Help needed! DX engine wont run with x-over relay 17 plugged in

Hi all,

I drive a MK1 DX '83 GTI.

This morning when I wanted to go for a ride the engine started but wouldn't keep running.

Quickly it became clear that the engine started on the cold start system but after that initial 3 or 4 second 5th injector spray the engine cutted of. So my first guess was an electrical issue.

I checked all the fuses, they were all ok.

Then (thinking it was the fuel pump relay because it clicked when I initiated the contact at the key) I unplugged relay 17 (X-over) and tried again to start to see how the engine would respond. To my big surprise the engine started and kept running perfectly.
Now after reading a bit I know that it is the X-over (17) relay and not the fuel pump relay. And that because of unplugging this one the heater etc didn't worked anymore. But I still do not understand why unplugging the relay keeps my car running.

The car was running perfectly before, never had any electrical issues.
A few months ago however I tested my injectors and so I took power from/via the solenoid or the WUR (I think but not sure anymore… I think I read this trick here on the forum but cannot find the thread no more)  to keep the pump spinning while testing. After that I didn’t drove the car. Although I used a cable with a fuse, I guess I must have messed some electrical things up …

Can anyone of you smart guys help me where to start diagnosing this issue, because I can’t get my head around it …?

Thanks!

Nobody out there that can give me some decent advice?

so 17 x over is upside down ?

nicci21paul said

so 17 x over is upside down ?

You mean mounted upside down?
Seems to me that would be weird since it has been in there without issues for 4 years.

It isn't 17 X-over. that is the Load reduction relay, it effects the X circuit path, as in the start position of the ignition switch it cuts out the High Load Circuits when you try to start the car.

They are blower motor, headlights, to mention a few.



A good explanation is here:
The "X" Circuit from the Ignition Switch. | VW Vortex - Volkswagen Forum

In my experience the usual suspects are:

Bad Grounds, Battery to frame and frame to engine.  If you do a voltage test on the Cables, and there is more than a 1/2 volt drop, replace teh batter to frame and frame to engine cable, yes you can use 2 off the shelf units from a car parts store.  If it is still Original unshielded Copper that is dull colored, crusty, or green, replace it.

The other suspect is the ignition switch.  I owned a 81 Westy Built Rabbit diesel for 20 years, and the Load Reduction relay was never an issue.
I have owned a 89-90-92, and 93 Cabriolet, and they too never had any load reduction issues.  It is always something else, and a bad ground can cause enough of a current interruption that can stop the things from running.

I had a 89 Oldsmobile 402, that wouldn't start on days it was 50 degrees and humid or raining.  If it wasn't raining it would run great.  I rebuilt the Diz and that seemed to take care of the issue,,, for about 2 months then same-o same-o no start.  I got mad wrenching on the car one rainy blustery day and the wrench that I was holding slipped out of my cold hand and fell across the Negative terminal of the battery, and frame ground and sparked… needless to say I took the battery cable loose, and pealed back the sheath, and about 4 inches back of the terminal end was the prettiest display of Green and white powered corrosion…

A quick test is to take a pair of battery cables, and connect one from the Battery to the Frame of the car, the Strut mount nuts is a good place then attach the other from the Battery negative cable to the rear lifting eye of the engine if the car now functions correctly, change your grounds.
 

Briano1234 said

It isn't 17 X-over. that is the Load reduction relay, it effects the X circuit path, as in the start position of the ignition switch it cuts out the High Load Circuits when you try to start the car.

They are blower motor, headlights, to mention a few.



A good explanation is here:
The "X" Circuit from the Ignition Switch. | VW Vortex - Volkswagen Forum

In my experience the usual suspects are:

Bad Grounds, Battery to frame and frame to engine.  If you do a voltage test on the Cables, and there is more than a 1/2 volt drop, replace teh batter to frame and frame to engine cable, yes you can use 2 off the shelf units from a car parts store.  If it is still Original unshielded Copper that is dull colored, crusty, or green, replace it.

The other suspect is the ignition switch.  I owned a 81 Westy Built Rabbit diesel for 20 years, and the Load Reduction relay was never an issue.
I have owned a 89-90-92, and 93 Cabriolet, and they too never had any load reduction issues.  It is always something else, and a bad ground can cause enough of a current interruption that can stop the things from running.

I had a 89 Oldsmobile 402, that wouldn't start on days it was 50 degrees and humid or raining.  If it wasn't raining it would run great.  I rebuilt the Diz and that seemed to take care of the issue,,, for about 2 months then same-o same-o no start.  I got mad wrenching on the car one rainy blustery day and the wrench that I was holding slipped out of my cold hand and fell across the Negative terminal of the battery, and frame ground and sparked… needless to say I took the battery cable loose, and pealed back the sheath, and about 4 inches back of the terminal end was the prettiest display of Green and white powered corrosion…

A quick test is to take a pair of battery cables, and connect one from the Battery to the Frame of the car, the Strut mount nuts is a good place then attach the other from the Battery negative cable to the rear lifting eye of the engine if the car now functions correctly, change your grounds.
 

Thx Briano!
Ok, I will try to investigate the grounds. but my gut says the issue lies not there.

All wiring has been rebuilt , the car sits in a dry garage. The battery has been moved to the trunk of the car with a new ground cable installed. All this has been done aprox 4 years ago and had no issues what so ever.
So it seems weird to me that now all the sudden I'm faced with this issue due to corroded electricity.
I still think I must have broken something or melted a cable or so when powering my pump with the injection tests.

It baffles me that when I remove relay 17 the engine runs without issues …

When you remove the relay, it is the same thing as starting the car. The High Current loads are removed from the circuit.

When the key is removed from the start to the run position, it re-picks the load reduction relay.
When this relay is picked or closed, it add the hi-current things in the path of current flow.

So it is the addition of the "extra" loads on the circuit that is causing the Problem.  This Load is probably reducing the ignition current, IE: Coil, Dizzy, or interrupting the Fuel Pump relay.  The Fuel pump relay is problematic.  You could try Jumpering it out, or replacing the fuel pump relay with the horn relay as a test.  If the car runs after jumpering or replacing the fuel pump relay, then you know it is either the Fuel Pump relay (they go bad often enough or the ignition switch.
BE WARNED that if you jumper or swap in the horn relay for the Fuel Pump Relay, then the fuel pump will run with the ignition switch on.

Grounds are the Bane of VW hood, and just because it is only 4 years old, is the main Battery ground in the trunk
to the frame in the Trunk, and You are using frame to engine as the ground path to the engine.  Same for the Battery Positive back to the engine compartment.
 E=I X R, adding additional cable to the run you have to increase the diameter of the cable, which can either reduce the current or decrease the voltage that the Engine requires.  

Don't discount what I have stated, as I have see weird electrical things happen over the years as a Aircraft, or Computer Repair person.
And for what it is worth, I had quite a few issues with my 72 Rover 3500S, and that battery was in the Trunk until I got it figured out.  I cut my teeth on Lord Lucas, Prince of Darkness.

Briano1234 said

When you remove the relay, it is the same thing as starting the car. The High Current loads are removed from the circuit.

When the key is removed from the start to the run position, it re-picks the load reduction relay.
When this relay is picked or closed, it add the hi-current things in the path of current flow.

So it is the addition of the "extra" loads on the circuit that is causing the Problem.  This Load is probably reducing the ignition current, IE: Coil, Dizzy, or interrupting the Fuel Pump relay.  The Fuel pump relay is problematic.  You could try Jumpering it out, or replacing the fuel pump relay with the horn relay as a test.  If the car runs after jumpering or replacing the fuel pump relay, then you know it is either the Fuel Pump relay (they go bad often enough or the ignition switch.
BE WARNED that if you jumper or swap in the horn relay for the Fuel Pump Relay, then the fuel pump will run with the ignition switch on.

Grounds are the Bane of VW hood, and just because it is only 4 years old, is the main Battery ground in the trunk
to the frame in the Trunk, and You are using frame to engine as the ground path to the engine.  Same for the Battery Positive back to the engine compartment.
 E=I X R, adding additional cable to the run you have to increase the diameter of the cable, which can either reduce the current or decrease the voltage that the Engine requires.  

Don't discount what I have stated, as I have see weird electrical things happen over the years as a Aircraft, or Computer Repair person.
And for what it is worth, I had quite a few issues with my 72 Rover 3500S, and that battery was in the Trunk until I got it figured out.  I cut my teeth on Lord Lucas, Prince of Darkness.

Ahaaa, that's a clear explanation! I hope to get to it this weekend! Thx Briano  

If you have redone the electrics, have you had your battery tested?  sometimes I forget the easy stuff.

You need a good battery especially with longer cables running from the back of the car to the engine.

Battery was new since the 4 years ago and hangs on a trickle charger. But will test for sure

So, the trickle charger wasn't doing it's thing lately, so the battery wasn't up to point. Charged the battery put the relay back and started the car. Everything seemed normal. Let it warm up, restarted it a few times, all seems well for the moment.

So it could well be that the battery is nearing it's end off live… It was a cheapo I admit…
I will test again tomorrow with a cold engine but hopefully it was the battery that was causing this weird sh$t.

Many thanks for your assistance! 🙏🙏

Well I haven't seen a true 5 year battery in Years.  The most we can get over here is 3 year. So I suspect that your battery is nearing END of life. If it is a Non-Maintenance free Battery, then you may need to add electrolyte.

I would still clean your ground and power attachment points.