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  #1  
Old 09-04-2010, 08:38 PM
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Low buck pop tester. Correct me if I'm wrong

Here is a pop tester I made for about $110, just got it together today. Seems to work, though I may need to get a more precise gauge. I may just be too green to read it properly since all I've done so far is test some of the used injectors I have. The pressures and spray patterns are varied, as is expected with used parts. I used the porta ram design I found somewhere on this site, and except for a couple of fitting changes, the parts recommended from McMaster work just fine.

Nothing is bolted down yet, real 3rd world type of operation.

What my limited math capabilities have shown so far is that 135 bar shims are around 1.5 to 1.6 mm (~2000 psi), while the 115 bar shims are 1.40-1.45 (~1680 psi). The psi readings are not absolute, and I'm trying for a little higher pressure for each type 137 and 117 respectively.

If any one sees fit to correct any of this, I'd be grateful.

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Low buck pop tester. Correct me if I'm wrong-0904001900.jpg   Low buck pop tester. Correct me if I'm wrong-0904001900a.jpg   Low buck pop tester. Correct me if I'm wrong-0904001901.jpg  

Last edited by wildest; 09-04-2010 at 09:50 PM. Reason: Grammer, context
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Old 09-04-2010, 08:49 PM
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Ideally, you should have a shut-off valve for the gauge. Otherwise, the gauge takes a beating when pumping fast to check spray pattern and chatter.
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Old 09-04-2010, 08:57 PM
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No fluctuation on the gauge at all, it's a decent glycerin filled gauge, and the design I followed stated the same. It seems to be okay, but I'll keep this updated as I learn more. I don't have to pump too fast to get the injectors to chatter. Once I get to the break pressure, just another stroke and it chatters, more strokes and more chattering.
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Old 09-04-2010, 09:09 PM
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Originally Posted by wildest View Post
No fluctuation on the gauge at all, it's a decent glycerin filled gauge, and the design I followed stated the same.
Liquid filled gauges lack the sensitivity necessary for accurate pressure testing.
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Old 09-04-2010, 09:13 PM
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So I'll be modifying this a wee bit more. Thanks.
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Old 09-04-2010, 09:15 PM
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Originally Posted by wildest View Post
So I'll be modifying this a wee bit more. Thanks.
Would the inaccuracy be too bad to get some injectors rebuilt? I need to do one of my cars tomorrow (Sunday), no access to a new gauge before then.

Last edited by wildest; 09-04-2010 at 09:51 PM.
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Old 09-07-2010, 08:55 PM
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The comments on other threads about not using the value of the previous shims is my experience, too. To get 1700psi/~117 bar I used shim sizes from 1.27 to 1.53, so there is no 'range' when rebuilding. But taking them apart and replacing shims is not a bad job. Keep it clean.
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Old 09-08-2010, 12:31 AM
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You Gauge will be accurate enough because there is a wide acceptable Pressure Range.

There is an acceptabel low and high range or opening pressures for rebuilts; and there is an acceptable amount that they need to all be balanced to for each other as a set.

All of the above is detailed on a bunch of threads.

It is just tough to eye ball a small Gauge with out small graduations on it unless the Opening Pressures just by chance happen to line up with a graduation mark on the gauge.
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Old 09-08-2010, 07:40 AM
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Quote:
Originally Posted by wildest View Post
Would the inaccuracy be too bad to get some injectors rebuilt? I need to do one of my cars tomorrow (Sunday), no access to a new gauge before then.
Is there a drain for the glycerine? If so, drain and save it in a bottle to be put back in when you want to.
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Old 09-08-2010, 12:42 PM
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My $1630 pop tester

I dont agree with the statements concerning the liquid filled gauge. The liquid dampens pulsing but as a rule are MORE accurate then non filled gauges. However accuracy is a function of the quality and expense of the gauge not if it is liquid filled or not. So anyway I just finished REV 3 of my first pop tester. I haven't tried it yet other than to pump lots of fluid through it to make sure its CLEAN. I'm using a large gas line filter for a filter and a reservoir. The cost break down is as follows .... parts about #0 bucks, lathe to make fittings $1000, welder to mosify jack $600. So there you have it, just don't tell my wife.
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Old 09-08-2010, 01:00 PM
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I dont agree with the statements concerning the liquid filled gauge. The liquid dampens pulsing but as a rule are MORE accurate then non filled gauges.
You don't understand the issue. The issue isn't accuracy or precision, it's responsiveness. Liquid-filled gauges are not adequately responsive for injector pop testing. No two ways about it.
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Old 09-08-2010, 01:37 PM
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You are right I don't understand the issue you bring up. I have never tested and injector or used my tester so Maybe that will help clue me in. My thoughts are that you may be seeing a loose or high fluctuating needle as acuaracy which it is not. If it over shoots 10 % then thats your unknown where as a liquid filled typically wont over shoot as much. It all goes back to accuracy of the gauge. Yes a cheap air filled guage will move around alot but what is it reading. Technically it is probably reading "jerk" or "momentum" which in this case doesnt tell you what you need to know. It boils down to money spent on gauge, in my case not very much. I'm cheap but I do like to learn so I guess I'll have to see. Thanks
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Old 09-08-2010, 01:44 PM
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Quote:
Originally Posted by wildest View Post
The comments on other threads about not using the value of the previous shims is my experience, too. To get 1700psi/~117 bar I used shim sizes from 1.27 to 1.53, so there is no 'range' when rebuilding. But taking them apart and replacing shims is not a bad job. Keep it clean.
Where does one obtain the shims if he is going to do this himself. I do not see them online from this site.

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Old 09-08-2010, 04:29 PM
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Originally Posted by DocSarvis View Post
You are right I don't understand the issue you bring up. I have never tested and injector or used my tester so Maybe that will help clue me in. My thoughts are that you may be seeing a loose or high fluctuating needle as acuaracy which it is not.
Unlike many situations involving pressure measurement, pop testing is a very dynamic event; it should be fairly easy to understand the need for a near real-time indicator.
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Old 09-08-2010, 07:24 PM
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Quote:
Originally Posted by DocSarvis View Post
I dont agree with the statements concerning the liquid filled gauge. The liquid dampens pulsing but as a rule are MORE accurate then non filled gauges. However accuracy is a function of the quality and expense of the gauge not if it is liquid filled or not. So anyway I just finished REV 3 of my first pop tester. I haven't tried it yet other than to pump lots of fluid through it to make sure its CLEAN. I'm using a large gas line filter for a filter and a reservoir. The cost break down is as follows .... parts about #0 bucks, lathe to make fittings $1000, welder to mosify jack $600. So there you have it, just don't tell my wife.
I can explain why a non-liquid Gauge is more desierable. But, at the same time for a persond rebuilding his own Injectors a Liquid Filled Gauge is OK.

This is the way I used to do it at work:
Hook up the Injector to the Nozzle/Pop Tester.
Turn the Valve to cut off the pressure to the Gauge.
Rapidly work the Tester handle to get rid of all of the Air; after which you work the Tester handle at various speeds and repititions while observing the spray Pattern. You want to see a good spray pattern even when you work the handle slow and constant; you want to hear a long chatter.

Next you open the valve a little to expose the Gauge to pressure. I would work the handle medium slow just to see where the Opening/Pop Pressure is.
After that I would very slowly work (one stroke of the Handle) the handle and watch the Gauge Needle moving up to the Opening/Pop Pressure.
As I am approching the Opening/Pop Pressure I would like not to see any Fuel drops leaking out of the Injector Pintlel.

When I reach the Opening/Pop Pressure I want to see the Gauge Needle reach that pressure; hear the chatter of the Nozzle and see that Needle suddenly and rapidly fall to a lower pressure. (This is the part that you cannot do with a Liquid Filled Gauge. Also no Pop Tester made by a Fuel Injection Equipment Company comes with a Liquid Filled Gauge and they all have a shutoff valve to protect the Gauge from some one "Rapping" on the Tester Handle.)
So in short you want a slow pressure to build up to the Pop pressure is reached and the Injector Pintle to suddenly open, spray and close; and this can be observed by watching the Gauge Needle.

Spray Nozzles with sticky Pintles will not pass the Test step in Blue. They will open OK but the will not close as rapidly as a good Nozzle will. The spray might start off good but the dribble at the end of the spray cycle.

Spray Nozzles with a bad seating area will just squirt ot the Fuel instead of atomizing it as you approch the opening pressure and the Gauge Needle will fall backwards slowly.

The other test you do is to slowly bring up the pressure to 200 psi below the the Opening/Pop Pressure and see if your Spray Nozzle will hold that pressure and count the drips. So many drips pre an amount of time are allowed.

Also it took me longer to compose and write this than it does for an experienced person in a Shop to test 1 Injector.

But, this is DIY and and I believe you can rebuild a good set of Injectors with the Liquid Filled Gauge.

It is great to have a Welder and a Lathe; and, any other equipment you can be creative with!

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