924Board.org

[Fifty50Plus]

The WUR dumps the excess fuel pressure eventually back to the gas tank. Make sure that one of the return lines isn't clogged and prevents that. I had a similar (high pressure) problem that was caused by a blockage.
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1979 924 NA race car
1982 924 NA race car - Sold
1982 924 Turbo almost a PoS
1981 924 Turbo a real PoS, new engine
1982 924 Turbo nice body, blown engine
1972 911 E race car - going to Vintage
Various 944s to become IT-S race car

[Beartooth]

Well, good news! It turns out there was a blockage - in the inlet filter in the WUR itself. It wasn't completely blocked, and I'd flushed it with brake cleaner, but either the force was strong with that nastly old varnish in the system, or there was a glob that found its way in there. I finally took the WUR apart completely, hooked up the line to the inlet, and turned on the fuel pump. Sure enough, fuel pressure shot up, and I just got a dribble coming out of the exposed inside of the WUR. After soaking the front half of the WUR in carb dip overnight, I cleaned it all out and put it all back together again. Presto! Cold pressure is just a touch high (2.5 bar, Haynes says 2.0-2.4), warm is bang on (3.6; Haynes says 3.4-3.8 ).

Even the injectors are working a little better, but I doubt they'll recover completely. I've run a fair amount of fuel through them into some jars, and they'll all spray a decent pattern if you push the plate down far enough, but if you push it down slowly from the resting position, a couple of them will start with a drip or solid stream. Once you get them all "chattering," you can back it down and they'll all produce a half-decent spray until just before they stop, but I'd be surprised if it'll idle smoothly based on what I'm seeing.

The kind of frustrating part in all this is I went back into the FD a couple times double-checking things, and then managed to mash one of the o-rings that fell off the barrel as I was putting it together, and damaged the diaphragm a little. I was a little concerned about warping the body, but I couldn't see anything against a straight-edge, and it seems to be working as it should without any leaks from the body. If it runs well, I'll call it good for the moment, but I'll probably go back in and put all-new soft parts in it before I try to take it outside the local area (hopefully I get to the point!). Who knows where the calibration is at, but I think I can figure that out if I have to, and it's not the biggest priority. I do need to dig through and see if I have enough crush washers to stop all the leaks I've got now. Having done and undone every fitting several times, the washers on there have pretty much been worked to death.

So, definitely a few lessons learned. First, never introduce any solvent to the fuel distributor or other parts until they're torn down and the non-metal parts are removed (I'd sprayed brake cleaner in the FD trying to get the plunger free). Think like Captain Ramius: "Mosht thingsh in here don't react well to sholventsh." (Hunt for Red October reference, in case you're wondering) The FD was in surprisingly good shape and probably would have been fine with a once-over if it hadn't been for the swelled o-rings. Second, the best tip for control pressure troubleshooting I found was to start cracking fuel lines, following the path the fuel takes, and when control pressure doesn't drop when you open the fitting, stop there and investigate the line or component. I think I found that in one of the PDFs here: https://cis-jetronic.com/index.php?rt=product/category&path=65_66 Third, that old gas gunk is persistent. Short of replacing all the fuel lines, it's probably going to keep cropping up for a while. Those little filters are a Godsend, and a pain in the butt. Finally, don't get in a hurry working with the fuel distributor. Both here, and working on one from my Mercedes, I've found that the o-rings on the upper part of the barrel are the biggest hassle (imagine dealing with eight). I'm finding the k-jet FD to be surprisingly forgiving, but definitely not foolproof. Like many things, when you start to get comfortable with it is often when you screw up by trying to rush it.

Anyway, hopefully this isn't too long and boring a post... I've kind of been stuck on the fuel system for a while (which isn't too surprising), so it's good to finally get to the point where I'm confident it'll work well enough to start the car, and can move on to putting the rest of the pieces back together. Hopefully I'll be able to hear it run soon!
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1980 931 diamond in the rough

[Fasteddie313]

Ever put Techron in it?
Some heat cycles might help the injectors clear up a bit too..
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80 Turbo - Slightly Modified

[Beartooth]

Yup, I put five gallons of gas in the tank with a whole bottle of Techron, and assuming I get it on the road, I'll put another in the first full tank or two, and probably a half bottle every tank thereafter until I get some miles on it. In retrospect, the best thing to do with the fuel lines I could take off would be to soak them in a bucket of gas with a bunch of Techron in it, probably for a week or so. It might not get all the gunk, but it'd help, and shouldn't hurt the rubber lines. Of course, I'd probably need a five gallon bucket (not full, obviously) with a lid that seals. Not worth burning the garage down to get your fuel lines clean! I'm not in a hurry to replace the injectors, and I'll definitely check out the spray pattern again before I make that decision. Would be really nice if they cleared up perfectly, but even if they're marginal, a new set would probably pay for itself in a year or two if I drive it much. Another future problem...
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1980 931 diamond in the rough

[Beartooth]

It lives! One quick thing I'll mention: I wish I'd paid attention to the oil pressure when I started cranking it for compression checks. I'm pretty sure it didn't have any; it definitely wasn't getting oil to the top end. I did wise up enough to check it out before trying to start it. I ended up taking the pressure relief valve off the oil pump, and just a few drops of oil came out. So I taped a couple pieces of hose together to attach to a vacuum bleeder catch can and used a shop vac to suck on the other end. That pulled some oil into the pump, and I was able to get oil pressure after that. The cam and buckets should be fine - I poured oil on them early on, and added a bit more once or twice - but if the bearings weren't getting oil while I was cranking for the compression check, it definitely did them no good.

Oh, sorry, but one more thing: I made a new plug wire set from part of an old partial set for a V8 I had sitting around. It was a universal set that comes with a bag of different boots and terminals for two or three kinds of distributor caps, I'd kept the pieces I didn't use, and it turns out the socket-style terminals match, so I had all the right pieces (I did buy a nicer crimping tool is all). I also had some miscellaneous wire looms, and a couple of those came in handy. I'm pretty happy with how it turned out, I'll have to post some pictures.

Anyway, I had a pretty good feeling it'd start, because it fired enough to turn over a few times on its own when I was working on the oil pressure. I set the adjustment screw for the fuel distributor to where one of the lines to the injectors was just starting to drip. I didn't touch the distributor, just verified that I was getting spark by pulling a plug wire and hooking it up to a spark spark plug, and cranking it until I saw a spark. So today I pulled it out of the garage so I wouldn't get a bunch of fumes in the house, hooked up a battery, and went for it. It fired after a turn or two, then died. I cranked it again, and this time it fired up and held a slightly fast, but pretty steady idle. There are some squeaks, and I'm not sure the turbo sounds quite right when I goose the throttle, but it sounds healthy enough that I'm tempted to try a spin around the block. I still have a lot to do before I even think of heading out on the road, but I'm a big step closer now!
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1980 931 diamond in the rough

[Beartooth]

I took a lap around the neighborhood today. Barely made it back! I don't have a battery that'll fit, so I've been using a battery booster (which is just enough to get it started), and I don't think the alternator is doing anything. Because of that (I think anyway) the ignition had barely enough energy to run it at all, and would run out as soon as it was taxed (fan was running by this point too). I was able to bring it up to 30 MPH or so and try out a couple gears. Reverse through third all seem to work, but I think the syncro on first is gone: I got a pretty good crunch when I want from second to first, and that at ten miles an hour or so... If it's just first gear, it's definitely something I can live with for the time being. Then, it definitely has an exhaust leak somewhere, and the turbo doesn't sound healthy to me. I'm not sure what it's supposed to sound like though, just revving it with the hood open; I guess I'm mostly comparing it to the Mercedes diesels I've tinkered with.

Oh, and speaking of ignition, I had another problem that had me scratching my head a bit: I went back about an hour after I'd initially got it going and tried to start it again, unsuccessfully. It'd fire up, but die as soon as you let the key off from the start position. I thought it might have something to the "run" resistor circuit, or something not right with the coil or plug wires I put in. I monkeyed with those a bit, then checked the coil voltage. When you turned the key to run, it was fine, but if you hit "start" and let off, the voltage was gone. Well, I finally figured out it was the ignition switch itself: you have to manually turn the key back a bit or 9 out of 10 times it doesn't re-energize the circuit. The other thing that helped me figure that out was that the dash light and all wouldn't come back on after cranking it either. I wouldn't say it's fighting me every step of the way, but it's definitely a little hesitant!
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1980 931 diamond in the rough

[Fasteddie313]

The ignition switches can be fussy..
Blast in the keyhole with WD40 and work it back and forth a bunch of times with the key.. Repeat..
That fixed one for me..

These turbos won’t spool much at low load like a diesel will, and they won’t make all the tuner car turbo sounds either..
They are kinda big turbos and don’t get a lot of RPM at low load like modern cars with their tiny turbos..

If you can tell the turbo is spinning, it’s not making noise like an owl hooting, and it’s not smoking, it’s probably healthy..

These turbos are like tanks.. They are beefy and robust..

You may hear some clacking at the turbo at idle and when bumping the throttle.. Normal for the bypass valve in it..

Yes get a real battery in it..
If your battery light comes on with your key turning on that’s good..
If it goes out when you start the car that’s good, and it’s probably working..

These G31 transmissions don’t shift like most others..
If you shift like a normal manual driver, making the syncros do the work, they suck because the syncros aren’t very good, and they have a HUGE job on their hands handling the inertia of the driveshaft..

If you learn and implement advanced/race shifting techniques they shift as good as any others… Double clutch and rev matching..

Downshifts, especially to the lower gears, requires a doubleclutch rev match..
Or like even selecting any gear after you have been coasting..

Shifting from 2nd (or 3rd whatever) to first while you are moving/slowing:
Clutch in-shift to neutral-clutch out-rev engine slightly higher than to match road speed-clutch in-shift into gear-clutch out..

Even going from 5th to 3rd, or selecting a gear after coasting, rev match the road speed in neutral with the clutch out first, then quickly dip the clutch-shift into your gear-clutch out..

Even a fresh G31 is greatly improved if you do the syncro work yourself instead of relying on the syncros, because they just aren’t good..

This guy has great technique videos and does them in a 944..
https://m.youtube.com/watch?v=c2LV8lvAFPs

Good job!
Good progress!
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80 Turbo - Slightly Modified

[Beartooth]

Thanks for the encouragement, Fasteddie! I took the alternator out yesterday: I was planning on taking it to a shop in town, but I figured I should take the voltage regulator out and look it over first. The brushes looked fine, but the electrical contact was discolored. So I cleaned it up, put it back on, and it's kicking out voltage now. I can't say for sure it's healthy, but hopefully that's one less thing.

I noticed too that even with the alternator working, it acts boggy off idle. So it's probably not ignition causing that. It's real sluggish going through about 2000 RPM, then pretty responsive once you get it above 3000 (just free revving it). Lots of potential culprits on that though; the CO adjustment is just a rough setting, I haven't checked duty cycles, and there could be vacuum leaks. It would also be a good time to install the wideband O2 setup I got (Innovate LC-2); would give me a gauge and take care of the probably faulty O2 sensor.

So now, it starts pretty reliably, doesn't look like it's fogging mosquitos, and the gearbox and clutch are all functioning. If I can get rid of that bog, all I really need to get it on the road is some brake work, a set of tires that aren't rotted to death, and to fix the turn signals. The cancel mechanism must be broken and jamming it up: it won't move freely, and you have to jiggle and mess with it to get it to stop flashing.

Hopefully the gearbox is in good shape. I gather that a full refurb tends to be a long and expensive process, and a good replacement requires either a lot of money or luck. I love manuals though: half my cars have one, and one will probably get converted to the way God intended it. And I always wonder at the kind of person who buys something like a 924 with an auto (driving in constant stop-and-go traffic or only having one leg is the only possible justification). I'm pretty handy with a stick, even on a difficult transmission, but hoping to get even better with this car. I am worried that the previous owner might have been a grind-it-and-find-it type; sounds like a ham-fisted driver could eat up one of these boxes in a fraction of the miles mine's got on it. On the other hand, as long as all the gears will hold, it'll still be a lot of fun even if I have to learn to drive around it. Hopefully the dog-leg first will be second nature to me too: my truck has such a low first that I usually start in second. Actually, my Mercedes starts in second too, but that's another story!

Anyway, I'm definitely starting to get excited. The big hold-up now is the state. I finally called them about the title: they said to see when the check for the title cleared, that it's in work but could be up to ten weeks. So, after I hung up with them, I went and looked it up. Eleven weeks ago... I feel like calling them back to suggest they get a calendar, and that it's the same amount of work whether they do it promptly or sit on it. But then I'm afraid the story would change to "what paperwork?"
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1980 931 diamond in the rough

[Fasteddie313]

Yep..
Vacuum leaks and CIS pressure testing time now..
Injector flow testing, set the timing by the book..
Getting close to the finishing touches..

What your describing about it running better after spool RPM is indicative of vacuum leaks..

If you decide you can’t live with that trans, and don’t want to put big money/work into fixing it, you can swap a 944 tranny into it pretty cheaply/easily.. Or any other 924/44/51/68 trans/TT..
But the G31 is kindof special and has its strengths.. Really adds to the character of the car.. Especially if it has a LSD its worth repairing/keeping/selling..
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80 Turbo - Slightly Modified

[Beartooth]

Well, I'm hoping the transmission at least works well enough to make the car driveable for the near future, and if it's sound, that'd be great. It's only if it's on its last legs that I foresee a transmission swap; I guess the upside there would be if I could find a wrecked donor and get the parts to upgrade the brakes. I'd also consider fixing the G31, if it comes to that; I rebuilt the transmission in my truck, so tearing into this one doesn't phase me much. Seems some parts for it are unobtanium though... That said, it's always worth a look. I'm not sure if it's an LSD or not; still have to get the rear end off the ground (which I'll have to do sooner rather than later, since I have a leaking wheel cylinder).

While we're on the G31 topic, what's the go-to transmission oil? Red Line 75W90NS seems to tick all the boxes (GL-5, recommended for Porsche transaxles). The one concern I'd have is if I do have a limited slip, whether the friction modifiers are needed. My understanding is those additives keep the clutches in the LSD from being grabby, but they interfere with syncro operation. I gather that Porsche recommends G-5 for the G31 (and related 915), but haven't found any information on whether a friction modifier was recommended. One last thing on that: the output flange seals are leaking pretty badly and I can't find any listed anywhere. Any idea where that's available from, or if it's a common size?

I'll have to do something about the potential vacuum leaks, I guess. Most of the vacuum lines look ok, and I hate to spend a bunch of money replacing all of them at this point, but I might have to sooner or later. On the other hand, it might be time to pony up and buy a smoke machine; I could have bought two with the money I've spent replacing vacuum lines on my Mercedes...
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1980 931 diamond in the rough

[jacobroufa]

So glad to hear of your successes in getting this car back running!

I think that Redline 75W90NS GL-5 oil is what is recommended. I picked up a jug myself for my G31 reassembly. I don't know that there's anything necessary to do for LSD regarding the gearbox oil however.

I have had OK luck finding some transmission parts through http://www.einmalig.com/. Thankfully there are 928 and 915 gearboxes that have some shared parts.
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1980 Porsche 931
1981 Porsche 924 Weissach

[Fasteddie313]

Replacing all of the vacuum lines (that actually see boost/vac) should be pretty cheap..

It’s just hose, and cut 90s out of whatever you can find..
You don’t need Porsche parts..

I would like to see ANY original 931 cloth covered lines that don’t need to be replaced.. Look at the inside of them and you will see..

Replacing all of them would be one of the first things I’d do to a 931 even if it seemed to run ok..
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80 Turbo - Slightly Modified

[Beartooth]

I've finally got a title! Things have kind of been on the back burner because I couldn't do much more without buying more parts, and I didn't want to spend any more money until I had the title in hand. Anyway, I'm thinking now about what I absolutely need in order to get it on the road safely. A new brake master cylinder and wheel cylinders are musts (one wheel cylinder is leaking; I'd consider the calipers too, but can't find those or parts for them anywhere). I figure a new turn signal switch is in order; maybe the one in it is fixable, but it feels like there are broken pieces inside. On the (long) short list once I feel comfortable moving forward are new clutch hydros, belt, hoses, hatch struts, CV boots and rack and pinion bellows, axle seals, and vacuum elbows and lines. I'm not sure what to do about the fuel pump relay. The few places I can find the correct KAE relay show it being out of stock. It works with a plain relay, but I'm guessing you lose some protection circuitry or something (I haven't found an explanation of what the extra circuitry does).

I'll order new tires shortly too. I think ideally I'd go with 205/60/15s, but the selection there isn't great. Meanwhile, Sumitomo has this tire https://www.sumitomotire.com/Tires?linename=HTR+A/S+P03 in 195/65/15 or 205/65/15. The 205/65 is 3lb heavier and a higher load range; it might grip a little better, but with more weight and a slightly taller sidewall, I doubt it'd feel any more sporty. I'm looking for a bit of a jack-of-all-trades, but biased towards performance as much as possible given the size and wanting to keep it at $100/tire or less. The Sumitomo is a high-performance all-season; most others in that size are grand touring or standard touring. Not sure if I should get too wrapped up in the category, but obviously I'd prefer to avoid a tire with a soft, squishy sidewall.
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1980 931 diamond in the rough

[Beartooth]

Well, no quick fixes for any of the broken bits so far. I pulled the steering wheel, and the turn signal switch is indeed broken. I tried spraying some electrical switch and contact cleaner in the ignition switch, but it's still dying between start and run. Then I pulled the window regulator out, and the aluminum frame is broken at the top where the main arm attaches. Any idea if Pimax brand replacements are any good? I guess on the other hand, if I get a used one I've got all the parts I need if something goes wrong, as long as it's not the frame...

On the plus side, I hadn't run it in a couple weeks, and it fired up instantly. The boggyness is a bit better (I found I'd left the vacuum line to the charcoal canister switchover valve disconnected, so I plugged that), but it's still bad enough that I wouldn't try to take it on the road yet. I was able to take it around the block again, and engage all the gears. The gearbox seems sound so far; the only issue was that it was sometimes blind man's bluff trying to figure out what gear you were putting it in. I can't see any play on the shifter side of the linkage, so it's probably the bushing(s) on the transmission end. Anyway, time to get some parts coming my way!
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1980 931 diamond in the rough

[madislandguy]

Replace that ignition switch before you start driving the car. You will eventually hit a some little bump that shifts the key just enough that the engine dies at the most inopportune time.