hybrid isuzu/cummins pump finished!

[truckinwagen]

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

[truckinwagen]

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.


(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

[truckinwagen]

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

[theman53]

Giles???
Is it a VE pump? Maybe mess with the advance

[truckinwagen]

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

[truckinwagen]

ok, I got the cummins pump apart(mostly to see how bad it would be to swap its innards over)

here it is!









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

[truckinwagen]

check out the super colorful cummins advance spring!

[truckinwagen]

so got the isuzu pump apart, and turns out one of the springs for the high pressure pump is broken.




the camplate looks very close to the cummins one, the cummins one has a slightly taller lobe, and much shorter duration.


(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


its all back together now, and will put it back in the car later tonight.

-Owen

[truckinwagen]

oh, and I took a HUGE stack of washers out of the advance piston, should help with dynamic advance some.

-Owen

[truckinwagen]

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

[truckinwagen]

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

[theman53]

wow your good. Never would i get something done that fast.

[truckinwagen]

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.

[rabbitman]

That 12mm pump looks weird, I'm used to seeing 9mm haha.

[truckinwagen]

yeah, it certainly is different!

with more than twice the pumping capacity of the 8mm it runs much differently too

-Owen