'87 Porsche 924s

it lives!
installed new coil and it instantly fired and ran for about 45 seconds, stalled and wouldn't restart and that's fine because we had more work to do...
drained gas, looked more like coffee
purged fuel rail too, as best we could (took nut off end and cranked for a bit)
went and got new plugs NGK copper, BP7Es something or other the bosch platinums made me nervous, I didn't want to burn out another coil or something.
Lit her up, smoked like you wouldn't believe (not surprising all the crap we poured down there)
I thought it could be bad rings or whatever. After about 5 minutes we shut it down, let the smoke blow over, then fired it up again, almost no smoke, couldn't resist a quick trip up and down the property, got into 2nd and reverse works, clutch feels awful, full of air I bet, PO was messing with it.
Suspension felt great, brakes seemed to work and not hang up.
Engine may still be junk but then again, it might make it back. It doesn't sound good, lots of ticking and knocking at low RPM but revs nice. I think we'll go ahead and do tires and clutch, and get it legal and drive it around and see what happens. Oil pressure was fine and it never got near running temp.
 
Now I wonder if some sort of detergent in the oil for a while might be wise, to "clean it out" a bit. It sure runs rough at idle, could easily be it's only running on "some" cylinders. I think the best medicine is exercise.
Thoughts on some sort of oil additive?
 
Rinse Run Repeat

Excellent, now get it to purr like a kitten

You have been busy then, I wish I had that much spare time on my hands - perhaps I would have kept 'in front' of your efforts and been actually useful in getting the young fella behind the wheel.

Sounds like stale fuel, so drain /flush & repeat, normal for a car that has been laid up for ages change the filter and clean as much 'gum' out of the injectors as you can afford. The coil change was wise as would new HT leads be. Now that you have reached this stage it’s a series of rinse flush repeat, rinse flush repeat cycles for both fuel and oil systems. There is a few good threads on Bob’s oil board about flushing oils, head over and decide. But even cheap oil run for a bit drained and replace with fresh is req’d. That ticking sound is most probably the hydraulic lifters [lash adjusters] they may come back if you can dislodge a stuck ball and spring that lives inside them. Sadly the only good and fast way is to take them out and do them by hand which is take apart the top of the engine, perhaps if or when you do a belt change you can have a dig around up there.
Now that it running albeit rough you are nearly there in getting it to purrrr.
Here's a few tips.
Yes Firing order = 1-3-4-2: Ignition timing : 10° ATDC at 925 ± 75 rpm , Vac lines on.
Bosch WR 8 DS or Champion RN 10 GY, Gap 0.028 – 0.032 in / 0.7 +- 0.1 mm
Looking at the cap while standing in front of the car it should look like this:
4 ** 2
3 ** 1

The PO was a bit of a Neanderthal then? If the wiring from the speed and CAS are compromised please check the shielding. Signal shielding was implemented to reduce RFI noise, a number of sensors (ie CAS, KS and OS) use a shielded cable. The shielded cable is connected to the main ECU earth wire at terminal 19? to reduce interference to a minimum. If you don't attend to this it may run okay at low revs but as the Ford boys discovered with the famous DFV Formula 1 engine, EFI makes a whole lot of electronic racket as the RPM increases. Those men were at the top of their game in the early 80's and it had them stumped for days at the Dyno shop in the UK.
The pulse signal is AC from the CAS sensor and processed to digital with an analogue to digital converter in the Motronics box as computers prefer their data as on/off inputs. If this data is screwy it may be your smoking gun as to the poor running.

I looked at that voltage magnitude I previously gave you but I went and had a look at my Bosch Data stash it may have been a bit on the low side. The CAS in the early Motronic system utilised two sensors to provide speed and position signals to the ECU. However, in M1.1/1.3 the primary signal to initiate both ignition and fuelling emanates from a single CAS mounted in proximity to the flywheel. Remembering the CAS consists of an inductive magnet that radiates a magnetic field and a number of steel pins are set into the periphery of the flywheel. As the flywheel spins, and the pins are rotated in the magnetic field, an AC voltage signal is delivered to the ECU to indicate speed of rotation. In addition, a reference mark to TDC also indicates crankshaft position as the flywheel spins. The peak to peak voltage of the speed signal (when viewed with an oscilloscope) can vary from 5 volts at idle to over 100 volts at 6000 rpm. Because computers prefer their data as on/off signals, an analogue to digital converter transforms the AC pulse into a digital signal.

Your Motronic box contains the amplifier circuitry for switching the coil negative terminal at the correct moment to execute ignition. The amplifier circuitry is inside the ECU itself and the microprocessor holding the map containing the correct ignition dwell period for each parameter of engine speed and battery voltage. The signal received by the amplifier from the trigger/sensor must therefore be of a sufficient level and stability to complete the necessary coil switching. i.e clean with no 'fuzzy' interference. The signal [voltage] is thus amplified to a level capable of switching the coil negative terminal. One disadvantage of an internal amplifier is that if the amplifier dies then the DIY or even qualified mechanic is powerless to repair it so the whole ECU must be renewed. But as any 'hacker' of technology you can replace the offending component as long as you a.] have the part b.] exhibit the required care in circuit board repair. Really not that hard. Impossible today with System On Chip (SOC's) devices and their Encrypted programming, but that’s where we are now with Auto ECU's, repair by replacement.

What I gather from your post is that the distribution and quality of spark was whacky, I would still try and get a hold of an oscilloscope to eliminate flaky sensor output as an issue to smooth running. If you can't get your hands on one can you trailer it to someone that has one once you tidied up the HT leads + dizzy. Myself, I get itchy if I can't tick things off the list one by one. If you cleaned up the spark side of your problem and the signal is good but it still runs poor then sadly I have a growing grey cloud that says Motronic computer may be suss’. Long ago when the Pug 205 came to live with me I learnt a lot on the Bimmer boards about how the J & Mo -Tronics worked. They can be fixed and if the one in your 924 is sick then the opportunity to put in a re flashable EPROM is worthwhile.

Why bother?
Crank Angle Sensors [CAS] are an inductive sensor that takes information directly from the crankshaft they are far far far superior to distributor Hall Effect sensors. Problem is that they have a small magnet inside to create the voltage [& EMF] inside. If they are covered in metal filings of the air gap is too large then no signal voltage will reach the computer. Why is any of this important? The more accurately we can measure the smaller we can make the margin of saftey for knock. The closer to knock we get the better the power and the leaner we can make the gasoline AFR. 14.7 was where we went with Lambda in the J & M series Bosch units but the best power is around 12.5 [11.5 thru 13.2 depending on the mechanical/environmental variables] The original 'maps' were set conservatively for economy and longevity on 91 RON. You can get a bit of a power bump if you have a vendor that re 'chips' them with ‘sportier’ program parameters and you use a better fuel. So if you ever get a brain box serviced why not go the extra length whilst they are at it.

There was an Anti-theft protection function in some editions of the Motronic but not all, so many options and not all of each edition were used in each market they were deployed in. Basically the drive-away code is entered upon the on-board computer, or when the anti-theft system is armed, a signal is sent to the Motronic brain box which switches off the ignition and injection functions. If that is activated then your Noids wouldn't be flashing and you would have had no fuel. So it would crank but there was no fire event. I'd discount that as a failure to fire in your instance.

Personally I am very wary of older carb and points projects, they never pay back the effort needed in getting them back to health and go sick easier.
If I get my head around this project the PO had a dodgy coil [ where a coumpterless car would have long before failed] and was a NooB who went and hacked the speed and fuel sensors. Probably flooded it with Aerostart and who knows what and it froze one piston or more in the bores. Efforts from bumbling around in the dark like a NooB. I understand your frustration but a step back and a look at 'how' computers work and attending to feeding them good data is always easier than fumbling around with a cranky carburettor and points dizzy. There is a fear that things are too complicated in the mysterious 'black box' but all you really need are the right tools if you have the right 'tools' digital systems are [for me at least] easier and more reliable than analogue systems. So an Auto Multimeter, some Noids and if you can get your hands on one an oscilloscope, with the correct info will get you back to running condition faster. These are essential tools for 80's computers, newer Millennial stuff needs computer CANBUS interfaces, ‘sniffers’ and an IT degree. In of itself just a step up but as I have winged and bitched before now the data is encrypted and the dealer training is woeful and 'repair by replacement embedded as a 'solution'.

Your twofer isn't an evil thing, just misunderstood. Once it's running like a kitten it should be reliable and a joy to own, a safe, reliable ride for your son is an comforting thing if you think about it. Get hit in an X or a 924, I know which one I'd rather be in if T boned.

Soldier on, you did good work. I think by this experience your EFI knowledge may have grown. Perhaps for your next project at least concider the option to 'computerize' the ignition side for more power. Timing and AFR's are everything in the search for more power.

airfuel.jpg



:clap::clap::clap::clap::clap::clap::clap::clap:

My best regards

Sandy
 
Again, thanks for that, really appreciate the time you take.
We did fire it up again tonight and it started immediately and idled well but what a vibration racket, it's really bad. It goes away and stays away as soon as rpms get above 1200 or so. This seems to indicate motor mounts to me. I will try to measure them as I've read there's a spec for that.
That would be great news as that's simple and (if you avoid the $230/each Porsche parts) isn't too dear. Decent aftermarkets can be had for $38. The ticking is already dwindling.
We're going to mess with clutch hydraulics (PO has been there too) Pedal is very low with a cheesy spring added. Have to get that sorted and then new tires as they are almost as nasty as what was on my X when I got it.
We did purge all the fuel out and replaced with fresh (and a dose of injector cleaner). PO had put on new pump and filter it seems.
All in all we're very encouraged. A long way to go to sort all the decimated interior electrics, I swear they took the interior apart with a mallet and crowbar, just unforgivable!!! We'll get it in the end.
I even think the A/C worked!! (hard to tell but the air felt cold to me).
A very cool car. I want one too now. As much as I love my X, the extra ponies and luxury items (power windows and A/C! who has such things?) are pretty compelling. I'm off to look for one for me now.........:dance:
 
Fantastic News Jeff

Happy to pay it forward as X-Web has helped me better understand Fiats little targa.

WRT the vibration mounts it could be, also go back to the begining of the thread, that counter ballence shaft can be an issue. Out of timing etc the engine will run but shake like a wet dog after a bath.

WRT the cylinder walls keep a keen eye on the engine/oil temps, if they stay high the friction of the pistons/rings may be in play, bad ju ju!


You'll be all over the technique for sorting a suss' clutch pedal, flush the brakes too while you two are in there. In good health they stop real nice in stock trim.

Again good work and best of luck with the interior. Most of that should still be floating around wreckers as that stuff should still be around from the number of cars that are parted out.


Congradulations on getting this far, others would have blamed the [insert profainity here] German engineering and crushed it in a huff. Pat yourself on the back, it now sounds like Jeff and son will be on a 'time share' quota for driving privilages. Perhaps a 924 with the old easily improved cast iron block with a supercharger addition for added thurst for yourrself? ? But even so I will never be parted from my X's, they are happy little fun machines. Just need a little love and understanding.

Don't we all?

Gotta go will be out of SAT range for a while.


Yours Aye

Sandy
 
running is good, running decently is the next goal,
getting new rubber on the wheels today and must flush the brakes, we bled the clutch but it still feels really weird
I'm worried we still have internal engine issues; broken stuck rings or such giving lousy compression on at least one cylinder but I want to run the car a bit, get a few heat cycles in it, then see what's going on
 
update; during a test drive we had an engine fire, lots of damage before we had it under control, now in middle of engine pull and clean up, bummer, set back, down but not out :tomato:
Good news is it's still fun.
 
Hey your back from up north. Would this week work to remove something from your garage?

Hope things are going better than when last we met.
 
Now in Chicago enroute to Florida to see sick mom so maybe the week of the 29th sometime? I can tell you were the key is hidden if you want in there before then (or to wrench on the Porsche if you need a wrenching fix)
 
Oh I have had my fill of wrenching fixes putting in two water heaters in two weeks with plenty of infrastructure updating/adding/adjusting

I may need to take you up on the key as I was thinking of going to Metro Cruise with the 850 (with all my free time...) I think I have finally found an easy replacement alternator, we will see.

I will let you know, thanks

I hope things go well with your Mom. I will be thinking of you all.
 
At least someone will be home later this week, including me hopefully, if not I should be home by the 22nd but the key is easily accessible if it comes to that, I'll email you. Most of the stuff is out of the way too.
You're welcome to use my messy shop to swap alternators too.
 
A bit late to the party here, but these are quite good cars. I had an '87 and enjoyed it quite a bit. One of the last "simple" cars without tons of weight and add-ons. Fantastic handling and easy to live with.

Hang in there - will be worth it once you start really using her.
 
I do really like the car and my son does too. I got the suspension bolted back up last night and hope to charge ahead with everything else in the next few days. My goal is him driving it to school on his 16th birthday (9/28) gunna be dicey.
I don't know about 'simple" I find myself looking longingly at 1950's technology. My next project is hopefully something really old and simple, old British is calling to me again. A TF or TC would be really fun. I've even been looking at Pempletons.:mallet::mallet:
2cv_pembleton_2.jpg
 
Try working on a 928S4 :)

Good old chrome bumper MGB is calling out to you. Basic repair procedure is stare at it for 10 minutes, get appropriate size hammer, hit offending spot, drive for another 30,000 miles, repeat. MGB owners (of which I am) should take that as a complement.
 
I've had a '75 and a '63 Midget. A B might work but awfully big :p
Almost pulled the trigger on a '62 MGA but passed.
There's something about the really raw roadster thing that just can't be beat (on a nice day). 50 mph in my '63 Midget on a country road on a summer evening was the most fun I ever had "motoring".
 
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