of the garage so that I could try and trace my problems with the use of a Star Tester, kindly loaned by @RayTVR 👍

Without the engine running, the star tester shows two error codes - 16 and 12 :-

16 - Electronic ignition - IDM circuit fault
12 - Idle Speed Control motor or Air Bypass not controlling idle properly

Sadly I wasn’t able to run the test with the car running due to the battery going flat (note to self!) before I managed to get the thing to fire.

Also, the injector loom that Ray also loaned me did not fit due to different connectors (see pics below).

So, apart from stating the obvious (the problem is electronic ignition and ISCV), anyone got any suggestions as to where I should start with this please?

Ta

Andy

Injector loom connectors (my car)


Borrowed loom

[RayTVR]

Injector loom was bought as a spare and I've never tried it

I have a spare ISCV (which I have tested and know works), but I don't think this sounds like the issue (normally a faulty ISCV just mucks up the idle)

The IDM signal is a monitor back to the ECU which tells it that ignition is firing and is used as a feedback to help the timing.

The signal comes form the ignition amplifier - mounted on the side of the distributor. Maybe start by checking wiring here looks ok and nothings loose or not connected?

[MisterTee]

Thanks Ray

I did check that the plug into the dizzy was tight and fitted properly. Couldn’t see anything untoward, but probably needs a closer inspection. At least it’s a starting point, which is more than I had before!

[Penelope Stopit]

MisterTee said:

Any other ideas on this really welcomed

MisterTee said:

Been and had a poke about this morning and the full near side bank of cylinders are not firing at all. Whipped the plugs out and gave them a clean, but no different.

MisterTee said:

Thinking about it, none of the plugs were wet when I took them out

MisterTee said:

Without the engine running, the star tester shows two error codes - 16 and 12 :-

16 - Electronic ignition - IDM circuit fault
12 - Idle Speed Control motor or Air Bypass not controlling idle properly

MisterTee said:

So, apart from stating the obvious (the problem is electronic ignition and ISCV), anyone got any suggestions as to where I should start with this please?

Ignoring 16 - Electronic ignition - IDM circuit fault for the time being

Have a hunch what's happening, wish the car was here to prove it

Looking at the below diagram found here in these forums some time in the past

The idle speed control connects to one bank of injectors signal cable

There is a diode in parallel with the idle speed control that will very likely be in the loom

One bank of injectors will cease to operate if the idle speed control is going short or semi short circuit, its wiring going short circuit or the above mentioned diode is short circuit or wired the wrong way around

Hoping that the above helps find and solves the problem, should the problem not be due to any of the above mentioned, a short circuit on the same injector banks signal cable will cause the injectors and idle speed control to fail

Due to the loom being new, DIODE problem is setting off the alarm in my head

[MisterTee]

Many thanks for your reply Penelope. It definitely sounds like you could be on to something here.

Unfortunately, I’m useless with electrics and electronics but will ask at our club meet tomorrow whether anyone can help.

Will keep you posted.

Thanks again.

Andy

[Penelope Stopit]

Glad to possibly be of some help

A Fault like this can be a nightmare for the likes of yourself, a multimeter will show the fault if it is as mentioned above

A good first test.......

Disconnect the ECU and idle speed control and check the resistance of one bank of injectors and then the other bank, the readings should be similar if not exact (length of cables come into play)

As shown in below diagram, Injector relay, fuel pump relay and injectors supply cable all join up in the loom, there are two other cables at this same joint that go to ECU Pins 37 and 57

Let's use ECU Pin 57 to help with testing as it's accessible with ECU disconnected

One bank of injectors are connected between ECU Pins 57 and 58

Other bank of injectors are connected between ECU Pins 57 and 59

With ECU and idle speed control disconnected, check resistance of each injector bank

Resistance between ECU Pins 57 and 58 = ?

Resistance between ECU Pins 57 and 59 = ?

You need to know all is good with the above tests before looking into the diode, but.......

The diode prevents a voltage produced by an electro magnetic field (EMF) created and broken when the valve is switched on and off travelling back to the ECU and damaging it (exactly the same as relays that have a diode or resistor across their coils do)


XXXXXXX Below Not Recommended XXXXXXX

Hence, going by the above, the diode could be removed and the circuit still possibly work
Not a good idea though as ECU's aren't cheap

Now wondering if the diode has been fitted and wired as it could be easily missed out

Good luck in finding the problem, the above information may help if someone is going to be assisting you with testing

[RayTVR]

Any update or joy with this Andy?

[Penelope Stopit]

Long time now since last update, hope all is well and next year brings a fix

[Penelope Stopit]

May help, shows idle valve diode in loom (Ford 2.9)
http://www.gbsportscar.com/TVR%20Body%20Off/wiring...

[MisterTee]

Hi all

Apologies for the lack of responses.

Thanks for the info. I’m almost convinced it is the wiring loom, so in contact with the company who made it for me.

I’m determined to get this sorted before the Spring - I can’t be having another year without my TVR!

Happy New Year folks

Andy

[magpies]

All the best for 2020 Andy

after an unexpected full year off

Hope to see both your and my S's on the road this year

Se you at the next Tees Valley Region meeting

[Penelope Stopit]

You live, all is not lost then

Had a thought today between wine breaks that the plug on the valve was possibly the same as the injector plugs and has been connected to an injector but

Don't know if they are the same plugs

Wouldn't explain how it ran ok on the rolling road and deteriorated later, unless something was disconnected for other work and not put back correctly

Anyway, hate unsolved problems like this, the answers out there somewhere or in here

Good luck and all the best