divil

Anyone ever use one of these fuel injector testers?

I had my injectors cleaned and tested a few years ago but I'm having issues that could be injector related. I just did a test with that tool and got some strange results...I wonder if anyone can help me make sense of them. I pulled the rail and tested each injector 5 times, priming the pump in between, and catching the fuel in a mityvac container. I started on #4 and found that on each successive test on that injector, the pressure drop got bigger and bigger. On the rest of the cylinders, the pressure drop was even bigger still than what I saw on #4...but the volume of fuel delivered was less! That must mean there was less fuel in the rail somehow?

Rail pressure after a few seconds of pumping each time was 35psi. I didn't time exactly how long I left it pumping each time...but once it reached max pressure I thought that shouldn't matter.

The tester was set to do 50 pulses of 10ms. The average pressure drops and volumes in the tests were:

#4: 35 -> 6 psi, vol 18ml
#3: 35 -> 2 psi, vol 18ml
#2: 35 -> 0 psi, vol 14ml
#1: 35 -> 0 psi, vol 14ml

In the case of #1 and #2, the pressure reached 0 before the injector had even stopped pulsing, so the pressure drop would have been more than 35psi.

After these tests, I circled back to #4, and this time I got the same results as #1 and #2 (both pressure drop and volume). So why did I get less pressure drop and more fuel on the first 2 injectors, the first time around? For that to happen, there had to be a greater volume of fuel stored in the rail, the way I see it. But I can't understand how that is possible, unless there was air in there somehow.

It's freezing out now so I've stopped, but I will probably do more tests tomorrow.

EDIT...I think I must have introduced some air into the rail when I attached the pressure gauge. It seems that would be inevitable any time you open a depressurized rail. Maybe that air skewed the tests somehow. Next time maybe I should run the pump for a few minutes before doing the tests.

Tiger03447

Dear Divil: I looked at your link..and I haven't used one before, but I know that the ASNU machines used by FI shops measure pressure and quantity..you might try soaking the injector in Techron FI cleaner overnight to loosen any deposits inside...be sure that if you're testing the injector keep it away form the ignition wiring. You can also put a piece of white cardboard behind the injector while firing it and check the spray pattern, and that it cuts off sharply with no dribbles afterward...jus sayin..Thanks, Tiger 03447

divil

Thanks. I was just looking for 1 or 2 injectors that were noticeably different. My plugs seemed to indicate that #2 and #3 were running leaner than the others, especially #2. I have a new injector wiring harness so that only left the injectors themselves, but so far the tests don't back it up. I also tried using an infrared thermometer to check the header temperatures, but I can't get any meaningful measurements. At first it looked like #2 and #3 were about 200F hotter, but then I found that I can get each runner to show that variation after a few tries...it seems to be pretty random.

Tiger03447

Dear Divil: Most of the injector cleaners are based on stoddard solution, an old dry cleaning agent..It cuts loose all the varnish that builds up on the pintle and the collar that it seats on...sometimes in the FI shops they have to run the solution through the injector several times before the crap cuts loose..I know of guys that have soaked the injectors in it for over a month - totally covered- and have had some success...but that was trying to salvage old injectors...if they ohm out OK that means the coil inside is OK. there are very fine mesh screens inside the injector to keep crap out..some have two, others just one..they can get plugged also even with the extra fine filters we use in the gas lines,etc...depends on the design of the injector..then you are back to the white cardboard trick to check for the spray pattern..but at least it sounds like the car is running..BTW, are the plugs that were "clean & lean" really "white" on the insulators? Could it be antifreeze getting into the cylinders? check for exhaust in the water to confirm/deny...Thanks, Tiger 03447

divil

All show around 4.6 ohms which is correct. When I had them cleaned before, they did flow testing/cleaning/repalced filters, o-rings etc...all the usual stuff.

The plugs...of of them is very white most of the way around, there is just a small faint grey patch at the back near the ground strap. The other one isn't quite so clean, but it's close. I'll get good pics of them tomorrow and post them up. If it's anitfreeze it must be a tiny leak, but I suppose it's possible. I did a leak down test a few days ago and all were < 4%. #2 which had the whitest plug did have the highest leakdown (but we are talking maybe less than 1/2 a psi more than the others). But I didn't open the coolant because the engine was still a bit hot. I have a chemical block test kit, I might try that again.