5.3 rebuild no spark
Thread Starter
Staging Lane
Joined: Nov 2020
Posts: 55
Likes: 5
5.3 rebuild no spark Hello,
I've recently finished fully rebuilding a 2003 5.3 and upon attempting to start it on the stand, it will not start. I can hear the injectors clicking and when I unplug the crank sensor they stop clicking when turning the engine. The coils are getting 12v and ground and I've checked every ground I could think of. Used a different harness that I've run a 5.3 in a stand with before to the same issue. Swapped crank sensor and cam sensor multiple times to no avail. Any advice?
I've recently finished fully rebuilding a 2003 5.3 and upon attempting to start it on the stand, it will not start. I can hear the injectors clicking and when I unplug the crank sensor they stop clicking when turning the engine. The coils are getting 12v and ground and I've checked every ground I could think of. Used a different harness that I've run a 5.3 in a stand with before to the same issue. Swapped crank sensor and cam sensor multiple times to no avail. Any advice?
TECH Fanatic
Joined: Jan 2018
Posts: 1,250
Likes: 239
From: Dade City, Fl.
are you using the factory fuse block? Is the harness factory or did you rework it? Double check everything as G Atsma suggested. There are many videos online to show how LS engines are ran on the stand.
Thread Starter
Staging Lane
Joined: Nov 2020
Posts: 55
Likes: 5
Reworked harness that I did myself, ran engines on the stand with the harness before no problem. Tried another harness aswell like I said and it's the exact same issue with both.
Thread Starter
Staging Lane
Joined: Nov 2020
Posts: 55
Likes: 5
Went back over the harness again and checked every 12v and ground I could think of, everything seems good and still no spark. I don't think this would have anything to do with it but I have an aftermarket cam installed from summit racing, could that be causing the no spark?
TECH Fanatic
Joined: Jan 2018
Posts: 1,250
Likes: 239
From: Dade City, Fl.
TECH Fanatic
Joined: Jan 2018
Posts: 1,250
Likes: 239
From: Dade City, Fl.
The coils are "hot" with key in run and crank position. They receive a ground from the pcm to charge the primary winding inside the coil. The pcm interrupts the ground to the primary winding of the coil causing the voltage induced in the secondary winding of the coil to be released by the spart plug wire. Much better explanation by Denso
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Staging Lane
Joined: Nov 2020
Posts: 55
Likes: 5
Yes, to crank the engine I just directly jump the starter and I can still hear the injectors clicking while cranking. I don't know if this is of any importance but when hooking the engine up to hptuners vcm scanner and cranking the engine it does not register any rpm. I don't know if it's just not spinning fast enough or if there's an issue with the ckp. It doesn't make any sense because the injectors fire based on the crank position.
Thread Starter
Staging Lane
Joined: Nov 2020
Posts: 55
Likes: 5
Thread Starter
Staging Lane
Joined: Nov 2020
Posts: 55
Likes: 5
Thread Starter
Staging Lane
Joined: Nov 2020
Posts: 55
Likes: 5
Timing gear was set so that the dot on the timing gear and cam gear were facing eachother, haven't used a spark checker but I can jump the coils at the coil bulkhead and get visible spark out of all the plugs, and there's no dtcs at all.
Thread Starter
Staging Lane
Joined: Nov 2020
Posts: 55
Likes: 5
Update: I had been reading some threads and someone suggested jumping pins a and c on the ckp pigtail, so I did that a couple times and heard the injectors clicking then one of the plugs fired, causing one of the cylinders to fire. I'm lost as to what this could be, I've tried two different crank sensors already... Could it be a bad reluctor wheel?
Thread Starter
Staging Lane
Joined: Nov 2020
Posts: 55
Likes: 5
According to this article it is possible not to have any spark or spark at the wrong time. Did you remove the reluctor wheel? Read