924Board.org

[jacobroufa]

Probably could have done this last Sunday, but I didn't have the time to get to it til this afternoon... Tore everything back down and got the water pump off. The gasket failed at the base, where a bolt had broken through part of it; must have been enough for it to fail!

I took everything back off and wire wheeled the whole area on the block to be sure, reapplied ultra black gasket material to the pump instead of waiting for another paper gasket to come in. Now I'm waiting 24hrs per instructions for it to cure before exposing to liquid. Weather permitting I'll fill the system tomorrow and see how we're doing. Fingers crossed I can button it up and take it for a drive!
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1980 Porsche 931
1981 Porsche 924 Weissach

[jacobroufa]

Well, so I got it back together, but now it's running like crap!

https://i.imgur.com/R2EWo6y.mp4

Timing looks good and thankfully I don't have coolant coming from behind the water pump anymore.. why would this be an issue now? Last time it ran it didn't have this sort of problem. Bad fuel?

So my plan of attack is to drain the tank and put in some fresh fuel and go from there, unless there is other wisdom anyone has to share...
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1980 Porsche 931
1981 Porsche 924 Weissach

[jacobroufa]

Ok so I had some time to think. I usually don't work on the cars during the evening unless I have small task -- it takes up way too much head space and I found myself thinking about this deep into the night. Maybe it was the coffee.

Starting over again.

So, the fuel is maybe 18mo old? I will drain and use in my small engines.

In my haste last night I didn't think about this in a diagnostic fashion. I just wanted the car to run! I was (am!) so eager to drive it, I really just want to get it on the road. I also really want to be like so many other of you where you can just reach in the window and turn the key... (and maybe that's just too much of me watching Kent from the Mercedes Benz CIS diagnostic videos.)

So resources:
924.org CIS diagnostic
931 Resuscitation by 924RACR
931 Diagnostics by Ideola

Once I read through all of these and thought some more, this feels like *more* than just bad gas. There's something causing the car to be completely unable to idle. In looking through Dans's diagnostic above, the very first line item is to ground out the overboost switch because it fails open! Well, if I had pressure in the lines to be able to deliver fuel, but not enough to push it at its required pressure, that certainly sounds like a pump is not working... That'll be the first thing to tackle when I get more time.

Looking through Dan's old thread on Woody I see that he replaced the fuel pump (probably external) and that was it as far as fuel system. So I've got a new fuel filter on order.

I was reading also that any vacuum leaks can be devastating, and the last time I looked at the boot between the fuel distributor and the turbo compressor it was pretty well cracked up. Reading into it a bit, I found this thread that references the part (931-110-138-04) and like me he found out it was NLA.. Thankfully there's a link to a fitting replacement. Ordered that as well.

Apparently some bonehead put the plug wires on in the wrong order also -- they were 1-2-3-4 and I must have done that in my haste to get the valve cover back on. Swapped them around and it ran more readily but still like crap.. Noticed that my distributor cap and rotor have seen way better days so a cap and rotor are on order as well. I did not get to pull the plugs yet, as I ran out of time last night, but they're on the list also.

---

So, my next steps are:
- ground out this overboost switch and see if that is indeed preventing proper fueling
- replace plugs, cap, and rotor
- finish vacuum leak repair -- I took care of all the braided lines I could get to but I didn't replace any of the rubber elbows up top or check the boots. Now that I know the one between the afm and compressor is bad that went up to the top of the list.

Then I will get to tackle fuel issues if they exist, I guess.

These cars are really trying to work on, with the packaging. Very nicely put together and it all fits well if you get it in order.. Not good for a half hour here and there and a quick win on an evening![/list][/list]
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1980 Porsche 931
1981 Porsche 924 Weissach

[ideola]

This is no reflection on your wrenching skills, but in situations like this, what almost always has happened to me is that I screwed something up in reassembly.

That car was running great, and I'm pretty sure I had already done a tune up (plug wires, cap, rotor, and plugs), so not sure why they would be looking sketchy...maybe think twice / doublec check them before replacing them.

I'll bet a dollar to donut that you still have the plug wires on incorrectly. Firing order is 1-3-4-2. You have to make sure that the ignition distributor is indexed correctly relative to the distributor post connected to #1 spark plug, and then CHECK AND DOUBLE CHECK that the plug wires are attached in the correct sequence.

From this thread:

[jacobroufa]

Just double checked -- I have the plug wires in order 1 - 3 - 4 - 2 starting with where the rotor is pointing at TDC.

The car was running awesome when I bought it! That's part of why I'm so miffed -- my expectation was that I should be able to get going right away.

I just grounded out the overboost switch while I was out there and that didn't change the condition either so I've still got something going on.

I definitely believe you did some tune-up items, Dan, but the center point on the cap has very bad carbon build-up -- this could not have happened with a new item -- and the rotor as well. I scruffed them up with some sandpaper but it'll be best to replace them. Perhaps you grabbed a known good set from the shelf instead of a boxed item? I know I personally have got "good" spares that look a bit rough for some of my stuff, so that seems plausible. Just doublechecked your thread as well and it makes no mention of these parts (though you do mention other small tune-up items in the list) though it's certainly possible to overlook that in a forum post.

No fault of yours, just another small item on my list!
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1980 Porsche 931
1981 Porsche 924 Weissach

[ideola]

It's possible / likely that I'm misremembering...although, hang on a sec...I have a list in Google Keep...

Here's the items I checked off of the list:
Cup I wheels + tires (used tires)
Install black interior
Remove AC
Reinstall exhaust
Reinstall half shafts
Shifter bushings
Walbro external pump
Starter solenoid
In-tank pump seal
Ignition switch
Swap in rebuilt trans
oil change + filter
air filter
plugs cap rotor leads
windshield

Here's the list that was not checked off:
clean and inspect wiper switch assembly
fuel filter
timing belt, tensioner, alt belt, water pump, tstat, temp gauge, coolant, water wetter
change dampers (were included with car as I recall)
diagnose backup lights
diagnose hazards
turbo seals
CIS test
flush brake fluid
hood liner (included with car as I recall)
check sunroof and hatch seals
check all vac elbows and lines


So, based on my note keeping, I'm pretty sure I did do a tune up. Not sure why it would have shown carbon buildup as you describe, but stranger things have happened, and the car didn't get a lot of use. Sometimes sitting is the worst abuse!
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erstwhile owner of just about every 924 variant ever made

[jacobroufa]

[ideola]

If you need to borrow my CIS tester, let me know.
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erstwhile owner of just about every 924 variant ever made

[jacobroufa]

Awesome, thanks Dan, I appreciate it.

So hearing nothing when I flip the ignition on I go to test the pump. No voltage at the pump terminals. Ok. Looking at the relay, it's not the original one with a fuse; looks newer and the part number checks out as the proper replacement. I bridged terminals 30 and 87 and nothing happened. I assumed the fuel pump would have come on. I turned the car on and cranked it and nothing... This should have resolved the problem if the fuse was good, right??
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1980 Porsche 931
1981 Porsche 924 Weissach

[ideola]

931 relays never had fuse.

Double check the ground wire for the overboost switch. Check the entire length of it. They are notorious for cracking and breaking, possibly inside the craptastic outer brown sheathing. If that wire doesn't ground, you won't get power to fuel pump circuit.
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erstwhile owner of just about every 924 variant ever made

[jacobroufa]

Got it. Checked the switch -- it's got continuity so it's good (they fail open, right?) and then checked continuity on pin 31 of the relay and it's good there too! Checked voltage on pin 30 which is right from the battery; got 12v and change. So if the pump doesn't run with 30 and 87 (line to pump) jumped, the issue is either continuity of the line from the relay to the pump, or the ground of the pump? Or the pump itself, but I can't bring myself to believe that would be the issue -- you JUST replaced it!
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1980 Porsche 931
1981 Porsche 924 Weissach

[jacobroufa]

I don't feel like crawling under the car again tonight; I did a ton of yard work today. I'll check ground on the pump tomorrow. Should have checked it earlier. Feeling like I'm close here! The electrics all seem to check out up front!
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1980 Porsche 931
1981 Porsche 924 Weissach

[ideola]

Yeah, seems like if you have good signals at the relay, it won't be forward of there, it has to be in the circuit from the relay back. Grounds, broken wire, or bad pump. Stranger things have happened.
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erstwhile owner of just about every 924 variant ever made

[jacobroufa]

So I've got it! Sort of... Fuse connection had corrosion on it, and at the time I measured voltage there, I could swear I measured both sides of the fuse but apparently not or I hit it in just the right way so as to bridge the gap.

So cleaned that up and jumpered and the pump ran. Relay is giving me intermittent success (by success I mean pump primes when I turn the key) and I'm still experiencing sluggish performance! Pushing my foot to the floor I've still only got ~1200rpm and if I take my foot off it'll die within 20 seconds or so.

I might have to take you up on that offer for the CIS tester, Dan..
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1980 Porsche 931
1981 Porsche 924 Weissach

[ideola]

Put a bottle of techron in, get it running, and hold idle at 2000 RPM until fully warmed up. Then see if idle settles in. I work from home 100%, you can either come by, or we could meet in Marengo or Belvidere.
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erstwhile owner of just about every 924 variant ever made