VW T4 Forum - VW T5 Forum banner

1 - 10 of 10 Posts

·
Registered
Joined
·
42 Posts
Discussion Starter #1
Around crimbo my 2000 T4 2.5 TDI AJT began to struggle to start. I had fuel pump timing checked twice and it’s band on. Runs beautifully Once it’s going.

In an effort to solve the starting issue I checked the leak back pipes (dry), clear tube (no bubbles) and decided to changed the glow plug fuse in the little box at the battery in case it had a crack etc...I fitted an 80A strip fuse.

On first turn of ignition I get 1v power drain on battery so it appears glow plugs are getting juice.

Climbed in the van an£ gave it a start. Fired immediately! BUT...

Now the van revs to 5000rpm on start up!!!

All I did was change no. 1 glow plug fuse and when I turned the key the van fired immediately but revved straight to 5000rpm without my foot on the accelerator ...switched off key and thankfully it died. Tried again same problem.

Voltage on fuse 1 for glow plugs is good, same as battery.

Pulled the 109 relay and fitted another one. Struggled to fire and didn’t start. Tried again and away it went immediately to 5000rpm again!

HELP 😩

F094164E-B8E5-48DE-B3BC-D2717BB8F8C7.jpeg
 

·
Full of Cr*p....
Joined
·
7,967 Posts
Check that when you changed the fuse, you didn't disturb the wiring/connections to the ECU (directly BELOW that fuse box).
These engines are electronically controlled....so if you damaged any wiring down there....that's what you may get. :eek:
Only takes one broken wire for the ECU to NOT know how fast the engine is rotating, and so gives it as much as it can!
RHD (which I assume yours is) are notorious for wiring problems over the engine as well.
LHD....the loom is straight from the drivers area to the ECU....simples.
On RHD, there is a very poor quality loom that has to run from one side to the other in the engine bay.
Many threads about this in both Engine and Electrical sections of the forum.
 

·
Registered
Joined
·
42 Posts
Discussion Starter #3
I’ll check around the ECU, it’s a jumble of wires in there! I’ve read about the loom issues for glow plugs just below the brake booster so I’ll look for that too. It doesn’t explain the the sudden appearance of this revving issue tho, so the ECU are is worth tidying up.

What about a throttle position sensor Or something like that?
 

·
Full of Cr*p....
Joined
·
7,967 Posts
It could be the throttle sensor, but as you've been "poking around" where the loom that carries the signal from it to the ECU, I'd start checking there.
VCDS will show you what the ECU "thinks" the throttle is at.....but that still won't say if it's the actual sensor, connection to it, or a broken wire to the ECU.

There "shouldn't" be a jumble of wires...just 2 plugs with the cables neatly fixed into the looms.....if it's a jumble, possibly someones had it apart before?
 

·
Registered
Joined
·
42 Posts
Discussion Starter #5
I’ve checked the ecu plugs. Removed the tape checked the wiring and revealed. All dry there.

I tried connecting VCDS-lite but it connect to controller.

Any ideas?
 

·
Registered
Joined
·
28 Posts
Hi. I once disconnected the flywheel sensor and my engine reved straight to 5000rpm. Same engine as yours. Might be worth checking?
 

·
Registered
Joined
·
820 Posts
If i remember well its on the block next to gearbox bellhousing towards the radiator, its end is on the metal bracket that holds the needle sensor plug and injector pump...did you said you reversed some plugs ? The speed sensor has a 3 pin connector either grey or black if the original...looks like this:

 

·
Registered
Joined
·
28 Posts
Hi deluxe. The flywheel sensor or crankshaft sensor is on the front of the engine block next to the gearbox . It's wire goes into the plate under the fuel pump with a few different connectors including the fuel pump one. I think its the connection to the right and when I disconnected it the engine reved out. A bit scary but might have something to do with your problem.
 
1 - 10 of 10 Posts
Top