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I am buttoning up all the standalone wiring and harness connections on my swap. Ran into a bit of a problem. First off I couldn't get the Fuel Pump to prime, I checked the relay connections that I had setup and realized I had a couple of wires backwards. Before I had realized what I had done with the Fuel Pulp Relay I had gone ahead and ran a 12v battery source directly to the fuel pump and it turned on and it was just priming the whole time, I successfully had the motor fire up and had to turn it off by disconnecting the battery connection to the fuel pump, would have ran until the fuel ran out. So now that I got all the wiring connections wired up, now when I turn the key I can hear the fuel pump prime for 2 seconds and the DBW/throttle get power as the throttle body fin moves a bit with key in on position. When I go to start the motor it fires up, but for only for like 2-3 seconds and then the motor turns off. I cant even hear the fuel pump on after the priming stage to when I turn key to start it.
I had gone through the ground pins 1 & 40 on the red and blue harness, the ground connections were good.
I went through pins 19,20,57 on the blue harness and all had power. I checked all the injectors and they also had a 12v signal. I did a continuity test on the #9 fuel pump relay from the blue harness as well and it was fine.
If anyone has had this issue, or have any suggestions please let me know.
Oh forget to mention that the PCM is tuned and the VATs have been removed.....if I wire the fuel pump directly to the 12v source and it runs for more than 10 - 20 seconds will this confirm the Vats have indeed been removed?
Not sure about the vats but I I'm in a similar situation.i haven't had time to troubleshoot mine yet but recently when I got it to the first start phase the fuel would run for a few seconds then stop.It ended up having a burnt pin in the deutch(spelling?) connector I had near the pump. I'm going to swap out the deutch connector for a weatherpak connector.
When the key is turned on, the fuel pump will prime for 2seconds. If the PCM see the ignition pulses within 2 seconds of cranking, the PCM shuts the pump relay off. I'd make sure the relay is clicking and you have power at the fuel pump. Make sure you have good ignition signal and spark.
So I went through all the wiring, cleaned up all the grounds, key switched +, Battery power. The car fired up and purred like an LS should. Had it running for about 10 mins and the check engine light came on,no leaks or any other issues. So plugged in the OBD reader and it was code p0118....Temp Sensor. Than I remembered that I didnt have the Temp sensor connected to the ECM, but instead had the Dakota Dash temp sensor connected to the DD gauge. So I got the OE sensor wired up and connected to the stock pigtail to ECM. Went into the OBD reader and erased the fault code. After this I went to start the motor up and again the car won't stay running more than 2 to 3 seconds.....no fault codes or CEL of any type.
I have a Russell/Edelbrock fuel pressure gauge on order to make sure I am getting 58psi to the rails. I have a TANKS efi fuel tank with electric fuel pump and all plumbed with a return line from the corvette style Fuel Pressure Regulator. I have the FP regulator mounted in the engine bay, is that to far from the tank to be getting 58psi? Should it be closer to the tank?
I just dont know what it could be, the fact that it started before i did the temp sensors, and now it doesnt want to run. I even fully charged the battery thinking it could of been a week battery after trying to crank it over.
Any help would be great,
Last edited by BabyDaddy; Mar 21, 2020 at 01:01 AM.
Yesterday morning and today,the first start it started right up and didnt stall or cut out in any way unless I turned it off. But what I realize is that once i turn it off, it wont start up again no matter how many times a try. It has a quick turnover like it's going to start but just doesnt turn over completely(fire up and stay fired up).
I checked the fuel lines to make sure they weren't plumbed backwards on the FPR and they were correct. I am still waiting g for my Fuel gauge to shop up so I can see if I the motor is getting the required 58-60psi it needs to run.
Any other suggestions or ideas would be greatly appreciated.
Fuel pressure gauge arrived today. Connected to the fuel rail. When I turn the key (not started)....the pressure goes to 65....than drops to 41....and than slowly creeps down to about 37 after about 10 mins of sitting.
I cranked it over and it got up to about 67 and died....tried a couple of times...same result disappointing result.
Been reading the forums for days. I have almost the same issue.
LS1 out of a 2000 camaro 5.7L
been running for months no issue.
1980 Blazer
Intermittent no prime but crank issue
tested/ replaced relay.
checked all fuses.
jumped relay fuel pump runs fine.
started up and kept running until jumper pulled.
Check grounds by touching a know good ground and getting continuity from the point the PCM is grounded.
Re-installed relay. Worked just fine for two days.
Now same issue.
What would cause the PCM to not ground/activate the relay? How can I check it the PCM is working properly? Thanks
Been checking everything I know of.
PCM seems to be working since it stayed running when jumped. Power from battery to relay is good. Relay to fuel pump is good. What can I check on the other two wires from PCM to relay. They both go into the harness. I haven’t pulled it apart yet one should get a continuity with the ground point for the PCM. What about the other?
also thought about checking wether my PCM is getting power all the time. Any easy way to do that. I’m waiting on my OBD2 reader to arrive today to help out.
After checking pins on the PCM. I am not receiving any voltage on pin 19 pink wire blue connector on PCM hdw no. 16220610. Should be an ignition wire.
anybody in the c10 LS swapped business know where this would come from on the truck side.
All grounds look good and all battery voltage into the PCM looks good.
I built a bunch of "noids" that I piggy back on the wiring when I have a weird electrical issue, just a LED with integrated resistor to run on 12V (auto parts store indicator light) and a pair of test lead ends on about 3' of wire..
I connect each from the wire I care about to ground. Works great for sorting out oddball problems.. (fan relays/ fuel pumps, any circuit thats On-off non digital connection. )
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LS1 Swap Fuel Pump issue/PCM 
