Lucas CAV rotary injection pump math

   / Lucas CAV rotary injection pump math #11  
Look at the liner for scratches..
Yes, I was talking about by-passing the return connector, just like you described..
BE CAREFUL w/ piggy backing an electric lift pump.. IF the pressure is to great, the check ball seats in the UP position, actually blocking OFF the return fuel.. causing extreme internal pressure & blowing out the front seals.. THEN you have 20 gallons of diesel fuel in the OIL..
Seen it happen MORE THAN once.. THATS WHY I said, the check ball return on a DPA is more trouble than its worth..
I've seen it happen w/ just trash in the pump.. & I've seen it on the test stand after a rebuild..[faulty connector]
 
   / Lucas CAV rotary injection pump math
  • Thread Starter
#12  
Thanks for all your advice. The liner had no scratches, installed new liner and blades but to no avail. Well at least I know that's not where it's at.

Also ended the day with a test with the check ball removed which supposedly causes dynamic advance to FAIL. No difference, ball left removed on subsequent runs to prevent any dynamic resurrection from stepping on the already raised static advance.

Finally, I advanced at the gear level by 2 teeth and this in combination with full housing advance gave about 15 degrees of static advance. This resulted in hesitation begining around 1800rpm, a very far cry from "Letter-B" timing so I'd postulate that dynamic timing just ISN'T taking place. I don't dare to advance any more because I have no clue as to how much total advance there is supposed to be at let's say 2500 rpm (5 static +?).

see the rearranged 6 test run videos @ the bottom of

http://trixtar.org/3/tinkerings/12valve208hp/index.html

By then I got tired and called it quits. For tomorrow I think I'll put the gear back to standard tooth, remove the pump again and maybe look for another suspect.

The Cummins manual says that 2 kinds of lift pumps are used, a diaphragm type good forf 3+ psi and a low-power piston type good for about 15 psi. I presume either is OK for the injection pump. I might yet try to use my electrical one instead of the one on the engine which IS a diaphragm type so it COULD be underperforming.

Your idea of bypassing the check-ball remains on the roster, as a permanent mod to do but I'll have to take another look at that hole on the bench because the fitting is also a hold-down device.

Cheers!
 
   / Lucas CAV rotary injection pump math
  • Thread Starter
#13  
I still don't understand how dynamic injection "timing advance" works, or IF it exists on these pumps.

The metering valve sets the amount of fuel injected, more fuel causes acceleration until stabilized. The governor flyweights apply an additional fuel AMOUNT increase on load to attempt to maintain speed by adding more fuel. None of this does anything to injection timing. If that is set to 5 degrees BTDC then when and exactly what and how increaes the number of degrees advance at a higher speed? Or is the static timing set on a stoped engine THE ONLY injection timing remaining valid thoroughout, an idea I would have a hard time digesting.
 
   / Lucas CAV rotary injection pump math #14  
More speed = more pressure = more pressure being applied to the pressure side of the advance piston.. The spring is holding the piston from moving to full advance at start-up..
When speed is decreased, the pressure is decreased & allows the spring in the advance housing to push the piston back.. inturn, moving the cam ring to adjust the "timing" of injection..
 
   / Lucas CAV rotary injection pump math
  • Thread Starter
#15  
More speed = more pressure = more pressure being applied to the pressure side of the advance piston.. The spring is holding the piston from moving to full advance at start-up..
When speed is decreased, the pressure is decreased & allows the spring in the advance housing to push the piston back.. inturn, moving the cam ring to adjust the "timing" of injection..

And I had worked on the "Advance Piston" fitting, too tired to think:laughing:

made 6 new runs, edited the same page, see bottom table:

http://trixtar.org/3/tinkerings/12valve208hp/index.html

Also tried an electric lift-pump, no change in performance. Rolled the whole circus indoors for 3 days of rain coming, expect to take a deeper look into the pump.

Cummins says the 5.9 engines with the Lucas-CAV use the gear letter D, except these fire pumps which (should) use the letter G which gives 5 degrees (1 tooth) less static advance. It so happens that I got the best result (up to 1900 rpm) using the letter D. I'd have a mind to go for it but for that I'd have to know that the two Lucas-CAV pumps perform an identical dynamic advance profile, which I do not know. Nor do I have any idea WHY these engines use 5 degrees less.

Also replaced the check-ball for the last run using the additional lift-pump. There was no difference at all either on account of the lift pump or the check-ball, still looks like a lack of dynamic advance unless I'm completely missing the diagnosis.
 
   / Lucas CAV rotary injection pump math
  • Thread Starter
#16  
I'm reading this 48page CAV shop manual (CAV and SIMMS Parts and Service LONDON w3 2124) and it 'seems' that what I thought was additional dynamic timing advance is actually a dynamic MODULATION of the static advance set via the gear and mounting provisions. As such, it would either ****** OR advance the static setting. Another untitled 21 page manual shows advance test at 1200 rpm as 1.5-2 degrees, and at 1800 rpm as 3.75-4.25 degrees but it doesn't say if these degrees are absolute, or added, or what. I would assume that not being negative these COULD be ahead or positive or further-advanced modulations. Thus the almost 5 degree figure would be close to the single-tooth or 5 degree increase from letter G to D which is what I got by making that shift on the relevant test run and getting rpm's up to around 1900. If the dynamic were operative maybe I would getthe same withOUT goping to letter D or I would get 5 more on top of letter D's 5 more than letter G's. I hope this isn't too freakin confusing, it is to me!
 
   / Lucas CAV rotary injection pump math #17  
OK.. last post.. When you rotate your engine until the pin falls in.. your at TDC on the engine timing.. When you put your LOCKED pump on, its actually set for 5* RETARDED.. its retarded for ease of starting & smoking.. {EPA}
The total advance movement on the pump is 5.75* to 6.25* @ 500pump & 1000 rpms engine..
So basically your starting at -5* & moving +.75 to 1.25* at "just above" low idle.. & thats all she's got..
It works for the rest of the world.. why not you??? I THINK you might be chasing ghosts.. & blaming the pump for something else..
 
   / Lucas CAV rotary injection pump math
  • Thread Starter
#18  
OK.. last post.. When you rotate your engine until the pin falls in.. your at TDC on the engine timing..

The #1 cylinder is at TDC, no problem with that, just like gas or in fact all piston engines and I have rebuilt a few. It's just that this is my second diesel patient ever.

When you put your LOCKED pump on, its actually set for 5* RETARDED.. its retarded for ease of starting & smoking.. {EPA}

THIS is news to me, I always presumed that it was advanced, just like gas engines, I have seen no mention of retarded in any of the documentation so far, and it certainly is a game changer.

The total advance movement on the pump is 5.75* to 6.25* @ 500pump & 1000 rpms engine..
So basically your starting at -5* & moving +.75 to 1.25* at "just above" low idle.. & thats all she's got..

Where is this and other such data, like the spring attachment 'code' published? I'd also wanna break down the part/model numbers and such.

It works for the rest of the world.. why not you??? I THINK you might be chasing ghosts.. & blaming the pump for something else..

I'm chasing whatever suspects I can think of, I have a 1300 hour engine that is sick. I'd much rather look elsewhere, and I have, but so far I've found nothing really wrong. That BTW is exactly where the previous owner gave up, something I on the other hand am not familiar with :)
 
   / Lucas CAV rotary injection pump math #19  
I MESSED-UP// The pump is locked 5* ADVANCED not retarded.. so in reality its starts at 5* & moves an additional 5*..
Sorry about that..
The code on the last line on the pump name plate is your fuel output @ what speed.. then the governor spring position, then the max rpm..
example> 113-1100-1-2400
spring code positions are a "code".. {1} & can be deciphered w/ a legend found on-line..
 
   / Lucas CAV rotary injection pump math
  • Thread Starter
#20  
I MESSED-UP// The pump is locked 5* ADVANCED not retarded.. so in reality its starts at 5* & moves an additional 5*..
Sorry about that..
The code on the last line on the pump name plate is your fuel output @ what speed.. then the governor spring position, then the max rpm..
example> 113-1100-1-2400
spring code positions are a "code".. {1} & can be deciphered w/ a legend found on-line..

Thanks for the info. I just made another run following rectification of yet another bug. Yesterday while intent on cleaning an otherwise insignificant amount of tiny paint chips from the inlet screen-filter I decided to check out that complete inlet end fitting. The little coil spring in the bottom of the pit was lying on its side (Murphy'd been there) , fixed that. At first I thought I had done it myself during disassembly but the test run video is unequivocally points a finger and shows a lot of improvement. Still not home base though.......... but it looks like a lesson in multiple-causes (like I needed one) :laughing:

Now that the 'fits' the engine rolls into are much less violent I ran it up to 2200 just to show more clearly what it's doing.

http://trixtar.org/3/tinkerings/12valve208hp/run-7-inletspring-1500.mp4

I want to get on top of this and once resolved I'll retime to the letter D on the gear.
 

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