If the body of a fuel injector is leaking (allegedly) and flooding a spark plug, there is any chance of fixing it cleaning the injectors or do I have to replace it 100%?

How can I determine which injector is bad (with DIY methods) ... maybe inspecting the spark plugs and find one that looks different?

2000 Peugeot 106 1.1 TU1JP (HFX) with Bosh 0280156025 injectors

  • Make model and year of vehicle?
    – Moab
    May 25, 2018 at 11:54
  • Peugeot 106 1.1 TU1JP (HFX)
    – Rhinoted
    May 25, 2018 at 16:06
  • What year is it?
    – Moab
    May 25, 2018 at 19:21
  • year 2000, uses Bosch 0280156025 injectors
    – Rhinoted
    May 25, 2018 at 22:24

2 Answers 2


You don't need to "absolutely" replace fuel injectors, if that is indeed your problem. From the description, you are suggesting the leak is incurring past the injector plunger and not from the fuel rail, so I'll take that tact.

The fuel injector in a gasoline (petrol) powered vehicle is a pretty simple device. Basically, there's:

  • The plunger which controls the flow of fuel (turns it on/off)
  • The body, which contains the fuel (gives it direction from fuel rail to combustion chamber)
  • A spring, which resets the plunger
  • Solenoid, which actuates the plunger
  • A nozzle, which atomizes the fuel

enter image description here

Note: These are the basic parts.

If an injector is leaking into the cylinder, the usual case is the plunger isn't closing correctly. This can be caused from the plunger getting gummed up and not closing correctly, which means it's not cutting off the flow of fuel correctly. It can also be caused by a weak spring, which allows fuel to bypass the plunger. Either way, you end up with excess fuel in the cylinder.

If there are just gummy deposits in the injector body, you can clean them. Carb cleaner can do this very well for you, but you need to actuate the injector to get the carb cleaner in there to clean out anything which may be causing issues. If you pull the injector out of the bore to clean it, you should consider getting a rebuilt kit, which in most cases gives your a new screen (located in the top of the injector ... if so equipped), as well as the O-rings. In most cases, you don't want to reuse the o-rings because they will tend to leak. If they are older, they will most likely tear as you try to put them back into the injector bore, even if you coat them with oil. Besides, depending on the age, newer o-rings will not be susceptible to getting ate up by ethanol.

You can possibly tell if there is an issue by reading the plugs. If there is one or more plug which is black and wet, this could very well be a sign the injector is leaking. This is not a given, as there is an art form to reading plugs. I talked about reading plugs in this answer.

Usually, though, if you have one bad injector (or one is leaking), you'll want to clean all of the injectors at the same time. This will help get them all back to a point more closely like new. If you do find one which is leaking, you should consider sending them to a professional who can do a thorough cleaning as well as check for wear, function, and flow rate. Sending them out is usually a lot cheaper than buying new ones and can get you just as good of results. It does, however, take a little time, as you are at the whim of the professional and their schedule.

Please note: The above is for basic fuel injectors. There are other types, such as what is used in Direct Injection (both gas/diesel), what is used in throttle body injection, and side flow fuel injectors. The above should give you an idea as to causes and how you might go diagnosing/resolving your issue.

  • Thanks for the exhaustive reply. The fact is that a set of injectors for my car is 50/100$ and I'm confident that I can replace it by myself without mistake.. Maybe the cleaning job and gaskets replacement won't be much cheaper (and from what you said I understand it wouldn't solve the problem if it is a weak spring inside the injector right?).
    – Rhinoted
    May 25, 2018 at 17:14
  • @Rhinoted - If you replace with new/rebuilt injectors, it would solve the issue if there was a weak spring inside. It won't solve any problem if the injector is NOT where the problem is at, though. You need to figure out for sure what's going on before you start replacing parts or you're just throwing good money after bad. May 25, 2018 at 17:29
  • The first time in the day I turn on the car, it idles fine but if I hit the gas it "soffocates".. after some seconds it starts to run fine. Now I cleaned IAC valve, throttle body and MAP but nothing changed.. the problem is very consistent and repeats always the same.. accumulated petrol from a leaking injectors seems a good candidate (also I noticed some graduality, if the car is stopped 2 hours the problem starts to appear, 3 hours is worse and so on ).. can you think of something else that could cause it?
    – Rhinoted
    May 25, 2018 at 17:53
  • @Rhinoted - I don't think it would point to injectors, then. If it was a leaking injector, it would be very hard to start right at first due to flooding of the engine as the injector purged all of the fuel pressure in the lines. it wouldn't start fine and it wouldn't idle fine until the excess fuel was burnt out of the system. Another thing is, some of the puddling gas would make it to the oil and would not only thin it out, it would make it so your oil was over full, and the oil would smell like gas (gas leaks down past rings and into the crankcase). May 25, 2018 at 18:09
  • I'll I have to investigate further then.. any advice?
    – Rhinoted
    May 25, 2018 at 18:22

Check spark plugs in any misfire coded cylinders, wipe the oil off the dipstick onto a clean paper towel, if it smells of gasoline, you very likely have one or more leaky injectors. Plugs fouled by a leaky injector will be darkened or if you catch them right away, maybe even wet and smell of gas, that's a pretty sure sign the injector is leaking on that cylinder. Look for gasoline or gasoline residue on the intake around the injectors in case the o-ring is leaking. It's odd if you don't have any codes, a code should have popped I'd think. When were the plugs last changed? Plugs can throw a weak spark even when they look "OK." Are the coil/coils all good?

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