P7100 Timing

[Joe G.]

Don,



The way these injector pumps work is kind of interesting. The timing is set by loosening the large gear at the top in the picture and rotating it to a different position. I've never had a P7100 pump apart so I may be wrong on some of the details. I have had an Bosche pump for a WWII marine Buda diesel apart (I had a couple of spares) to replace a delivery valve and some of the parts for that cylinder. That pump is some sort of remote ancestor of our pumps. The basic structure is that the delivery valve is a precision check valve to maintain pressure in the lines between injections. The pump plunger is forced upward by the lobe on the pump camshaft. Injection occurs when the resistance to pressure in the injector nossle is overcome. The point at which this occurs is always the same in relation to the rotation of the crankshaft. What the throttle controls is the point at which injection STOPS. The pump plunger moves inside a sleeve that is inside the plunger barrel. The plunger has a groove in it's side. The sleeve has a spiral shaped slot in the side. Rotation of the sleeve within the slot is done by the throttle rack. As the plunger rises it will reach a point at which the groove in the plunger uncovers the slot in the sleeve. At this point pressure drops and injection stops. Pretty simple concept, but the clearances for the parts involved are very critical.



From this you can see how a leaking injector is a problem. First of all it probably has a poor spray pattern so the fuel does not ignite properly. Timing for the start of injection is fouled up because the pressure in the injection line has dropped because of the leak so that cylinder is out of time.



The governors in our pumps are a LOT more complicated than the one on my old Buda marine diesel.



As I said above I may not have all the details right as far as our pumps are concerned, but I thought you might be interested in the general scheme about how they work.

 

[Reddog1]

Joe George – How would you know if you had the original pump if you did not buy the truck new? Can't just throw the charts away, darn, it could have made it easier. I still do not understand why it is the engine (not the pump) that determines the timing, if the pump cam profile, plungers, and delivery valves are the different in the pumps?





Don M – Don’t leave me cause you learned something too. Everything you said pretty much makes sense to me. Can you be more specific as to which testing you are referring to. It is still not clear to me as how can I tell if I have set the timing too far advanced or retarded, until after the damage?



I went back to Joseph Donnelly’s post, I think understand a little more.



Let’s see if this is correct:



Heavy pull (trailer, etc. ) stay low on timing.



No pulling (empty, flat land, etc. ) up on timing



Increase MPG, up on timing.







Wayne

P. S. Joe our post hit about the same time. I appreciate knowing the basiics on how to pump works. It was going to be my next question.

 

[Joe G.]

Wayne,



Unless the previous owner(s) had plenty of money the one on it is the original. There must be a part number on it somewhere so you can check. I've never heard that question asked.

 

[Reddog1]

Joe,



Leave it to me to be the only one to ask. I must admit, I wear a belt with my suspenders.



Actually, I have been told the previous owner did have a lot of money. I bought the Ram from an estate. The question was more out of curiosity than anything else.





Wayne

 

[Don M]

Wayne,



Im not going anywhere. I actually knew what Joe was speaking of. I just somehow forgot they were independent pieces.

I was thinking of degreeing a cam for a gasser and distributors being the same idea as the pump and just got all twisted up.



Now I know whats up. I think I knew before.

Of course they are seperate. The cam gear does not get pulled to set the injection pump timing the injector pump gear gets pulled.

I get the bozo award today and i seem to win that award too many times. hehehe!



The testing I was referring to was dyno runs. seat of the pants feel, and listening for the louder knock or hammering sounds associated with increased timing.

NOX levels increase too.



What kinda stuff do you want to do to the truck, what kinda HP are you looking for?



Don~

 

[Reddog1]

Don M



I have not decided what I want to do to the truck or what HP I want. The first thing I want to do is understand the truck, and be able to make a somewhat intelligent decision as to what mods to go with. I fully intend on asking for input on the mods, but ultimately, I will have to separate the wheat from the shaft. HP wise, I am considering 300 to 350 HP, maybe more or maybe less, depending on the cost and/or compromises.



It is obvious to me; many TDR members have a good idea why they are making mods, and what the mods do. Unfortunately, many only go with the mods because they sound cool. I think it is great that so many people share the results of mods they have made, even though they do not fully understand.



This thread is about timing on the P7100. I am little amused as to how few contribute their experiences relating to this subject. I may stand corrected, but at this point it is my belief that better running trucks with more MPG could be the result of more attention to timing.



I am building a wish list of BOMB parts, and gathering data on them. With the help of you guys, I hope to get it right the first time. Santa will finish off the gauges. March or April, I expect the DTT transmission. After that, wish list of BOMB parts.





Wayne



P. S. The bozo award should be reserved for those who read the various post and become an expert or spend a lot of money without questions or comments.

 

[Jeff H]

If you are not sure what pump you have or think you have one that you think is not the original. You may want to contact Bosch. TDR has a link set up.