Injector Cleaning by fuel additives?

Ben Swann benswann at
Sat Dec 6 15:10:47 EST 2003

They fail - slowly buyt surely.  Leakage occurs where the injector tip is
pressed into the housing - not sure of termnology here, but if you want to
spend your time verifying what I and others have seen:

Pull the injectors and pressurize the system with fuel.  You can then
observe the fuel weeping up the sides of the injectors over the period of an
hour or so.

I have even seen this in some relatively new injectors I purchased, but
without a doubt - if you have injectors with 100kmi on them, replace them.

Injectors will not be pressurized after leakdown just by running the pump,
as the airplate needs to be lifted to re-pressurize the lines - hence long
cranking times and even a no start condition may occur.

----- Original Message ----- 
From: "Louis A. Mulieri" <mulieri at>
To: "Ben Swann" <benswann at>
Sent: Saturday, December 06, 2003 7:12 AM
Subject: Re: Injector Cleaning by fuel additives?

> Hi Ben,
> I appreciate your words of experience. As you may have noticed,
> I'm a stickler for proving a component is bad before replacing/repairing
> it (I'm retired and with more time than money :-)).
> Your comment about leaking externally: **Does such leakage occur
> through the viton seals or is there another path?** I never considered the
> possibility and have not checked for it, i.e., I should be able to see
> fuel seeping out around the injector base??? **Or does it leak so slowly
> that it evaporates before making droplets?**
> Yesterday I cranked for about 20 sec when trying to start after a
> 70 min cooldown. I quit cranking and took out spark plug # 1 and found it
> to be totally dry. I will do this check again with more plugs checked but
> I reason that if my trouble is from flooded cyls due to injectors leaking
> into cyls, I should have heard at least cyl # 1 firing during my 20 sec
> crank. **Is this correct?**
> But now that you bring up the possibility that the no-start comes
> from empty lines due to fuel seeping to outside from leaky injectors this
> presents an altogether new situation. Help me with this please: I
> previously assumed that empty injectors would be filled by jumping the
> fuel pump relay to run the pump for a minute or so before cranking. This
> does not rescue the long crank trouble so I concluded that injector lines
> were not empty. **Is this a wrong idea that the lines will
> fill even if the engine does not start, perhaps because the air-flow vane
> has not lifted with engine rpm only at crank speed???**
> If running the pump cannot fill the injector lines without engine
> running I should be able to get the engine runing by jumping the cold
> start valve,** no?** I could run a wire from terminal # 2 of the CSV plug
> to front seat and momentarily ground it as needed to rescue a long-crank
> session.
> If this works I would invest in a fuel pressure gauge kit to measure
> residual pressure leak-down after warm engine shut-down to determine if
> the lines are emptying due to: 1. Leaky fuel pump check valve, 2. Leaky
> frequency valve, 3. Leaky CSV, 4. Leaky injectors. Would you agree with
> such an approach? I mean as a way to avoid the $300 + cost of replacing 5
> injectors and seals if they are not the cause of my trouble.**Reasonable
> approach**?
> Ben, I know I'm asking a lot of your time but I will be grateful
> for any spare time you can spend on this, and I will post a complete
> summary of the diagnostics path to the final solution on the Audi list
> once the trouble is found.
> Thanks,
> Lou
> On Sat, 6 Dec 2003, Ben Swann wrote:
> > Lou,
> >
> > They tend to leak externally - that is fuel goes from inside the
injector to the outside.  System pressure bleeds down and hard starting
> >
> > If you don't know the history of your injectors, it is best to just
replace them.  Although it is not an extremely difficult job, it is better
to just install new ones and be done with it, than trying to check for bad
pattern and leak - IMO..YMMV - but I have spent too much time in the past
t-shooting for/because of bad injectors when I should have just replaced
them at the outset.
> >
> > Ben
> >
> > [Hi,
> > I've had numerous suggestions from list members that my
> > long-crank, hot start problem could be due to leaky injectors. Has
> > found a fuel additive that corrects injecor leaks due to sludge-etc
> > buildup?
> >
> > Thanks,
> > Lou
> > 88' 5KCSTQ]

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