I've been working on this for the last few months, it was going to go on my website in the article section, however as my site is down I might as well post it here for now. I haven't had time to proof it too much, but it'll get us started. I am open to suggestions, but would rather it not be torn apart as there are always going to be arguments from one side or the other. This is MY experience over the last few years....
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All about Injection Pumps
As a parts vendor I get a lot of calls about injection pumps. I’ve sold in the neighborhood of 200 pumps over the years! Because of this I think that it’s a good time to do a little education about how they work, and how one can prolong or shorten the life of their pump. All the pumps I sell come either direct from VW, or from the only licensed Bosch rebuilder in North America. As one of their main distributors we see a lot of pump traffic and have knowledge about life expectancy as well as the usual problems.
To be a licensed Bosch rebuilder you have to do everything that Bosch would do direct—they are one in the same. You need millions of dollars worth of test equipment and a lot of education as well as a proven track record. When a pump is rebuilt, everything is gone over; if something is wrong they replace it. Many rebuilders cut corners by not replacing the mandatory parts, such as the temp sensors, center head plug, transfer pump, all the overhaul gaskets and the transfer pump regulator. These parts add up in cost, but it’s a lot better than having a job half done to save a few bucks only to have a problem down the road. I have never had a problem with any of the pumps I have received from either of my sources.
How does a pump work?
This paragraph borrowed from Drivbiwire:
Inside the TDI injection pump there is a "Cam Plate" that is turned by the pumps timing belt pulley. The cam plate is also turning a small "Plunger", these two assemblies rotate in unison. The rotating plunger is mounted to a stationary plate or "Roller Ring" that has four rollers that provide the contours for the spinning cam plate to follow and cause the plunger to extend in and out on. The cam plate contours are what determines how far the plunger slides in and out of the fuel compression chamber and the size of the contours are what can vary from year to year effectively determining how high the fuel pressures can reach. Since the roller ring assembly (fig 2) is "mostly" stationary the compression of the small amounts of fuel can occur at exactly the same time. The caveat to this is that the roller ring assembly can be rotated slightly clockwise or counter clockwise effectively adjusting when the compression of the fuel actually occurs without having to integrate a complex system for injection timing. The looming question is how do you control the quantity of fuel ie speed of the motor? The above describes how you effectively create fuel pressure and adjust timing but the next key is the "Fuel Collar" (Fig 7). The fuel collar is a simple ring that the plunger slides through during each and every injection stroke. In the plunger there is an elongated hole (figure 5, top) that when uncovered allows all remaining fuel in the compression chamber to be vented back into the internal body of the pump effectively ending the fuel delivery for that cylinder. This means that all unused fuel is simply vented internally without having to flow to and from each injector. The injectors ONLY receive what is needed and the fuel collar is what directly determines engine speed and power output.
How does a pump fail?
There are many reasons a pump can fail, the most common is a seal going bad. When this happens the pump will spring a leak. If you have a puddle of fuel after having your car sit overnight you should look at your pump first!
The next most common is general wear and tear; the quantity adjuster goes out, fuel temp sensor goes out, or the plunger starts to wear out. In these cases you’ll have either a code (quantity adjuster upper limit reached (code P1562 on an A4 ALH or 01268 on an A3/B4). The quantity adjuster is a motor in the pump that with the eccentric shaft adjusts fuel and responds to the throttle sending unit.
Plunger failure: The driveshaft turns the cam, between that there is a cam cross. These are hardened chrome pieces which start to wear out over time. The clearances start to get out of spec. As this happens the pump starts to make a lot more noise or clatter--all this does is show is that there has been a lot of wear and the parts are now out of operating tolerances. If the plunger is going out then what was a smooth running pump will turn into a very loud “clacking” noise. It almost sounds as loud as the engine itself (put your ear by it). When you’re heard it you know what it sounds like! More along the lines of the classic marbles in a tin can sound... In these cases change the pump out ASAP as it will keep running until it seizes. Changing it earlier might save the pump core.
Another problem is when the plunger seizes. The tolerances are down to 4 millionths of an inch (air miked) between the pump head and rotor. They need enough room for fuel to move through it; when there is excessive plunger clearance then you start to have low cranking delivery, also known as hard starting. This is where biodiesel starts to come into play. Bio or veggie oil has lots of lubricity, but veggie oils have particles/water/glycerin which does NOT have lubrication properties, this in turn will cause extra wear on your pump plunger and rotor. Also if your bio has particles, water or glycerin then the same problem happens....
Center head plugs are a one torque item. This has a sharp edge on it which allows it to seal as it's torqued. If you don't replace this plug then often it doesn't torque and seal right, which causes low cranking delivery (again, hard starting).
Transfer pump is a vane style pump. The driveshaft turns the pump, the blades centrifugally "fly out," or spread, and start picking up fuel....
Rollers are what rides on the hardened cam lobes. The cam lobes gives the plunger the lift it needs to operate. If you have low lubricity fuel, or biofueles then you'll see these hardened chrome pieces are pitted.
Perhaps the high pH levels of the biofuels cause the etching of the chrome pieces. Regardless, biofuel useage is a contributing cause to this failure.
The quantity adjuster, or positioner, is the brain of the pump. This takes information from starting, to low idle, high idle, etc... This part is electrical, in the past with the IDIs it was mechanical. If the quantity adjuster starts to go out then your revs can go all over the place. Often they get sticky from veggie oil. They can rust out too with poor quality fuel.
Temp sensor is a always replace item on a proper rebuild. It causes CELs if it goes bad.
Output delivery valves are on the ends of the head, they are what you hook your fuel line up to (also known as fuel delivery valve holder nut. There is a spring and a gasket in there). This part stops fuel from going back up in the head after ignition as taken place. Some people put aftermarket delivery valves in hoping that they can get more fueling. There are better ways to get higher transfer pump pressures (like tuning!).
What is the Life Expectancy of a pump?
We’ll get to that in a bit. Just like a turbo, injection pumps are wear items. They are constantly rotating and do wear out over time, but there are many things one can do to help increase the life of a pump.
Hard conditions: The transfer pump is a vane style pump—when you have a lot of power modifications and don’t upgrade to support your increased fueling, or if you raise the advance too far, then you can overwork the pump. Also, if you have fuel starvation from running out because you tried to get that last mile for your fuel distance marathons (you know who you are!) then you’re abusing the pump. Pumps do not like to run dry, just like anything that requires constant lubrication!
Normal Use conditions: First me must define what is normal use? Normal use is what the pump was designed for. Bosch built this pump to run on well lubricated diesel fuel. Just like the engine for efficient combustion requires cetane of at least 49, the pump needs fuel that is well lubed. Many truck stops (or any cheap diesel location) carry fuel with a cetane rating of 40 and no additives in addition to the required ones as the refinery. If you have a technician at the refinery that fails to put in the correct amount of additive then you could effectively be putting sand paper through your pump. It can literally wear out completely in one tank of fuel…or less. IF you are fueling at these locations, ALWAYS use an additive such as Powerservice, Redline 85+, or Stanadyne. I always fuel at either Chevron when I’m out west, or at BP/AMOCO in the Midwest/East or Sunoco when I’m in Canada. All of these companies have high cetane, which the engine loves, and all have aggressive additives to protect your injection pump. These are the only non biodiesel fuel stations I’ll go to and not add an additive. Your other option is to run biodiesel, but that opens a whole new can of worms…
If you are running biodiesel expect to have to change your pump sooner. If you run a small blend (B5-B20) DO NOT switch between Biodiesel and regular diesel as this will kill your seals. (Biodiesel causes the pump seals to swell; regular diesel causes them to shrink—when you switch back and forth you’re asking for a seal to fail). Also be sure to change your fuel filter more often; if you’re running home brew biodiesel run a 2 micron fuel filter. Water is a huge enemy to pumps. If you have water in the fuel then your pump will rust out from the inside. Don’t expect a core refund in this case! The most common pump failure for biodiesel users though is a bad seal. This is why everyone on tdiclub.com says to get a seal kit and replace the seals. This is potentially the worst mistake you can make!
My Pump sprung a leak, so all I need is a seal kit right?
WRONG! Time and time again we see pumps that come in where the customer tried to do their own pump head and o-ring job. When they do this job themselves they put the studs in (and let the head slide out); often they inadvertently let it slide out too far, which causes the main springs to drop. Not knowing any better they faithfully put the pump back together and button up everything. The instant they start the car the head and rotors snap, which causes the shaft to seize up and thereby completely junks the pump. You might as well use it as a trophy as it is now completely worthless! I should add that there are many that do know how to change the seals, and have done so with success. However, they are not capable of changing out the transfer pump regulator or the center head plug, often they don’t change out the temp sensor, and they are certainly not able to calibrate everything when they are done. Biodiesel use shortens the life of your pump; that much is certain. If you just replace the seals then down the line you’re still looking a full rebuild eventually. I should also add that some people don’t replace all the seals either, which is not good as any leak will find its way through the weakest seal when the pressure builds up in the pump. This pressure is between 90 and 100 PSI.
Tell me more about Biodiesel and veggie oil…
Biodiesel will shorten the life of the pump, that much is certain. If you have proper filtration, good quality biodiesel, and don’t switch back and forth with regular diesel you should get a good 120-150,000 miles out of a pump. Often biodiesel pumps are good cores and have no problems with rebuilds. The exception is the home brewers that don’t get all the water out which rusts the pump out from the inside.
Grease/veggie oil gums pump the pump. When you open it up it looks like syrup in there. The positioner sticks, as do the sliding sleeves which all combined contribute to the pump failure. Because of that anyone who runs veggie oil can count on a core being completely junked. Sometimes in rare cases they are ok, but this is the exception and not the rule. In my experience most people have their veggie oil pumps fail at 60-80,000 miles. Some have gone more than twice that, but they are very particular about how they use their veggie oil. Remember we’re talking about my average experience over a good 200+ rebuilds over the years.
So in conclusion, if you have proper filtration, don’t have water going through the system, don’t run biodiesel or grease, and run a properly lubricated pump then your pump should last indefinitely. I have customers with over 500,000 miles on the original pump. I’ve heard of a couple older A3/B4 pumps that lasted over 700,000 miles. However, in my experience most A3/B4 pumps last about 200,000-250,000 miles before needing a rebuild. Most A4 ALH pumps last about 175,000-200,000 miles before needing a rebuild. Watch for the symptoms of a bad pump, and then take care of it soon to avoid a good core from being turned into a junk core. If you’re close to a timing belt change you might as well do that at the same time too.
I hope that this article has helped, and I hope your injection pump will last you a long time.
-BB
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