924Board.org

[BWW]

Happy New Year to everyone here. I'm having an issue I could use some help with. I have a 1981 931 I'm trying to get running. The engine and transmission have been recently rebuilt, so it should be great once I can get it going, but I'm not there yet. I've been having issues with fuel pressure. It wasn't working for a while, then I swapped out my DITC with a spare I had and it worked. However, when I went out to work on it today, there's was once again no pressure when cranking. The tach is bouncing and there is pulsing voltage at the ignition coil. Also, I recently swapped out the fuel pump relay just to be safe, but to no avail. Finally, I checked the wiring back to the fuel pump by jumping across 30 and 87 and that is fine. I also checked the connections between the DITC pins and the other parts of the car and they seemed fine. Connections between the DITC pins and wires also seem solid. Any ideas on what could be at the root of this? Any input would be much appreciated!

[Fasteddie313]

First I would be all over checking grounds..

Battery-engine-chassis big grounds..
Fuel pump grounds to a “ground crown” under the carpet behind the left rear tail light..
Connections at the fuel pumps themselves..
The ends of the fuses and the contacts in the fuse panels that the ends of the fuses touch..

Would be my first suspicions ..
_________________
80 Turbo - Slightly Modified

[BWW]

Thanks for the tips. I will give this a try. Fingers crossed!

[BWW]

So I checked the grounds and everything seems to be in order. I was advised to next try hotwiring the car to eliminate the possibility of a bad ignition switch. I have read on another post that this can be done by jumping 15 to 30 and then touching 30 to 50 to engage the starter, but I'm not sure which number is which and I can't find any indication on either the switch or the connector...

[Eliza]

Hi Brent!

when I told you to try and hotwire, I never thought to send you a picture of the plug - I can see the pin numbers per terminal on mine .

Anyways, here's one off of the interweb where you can see which terminals are 15, 30 and 50.



Good luck!

Eliza
_________________
1985 924 NA RoW
1981 931 S2 RoW

[BWW]

Thanks, Elisabeth! You're the best. What would I do without you?

Unfortunately, mine doesn't quite look the same as what you posted. I'll email you a picture, since I can't post them here.

[Eliza]

Hi Brent,

check your email. I was posting the promised picture indicating how to hotwire then thought, maybe not on a public forum.

Imagine somebody illwilled reads my post then goes and steals my car because I kindly showed them exactly how to do that

Eliza
_________________
1985 924 NA RoW
1981 931 S2 RoW

[BWW]

So...where do you park at night, Eliza?

[924RACR]

Pretty sure instructions to hotwire the cars are in the Tech Section linked above...

EDIT: Now I can't even find it myself... and I put it in there... dammit.
_________________
Vaughan Scott
Webmeister
'79 924 #77 SCCA H Prod racecar
'82 931 Plat. Silver
#25 Hidari Firefly P2 sports prototype

[BWW]

Thanks for this. I'm pretty sure most of the answers to my questions are somewhere in this forum. The problem is finding them!

[924RACR]

Ah. Yeah, I hid it, it's in the Tech Section, Bodywork section, in with how to replace the switch.
_________________
Vaughan Scott
Webmeister
'79 924 #77 SCCA H Prod racecar
'82 931 Plat. Silver
#25 Hidari Firefly P2 sports prototype

[BWW]

Thanks, 924RACR. I will keep this in mind for future reference.

[BWW]

I finally got a chance to trying the hotwiring trick. I'll start with the good news. I had fuel pressure again when I did this. What's confusing is after I reattached the connector to the ignition switch and tried to start it with the key, I still had fuel pressure. I'm not sure what's causing the fuel pressure to come and go like this. Additionally, the car still won't quite start and keep running. It fires and sputters when cranking but won't keep going once the key (or the wire when hotwiring) is released. Any ideas would be greatly appreciated!

[924RACR]

Almost makes me wonder if you're only getting power to the coil or ignition in crank position/through the crank circuit?

Just to be clear, when 15 and 30 are jumped it will not run, only when 50 is included? Because normally that failure is in the ignition switch itself, but OTOH there is a circuit from the starter to power the coil at 12V for cranking/easier start... normally the coil will run only at 6V, and is designed for that. Almost makes one wonder indeed if in fact your coil is dying, and can only provide a good spark with 12V.

Would be worth checking the voltage supplied at the coil and to the ignition controller (forget if this is S1 or S2, so depending there) is correct or not.

Might also be worth jumping 12V to the coil (terminal 15) directly from the battery, and trying to start then, see how that works.
_________________
Vaughan Scott
Webmeister
'79 924 #77 SCCA H Prod racecar
'82 931 Plat. Silver
#25 Hidari Firefly P2 sports prototype

[BWW]

I hadn't thought about that. In answer to your question, that is correct. It seems to want to start and run when 50 is connected, but as soon as I let go it stops. I've posted a video here so you can hear what it sounds like. (Sorry for the quality; I was recording while also hotwiring.)

I didn't know that about the ignition coil, but it does explain things. This car is the S2. For the sake of clarification, you are suggesting I run power from the battery to terminal 15 on the ignition switch wiring, correct? If so, would I still want to connect 30 with 15?

Many thanks for the help! I never would have gotten this far without you and Eliza.

https://isu.box.com/s/yy4wf3ysiy4tsu0p0gu7gx69c6xk6zh1