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Discussion Starter · #1 ·
Injectors\' life span

Hi all,

Can anyone tell me the life span of fuel injectors(my is from 91 original). I'm not having any problems with injectors./wwwthreads_images/icons/smile.gif


Nycjeep :) /wwwthreads_images/icons/smile.gif/wwwthreads_images/icons/cool.gif/wwwthreads_images/icons/wink.gif

Discussion Starter · #2 ·
Re: Injectors\' life span

In my experience, they won't need replacing unless they are leaking or the electrical connector gets corroded. Some of our customers have over 250k without replacing them.

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6,784 Posts
Re: Injectors\' life span

Just because the engine still runs doesn't mean that the fuel injectors are doing great...
That is a myth, and someone needs to get the word out that FUEL INJECTORS ARE WEAR PARTS, and need to be serviced just like all other wear parts do.
They especially need to be cleaned on a fairly regular basis.

Ask anyone that has to deal with injector problems on a regular basis, and you will soon learn about the fuel they control.

Any petroleum based fuel has microbes in it, along with lots of other impurities.
Those impurities are the cause of most injector failures.

When GM first started testing fuel injectors, they put a couple of dozen test engines through what would normally be over a million miles of driving on dynos.

The injectors went what would have been a million miles of highway driving with no major problems.

When those same injectors were put into the first of the production engines, they failed in less than a year.

The reason, Pintle (Needle) and Seat failures do to "Build Up Of Foreign Material".

While on the dynos being tested, the engines were never shut off unless they needed maintenance. For those particular engines, that would have been 7,500 miles of highway driving.
To replace the engine when they wore out.
The fuel delivery systems were what was being tested, so they were reused.
The engines in testing were run nearly continuously with a very high grade of gasoline (scientific grade) that was filtered to a single micron...

Those engines were switched off an average of 141 times TOTAL in what would normally be 1,000,000 miles of highway driving.

The average passenger car in the united states is cycled (started and stopped) an average of 9 times a day, 144 times in 16 days.

The test engine fuel systems were heat soaked less than 16 days in the real world.

WHAT WENT WRONG, Failure Analysis, The short version...
(The reason, Pintle (Needle) and Seat failures do to "Build Up Of Foreign Material".)

Commercially available fuel is just loaded with microbes, hard and soft contaminants, corrosive solvents, and corrosive additives.

When an engine is started, driven, and shut down, the injectors are stopped when the engine is shut off.
Fuel return circulation to the tank also stops.
The injectors then heat soak, and so does the fuel in them.

The heat soak kills the microbes. The microbe remains (dead bodies) build up inside the injector, and harden.
During decomposition, they emit strong acids that can and will eat into the injector's components.
The hardened bodies are hard enough to dent and degrade the tolerances of the injector parts. The hardened bodies also act as an abrasive to wear away moving parts.

The resulting plaque then acts as catch net for more of the impurities and microbes, further compounding the problem.

While the build up was very slight, it was still enough to allow a small amount of fuel to leak past, resulting in a larger and larger amount of heat soaked fuel deposits to build up.

Injectors build up plaque on them, just like your teeth do... Or a coral reef builds up...

It is a really good idea to have injectors cleaned and flow tested about every 50,000 to 75,000 miles.

There are several ways to clean the injectors, but none really cost effective for most users.

I have seen very good results with an on car cleaning system, but the best way is to take the injectors out of the engine and have them professionally cleaned by a reputable and qualified repair or rebuild shop.

The on vehicle cleaning system I referred to is about $400, so if you see one of the $60 cheepies advertised, don't be fooled...
The on vehicle system is more of a maintenance procedure than a fix for injectors in bad shape.


If you have a THROTTLE BODY injection system,
1. Take the air cleaner off, and get a good view of the injector and throttle body.
2. Set up your timing light just like you were going to time the engine, but instead of connecting the pickup to the #1 plug wire, connect it to the coil wire.
3. Start the engine, and point the timing light at the injector(s).
4. Look for a nice even cone shape of fuel spray, with all fuel droplets being the same size.

There should be NO DRIPS, NO DROPS, NO OPEN SPACES OR 'TEARS' IN THE CONE. If you see any of these, there is build up in the injector, and it needs to be cleaned.


All port type injection systems have a fuel pressure test port on them.
It usually has a metal cap covering a valve.
You will need an adaptor for this valve so you can test fuel pressure...

1. Connect a fuel pressure gauge to the fuel pressure test port.
2. Run the engine a little while, and get a good working fuel pressure reading.
3. Shut the engine off while watching the fuel pressure gauge.
4. The fuel pressure should stay when the engine is switched off. This means the injectors are not leaking.

If the fuel pressure drops to little or nothing when the engine is switched off, there is a good chance that....
This means the injectors are dumping raw fuel into the intake, washing down the cylinders and filling the crank case with explosive fumes, not to mention diluting the oil every time the engine is turned off.
This situation needs to be corrected IMMEDIATELY.

If it's a leaking return fuel pressure regulator or some other problem, also inspect the injectors out of the vehicle while working on it...


Hope this helps clear things up...

"I Have The Body Of A God... Buddha"
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