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Hey guys I’ve been working on this 5.3 swap for way too long. I converted a truck harness myself and am using a fuse box from BP automotive. I’ve triple checked the wiring and I’ve already turned VATs off via HP tuners.
Cliff notes:
’88 Corvette
-1999 5.3 that I’ve already gone through (new timing chain, PAC valve springs,)
-Blue/Red DBC harness.PCM shows VIN of an ‘04 truck engine in HPTuners.
-4 speed manual trans (no VSS hooked up, no tach currently)
-truck MAF
-new CKP sensor.
-Not getting any DTCs.
Fuel pressure is good but I’m not getting spark-checked with a spark tester. I find it unlikely that all 8 coils would be bad so I’m leaning towards a wiring issue. I’m assuming the fusebox is good to go since I am getting fuel. Small chance the ignition relay could be bad? Is a tach signal or VSS signal needed just to get the engine started?
Any ideas what to check next?
Does anything go into the threaded left hole? Just installed LS6 valley cover.
Also installed new AC Delco cam and crank sensors.
Last edited by Vette-byrd; 03-16-2020 at 07:18 PM.
Double check your grounds. There should be 3 of them on a truck harness, o e on the rear of each head and one down low behind the power steering pump. That one will usually cause a no spark issue if missed.
Double check your grounds. There should be 3 of them on a truck harness, o e on the rear of each head and one down low behind the power steering pump. That one will usually cause a no spark issue if missed.
I’ve recently redone them. Each coil bank is grounded to the rear of each head. Pcm grounds are at the pass side rear head. Batt is grounded to the engine block. Also have a strap from the pass side block to frame.
take all the pink coil wires and run straight to battery with a fuse to confirm. That should be easy. I don't recall but I don't think all the pinks are always 12V. Sometimes you 'may' have a 5v source you used.
take all the pink coil wires and run straight to battery with a fuse to confirm. That should be easy. I don't recall but I don't think all the pinks are always 12V. Sometimes you 'may' have a 5v source you used.
Temp wire only the pink coil wires to the battery? I’ll give this a try!
I’m having the same problem with my L33 swap except everything tests out except no spark. 2 grounds wires on back of engine were loose and fixed that. Then Ls1Nova71 mentioned the 3rd ground behind P/S pump and Bingo it was loose. I will test start today but think that is the problem. I’ve been searching the forums for days. Not the first time Ls1Nova71 info has helped me out. So check that 3rd ground
when I rewired my car, I moved all the grounds from the back of the head to the front. Mainly because in an FBODY i never want to chase that bolt again while the engine is in the car and so I moved it to the front. Also - for trouble shooting and temporary. I would wire all the Pinks, there are not many and all the grounds to one place and it will fire if you have your fuel pump. Otherwise, it is something else like vats or damaged ecu, otherwise it will fire.
when I rewired my car, I moved all the grounds from the back of the head to the front. Mainly because in an FBODY i never want to chase that bolt again while the engine is in the car and so I moved it to the front. Also - for trouble shooting and temporary. I would wire all the Pinks, there are not many and all the grounds to one place and it will fire if you have your fuel pump. Otherwise, it is something else like vats or damaged ecu, otherwise it will fire.
Appreciate all the input! Fortunately I have a spare PCM that I’ll have to buy credits for and try.
Small update:
I wired the injectors and coils to battery power. Still not getting spark though.
Fuel pressure is good.
Every injector is getting signal-confirmed with noid light.
Messing with the multi meter I got a coil to spark just probing the plug.
I also tried a different PCM ( same 4856 serv PCM) with no change. For some reason HP Tuners allowed me to write this PCM without paying for credits).
No codes.
IAT is showing maxed out in HP Tuners though-using truck maf with the integrated IAT.
Last edited by Vette-byrd; 03-26-2020 at 02:49 PM.
No luck.
2nd new CKP sensor.
Redid the grounds:
-negative cable to drivers side engine block.
-each coil to each head
-frame to head
-p/s block to frame
-PCM grounds to head.
Wired coils to constant battery wire with fuse.
Getting power in both key on engine off AND while cranking.
-Tried 2 diff batteries + a jumpbox.
-Tried two sets of coils.
Still no spark.
Only codes are 2 for the MAP sensor.
Last edited by Vette-byrd; 04-05-2020 at 05:11 PM.
Maybe I missed it while reading but did you try opening your TB blade a little. Some TB have small port holes that clog.
Could that help with a DBC Tb?
I’ll give it a try. I’m running out of things to check. Going to go over the pcm grounds tomorrow but not sure what else could be the issue.
PCM red pins 60 and 61 are bank 1 and 2 low reference, respectively. Verify continuity between the PCM and the common electrical plug for the 4 coils at each bank.
What codes are you showing? Your high IAT reading suggests that the circuit is shorted to ground.
I believe it was a p1107 and p107? I’ll double check this evening.
originally I had the IAT separate in my intake but I’ve switched to the truck maf with integrated IAT.
"Is a tach signal or VSS signal needed just to get the engine started?"
No tach signal, no start.
well damn. Lol
I guess I’ll have to do some research on an aftermarket setup. Any recommendations? I hear Dakota Digital has something. Or is that the VSS setups?
PCM red pins 60 and 61 are bank 1 and 2 low reference, respectively. Verify continuity between the PCM and the common electrical plug for the 4 coils at each bank.
What codes are you showing? Your high IAT reading suggests that the circuit is shorted to ground.
Ive got continuity at both pins.
Also have continuity at pins 1 & 40 on both connectors.
Each is going from the coil plug to pin 60 and 62 on the Red PCM. Is this correct? From what I’ve read the low ref is the same as a ground?
My IAT is now good.
Swapped Map sensors-now good and no codes.
Still no spark and no rpm while cranking. What are the chances of my sbc reluctor being damaged?
Last edited by Vette-byrd; 04-12-2020 at 03:55 PM.
03-09-2020, 02:42 AM
Troubleshooting Swap No-start 
