Injector pop tester - call it crazy but would it work? - PeachParts Mercedes-Benz Forum

ah-kay · #1 07-12-2011, 09:45 PM

If I can connect a hardline and a pressure gauge to the bleeding nipple port of a caliper, can I use it as a pop tester? It has a ready reservior of fluid and I just ask someone to pump the brake and I look at the pressure and the spray pattern. Would the master cylinder create enough pressure? Am I crazy?

When done, just bleed the brake and the car is good to go. It should be similar to doing a brake hydraulic pressure test.

1980sd · #2 07-12-2011, 09:49 PM

HE!! YEA IT'LL WORK!!!

KenB · #3 07-12-2011, 09:52 PM

isn't there a different resistance for popping brake fluid versus popping diesel?

ah-kay · #4 07-13-2011, 04:19 AM

Quote:

Originally Posted by KenB

isn't there a different resistance for popping brake fluid versus popping diesel?

No. Liquid is incompressible so both will pop at the same pressure. May need to add a check valve. In any event, it will be a while before I get to it as I have no need to service any injectors yet.

mach0415 · #5 07-13-2011, 04:23 AM

Quote:

Originally Posted by ah-kay

No. Liquid is incompressible so both will pop at the same pressure. May need to add a check valve. In any event, it will be a while before I get to it as I have no need to service any injectors yet.

There's ole Blaise Pascal's noodle working for us again.

wildest · #6 07-12-2011, 09:50 PM

Except that brake fluid has the wrong viscosity, you need diesel or a special oil to calibrate the injectors. Not a bad thought, though.

warmblood58 · #7 07-15-2011, 02:55 AM

Quote:

Originally Posted by wildest

Except that brake fluid has the wrong viscosity, you need diesel or a special oil to calibrate the injectors. Not a bad thought, though.

Ya, my thought too, pretty creative but not really practical -Could it be done, sure, but should it - prob not. Get an old bottle jack and make a cheap tester boy! Plenty of instructions on this site for that. Btw, today I was at Pacific Fuel Injection with Gus (A legend!) and he popped tested my injectors before my very eyes with his equipment (vast, tech, very complete while decidedly "old school" German in approach -perfect!) His Pop tester, while amazing was still something you could fabricate very cheaply on the fly, bottle jack, old injector line, gauge, and few misc hardware parts, sealer, etc

Good luck, keep that braking system out of this equation!

layback40 · #8 07-12-2011, 09:52 PM

You will need a very strong leg. No where near enough pressure.

mach0415 · #9 07-13-2011, 02:05 AM

Quote:

Originally Posted by layback40

You will need a very strong leg. No where near enough pressure.

Ditto. The question is rhetorical, since there are several factors, regarding Pascal's Law and how it relates to the pressures you are after. First, the average brake pedal has a 5:1 ratio of pressure out vs. in. So for $h!ts and giggles, 100lbs in = 500lbs out on the brake pedal to MC input piston. Add a brake booster and you have made it easier. Then, one must factor the surface area of the primary and secondary pistons of the MC to transfer into output PSI. Third, whatever the output piston is, overall psi is increased according to output piston surface area. A smaller piston acting upon a larger piston will increase pressure, but proportionately decrease piston travel. SO, if anyone is wondering if a MC could be used, then one might answer that question with a "maybe" depending on all these factors, piston sizes, fluid viscosities, etc. and pressure requirements of the pop tester. 3000psi is doable in a brake system. Diesel fuel WILL ruin a MC's seals. Could you build a hybrid system with glycol on the piston input side and devise an output side with a double seal with viton being on the diesel fuel side. As I think more on this, it seems like the hydraulic jack idea would involve less engineering.

leathermang · #10 07-13-2011, 12:04 PM

Quote:

Originally Posted by mach0415

... whatever the output piston is, overall psi is increased according to output piston surface area....

All the rest of the post was correct... showing that you actually did not mean to say that psi is increased...but that total force exerted by the piston is increased according to the psi multiplied by the surface area of the piston.

mach0415 · #11 07-14-2011, 01:37 PM

Quote:

Originally Posted by leathermang

All the rest of the post was correct... showing that you actually did not mean to say that psi is increased...but that total force exerted by the piston is increased according to the psi multiplied by the surface area of the piston.

That is correct. PSI would not increase within the hydraulic circuit. Force in terms of physical exertion by the output piston on something would.

whunter · #12 07-14-2011, 11:36 PM

Stressing the brake system.
Risking brake system contamination.
The risk of sucking air into the brake system.

It is cheaper/easier to buy or build a pop tester.

How to build a diesel injector pop tester
How to build a diesel injector pop tester

Finally finished my over-engineered pop tester!
http://www.peachparts.com/shopforum/general-information/251435-finally-finished-my-over-engineered-pop-tester-post2186902.html

power steering pump as injector pop tester
http://www.peachparts.com/shopforum/general-information/282524-power-steering-pump-injector-pop-tester-post2521649.html

Easy homemade pop tester
http://www.peachparts.com/shopforum/general-information/251436-easy-homemade-pop-tester-post2186930.html

Diesel injector nozzle POP test pump
http://www.peachparts.com/shopforum/general-information/213112-diesel-injector-nozzle-pop-test-pump-post1756633.html

.

ah-kay · #13 07-12-2011, 09:57 PM

A cylindrical cylinder of diesel can be put in line. If there is not enough pressure then all bet is off.

Came across this thread, brake pressure is in the order of 2000PSI. More then enough. If it is not a crazy idea then I will fabricate one, time permitting.

http://www.stu-offroad.com/suspension/bpress/brake-pressure.htm

79Mercy · #14 07-12-2011, 09:59 PM

HAHAHAHAHAHAHAHAHAHAHAHA no

Diesel911 · #15 07-12-2011, 11:13 PM

Let us know if it works!