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Old 05-16-2019, 08:31 AM   #1
ScotchWhiskey
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Default More V8:LS Swap - Fuel and Wiring

Hey guys, so I’ve got a GenIII 5.3 sitting in my 92 740 turbo wagon. Next on the list is plumbing the coolant system, modding a wiring harness, getting fuel to it, and a custom driveshaft and exhaust.

So what is everyone running to get fuel to the LS transplants? I see a lot of swaps use the corvette FPR as sort of a returnless system. Is there any chance to set it up inline under the car and use the Volvo pump? Or will I need to use an aftermarket unit like a Walbro?

With the wiring, my plan is to use the LT1swap wiring tutorial to create a standalone type harness to run the engine. What do I need to integrate out of the 740 harness to keep any functionalities? I know the coolant sensor will need to be there to run the gauge on the dash, but is there anything else? Will I need to keep a Volvo ECU and EZK in the vehicle for any reason? I thought I saw a thread where a guy was unpinning stuff at the ECU harness and removing it from the engine bay.

Any help or direction would be great, I’ve read and read on this stuff for years but sometimes it’s best to get direct information from someone with firsthand knowledge and experience.
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Old 05-16-2019, 03:38 PM   #2
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get an adapter fitting for the fuel filter outlet and run a new line to the fuel rail. if you're using a return style system, you'll probably need to either run aftermarket rails and a regulator (and then just use the OE return setup, this is what I'm doing)

for the temp sender for the gauge, you'll probably just want to put that in the upper radiator hose, I haven't found a suitable (that I know of at least) interchange sensor that threads into the head. I haven't really spent much time looking for one though either, car has not overheated after putting a bigger radiator in it. You will not need to keep the lh and ezk boxes.
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Old 05-16-2019, 03:41 PM   #3
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I'd have to think a stock Volvo pump would really be on its limits trying to feed an LS? Although I guess no boost makes it a lot more likely to work.
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Old 05-16-2019, 05:14 PM   #4
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I used the corvette fuel filter/regulator and a walbro 255 in the tank. 58 psi and returnless system. I placed it in the housing for the main 240 pump. Short supply and return hoses and one fuel feed to the rail.
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Old 05-16-2019, 08:47 PM   #5
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I like both ideas on the fuel systems, probably need to see which type of return system I have and go from there. I have several intakes so it seems like the vette filter/regulator and Walbro would be the optimal setup.

Am I correct to assume that I can just pull the majority of the wiring harness for the engine and then unpin those from the ecu connector?? Everything but the coolant temp for gauge??
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Old 05-16-2019, 10:21 PM   #6
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Quote:
Originally Posted by MikeSr. View Post
I used the corvette fuel filter/regulator and a walbro 255 in the tank. 58 psi and returnless system. I placed it in the housing for the main 240 pump. Short supply and return hoses and one fuel feed to the rail.
Similar setup. I mounted my regulator on the firewall above the booster.
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Old 05-17-2019, 09:23 AM   #7
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Quote:
Originally Posted by JohnMc View Post
I'd have to think a stock Volvo pump would really be on its limits trying to feed an LS? Although I guess no boost makes it a lot more likely to work.
nah, I was fine til the in-tank pump started blowing the fuse and then it would lean out. Of course, I didn't discover this until I'd put a 450 in the tank lol
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Old 05-17-2019, 10:19 AM   #8
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What kind of line are you running from a fitting in the stock filter to the LS fuel rail??
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Old 05-17-2019, 10:26 AM   #9
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I have ebay rails on mine, but it's a -6an
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Old 05-17-2019, 11:14 AM   #10
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Are you sure your engine has a returnless fuel system? Some GenIII 5.3s have a conventional return style system.
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Old 05-17-2019, 12:29 PM   #11
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OP, is this for a turbo 5.3 or just a simple LS swap? The C5 filter/regulator is super easy if you're leaving the 5.3 stock. If you're gonna boost it, you might be best off starting with a return style system. Fueling issues suck to deal with when everything is already assembled in the car.
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Old 05-17-2019, 09:15 PM   #12
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Most of the motors I've seen have back pressure regulators - so there's a return line from the reg. The issue is simply where is the regulator located. If it's on the fuel rail - then you have a return line running all the way back to the tank. If you mount a Corvette style filter/reg near the tank, the return line is short. And you just have a 58 psig single line running to the front. Some folks refer to that as a 'returnless' system - but it's really just not returning from the fuel rail. If you're using an ECU from a set up that had a regulator on the rail that takes a vacuum connection -- the ecu is programmed expecting that fuel pressure will vary with the vacuum signal. And the Corvette filter/reg won't do that. You can alter things in a tune - but if you're trying to keep it simple and that's the style regulator/ecu you have -- then you'll run a return line to the back. Mine's in a 240 - like Mike Sr. above, mounted the Corvette filter/regulator on the platform for the OEM inline pump. Put a Deatschwerks DW300 in the tank. -6AN lines.

I found it easier to just run a few new wires for gauges, idiot lights, etc. than to try and pick them out of the Volvo engine harness. Besides, a lot of the original harnesses under the hood have seen better days anyhow.
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Old 05-17-2019, 09:49 PM   #13
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Man I wish we had an LS swap subforum to catch all the info in one place...
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Old 05-18-2019, 08:38 AM   #14
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Going to be a pretty simple 5.3 with cam and springs with a 4l60e. Going round and round with intake manifolds as I’m stuck with truck manifolds and no good clearance. Either space the subframe or find a LS1 intake which is near impossible where I’m at. I have return-less and return style fuel rail set ups right now, so either option should work for me. I will most likely attempt the vette filter/regulator after the info in this thread. I’m really tempted to swap the redblock out of my 240 and start over with a chassis that will fit the truck intake!!
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