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931 Head Installation Thread
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bureau13  



Joined: 07 Sep 2017
Posts: 412
Location: South Florida

PostPosted: Sun Nov 28, 2021 8:53 am    Post subject: Reply with quote

I decided I should do a compression test prior to actually starting it. Not sure that's really needed at this point, but it's easy to do right now so why not.

Pulled fuel pump fuse, spark plugs, coil is not in the car yet, hooked up the tester and battery and cranked it.

Nothing. Battery is charged up, lights come on, but the only thing I hear is an audible click that sounds like it's from the engine compartment, not the starter.

I'm guessing I've forgotten to do something, but I'm not sure what. Any ideas? I suppose the battery could be "charged" but can't put it much current, or I could have an issue in the ignition circuit that popped up while the car sat. The starter was replaced fairly recently however.
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-----------------------------------------
1982 931
1986.5 Silver 928S
2007 Hummer H3 (Daily Driver)

Past lives (I miss them all):
2004 RX-8 (Wrecked)
1993 RX-7 (Sold)
1987 RX-7 Turbo II (Sold)
1985 RX-7 GSL (Stolen)
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bureau13  



Joined: 07 Sep 2017
Posts: 412
Location: South Florida

PostPosted: Mon Nov 29, 2021 5:34 am    Post subject: Reply with quote

Lol never mind, apparently I disconnected the the ignition wiring connector by the passenger firewall.

That's the good news. The maybe bad news is that I'm now getting about 60-70 psi compression on all cylinders. I was getting 120 psi on cylinder 2 before I pulled the head. FWIW it jumps up to its final reading quickly and stays there. That being said, this IS a different compression tester, as I couldn't find the one I used before. But I don't think that should matter.

One other thing I meant to get some opinions on...the car has some gas in it, but hasn't run in about a year. I've been assuming I should drain that out, but some other people were telling me it should be fine. Seems safer to drain it, but what do you guys think?
_________________
-----------------------------------------
1982 931
1986.5 Silver 928S
2007 Hummer H3 (Daily Driver)

Past lives (I miss them all):
2004 RX-8 (Wrecked)
1993 RX-7 (Sold)
1987 RX-7 Turbo II (Sold)
1985 RX-7 GSL (Stolen)
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Mike9311  



Joined: 14 Dec 2004
Posts: 1216
Location: Chicago-ish

PostPosted: Wed Dec 01, 2021 12:38 am    Post subject: Reply with quote

If you have the patience, drain it, but I know I would be lazy in the moment and try anyway

If patience prevails, then into the lawn mower it goes
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1980 931 since 1989
1981 Ideola 931 Club Sport
1982 931 Entwicklungsfahrzeug
1979 924 NA ohne 650 mit 471
1982 931 Red Resurrection - 951 IC
1982 931 parts car / resurrection?
1980 924 NA (R&D lightweight)
1982 931 wana-be GTR race car
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924RACR  



Joined: 29 Jul 2001
Posts: 8546
Location: Royal Oak, MI, USA

PostPosted: Wed Dec 01, 2021 1:09 am    Post subject: Reply with quote

One year old gas wouldn't bug me. Worst case, top it off with fresher stuff when you're ready to get some miles on - then run through it and backfill with new, should be no issue.
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bureau13  



Joined: 07 Sep 2017
Posts: 412
Location: South Florida

PostPosted: Sat Dec 04, 2021 11:19 am    Post subject: Reply with quote

Well I'm all set up to test this out but...I have a coil wiring issue. Keep in mind I had all this wired up before and it was working.

I have a Bosch coil that has two male spade connectors at the (1) terminal and three male spade connectors at the (15) terminal.

I have five female connectors that I need to attach. However, the Mittelmotor distributor has three wires, one that goes off to chassis ground, one that goes to the positive side of the coil (15) and one that goes to the negative (1).

I then have the +12V switched (black and blue wires) that goes to (15) and a pair of green wires. I'm not entirely sure, but I believe one is the tach, maybe the other is the fuel pump relay? In any case, they are supposed to go to the (1) terminal.

The problem is after I hook up the distributor and the +12V switched I have two green wires that need to attach to the (1) but only one connector each for the (1) and (15) terminals.

Like I said, this worked before. Clearly, something I've said up above is incorrect, but what? Either that, or I previously had EVERYTHING backwards, as three terminals on the (1) would solve my problem. But I don't think so. I'm remembering something wrong, but the only wiring instructions I have for the distributor say to do it the way I did it. I'm afraid if I do it wrong I'll fry something. For what it's worth, when I turn on ignition power the distributor powers up and connects to my phone. So that's running, at least.
_________________
-----------------------------------------
1982 931
1986.5 Silver 928S
2007 Hummer H3 (Daily Driver)

Past lives (I miss them all):
2004 RX-8 (Wrecked)
1993 RX-7 (Sold)
1987 RX-7 Turbo II (Sold)
1985 RX-7 GSL (Stolen)
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bureau13  



Joined: 07 Sep 2017
Posts: 412
Location: South Florida

PostPosted: Mon Dec 06, 2021 2:45 am    Post subject: Reply with quote

I've pretty much come to the conclusion that the coil was wired up backwards from the start. Either it was that way when I bought it or the replacement coil I bought has the terminals configured backwards when compared to the one I took out and I didn't notice. I found a picture of the car from the BaT ad and you can clearly see the two green wires on the same side as the green wire from the ignition amp (which I am replacing with the black wire from the Mittelmotor dizzy).

This begs the question as to what effects of a backwards coil I might have seen? If you recall, I was having problems with the car bucking under light throttle and this is actually why I swapped out the original coil, and then the dizzy. Hmmm....

But first things first, need to see if this thing will run now...
_________________
-----------------------------------------
1982 931
1986.5 Silver 928S
2007 Hummer H3 (Daily Driver)

Past lives (I miss them all):
2004 RX-8 (Wrecked)
1993 RX-7 (Sold)
1987 RX-7 Turbo II (Sold)
1985 RX-7 GSL (Stolen)
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bureau13  



Joined: 07 Sep 2017
Posts: 412
Location: South Florida

PostPosted: Wed Dec 08, 2021 3:22 pm    Post subject: Reply with quote

It's not starting. I think maybe I'm off a tooth, and maybe the distributor needs to be adjusted. It cranks, occasionally coughs like it wants to catch, and sometimes makes some odd sounds. I'm worried about those compression numbers but I'm not sure what would cause them all to be uniformly low like that. Unfortunately I run out of light by the time I'm out of work so I need to wait for the weekend.
_________________
-----------------------------------------
1982 931
1986.5 Silver 928S
2007 Hummer H3 (Daily Driver)

Past lives (I miss them all):
2004 RX-8 (Wrecked)
1993 RX-7 (Sold)
1987 RX-7 Turbo II (Sold)
1985 RX-7 GSL (Stolen)
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bureau13  



Joined: 07 Sep 2017
Posts: 412
Location: South Florida

PostPosted: Mon Dec 20, 2021 6:28 am    Post subject: Reply with quote

Re-timed the cams the way I used to do it (back of cam sprocket, notch/paint mark on crank pulley) and got the dizzy set where it looks right. Pulled the fuel pump relay and jumpered it (pump is definitely running now).

Cranks and that's it. No sign of life whatsoever. Whatever the opposite of progress is, this is it.

Completely serious here, what's an '82 924 Turbo worth that's all there and in fair condition, everything is there including fresh head rebuild that may or may not be correct because it won't start. Probably not much, but I'm about out of patience with this car.
_________________
-----------------------------------------
1982 931
1986.5 Silver 928S
2007 Hummer H3 (Daily Driver)

Past lives (I miss them all):
2004 RX-8 (Wrecked)
1993 RX-7 (Sold)
1987 RX-7 Turbo II (Sold)
1985 RX-7 GSL (Stolen)
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Fasteddie313  



Joined: 29 Sep 2013
Posts: 2421
Location: MI

PostPosted: Wed Dec 22, 2021 12:48 pm    Post subject: Reply with quote

Did you possibly put the cam sprocket back on backwards?


Iirc their are dots on both sides and if you accidentally put it onto the cam backwards then the dot won’t be correct..
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bureau13  



Joined: 07 Sep 2017
Posts: 412
Location: South Florida

PostPosted: Sat Dec 25, 2021 1:41 am    Post subject: Reply with quote

I did not, but good idea. I actually had a moment of "Wait which way does it go??" when reassembling but I double-checked that with the donor head, which was still mostly assembled, as well as some photos online.

Fasteddie313 wrote:
Did you possibly put the cam sprocket back on backwards?


Iirc their are dots on both sides and if you accidentally put it onto the cam backwards then the dot won’t be correct..

_________________
-----------------------------------------
1982 931
1986.5 Silver 928S
2007 Hummer H3 (Daily Driver)

Past lives (I miss them all):
2004 RX-8 (Wrecked)
1993 RX-7 (Sold)
1987 RX-7 Turbo II (Sold)
1985 RX-7 GSL (Stolen)
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bureau13  



Joined: 07 Sep 2017
Posts: 412
Location: South Florida

PostPosted: Mon Dec 27, 2021 5:42 am    Post subject: Reply with quote

I'm pretty convinced I am not getting spark. I put on a spark plug tester which didn't fire, but I'm not sure how well that thing works anyway, but the fact that I was at least getting some coughing and sputtering, and now, even with the fuel pump jumpered I'm getting nothing but cranking makes me suspicious.

I tested the coil resistance, primary (+ to -) is 1.6 ohms, which is fine, and secondary (+ to high voltage output) is 4.2 k-ohms, which I think is on the low side? I see comments that it should be between 5 and 15 k-ohms. Maybe that's close enough. I also get that exact measurement between the "-" and high voltage as well, but that's probably normal.

The Mittelmotor dizzy is turned so that the light is on (that's how you get it initially set, supposed to be good enough to start, then you adjust it with a timing light to set idle timing) and using the app, I can connect to the dizzy so I know it's powered up and running, at least.
_________________
-----------------------------------------
1982 931
1986.5 Silver 928S
2007 Hummer H3 (Daily Driver)

Past lives (I miss them all):
2004 RX-8 (Wrecked)
1993 RX-7 (Sold)
1987 RX-7 Turbo II (Sold)
1985 RX-7 GSL (Stolen)
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bureau13  



Joined: 07 Sep 2017
Posts: 412
Location: South Florida

PostPosted: Tue Dec 28, 2021 1:40 am    Post subject: Reply with quote

Of course, the best way for me to prove something wrong is by posting that it is true. I read some reviews for my spark tester, and they mentioned that it's hard to see in daylight, so I went out yesterday after dark and re-ran that test: I definitely have spark. Now, I don't know if it's strong or weak or whatever, but it's there.

I'm positive my timing is not way off (uh oh ) so that leaves fuel. And while I thought I had proven that fuel is getting there, I think today's project will be to get there more definitively.
_________________
-----------------------------------------
1982 931
1986.5 Silver 928S
2007 Hummer H3 (Daily Driver)

Past lives (I miss them all):
2004 RX-8 (Wrecked)
1993 RX-7 (Sold)
1987 RX-7 Turbo II (Sold)
1985 RX-7 GSL (Stolen)
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bureau13  



Joined: 07 Sep 2017
Posts: 412
Location: South Florida

PostPosted: Tue Dec 28, 2021 5:26 am    Post subject: Reply with quote

Well, my cold start injector seems to be working. I pulled it, jumpered the fuel pump and cranked, and I got a brief spurt of gasoline. So, regardless of the possibility of off-timing, regardless of the rest of the injectors, regardless of possibly low compression, SOMETHING should happen, no? Something other than the starter turning over the motor? There's just no sound of anything even considering being ignited (which was not true initially, fwiw). That makes no sense. At a minimum, I have spark at one plug (no reason to believe that's not four, I just tested on) and gas from the cold start valve (again, no reason to believe the main injectors aren't also working, I just haven't pulled them to observe). But shouldn't that minimum case cause some sign of life???
_________________
-----------------------------------------
1982 931
1986.5 Silver 928S
2007 Hummer H3 (Daily Driver)

Past lives (I miss them all):
2004 RX-8 (Wrecked)
1993 RX-7 (Sold)
1987 RX-7 Turbo II (Sold)
1985 RX-7 GSL (Stolen)
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Carrera RSR  



Joined: 08 Jan 2010
Posts: 2241
Location: Somerset, UK

PostPosted: Thu Dec 30, 2021 8:12 pm    Post subject: Reply with quote

In the past when the fuel system has been drained I've found I have had to bleed the fuel to injectors which means cracking them open at the fuel pipe to injector joint and running the fuel pump until some fuel pushes out most of the air trapped post fuel distributor. That confirms all injectors are getting fuel and no air in the system that could stop the injectors opening.

As for spark, the beauty of RHD and S1 is I can loosen the dizzy, reach in to the cabin and turn the key whilst rotating the dizzy back and forth to get some timing to spark the car into life then retime it via a strobe when fully warmed up.

Both have worked for me many a time.
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1980 931 - forged pistons, Piper cam, K27/26 3257 6.10 hybrid turbo, 951 FMIC, custom intake, Mittelmotor dizzy & cam pulley, H&S exhaust, GAZ Gold, Fuch'ed, Quaife
Now www.924board.org/viewtopic.php?t=34690
Then www.924board.org/viewtopic.php?t=31252
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bureau13  



Joined: 07 Sep 2017
Posts: 412
Location: South Florida

PostPosted: Sat Jan 01, 2022 2:45 am    Post subject: Reply with quote

That's interesting...I thought maybe I flooded it, I could smell gas on the plugs, so I dried everything out but no change. Maybe I just got some vapors. I'll try the injector line bleed thing.

I will have to recruit a helper for the dizzy-twist-while-cranking, but I've got a couple candidates...I'll try that too.

Thanks

Carrera RSR wrote:
In the past when the fuel system has been drained I've found I have had to bleed the fuel to injectors which means cracking them open at the fuel pipe to injector joint and running the fuel pump until some fuel pushes out most of the air trapped post fuel distributor. That confirms all injectors are getting fuel and no air in the system that could stop the injectors opening.

As for spark, the beauty of RHD and S1 is I can loosen the dizzy, reach in to the cabin and turn the key whilst rotating the dizzy back and forth to get some timing to spark the car into life then retime it via a strobe when fully warmed up.

Both have worked for me many a time.

_________________
-----------------------------------------
1982 931
1986.5 Silver 928S
2007 Hummer H3 (Daily Driver)

Past lives (I miss them all):
2004 RX-8 (Wrecked)
1993 RX-7 (Sold)
1987 RX-7 Turbo II (Sold)
1985 RX-7 GSL (Stolen)
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View user's profile Send private message
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