ianbsears

Hi everyone,

I have 1 or more faulty fuel injectors. I am curious if you guys would recommend having all of the injectors tested and cleaned, replacing any faulty ones or simply replacing all of them. While I don’t really want to spend money where I don’t need to I also don’t want to do this multiple times if injectors are known to fail or if folks on the forum have any intel on testing and cleaning that would suggest that it is penny wise and pound foolish.

thanks,
Ian
92’ 964 Turbo, Polar Silver

peterpullin

replace!

but: you have to check flow and spray pattern mounted to your system.
mount each injector to the fuelline you will use finally for it. then see if
flow is equal or not.

dead injectors can be a follow up of a damaged fuelhead too.
if there is too much difference in flow it is time to have a look there.

and do not adjust fuel head if you do not know what you are doing.
that can damage the whole thing…

wicks

Injectors die of old age as well as the other causes. I replaced my injectors with new and rebuilt my FD with a kit. Works amazing.

ianbsears

thanks guys. i’m 3 for 3 on that question. i’ll replace!

Ian

ianbsears

@wicks whats a FD?

wicks

This genius piece of hardware sitting on top the engine http://www.autoatlanta.com/porsche-p...section=107-15

wicks

Peter: I did not do this step. I wonder if my motor is wearing unevenly.

peterpullin

i did this step after rebuilding the fuel head. there was a difference of about 7% fuel with the new injectors. i adjusted that and tried agian without injectors. the difderence was horrible. so this can not be wrong to do so. i still do not understand why this happens. in my case it worked out fine.

this test is useful to find out if this brand new injectors work. there is stories that two of six were not working properly and needed to be replaced.
not the quality we know anymore...

it is not the wear in the engine. if it is only few percent: that is fine -nott perfect but fine. the risk starts with one injector that delivers more or less fuel in a range of 20% plus. then you get too hot or wash the oil away. both results in $$$$$$$

ianbsears

@peterpullin @wicks Is the difference in fuel flow to a specific injector a function of the FD or the fuel injectors or both? I am asking b/c the schematic you sent a link to looks as though the fuel would flow evenly to all 6 injectors by virtue of how the FD is built (FACT - I'm no engineer). I think what you are saying is that despite the fact that I might buy new injectors I shouldn't expect them to flow evenly. Is that correct? I think rebuilding the FD and adjusting it might be a 400 level class for this 200 level student

Just ordered my injectors and o rings.

Thanks,

Ian

peterpullin

if you rebuild your fd and do not touch the adjusting screws nothing should change.
but you never know if someone did in the past. the adjusting screws are ealed with rubber rings too.
if you change that (bone hard in my case) you have to remove this screws.
before you do so measure the depth of the screws individually from the underside and note the values.
i do not remember at the moment. i used a digital tire tool and a ruler. that does what it should

the fd delivers much more fuel than needed. so without injectors the flow is higher through the
lines. the injectors block the free flow and deliver a different result. especially the adjustment
is way different. minir changes are enough. without injector it is almost impossible to adjust for
a final result

urquattro20Vt

It’s hard to argue against replacing 30 yr old CIS injectors. However when I had my engine rebuilt at 95k almost 3 yrs ago I had them tested and cleaned and retested. All but one were functioning as designed. So I replaced that one injector. It’s also easy to assume just because a part is 30 yrs old it needs to be replaced. For me I try to strike a balance. Where’s the balance? I guess each person has to find their own.

Brandon
’91 Turbo

wicks

It's prob not a meaningful concern regards the flow - and if your FD isn't at issue, ignore it for now. You're right re the design - if one flow balanced a very uneven delivery they would be compensating for something else wrong in the FD, an injector line, a fitting, a split oring, etc. If the system and control fuel pressures are good, and you don't have any crud blocking flow in the fuel system, and you have new (clean and springy) injectors, you should be able to run close to optimum power.

ianbsears

Hi everyone who replied. Here is the update - i bought new injectors and went about installing them myself. Had some issues and ended up bringing the car to an independent shop (S Car Go in San Rafael, CA ). They tested and cleaned the old injectors and opted to use them but replaced the injector blocks with aluminum ones (painted them to look like the stock plastic). They did find the intake manifold was loose as well as a number of oil leaks. They also adjusted the mixture which was running rich. Car is back and runs like a champ.

urquattro20Vt

Cool. Thanks for the update. Always nice to hear closure. Yeah those injector blocks have caused issues with a few people. Guess I was lucky in that mine were tight and not cracked or broken.

glad to hear the car is running well. Hope you put some fun miles on the car.

Brandon
’91 Turbo

997 tt/rs

Guys, but this is not a real injector, this is the metal pipe in which the fuel is pumped by the injection pump. What can break in such a metal tube?