Professional Fuel Injector Cleaner

Today I made the trip out to the western part of the Montreal island, to a shop in Pointe-Claire, Lew Dieselec. They're a small shop with a handful of talented employees that specialize in fuel pumps and fuel injectors, mainly from gigantic vehicles like front-end loaders, trains/locomotives and heavy farm equipment.

I met with Stan, who gave me a full run down of testing and cleaning a set of used injectors - My newly acquired second hand Densos' were the subjects of our testing (These Denso fuel injectors were to be used on the R32 Skyline GTR 400whp Build car).

I compiled this 6 minute video which shows all the steps briefly, including the flow pattern tests, and output tests, but I'll explain in detail below...

I suggest watching the video first, and then reading the rest of the article

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Fuel injectors are an integral component of any engine, they are the "nozzles" that squirt fuel into the combustion chamber, which results in a small explosion, forcing a piston down (or a rotor to rotate), resulting in power generation.

Why Flow test injectors?
It's a good idea to flow test any set of injectors that has been previously used, or sat on a shelf unused for an extended period of time. Fuel injectors have a small apparatus that

opens and shuts very many times per second, and if that part gets gummed up with debris from contaminated fuel, or anything at all, the fuel injectors can become blocked, defective and leaky. This is bad for everyone because it means the car will run less efficiently, consuming more fuel, adding extra strain to the engine and even polluting the environment. (See here for Dyno Tuning with these Injectors)
For anyone with a turbo powered car, a bad set of injectors, or even just one bad injector could spell disaster and the end of your engine! if you don't have enough fuel while on boost then the engine will have a lean condition in one or more cylinders and potentially cause detonation, leading to total engine failure. The ECU will attempt to correct it by forcing more fuel into the chamber, but if the injectors aren't working right in the first place, then things will just get worse.

Thats why it is important to have your injectors cleaned periodically. Since by now, most everyone will be thinking: "Thank god I picked up that can of fuel injector cleaner at the store for $5.99" I of course asked the expert his opinion on those products. "Garbage, absolute garbage" he said, they're completely worthless and won't clean a damn thing inside the injectors. worse than that, on some cars they may even cause leaks as the chemical additives can eat away at gaskets, seals and rubber hoses.

Really, the only way to clean an injector is to have it cleaned by a professional, who knows what they're doing.
Fuel Injectors
Denso 660cc Fuel Injectors
Well, we did just that, with this set of Denso 660 cc fuel injectors coming second hand from Japan, they made a prime candidate for cleaning and testing, before I put them in my own car.

The serial number associated with these units is: Denso: 195500-0610

The first thing we had to do was to remove the black paint from the casing. They use an ultra-sound machine to thoroughly clean them and apparently the paint has adverse reactions to the ultra-sound. So using a wire brush wheel Stan removed the paint from all 6 and then washed everything off in parts cleaner, and blew them dry with compressed air.
Denso Fuel Injectors
Then he proceeded with a visual inspection of the micro filter, which is situated at the inlet side of the injector, they are very small and almost impossible to see inside the casing, but this is what they look like brand new, up close.
Fuel Injector Filter
Fuel Injector micro filter
Once all the filters are checked, and pass inspection (any that don't are replaced with new ones of course) he replaced the O-rings with new ones. This is such a crucial step that most people over look when installing fuel injectors, new O-rings will mean the difference between a good and bad seal. The cost for 6 of them is nearly negligible, so just replace them!
Fuel Injector O Ring
Injectors with new O-rings
Then, he installed the rig adapters onto each injector
Placing each injector in the rig, getting ready for the first set of tests
Fuel simulator for testing purposes
Fuel Injector Plug
Then he cleaned off any corrosion on the plug connections and secured the rig into position
Plugged the injectors into the wiring harness, and setup the machine
We ran through the first test, a spray pattern test. He awarded a rating of "Fair" only, because the spray wasn't as good as it could have been. The next test was a leak test, where the injectors are supplied with fuel but expected to remain closed and not leak.
Stan inspecting the injectors for leaks during the leak test
Up next was the volumetric flow test, usually he lets a set of injectors run for 30 seconds and then measure how much output it has had in that 30 second period. You're looking for all the injectors to have pretty much the same volumetric output (this is known as balance), and the output rate per minute can be obtained by multiplying the volume by 2.

Unfortunately because these are 660 cc injectors, they were flowing Three Times as much as the injectors that he's used to testing, so it filled up the cylinder very quickly. I also noticed the pressure he was running was near 37 PSI, so the fact that the pressure was different than what Denso suggested for testing (around 45 PSI) I knew that any static flow rate numbers we would get wouldn't truly represent what these injectors are capable of. Flow rates have everything to do with fuel pressure, if you have a lower pressure fuel supply, you can expect a lower flow rate, on the contrary, its common for people to increase their fuel pressure during tuning to squeeze more out of injectors also.

But that's ok, cause we weren't here to verify the rating of the injectors, just to make sure that they're operating properly, and that they are balanced within reason amongst themselves.

So, all that to say that the numbers we obtained for flow rates are Nominal rates, meaning they are not the real usage flow rates, but instead just what ever the injectors happen to flow using the lower pressure, and smaller time slots (15 ~ 20 seconds) so the cylinders didn't overflow.
Fuel Injector Flow Testing
First test results
No leaks, a Fair spray pattern and the following Nominal flow rates adjusted for a standardized time period:

  1. 125
  2. 122
  3. 120
  4. 121
  5. 120
  6. 120
So we've now established our baseline measurements. Next comes cleaning, this involves a 20 minute chemical bath inside of the ultra-sound machine, while hooked up to the wiring harness, which forces the solenoids' to open and close while bathing.
Fuel Injector UltraSound Cleaning
The result was a chalky white fluid leaking out from the injectors, and small dirt particles which began to float around. After the full 20 minutes was up, the water had turned from a clear liquid to a murky brown pond, seemingly filled with scum. I guess they were dirty after all... but theres only one way to know for sure if the cleaning made any difference in the end.

Second Test Results
the injectors went back into the rig where Stan re-performed the spray, leak and flow tests.
Fuel Injector Spray Pattern
The result was notably better, while there were still no leaks, the spray pattern had improved enough to warrant a grade of "Good", which is better than "Fair". But the true test of improvement would be the flow results; again using the same Nominal scale and standardized measurements we obtained the following results:
  1. 125 Increased to: 164 
  2. 122 Increased to: 160
  3. 120 Increased to: 158
  4. 121 Increased to: 158
  5. 120 Increased to: 158
  6. 120 Increased to: 159
Which is an astonishing 32% improvement overall.
Needless to say, the injectors must have been dirty inside, and the numbers speak for themselves, cleaning and testing resulted in a 31% increase in flow rate, an improved atomization spray pattern, and no leaks. 

We numbered the injectors in order of flow rates, so that I could put the highest flowing injector in # 6 cylinder to combat the common lean condition with the oem RB26 intake manifold. (If you're working on your engine, you might be interested in this article: Complete Turbo Swap Guide and Engine Externals Overhaul.

All in all I was very pleased with the quality of service, and the results. Never under-estimate the power of having your injectors cleaned and tested, it usually will make a difference.


  1. well written article!


  2. So to all of the "naysayers"out there that say a bottle of Chevron "Techron"will do the same thing.Think again.This is the real deal!!

  3. Thanks for sharing this informative post with us, it is true that dirty fuel injectors can decrease the flow rates which results in poor performance of the engine.

  4. Hello there, very informative indeed. I was wondering if we use those liquid fuel filter cleaners, do they work? If yes, which is good one? I have Mazda 6, 2.5L, 4 cylinder, 2010 model.

    Will appreciate your guidance, you could write to me on jfaijaz at gmail dot com.

    1. The liquid fuel cleaners do NOT clean anywhere near what a proper cleaning accomplishes and in some cases can harm your engine.

  5. Hey there, great reviews & very informative. I'm so glad I stumbled upon your site while searching for fuel injectors around Montreal. Do you mind if I ask how much did this cost? Thanks so much.

    1. Hey Sebastian, it's good value, generally it costs between $20 and $50 per injector depending on which service you go with.

  6. what is the name of the place?

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