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1977 Project non runner

 
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mrborrie  



Joined: 09 Jun 2021
Posts: 29
Location: Netherlands

PostPosted: Mon Aug 09, 2021 5:19 pm    Post subject: 1977 Project non runner Reply with quote

Hi All,

I bought a 1977 924 off a friend of mine who drove it into storage 2 years ago. When i got it the car would not ran, tank was pretty much empty.

Filled it up and it would now start very rough and die instant.

https://www.youtube.com/watch?v=EUNenZ7Mjpc

Now one month later i got my lift installed and now it wont even idle rough (was no fun pushing it on via my garden XD)

I did notice that the fuel pump wont make a noise when contact is on (and during start i dont hear anything ether)

And what i could not find in the Haynes manual is that the fuelpumpwire has been sliced and has 2 connectors to the tank ?! (they where undone, i put them back)


I have done allot of reading on the forums and i think my next steps are to bypass the fuel relay to see if the pump (or is there a intake pump too?) will start making noise.

Why the post? well i am looking for the joined forced of knowledge of the internet for good tips. I am pretty know with old Volvo’s but this is my first Porsche (next to a 986 I had a while ago) and back in the day I shared my knowledge on those things on forums. Hope to find a enthusiast willing to guide me through this.
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morghen  



Joined: 21 Jan 2005
Posts: 8947
Location: Romania

PostPosted: Mon Aug 09, 2021 7:36 pm    Post subject: Reply with quote

If it starts but does not idle you may have a vacuum leak somewhere in between the air metering unit and the throttle body.
If it sat dry the fuel distributor could be a bit stuck but that should start working better and better once you put gas into it.
Look for vacuum leaks, split rubber parts, not tightened rubber parts..etc.

If it does not even fire once, see whats up with the fuel pump, it should run when ignition is turned on, then stop after a few seconds...or run continuously if relay has been hacked.
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mrborrie  



Joined: 09 Jun 2021
Posts: 29
Location: Netherlands

PostPosted: Mon Sep 23, 2024 1:52 am    Post subject: Reply with quote

I had a 924 expert come over for a visit and he mentioned that i have the wrong relay in there.

The older models (4 speed ones) had a different fuel relay (477 906 059) with a fuse in there.
This one: https://rareporscheparts.co.uk/products/porsche-924-dme-relay-with-fuse-tester-477-906-59

The jump wire relay hack wont work on these models, this was news too me.

Since this relay is even more rare than the later ones i am looking to rewire it.

With the fuel pump directly wired the car starts and keeps running as you keep the key in starting position.

However the second you let it go the spark gets cut, I think perhaps the direct wiring of the pump and a direct wire to the coil could be a hack?

I am not the first to figure this out i am sure so any tips are welcome!
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mrborrie  



Joined: 09 Jun 2021
Posts: 29
Location: Netherlands

PostPosted: Mon Sep 23, 2024 2:34 am    Post subject: Reply with quote

Car is running again! Yes the old style relay can be hacked by powering the coil directly
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copeina  



Joined: 06 Dec 2023
Posts: 13
Location: Calgary, AB, Canada

PostPosted: Wed Sep 25, 2024 12:00 am    Post subject: Reply with quote

mrborrie wrote:


The jump wire relay hack wont work on these models, this was news too me.


The jump wire hack works if you unplug the connector on the airflow meter box and jumper it. I've got a 77 and I'm using a "normal" relay which just takes power with the ignition rather than through all the other inputs. Noticed when the air plunger raised, the pump cut out. Unplugged that connector, installed a jumper and all is well.

$5 relay available at any parts store. Fuel pump won't shut off if you crash and it stalls, but you've got bigger problems that day.

/Kris
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mrborrie  



Joined: 09 Jun 2021
Posts: 29
Location: Netherlands

PostPosted: Fri Sep 27, 2024 4:45 pm    Post subject: Reply with quote

I found said switch under the airbox indeed. What does this switch do. does it keep the fuelpump from going on?

I am asking because i drove the car around with a separate battery indeed on the pump because no power on the OEM lines even with the newer style relay in there and the "coil" hack.

It could also be a fuse they hacked in somewhere since the OEM relay had a fuse and with this hack its gone.


Can you confirm for me what this switch does in the system?




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copeina  



Joined: 06 Dec 2023
Posts: 13
Location: Calgary, AB, Canada

PostPosted: Mon Sep 30, 2024 11:40 pm    Post subject: Reply with quote

mrborrie wrote:
I found said switch under the airbox indeed. What does this switch do. does it keep the fuelpump from going on?


LOL - I honestly have no idea how it is wired into the system. Someone sent me a schematic when I asked, and I just politely thanked them. Pre-78's are different in more ways than one.

I know the relay jumper hack / simple relay bypasses the distributor part of the circuit which makes sense, but that airbox thing seems to work contrary to expected. All I know is that once I had the fuel pump running, it would shut off when the air plunger lifted. Unplugged that connection, jumpered it and the problem went away.

My car looks good, but has enough issues that it will never be a candidate for restoration. I kept the unplugged connector ziptied nearby so if it ever needs to be looked at, at least the location is relatively intuitive. Goal is just to drive it and enjoy!

Not sure that helps, but it explains what mine was experiencing. Good luck!
/Kris
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Raize  



Joined: 18 Sep 2013
Posts: 236
Location: Scotland

PostPosted: Tue Oct 01, 2024 12:22 am    Post subject: Reply with quote

Is that not the hot start solenoid though? I thought the plate microswtich was a blue connector directly on the airbox for the cars that had it...

The hot start solenoid drops the control pressure to zero when it's fired, so I guess if it was incorrectly constantly fired, it would shut off your car when the plate lifts due to giga-rich fuelling.
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!tom  



Joined: 28 Aug 2006
Posts: 1939
Location: Victoria, BC Canada

PostPosted: Wed Oct 02, 2024 2:39 am    Post subject: Reply with quote

I did some diagnostics with how the fuel pump relay works in my car.

You can see the topic here: https://www.924board.org/viewtopic.php?p=289747
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mrborrie  



Joined: 09 Jun 2021
Posts: 29
Location: Netherlands

PostPosted: Mon Oct 14, 2024 3:53 am    Post subject: Reply with quote

Thanks for that topic, i had some issue again this weekend.
Fusebox and all the pins have some corrosion from being parked so long.
Its funny there in not allot of electronics in this car but what is there keeps on giving

We wont give up though. This time it was pin 15 for the coil perhaps ll directly wire that one too, switched 12V will do iirc
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