K-Jetronic Diaphragm / Rebuild Kit Failure.

High alcohol content in your fuel? Any additives used? I thought these kits have modern rubber that can withstand modern fuels, but maybe not.

 

Since you have it apart for the second time, would it be a good idea to replace the diaphragm with an original Bosch part? It will be more expensive, but you know for sure that it will work.

 

Can you tell us from who you did get this set ?! So, all other owners are warned...

 

As your seller said: looking at the picture, there is no hole in the membrane, so looks Ok. Remember that this membrane is meant to
1) isolate the upper side of the distributor that contains gasoline stored at system pressure
2) let move the teflon discs that do apply pressure on the injector "valves"

The deformation you see is just the required flexibility to let the discs go up and down. Looks normal to me.

As far as ethanol compliant seals for the k-jet, I've requested three sellers about it (even ferr400parts when he was still involved in this business), and only one(Savox) confirmed his products could accept ethanol. Bosh original products were not compatible. Did not ask DeLorean about their products.

 

Looking at the orifice at 2 o'clock on the last picture it seems to me you did not punch the diaphragm in order to properly line it up with the orifice that goes to the WUR.

See how was mine and how I fixed it.

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I If you had lost pressure on one injector, this might have been related to this membrane, but as you lost the whole bank of cylinders, I doubt this gasket is your problem: given how recent it is, you would not have experienced 6 sudden leaks on the 6 chambers.

With the K-jet, cleanness & pressures are the keys. So clean all the components then check flows and pressures "by the book". Your cars has been siting for several years, the most probable cause is that shortly after you brought it back to life some crude managed to get free and made a mess.

You should definitively proper line-up this hole as it is through this orifice that the metering head feeds the control pressure. A partial choke would not prevent the cylinders from firing, but as with everything related to k-jet: nothing is complex, but must be performed with accuracy.

 

Yes, if the WUR warm control pressure has changed from when the warm idle mixture was adjusted. Doesn't make sense to even attempt setting the warm idle mixture until you've confirmed that the WUR warm control pressure is in spec (and the WUR cold control pressure, too, as, if that is bad, you'd be replacing, or rebuilding, the WUR and that can have a slightly different, but still in spec, WUR warm control pressure).

 

Yes. WUP regulator can cause mixture issues. Bosch no longer services these parts. You are at the mercy of cheap garbage aftermarket junk that unfortunaly simply will not do the job. Short of a full conversion to EFI, you may find yourself in a battle to source parts for this once proud automobile.

 

For these and other reasons, I will NEVER, EVER, NEVER EVER, buy a CIS car again !!!!!!!

 

That’s exactly why I’m converting my QV to modern EFI as we speak. They are troublesome.


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I don't think so (as the pressure is OK and the fuel use at idle is very low). The symptom would be "insufficient fuel to run at very high RPM" for the reduced fuel flow volume. Are you using the smaller diameter 52mm, lower power/lower fuel delivery Bosch 0580464125 (Bosch USA 69435) CIS fuel pumps that many F part suppliers are now supplying? This post shows the difference between the stock 60 mm diameter CIS fuel pump and the smaller 52 mm diameter CIS fuel pump:

https://www.ferrarichat.com/forum/posts/148392020/

I.e., Do you have the zig-zag black plastic piece around your fuel pumps to fit them in their clamps?

 

My mistake -- I was thinking 400i, not 412. By "original" do you mean you know that they've never been replaced? Did you note the Bosch part number on them when you refreshed the rubber pieces?

Are both sides the same 700 cc3 in 30 secs? You could measure the voltage at the fuel pump terminals with the engine running vs the voltage at the battery terminals with the engine running to rule something electrical in, or out -- the voltage at the fuel pump might (would) be a little lower, but it shouldn't be a lot lower. (But I still think that this lower fuel flow volume delivered would have no effect on idle if the pressure is OK.)

 

Bosch do make these again, was advertised last year for the renault5 turbo that uses a k-jet.

 

And what about control pressure? Once the wur has received current for 5minutes you should have "hot pressure" as the bimetalic strip does heat it regardless of thd fact that the engine is runing or not.

Have you checked that the sensor works freely when the pumps are off. You did not mix plungers from one head to the other? (just sondering if the plunger works freely)

 

That's actually great news..they were unavailable for a number of years. I just hope they are made from the same material mix and not just pawned off to some offshore manufacturer.