How to replace the Head Seal on the Bosch VE Injector Pump without removing the Pump.

The injector pump on can often develop a minor leak from the rear distributor head The leak will often start off slow but over time it will worsen, losing fuel each time the engine is started or stopped, and drip all the time in between. This will also make cold starting very difficult.

If your not in a position to do the repair or fault find immediately  fitting a Non-Return Valve will help lessen the symptoms. We have a Guide to doing this here.

The cause of the leak is often the hardening of the O-ring around the rear pump head. This is caused by the removal of sulphur from diesel fuel many years ago. The sulphur acted as a lubricant to keep the seals supple and its removal allowed seals to harden and leak.

Our aim is to replace this with our Viton seal which is more robust and better suited to modern day fuels.

Click here to read about the Viton Bosch VE pump head seal O-ring.

The hardened (and brittle) O-ring which caused the leak 

Removing the pump to replace the seal it is not a trivial job.
it required only a few spares, some fairly normal tools plus a day of work.

No technical skills are required, and someone with reasonable car maintenance experience could do it.

Usually, unless there is something else wrong with the pump, there is no need to go to the expense of a professional rebuild.

So Before starting the repair please read all you can find about the Bosch VE pump.

especially the warnings about engine timing and how not to lose it. (If removing the pump)

Also, ensure you have the item listed below.


In preparation, you’ll need the following items.

First Steps  

Thoroughly degrease and clean the side of the engine, pumps and fuel filter with degreaser.

Take plenty of photos of the location of pipes, bolts and cables to aid subsequent reassembly.

Move any cables and water pipes aside and hold with tie wraps to provide easier access to the pump area.

Disconnect the battery to prevent the engine from being turned accidentally.

Mark the fuel direction on the 2 fuel filter pipes from the lift pump and the return to the tank using sticky tape to avoid later confusion.

Remove the fuel pipes between the filter and the injector pump.

Remove the remaining fuel pipes from the top of the injector pump.

Release the throttle cable end from the pump lever.

Remove the high-pressure fuel lines from the head of the injector pump. Put them aside so that no dirt can enter the pipes.

Cover the exposed ports on the injectors and the rear of the pump with tape or screw caps to avoid dirt falling in.

The injector pump is now more accessible.

Resealing the Pump

First, remove the top lid of the pump so that you can see inside at the plunger.

Using the lid section of your squirter drop the straw into the pump and pump out any fuel from inside.

You need to rotate the engine ideally with a spanner on a pulley till the plunger is fully extended towards the pump head. • Once in this position be careful not to let the engine rotate either via the gearbox or starter motor.

If any brackets or obstructions share any of the 4 head bolts like in the picture above these will need to be removed taking note of the length of the bolt for the next steps.

These bolts will be T30 Torx head.

From your 4 head bolts, 2 of these should be slightly longer than the other 2 by around 5mm.

Now pay attention to this bit 

Without loosening the head from the body and remembering there an original location we need to find the 2 longer bolts and place them at opposite corners of the square head.

Once they are in place you can fully remove the 2 shorter bolts.

The 2 remaining bolts will the ones we will eventually use to evenly loosen the head from the pump body.

Remove the fuel cut off solenoid from the distributor’s head and carefully remove the plunger and its spring.

This is usually a 24mm or a 15/16in spanner or socket.

The distributor head covered in smooth tape.

To access the O-ring, the distributor head must be partly (but NOT completely) released.

Place some smooth tape around the rough exterior of the distributor’s head so that the new O-ring is not damaged during fitting, but don’t cover up the bolt heads or holes, access will be needed.

Undo the remaining 2 bolts progressively until you can see the head moving upwards (The head should be spring loaded and come up by itself). The head only needs to be removed this far.


Installing the new Viton Bosch VE pump head seal 

Continue to undo the 2 bolts progressively, ensuring that the head is coming up with them. Continue this until the O-ring can just be seen but no more.

The head may need to be lifted gently to ensure this but don’t allow the head to come completely out.

Carefully lift and cut the O-ring and remove it but don’t scratch the groove that it sits in.

Clean the O-ring groove as well as possible.

Now the new O-ring can be fitted.

Replacing the broken seal for a Viton Bosch VE pump head seal.

Grease the outside of the tape and the new O-ring with red rubber grease. This will help stretch it over the distributor’s head without damaging the Seal.

Slide the O-ring down until it drops into the gap and carefully manoeuvre it into its groove on 2 sides. It will still be on the outside of the 2 bolts as shown in the picture below.

Using your supplied extra bolt place it in an empty hole to hold the head in the same position, being careful not to damage the O-ring on the way.

Holding the O-ring away from the threads, remove the other 2 bolts one at a time and allow the O-ring to slip into the groove and replace it until it takes the tension of the head again.

Once the O-ring is fully in its groove, tighten all 4 bolts progressively so the head slides evenly back into its location.

Remember to put the long and short bolts in the correct order at this point and replace any brackets that utilised these bolts.

Reinstall the fuel cut off solenoid with the plunger and spring.

If no other work is required on the pump, the resealing task is complete.

The injector pump complete and ready for refitting

Reassembly Notes

While it is empty you should check inside to ensure that no components had moved or fallen out during the resealing process.

Use Loctite on all major bolts and nuts, as in my case none of them had spring washers or nylon nuts and you don’t want these critical parts to come loose.

Clean everything well before reassembly, especially oil passages where dirt or bits of the hardened gasket may have lodged.

Priming the System

Loosen the banjo nut on top of the fuel filter and use the priming lever on the lift pump to fill the bowl until fuel comes out of the banjo nut, then tighten it.

Don’t forget to refill the radiator and check for water leaks.

Testing the System 

Once Everything is back in place ready for testing Loosen the injector nozzle nuts on cylinders 2 and 3 slightly to allow air trapped in the injector pump to be cleared after the engine first starts. A mist of diesel will squirt out so keep clear of the injectors. After about 10 seconds, stop the engine and tighten the nuts.

If for any reason something goes wrong and the engine over-revs, be ready to remove the fuel inlet pipe.

Recheck the water level after a few test runs and the task is complete.


I accept no responsibility for loss, injury or damage caused by your use of this kit. A successful repair depends on your own skills and fault finding ability, for this reason alone I can not be held responsible if your fault is not cured after you fit this kit.


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