Injector blowpast

[goosergus]

Hi agin all,

Sprinter 208d-ka. 1999

I had some blowpast on injector number three just recently.A friend helped with putting new washers on the injectors.
The forth injector would not budge so we left it.
The third one still blows despite its new washer.
The plan now is to get hold of a copper washer for the third injector because they apparently seat better.
My friend says the third injector was previously overtightened forcing the seat out of shape therefore allowing the blowpast.

Questions
Is using a copper washer rather than the original Mercedes washer acceptable?
Is there a better way of curing the third injector problem?
How can i safely remove the stuck solid forth injector?

 

[panason1c]

I'm not familiar with sprinters.. but if it's a CDI engine,

1/ I would ONLY use the washer specified by MB.

2/ Both seats (injector and cyl head) of the 3rd injector need checking that they are thoroughly clean and not 'pitted'........refit with another new washer, bolt and clamp, tighten to 7nm + 90 degrees (using an angle guage) .

3/ Try loosening the 4th injector retaining clamp and running the engine to its maximum working temp till the injector is pushed against the loosened clamp by engine compression.

 

[Aussie Nick]

If the thread on the leaky injector is damaged there is really only one way to fix it . Take the injector out and rethread by using a helicoil to seat the injector. If you follow this procedure then I would suggest that you throw out the old injector and use a new one as the thread on the injector is also damaged. I don't even think it is worthwhile rethreading the injector as it has been weakened by the damage, if this is truly the case.

You have to remember that the injector thread area is subject to piston ignition pressure and very hot exhaust gasses. I do not think using a copper washer will do the job here . Copper is too soft to withstand the blowby taking place.
I wouldn't risk the injector vibrating loose and punching a hole in your bonnet.
Use Rost Off Ice to soak the thread around the other tight injector. Rostoff ice is a marine grade loosening agent. If that dosen't work come back and will advise you of the only other way to get it off.

 

[goosergus]

Cheers Aussie Nick and panason1c,

My sprinter is not a cdi. Does advice still stand?

There are no clamps on the injectors.

Does the blowpast suggest damaged thread or couid it be just not seated properly? Certainly the blowpast only occurred after the connection for the fuel supply to the top of the injector was (in my opinion) overtightened

The fourth injector loosens slightly and siezes again. We are not even talking a quarter turn. Rather than push it too much we turned it back and then tightened again. Should i loosen it the bit i can apply the rostoff and then run engine to warm?

Where do i get a Helicoil? can i hire one?

When refitting the injectors my friend is setting his wrench to 70. 70 what i dont know. Does it relate to 7nm anyhow?

 

[panason1c]

Hi, Disregard most of what i said as it's a cdi..........apart from ......use only a MB sealing washer and checking that the injector seat and cyl head seats are clean and not pitted.

Your injectors are screwed into the head rather than clamped (as on cdi's) so ignore the 7nm i previously mentioned, yours will require a much higher torque.

The blowby is definately because the injector is not seated properly and this could be because of a stripped thread not allowing the injector to be fully tightened and/or due to the cleanliness/condition of the seats .

 

[Aussie Nick]

Helicoil is a rethreading system mainly used on crossthreaded or damaged sparkplug orifices. The system screws in to the old port a new metal or alloy thread to suit the spark plug thread. One of the specialist car supplier's in your area should have it and be able to advise you of the correct thread and material. As the screwing involves bits of metal being torn off You might want to contact a specialist rethreading company who will do this expertly for you as you may get filings going down into the piston chamber. If you take this option can you come back and tell us of the outcome?

 

[goosergus]

Hi and thanks again.

The third injector goes back into the port easily and tightens nicely to 70? on the wrench which is what makes me wonder if the thread is really damaged at all.

Anyone out there know the correct torque for the injectors and/or rethreading companies in south Essex?

We are having a go at the problems this weekend and i will report back.

Sorry Aussie but if i cant find a re-threader company is there any advice -other than extreme care -for doing it myself

 

[Aussie Nick]

I would get it done proffesionally . There is too much at risk.

 

[goosergus]

advice taken Aussie Nick

Thanks to all.

 

[exeng]

I assume tour Sprinter has the pencil type injector which is pre cdi if you have a wyco shop close by they sell the best release agent i have every used which may help with no4 as for the threads if you are getting the torque setting i would not think they are stripped but there are loads of different types of repair not just helicoil.

 

[goosergus]

Thanks exeng.

The mechanic today insisted that fitting a copper ring would be okay and under his gaurantee i allowed him to do so. The blowpast is no more.

The fourth injector isnt causing any problem at mo (other than not coming out) so i will leave it till it needs to.

 

[confused99]

hi there with regards to ur sprinter ive had this prob with injectors blowing and they get lots of carbon around them from build up where they leak. very strange way but i promise u it works!! pour a bottle of coke and pour it over and around the injector leave it 24 hours 2 soak and it will b 10 times better to get out. its worked for me many times ive got 4 sprinters . hope it works

 

[charlie3656]

i have just used steves services from extract, he is a wizard, saved me fortunes, he is the dogs give him a go, he wont let you down. 10 out 10.