924Board.org

Clbmkr1 · Joined: 21 Jul 2010 Posts: 76 Location: Wind Point, Wi.

I bought a 1980 931 a week ago. The car is in good, original condition; 77,000 miles. I'm the 3rd owner.
Everything seems to work, except it won't start. When I turn the ignition on the fuel pump doesn't run. If I pull the pump relay and put in a jumper wire between #30 & #87 the pump will run. When I check the signal between #15 and #1 with the ignition on, I get 12 volts. I bought a new relay, but it still won't start.
The fuse is good. What am I missing?
_________________
Jim Baldwin
1980 931
2013 Lincoln MKZ
2013 Ford Escape

Grenadiers · Posted: Mon Jul 26, 2010 12:52 pm Post subject:

Might be the 14 dollar ignition switch not working. As I recall, the jumper you did allows the fuel pump to run regardless of switch position.
_________________
'83 944 Track car.
'88 924S Track car.
'89 944 Turbo
2004 Winnebago Vectra monster RV
2012 Jeep Wrangler
2014 Kia Soul
2001 Ford F350 powerstroke

Paul · Posted: Mon Jul 26, 2010 1:12 pm Post subject:

Welcome to the board, you seem to have fuel, do you have spark?
_________________
White 87 924S "Ghost"
Silver 98 986 3.6l 320 HP "Frank N Stein"
White 01 986 "Christine"
Polar Silver 02 996TT. "Turbo"
Owned and repaired 924s since 1977
Porsche: It's not driving, it's therapy.

Smoothie · Posted: Mon Jul 26, 2010 3:28 pm Post subject:

Possible weak/non-existing elect. connection at the overboost pressure switch..? During normal operation, it completes the circuit to ground the fp relay.
[See "manifold pressure limiting switch" here on current track 23 (ignore current tracks 11 through 17 - that's '81-'82 S2 DITC ignition-specific stuff) - http://farm3.static.flickr.com/2193/2399050926_b6825efef7_o.jpg ]
_________________
"..it's made in Germany. You know the Germans always make good stuff."

'82 924T, US version, dark green metallic, 5 speed Audi 016G gearbox

Clbmkr1 · Joined: 21 Jul 2010 Posts: 76 Location: Wind Point, Wi.

Hey Guys, thanks for the quick response.
I've wondered about the ignition switch, but it does give a voltage reading at the relay in the "on" position.
The manifold pressure limiting switch is something I haven't checked. I don't know why, it's right there on the schematic. Is this the switch just before the Throttle Body? I'm assuming it is a "normally closed" switch, opened by excess pressure from the turbo. If I pull off the connector and check the resistance of the switch, this will tell me if its open or closed?

Thanks again for you advice.
_________________
Jim Baldwin
1980 931
2013 Lincoln MKZ
2013 Ford Escape

ideola · Joined: 01 Oct 2004 Posts: 15550 Location: Spring Lake MI

Just ground that connection out for now while you're trouble shooting to eliminate the switch as a variable. Make sure you have a GOOD clean ground. I connect mine to the alternator chassis, as it's nearby and typically grounded pretty good. The switch itself could be bad, or the wire could be bad, so make sure you inspect the wire itself as well as you can before it disappears in the wiring harness.
_________________
erstwhile owner of just about every 924 variant ever made

Clbmkr1 · Joined: 21 Jul 2010 Posts: 76 Location: Wind Point, Wi.

OK, I disconnected the lead from the boost pressure control switch. The switch is closed to ground using a meter. I jumped the lead to ground, using the alternator ground as suggested.
Still, when the ignition is turned to the on position, the fuel pump doesn't run. Turning the key to start, the engine turns over but doesn't fire.
How's the easiest, safest way to check for spark?[/img]
_________________
Jim Baldwin
1980 931
2013 Lincoln MKZ
2013 Ford Escape

Paul · Posted: Tue Jul 27, 2010 11:46 am Post subject:

Did you try to start the car when you jumpered the fuel pump relay?

In regards to spark, just pull the coil wire at the distributor and lay it on the valve cover and crank the car.
_________________
White 87 924S "Ghost"
Silver 98 986 3.6l 320 HP "Frank N Stein"
White 01 986 "Christine"
Polar Silver 02 996TT. "Turbo"
Owned and repaired 924s since 1977
Porsche: It's not driving, it's therapy.

Clbmkr1 · Joined: 21 Jul 2010 Posts: 76 Location: Wind Point, Wi.

I did try to start it after jumping the relay. It fired the first time, but not since. I didn't get a spark from the coil wire.
_________________
Jim Baldwin
1980 931
2013 Lincoln MKZ
2013 Ford Escape

fiat22turbo · Joined: 18 Jan 2006 Posts: 4040 Location: Portland, OR

go back through your grounds and read, then re-read the 931 ressurection thread and try the jumpers on the relay, the switch and the pressure switch. Then start troubleshooting from there.
_________________
Stefan
1979 924 Carrera GTS (clone-ish)
1988 944 Turbo S (Silver Rose)

Clbmkr1 · Joined: 21 Jul 2010 Posts: 76 Location: Wind Point, Wi.

Thanks, I'll keep at it......
_________________
Jim Baldwin
1980 931
2013 Lincoln MKZ
2013 Ford Escape

Clbmkr1 · Joined: 21 Jul 2010 Posts: 76 Location: Wind Point, Wi.

I still haven't discovered why the fuel pump won't run with the relay installed. I've checked both of the pump relays I have and the both close when power is applied to 31 and 15. I have a switched jumper between 30 and 87 to operate the fuel pump manually. I assume the pump is designed to run continuously since there isn't a pressure switch in the system.

I decided to check the distributor and rotor. All components look to be brand new, no sign of arcing or carbon. I noticed the distributor cap was 180 degrees off in orientation, the postioning tab wasn't engaged leaving the cap able to move.
I pulled the plug wires off of the cap and repostioned it to the proper position and locked it in place. I reinstalled the wires, (1, 3, 4, 2), beginning with #1 at back-right position, moving clockwise in the order.

Now when I try to start the engine it backfires through the Air Flow Sensor.
Today I'll check the timing. rotate the engine to TDC and assure the rotor is in the #1 position.

Any and all continued advice is welcome and appreciated.
_________________
Jim Baldwin
1980 931
2013 Lincoln MKZ
2013 Ford Escape

Smoothie · Posted: Mon Aug 02, 2010 1:10 am Post subject:

Clbmkr1 · Joined: 21 Jul 2010 Posts: 76 Location: Wind Point, Wi.

OK, its running. The rotor, at TDC, points to the #3 wire position on the distributor cap; 1/4 turn clockwise from the proper position. I reconfigured the plug wires from that starting position and it fired right up. I took a couple of laps around the neighborhood, then back in the garage. It needs the timing set and 2 years of cobwebs blown out and I think it will be fine. Now its on to a/c, window, and wipers.

I saw the adjustment for the distributor angle; what's the purpose?

Thanks to all for your help and support.
_________________
Jim Baldwin
1980 931
2013 Lincoln MKZ
2013 Ford Escape

Smoothie · Posted: Thu Aug 05, 2010 12:49 am Post subject:

The other angle is apparently for use with another application of the distributor holder - when it was installed in an Audi or something else...
_________________
"..it's made in Germany. You know the Germans always make good stuff."

'82 924T, US version, dark green metallic, 5 speed Audi 016G gearbox