Pump Timing Observation

[Midnite]

I picked up the Snap On SP144 fuel pump wrench and decided to play with a little more advance. My pump timing was already set at 1. 5mm by Piers when my wife and I drove through the area this spring.



Before I advanced it myself, I was hitting 1300+ deg. empty, no problem, and about 26 psi boost (also empty). Keep in mind that I have PW injectors and a PDR HX-35 with a non-wastegated 16cm2 housing.



Piers' advancement to 1. 5mm resulted in a little less than 1/8" difference between marks on the pump and gear case. He'd mentioned that when I pulled into his shop, my timing had been 1. 31mm.



I wanted to rotate the pump about 1/16" further and see what effect it had on things. There was barely the slightest difference in sound, so I'm pretty confident I'm still within the safe zone. But there was a dramatic difference in boost and EGT. Max boost is now 17psi, and I can't get EGT higher than 1000 deg. (and both of those are with a 1200 lb. camper, up a hill!).



There is also *zero* smoke now, even at full throttle (it used to leave a nice gray haze behind).



I know that advancing pump timing generally reduces measured boost and EGT, but I wasn't expecting that much of a difference! Do those numbers sound reasonable to those of you who play with pump timing quite a bit?



Thanks,

Mike

 

[Midnite]

Bob, Nascar Mark, anybody?



The complete lack of smoke now surprises me and makes me think something is wrong. Any feedback would really be appreciated.



Thanks,

Mike

 

[Midnite]

Wow, over 120 views and nobody has any opinions?



Since my performance has dropped a little with the additional timing advance, I'm going to back it off a little bit and see if things improve.



I'd still like to hear from those who actually work on these engines for a living as to whether the effects I'm seeing are normal for the extra advance I've added.



I think my max boost and EGT dropped more than they should have, and the total lack of smoke seems to back that up.



However, I work on unix servers for a living, which was why I was hoping someone who works on diesels for a living would pitch in here.



Thanks,

Mike

 

[Greenleaf]

I'm still thinking... ... ... ... ... ... ... .....



I will be experimenting with my timing again when the new injectors are in. Stay tuned... ...

 

[nascar mark]

Sorry Mike, This one slipped by me. Been so busy at work/home/play, that I haven't spent much time helping out on this end.



This is not normal. You are lacking fuel some how now. Did you do any other adjustments when adjusting timing?

9 psi drop for a small timing adjustment is not normal. Also you mentioned a decrease in power? Is it only of the line at low boost or mid or top?

Need to know your adjustments/settings. More the better.

 

[Midnite]

Thanks Mark!



Low end power maybe dropped a tiny bit, mid-range seemed about the same, and top end seemed to be noticably weaker (should be stronger with the increased timing, right?)



For a long time I've had my full power screw turned in up to the collar, and never really messed with the star wheel. I've also had the eccentric turned out for max pin travel.



The only screwup that I can think of when I bumped up the timing was that I also turned the star wheel clockwise one full turn. I call that a screwup because I know better than to change more than one setting at a time when playing with things. Anyhow, I turned the star wheel back, even though I knew that would cut back on the fuelling rate. Other than that, I've made no changes to the pump. I looked to see if maybe I kinked a fuel line somewhere, but didn't see anything. Is there anything else I could look for?



I'm going to try turning the timing back to 1. 5mm to see if things go back to the way they are, but I'm guessing if I lost fuelling somewhere along the line I won't see much change?



Thanks,

Mike

 

[Midnite]

Well, I backed the timing back to the PDR setting, and I'm still low on boost and EGT (20psi and maybe 1200).



I decided maybe I goofed something up on my throttle linkage, so when I was looking at that I noticed something--on the part that "see-saws", the end that rests against the idle stop is hitting a fuel line that comes out the top of the pump near the gear case. I didn't trace the line too far, but it looks like either the main feed from the lift pump, or an overflow line that heads back that way. It's hitting that fuel line at very near full throttle, which makes sense since my low and mid range seemed fine.



I can't see how I could have bent the line so that it got in the way of the linkage. I did try loosening the nut, but it was just a hair too small for my 14mm wrench, and too big for 13mm. My 9/16 in. is about identical to 14mm, so that didn't work either. I'm guessing it's a 14mm nut, and my wrenches are just cheapies that are a little off.



What do you guys think?



Mike

 

[Greenleaf]

Well,,,,,I'll tell you what. I'm working on installing injectors and advancing my pump some more as I write this. I have my throttle adjusted to the point that the lever is just up against that fuel line you speak of. If I try to get any more speed out of the old girl it wont happen until I move it over some. What aggravates the situation is advancing the timing... it seems to bend that line enough to cause trouble if your operating high RPM's.



If you need... I'll locate the wrench size for you.



a. k. a. greenleaf

 

[cerberusiam]

That would be the main fuel supply for the pump. I had rebend mine after advancing the pump to get the throttle lever to quit binding on it.

 

[Greenleaf]

Wrench size

... ... . 14mm... ... .

 

[Midnite]

That was it! I bumped the timing up a tiny bit again (but not as much as before), and bent the fuel line down so that the lever wasn't hitting it. I now have 25psi boost and 1300 deg. EGT again.



One question though--for those of you who set timing the "correct" way when my pump is set at 1. 5mm, and I move it 1/16" more, about where would that put me? Maybe 1. 6mm or a little higher?



Thanks,

Mike

 

[Greenleaf]

Further Advanced

I bumped my timing up another 1/16" This would give me 3/16th of advance, best I can judge. The sound has changed, had to slow the idle speed down and the truck wants to jump right out of it's tires



I did not calculate change to boost/EGT because I also installed a different set of injectors at the same time so my boost/EGT went up a bit from that i'd say.



a. k. a. Greenleaf