Newb 944S LS1 Conversion

The old pics you dug up seemed to show the wire from the firewall but not so much of seeing where it appears on the mess of other connections to the positive terminal.

But you've already passed this point so its a big help to hear that everything except the obviously already tied to ground and negative post goes on that side. so kitchen sink it is to the positive!

It also makes more sense that if you both to go into the battery compartment that you wouldn't just go to the ground point there as there are many ground points with the battery.

Still kind of curious, what the wire from the firewall actually heats up but not curious enough to rip it apart. Would rather keep building.

One thing i fear i threw out years ago is what holds the battery down in this compartment via the stud retainer on the bottom. Probably back to fabricating something to keep it from shifting/moving.

That is one of the main power wires for everything inside the car. It does go to the positive terminal.

I’m out and about in SoCal but later today, I’ll send you some pics that show how I made a nice battery hold down clamp from a bathroom towel hook!

UPDATE:
Got back to the hotel for a bit so here's the scoop on the battery hold down.   I too "misplaced" the factory unit.  As I was looking for some scrap metal to fabricate a hold down, I came across and ordinary brass plated bathroom robe hook (not really a towel hook but it could be!).

Readily available at Home Depot:  [You must be registered and logged in to see this link.]

The size was just right and all I needed to do was drill a hole in it to accept the hold down stud protruding from the battery box floor.  I'm thinking this stud was M6 x 1.25 with a 10mm nut, but don't quote me on that.  It appeared to be made of "pot metal" so I had to be gentle with it.

The battery has a beveled flange on both sides so to assure I drilled the hole in the proper place, I slid the battery over to the PS side fully engaging the built in flange catch on the floor of the battery box. Then, I measured to see where the hole needed to be in the robe hook for proper engagement of the battery flange on the DS of the battery.

I found a matching locking flange nut for the hold down and tightened it snug....perfect!

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< Robe Hook and Nut >                                                         < Final Install >

It would not be difficult to fabricate a custom hold down clamp, but this was a really simple alternative.

will most likely go the exact same route and now have another to look for when i scout out my battery in terms of this bottom plate for the hook to squeeze on to.

Great stuff raymond.

Simple continuity test with a meter will tell you which are grounds.

assuming i have everything hooked up... the continuity test would work.

Just have to hook up your main engine ground.

Finished harness taping the new loom for the coolant temp wire to the gauge, oil pressure send to the gauge, and ignition wire. Then I got a type 96R battery for a mustang from costco and got everything landed on the post terminals.

Scabbed in the fused battery lead to the ecu since I need to get some 12awg and do that properly just to be able to see the dash light up for the first time in 14 years. Wow did that ever bring a grin to my face after losing the 4 banger block back in 2009 it had been a long time since i saw the inside come back to life. Forgot how good the infinity plate speakers sounded in this thing, was a real treat to see it come back from the dead. Also tried a crank of the engine to make sure all is good with the solenoid and starter and all good! crazy how torquey and large the engine seemed in just cranking it over. This thing with the borla S type fed by the flowmaster Y scavenge is gonna sound pretty grizzly with this 222/224 112 lobe cam.

can't wait till i get the last of my checklist complete for the first fire party.

i remember reading ray's post of when he first turned the key to see his car come back to life after so many years and coveting that moment. So awesome to experience the same thing after 3 long years of putting one day of the weekend on the project to slowly eat the elephant one bite at a time.

Just have to cut my IAT sensor in to complete the intake and make a bracket to make sure it maintains that finger separation from the belt; mount the ecu and wrestle the firewall boot on, flush old brake fluid out, then drain and bleed brakes/clutch/power steering as best as can; flush fuel through quick connect into a bucket as well as a function test for fuel pump circuit; fill coolant, fill transaxle with oil.

should be good to fire up after that with a bunch of neighbors over to celebrate and then torque up tie rod to torque spec, torque up suspension points on torsion bar from when i removed the torque tube for rebuild, attach sway bar and torque up and then follow Ray's great how to on using the dowels to put the new greased up cv joints on the 4130 chromoly half shafts Rob (xschop) made me ions ago back in 2013.

at some point i think i am going to make a new chronologically arranged thread going through all the progress pics of my build to help someone who may have run into what i did for the first year of my project where i literally had no idea where to start and what step to do next while worrying about potentially missing one or doing one out of sequence that would make me do rework.

ended up performing a tonne of rework as part of the learning process which is arguably normal for a first time LS swap let alone this conversion.

List is getting real short of things left to do before first fire.

1. Have to extend wire for battery connection of ecu to add on to the pile of positive battery taps.

2. have to follow raymond's thread to complete the vacuum lines. looks quite simple just have to get some 5/16 fuel line, maybe some larger heat shrink, and a few hose clamps. will have to check the extra vacuum line i had for redoing the porsche vacuum lines before the original block blew up and whether that will work with what seems like two dimensions of hard vacuum line.

3. My AR transaxle has the oil cooler and it seems like it could be much more difficult to have the transaxle full of fluid and cooler installed to then try to put the half shaft and cv boots in. So seems best to at the very least get the passenger's side done so i can put the oil cooler back in and then fill with gear fluid as I don't want the torque tube spinning the transaxle input shaft with no oil in it even though its not in gear. Guess i just have to finish it all lol.

4. This EGR thing has me a little perplexed and slightly frustrated although it wouldn't be the first time i got news of "oh, you'll have to redo that or pull that back out". But maybe there's a somewhat quicker fix? I can see the return line back by the fuel tank, thinking i could just put a fuel filter there and that would allow the pump at the gas station to not click and burp at me on fill up and although i realize it could be venting off fuel fumes with it being at the back of the car i'm not sure it's really much of a danger compared to it being under the hood and filling the engine bay close to the spark plugs? would this work? or do i really have to split open my ecu, add 2 wires, put them in yet another loom and fish them through firewall hole and then get the EGR part and pigtail that Raymond listed in his thread on page 9 i think and feed it to the intake manifold port? i have hptuners so should be easy enough to buy the 6 credits to access read/write to the tune (will need to do this eventually) and change the EGR setpoint if required.

Guess i'm just wondering if i can save myself time effort and more parts by tucking a fuel filter at the back for the return for it to breathe cause i thought the only concern was filling the engine bay but at the back i don't think it would be much of an issue. My garage already smells like fuel after shut off from my frs with the cats deleted and aggressively rich fuel map to keep the turbo happy on the aggressive timing soooooo no difference?

it's already gonna be quite a bear to force my harness firewall boot on over the wires coming out of there let alone having to put it upside down with the way the looms spill out, another loom added is just gonna make it worse.

thoughts/warnings/finger wags of don't do that?

Do not put a filter by the tank. It is too low and you will have gas pouring out of it on fill up and cornering. Ask me how I know..........

If you still have the original 944 tank vent valves on the drivers side strut tower, then you can put the vacuum hose on that and plumb a line from the vent valve on the strut tower to the nipple behind the throttle on the left side of the intake. It will then work like Porsche made it. If you don't have that valve setup, then just put a filter on the hose in the engine bay. I've run them that way for years and never had an issue.

ok.... so very very glad i asked before i proceeded with my fuel filter in back near the gas tank idea. lol
and know i won't ask how you know

so it appears i was once again quite hasty on the demo of the old motor and must have chucked the tank vent valves not even knowing what they were or what they did. ooops.

i do still have the grey hose going into the fender but also really good to know that it goes to the charcoal canister and not just a drain drop hose for moisture to escape. Guess i should not put my coolant overflow hose into that lol.

But I still have a question.

if i just put a fuel filter on the grey hose going to the charcoal canister that just makes it so the abandoned charcoal canister doesn't fume back but truly it's disconnected entirely is it not? cause i don't have the old return line to feed it vapors so with it being dormant for 13 years there shouldn't be anything happening at all no?

secondly, to fix the burping while filling issue don't i need to run a new line from the old fuel return to the canister's grey hose to connect them together and then air inside the gas tank with fuel vapors can be forced to the charcoal canister as the tank is filled with gas?

picture of hardline on the fuel return on the passenger's side of the torque tube bellhousing that i think i need to run new to pick up the charcoal canister grey hose for reference. (run new because i have removed that line many moons ago with advent of engine being in the car and many other subsystems now tied in and complete. didn't throw it out but i doubt it would go back in with all the new harness wires in the way and such.)

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I've never had an issue with the burping while filling, with just a filter on that line. With the tank vent valves not there it should just vent to atmosphere.

Heres a link to look at too

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FYI, these battery hold downs are still available.

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Gutterboy wrote:.... so it appears I was once again quite hasty on the demo of the old motor and must have chucked the tank vent valves not even knowing what they were or what they did. ooops.

Looks like you are making good progress!

Just in case you have a box full of old parts laying around, below is what the factory Porsche vapor recirculation valve assembly looks like.

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< Factory Porsche Vapor Recirculation Valve >

From various thread comments, simply "connecting" the fuel tank vent line to the charcoal canister will provide the pressure release you're looking for.  Without it, adding (or removing) fuel from the tank creates positive or negative tank pressure respectively.  Both are bad, but the positive pressure creates the "burping" effect you mention.  Negative pressure reduces the efficiency of the fuel pump and subsequent fuel volume delivery.

The recirc valve arrangement is just to meet EPA emission standards by allowing the engine to burn off a percentage of tank fumes without creating negative tank pressure.

Hotrodz of Dallas wrote:FYI, these battery hold downs are still available.

Good to know Bob.... though not as "shiny" as my bath robe hook!

k so after reading the rennlist link, and re-reading your post several times perhaps i'm mistakenly envisioning a tiny lawnmower air filter but what's supposed to be an inline fuel filter installed from the extension of that vapour return hard line left of my torque tube bellhousing going into engine bay and then connecting to the charcoal cannister on the other end and mounting said in line fuel filter more at the the point of where the charcoal hose begins in absence of my vapor control valves being thrown out?

basically if there were any fuel to travel to front it gets soaked up by filtering material in filter but most of the time the vapors just get filtered and any left over the charcoal canister absorbs?

do i need to open fender well to make sure i get a vacuum confirmed on the charcoal canister? with all the valve controls removed its possible i unknowingly yanked that out to without knowing the vacuum line on the charcoal canister had to stay?

sorry, i've gotten too lazy with relying on Raymond's eighty billion pictures for me to learn by visually seeing everything. without them i've been doing a lot of guesses. turns out that between conversations with you and kent and other posts by raymond alot of my guesses have been pretty wrong lol.

There isn't vacuum at the carbon cannister. It is simply in-line from the tank to the original vent valves. It will absorb most of the fumes coming from the tank. Excess fumes and, on the rare occasion, wet fuel, will go out of the cannister behind the left front tire, through a drain hose. Only real reason for the filter on the end of the hose in the engine, is to keep trash out of the system.

K I think I finally get it with the keeping the trash out comment.
So really you could either just bother with a hose line all the way to the hose from. The canister to complete the vent return or just simply plug the return inlet at the mouth of the engine bay with said fuel filter? Or does it need to come up so that a full tank doesn't also spill out there from being lower than the height of the tank?

Also seemed pretty weird on the rennlist thread that some were just putting a check valve at the tank. If you put it towards the tank it could only pull fresh air in and still pressurize. Don't see how that works

As long as its in the engine bay, then its high enough to not cause problems.

I didn't get the check valve thing either

so put the fuse back in the fusebox to see if i could hear the pump turn on now that i have a battery and can start going through all the electrical tests to get ready for true first fire.

turn to accessory and nothing, leave the key on in accessory and lift the car up and undo the connector to the fuel pump and no voltage.

so then i do an advanced search and find a few different ideas including a super old post of arthropraxis using jumper wires in his fuse box to heat it up from the LS pin 9 ECU wire and then also this post/caption.

i'm just curious if a better or more obvious way is done now as many things change over the years on these conversions and in the wiring part of the wiki it shows pin 5 on the 14 pin connector but then says "not used"

i'm also confused by the captions instructions to pick up 87 on pin 2 or 3 for switched power which would be the same as what i have my pink wire going to already on pin 3; but then hooking 87b to ground which i would have thought is the controlled output of the relay to send 12V to the pump at the connector that i found no voltage.

guess i'm more confused on what's happening here by the caption and haven't hunted down the 944 schematic to how this caption would make sense.

i know i know there's plenty of warnings to abandon the DME relay altogether on G5 but i stuck with using the porsche fan switch since honestly my car was barely used in the first 60000 km on the chassis in BC in very temperate coastal climate with no salt/sand/snow until i rescued it from sitting for so long and then ultimately blew the engine up in 4 years (2009).
chassis and rest of car only has 100,000 km now and everything has always worked and still does so i really don't have enough abuse/use to abandon the DME relay i don't think. could most likely be one of the youngest 944's chassis wise to be on the road....

would appreciate the confirmation on go ahead and hook it up iike that for using the DME relay on G5 but better yet how this even works to be grounding what i thought was the output contact on the relay.

actually while thinking out loud, maybe that green with black on 87B is the return pin that needs to be grounded to complete the circuit and the accessory switched wire off of terminal 86 is already going hot to the connector at the fuel pump?

i'm guessing that pin 9 from ecu on 87 is to pull in the coil of the relay to energize and pull in the contacts...

thoughts/guidance?

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DME relay gets abandoned no matter what. It required the Porsche ecu to activate it. Pin 3 in the 14 pin connector goes to the pink wire on your LS harness. Sounds like you have already done that. Assuming you wired the fuel pump wire from the LS harness, then it should power up the fuel pump for 3 seconds only when you first turn on the key. If your pump is still wired to the dme relay, then it will not run at all.

Your LS harness harness should have a fuel pump relay in the fuse/relay block. They usually come with two pins for that relay to add fuel pump wiring to. One pin will come from a fuse in the fuse block and the other will go to the pump. I don't know why the LS harness builders don't add the needed wires for the fuel pump. Battery power will go to pin 30 on the relay and pin 87 will go to the pump.

Fans have nothing to do with the dme relay. The fan relay works great as long as you still have the fan switch in your radiator.

You are only using the 14 pin connector for key on power, oil pressure sender, and water temp sender.

Bob, Those are some great points that helped enlighten me a bit.

To give some better background, i bought the LS1 from a wrecked RX7 conversion which came with the ECU already being scabbed in to work with the RX7 the engine came from. So although the harness seems to have everything, i don't have anything with regards to a fuse block; all i have is the green wire from pin 9 on C2 for fuel pump that needs to be extended and most likely go to a generic relay (since i can't just re-use the DME relay and repurpose its connections?) that i need to find a home for that i can then wire this with accessory and battery connections.

I still don't know how i pick up wires locally in engine bay to heat up the wires that eventually get to the two prong connector back at the fuel tank for the fuel pump; or are these simply run new and abandon where those wires originally ran?

on another side note, i merely have the pin 20 and 57 orange wires combined and in-line fused at 10A. that's it. no additional relays or fuseblock at all with the harness it came with, so probably need to add?
thought i saw another post in advanced search that talked of using a relay that's a spare in the porsche fuse block....

TIA for further pointers and advice.

I ditched the dme relay and added a relay for the fuel pump. The relay I added for the fuel pump, ties back into the 14 pin connector that the fuel pump uses. I can't remember the pin number... (pin 4???) It's been awhile.

If you connect the old coil wires together it will energize a wire in the 14 pin connector to use for a 12v switched relay. Again, I can't remember the pin number.

Gutterboy wrote:Bob, Those are some great points that helped enlighten me a bit.

To give some better background, i bought the LS1 from a wrecked RX7 conversion which came with the ECU already being scabbed in to work with the RX7 the engine came from. So although the harness seems to have everything, i don't have anything with regards to a fuse block; all i have is the green wire from pin 9 on C2 for fuel pump that needs to be extended and most likely go to a generic relay (since i can't just re-use the DME relay and repurpose its connections?) that i need to find a home for that i can then wire this with accessory and battery connections.

I still don't know how i pick up wires locally in engine bay to heat up the wires that eventually get to the two prong connector back at the fuel tank for the fuel pump; or are these simply run new and abandon where those wires originally ran?

on another side note, i merely have the pin 20 and 57 orange wires combined and in-line fused at 10A. that's it. no additional relays or fuseblock at all with the harness it came with, so probably need to add?
thought i saw another post in advanced search that talked of using a relay that's a spare in the porsche fuse block....

TIA for further pointers and advice.

Do yourself a huge favor and buy this. Will save you a lot of headaches.
Otherwise, it's going to be very hard to make your setup work.

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so you have a very valid point on that dream of a harness brand new for that price, i guess i should have just asked but when i did my own searching all my purchasing options started at $600 whether it be painless or some other brands.

thus i decided to dig deep and being more confident at it since its my lane as an electrical engineer i figured it can't be that bad. got even easier when one of my other electrical car buddies passed me a summit racing guide to the ls swap stand alone harness.

i stripped the harness to bare wires and checked all connectors to documentation and labelled all connectors to isolate what was left. All I had remaining were a jumble of pink accessory wires that I now know were used to heat up the old RX7 conversion's distribution block from which this engine and harness and ecu came from.

only last thing i didn't know what to do with was the fuel pump cause none of the wiki said where that goes but now re-reading the summit harness swap doc that was meant to go to the relay block with the harness that i never had.

spence gave me the tip to go track down what's what on the 14 pin connector through the schematic and pin 4 indeed is the same black/green wire that goes back to the fuel pump by the transaxle. Confusion continued to evaporate when i realized from the schematic that the 2nd pin on the connector is a brown wire which goes to a ground point in the floor of the hatch to complete the circuit from the fuel pump being grounded.

Now i just need a new relay socket with relay, an in line fuse, make some connections with the dark green with white wire on pin 9 as the trigger wire to pull in the coil of the relay and then run the output contact wire from the relay to pick up pin 4 to complete the circuit.

Should be easy now.

honestly if i knew that link existed with a new harness at that price i would have just gotten but since i thought i was facing 4x that i poured quite a bit of labour into reforming the harness, laying it out making sure everything still reached and was in the right place, then ripped it out and did final harness tape wrap on all of it. Can't bring myself to bail on it when i really just need to add one relay circuit cause my fans all work on the porsche control system with the porsche radiator fan switch (new).

My bad for just throwing out random confusing questions instead of taking the time and being patient with trying to understand german schematics that are chopped in a non ideal manner in the pdf of the shop manuals i have.

snippets below for reference.

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