2008 LS 1 swap fuel question
05-21-2017, 07:33 PM
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2008 LS 1 swap fuel question Hi guys,
My first time posting here. I am currently working on a 73' f100 that has a 6.0 out of a 2008 chevy express 3500. Right now it has an inline fuel pump, but it isn't hooked into the ecu so there's no communication there so it's runny real wacky. I've been told of a few ways to fix this. 1. Go carbureted. 2. put a higher psi fuel pump in and plumb in a return line (right now it's a returnless system). 3. Use a stock in tank fuel pump and wire it back into the system. Problem is I can't find the 2 pigtails that clip into the fuel pump. I've read a lot about the different ways to do this, including in line pumps, but I don't get how guys are getting those to communicate with the computer. Any info. would be great. Thanks.
My first time posting here. I am currently working on a 73' f100 that has a 6.0 out of a 2008 chevy express 3500. Right now it has an inline fuel pump, but it isn't hooked into the ecu so there's no communication there so it's runny real wacky. I've been told of a few ways to fix this. 1. Go carbureted. 2. put a higher psi fuel pump in and plumb in a return line (right now it's a returnless system). 3. Use a stock in tank fuel pump and wire it back into the system. Problem is I can't find the 2 pigtails that clip into the fuel pump. I've read a lot about the different ways to do this, including in line pumps, but I don't get how guys are getting those to communicate with the computer. Any info. would be great. Thanks.
05-22-2017, 12:45 PM
#2
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The PCM has a wire in it that supplies 12v to turn on the fuel pump relay. Power for the pump comes from the battery passes through a relay, and goes to the pump. The PCM has a single wire that goes to the relay that turns it on/off.
Inline Walbro 255 with Corvette inline filter/regulator can be done fairly cheap. I usually have $200 or so in a pump/filter/regulator/AN fittings/Push lock hose/relay.
Inline Walbro 255 with Corvette inline filter/regulator can be done fairly cheap. I usually have $200 or so in a pump/filter/regulator/AN fittings/Push lock hose/relay.
05-25-2017, 05:37 AM
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So the mechanic I last took this to thought the in line fuel pump I was using wasn't sufficient. He said that at idle the pressure was good, but when you hit the throttle, pressure would drop. So I attached a chart of the fuel pump specs that I'm running now, and then looked up the specs on stock in tank fuel pumps...the ratings vary quite a bit. From what I see, this inline fuel pump should be sufficient, but I wanted some other people's opinions. See attached.
Im running the first pump listed on the attached spreadsheet. The delphi in line pump.
Im running the first pump listed on the attached spreadsheet. The delphi in line pump.
Last edited by hath; 05-25-2017 at 08:16 AM. Reason: Clarification
06-03-2017, 02:14 PM
#5
The purpose of the ECU connection is to turn the pump off when it's not needed - like when the key is on but the engine is not turning over. That's a very nice feature, but it's NOT REQUIRED. You could hot wire the fuel pump straight off the battery, and the engine would run just fine.
If you're pressure is dropping when the rpm's go up, then one of two things are happening. The fuel pump is not big enough to supply enough fuel, and you need a bigger pump.
Or, it's losing it's electrical amperage. Get the rpm's up to about 2,500'ish, and then turn everything on - headlights, 4 way flashers, stereo, etc. Put a big electrical load on the system. Also, shake the power and ground wires to the pump, looking for loose connections. If you lose pressure, you know it's an electrical problem. That's not very common, but I suppose it could happen.
With a retrofit, you might also take a look at the rest of the fuel system. What pressure regulator are you using? Do you have a 1/4" pick in the fuel tank? Is a feed line pinched? Old fuel lines clogged? Stuff like that.
If you're pressure is dropping when the rpm's go up, then one of two things are happening. The fuel pump is not big enough to supply enough fuel, and you need a bigger pump.
Or, it's losing it's electrical amperage. Get the rpm's up to about 2,500'ish, and then turn everything on - headlights, 4 way flashers, stereo, etc. Put a big electrical load on the system. Also, shake the power and ground wires to the pump, looking for loose connections. If you lose pressure, you know it's an electrical problem. That's not very common, but I suppose it could happen.
With a retrofit, you might also take a look at the rest of the fuel system. What pressure regulator are you using? Do you have a 1/4" pick in the fuel tank? Is a feed line pinched? Old fuel lines clogged? Stuff like that.