injector strategy

[greg lousy]

I became aware that I was basically running on 3 cylinders a while back due to my milage, power, and excessive white smoke. Now that its warmer I've gotten to work. I wanted to post my process and plan here to get some feedback.

First I went through loosening the injector line unions and determined that my number one cylinder was either not firing or barely firing. then I put my injector lines on backwards and had my wife crank while the injectors sprayed into a cardboard box (it was mentioned here). Suprisingly, they all seemed to spray consistently and powerfully. then I did a compression test - 520 485 520 460.
Then I put them back, switching the problem injector to the number 2 cylinder and sure enough, 1 started firing fine and the problem moved to 2 (again loosening the unions).
About a year ago, I replaced the nozzles in all injectors. So now i'm thinking that although the spray pattern looked fine, the injector in question has a problem in breaking pressure, so its out of time. I'm about to get a remanned injector and switch it out. I know switching them all out would be better but I really can't afford it right now.

I've set my general timing about 6 times and my injection timing probably ten, using a dial indicator to get in the ballpark then tweaking it "hillbilly" style. So i'm no pro, but fairly confident in these areas, and can't see why the timing would affect one cylinder so disproportionately. So I haven't messed with it - I focused on and tweaked the IP timing pretty thoroughly last time.

thoughts?

[TylerDurden]

Making a DIY pop-tester is not very hard to do. Then you will know the story. Whereas a reman may also not match in pressure.

Mark the Limey has some tips on shimming the injector internals, and there is the speculation that injectors can be tuned by changing the amount the body is turned in relation to the nozzle retainer.

[Quantum-man]

OK here's what I'd do with limited resources:

Take one or even two of the 'good ones', as well as the 'bad one' and loosen their body halves.

Keeping upright, unscrew each in turn, until you can just part the body.

Now using the point of separation as a reference angle, count the number of turns before the spring starts to be compressed.

It's quite easy to find, and in my experience, will show up a low or high break pressure.
Best not to disturb the nozzles, [at least not yet].

If the one seems different, lift off the injector top, reinsert the shim [if it has fallen out] and it's spring and check for protrusion of the spring.
Compare with a good one.

No feeler gauges?
Then open up a good one and point the tops of the springs towards each other, the spring of one touching the rim of the other like snails having coitus, [as Sheldon would say]

One spring shim combo should be shorter than the other.
Check springs and check shim thicknesses to find source of difference...

[Quantum-man]

Ha ha, beaten by 2 minutes...
Sections of old feeler gauges, pieces of tape measure spring, pieces of razor blade, all work perfectly as you blueprint the 4 break pressures once you have your tester made.

[Fatmobile]

Right, from the time the top comes in contact with the spring until you tighten it down @52ft.lbs. should be the same degrees.
I remembered that as one of Hagar's trick.

[JHH]

Keeping upright, unscrew each in turn, until you can just part the body.

Now using the point of separation as a reference angle, count the number of turns before the spring starts to be compressed.

Are you sure that's a good idea, Mark? I know you like to think outside the can, but it seems that way might introduce some unwanted variables... unless I'm reading you wrong. The Hagar Method seems more reliable; basically thread-counting as well, but starting from the other end so as to measure spring deflection directly... Like Fatmobile suggests.

Here are the numbers again, since I have it written down in front of me.

Thread pitch 1.5 mm.
0.05 mm per 5 bar breaking pressure.
1 turn = 150 bar.
25 bar per 60 deg / 1/6 turn / 1 wrench flat.

[JHH]

Interestingly I checked my injectors recently using the Hagar Method, and they all bottom out at just about 240º... a mere 100 bar. I might have them pop-tested when I can afford it. The nozzles turned out to be French even though the injector-bodies say Brazil, so I shouldn't complain too much.

[greg lousy]

well screw it. sounds like I've got all I need to work this out, save some money and come out better.


I'll probably address this immediately by taking them apart and putting them back together with all this great information.
For the long term though... I just read a lot here about diy pop testers.... hmmmmm, we'll see. I'm curious. Has anyone just jimmied a gauge in between the injector line and injector and pop tested using the IP itself? hand turning the engine?

as always, thanks

[JHH]

That's actually a really good idea, especially since you already know how to check spray pattern with the engine. I don't know about the fittings; you may have to somehow fit the end of an old injector line to the top half of an injector... Alternatively you could make up a device that replaces the line altogether.

Good thinkin'.

[Quantum-man]

Keeping upright, unscrew each in turn, until you can just part the body.

Now using the point of separation as a reference angle, count the number of turns before the spring starts to be compressed.

Are you sure that's a good idea, Mark? I know you like to think outside the can, but it seems that way might introduce some unwanted variables... unless I'm reading you wrong. The Hagar Method seems more reliable; basically thread-counting as well, but starting from the other end so as to measure spring deflection directly... Like Fatmobile suggests.

Here are the numbers again, since I have it written down in front of me.

Thread pitch 1.5 mm.
0.05 mm per 5 bar breaking pressure.
1 turn = 150 bar.
25 bar per 60 deg / 1/6 turn / 1 wrench flat.

OK, Your points seem reasonable.
1) Practicing hygiene, ie on clean cloth is recommended. Pointing body tops and spring shim combos was just another lateral thinking, method to overcome tool starvation.

2) Hagar's method of going from initial spring compression point to rated torquing, is fine, but you need a torque wrench, equally lubed/frictioned injector threads, and you still need to judge the point of start of spring compression, which cannot be done with the torque wrench, unless you also have one of those low torque screwdriver type tools for nuts on clocks etc. [I just happen to have one ]

With my method, I have found the casings of a batch/similar type, are all threaded from the same starting point. Thus the test can be done by hand, and with the same result.
I'm envisioning a tool free scenario here.
Incidentally; I have never found the 0.05mm of shim per 5 bar particularly repeatable, and most frustrating when trying to get matching better than 2 bar. Which is why I make my own additional shims. N/a springs and TD springs are different too.

Remember we are only looking for a difference from 'the norm'.

3)I must revisit his thread. I thought he had strayed into the possibility of adjusting the break pressure slightly by altering the the turn. Clearly this has the issue of body leak for under torque and as I've made it clear, over torquing collapses the nozzle body [a tube] onto the pin, more or less, creating binding.
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[Quantum-man]

well screw it. sounds like I've got all I need to work this out, save some money and come out better.


I'll probably address this immediately by taking them apart and putting them back together with all this great information.
For the long term though... I just read a lot here about diy pop testers.... hmmmmm, we'll see. I'm curious. Has anyone just jimmied a gauge in between the injector line and injector and pop tested using the IP itself? hand turning the engine?

as always, thanks

There used to exist injector testers that screw inline, monitoring, the pressure. Things to be wary of are introducing extra volumes of diesel into the line, as it's compressible to 1.5% per 100bar.

On a slightly different tack, this can be used with injector still on engine... By TI Dieseltune a very elusive company , that makes or made, some great diesel test stuff...

http://www.ebay.co.uk/itm/Diesel-Inject ... 35d4cce482

[TylerDurden]

I've often wondered what the residual pressure was in the lines after the pintle closes, and how much variation there might be across delivery valves. An inline tester might answer that.

[82vdub]

It may be very difficult to install an inline tester in an actual installation. There's not much give to the injector lines, so if you add something that's much more than a half inch, the lines may not line up properly on all ends. Just a thought to ponder.

[Quantum-man]

It may be very difficult to install an inline tester in an actual installation. There's not much give to the injector lines, so if you add something that's much more than a half inch, the lines may not line up properly on all ends. Just a thought to ponder.

OK how it works is a pair of short lines. And now I've found the exact item...

http://www.ebay.co.uk/itm/DIESELTUNE-iN ... 338c5f5594

Tyler, I'm not sure how you'd measure the residue dynamically, unless you revved engine and turned off quick. Not sure how fast back leakage is when switched off

[greg lousy]

well that'd do it wouldn't it...

I was thinking it doesn't necessarily have to connect to the engine


I've been thinking about putting a gauge on my IP for a while and now I'm thinking about getting the fittings so I can just move it over to the an injector line and test breaking pressure - can anyone recommend a good gauge?

... it all connects to figuring out my situation - today the problem injector was actually firing pretty good, further confusing me - it was the first fire after compression testing so maybe it just seated a little differently? or its just on the border of missing?
Also, the main bearing on my IP is worn - fairly new remanned IP and I think it came that way - I think it loses a bit of pressure while sitting but appears OK when running - no air from the out bolt - good resistance when you pull the cold start at idle...
... all in all another reason for doing the whole pressure gauge thing. I've pulled the injectors. I plan on checking them out with more care like people have been explaining, then adjusting IP timing for now