06-12-2011, 01:23 PM
Guide: Bosch pump setup and tuning
Before you go fiddling with your Bosch fuel pump its a good idea to read this guide and understand what the main parts of the pump do, why you would want to change them and what effects changing them will have on your engine. Most of the information in this guide can be found from other sources on the web but im hoping to have the bulk of the important stuff all here together, making it easier to read and learn about the pump.
Firstly, make yourself familiar with the main parts of the pump and understand what does what while your driving. See the photos below for a general guide.
![[Image: edit1.png]](http://i789.photobucket.com/albums/yy175/DanHargrave/edit1.png)
![[Image: boschmaxfuel.png]](http://i789.photobucket.com/albums/yy175/DanHargrave/boschmaxfuel.png)
![[Image: boschedit1.png]](http://i789.photobucket.com/albums/yy175/DanHargrave/boschedit1.png)
![[Image: edit2.jpg]](http://i789.photobucket.com/albums/yy175/DanHargrave/edit2.jpg)
Now you where everything is and whats its for youâ??ll want to know how to adjust certain things and understand what adjusting them does. Below are numbered sections with an explanation in each for specific adjustments.
1. Adjusting your idle
2. Adjusting the throttle arm
3. Adjusting the fuel screw
4. Adjusting the injection timing
5. LDA Modications
6. 11mm and gov-mod guide
1. Idle
The ideal hot idle would be between 800-900rpm and cold idle between 1000/1100rpm. If you locate the hot and cold idle screws you should be able to see a pivoting arm between the two of them and a cable attached to this, which goes to the wax stat. The wax stat will pull the cable in when the engine temperature is low and this will then pull the pivoting arm to the right (You should be able to move the arm from left to right with your fingers when the engine is hot).
When the pivoting arm is not under tension (Hot engine) it will rest to the left. If you look at how the arm operates you will see it has 2 prongs which rest on the bottom of either the left or right idle screws. When hot it rests against the screw on the right and when cold it rests against the screw on the left. By winding these screws in or out we can change the resting point of the arm and therefore the idle.
Hot idle adjustment - Left hand side screw, slacken the 10mm locknut and wind the screw in (clockwise) to increase the idle speed and out (anti-clockwise) to lower the idle speed. Once correct speed is achieved re-tighten locknut.
Cold idle adjustment â?? Right hand side screw, slacken the 10mm locknut and wind the screw in (clockwise) to lower the idle speed and out (anti-clockwise) to increase the idle speed. Once correct speed is achieved re-tighten locknut.
Also, remember that you can adjust the cold idle speed even when the engine is hot by pushing the pivoting arm to the right and holding it there while you adjust the screw.
2. Throttle arm
The throttle arm is connected to the throttle cable (and that connected to the accelerator pedal) and also the throttle shaft. When the cable is pulled the arm rotates and twists the throttle shaft, which in turn moves the governor shaft and leverset inside the pump and increases the fuelling/engine speed. The throttle arm rests at idle on a screw found at the back of the pump and at full throttle it rotates anti-clockwise until it reaches the max travel limit screw on the front of the pump.
The throttle rest screw can be adjusted by slackening the 10mm locknut and winding in to raise engine speed, or wound out to reduce engine speed. This should only be used to reduce the idle when you cannot get the idle low enough by adjusting the idle screws. Past a certain point it will not reduce engine speed any more. At this point, you could remove the throttle arm from the throttle shaft (Explained in detail in the gov-mod guide) and move the throttle arm anti-clockwise 1 spline on the splined shaft. However this will mean you will lose 1 spline of throttle arm travel at maximum throttle. Some people would chose to combat this by grinding the part of the throttle arm that touches the throttle rest (Will let the arm sit further back) or grinding the other end of the throttle arm which touches the max throttle stop, to gain back the throttle arm travel lost when rotating the arm on the shaft. Both of these are fine to do as long as you are careful and donâ??t get silly with the grinding.
The max travel limit screw is usually just removed when tuning the pump to let the engine rev a little higher and inject slightly more fuel. If you remove the throttle stop screw the throttle arm will just contact the pump body at full throttle. You can grind off the part of the throttle arm that touches the pump body for slightly more arm travel.
3. Fuel screw
The fuel screw (Located on the right side of the pump) controls the injection length. By turning this screw in you will increase the length of time the pump injects fuel per stroke, and thus end up with more fuel, or smoke. Increasing the injection length will cause the fuel to burn at a hotter temperature and means you get less efficient combustion.
However, it is the simplest way of increasing the fuel and as long as you donâ??t go mad it wont have a noticeable impact on efficiency. At a certain point, usually after turning it in around 6 full turns from stock, it will cause the idle to rise to ~3000rpm. When this happens the fuelling limit for a â??stockâ?? pump is almost reached. You will need to turn the fuel screw back out marginally until the idle drops back down and claw back a little extra fuel elsewhere. The only other simple mod you can do to increasing fuelling from here is an LDA rotate/grind.
4. Timing adjustment
The pumps timing is controlled by the cambelt and controls when the fuel is injected. You can adjust the pumps timing slightly without removing or even touching the cambelt, but instead by loosening the bolts that hold the pump to the pump bracket and rotating the pump back or forwards. The bolts that hold the pump to the bracket are shown as best as possible in the below photos:
![[Image: edit3.png]](http://i789.photobucket.com/albums/yy175/DanHargrave/edit3.png)
![[Image: boschbracket.jpg]](http://i789.photobucket.com/albums/yy175/DanHargrave/boschbracket.jpg)
There are 3 bolts on the left, one at the front of the pump, one at the back of the pump and one under the pump. (The pump bracket photo helps you see where on the bracket the bolts are located) The top 2 are easy enough to get to but to reach the bottom one you may need to remove the alternator or cut a 13mm spanner in half, it can be quite fiddly. The one on the right is at the bottom under/behind the 4 metal injector lines. In the photo abovve you cannot actually see the bottom 2 bolts, but the arrows indicate where they are located. You also cannot see the rear left bolt, but it is easy enough to see when you look.
You may also want to slacken the 4 17mm union nuts on the metal injector lines (at the pump end, NOT the injector ends) as these sometimes make rotating the pump hard. Once all bolts are slackened, you should be able to hold the top of the pump and push/pull it into position. As a general rule the pump usually runs best between 2/3rds and ¾â??s ADVANCED, but you may need to adjust it a bit more/less depending on your engine. It is also possible to adjust the timing while the engine is running, but make sure you are holding the pump steady while somebody else starts the engine and do not let go of the pump until the bracket bolts are tightened up again.
Note, many people do not bother to tighten the bottom left bolt back up, so that any future adjustments donâ??t involve having to struggle at loosening it again. From my own experience I donâ??t see any problem leaving it loose or removing it as long at the other 3 bolts are tight. However you do this at your own risk.
5. LDA Modifications
Please see my seperate guide for LDA tuning here - BOSCH VE GUIDES - LDA modifications.
6. 11mm and gov-mod guide
And also see Londondan's guide for 11mm and gov-mod here - BOSCH VE GUIDES - 11mm Hybrid Bosch Pump + Gov Mod
Before you go fiddling with your Bosch fuel pump its a good idea to read this guide and understand what the main parts of the pump do, why you would want to change them and what effects changing them will have on your engine. Most of the information in this guide can be found from other sources on the web but im hoping to have the bulk of the important stuff all here together, making it easier to read and learn about the pump.
Firstly, make yourself familiar with the main parts of the pump and understand what does what while your driving. See the photos below for a general guide.
Now you where everything is and whats its for youâ??ll want to know how to adjust certain things and understand what adjusting them does. Below are numbered sections with an explanation in each for specific adjustments.
1. Adjusting your idle
2. Adjusting the throttle arm
3. Adjusting the fuel screw
4. Adjusting the injection timing
5. LDA Modications
6. 11mm and gov-mod guide
1. Idle
The ideal hot idle would be between 800-900rpm and cold idle between 1000/1100rpm. If you locate the hot and cold idle screws you should be able to see a pivoting arm between the two of them and a cable attached to this, which goes to the wax stat. The wax stat will pull the cable in when the engine temperature is low and this will then pull the pivoting arm to the right (You should be able to move the arm from left to right with your fingers when the engine is hot).
When the pivoting arm is not under tension (Hot engine) it will rest to the left. If you look at how the arm operates you will see it has 2 prongs which rest on the bottom of either the left or right idle screws. When hot it rests against the screw on the right and when cold it rests against the screw on the left. By winding these screws in or out we can change the resting point of the arm and therefore the idle.
Hot idle adjustment - Left hand side screw, slacken the 10mm locknut and wind the screw in (clockwise) to increase the idle speed and out (anti-clockwise) to lower the idle speed. Once correct speed is achieved re-tighten locknut.
Cold idle adjustment â?? Right hand side screw, slacken the 10mm locknut and wind the screw in (clockwise) to lower the idle speed and out (anti-clockwise) to increase the idle speed. Once correct speed is achieved re-tighten locknut.
Also, remember that you can adjust the cold idle speed even when the engine is hot by pushing the pivoting arm to the right and holding it there while you adjust the screw.
2. Throttle arm
The throttle arm is connected to the throttle cable (and that connected to the accelerator pedal) and also the throttle shaft. When the cable is pulled the arm rotates and twists the throttle shaft, which in turn moves the governor shaft and leverset inside the pump and increases the fuelling/engine speed. The throttle arm rests at idle on a screw found at the back of the pump and at full throttle it rotates anti-clockwise until it reaches the max travel limit screw on the front of the pump.
The throttle rest screw can be adjusted by slackening the 10mm locknut and winding in to raise engine speed, or wound out to reduce engine speed. This should only be used to reduce the idle when you cannot get the idle low enough by adjusting the idle screws. Past a certain point it will not reduce engine speed any more. At this point, you could remove the throttle arm from the throttle shaft (Explained in detail in the gov-mod guide) and move the throttle arm anti-clockwise 1 spline on the splined shaft. However this will mean you will lose 1 spline of throttle arm travel at maximum throttle. Some people would chose to combat this by grinding the part of the throttle arm that touches the throttle rest (Will let the arm sit further back) or grinding the other end of the throttle arm which touches the max throttle stop, to gain back the throttle arm travel lost when rotating the arm on the shaft. Both of these are fine to do as long as you are careful and donâ??t get silly with the grinding.
The max travel limit screw is usually just removed when tuning the pump to let the engine rev a little higher and inject slightly more fuel. If you remove the throttle stop screw the throttle arm will just contact the pump body at full throttle. You can grind off the part of the throttle arm that touches the pump body for slightly more arm travel.
3. Fuel screw
The fuel screw (Located on the right side of the pump) controls the injection length. By turning this screw in you will increase the length of time the pump injects fuel per stroke, and thus end up with more fuel, or smoke. Increasing the injection length will cause the fuel to burn at a hotter temperature and means you get less efficient combustion.
However, it is the simplest way of increasing the fuel and as long as you donâ??t go mad it wont have a noticeable impact on efficiency. At a certain point, usually after turning it in around 6 full turns from stock, it will cause the idle to rise to ~3000rpm. When this happens the fuelling limit for a â??stockâ?? pump is almost reached. You will need to turn the fuel screw back out marginally until the idle drops back down and claw back a little extra fuel elsewhere. The only other simple mod you can do to increasing fuelling from here is an LDA rotate/grind.
4. Timing adjustment
The pumps timing is controlled by the cambelt and controls when the fuel is injected. You can adjust the pumps timing slightly without removing or even touching the cambelt, but instead by loosening the bolts that hold the pump to the pump bracket and rotating the pump back or forwards. The bolts that hold the pump to the bracket are shown as best as possible in the below photos:
There are 3 bolts on the left, one at the front of the pump, one at the back of the pump and one under the pump. (The pump bracket photo helps you see where on the bracket the bolts are located) The top 2 are easy enough to get to but to reach the bottom one you may need to remove the alternator or cut a 13mm spanner in half, it can be quite fiddly. The one on the right is at the bottom under/behind the 4 metal injector lines. In the photo abovve you cannot actually see the bottom 2 bolts, but the arrows indicate where they are located. You also cannot see the rear left bolt, but it is easy enough to see when you look.
You may also want to slacken the 4 17mm union nuts on the metal injector lines (at the pump end, NOT the injector ends) as these sometimes make rotating the pump hard. Once all bolts are slackened, you should be able to hold the top of the pump and push/pull it into position. As a general rule the pump usually runs best between 2/3rds and ¾â??s ADVANCED, but you may need to adjust it a bit more/less depending on your engine. It is also possible to adjust the timing while the engine is running, but make sure you are holding the pump steady while somebody else starts the engine and do not let go of the pump until the bracket bolts are tightened up again.
Note, many people do not bother to tighten the bottom left bolt back up, so that any future adjustments donâ??t involve having to struggle at loosening it again. From my own experience I donâ??t see any problem leaving it loose or removing it as long at the other 3 bolts are tight. However you do this at your own risk.
5. LDA Modifications
Please see my seperate guide for LDA tuning here - BOSCH VE GUIDES - LDA modifications.
6. 11mm and gov-mod guide
And also see Londondan's guide for 11mm and gov-mod here - BOSCH VE GUIDES - 11mm Hybrid Bosch Pump + Gov Mod
tell you what, I will get my coat...........![[Image: DSCF1804.jpg]](http://i1128.photobucket.com/albums/m481/martypellowe/DSCF1804.jpg)
![[Image: DSCF1805.jpg]](http://i1128.photobucket.com/albums/m481/martypellowe/DSCF1805.jpg)
![[Image: DSCF1807.jpg]](http://i1128.photobucket.com/albums/m481/martypellowe/DSCF1807.jpg)