Engine Bay Loom

[griffsmith]

Hello
I need some help I think I've got a gremlin hiding somewhere in my engine bay loom just behind cyl no.8. I was hoping someone who has taken the engine out has got or can take some pictures of the loom in that area. Because I'm not taking the engine out to find the problem (yet!) it would be really handy to see where I'm hunting..
I know its not pleasant seeing a grown man beg... but...

please please pleeeeeese.....
chris

[GreenV8S]

Do you know which loom is causing trouble? There are two looms are that area. The engine loom comes through the side of the passenger's footwell, and splits up with one half going down each side of the engine. On my loom the area where these two halves meet up is very messy with some bits of the loom going back and forth across the back of the engine to use up spare length. This loom basically connects the ECU to the injectors and sensors on the engine. Any problems here should be apparent if you do a circuit check at the ECU plug.

The second loom runs along the off side rocker cover and through the bulkhead in front of the driver. This loom contains the main power from the starter motor, the feeds to and from the alternator, and the switched ignition to the coil and the signal from the coil back to the rev counter.

[griffsmith]

Hi what I really want is a picture of a loom in the car with the engine out just to use as a bit of a map realy cos I won't be able to see as much with my engine in..

I think the problem is somewhere around the stepper motor connector branch where it joins the main loom, either at that junction or near to it when mounted in the car. I'm wondering what other sections of loom are around there.

I know I'll see more once I start taking bits off just wanted a heads up on what to expect.. can you tell if the injector or ignition wires are around there just wondering what might cause a misfire??

cheers

delayed typing ment I missed your reply GreenV8S cheers it sounds like plenty of candidates then.. looking good for the ECU loom though. will do the plug checks but I'm not confident it'll show up that way.. however a good place to start. cheers

>> Edited by griffsmith on Tuesday 22 November 22:14

[griffter]

It's worth checking the earth tag on the back of the n/s cylinder head. You can just see it with a small mirror and a torch. AFAIK it earths the injectors and so is fairly crucial... It's just a ring terminal secured to a threaded stud with a nut and wsaher. From memory, everywhere else behind the engine, the loom just runs, but doesn't connect to anything. Of course a section of it runs under the plenum.

Are these new symptoms or the old ones unresolved?

[griffsmith]

griffter said:

It's worth checking the earth tag on the back of the n/s cylinder head. You can just see it with a small mirror and a torch. AFAIK it earths the injectors and so is fairly crucial... It's just a ring terminal secured to a threaded stud with a nut and wsaher. From memory, everywhere else behind the engine, the loom just runs, but doesn't connect to anything. Of course a section of it runs under the plenum. Are these new symptoms or the old ones unresolved?

Cheers for that Griffter, I've had a good 'feel around' there already and it seems ok.

These are new symptoms unfortunately. after being great all summer, the car has had a patch of bad luck recently starter motor failed, now this.. the misfire was evident after the starter motor was replaced and was initially very bad then the specialist noticed the car would stall when moving the stepper motor loom I can't repeat this at the mo but it still has a constant misfire
I'm really hoping it will be obvious. but you know what these things are like!

[raw-sewedge]

Any good?

[griffsmith]

raw-sewedge said:

Any good?

Not bad at all thanks raw-sewedge... Do you know which part of the loom is heading up and over the driverside windscreen?? the stepper branch attaches to the O/S injector loom if my eyes don't deceive but I can't zoom in without loosing detail.. has anyone got any close ups of that section.

thanks

[raw-sewedge]

The branch heading off over the drivers wing runs throught the valley under the inlet manifold and connects to Dizzy/Otter switch/Oil pressure switch etc...

The Stepper connection joins the injector leads as you say and there is the plug for the offside Lambda here too.

PS. YHM. Drop me an email so that I have your email address and I'll send you the original picture which is bigger.

>> Edited by raw-sewedge on Wednesday 23 November 12:17

[griffsmith]

raw-sewedge said:

PS. YHM. Drop me an email so that I have your email address and I'll send you the original picture which is bigger.

thanks YHM also (I can't recieve PM at work but will pick these up laters)

cheers

>> Edited by griffsmith on Wednesday 23 November 12:58

[griffsmith]

Cheers guys I started this evening with simple ECU loom checks from the ROVER EFI manual on RAW-SEWedge's www.warks-tvr.org.uk/ site. A great resource I keep forgetting

'First' gremlin located.. I found a error on the O/S injector bank, reading a 5-6 ohm resistance. With a few more checks it turned out to be injector no.4. When I check the injector directly with a meter it seems fine 16.3ohms. So I suspect the connector or wires. Any ideas or experience of how to locate where the fault is??? are the injectors looped or do the wires from each injector all connect together in a common place on the loom??

All other checks on the ecu loom seem fine so maybe the rest of the loom is fine.. still one step at a time, fix this one a see..

[GreenV8S]

The four injectors in each bank are spliced into a single wire to the ECU.

Wth four injectors in parallel you'd expect to see about 3-4 Ohms. If you're seeing 5-6 Ohms that indicates that the circuit through one injector has gone open circuit. It may be in the ignition supply, or the return to the ECU. A continuity test between each injector plug and the ECU plug would show which side of the circuit was fault and which injector it affected. Then it is 'just' a matter of finding where abouts in the loom the break occurs. The only way I can see to do that is to unwrap the loom and look for mechanical damage (often you can feel where the wire has broken) if that fails then you are left sticking pins into it.

[griffsmith]

GreenV8S said:

The four injectors in each bank are spliced into a single wire to the ECU.

I'm wondering where this/these splices are? is each injector spliced separately inside the loom that runs along the inlet manifold or is there one common location somewhere in the loom behind the engine where they are all spliced in together?? this defines which sections of loom are suspect.

GreenV8S said:

With four injectors in parallel you'd expect to see about 3-4 Ohms. If you're seeing 5-6 Ohms that indicates that the circuit through one injector has gone open circuit. It may be in the ignition supply, or the return to the ECU. A continuity test between each injector plug and the ECU plug would show which side of the circuit was fault and which injector it affected. Then it is 'just' a matter of finding where abouts in the loom the break occurs. The only way I can see to do that is to unwrap the loom and look for mechanical damage (often you can feel where the wire has broken) if that fails then you are left sticking pins into it.

I'm not liking the sound of tracking it down with a pin, but needs must. I know its no.4 injector and will narrow it down as you suggest to ign supply or ECU return. then start at the plug and work back.. cheers

[raw-sewedge]

griffsmith said:

RAW-SEWedge's www.warks-tvr.org.uk/ site. A great resource I keep forgetting

Thankyou ,wait till Quinny sends me all his notes