Bosch Diesel Injection Pump Disassembly

MikeT · Unread post by **MikeT** » 24 Oct 2009, 19:19

DISCLAIMER: Any alterations you make are at your own risk. I take no responsibility for how you use this information.

2nd DISCLAIMER: This is not gospel - this is my understanding, opinion if you like. To err is human so expect mistakes! I welcome any corrections.

I base this guide on all the knowledge I've aquired from other people's generosity to share theirs.

This is my first attempt at stripping and rebuilding a Bosch VE injection pump, as found in many of our French diesel cars and vans (as well as other vehicle makes).

If we believe the Haynes (BoL), we have an "AS3 VP20" (whatever that means) in our Xantia 1.9TD's but when I compared the description and pictures, I found there are significant differences to the one in my car so at this point of time I'm confused as to what the exact configuration of any pump is! It seems that Bosch give them two different types of part numbers, the car makers use a different one and here we have Haynes calling them by yet another. To confuse myself more, the one I am going to rebuild in this thread is supposedly off a "PEUGOT 306 T REG" (and is again, obviously different to my Xantia's pump) though I can't actually reconcile it's Bosch part number with that particular vehicle (yet), so who knows what it's off. What I do know is that they are all from a family of Bosch distributor axial pump types known commonly as the "Bosch VE".

I don't even know if it's actually serviceable so let's go find out....

Tools Required
(As I use the tools, I will edit and update this paragraph)
21MM or 13/16" socket for Pulley Sprocket nut
24MM, 17MM, 14MM, 10MM, 8MM socket and/or spanner
T20 and T30 male bit for various bolts
5MM Allen key for governor cover
A few spare nuts to act as spacers for the Distributor Head bolts.
Some clean, lint-free rags and/or paper towels to mop up and clean the diesel that's lurking within
Some disposable gloves to protect the hands
A box of freezer/sandwich bags (and a marker to pen) to keep the parts free from contamination and a large enough box to store them all in if you're not going to be rebuilding it immediately afterwards

WARNING
If you've read any other service guides you'll know that cleanliness is very important. There are small exact passageways inside the pump that must be free of even the smallest spec of dust or dirt. Ok, soft particles will probably get ground up and spat out but you have been warned.

So without further ado, let me introduce you to the patient, as it came to me and after a good scrubbing...
Bosch Part Number 0 460 494 342

This photo is taken from the same side as you see when you stand in front of the vehicle and lift the bonnet.

Please note, it is actually desirable to leave the pulley/sprocket on the engine using a couple of cleverly placed holes to add bolts. Once the pulley is secured on the engine, just loosen the shaft nut a few turns and then give it or the shaft a firm tap with a rubber mallet to break the shaft free. Beware of there being a woodruff key in the shaft - hence the instruction to just loosen the nut first. Then undo the nut, pull the pump out and grab that key before it falls where man can't go.

Unread post by **CitroJim** » 24 Oct 2009, 19:26

That's a fully mechanical VP20 Mike, as fitted to the Pug 405 1.9TD and to the Xantia 1.9TD (amongst others) before the AS3 came along with the keypad, armour and electronic timing control. It has the electric cold advance system (you can see the electrovalve for this on the end of the light brown wire) that works in conjunction with glowplug post-heating.

13/16" is 21mm metric. It's one of those funny sizes like 3/4" (19mm) where the imperial is almost exactly the metric size.

Sadly, I know of no way to decode the Bosch part numbers.

Looking forward to the next instalments

MikeT · Unread post by **MikeT** » 24 Oct 2009, 19:37

CitroJim wrote:13/16" is 21mm metric.

Looking forward to the next instalments

Cheers Jim, updated accordingly. My to-hand socket set only goes up to 17MM in metric so I grabbed the largest imperial one and bingo.

EDIT: I've since learnt that the sixth and seventh number in the code (0 460 494 342) represents the plunger size and number of cylinders provided for. So this pump will have a 9mm plunger (the device that pressurises the metered fuel to each injector) feeding a 4-cylinder engine.

MikeT · Unread post by **MikeT** » 25 Oct 2009, 18:11

Now I've removed the pulley, I'm going to start at the rear of the pump. This is the business end that contains the distributor head with four outlet delivery valves - one per injector (which I've covered with whatever was at hand - blue, red caps, silver and black tape).

As per Jim's guide, I need to be mindful that there are parts inside the distributor head under strong spring tension and therefore allowing the head to come away from the body can allow parts enough room to move and drop out of position. Not really a problem if you're going to fully strip the pump as I will but still worth bearing in mind. Fortunately for some, it is possible to change the distributor head o-ring while the pump is still on the car (if access is possible and not barred by armouring!) but it has to be done very carefully and requires tedious and progressive bolt loosening/tightening sequences.

As such, if we look at how the bracketry is bolted on, we see that three of the four distributor head bolts (one each corner) needs to be removed to get the brackets off. The left side bracket (as we look at the pic) uses two (diagonally opposite) of the bolts and the smaller right bracket uses one of them.

Incidentally, there are several different configurations of brackets that I've seen to accomodate the different add-on units, connectors and control cables. If this were my Citroen pump, I'd also be facing an armoured covering protecting the immobiliser circuit as per Jim's guide. Thankfully, this pump doesn't have such an obstruction.

This is where the T30 bit comes in. I have a total of eight torx bolts to remove - yours may be more or less, dependant on bracket layout.

Click to enlarge

In the second picture we can now clearly see the distributor head (rusty looking block) and the four delivery valves - well only three came with this pump though I'm promised a replacement along with the shaft woodruff key that is also missing

I removed the right side bracket first as that only required one distributor head bolt to be removed. Note I had to shim the head bolts with nuts to make up for the lost thickness the bracket provided otherwise the bolts would not re-clamp the head fully on refitting as they will bottom out in the their thread.

By taking this approach I could ensure that at least two diagonally opposed bolts were keeping the head clamped at all times.

Also note the Stop Solenoid which is fitted in the top of the distributor head. This electrovalve uses a plunger seat and spring to block the fuel being delivered to the high pressure side of the pump - the plunger. When energised, it should lift the plunger allowing fuel to be pumped so a failing one can be the cause of intermittent starting problems.

Unread post by **CitroJim** » 25 Oct 2009, 20:06

Excellent stuff Mike. I like your presentation and attention to detail; first class

MikeT · Unread post by **MikeT** » 25 Oct 2009, 20:37

To Jim;
Thanks Jim, I'm driven by collective guides I've read so far but ideally, I'd like to add pointers and identifiers on the pictures. I just haven't found the time to investigate a suitable package that I can easily use yet.

To All;
While it may have not have been necessary to remove the brackets and refit the head bolts, I did so as I wanted to get a clearer view of the actual pump and for illustration purposes.

Likewise, it's probably not necessary to open the top of the LDA and remove it's inner parts but as this is a current topic in the Citroen section, I thought I might make a more useful contribution.

So here is the LDA or manifold-pressure compensation device or as some like to call it the flying saucer or UFO.

and from above

On the left picture, note the cutaway dimple in the lower half's mating area. This is to reference the position against a small punched dot on an inner part of the LDA which I will come back to in a later post showing the dot I'm referring to.

Along with the earlier mentioned missing parts, you may now have noticed in the last picture that there's a mixture of slotted screws and torx bolts fitted to this pump. On my other Xantia's these were all torx bolts, no screws to be seen, hence the mention of the screwdriver in the tools section. What you probably cannot see is the yellow paint marking the smoke screw and locknut position (centre of device) is broken, indicating this pump has been previously interfered with.

MikeT · Unread post by **MikeT** » 26 Oct 2009, 11:13

As stated in this thread http://www.frenchcarforum.co.uk/forum/v ... 5&start=15 and seen in the above posts picture, the top of the LDA has an adjustment screw with locknut known as the "smoke screw". It is one of many adjustments that can be made to fine tune the pump for best power and/or economy. If we take a look at the whole LDA assembly we can get a better idea of how it all works.

Once the four screws/bolts are removed we can lift the top off and we should find a rubber diaphragm clamped in place by two metal discs either side, held together by a nut and a special threaded rod (or rather a "pin" as Bosch call it) below the diaphragm. Note on the top metal disc the small dot I referred to earlier and the reference cutout/dimple on the lower body? It is roughly set 45 degrees clockwise.

If the diaphragm appears stuck, use a soft lever to prize it out

and then lift it upwards gently

If it resists coming out completely at about this point

that means the fuel enrichment pin has caught on a lip on the LDA pin and you'll have to gently rotate the diaphragm and tease it up and out - don't force it or you might break something, just be gentle and patient.

Here's the lid and the diaphragm assembly with fuel enrichment control pin fully removed. Note the small white collar on the control pin - it sometimes gets left in the LDA housing.

Now look at the lid closely and you will see the bottom of the smoke screw in the very centre. Also notice the manifold pressure inlet hole at the edge on the right and it's external spigot that connects to the intake.

The smoke screw is a pre-set for setting how high or low the control pin sits when at rest, held in place by it's return spring.

Which leads me to the last part we need to remove. Just lift out the spring (if it hasn't already fallen out).

MikeT · Unread post by **MikeT** » 26 Oct 2009, 11:39

The idea of the LDA is to enrichen and match the fuelling to any increase in manifold pressure that is created by the turbocharger. At low rpm, when the turbo isn't producing any meaningful pressure the diaphragm is at the mercy of the return spring which keeps it pushed up against the smoke screw stop in the lid. Therefore, the smoke screw becomes the enrichment pin's adjustable preset stop point when off-boost. As boost pressure builds, it flows into the lid of the LDA and pushes down on the diaphragm, against the spring tension and, with enough force, moves the pin down and away from the smoke screw stop. (Down for richer, up for leaner).

If we look at the bottom half of the LDA housing (still attached to the pump) we see the underside port which vents to atmosphere.

MikeT · Unread post by **MikeT** » 26 Oct 2009, 12:32

Let's take a closer look at this boost fuelling enrichment pin to better understand how the LDA works it's magic.

The part we're interested in is the bottom half where a coned taper has been machined, leaving the very end, about 4mm untouched. It is the coned taper that another pin rides on as the enrichment pin is pushed up and down by the LDA return spring vs manifold pressure. You can actually see a line on this cone's surface where the fuel pin has scribed it's mark over the years. This is a good indicator of exactly how the cone's "ramp" is being put to use.

The fuel delivery pin rides against this ramp pushing against it from the side (horizontally against the vertical enrichment cone) by the pump's governor mechanism inside the pump. As the diaphragm is pushed down, ergo the enrichment pin moves down with it, the side-on fuelling pin riding the ramp moves outwards to keep in contact, which in turn increases the maximum full load delivery in proportion to how far the fuelling pin moves outwards. The further out it extends, the more fuel is provided. As the boost pressure drops and the enrichment pin travels back up by the force of the return spring, the fuelling pin is pushed back inwards reducing the injected fuel quantity.

So, now we know what adjustments are available to us. We can set the off-boost fuelling point using the smoke screw. This affects the idle to low rpm range before boost has any effect on the LDA. More fuel allows the turbo to spool up quicker and improves low down torque.

The next adjustment we can make is to the return spring's pre-tension. The spring sits in a star wheel which can be rotated; clockwise moves the sping seat down, lowering the pre-tension while anti-clockwise brings the spring seat up, increasing pre-tension. This allows us a setpoint for the amount of boost required to start the control pin moving. Note: I have just recently learnt that Bosch "match" the spring to the pin as different applications require different pin profiles requiring different springs but we don't need to be concerned about that at this point.

I hope that's clear because there's one more aspect of this clever device we can adjust. Remember I mentioned the cutout dimple and the punched dot marks? Remember I said the diaphragm can be rotated? Well look closely at this picture of the cone. The cone is actually offset, concentric to the centre.

That gives us wide range of progressively more aggressive ramp choices because the further out the fuel pin has to move to contact the cone surface, the more fuel is injected. Using the shallowest ramp will give us the softest/least increase in fuel while rotating the enrichment pin so the deeper ramp is used will give us the strongest/most increase in fuel. Clever stuff! This LDA alone is one of the biggest reasons I'm a huge fan of these pumps - so many choices and all for free without needing any special tools or skills.

WARNING
If you make small adjustments one at a time and note the original position, you can, with time and patience, totally transform the performance of your diesel. For gentle tweaks, it's ok to use the smoke as an indicator of how much fuel you're pushing but if you're going to be pushing the limits as far as you can I would advise fitting both a boost gauge and an Exhaust Gas Temperature (EGT) gauge because more fuel creates more heat, enough to actually melt metal.

deian · Unread post by **deian** » 26 Oct 2009, 13:14

Is there more?

MikeT · Unread post by **MikeT** » 26 Oct 2009, 20:17

deian wrote:Is there more?

To the LDA? No, not that I can think of right now unless you want me to detail the "mods" that are possible.

As for the pump, I haven't begun yet - the LDA is simply "an add-on" device and just one of many.

For instance, there is something very similar to the LDA known as an ADA(?). So similar that unless you knew, you'd swear it was an LDA.

KP · Unread post by KP » 26 Oct 2009, 21:17

Can a TD Really generate that much heat?? I know of the heat issues for petrols, and been there myself, but i always thought TD's ran much cooler on the EGT side of things?

Really good write up Mike

Think if i ever get another TD i'll be playing around with a pump off hte engine a bit and seeing what can be done as only ever played with the offboost fuelling and a tiny amount of boost added on one i had

MikeT · Unread post by **MikeT** » 27 Oct 2009, 01:09

KP wrote:Can a TD Really generate that much heat?? I know of the heat issues for petrols, and been there myself, but i always thought TD's ran much cooler on the EGT side of things?

Have I witnessed it? No, but I hope to find out, hence the EGT probe fitted to my exhaust manifold. It is said that too much fuel and not enough air will see diesel EGT's rocket. The heat range possible is as wide as the fuel ratios a diesel can operate at

KP wrote:Really good write up Mike Think if i ever get another TD i'll be playing around with a pump off the engine a bit and seeing what can be done as only ever played with the offboost fuelling and a tiny amount of boost added on one i had

Thank you, it's good to know it's appreciated and please keep popping back, I'm learning more each day and I thought it couldn't get any better!!! These pumps have way too much to give apparently 8)

VertVega · Unread post by **VertVega** » 27 Oct 2009, 09:54

MikeT. Nice descriptions and very good pictures! I enjoyed reading eventhough I have a petrol Xantia

PS: Also I liked the disclaimer part

May I use it in my post ?

MikeT · Unread post by **MikeT** » 28 Oct 2009, 14:01

To VertVega I appreciate your comments, thank you. Please feel free to copy whatever you like.

To All I cut corners last night by not checking all my photos were in focus and as such I've had to "rewind" last evening and re-shoot the next stages.

Here, we're going to remove all that's necessary (and some probably not necessary) to get to the inner workings of this mechanical marvel. Namely, the fuel inlet and outlet banjos, accelerator, fuel cut-off and fast-idle lever assemblies as well as a few adjusting screws.

Starting with the fuel inlet and outlet parts, it's important to be aware they are not interchangeable. The outlet banjo bolt port is matched to the pressure valve in the vane pump and also contains a mesh filter whereas the intlet banjo has two large ports and no filter. Keep the parts grouped and clearly marked for re-assembly.

The outlet end

requires a 17mm socket

As does the intake banjo bolt

Obviously, the pump needs to be firmly clamped when undoing such fittings - I prefer a wooden workmate but whatever suits you should be fine - just be sure you clamp it where it won't be damaged.

With these parts removed, any fuel left inside the pump will escape more readily and in my case it wasn't a pleasant experience. The smell reminded me of used gloss paintbrushes sitting in white spirit so I'm guessing this pump was running home-brew WVO?