Weird Starting Fault Help!

[Telf 224 2 Cars]

Right starting fault on my GTI. The starter won't turn over. If I connect to another car that's running via jump leads it starts. I've fitted a new starter and tried a new battery. Still won't start. I'm thinking it must be earth related as from the other car it's only getting power/earth. Any ideas please

[welshpug 1,661]

try attaching a jump lead from engine to chassis or negative terminal.

[Telf 224 2 Cars]

So I have 12 volts at the starter, a signal on the solenoid when you turn the key. I have checked the earth on the gearbox and cleaned the stud - confused now! The car will only start when hooked up to my mondeo whilst it's idling

[Telf 224 2 Cars]

I've also cleaned both contacts on the starter and disconnected the alternator just in case that was causing some random issue

[j_turnell 137 3 Cars]

As Welshpug mentions run a jump lead from your battery neg to the engine/chassis and see if it starts. Sounds like your main earth lead or connection is at fault.

[Telf 224 2 Cars]

Hi sorry tried that , it doesn't start.the only earth I'm aware of is the one on the gearbox

[toolie72 67 1 Cars]

What happens to battery voltage when it won't start

[oldkiteman 6]

It sounds like a bad connection either in the ignition switch or wiring.Try un-plugging and re-plugging the smaller brown connector under the steering column just to the side of the heater.It starts when jump leads are connected to a running car as this bumps the voltage to 14.4volts which overcomes the resistance.You could also try disconnecting the smaller of the two plugs and connect a good 12volt supply to the thick blue wire which should make the starter turn.

[oldkiteman 6]

If you look on the " XU16v engine maintenance and upgrades" thread and then click on the GTI6 engine wiring loom guide,and scroll down,there is a picture of the connectors and a list of what each wire does.

[Telf 224 2 Cars]

I've not measured the voltage as it trys to start. It's now had 1 new battery and a borrowed one none of which start the car. It doesn't even crank. The solenoid doesn't click. Nothing happens except you can hear fuel at the rail. I will have a look at the connectors under the column. I haven't measured the voltage at the battery as I say it won't even begin to crank.

[Telf 224 2 Cars]

Will report back on sunday

[Anthony 1,003]

I bet it's voltage drop on the solenoid wire, and having the jump leads attached with the other engine running boosts the voltage just enough for the solenoid to work.

 

You need to have the solenoid wire attached to see how it drops when you turn the key. If you can do so, touch 12v positive wire from battery to the solenoid and see if it then cranks... I'm betting it will.

[Telf 224 2 Cars]

Anthony there is a voltage on the wire but it's not 12 volts. More like 5. I have been looking to see what voltage in should have there but haven't found anything.

[Telf 224 2 Cars]

I also split the brown multi plug as I believe the solenoid wire passes through there. The contacts all looked good but I cleaned them anyway. Will look again tomorrow, thanks all.

[Telf 224 2 Cars]

fault found, loose connection in one the ignition barrel plugs!

 

thanks all

 

[Telf 224 2 Cars]

ive collated a few bits I found on the forum that might be of use one day to someone else:

 

 

Starter solenoid wire connection in fuse box area

 

[Telf 224 2 Cars]

and here is the pin out for the brown plugs (as linked)

 

 

Solenoid wire under dashboard is on the brown connectors as follows:

 

 

here is the wiring details for the 205 two brown plugs under steering column (as shown earlier),this is how they were on mine:

9 Pin plug

52 Reverse light (dark grey)
53 Reverse light (purple)
47 Coolant light (yellow)
47a coolant gauge (red)
7a Alternator light (dark grey)
30 oil pressure light (purple)
30a oil temp gauge (white)
30b oil pressure gauge (grey)
32a tachy relay (yellow)

6 pin plug

76 fuel pump (white)
M ignition amp (green/yellow) (Permenant earth)
112B tacho feed (grey)
112c not connected ( green)
2a switched live (red)
46b starter (blue)

with a diagram:

 

 

 

 

[Telf 224 2 Cars]

Also a couple of bits of wisdom from various posts:

 

 

The only connections inside the engine bay is the brown multiplug of doom (although if memory serves me right that had been removed on yours and replaced by a black plug near the passenger headlight) and the connection on the back of the starter itself. There could have been repairs to the loom over the years of course, but impossible to say without seeing it.

The route inside the car is somewhat more torturous, going from the ignition barrel to the fusebox, back across the car to the brown multiplugs under the dash, probably with your alarm/immobiliser installed somewhere in the middle. This wiring rarely gives problem - problems inside the car are usually down to immobiliser problems (especially the poor standard most of them are installed to) and increasingly worn out ignition switches.

 

and a simple way to check the solenoid:

 

Short the battery power terminal on the starter to the solenoid wire just above it, and see if the starter cranks over good. If it doesn't, it's clearly the starter, an earth strap or else just poor voltage/cabling to the starter itself (ie. battery leads or the battery condition itself). Will at least help you rule out the low-current trigger circuit. Just make sure it's not in gear when you do it

Again thanks all for the help much appreciated !

[Telf 224 2 Cars]

Well the fault returned. It wasn't the connector it was the immobiliser wiring spliced into the ignition