VWDiesel.net The IDI, TDI, and mTDI source.
Engine Specific Info and Questions => IDI Engine => Topic started by: truckinwagen on January 28, 2011, 02:44:26 pm
-
ok, so I have an issue with the I-mark injection pump.
it originally had an altitude compensator that worked like a boost aneroid but backwards(ramp on the pin cut backwards)
so at full fuel allowed it was normal for no boost, and with minimum fuel it was a real pig that could hardly pull through a gear.
I wanted to use the aneroid for boost, so I got a pin cut the normal way, and now it normally sits at minimum fuel stop(like a normal TD does)
I then went to turn up the fuel to get back to normal, so when the boost pin is depressed I get lots of fuel to burn with boost.
trouble is that I cannot get the fuel back up to normal levels without the dreaded "hanging idle" so bad that it will rev itself once you get it off idle.
I did move the throttle lever over a couple splines to get the idle back down, and I have the idle so low that it hardly keeps running(about 450RPM) but it still hangs once it revs up.
any ideas would be appreciated!
-Owen
-
well, did the governor mod, hoping that would help with fueling allowing me to back off the fuel screw to help with the hanging idle.
(http://i229.photobucket.com/albums/ee139/truckinwagen/phone%20pics/IMAG0192.jpg)
(used a small nut to shim the main spring)
it did help some, the idle will only hang if I rev it up above 3000, and is a little sluggish to return below that.
and I can get the EGT to 1000* above 4000RPM, but only get to 900* at 3000RPM
I would like to be able to get EGT to 1200* anywhere in the RPM range(maybe higher as I am looking at nitrous)
and I just cant get there with the boost pin not seeing any boost and still have the RPM not hang all the time
-Owen
-
I am tempted to make a hybrid pump with the cummins pump I have.
use the pump body from the isuzu(along with the pump top and throttle assembly) and all the cummins insides and high pressure pump head.
only problem is I dont have a spare isuzu pump to use and then swap in, I would have to pull the pump off the car and then do the mods to it.
not sure if I really want to do that right now... although it would surely fix my fueling issues.
-Owen
-
Giles???
Is it a VE pump? Maybe mess with the advance
-
it is a ve pump, it just has a different mounting setup(two ears instead of three) so a vw pump body wont work.
I would do the advance mod, but I would have to pull the pump to get to the advance cover, as the intake manifold is in the way.
if I do pull the pump at some point, I will do that though.
-Owen
-
ok, I got the cummins pump apart(mostly to see how bad it would be to swap its innards over)
here it is!
(http://i229.photobucket.com/albums/ee139/truckinwagen/phone%20pics/IMAG0194.jpg)
(http://i229.photobucket.com/albums/ee139/truckinwagen/phone%20pics/IMAG0195.jpg)
(http://i229.photobucket.com/albums/ee139/truckinwagen/phone%20pics/IMAG0196.jpg)
(http://i229.photobucket.com/albums/ee139/truckinwagen/phone%20pics/IMAG0197.jpg)
looks like I can just swap out the parts from the cam plate out to the high pressure pump head.
but my question is this, is it necessary to swap the control lever too?
or will the control lever from my pump(8mm) work on the cummins pump head(12mm)?
thanks,
-Owen
-
check out the super colorful cummins advance spring!
(http://i229.photobucket.com/albums/ee139/truckinwagen/phone%20pics/IMAG0201.jpg)
-
so got the isuzu pump apart, and turns out one of the springs for the high pressure pump is broken.
(http://i229.photobucket.com/albums/ee139/truckinwagen/phone%20pics/IMAG0206.jpg)
(http://i229.photobucket.com/albums/ee139/truckinwagen/phone%20pics/IMAG0207.jpg)
the camplate looks very close to the cummins one, the cummins one has a slightly taller lobe, and much shorter duration.
(http://i229.photobucket.com/albums/ee139/truckinwagen/phone%20pics/IMAG0204.jpg)
(isuzu on left cummins on right)
I decided to use the cummins camplate with the cummins pump head(why not?)
look at how tiny the 8mm plunger looks next to the 12mm plunger ;D
(http://i229.photobucket.com/albums/ee139/truckinwagen/phone%20pics/IMAG0205.jpg)
its all back together now, and will put it back in the car later tonight.
-Owen
-
oh, and I took a HUGE stack of washers out of the advance piston, should help with dynamic advance some.
-Owen
-
well, I got the car all back together, replaced the starter while I had it apart(the IP is right in the way of it, and I have been meaning to replace it anyway)
battery died before I got it primed and fired though, I have the battery charger on right now, and will try again in a while.)
-Owen
-
well, got it running!
was a little too advanced to start with, was hard to start and clattered really bad.
after retarding it a little, it started really easily and quieted down a lot.
with the new larger pump head the throttle response is much better, and I was able to tune it to idle fine and blow lots of black(and thats with the boost pin in the no boost position)
have not taken it out on the highway to see what EGT looks like on a hard pull, but it will get to 950* by the time I get to 45MPH, thinking I am well set for my 1200*+ on a long pull.
right where I want it for nitrous, etc...
-Owen
-
wow your good. Never would i get something done that fast.
-
I was a little apprehensive about trying it on my daily(with only half a day to get it done) but it went really smooth.
surprised the crap out of me to tell the truth.
-
That 12mm pump looks weird, I'm used to seeing 9mm haha.
-
yeah, it certainly is different!
with more than twice the pumping capacity of the 8mm it runs much differently too
-Owen
-
well, I drove it out on the highway to borrow a garage today, and it drives real nice except that it falls on its face at 4000RPM.
it pulls real hard right to 4000, but stumbles and has a hard time accelerating beyond that.
I am thinking that it is running out of timing on top, I might advance the static timing a bit to see if that helps, and if it does, I might modify the timing piston cover to allow farther travel of the advance piston/ install a softer spring
-Owen
-
what about increaing internal pressure a bit? I really dont want to have to remove the pump again(the only way to pull the timing piston cover is to pull the pump)
increasing internal pressure would advance further at high RPM right? as long as the piston is not bottoming out on the cover, yes?
-Owen
-
Right, someone graphed the curve (actually a straight line) pressure doesn't change the curve, other than to move the whole line forward.
It makes the starting point change come in later, along with the whole line.
I wonder if removing the shims might have advanced your high RPM timing too far.
You did the gov mod right?
-
yep, gov mod is done(pic of it early in this thread)
I suppose I could advance static timing and see if that helps, and then retard static timing to see if that helps.
should identify if it is too advanced, or not advanced enough at high RPM.
hard to believe that it could be too advanced to continue accelerating though...
it does clatter pretty loud on the throttle, but the cummins pump did that on the VW too, something to do with the injection event being really short compared to the smaller pump head.
-Owen
-
I think fat's correct, IIRC different IP's have different pressure regulator springs with different advance curves.
Look in the vwdieselparts forum in general, there's a sticky called "internal injector pump pressure" or something with some pretty good info in it.
-
yeah, I know the internal pressure and advance spring are matched, but I was just wondering if it were possible to advance so far that it would not burn the fuel properly.
supposedly giles pumps have ridiculous amounts of dynamic advance.
regardless I could see if it was too advanced or too retarded by playing with static timing(as it affects dynamic timing)
then I could play with the dynamic advance mechanism to match what is needed(if its advancing too far I could put the shims back in, and if it is not advancing enough I could modify the advance cover to allow more travel)
-Owen
-
Let me rephrase that to mean what I'm thinking ;D, there's a spring in the pressure regulator and another (much larger) spring under the advance piston cover.
I'm talking about spring #3 in this picture:
(http://i249.photobucket.com/albums/gg218/rabbitdude82/avance2.jpg)
I'm pretty sure you can use a different one and get a totally different curve.
I just thought of that if your internal pressure is just not high enough, the 12mm pump with its heavier return springs might be fighting the advance piston as it tries to climb the camplate, thus never reaching full advance. So if you bump the pressure up the piston might have enough hydraulic force behind it to overcome the heavy springs and boom, more power!
-
I like that!
especially at higher RPM's the heavier springs(and heavier plunger) would hold lots of pressure against the rollers.
the only seal I did not replace was the main shaft seal(I only had a 17mm shaft seal in my kit, and the isuzu pump has a 20mm shaft) hopefully the higher internal pressure will not make it leak!
thanks for that,
-Owen
-
well, I tapped the pressure regulator down some(not much, like 1/100 of an inch) and saw little improvement.
after class I will try advancing static timing to see what that does
-
well, I advanced the static timing just shy of where its a pain to start.
this did move the stumble up 500RPM(from 3750 to 4250) so it definitely needs more advance up top.
I will achieve this by getting ahold of a softer advance piston spring and machining the piston cover to allow more travel.
anyone know which is the softest stock VW timing advance spring?
I think it is the green one, but I could be wrong.
-Owen
-
also, will running timing really advanced(at low RPM at least) hurt anything?
not sure if I should put the timing back where it was and deal with the hesitation before 4K until I can get the new advance spring, or if I should leave it where it is now until then...
ah, and other than the problem at 4K this thing is like a different car!
never thought an N/A could be transformed so much without adding a charger!
it now has power to accelerate at 60MPH, where it used to be flat out, and take forever to get to 65.
loving the car more than ever now, all I need to do is get it quiet again(between the injection clatter and exhaust, you need earplugs to drive it any distance)
-Owen
-
I seem to recall green being the softest.
I don't think excessive advance will hurt at high rpm but I have heard stories of pounded rod bearings, broken pistons and of course blown head gaskets. I'd really try to keep it in the safe zone, I would think that you shouldn't have to worry much at high revs though.
For punching in the pressure regulator it would make it lots safer to use a pressure gauge while doing it. I did mine a couple years ago and it was very easy to over do it even with a gauge, I'd tap it over and over and nothing would happen so I'd hit a little harder and all a the sudden the gauge would shoot up and it would start clacking harder. So instead of going from 35psi up to 45 it would jump to 55 or something. The fix is to remove the regulator, pound it all the way through and then start over.
-
ok, I will pull the timing back to normal in the morning then.
now that I have more power, I find myself needing to go past 4000 less, so its not such a big deal.
not to say that I don't want to fix the problem, I will need to go as far as I can RPM wise when I take this thing to the drag strip.
-Owen
-
I think we need jedi master giles here, this is pretty cool stuff, May look into something like this for my build.
cool
-
will try that, but advancing timing certainly helped high RPM running(lifted the "ceiling" by 500RPM)
so I am pretty sure it needs more timing up top.
-Owen
-
well, I retarded the timing to where the clatter at idle was almost eliminated, and now it hits the stumble and looses power at 3000RPM
gonna time it in the middle for now, so it is more drivable(with a 3-speed I need to rev past 3K alot) and then get the softer spring for the advance to fix the problem outright.
-Owen
-
that I did not swap over, and it is easy to do(not hidden by the intake manifold)
I'll try that.
I did clearance my spare timing spring cover(to allow more total timing advance) to go with the softer spring, if it comes to that.
(http://i229.photobucket.com/albums/ee139/truckinwagen/phone%20pics/IMAG0215.jpg)
but to get to the timing advance cover I have to pull the pump, so I will wait until I get the green spring before I do that.
-Owen
-
cool, thanks!
-
Which pressure regulator did you use? They are specific to the plunger size so you'd need to use the cummins one.
My gut feeling says that'll fix it ;D
-
well, changed the regulator.
it helped, but not much, moved the stumble from 3000 to 3250RPM
gonna go forward with the softer advance spring.
-Owen