Testing electrics without engine in
#16
Former Vendor
I'm confused about what is being said.
I thought that power for the relay board came from the extra red wires at the positive battery post and not from the positive connector at the front (by the 14 pin connector.)
I thought that power for the relay board came from the extra red wires at the positive battery post and not from the positive connector at the front (by the 14 pin connector.)
#17
Instructor
Thread Starter
Mine is an unloved '79 with the engine out, not sure if the early cars are difference, or if its been altered... but there is only a single red wire coming from the battery to the starter motor.
#18
Rennlist Member
Your 79 should have a single black 35mm2 cable running to the starter motor as do the later S4/GTS models. From the starter motor you should have a red 10mm2 cable taking power across to the alternator and then up to the hot post where the cable splits into three parallel paths each with a red 4.0mm2 cable that powers bus 30 [the live bus] in the CEL. The S4/GTS models do something similar only they have a 16mm2 cable through to the alternator and the hot post and that then splits into two x 10mm2 cables to bus 30. The later models have more electrics on them. The S4/GTS's have a separate 4mm2 cable to the ABS post and they also have separate feeders from the battery to the likes of the twin fans and several other users such as the MFI relay- why that is run separately to the CEL I have no idea but then I do not see why they had to run cables out to the hot post and then back to the CEL in the cabin- somewhat baffling as a design feature if they could have avoided routing via the engine bay. ..
#19
Instructor
Thread Starter
Your 79 should have a single black 35mm2 cable running to the starter motor as do the later S4/GTS models. From the starter motor you should have a red 10mm2 cable taking power across to the alternator and then up to the hot post where the cable splits into three parallel paths each with a red 4.0mm2 cable that powers bus 30 [the live bus] in the CEL. The S4/GTS models do something similar only they have a 16mm2 cable through to the alternator and the hot post and that then splits into two x 10mm2 cables to bus 30. The later models have more electrics on them. The S4/GTS's have a separate 4mm2 cable to the ABS post and they also have separate feeders from the battery to the likes of the twin fans and several other users such as the MFI relay- why that is run separately to the CEL I have no idea but then I do not see why they had to run cables out to the hot post and then back to the CEL in the cabin- somewhat baffling as a design feature if they could have avoided routing via the engine bay. ..
#20
Instructor
Thread Starter
Happy to report that it worked !
Jumper lead from Starter positive to the enginebay jumper post (both carefully insulated against shorts). Turn key and various lights appear on dash... but importantly, I hear the fuel pump buzz for about 3 seconds (I assume thats a priming phase?). I repeated a few times and its consistent. Then I remove the battery ...
Thanks as ever
Todd.
Jumper lead from Starter positive to the enginebay jumper post (both carefully insulated against shorts). Turn key and various lights appear on dash... but importantly, I hear the fuel pump buzz for about 3 seconds (I assume thats a priming phase?). I repeated a few times and its consistent. Then I remove the battery ...
Thanks as ever
Todd.
#21
Former Vendor
Thanks for the clarification.
#22
Electron Wrangler
Lifetime Rennlist
Member
Lifetime Rennlist
Member
Later years with electric fans do have direct feeds for the fans (to the fuse) from the battery. Depending on year/equip there are also direct feeds for the ABS/PSD/ECU's/Telephone - none of these use main CE power. The 'additional' direct battery supplies that go to the CE panel enter at the plug connectors at the bottom.
This engine out connection scheme is good for all years.
Alan
PS note that this means that although the engine being out removes main power to the CE panel - there are still some things powered there if the battery is still connected - so be careful.
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Todd Gibbs (04-19-2022)