Bosch VP30 simple fault diagnosis
As fitted to Rover 25 & 45 and MG ZR & ZS
As a rule the Bosch VP30 pumps fail in one of 3 ways. Its quite easy to diagnose what the problem is.
First of all the three common problems.
1 Timing solanoid failure
2 Metering solanoid failure
3 Pump psg5 ECU failure
Lets look at each one in turn.
The image shows the position of the parts on the pump.
- Timing solenoid failure
IF this happens the engine will still run, but will sound like an old tractor on its last legs. You’ll also get a loss of power. Its not advisable to run for prolonged time as the timing is now heavily advanced and puts a lot of strain on the engine. This can start intermittently or suddenly happen.
The timing solenoid is under the pump. It can be replaced in situ. Heres a link to a howto – Timing Solenoid Replacement. Its held by two torx bolts which are quite hard to get at. Also its sealed against diesel so will be tight to get out. The wiring to it is not on a plug and will have to be cut and spliced. This also applies to the metering solenoid.
Here is a picture of the two solenoids removed from the pump.
- Metering solenoid failure
IF this happens the engine will stop. This usually happens suddenly without warning. It can be confusing as to what the problem is because if the injector pipe union is cracked open, diesel will still come out. Its just not under enough pressure to cause the injector to open.
To replaced the metering solenoid in situ is fairly easy if you have the tools to do it. This YouTube video shows a metering solenoid removing tool being made. It can be made from 32mm pipe, you don’t need to use a socket. http://www.youtube.com/watch?v=uontvecMqI0
You’ll need to remove all the injector pipes, and the extensions that they are bolted to. Once the sleeve has been loosened the metering solenoid can be extracted from the pump, but it will be very tight. To refit you’ll need to use a “C” spanner.
As you tighten the sleeve it draws the metering solenoid into the pump. It will get tight when its fully home. You’ll need to use the extracting tool to just finish off the job as it has to be done up very tight. Careful positioning of the metering unit is essential as it can spin round and the removal tool won’t quite do 1/4 of a turn.
Here’s some tools I made and used
3. Pump psg5 ECU failure
This unfortunately will 99% of the time give exactly the same symptoms as a metering solanoid failure. Sometimes, but not always it will put the engine light on.
To successfully differentiate between metering solanoid failure and pump ecu failure there is a simple test you can perform. Cut the two wires from the pump ecu to the metering solanoid. put a multimeter on the two wires from the pump and get somebody to turn on the ignition. You should see 12volts or there abouts, and then dropping to about 6 volts when the engine is turned over.
If no power is registered the ECU has failed. If you do get power then the metering solenoid has failed.
If the pump ecu has failed is usually down to a crack in the circuit board which cannot be repaired. Easiest thing to do is replace the pump in this circumstance as removing the circuit board from the pump is very difficult due to overly tight torx screws that are not very strong.
As you can see I managed to get them out, but don’t even try unless you have a quality T10 torx bit. A cheap one will just break off in the top of the screw.
After replacing solenoids
The pump will be totally drained of diesel and despite pumping the priming bulb and bleeding at the injector pipes the engine can be very hard to start afterwards.
Article originally written my Cap’n ZS