So you’re nearing the end of your epic LS1 build, only to find out that when you insert your ignition key and turn it, your LS1 isn’t starting up or running right. With so many new manufacturers bringing so many new products to the table for LS1 swappers, it’s a small wonder than a true turnkey solution is still available.
No matter what the budget of your LS1 swap or build, or even if you are building or swapping a different GM engine, you have to know how to troubleshoot your LS1 swap.
How To Troubleshoot Your LS1 Swap – No Fuel condition
When you are swapping a LS1 into your donor car, you’ll need the right fuel upgrades to ensure your chassis can deliver the fuel your LS1 needs. Whether you’ve installed a Walbro or another brand fuel pump, you need to check the following :
- Fuel pump primes when key is set to “ON” position
- Fuel pump receives power and ground
- There’s 56 psi of fuel pressure at your rail.
If the following things have been checked on your LS1 swap, but it’s still not starting you’ll need to check the following.
Fuel Pressure – The stock pressure at the LS1 fuel rail is 56 psi worth of fuel. You can achieve this a number of ways.
- You’ve got an aftermarket fuel pressure regulator and fuel system. Click here to learn how to install LS1 injectors and rail.
- You’ve got stock LS1 pump and stock rail – You will need a LS1 fuel rail adapter (shown below) to tap into a fuel pressure gauge.
If you have an aftermarket fuel pump with the stock fuel rail and returnless setup, chances are your fuel pressure is sky high. You can cheat this by installing a Bosch fuel filter, part number is 0756161.
This aftermarket fuel pressure regulator is used in a Chevy Express with the 5.3 liter engine, and automatically sets your fuel pressure to 56 psi.
You can also adapt a Corvette pressure regulator, GM part number 10299146 or 19239926.
How To Troubleshoot Your LS1 Swap – No Injectors
If you have sufficient fuel pressure at your fuel rail, but one or more of your fuel injectors are not firing correctly, you’ve got a big problem. To troubleshoot the fuel injector system in your LS1 swap, you should always check your MIL status first for any stored check engine lights.
If just one of your fuel injectors are not firing :
You can test your injector and the harness using a fuel injector noid light. The part number we’re going to be using for our 5.7 liter LS1 swap, is BOSCH 510597 or 510587.
Install this noid light and then attempt to crank over your LS1 swap to see if there’s a reaction. If your noid light does not respond, check your engine grounds. If the noid light does respond but your injector is still not firing and causing a misfire condition, you must replace the fuel injector itself.
If none of your fuel injectors are firing :
Already check your ECU and it’s clear of any OBDII trouble codes? Then the next thing to check is the real time data in your ECU from the engine. Look for engine inputs that are stuck at 100% or values that your ECU should not be seeing.
For example if your TPS wiring has an issue, or is wired incorrectly you’ll see 100% value for the throttle or 0%, depending on what wire is mispinned. If there’s a vital engine input that’s miswired, or there’s a problem with the wiring no part of your LS1 EFI system will work correctly. Check your ECU values first.
How To Troubleshoot Your LS1 Swap – No Spark condition
When your LS1 swap does not turn over or start, you’ve got to start with the basics. Testing your LS1 swap for spark is easy, simply unplug one of your ignition coils and plug in a spare spark plug into the spark plug wire. With someone inside the car and cranking the engine over, you should see spark at the test spark plug.
If you don’t have a spare spark plug, you can use an inline spark tester to determine which coil and cylinder is the problem.
Here’s a shortlist of things to check on your ECU when you are trying to learn how to troubleshoot your LS1 swap.
ECU – Check your ECU terminal for power at these following pins.
LS1 Blue Connector
- PIN 2 LT GRN 1867 12 Volt Reference- CKP Pin “C”
- PIN 3 PNK/BLK 1746 Fuel Injector 3 Control
- PIN 8 GRA 596 5 Volt Reference TPS Pin “A”
- PIN 48 GRA 416 5 Volt Reference (MAP Sensor) Pin “C”
- PIN 57 ORN 340 Battery Positive Voltage
LS1 Red Connector
- PIN 15 RED 225 Generator Turn ON Signal
- PIN 39 RED 631 12 Volt Reference CMP Pin “C”
- PIN 66 PPL/WHT 2128 IC 8 Control
- PIN 67 RED/WHT 2122 IC 2 Control
- PIN 68 DK GRN 2125 IC 5 Control
- PIN 69 LT BLU 2123 IC 3 Control
ECU – Check your ECU terminal for Ground or low reference at these following pins.
LS1 Blue Connector
- PIN 1 BLK 451 PCM Ground
- PIN 21 YEL/BLK 1868 Low Reference CKP Pin “B”
- PIN 40 BLK 451 Ground
- PIN 53 BLK 407 Low Reference (Transmission Temperature Sensor) Pin “M”
- PIN 54 BLK 407 Low Reference (MAP Sensor Ground) Pin “A”
- PIN 60 BLK 452 Low Reference TPS Pin “B”
- PIN 61 PNK/BLK 632 Low Reference (Camshaft Position Sensor) Pin “B”
- PIN 80 BLK 407 Low Reference ECT Pin “A”
LS1 Red Connector
- PIN 1 BLK 451 Ground
- PIN 57 PPL 719 Low Reference IAT Pin “A”
- PIN 60 BRN 2129 Low Reference Ignition Coils bank 1 (1-3-5-7)
- PIN 61 BRN/WHT 2130 Low Reference Ignition Coils Bank 2 (2-4-6-8)62 — — Not Used
That does it for our How To Troubleshoot your LS1 swap, if you have any questions or a problem with your LS1 project, leave a comment for us below!