Hey don- this is what I gather from your first pic of the plunger (not the drawings). By the time the fill port is in the position you suggest in your last drawing, the port will no longer be fully exposed (or maybe not at all) to the helix to end injection. If you draw an immaginary line from the END of the helix (lowest portion) to the top of the plunger, that line goes almost exactly to the end of the bevel to the top of the protrusion. So to take full advantage of the advance provided by the protrusion, the helix would be rotated clear of the spill port and it would never spill into the helix.
-
TDR Magazine subscribers receive more than the magazine! You also gain additional forum privileges!
Details here: TDR Privileges
Subscribe to TDR Magazine here: https://www.tdr-online.com/
Engine/Transmission (1994 - 1998) Take your plate out!!!!!!!
- Thread starter Cummins Corvette
- Start Date
Attention: TDR Forum Junkies To the point: Click this link and check out the Front Page News story(ies) where we are tracking the introduction of the 2025 Ram HD trucks.
Thanks, TDR Staff
- Status
Yes you are correct. There is a point in which the rotation of the plunger would be too great and the helix would never uncover the spill/fill port. My drawing may be a tad too extreme. It is not scaled as I drew it quickly.
I have my old P&B in my hand now and just as you completely cover the spill/fill port with the entire protrusion the plunger helix will just barely dump or spill the fuel back.
Even a slight movement too far will cause problems.
Remember though the port closure will still be advanced some even if the plunger protrusion does not fully cover the spill/fill port.
It is not a ton of advance in moderate rack travel situations but it is still better than nothing at all or what the other pumps use.
Man, I feel better knowing you understand now what I tried to say
Hey Chris- What have you found out as far as the differences between your maxed out 160 pump and your maxed out 215 pump? Was the 913 worth it? Thanks
Thanks Don. This is the coolest p pump thread there has ever been. 
My question now is that it looks like the advance would also be in effect at idle or close to it. Idle should be the point at which the distance between the top of the plunger and the point directly below that on the helix is slightly greater than the height of the port. It looks like that point is still on top of the protrusion prior to dropping down into the groove.
illflem,
Thanks for the tip. I have three bosch pump books and a video as well.
The best part about the TDR is this stuff.
Ask someone a technical question and they have no idea how to respond on a technical level. Instead, people attack your word choice to try and make you look bad personally.
I refuse to let this thread spiral downhill. I refuse to let people spread false rumors because they don't have the technical background to figure it out themselves.
Don, you say I'm looking too closely. I say you're not looking close enough. It's in the details, man. You HAVE to look closer to understand. Yes, a protrusion would advance the timing. You are a smart person for understanding that. But what if the pump starts out on the protrusion and then falls off. Why can't you see that?
I'm sorry you felt like attacking my word choice instead of answering even ONE of my questions.
There's a reason for each one of the questions. I'm trying to lead this discussion to a much more technical level. But we can't just dive in all at once, because most people would be lost.
At a constant throttle setting, here's what happens in the governor. As RPM is pulled down, the flyweights are pushed in by the governor springs and rack travel is increased. That's the reason for the governor. It works in both directions. It increases fueling as rpm drops and decreases fueling as rpm increases.
I thought you could have figured that one out.
This is where I was going with that. When a truck is idling at let's say 700 rpm the throttle isn't moving. When the truck is cut off, the governor springs push the rack forward to increase fueling. So when you pull out a delivery valve and look at the relationship between the fill port and the top of the plunger, you have to understand that the plunger is in a position to delivery much more fuel than idle. Even still, my pump is not fully down off the advanced side of the "protrusion/groove. "
When the engine cranks, the plungers will rotate to deliver less fuel which is AWAY from the 'groove' and more up on the 'protrusion. ' My timing is therefore at its highest point while idling. As rack travel increases, I will then begin using the lower portions of the plunger.
I asked that question because this is what you will find when you take out a delivery valve. Maybe you would understand if you actually looked inside your pump.
If you don't understand what changes take place in the governor when the engine starts, it would be very easy to get yourself confused looking at a non moving engine.
I'm not going to explain each question in such great detail but I do want to comment on this.
You must have finally realized that a stock truck will never reach that advanced protrusion, but you can't understand why.
My pump uses that region to start. Just like you said the marine pumps do. The engine starts easier with retarded timing.
I'm fully aware that the fill port is stationary. You know that I paid money to have a shop rotate my fill ports around to use more of the available helix. I guess those comments were just ways of attacking me publicly?
Come on Don. Let's keep it technical.
Here's my picture to show how it works!
#ad
Notice that from the idle position as rack travel increases, timing gets retarded. Most trucks never reach the second 'slope' to get advance. But even if they did, they would be back at the timing they had at idle, with retarded timing in between.
Is that clear now?
-Chris
Thanks for the tip. I have three bosch pump books and a video as well.
The best part about the TDR is this stuff.
Ask someone a technical question and they have no idea how to respond on a technical level. Instead, people attack your word choice to try and make you look bad personally.
I refuse to let this thread spiral downhill. I refuse to let people spread false rumors because they don't have the technical background to figure it out themselves.
Don, you say I'm looking too closely. I say you're not looking close enough. It's in the details, man. You HAVE to look closer to understand. Yes, a protrusion would advance the timing. You are a smart person for understanding that. But what if the pump starts out on the protrusion and then falls off. Why can't you see that?
I'm sorry you felt like attacking my word choice instead of answering even ONE of my questions.
There's a reason for each one of the questions. I'm trying to lead this discussion to a much more technical level. But we can't just dive in all at once, because most people would be lost.
At a constant throttle setting, here's what happens in the governor. As RPM is pulled down, the flyweights are pushed in by the governor springs and rack travel is increased. That's the reason for the governor. It works in both directions. It increases fueling as rpm drops and decreases fueling as rpm increases.
I thought you could have figured that one out.
This is where I was going with that. When a truck is idling at let's say 700 rpm the throttle isn't moving. When the truck is cut off, the governor springs push the rack forward to increase fueling. So when you pull out a delivery valve and look at the relationship between the fill port and the top of the plunger, you have to understand that the plunger is in a position to delivery much more fuel than idle. Even still, my pump is not fully down off the advanced side of the "protrusion/groove. "
When the engine cranks, the plungers will rotate to deliver less fuel which is AWAY from the 'groove' and more up on the 'protrusion. ' My timing is therefore at its highest point while idling. As rack travel increases, I will then begin using the lower portions of the plunger.
I asked that question because this is what you will find when you take out a delivery valve. Maybe you would understand if you actually looked inside your pump.
If you don't understand what changes take place in the governor when the engine starts, it would be very easy to get yourself confused looking at a non moving engine.
I'm not going to explain each question in such great detail but I do want to comment on this.
You must have finally realized that a stock truck will never reach that advanced protrusion, but you can't understand why.
My pump uses that region to start. Just like you said the marine pumps do. The engine starts easier with retarded timing.
I'm fully aware that the fill port is stationary. You know that I paid money to have a shop rotate my fill ports around to use more of the available helix. I guess those comments were just ways of attacking me publicly?
Come on Don. Let's keep it technical.
Here's my picture to show how it works!
#adNotice that from the idle position as rack travel increases, timing gets retarded. Most trucks never reach the second 'slope' to get advance. But even if they did, they would be back at the timing they had at idle, with retarded timing in between.
Is that clear now?
-Chris
I think Don is right on the port being just bearly back on the advance protrusion and just BEARLY still dumping into the helix. Whoa that is a fine line! Chris is right in that it will never ever get even close to this point in a stock truck. That would be absolutely MAXIMUM FUELING. I think he is also right in that the timing would be fully advanced at idle too. That is if the port is small enough to be fully covered for a distance great enough to build the necessary pressure for injection before the plunger is rotated back off that protrusion.Chris Strickland,
Man I never wanted you to get uptight and I lost my temper slightly as well. What else is new?
I now see what you were trying to say. I also agree the timing will change with rack position and also know the governor will change the rack position. I have been into mine two times now.
The only portion we did not discuss is the total rotation of the barrels can be changed from more advance to less advance by twisting them in the pump housing. Many guys rotate them until they just stop spilling over. This will give an artificial advance as well and mine is able to completly cover the spill/fill port with the entire protrusion unlike your diagram/drawing shows.
Looks like it is the only thing we disagree on.
Don~
Man I never wanted you to get uptight and I lost my temper slightly as well. What else is new?
I now see what you were trying to say. I also agree the timing will change with rack position and also know the governor will change the rack position. I have been into mine two times now.
The only portion we did not discuss is the total rotation of the barrels can be changed from more advance to less advance by twisting them in the pump housing. Many guys rotate them until they just stop spilling over. This will give an artificial advance as well and mine is able to completly cover the spill/fill port with the entire protrusion unlike your diagram/drawing shows.
Looks like it is the only thing we disagree on.
Don~
Here is a pic of what I gather so far (be warned, it's crappy).
https://www.turbodieselregister.com/user_gallery/displayimage.php?&photoid=1391&width=3
The circle on the left represents the port position at full rack. The ones at the right represent port position at idle. I don't know the exact size of the port in relation to the plunger, thus the different size circles. If the port can be sealed by the plunger before it is "in the groove" (hehe), it will idle as Chris said, at full advance. But if the port is too big, it will need to be "in the groove" before it can inject any fuel and idle. Since Don has the plunger in his hand, which is it? Will it idle before it comes down off the protrusion? Does any one understand my crappy pic?
Oh ya, that thicker line is so you can see how I think things will line up at full rack. I think it will just BEARLY spill.
https://www.turbodieselregister.com/user_gallery/displayimage.php?&photoid=1391&width=3
The circle on the left represents the port position at full rack. The ones at the right represent port position at idle. I don't know the exact size of the port in relation to the plunger, thus the different size circles. If the port can be sealed by the plunger before it is "in the groove" (hehe), it will idle as Chris said, at full advance. But if the port is too big, it will need to be "in the groove" before it can inject any fuel and idle. Since Don has the plunger in his hand, which is it? Will it idle before it comes down off the protrusion? Does any one understand my crappy pic?
Oh ya, that thicker line is so you can see how I think things will line up at full rack. I think it will just BEARLY spill.
My barrels were rotated as you describe, but it doesn't just change the advance. It increases fueling over the entire range. Since the fill port has rotated about the plunger the pump now uses a wider portion of the helix at all rack positions. The idle set screw has to be backed nearly all the WAY down to get it to idle.
The amount of advance per cc of fuel delivered cannot change. It's built into the plunger. But if you can now use more of the helix, you also get to use a little more of the 'protrusion' to get your timing nearly back up to what it was at idle.
But while using that much of the helix, the fuel is injected too late to be useful. That's why my modified stop plug didn't help me even though it gave me an additional 2 mm of rack travel.
When I put my camplate in to limit fueling, I no longer get up to the protrusion and my timing is retarded from idle.
So, let's leave the maximum fueled pumps out of the equation.
On a stock or slightly modified pump, Is timing advanced or retarded as rack travel increases?
-Chris
The amount of advance per cc of fuel delivered cannot change. It's built into the plunger. But if you can now use more of the helix, you also get to use a little more of the 'protrusion' to get your timing nearly back up to what it was at idle.
But while using that much of the helix, the fuel is injected too late to be useful. That's why my modified stop plug didn't help me even though it gave me an additional 2 mm of rack travel.
When I put my camplate in to limit fueling, I no longer get up to the protrusion and my timing is retarded from idle.
So, let's leave the maximum fueled pumps out of the equation.
On a stock or slightly modified pump, Is timing advanced or retarded as rack travel increases?
-Chris
Given all the specifics you just mentioned, it will be retarded.
What about my earlier question? Is the 913 worth it?
I still think that at max rack on a stock truck that it would just bearly get into the groove, retarding the timing at full throttle for emissions reasons.
CS,
The timing can never be retarded lower than the static setting you have it at. The lowest part of the plunger is actually the top of it as I explain earlier and is indicated in the drawing I made up.
The plunger top does not have a retard groove cut into. The top of the plunger has two equally opposing raised areas or protrusions that advance the timing when rotated by the rack.
Since we measure the plunger lift from the center of the plunger retarded timing is impossible.
CA,
I dont know for sure if the engine will idle with advance or not. I do not know the relationship of the plunger and rack at idle speeds. Rather than guess I will wait until I know for sure.
Don~
The timing can never be retarded lower than the static setting you have it at. The lowest part of the plunger is actually the top of it as I explain earlier and is indicated in the drawing I made up.
The plunger top does not have a retard groove cut into. The top of the plunger has two equally opposing raised areas or protrusions that advance the timing when rotated by the rack.
Since we measure the plunger lift from the center of the plunger retarded timing is impossible.
CA,
I dont know for sure if the engine will idle with advance or not. I do not know the relationship of the plunger and rack at idle speeds. Rather than guess I will wait until I know for sure.
Don~
Last edited:
I'm confused on your word choice here.
If you find a plunger that is all the way DOWN on the base circle of the camshaft, then rotating the plunger doesn't cover up the fill port. How would it fill?
Maybe you are asking what portion of the plunger is directly below the fill/spill port.
With my pump, the fill port was on the incline going back up the slope to idle timing. It was NOT up on top. That's been my main argument this entire thread. My port lines up where I drew it on the picture I posted.
And I run more plunger to port rotation than most trucks.
-Chris
If you find a plunger that is all the way DOWN on the base circle of the camshaft, then rotating the plunger doesn't cover up the fill port. How would it fill?
Maybe you are asking what portion of the plunger is directly below the fill/spill port.
With my pump, the fill port was on the incline going back up the slope to idle timing. It was NOT up on top. That's been my main argument this entire thread. My port lines up where I drew it on the picture I posted.
And I run more plunger to port rotation than most trucks.
-Chris
Ok, so now we are getting somewhere
I understand that you are saying the spill/fill port on your pump is not completely covered with the protrusion at full rack travel or that it is maybe 50% covered at full rack with the plunger in its effective stroke or moving up in its barrel. In your case.
OTOH, Can you see what I say that the timing is never retarded at all, but is actually at the static timing you set it at? Since the timing is set from the lowest point on the plunger which happens to be the center, the plunger cant retard the timing. I was getting frustrated when everyone was saying the word "retarded"
I even tried to show a difference when I brought up the marine pump that does actually retard timing.
Don~
I understand that you are saying the spill/fill port on your pump is not completely covered with the protrusion at full rack travel or that it is maybe 50% covered at full rack with the plunger in its effective stroke or moving up in its barrel. In your case.
OTOH, Can you see what I say that the timing is never retarded at all, but is actually at the static timing you set it at? Since the timing is set from the lowest point on the plunger which happens to be the center, the plunger cant retard the timing. I was getting frustrated when everyone was saying the word "retarded"
I even tried to show a difference when I brought up the marine pump that does actually retard timing.
Don~
pump school
Chris you are doing a better job than I as I am unwilling to tear into my pump to just a look. I went to pump school about 20 years ago and it was only taught as a basic course. I think that is was a couple of 4 hour night classes. However I enjoy all of the education I am getting here.
Especially how to build a hot rod cummins. I enjoy watching and reading you guys build 600 plus engines. My goal is to just learn how to get the most bang for the buck and Not have the truck in pieces. LOL jimk
Chris you are doing a better job than I as I am unwilling to tear into my pump to just a look. I went to pump school about 20 years ago and it was only taught as a basic course. I think that is was a couple of 4 hour night classes. However I enjoy all of the education I am getting here.
Especially how to build a hot rod cummins. I enjoy watching and reading you guys build 600 plus engines. My goal is to just learn how to get the most bang for the buck and Not have the truck in pieces. LOL jimk
Don- the reason I was saying, "retard the timing" is because I think it uses the advance protrusion at idle. Therefore when it drops into the groove when the rack travels far enough, it is in affect being "retarded". It is just a different way of looking at what is happening.
Well Don,
I covered the timing procedure earlier as well, but you seem to be much more open minded and friendly now so I'll repeat.
It doesn't matter where the dial indicator touches on the plunger.
If you put a spacer above the plunger and set the dial indicator on that or even if you drilled down through the center of the plunger, you would get the same timing.
You know the procedure for timing. You find the rotation of the pump cam that puts the #1 plunger on the base circle. (at its lowest position). Then you zero the dial indicator. Then you rotate the pump forward until you get to the desired lift setting. Then rotate the engine until you have TDC #1, and tighten the pump gear.
So during the timing procedure we are just looking for a CHANGE in lift. It doesn't matter where the lift is measured from.
Lets discuss a stock truck. There is NO way the plunger rotates far enough to get to the second protrusion to advance the timing.
If the truck idles in the lower groove of the plunger, then timing is never changed throughout the rack movement. If the truck idles on the first protrusion then the timing is retarded (from idle) as rack increases. But there is NO WAY timing is ADVANCED from where it is at idle.
If you want to be right, just say that advance is built into the top of the plunger to advance timing under idle and low throttle positions, but that is taken away as rack travel increases. That way we can agree and don't have to use the word "retarded. "
-Chris
I covered the timing procedure earlier as well, but you seem to be much more open minded and friendly now so I'll repeat.
It doesn't matter where the dial indicator touches on the plunger.
If you put a spacer above the plunger and set the dial indicator on that or even if you drilled down through the center of the plunger, you would get the same timing.
You know the procedure for timing. You find the rotation of the pump cam that puts the #1 plunger on the base circle. (at its lowest position). Then you zero the dial indicator. Then you rotate the pump forward until you get to the desired lift setting. Then rotate the engine until you have TDC #1, and tighten the pump gear.
So during the timing procedure we are just looking for a CHANGE in lift. It doesn't matter where the lift is measured from.
Lets discuss a stock truck. There is NO way the plunger rotates far enough to get to the second protrusion to advance the timing.
If the truck idles in the lower groove of the plunger, then timing is never changed throughout the rack movement. If the truck idles on the first protrusion then the timing is retarded (from idle) as rack increases. But there is NO WAY timing is ADVANCED from where it is at idle.
If you want to be right, just say that advance is built into the top of the plunger to advance timing under idle and low throttle positions, but that is taken away as rack travel increases. That way we can agree and don't have to use the word "retarded. "
-Chris
Don- Could you PLEEEEEEEEEEEEEESE do me a huge favor???? GOOD!!! Put up a picture of the plunger looking square at the side with the bottom of the helix (full fueling side) about 2/3 the way to the left? Basically the exact same picture you already put up but looking square at the side of the plunger. THANKS A BUNCH!!
Chris Oo.
Chris Oo.
- Status
Issue 128 – Digital Version
Digital Magazines
FREE!
TDR Test Drive - Digital Edition
Renew
Subscribe
Gift Subscriptions
Back Issues
Subscription Status
Address Change Form
Buyer's Guides
Ram Diagnostic Trouble Codes
The Perfect Collection
The Perfect Collection Vol. II
TSB Updates
Dodge/Cummins Historical Overview
Cameron Collection
What Makes Us Tick?
Product Showcase
Advertising
Turbo Diesel Register
Issue 128 – Digital Version
Digital Magazines
FREE!
TDR Test Drive - Digital Edition
Renew
Subscribe
Gift Subscriptions
Back Issues
Subscription Status
Address Change Form
Buyer's Guides
Ram Diagnostic Trouble Codes
The Perfect Collection
The Perfect Collection Vol. II
TSB Updates
Dodge/Cummins Historical Overview
Cameron Collection
What Makes Us Tick?
Product Showcase
Advertising
