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ls swap/engine-now with vss wiring question

big dan

big dan

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Ok I will first admit that I dont know a whole lot about these engines but decided to dive in a do a swap on my dd. Used lt1swap.com for wiring harness modification and had the computer retuned. Swapped engine in 85 chevy and it will not start.

What I know is that it cranks over, fuel pump is working and has proper pressure at test port. It seems that the coils are not getting fire but Im not sure if Im checking correctly. I have checked crank sensor and cam sensor for proper operation and it seems that they are working correctly and there are no codes on pcm. Where do I go from here? Im really starting to regret this swap so if someone could point me in the right direction I would very much appreciate it.
 
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Did you disable VATS? Either by putting the proper resister in the harness or better yet programing it out of the PCM.
 
the vats should have been disabled by the guy that programed my pcm but Ive been curious if it got done. Is there a way I can check to see? I have a friend with a good pcm I may hook up and see if that makes a difference but if its just the vats I need to take it back to the guy that programed it for me.

Another thing that I didnt know about was the tcc brake switch. From what I read it is part of the auto transmission control and since Ive got a manual I didnt hook it up. Should I go ahead and hook that switch up?
 
The tcc switch shouldn't affect the engine starting. What year and model LS are you working with?
 
The crank sensor is used primarily for misfire detection but does some timing reference. The cam sensor is used for most spark and injector timing reference so I would double check both sensors operation.
 
I have replaced the cam and crank sensor with known good ones and it made no difference. I will check the wiring to make sure that the wires are good.

Thanks for the links, may check out that forum for some more info.
 
They are a good group for the most part. A lot of camaro and vette guys but they all seem to get excited when a LS swap guys gets on the board. Currently there is a guy working on his LS swap into a Z34.
 
First off I want to thank you for your help, second Im a moron.

While reading through the responses in the two links that you posted it got me to thinking about my power source. One battery hot and one ignition hot running to the pcm-not all ignition hot sources stay hot when the key is in the start position. Since it is hot in the on position and I was turning the engine by hand to check sensors everything was checking out good but once I turned the key to "start" the pcm was losing ignition hot. Once I hooked the pcm to an ignition hot source that stayed hot it fired up before it cranked a full revolution:doah:

Again thanks for your help, Ive learned a lot about these engines in just the past week.:bow: And hopefully my experience can help some others with no start issues.
 
Glad it was easy. LS engines make great power and there electronics are fairly simple and robust. The 4.8 is the most undersung of the group. They make good power for only a few bucks. Hotrod magazine got almost 1000hp hopping up what they thought was a 5.3. When they pulled the heads it turned out to be a 4.8. I haven't had my LS Camaro for 3 years now and have forgotten quite a bit unfortunately.
 
Ok I got the vss from dakota digital (pn sen-4160) and had my pcm tuned for the 8000 ppm sensor but the wiring isnt making sense to me. The wiring on the sensor has speed signal output and ground. The original wiring for the speed sensor in my harness has a ppl/white which is speed sensor signal and then a grn/blk which says speed sensor reference low.

Not sure how to connect these two together. again, any help is appreciated.:bow:
 
I have been searching all over for that answer! Even Dakota Digital tech help had no idea. They told me hook up voltage from signal to either wire and cap off the second wire and sensor ground :eek1:
 
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