924Board.org

[924RACR]

To save you guys the wait for me to format this and test it and include on the main website, I'm going to post this procedure here for you to try out if you feel desperate or daring.

Now with the disclaimers. Don't do this if your car is running OK!!! This is a last resort to an expensive rebuild. No warrantees, express or implied, about how well this will work or how well this procedure applies to your car. You may have no success whatsoever. I have not tried this at all, though it does come from a reliable source - thanks to David Grant, of Edmonton, Alb. YMMV, do it at your own risk, if you have problems with it, don't expect me to bail you out, I haven't done it yet either. Last time I tried to fix a rusty fuel distributor, it leaked, I gave up and swapped in another. I have yet to find the time to try this again. Leave me alone.


Again, as noted at the end, don't do this if you can at all avoid it. If you run clean fuel, change your filter regularly, and run fuel injector cleaner regularly (at least twice a year), you can be spared all this.

----------------

First sweep a place in your driveway or garage. You will drop something, and
must find it the same day! If you do not have great confidence, a plastic
drop clothor a sheet of cardboard might be good as a "parts catcher".

Remove the air filter, the big plastic duct that carries dirty air to the
filter element, and the tube from the fuel metering area to the intake
manifold. Now the fuel distributor and its plastic mount are all lone.

Draw a diagram of the dist and all its lines. Put a taped or wired label on
each of the 4mm lines attached to the dist. Each must have a consecutive
number. Show each item and its number on your diagram. There are about a
dozen banjo bolts lines attached to the fuel-distributor. Remove them all.
Do not loose any of the little copper or copper or aluminum washers; if you
have new ones, fine, get careless! Put a banjo bolt into each of the holes on
the top of the unit (these are the connections that go to each intake port.)
If you do not, a little (2mm by 8mm) filter could drop out of the port!
Put all parts on a clean magazine or paper. Clean cereal bowls are useful if
your spouse does not mind. If you do this kind of repair a lot you will have
a supply of nice clean margarine tubs just for the little parts.

Remove the 6 bolts holding the (metal) air metering housing to the plastic air
passage. Put the thing on a clean newspaper, on a table. Do not take this or
any fuel indoors. Undo the 3 bolts which hold the fuel-dist to the air
metering unit, with a flat blade srewdriver. Do not drop the (half inch by
1.5 inch?) fuel metering rod. It will want to fall out the bottom of the dist
housing. Turn the unit onto its side until the rod has been removed.

Remove the 8 torx bolts which hold the two halves of the dist together. You
may have to shock the two apart, with a 6 OZ hammer on the side of one piece.
Keep it upside down (the 4 inj connectors downwards!) There will be 4 bent o
rings and a diaphram that will want to fall under somewhere hidden. There are
also 4 metering/ pressure relief assemblies which might jump out. When
putting them back in, the steel ring goes in first, then the spring then the
aluminum ring. The cone shaped surface of each piece goes toward the
diaphram.

When you have the central metering rod in a safe place, and the "head" removed
from the "block" you can remove the 19mm nut that holds its slotted holder in
place. When the nut is mostly off, hit it with the little hammer, to
dislodge it a few mm, then remove the nut and its lock plate/washer. There is
a fine screen on this tubular rod holder. If it is dirty, it can be freed
from the slotted metering cylinder by carefully removing the snap rings. It
can be cleaned with a toothbrush, and solvent. There are fine screens in each
port below the banjo bolts to the 4 injectors. Test those by blowing or using
a tiny amount of compressed air. They can be removed, but need not be, if
they flow lots of air. You should be able to see a line of light through each
of the 4 main fuel-metering slots (each about 6 mm long and very narrow. If
the 4 slots are uniform in width and clean, and the big screen and the 4
little ones are all in good shape, you need to put this together again.

The metering cylindere is straightforward; if you rotate the fold/ lock washer
you can re-use it. Be reasonable in torquing it down.

GLUE: You should put a very tiny amount of a low viscosity fuel-resistant sealant,
like Permatex aviation form-a-gasket, on the perimeter of the thin stainless
steel diaphram. If you do not, taking it apart again might be simpler, but
the chances of a leak are significant. Any leakage will be evident as a
wetness when you are all done. You must not use more than a few (5 to 25?)
thousandths of an inch of sealer, by a few mm wide; the sealant line must go
between the fuel-filled parts and the bolt holes/ outside. It must not go far
from the bolt holes and the perimeter. it must not go near the tiny central
passages or the 4 aluminum pressure control/ relief valve/ orifices. You must
use a little tapered object to center the diaphram (it is symetric EXCEPT for
a little bleed hole, which lines up with larger holes in both the head and
block castings) on the lower housing. A stick pen may work well, pushed
gently into a couple of bolt holes on opposite sides. The holes in the thin
steel are the same diameter as those in the castings, so this centers it well,
perhaps after a few repeats to be sure.

Then you must put the 4 curved o rings on the little sheet steel guides in
the oblong holes at each fuel-metering slot location. If they are too hard,
use ordinary fuel type o-rings of the right thickness; ring ID is of less
importance. The sheet-metal guides can be removed, but again, why bother.
Before you put on the glue/ sealant or start to reassemble the unit, assess if
it is perfectly clean. If in any doubt, brush all parts in very clean
solvent. For rinsing, paint thinner or unleaded fuel work well; it must be
very clear (i.e. grit free). A fume hood is good for this, as are rubber
gloves. I find that stirring the bowl of solvent with the part is effective
at getting all the grit off. If you skip this step, you will get enough grit
on the metering rod etc. to make things stick. They will not tolerate even
invisible dust. You cannot do this assembly on a windy day outside, as there
is too much grit in the air.

Anyway when the diaphram is perfectly centered, and the curved o-rings are in
place outside each slot, put a thin film of grease on the outside of the 4
o-rings. A microlitre (one cubic mm) of grease should be enough; 10
microlitres is a bit too much.

Now put the lower housing onto the top one, which I have called the "head".
If you do not keep the top one inverted, all its little aluminum rings will
fall out. If you are working in the dark, or over the lawn, you are now
toast. If you drop a piece on a clean sheel of paper, no problem. Don't
get upset at this point, 'cause I told you so!

When the two pieces are together, put the little torx bolts in place. If they
do not fall freely until they are most of the way in, the diaphram may have
shifted; check it for position. Do not torque it if offcenter; you can easily
crimp the diaphram around these bolts, crimping it, and making sealing very
difficult.

Wash the central metering rod, then put it in wet. It should slide in easily,
but only when very exactly centered. Use force less than 3 times its weight,
i.e. very light force! Do not let it fall out. Work over a soft surface,
like vinyl or wood/ carpet, just in case you drop it.

Reassemble; put new copper gaskets on each side of each banjo; old ones can
be used if they are perfect you you have no choice. Do not overtighten the
banjos, as they can be damaged. If a few foot pounds are not enough to get a
seal, you need to buy some new copper washers.

Mount the fuel-dist on its aluminum air metering buddy. A new oring between
the two will keep dirt out of your engine, if the old one is too thin and
tired.

The gasket below the air metering aluminum unit is also to keep dirt out of
your engine. The gaskets between the air metering unit and the intake valves
also keep the mixture from going offspec, including the fat little orings on
each injector. The various large air hoses and teh plastic pieces they clamp
over must all beb nearly perfect. Silicone or other sealant can be used to
corrrect any gaps you find, if you cannot get replacemernt (used) parts. Keep
in mind that VW (and Volvo, and Audi, and likely a lot of other cars...) used
very similar CIS parts. Your local auto wrecker might sell you an extra set
of injectors or a fuel distributor very cheaply. Odds are the head will be
identical; the metering cylinder might be different; the metrering rod on the
VW unit I found was identical. The VW base casting was quite different from
the 924 unit, so I used the VW "head" and diaphram on a 924.

The injectors should be easy to pry out with a small "heel" pry bar. When
they are out, the little nylon injector seats can be checked for tightness
with a 12 mm allen hex wrench. If the o-rings are not really soft and round
in cross-section, get new ones. Installing the o-rings on injectors, or
putting the injectors into the engine will go easier with a drop of oil or
grease spread on them.

You can test the function of the injectors in a 944 or 924 by removing them,
pointing them slightly upward, and out of the engine bay, and cranking the
engine. It is good not to have any sources of ignition; cut 12 volt power to
the ignition, and take any other precautions. There should be a nice full
cone-shaped mist from each one, continuously for a 924 and intermittently for
a 944. while cranking the engine. The spray should get bigger if a 924 air
metering plate is manually raised (by reaching in past where the air fulter
should be!). For a 924, with the throttle closed, starter NOT cranking, and
fuel pump running, there shoudl be no fuel spray out of the upturned
injectors. If there is fuel running out of 1,2 or 3 of them, or if there
might be dirt or corrosion in the metering fuel distributor unit, you may be
justified in taking it apart. If there is fuel spraying out of all 4, it is
likely that the metering rod is not in its lower position. If it is stuck,
you will have to take the fuel dist apart. I have successfully hammered out a
fuel metering rod that was very badly stuck, AFTER the "head" etc. had been
removed. I was lucky that the parts were still perfectly shiny when it was all
apart; no corrosion.

You might just want to do all this 'cause it is a challenge. I wouldn't
unless there is evidence of a problem inside it.

_________________
Vaughan Scott
Webmeister
'79 924 #77 SCCA H Prod racecar
'82 931 Plat. Silver
#25 Hidari Firefly P2 sports prototype

[levans924]

I appreciate the info 924RACR, hopfully this weekend i will be able to do the rebuild.

[teo]

Illustration:

[Lizard]

I am glad I haven't taken that apart I like taking small things apart but damn that is just messed

[Diesel]

You should see what's inside the average diesel injection pump, it's a lot more complicated than k-jetronic.

[Lizard]

no thanks I don't like diesel engines

[Min]

has anyone done this successfully?

Min

[dpw928]

Haven't rebuilt one on a 924, but I did rebuild the distributor on my 928 euro. As mentioned above, be careful with the sealant. I tried the type of loctite mentioned in PCA's UP FIXIN V but it either leaked or plugged a decoupler orifice. After the third teardown I tried an OLD trick they used for stamped steel head gaskets used on flat head engines. I coated both sides of the steel gasket with wheel bearing grease. No plugs or leaks in the two years. For the o rings I found an A/C assortment pack at the local parts store which had all the sizes needed.

Another problem I had was making sure the holes in the cylinder matched up with the metering slits in the head. Recommend the orientation be noted/marked prior to removal of the cylinder.

Great write up Vaughan!!!!!

Dennis
_________________
81 931 5 sp
78 928 5 sp Silver
78 928 AT Euro Black

[Min]

thanks for the tip. looks like I'll be doing this in the next day or 2 .... so any further suggestions would be awsume.

Min

[924RACR]

Cheers, but it's not my write up...
_________________
Vaughan Scott
Webmeister
'79 924 #77 SCCA H Prod racecar
'82 931 Plat. Silver
#25 Hidari Firefly P2 sports prototype

[CMXXXI]

My fuel distributor is also toast. I backflushed the unit by removing the control plunger, then using a syringe hooked up to a banjo bolt I could squirt solvent from the outlet port backwards into/through the head. This dramatically increased the fuel output through the unit, but when I tried to run the car it was still a no-go. Again the best I could do is an idle. I've had an on-going thread about my continuing CIS problems, and have decided that a new/rebuilt head is required.

I remember this rebuild procedure write-up from last October, but decided that having someone who knew what they were doing rebuild the unit would probably be the best thing to do. Prepare yourself for huge sticker shock if you try and buy a new head from the dealership or aftermarket source.

I did however find someone to rebuild my 931 distributor head for a mere $320. If you missed my shameless advertising plug in Capt EZ's "Parts Source" thread, check out http://www.specialtauto.com/delorean-parts/fuel-distributors.html. He also handles Bosch fuel pumps, filters, WUR, injectors, etc. The guy is a car-cousin of ours, but on the DeLorean side of the family. Exchanged several e-mails and a couple of phone calls with him, and he sound like he's worth doing business with. I'll let everyone know how things turn out in a couple of weeks.
_________________
'79 Eurospec 931

[924RACR]

Excellent link, thanks very much!
_________________
Vaughan Scott
Webmeister
'79 924 #77 SCCA H Prod racecar
'82 931 Plat. Silver
#25 Hidari Firefly P2 sports prototype

[Roger]

I did this today and its not hard but it definatley a PITA. I used the parts fron the Audi 4000. with the exception on the lower part of the fuel dist I(I used the Porche part) they were identical.

It took me three tries to get it right. First time I tore the orings on the fuel meetering cylinder. I had gas comming out the exhaust pipe. Maybe it was running rich hehehe. Second time I did not seal the two halfs of the fuel dist properly and I had a bad leak.

I finally got the car started and I noticed three things right away

Surgining is compleatly gone
Idle is amazingly steady
Starts with only a slight turn of the key

Keeping my fingers crossed!!!!!!!!!!!
_________________
1981 924 NA

Some people are like Slinkies. Not really good for anything, but you
still can't help but smile when you see one tumble down the stairs.

[Paul]

PLEASE CHANGE YOUR OIL!

You've got a lot of gas in the oil pan if you were running that rich.

[Roger]

First thing I did this morning was change the oil. There was so much gas in it the pressure was 1 bar at idle.
_________________
1981 924 NA

Some people are like Slinkies. Not really good for anything, but you
still can't help but smile when you see one tumble down the stairs.