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Armstrong Injector Pop Tester

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Old 02-26-2018, 06:45:25 AM
monkey551 monkey551 is offline
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Default Armstrong Injector Pop Tester

Hi All

Not sure what I really have here, I believe it to be an injector nozzle pop tester that I found in the back of the shed. My old man can't recall where it came from.

I've partially stripped it down and cleaned it and put in some fibre seals where there was old ones.

Anyone have any info on these? Would love a schematic/parts diagram but I believe the chances of one of those is slim to none.

Got a couple issues, one the gauge is stuck at north of 2000psi and that that it won't hold its own pressure. Can't see it leaking anywhere but presume its more in the piston area deeper inside which I haven't stripped down yet.

Pictures speak words so have a look and if anyone has any thoughts, let me know.


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Old 02-26-2018, 08:10:59 AM
Thaumaturge Thaumaturge is offline
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Default Re: Armstrong Injector Pop Tester

Can't speak about this model in particular, but many older pressure gauges I saw inside at various calibration labs I worked at had bent chambers inside with precision gear trains driving indicator needle. Stuck needles were often caused by a bit of grit stuck between these tiny gear teeth. To unstick them, with back of gauge accessable, you had to apply higher pressure than needle stuck at then spray solvent cleaner into gears to wash away any grit.
At 2500 PSI I'd wear a face sheild and heavy gloves. Gauge could be pressured with hand hydraulic pump such as used on power rams. In the lab the techs used dead weight testers. You could maybe build one with long screw thread driving oil inside longer threaded collar screwed onto base of gauge. First step would be to remove valve from rest of assembly to both eliminate possibility of trapped pressure, but to also reduce volume of oil needed to pressure gauge enough to dislodge any grit.
Hope this helps.
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Old 02-26-2018, 10:06:25 AM
Combustor Combustor is offline
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Default Re: Armstrong Injector Pop Tester

The gauge is a surface mount type, so obviously not original. Outlet fitting has been brazed on, so seen a bit of a hard life. If snubber valve and outlet pipe are both open, then no chance of any trapped pressure. Gauge may have been way over pressure and simply skipped a number of teeth on the gear quadrant. Bourdon gauges are fairly simple. Take it apart and run the gear back past the end of the quadrant till the needle sits close to zero, then either bend the pointer a bit to reach zero, or pry it off and re-fit on zero position. You can get a rough check if you have an injector that pops at a known setting, and your gauge agrees with it or indicates a known error in its working range.
May be able to adapt a hydraulic gauge , anything over 3000 psi is enough for setting most injectors. You have a fairly common British tester, think mine is labeled CAV, but am sure they were sold under various brands. Not worth investing a lot of time and money, as cheap units are out there on the net, and good enough for casual use. Have fun with it anyway. Regards,
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Old 02-26-2018, 03:33:52 PM
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Motormowers Motormowers is offline
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Default Re: Armstrong Injector Pop Tester

Last year I bought a new pop tester off Ebay with a huge glycerine filled gauge for $150.00 from India. Its a Bosch copy. I used it to set the pressures on the new nozzles I installed in my Mazda diesel and also my Mercedes 240D and 180D and it worked perfect. A shop wanted $125.00 just to set the pressures on the Mazda nozzles. Now that I dont need it I'll list it on Craigs and prob get most if not all of my money back on it. Beats wasting your time with all those Youtube videos I saw of trying to build your own with a bottle jack and parts. Found the shim assortment on Ebay at the same from India for $35.00. Both had free shipping. I have to laugh at lots of these kids on Facebook VW or Mercedes diesel forums that are of the opinion nozzles dont have to be pop tested after installing or shimmed up or down. Their cars prob nail so bad and they think thats normal lol
Remove the all rotten apples out of your basket of life and toss them in the trash where they belong.
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Old 02-27-2018, 09:18:01 AM
Combustor Combustor is offline
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Default Re: Armstrong Injector Pop Tester

No valves missing that I can see. Snubber valve isolates the gauge from the pump and injector is then connected loosely and pump is operated to fill test line with fuel, then tighten injector connection. Another few strokes should fill injector and should then spray. Pump steady strokes and compare spray pattern with makers manual. Then open the snubber valve a very small amount till a fairly steady pressure is indicated when stroked slow and smooth. Snubber stays closed down enough to damp heavy vibration which can damage gauge internals. Set injector to correct pressure and then wind out the snubber another turn or so and pressure will drop away safely before loosening test line connector.All fairly simple with a little practice. Regards,
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