What did I do?

[Thewespaul]

It's not that it is affecting maximum injection pressure it's that it is able to scavenge the volume of fuel to inject sooner with the plungers opening further. This is my understanding from what Mel explained to me, and I trust a experienced pump builder like Mel over a dude on YouTube with a diagram.

 

[Macrobb]

It's not that it is affecting maximum injection pressure it's that it is able to scavenge the volume of fuel to inject sooner with the plungers opening further. This is my understanding from what Mel explained to me, and I trust a experienced pump builder like Mel over a dude on YouTube with a diagram.

And that's true... AT WOT!
The plungers aren't going to open further /without the fuel getting to them/. This will only happen at full throttle; otherwise, how do you think you can vary RPM and torque?

Also... you trust someone's explanation over a cutaway of the device in question? It's not that he has a diagram(watch the video!), he's got a frigging cutaway pump! You can /see/ how it works!

Edit:
I may have misunderstood you a little.
The plungers do not have springs behind them, nor do they open by themselves. Fuel pressure pushes them open. The cam cam ring then pushes them shut. So, there is no "suction" going on anywhere in the pump - fuel that has "jumped the gap" into the rotor pushes the plungers open by the precise amount of fuel that is there. More fuel = more advanced timing, as the cam ring is fixed*
But, unless you get the fuel in to the pumping element in the rotor, there's no way for the plungers to fully open, because /nothing but fuel pressure opens them/.

(*The cam ring is attached to a separate plunger in the housing that moves based on transfer pressure - more RPM = more transfer pressure = more advance. So light load at high RPM is more retarded than heavy load at the same RPM.)

 

[bbjordan]

So light load at high RPM is more retarded than heavy load at the same RPM.

Light load at high RPM is more advanced than heavy load at the same RPM. The light load advance cam comes into play here. The more you have your foot into it, the more retarded the timing is.

 

[Macrobb]

Light load at high RPM is more advanced than heavy load at the same RPM. The light load advance cam comes into play here. The more you have your foot into it, the more retarded the timing is.

I didn't want to get into that, because that is yet another "counfounding" factor when it comes to measuring timing... and I'm also not entirely sure how far it applies. I know the cam "runs out" early in the throttle pedal; I've heard that it's in the fully retarded position by 2K RPM unloaded... but I'm also not sure of that. It certainly depends on how far it's adjusted, and I haven't had a new stock IP that I could really check....
I did find this DB2 Bench Calibration manual, but I'm not sure how to get this number out of it. Page 12 has some useful info...

The problem is that if it isn't run out by 2K you are balancing three different things when timing it by the timing light: Retard from very little fuel, Advance from transfer pressure, and partial advance/retard by the light-load advance cam*... so even slight differences in RPM would make a big difference in timing numbers.

Also, it has nothing to do with the relative timing based on the fuel screw - the cam(having not been moved) is going to affect the timing exactly the same from idle to WOT, throughout the load range.

(*Note: the light load advance cam is actually a "retard" cam - The more throttle, the more the cam ends up pushing a spring against the retard side of the advance piston... but it hits the fully "retarded" position quickly).

 

[Clb]

@towcat That link may be tech section worthy????

 

[Macrobb]

@towcat That link may be tech section worthy????

Probably? I didn't even know I had it until I found it in my truck folder last night. I've uploaded another couple of files as well.
Might be a good idea to make a few backup copies/links in places.

 

[Clb]

Go to the tech section and load it, then a mod can add it in.

 

[towcat]

@towcat That link may be tech section worthy????

just looked through it. I don't see any copyright logos, so we should be ok to post. i'll work on it later on today.

 

[FORDF250HDXLT]

if your at 16 degrees, that thing should be very loud and rattle when running, even worse when cold. is it? you say you cleaned the spot on the lines a year ago, did you reclean them? my tech time is very picky on clean lines to get a good reading.

Yeah,someones meter isn't any good.If he was at 16 BTDC........He'd know it.

 

[crash-harris]

I cleaned the lines yesterday, but haven't had time to put the meter on it again. I did notice that the tube for the magnetic probe was wobbly again. I put some JB weld on it last time I timed it in an effort to stabilize it. Looks like it's rattled loose again over the past year.

 

[Clb]

What mag probe holder are you using????

 

[crash-harris]

The only one the probe fits in, skinny one. On my set of timing marks it's loose.

 

[Dieselcrawler]

on any that i time, if the crank pickup hole is loose, i dont use. it. but i have the timing light also for my tech time, so i get RPM from injector line and use the light. if that is loose and you dont have it set at the right spot it can angle the probe enough to change the degrees

 

[crash-harris]

That could be my issue. Well, maybe I'll get to jb weld the tube again next Sunday (a day I won't be driving it so it can cure straight) if I'm lucky.

 

[Clb]

First try EQUALLY spreading the spring that is around the mag probe end, this will tighten the fit....some ham handed p.o. could have yanked it out !?
Not being a rustbelter, is the holder size larger due to rot?
I think jb welding it up could be problematic.

Next I would think about having the meter checked ....