Author Topic: Copper shims (Read 3250 times)

web · « **on:** October 16, 2007, 11:38:40 am »

Hi,

Long time no post ; I was active in the IDI section a while ago. Now I'm back and surprised to see my account still exists

I'll re-introduce myself properly elsewhere. But I have a burning question...

The copper sealing shims that sit under the injectors of my DI Fiat are no longer available from the dealership. BTW my injectors are identical to VW TDI injectors. Now a diesel shop nearby said he could get any shim for me, but he needed to know what thickness I need. He told me these shims are extremely critical because they determine the position of the nozzle in the combustion chamber, apparently quite important for proper burn. He also said I really need to have the original thickness, down to a tenth of a mm (that's about 4 thou). He told me if shim thickness was even a little bit off, causing the nozzle to sit a tad high or low, I might burn holes in my pistons.

So I want to know - is it really that critical? Also, is there any way of finding out what thickness my head needs? The head is off the engine because I'm halfway through a BHG repair. So I have access to all sides of it, if necessary.

Unfortunately I don't have the old shims. They were thrown away when my injectors were rebuilt - by same diesel shop

Also, the dealership doesn't have any specs of the shims, besides their Fiat part number. Browsing the EPC DVD, that Fiat partnumber turns out to be specific for the first three model years of Croma - no other cars. So I'm kinda out of options here... Any ideas?

jtanguay · « **Reply #1 on:** October 16, 2007, 02:01:24 pm »

he's right... the injectors could burn holes in the pistons and the position is critical.

the piston will always reach a certain height, so if you get a thin shim, the injector will shoot diesel even deeper, and if the stream hits the piston, eventually it could make a nice hole.

however if you get a thicker shim you should be fine, within a mm or so. maybe the car just won't run as smooth as it used to???

web · « **Reply #2 on:** October 17, 2007, 12:35:45 am »

Thanks - so those horror stories are true then. Not just for high pressure common rail injectors either? (mine open at just 250 bar which is pretty low for direct injection - then again, it's the very first generation of DI in passenger cars... same year introduction as the Audi 100 TDI.)

To know what's thicker or thinner than stock, I'd have to know stock size first though

Go way too thick and the stream may hit the head? Dunno, but the injectors don't sit completely straight up...

Right, I may have to go find the same car in a junkyard then, pull an injector and check shim size. It may be a hens teeth search though, cos these cars are becoming quite rare and I'd need one of the first three model years, because injector and shim were changed after '92.

lord_verminaard · « **Reply #3 on:** October 17, 2007, 07:11:01 am »

Are the injectors and shims available after '92? Is it possible to swap them out to the newer style? Just thinking aloud. Sounds like finding an old shim is your first order of business though.

If you can find a complete set of old shims, they can be re-used by heating them up with a torch until they glow red and then quenching them in water.

Good luck.

Brendan

web · « **Reply #4 on:** October 17, 2007, 11:25:17 am »

Can't change to later style, because they rely on a different shape piston (chamber) as well.

I found a diesel shop that appears to have the bosch # for these shims, I'll have him verify if they are early or late style though.

I heard about the torch method of reviving copper seals before, though I'm hesitant to try it out on such critical seals and risk my newly rebuilt injectors... I better get new ones and save the experimentation for some other place. BTW what's a sensible tightening torque for injectors?