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1980 Porsche 924 Restoration - Finally Coming Together!
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Rasta Monsta  



Joined: 12 Jul 2006
Posts: 11332
Location: PacNW

PostPosted: Sun Nov 06, 2016 9:01 am    Post subject: Reply with quote

Yes, that is one possibility.

Could also theoretically be:

1) low control pressure (clogged or broken WUR, crushed/obstructed control pressure line, obstructed control pressure orifice), or

2) excessive system pressure (sticking FPR or crushed/obstructed return line).

Have you checked pressures?
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Fasteddie313  



Joined: 29 Sep 2013
Posts: 1418
Location: Not Detriot - NMI

PostPosted: Sun Nov 06, 2016 11:33 am    Post subject: Reply with quote

j03k64 wrote:
I finally had a go at adjusting the mixture screw this afternoon. Thanks for the above image Rasta.

I turned it counter-clockwise until it stopped(max lean) and still have spray at the injectors. Fuel emerges slowly from the above injector line port, however, it sprays like hell from the injectors seconds later. Also, the mixture screw doesn't click when you turn it; my 79 is indexed and clicks loudly if you tamper with it.

I take it that means the fuel distro has failed?


the head will likely flow fuel at metering plate rest position with no injectors on it because the injectors are designed to hold back 30 or 60 psi at all times, I forget exacty what pressure..

That is also why bad injectors will leak with the metering plate at rest..

(I think, but that is a bit counter to rasta's page thing idk)

I adjust for base setting with all injectors on and go rich just until they spray and then back lean just until they quit..


Check and make sure your metering plate is coming all the way down to the rest position. The linkage could be gummed up with crud or something it impedeing its full travel.. Did you mess with the stopper thing on it? Make sure it is coming all the way down and bottoming out solidly in the rest position.. (yours is backwards from a turbo, updraft style right?)

My 931s doesn't click..

BTW while you are adjusting it with the wrench you are pushing on the metering plate mechanism and can deflect it that way..

Also.. Yours being an updraft instead of a downdraft maybe your rich/lean lefty/righty may be backwards? Try it the other direction..

j03k64 wrote:

-Fuel distributor cleaned in an ultrasonic tank


If you did that with the FD all put together including all its seals and whatnot materials inside I could see that destroying certin materials inside of an aluminum encasement.. I don't really know about putting anything but mettle in them, I hear if you put your hand in there it tears your meat off of your bone so there is that, if meat is to gasket and bone is to aluminium maybe not great..

If your diaphragms in there were already old and brittle, and the ultrasonic munched them, it may give those symptoms..

Maybe I'm wrong and it's a great idea to put a whole FD in an ultrasonic cleaner seals and all but I'd look into it..

All the WUR does is like adjust the spring pressure pushing the airplate towards the rest position so the WUR adjusts how hard air has to fight the plate to get by kindof..
The WUR and control pressure has no authority over injector pressure givin a constant airplate position. It just decides how hard it is to move the airplate through its motion from rest to open. So if the plate is at rest the plate is at rest and the control pressure means squat..
With zero control pressure it would be very easy to move the airplate to full open (failed WUR leaking through). With control pressure equal to system pressure it will be much harder to move the airplate physically to full open (clogged WUR)..

j03k64 wrote:

The air sensor disk was relatively difficult to pull up and hold with my fingers when the fuel system was pressurized during the above test. Is that level of resistance normal?


Yep control pressure = resistance so your control pressure is not zero but it may be max.. Do you have gauges?

Those flow balance numbers look pretty crappy for brand new injectors I must say.. And inconsistently varying, like first its injector 2 thats low, then 4, then 4, then 1.. Boggles the mind.. Points to bad FD..


j03k64 wrote:

So, in short, the CSV acts like a choke, the motor fires and generates sufficient vacuum to run the air plate/fuel distro system.


The CSV is just like a normal electronic injector on modern cars that acts as an enrichener or like pumping the throttle on a carb with a pumper, not so much a choke that works by increasing vacuum over venturies..

j03k64 wrote:
Thus, if the injectors are spraying without the air plate being lifted, it causes massive flooding as air/fuel ratio is grossly incorrect.


Yeah, if any of the CIS injectors are spraying or the csv it will sit there and fill your cylinders right up with fuel that will make its way into your oilpan and contaminate your oil to where it will ruin your bearings throughout your engine if you run like that..
Or if your really unlucky, enough fuel will accumulate in your cylinder at the wrong time and hydrolock your engine which leads to bent conrods, broken pistons, blown head gaskets, cracked heads, who knows.. not good.. It's pretty much lets play weakest link at that point, starter torque and rotational momentum vs dead stop like your piston hits a brick wall..
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j03k64  



Joined: 26 Jul 2010
Posts: 114
Location: Urbana, Ohio

PostPosted: Wed Nov 09, 2016 4:15 am    Post subject: Reply with quote

Rasta Monsta wrote:
Yes, that is one possibility.

Could also theoretically be:

1) low control pressure (clogged or broken WUR, crushed/obstructed control pressure line, obstructed control pressure orifice), or

2) excessive system pressure (sticking FPR or crushed/obstructed return line).

Have you checked pressures?


Rasta, I will check CPR line to make sure there's fuel pressure pushing down on the top of the main fuel control pin - good call! WUR voltage checks out, I can look for a clog, do those get stuffed up often? A sticking FPR is possible, I could pull the shim/s and see if it changes condition. Most pressure tests on the FD require the car to run, except cold pressure. Fuel pump is new. I don't think we've crushed any of the return lines as we're always very careful when jacking the car up, but can definitely look - no leaks on the shop floor.

I do not have the appropriate pressure gauge for CIS. I need to get one now that I have two dead cars. My mechanic 15 years ago calibrated the fuel system in my 79, basically told me to never touch and it would run like a beast until the head gasket lets go. He was right, no issues with it until it let go last fall!

fasteddie313 wrote:

Check and make sure your metering plate is coming all the way down to the rest position. The linkage could be gummed up with crud or something it impedeing its full travel.. Did you mess with the stopper thing on it? Make sure it is coming all the way down and bottoming out solidly in the rest position.. (yours is backwards from a turbo, updraft style right?)


The metering plate appears to be going to rest position; I sprayed carb cleaner down the mixture screw hole to help relieve any gunk that might be between the sensor beam and mixture screw. Didn't mess with the stopper thing, haven't pulled it from the airbox since it ran. Yes, NA is updraft, whereas the turbo moves in the opposite direction I believe.

fasteddie313 wrote:
If your diaphragms in there were already old and brittle, and the ultrasonic munched them, it may give those symptoms..

Maybe I'm wrong and it's a great idea to put a whole FD in an ultrasonic cleaner seals and all but I'd look into it...


Haha! Crap. I pulled all the banjo bolts, FPR, the odd allen screw off the FD. I left the main fuel pin in, and stuck the whole unit in the ultrasonic cleaner for the weekend, low to mild carb cleaner solution for motorcycle carbs was used. I've been digging around for info on how to rebuild the FD. I didn't know there was a diaphragm like mesh coffee filter thingo on the core. I knew there were hardy gaskets, springs and diaphragms in there, but they can usually tolerate the tank; especially within an enclosed environment - age as you indicate is definitely a factor to consider. I suppose it could have eaten the core filter and sucked it into the internal return line section of the FD?

There's only one way to legit figure out what's going on inside of the FD and that's to take it apart.
I bent over and ordered a new/used FD before this specific FD becomes even harder to find

By the CSV acting like a choke... I meant the CSV basically mists fuel into the intake, it sucks it in while cranking, goes boom, until sufficient vacuum is generated, so the car can run off the CIS system. Trying to completely wrap my mind around how the entire system works =)

I got a copy of the "Bosch Fuel Injection and Engine Management: How to Understand, Service and Modify" Nov 27, 1989 by Probst, C" and the Porsche 924 factory shop manual.

Had an possible epiphany, while flipping through the CIS book. We replaced the o-ring at the base of the FD with one from the hardware as it looked to be very similar; it's exactly 1.85mm thick. Does anyone know how thick the OEM o-ring is? If it were too thick it would directly impact the position of the control plunger, possibly throwing the system out of adjustment range - I would think lifting the FD would cause a lack of fuel from this drawing I found on the board.



I'll go check these other bits and let you know!
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Tiny  



Joined: 10 Apr 2006
Posts: 500
Location: London, UK

PostPosted: Thu Nov 10, 2016 10:43 am    Post subject: Reply with quote

Yep, you're going the through the K-Jet system, and got the right books too.

Get the gauges next (they were cheap in the u.s. or borrow them) and you'll see exactly what's going on with your pressures, using the book. Most other things will be just plain ole fiddling.

Rebuilding Fuel Distro's failed twice for me. Rebuilding WURS if blocked is easier in comparison.

But as many wiser have said before me --> GET the gauges or you'll likely ending up mostly just fiddling in the dark.
Hope that helps
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Fasteddie313  



Joined: 29 Sep 2013
Posts: 1418
Location: Not Detriot - NMI

PostPosted: Fri Nov 11, 2016 12:21 am    Post subject: Reply with quote

j03k64 wrote:
Trying to completely wrap my mind around how the entire system works =)


https://www.youtube.com/watch?v=a4fJAfXYxWk

Reading/understanding the frankencis thread has a lot of good info about how CIS works and the applications of each component along with what changes each have on the system as a whole..

And that WUR modification thread..

I understand things better by seeing what happens when you tweak this and that..

If you want a hardcore understanding of CIS..
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j03k64  



Joined: 26 Jul 2010
Posts: 114
Location: Urbana, Ohio

PostPosted: Fri Nov 11, 2016 11:34 am    Post subject: Reply with quote

Haha, I love theory and application!

I got the new fuel head in the post yesterday. It took a few hours to clean up before I'd even consider attaching it to my fuel lines. I pulled the flapper base, cleaned it; odd red crap growing in it. Not sure if it was a factor, but it's gone now. Luckily, they left the gasket in place, so I got a new/old rubber gasket - measures 1.5-1.55mm thick in case anyone is looking for that information. I checked the return line to see if it was crushed, couldn't find anything. So, I put it back together, left the injector lines off and pressurized the unit...

Not a drip of fuel comes out of the top, sends all fuel back to the fuel tank where it belongs - unlike the other one that was pouring fuel out the top. The mixture screw is full lean still. Lifting the flapper didn't allow fuel to come out of the injector holes. Stopped the pump, lifted it manually to eject any contaminates from top section. Repeated that a few times to ensure it's clear before attaching it to my brand new injectors. Chemicals and I are not friends at all, had to call it quits for the day. I'll sort the mixture screw using Rasta's instructions and purge the FD again to be doubly safe.

I think it's safe to say the fuel distributor was dead.


New FD


FD Flapper Base (left is off a '79, right is off the 80')


FD Flapper Base Part Numbers (top is off a '79, bottom is off the 80')


I grabbed my spare FD flapper base from the shelf. The air plate size is different!? Is that due to the EGR on the 79' and the OXyS on the 80'? So interesting how different they are in terms of the disk and funnel shape!

UPDATE:
Adjusted the fuel mixture screw using Rasta's instructions.
Passes 100ML volume test at the injectors.
I put everything back together and called it a day.
Will top the battery up, look things over and have a go at getting it to start...
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j03k64  



Joined: 26 Jul 2010
Posts: 114
Location: Urbana, Ohio

PostPosted: Sat Nov 26, 2016 10:09 am    Post subject: Reply with quote

Got it started yesterday on the first crank! Thanks for the trouble shooting help everyone! Runs smooth as glass. The smoke from the freshly painted exhaust system was unbelievable. Did standard break in procedure, burped the coolant system after the thermostat opened. Let it warm up completely, then it started to get a bit hot. The radiator fan failed to come on; pretty sure the fan thermo switch is dead, a new one is on the way before attempting to tune the motor.

There's still a few little things left to sort out:
- Random bundle of wires from a relay that's been removed
- Rear shocks need replaced (any idea what brand is best on those for OEM performance? NAPA says KYB, but I remember a post on here regarding choosing proper shocks and brand issues lately?)
- Front end alignment
- Repaint the drivers door/front fender (the previous owner welded the hinge to the car. The paint pinched when we shot the sealer on it.) Buffing and polish.
- Final touches (Anyone know where you can buy the solid rear model number decal? I can find the outlined one, but it's just not as 80s as the solid one)
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Paul  



Joined: 02 Nov 2002
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PostPosted: Sat Nov 26, 2016 10:40 am    Post subject: Reply with quote

Congrats!

Please add: change oil and filter before running again, since your oil is probably diluted by gasoline.
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j03k64  



Joined: 26 Jul 2010
Posts: 114
Location: Urbana, Ohio

PostPosted: Sat Nov 26, 2016 2:10 pm    Post subject: Reply with quote

Thanks!

Haha, yes! I changed the oil before starting it and had racked the injectors in jars while calibrating the CIS system to avoid risking the bottom end - bearings, gaskets and such. Definitely changing the filter before starting it again, most of the metal filings from machining should be in there now after an 8-10 minute run. The manual recommended driving it 200 miles, then oil/filter change. Does that seem like a good course of action?
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Paul  



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PostPosted: Sun Nov 27, 2016 2:31 pm    Post subject: Reply with quote

200-500 miles then oil and filter.
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j03k64  



Joined: 26 Jul 2010
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Location: Urbana, Ohio

PostPosted: Wed Nov 30, 2016 7:04 am    Post subject: Reply with quote

I will definitely do that Paul!

Confirmed the fan thermo-switch is dead and order Boge/Sachs 447513031H to replace the rear shocks after some research here on the forum this afternoon. I'll patch it up and post a few photos/videos
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j03k64  



Joined: 26 Jul 2010
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Location: Urbana, Ohio

PostPosted: Mon Oct 02, 2017 7:37 am    Post subject: Reply with quote

So, I had a really bad go with the dentist and nearly checked out; recovery has taken a while, but I'm finally back out in the garage. I Replaced the cooling fan radiator thermo-switch, rear shocks, and put a new oil filter on it after initial start-up after the engine rebuild, it has unfortunately been sitting since my last post.

Pushed it out a few days ago now that I'm feeling better, it started beautifully, but now runs like a golf cart. It feels empty, no power, and won't idle (idles and revs if you put your foot on the gas/throttle it). Seems to run slightly lean (head gets hot quickly), exhaust smells not so good. Starts consistently though!

I did the following so far:
Fuel system cold pressure tests - injectors spray only with air plate lifted slightly, patterns are even, volumes are within spec. Volume test at 25 seconds over flowed my quart jar, so heaps of fuel. The fuel frequency valve (behind the CIS, adjacent to the air box that is linked to OXS); it checks out at 2-3ohms. New pump, accumulator, fuel filter, lines are clear, injectors. So, fuel system is good to go; possibly too much fuel flow to the fuel distributor? 30 seconds would have been about 1.25ish quarts.

WUR tested at 18.3-18.9ohms, between the 18-22ohm range. Not sure if the lowish reading suggests the element is getting weak (around 60F that day). Screens are clean, was careful about that during the engine rebuild.

Pulled the auxiliary air valve (AAV) cleaned it, tests 48-49ohms, put it in the freezer for a bit and it opens heaps, 12v close test passes within the 1-5 minute window. Seems to be functioning correctly. I have spare units, all three tested at 48-49ohms, not the 30ohms specified in the Haynes manual. Anyone else notice this?

I checked the intake fuel air mixture screw and the idle stop. Idle stop is at 90% max adjustment before the CIS side of the bolt (the bit with the screw driver cut out) goes beyond the casting. Set the idle mixture screw using measurements off my '79 to try and get close (how many turns to hit the same setting).

I thought the decel valve (Vacuum Limit Valve) might be faulty, unlikely(?), but possible. If you unplug the top line off the decel valve, the idle issue is resolved. However, the idle slowly increases from 950 to 1200, then 1600, then 2100. If you place your finger over the removed decel upper vacuum line, it kills the engine. I pulled the vacuum lines connected to that system, they're all free of obstructions.

It should be noted that the carbon canister, normally located in the inner fender well, has been removed, and those large lines leading off this system are open. I put a filter on the line that is attached to the decel valve on my 79 and the airbox line is simply plugged with no issues.

Lower line of the decel goes to the thermo-vacuum valve, so it could be the decel valve, thermo valve, AAV(?), or something with the OXS system.

Any ideas?

Update:
Another possibility is wiring related to the Oxygen Sensor System (the OXS box) is incomplete/connected incorrectly. There's one relay's worth of remaining wires hanging in the car near the fuse box that are 'unknown'; one has ignition signal/is hot (can't remember).

I understand there's an 'RPM relay' in the 1980 model (http://924board.org/viewtopic.php?p=136069&sid=c1ce43ab263342643061676544a41a34), found it a couple days after this post. Maybe I have connected the wires that go to the microswitches/thermo switch that's linked to OXS incorrectly upon reassembly. Anyone have a photo of what wires go where so I can check that? I hope he didn't mess with the OXS

I'll check the colors to figure out what the hanging wires are for; the horn & fuel gauge are dead, headlights fried the motor relay as well. Maybe the hanging wires are for the AC fan relay (he ghetto rigged the cooling fans to run 24x7). I don't think the coolant has been hot enough to trigger the new thermoswitch. It's still odd that the engine would run properly and then not...



(post trimmed on 3 Oct)
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Eric P  



Joined: 21 Jun 2017
Posts: 94
Location: NY, USA

PostPosted: Tue Oct 03, 2017 3:40 am    Post subject: Reply with quote

I won't be much help in figuring out where to plug stuff in, but I do have a few notes on the fan operation as I spent a considerable amount of time troubleshooting mine.

The passenger side fan comes on only when the AC is on and the car is running.

The driver side fan comes on at low speed when the car is off and the engine is hot. You can test this with the engine cold by pulling the thermo-switch wires off and jumpering them together. With the key off, you should have low speed fan operation (which goes through the low speed resistor under the dash). With the car running and the engine hot, the driver fan should kick on at high speed (through the fan relay). Again, test this with a cold engine by jumpering the thermo-switch and starting the car.
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j03k64  



Joined: 26 Jul 2010
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Location: Urbana, Ohio

PostPosted: Tue Oct 03, 2017 8:39 am    Post subject: Reply with quote

Eric, Thanks for the reply! A/C is completely removed from the car, I had to rewire the harness for the two fans from scratch bc the last guy cut them off entirely. I jumped them at the thermo switch in the radiator to test and the driver's side fan does comes on if I do that. I should probably double check the speed as you point out; pretty sure it was fast moving, but better safe than sorry.

I wrote the wire colors down that are hanging inside the car near the fuse box, they appear to match the A/C fan relay schematic?

RedBlack, WhiteBlack, PurpleBlack (?), Brown, RedWhite (maybe redyellow?), GreenYellow, and YellowBlue.



I tried bypassing the thermo-vacuum valve out of curiosity, same issue persists. Runs without the decel top line on, dies if you put it on the valve or cover it with your finger. Cover the decel top line half way with your finger, and the car seems to idle as it should. Runs lean and a bit hot. Need to check the shop manual for further testing procedure. Has to be something with vacuum/mixture.

I pulled the intake tube to take a picture of the wires on the micro-switches; screwing up the order OR a failed micro-switch would cause mixture related problems (assuming the system is intact). Does the order look correct? Also, the coolant thermoswitch at the back of the motor has two brown wires that are linked to OXS, does the order matter?


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Goldwolf  



Joined: 25 Jun 2017
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PostPosted: Tue Oct 03, 2017 11:58 am    Post subject: Reply with quote

First off, the DENTIST! Damn.

I have a similar symptom, I have to give mine a touch of gas to get it started, then a little to hold the idle. I can drive it no problem. But if I come to a stop it may or may not die.

Hope the experts on here can help you out. Me too.
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