Injector Check Tips

Determining if you have dirty injectors:

Tools needed: Fuel pressure gauge ( I took off the fuel rail cap and took it to an industrial hose supplier that made my 6 foot test hose. They swaged a 90 degree fitting to one end of the hose for connecting to the rail and a fitting & for a 100 psi gauge at the other end. Cost was less than $25 with the gauge.) 

Procedure: Install gauge on the fuel rail, start the car, have someone watch the gauge then go to the back bumper and unplug the orange connector for the fuel pump. The car will run for a little while on the fuel in the lines after the pump stops but when it stops will give you an indication of whether your injectors are clogged or clean. If the car dies before the fuel pressure drops to 30psi, you need to clean or replace the injectors. I've performed this test on a dozen or more cars and have found that with good injectors, the engine will continue to run at 30 psi or lower. Some cars I've tested died as soon as the pump was unplugged indicating the injectors were severely clogged. 

Injector Leak Check 

(injectors not installed)

A few years ago, I bought a set of used injectors for my Turbo Trans Am and wanted to be sure they worked leak since they had been sitting for several months. I didn't want to spend $15 each to have them flow tested so I came up with this method to verify that they fired and didn't leak 

Tools Needed: Battery charger, Test leads, fuel rail from a FWD salvage yard car or home made injector cap. 

Having a lathe, I made up a cap to slip over the top and test each of the injectors for leaks and flow. This in no way insures anything but that they do spray and probably don't leak. If that suits your needs, you can read on further to see how I checked these used injectors. 

First, I machined an aluminum cup on my lathe. The inside diameter being slightly larger than the injector end with enough clearance to allow me to force it over the injector O-ring. This was just going to be a quick & dirty kind of injector tester. It wasn't much trouble to hold the cap on the inj. while doing the test so I didn't bother adding anything to it that captured the cap on the injector.

If you want to use a fuel rail for the test and can pick one up cheap at the salvage yard, there are 2 options for using it. Either plug all but one of the injector bosses and the outlet with JB Weld or saw a section containing only one boss off the rail and cap one end and JB Weld whatever type of liquid supply fitting you want to use into the other end. 

The procedure that follows will have to be modified to suit your choice of injector mounting hardware but it gives the general idea of how you can do a quick test on injectors. 

After machining the cap, I drilled a small hole in the top and used epoxy glue to secure one of those little red tubes from a can of carb cleaner into it. To that tube, I connected a section of small vacuum tubing. At the other end of the vac tubing, I inserted another little red tube which fit nozzle on the can of cleaner.

That's all there is to the hardware and for the power source to fire the injectors, I connected alligator clip test leads to my battery charger. I used it on the 6 volt setting but it will probably not harm anything at 12 v for no longer than it will be used.

To run the test, I held the cap tightly on top of the injector, attached the test leads to the injector terminals and pressed the spray nozzle on the solvent can to fill the hose then switched on the battery charger to fire the injector. If you use about 3 feet of hose, you'll have plenty of fluid spraying to get an idea of the spray pattern.