With all of the issues with pinched lower o-rings I would like to test my new injectors in the rails before installing them in the car. I think it would be easier to test them with air pressure vs. hooking them up to the fuel lines and priming the pump. Is there any chance of damaging the injectors doing this as long as I keep the pressure under about 50PSI?

Heath

It's always preferable to pressure check with liquid so you could fill the rail with fuel and then apply air pressure on top of it.

Not that I doubt you, but why is it preferable to test with a liquid?

I had planned on putting a pressure gauge inline and then check for a leak-down. I have done this with plumbing in condos where it's critical to minimize leaking on a downstairs neighbor.

Heath

Study the molecule size of the 100's of different chemicals in gasoline [hint the avg is C6.8] vs Nitrogen [air].

If you use air test to 61.3 psi as the average psi as read by a gauge [43.4] does not take into account the peak when injectors are closed.

Peak is 1.414 x average just as average is 0.707 of peak.

I spent a couple of hours this afternoon putting together my "test kit" - some stuff that I already had in the garage and a ball valve from Home Depot. I'll post the whole setup when I get a chance to try it out.

My mega plenum order from IOS should arrive sometime in the middle of next week.

Heath

Q451990 wrote:Not that I doubt you, but why is it preferable to test with a liquid? Heath

I wasn't ignoring you Heath but I wanted to wait until I got back to work after a few days vacation to review the source of the info I gave you.

One of the safety courses I teach is Pressurized Systems Safety Training and in it I quote an ASME standard which states (paraphrased) "ASME Division 1 Systems are to be proof tested at 150.0% of operating pressure using non-combustible liquids; or at 125.0% using inert gases.....Liquid is to be used whenever possible".

I'm working with (Div 1) systems which operate in the 100's psi to 1,000's psi so my logic may or may not flow down to the 45 psi engine fuel pressure level. I didn't quite follow Tech's post either but I think he is saying that he pressure checks with air at about 150% (60psi). If you do decide to pressure check with a liquid maybe (flammable) fuel is not the best choice, especially if it leaks.

Q45tech wrote:Study the molecule size of the 100's of different chemicals in gasoline [hint the avg is C6.8] vs Nitrogen [air]......If you use air test to 61.3 psi as the average psi as read by a gauge [43.4] does not take into account the peak when injectors are closed......Peak is 1.414 x average just as average is 0.707 of peak.

In layman's terms Tech- which method is preferable? Air (at 125%?) or liquid (at 150%?). I'll be looking for your answer and some references from the ASME or ANSI standards in the morning.

A question- I have access to some good quality gauges at work that are being discarded. For measuring fuel pressure, can I use a gauge that's been used for air systems or do I need a gauge that's been used in liquid service?

in my experience--solenoid valves (injectors are a normally closed solenoid valve) are often leak checked with air (or GN2 or GHe) since there is an inherent margin---if it don't leak gas, it won't leak liiquid (molecule size as above).Goody, i'm thinking that AMSE proof would indeed be with liquid as you stated (usually pressure vessels would be in this category) since one wants to have an (semi)incompressible medium for proof.

proof vs. leak

Injector test companies use something nonflammable that is close in viscosity/density to gasoline...........

http://www.ecs.fullerton.edu/~...g.pdf

Thanks for the links and thoughs! I think I will try an air test at about 65 PSI. For the most part I think they will either be sealed or not. If there's a small leak that I can't hear, the issue will be more of figuring out if the leak is in my test setup or at an o-ring.

I will try to remember to take pictures of the setup and post everything here.

Heath

Since I replaced 4 injectors [May 15 driverside], I've been counting days until the other 4 started acting up. This week, one was 21 and another 15 ohms [others 13], so I used the BG fuel system to pressurize a used spare rail that has been unused sitting in storage for 7 years.............all injector were clogged to air flow used BG44k to finally clean them............pulsed with jump box battery. Made a mess with flowing 11 ounces pressurized with 60 psi.

The point is junkyard rails and injectors will need some serious work to get functioning.

Well, I finally put my test kit together and put the injectors in the rails. Mobil 1 10W-30 worked wonderfully as an injector o-ring lube! My prior experience using vasoline left me tightening them into the rails with the caps to get them to seat fully, but these went in snugly but solidly just pushing them in by hand. I don't know if that's a function of the different design (this is my first experience with the phase 2 injectors) or the fact that the rails are new. Deatschwerks sent a small tube of Superlube with them, but some of the later Nissan FSMs recommend motor oil, and that is a product native to the engine environment, so that's why I chose oil. I think it's more important to lube them with something vs. what that lubricant actually is.

Unfortunately I don't have the caps that hold the injectors into the rail yet - so I can't pressure test them. Here are some pics. of my test kit...

Parts of the test kit:From left to right:Quick Coupler filed down for output to fuel hose1/4" ball valve1/4" threaded extension threaded into 1/4" teeAir compressor quick disconnect.____

Close up of filed down quick connector... bad pic... sorry.

____

Hose with bolt used as a plug:

____

Whole thing put together:Notice that I had it in the wrong order before I put everything together. Now it's right.... quick connect > ball valve > threaded extension > tee with gauge > filed down quick connect.

The gauge is a part of a cheap-o fuel pressure testing kit from Harbor Freight - I think I paid $10 for it. Everything else is from Home Depot, except for the quick connectors, also from Harbor Freight.

The bad news is that I loose about 1PSI every hour at 70PSI. The leak is on the barb that I filed down at the output to the hose. That is a really tiny leak - had to submerge it in water to find it.

I have a fix for it, but it involves a hose and fitting from the NAPA fuel injector flush kit that I bought on eBay - so it won't be as easy to recreate. I'll post it after I buy a couple of extra fittings and have the whole set-up ready to go.

As a fun side note, I think I found a new way to easily get injectors out of the rail without damaging them. As long as you catch them before they hit the floor

I can't wait to try it with the old injectors and rails after I get them out of the car.

Heath
Modified by Q451990 at 12:16 AM 9/20/2008

Q451990 wrote:As a fun side note, I think I found a new way to easily get injectors out of the rail without damaging them. As long as you catch them before they hit the floor

Do I have the image correct? You're blowing them out of the rail with air pressure? Heheh .... POP!

Obviously the weakest sealed one goes first what do you plan for the other 3? Go slow with incremential psi.

The rail I was testing had one with no hold down cap nothing happened at 60 psi, but I didn't presoak them.

I guess they would have to be replaced one at a time... not ideal for cleaning the rails. Perhaps you could break them loose one at a time, lubricating and reinstalling them as they come out. Then they would be easy to get out by hand after getting them all loose with air pressure.

Heath

I found this TSB on general driveability issues.

http://www.q45.org/gallery2/d/...+.pdf

Check out page 6 of the TSB. It shows a graph of "normal" injector leak-down. My question is this... how can any leakdown be normal when the fuel lines are pinched off? Does the fuel have gasses in it that leak past the seals, making the liquid portion of the fuel in essence become more compact?

In any case I'm finally pressure testing my injectors, and they are following this graph exactly... 10PSI Per hour... My setup is far from perfect, but I think it can let me rest easy that there are no major leaks.

Heath

An injector valve is not as perfect as you think. The brand new spring may exert more closing force than the old used injector spring.

10 PSI drop per hour seems excessive especially on the old 90-93 design.

Since this was a 1995 it might apply to ONLY newer design?

fuel hose pinching pliers may not be the perfect seal you think, it might be wise to really seal off the inlet and outlet with a better system.

Thanks for the response. The last hour showed a drop of 6 PSI, but I started out at 65 PSI vs. the 40 on the graph. My test setup was leaking at about 3 or 4PSI per day after it stabilized - I saw pretty big swing (3-4 PSI in the first hour or two) I suspect due to temperature changes. I couldn't find the leak under water. I assume it wouldn't be wise to submerge the injectors and rails in water to look for bubbles?

I'll be interested to see how much they drop when the pressure gets down closer to 40 PSI, but there are just so many variables... four hose connections vs. 1 when I tested the set-up... plus a plug on the damper output for the right side rail...

In any case, I feel fairly confident that I don't have a serious leak-down issue.

Heath

Here are pics of the whole setup.





This is an adapter that came with a fuel injector flush kit I bought on eBay, with a cap from Home Depot. This would be the hardest part to recreate. I don't know if the fuel pressure damper would hold pressure or not.

Heath

You're hurting my pintle portectors!

They are there, are they not?

They are there... no damage done... I was gentle.

Heath