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lt1 to ls1 swap no start

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Old Mar 10, 2014 | 11:06 PM
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Default lt1 to ls1 swap no start

Today i tried to start the car on my lt1 to lq4 swap.

I get no fuel pressure and i also get no power to the starter. i dont here it engage and the fuel pump i dont here it prime.

I dont have VATS disabled. Can that be the main issue?

Does that stop the starter from getting power? or engaging.

I dont think i have the fuel pump wired correctly.
The harness i bought has its own fuse box for the fuel pump relay and the ignition.

for the ignition i have the red wire for key on cracking to connector C100 cavity G(Power feed from igntion Fuse #11).

as for the fuel pump relay i have the #87 wired to connector C220 to the Cavity J (Fuel pump relay control).

i dont have no wire to the #30 on the relay(+12v).

I am really confused at this point why im not getting any power to the fuel pump and the starter.

This is my 1st car project. hopefully this made some sense.

Thanks for the help fellas
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Old Mar 11, 2014 | 01:16 AM
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Hard to say honestly without knowing how the Harness is wired. IMO there is absolutely no need for any kind of external Fuse Box, Relays, or anything on a LT1 -> LS1 Swap Harness. Well I take that back, not my opinion, from my experience.

From what we have discussed it sounds like the company you paid to wire it took your money and left you hanging... I say that because there are several of us that have built direct plug in Harnesses for this swap that start the car without issues.

I would put a foot in their *** and ask them why they couldn't build a proper harness.
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Old Mar 11, 2014 | 01:21 AM
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I did a swap on a jeep and it had no power to the starter and it was a bad ground, do all of your dash lights, headlights, brake lights work?
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Old Mar 11, 2014 | 01:23 AM
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Originally Posted by davidc212k
Today i tried to start the car on my lt1 to lq4 swap.

I get no fuel pressure and i also get no power to the starter. i dont here it engage and the fuel pump i dont here it prime.

I dont have VATS disabled. Can that be the main issue?

Does that stop the starter from getting power? or engaging.

I dont think i have the fuel pump wired correctly.
The harness i bought has its own fuse box for the fuel pump relay and the ignition.

for the ignition i have the red wire for key on cracking to connector C100 cavity G(Power feed from igntion Fuse #11).

as for the fuel pump relay i have the #87 wired to connector C220 to the Cavity J (Fuel pump relay control).

i dont have no wire to the #30 on the relay(+12v).


I am really confused at this point why im not getting any power to the fuel pump and the starter.

This is my 1st car project. hopefully this made some sense.

Thanks for the help fellas
VATS wont stop the Starter.

What I highlighted in bold is what confuses me. What did you wire to Cavity G?

No power to the Fuel Pump is because there is no 12V source in on 30, there needs to be a 12 Constant in on this, 87 out to the Pump, 85 ground, 86 the 12v FP Relay Control wire from RED 9 on the PCM.

But, don't worry about what I just said, my question is why is the factory Relay not used?? It works good from the factory and in every harnesses I have built so I want to know what dip **** put that in the harness with their wisdom in turn leaving you hangin looking for answers here from some of us technical experts.

Send me that damn harness and get your money back from the company that built that crap. They have any questions on how to do it the RIGHT way they can get ahold of me for lessons.

I'm tired of seeing these damn companies doing half-assed ****.
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Old Mar 11, 2014 | 01:23 AM
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Try crossing the solenoid, see if its getting any power that away and if its a communication issue to the starter, i have no suggestions on the fuel pump though.
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Old Mar 11, 2014 | 01:27 AM
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Starter is simple...there are two wires. Heavy 12V from Battery, and the 12ga 12v wire to the Solenoid. Only thing that can be stopping that is the Starter is bad, so get a test light (or multimeter) and see if you have 12v at the purple wire that goes to the starter when you turn the Key to START.

As far as the other stuff I'm baffled because as I mentioned these harnesses are a direct plug in swap. There is no need to wire ANYTHING unless it's a 1993-1994 and you have to put in the OBD2 DLC.
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Old Mar 11, 2014 | 06:16 AM
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I will see what I can do this afternoon. As far as making them give my money back.
dude didn't even want to help out. He basically said did you read the manual we sent you. But in a pissed off manner. At this point I will try my best to figure it put. Thanks all for the recommendations.
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Old Mar 11, 2014 | 06:51 AM
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Maybe, put this morons name up, and save others from making the mistake you did??
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Old Mar 11, 2014 | 07:56 AM
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Default ls1

Originally Posted by LsPrideOrDie
I did a swap on a jeep and it had no power to the starter and it was a bad ground, do all of your dash lights, headlights, brake lights work?
as for the starter. im not sure if its wired correctly.
basically there is two wires that i believe go there plus the battery wire to the starter. the dash lights work. headlights work. i will have to check the brake lights today.
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Old Mar 11, 2014 | 08:01 AM
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Default ls1 swap

Originally Posted by the_merv
VATS wont stop the Starter.

What I highlighted in bold is what confuses me. What did you wire to Cavity G?

No power to the Fuel Pump is because there is no 12V source in on 30, there needs to be a 12 Constant in on this, 87 out to the Pump, 85 ground, 86 the 12v FP Relay Control wire from RED 9 on the PCM.

But, don't worry about what I just said, my question is why is the factory Relay not used?? It works good from the factory and in every harnesses I have built so I want to know what dip **** put that in the harness with their wisdom in turn leaving you hangin looking for answers here from some of us technical experts.

Send me that damn harness and get your money back from the company that built that crap. They have any questions on how to do it the RIGHT way they can get ahold of me for lessons.

I'm tired of seeing these damn companies doing half-assed ****.
To cavity G(C100) i wired the ignition feed when key on cranking wire from the harness. its a red wire. that wire is coming from the ignition relay.

Last edited by davidc212k; Mar 11, 2014 at 08:25 AM.
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Old Mar 11, 2014 | 08:40 AM
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Default ls1

Originally Posted by Old Geezer
Maybe, put this morons name up, and save others from making the mistake you did??
i got the harness from psiconversion.com. i believe i spoke with the main guy from the company.
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Old Mar 11, 2014 | 10:30 AM
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I just remembered that i have an extra walbro fuel pump wire kit.
I believe if i install that. it should take care of the fuel pump issue.

what worries me is the two connectors that i have plugged in the starter and then the red(+) coming from the battery to the starter.
As for the ignition wire that says ignition wire to key on and cranking power. like i stated i have it plugged in the C100 Connector Cavity G Pink wire(Power feed from ignition fuse#11.)
There is no wires for the ignition relay for #86,#30,#87 or #85. So how am i suppose to get ignition ? lol.

I feel like i should just plug in the factory wires to these two relays. lol.

Last edited by davidc212k; Mar 11, 2014 at 10:36 AM.
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Old Mar 11, 2014 | 11:35 AM
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Default ls1

Today i will plug in the purple wire to the starter to the purple wire on the C210 Cavity A. that wire is for the deft deterrent relay to starter solenoid feed.that wire is currently not plugged in. im guessing that ignition switch related.
As for red wire on the psi harness, on the LS1 C105 Cavity B its for the ignition one voltage that gives 1 voltage when the key is on cranking.
On the LT1 C105 its for power feed from fuse #10.

Last edited by davidc212k; Mar 11, 2014 at 01:49 PM.
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Old Mar 11, 2014 | 04:37 PM
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The only question i have are.
on the C100 Cavity G Pink power feed from ignition fuse 11. Is that the ignition key on crank?
There is also the Pink on C105 that power feeds from fuse#10.

I do get power to the gauges. i did notice last night.
i dont get anything on the milage or the tachometer.
I will take a video shot of it all. Soon as i get off work.
I swear i cant concentrate at work, lol. been thinking about this issue all day.
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Old Mar 11, 2014 | 08:06 PM
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Well i just connected the purple wire to the starter C210 connecter for the Theft deterrent relay to starter solenoid feed.
Now i get ignition to the starter.
As for the fuel pump i connected the #30 and the #87 from the fuel relay to the connections on the factory connections.
I get not fuel pressure and priming sound.
now i just need to get the fuel pump running.
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Old Mar 11, 2014 | 08:09 PM
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The large purple wire in the C210 is what SHOULD be going to the starter. There are two wires, heave 12v and this purple to the Starter Solenoid.

This C100 G Wire is a 12v with key on, Fuse #11 in the box is this circuit, that would have originally have powered the Opti on the LT1. This circuit is adapted for another use in this conversion, as are a few others.

Lights and all that are going to work, it's chassis wiring on completely different circuits.

Now I will say this..what you "believe" you should do is probably not going to work. You don't sound like you have a lot of wiring knowledge and before you burn the car down I recommend that you take a step back here and think about how you want to go about fixing this.

I honestly think you have a pile of **** for a wiring harness that needs to be looked at to ensure the quality, but that is just me.

.
Originally Posted by davidc212k
i got the harness from psiconversion.com. i believe i spoke with the main guy from the company.
Sounds like they are a bunch of
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Old Mar 12, 2014 | 12:28 PM
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Yea I dont have any wiring experience. That why this whole process is called a project.
i will try my best to get this car running without causing any fires. lol.
last night i wired the FP relay #30 for 12v and the #86 to the fuel pump. Like stated i got no fuel pressure or prime from the fuel pump.
The harness has a #87 that is going to PCM for the FP relay Control.
The harness also has the #85 for ground built in the harness that is going to ground by the passenger side.

This is a learning experience. So i did a bit more research. i will test the 12v source for voltage.
I was curious, since i dont have a wire connection to the oil pressure sensor wired to gauge cluster. Does that send a signal to the PCM to cause the fuel pump not to power on?
The harness did come with a oil pressure connector for the LS1, but since im using the LT1 body n gauge cluster. that wont work.
I simply have to wire the oil pressure sensor wire to the LT1 gauge connector.
Im just taking a wild guess if that can cause no power to the fuel pump.

Thanks for your grateful help gents.

Last edited by davidc212k; Mar 12, 2014 at 01:10 PM.
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Old Mar 12, 2014 | 01:34 PM
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On your last post you said that #87 goes to the pcm and that is incorrect as # 87 should go to the fuel pump. 85 and 86 should be 12v and ground respectively an 30 should be a 12v constant.Some may argue that 85 and 86 can be reversed and in most cases it will not matter unless the relay has a suppression diode internally to clamp off voltage spikes. Google automotive relay operation to better understand their function.
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Old Mar 12, 2014 | 02:30 PM
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Here is a small part of the fuel pump relay wiring for a 95 Z/28

The DK GRN/WHT wire shown goes to the pcm for relay control.
Attached Thumbnails lt1 to ls1 swap no start-95-fp-relay.jpg  
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Old Mar 12, 2014 | 04:40 PM
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Per chevyowners diagram #30 is a ign/key switched 12 volt supply wire. This is the way the factory did it as to provide fused protection of the fuel pump circuit.If you intend to to supply a constant 12 volt I would suggest a 15 amp fuse in that line also.
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