78rado

Ok little info: 78 c10 I used stock th350 and an 01 4.8l with factory harness, computer and fuseblock..(.im going for ultra easy to work on DD) so I sent the comp to LT1swap.com and requested the egr,2nd o2s, m.a.f. and I thought the PRNDL all to be removed...then I wired it like his site said hit the key and nothing now if I go jumping wires I can get things to work...so im thinking its the PRNDL wasnt removed and the comp dosnt know what gear its in...any imput please thanks

aknovaman

iTrader: (7)

Did you ask for vats security to be deleted? If not it will still prime the fuel pump and fire for 1-3 seconds then die.

78rado

Sure did sorry forgot to mention that...yeah I get nothing

aknovaman

iTrader: (7)

Injectors stuck closed with gummed up gas residue.

78rado

That will cause a no crank? When I say I got nothing I mean nothing no power going out...except for the fact that I do get injector noise when I do key on.but run/start I have no power to starter, fuel pump nothin...kinda weird

i r teh noobz

iTrader: (4)

Sounds like an ignition switch issue. Are you sure everything is wired correctly? The PCM should have nothing to do with the engine cranking over.

78rado

Yeah im pretty sure its wired correctly I get dash lights and if I bypass the pcm and touch the ign. Wire to a start wire and hit key it will turn over...

sweetk30

make dead sure all 12volt hook ups are key hot AND key hoy crank .

seen a guy spend a whole day tracing down a intermit fire for 1-2 sec and stop . he swaped in a lt1 in a truck and used a painless kit . all was perfect . but he got 1 hot wire on a 12 volt key hot NOT hot in the crank also . some times on a slow roll back from start position the ign switch still made contact barly inside and made it pop for a sec and die .

figured this out and moved it to key AND crank hot spot and fired right off no problems .

and if you did little tweeking under dash recheck park/n safty wiring and switch . make no power come out to the starter purple trigger wire .

BigEd_72455

iTrader: (7)

First thing you need to do is figure out if you have power coming through the starter circuit under the dash at the ignition.

Where are you located at?

Do you have a good digital camera that you can take pictures of the wiring under your dash?

BigEd_72455

iTrader: (7)

When sending a ECU to lt1, he automatically does that for stand alone.

Disables vats, turns off second O2's, sets electric fan control based on thermostat temp you are running.

78rado

Im in iowa...yes I have power going out to the engine bay...key on/run...so can anyone tellme for sure if not having a PRNDL switch hooked up wont cause a no start...im thinking if the comp dosnt know what gear its in it wont alow it to start...?!?!

BigEd_72455

iTrader: (7)

you don't have a transmission that the computer deals with. The neutral safety is handled by the trans itself. Not the engine computer.

The fact you have the TH350, they don't have a built in neutral safety.

Did you figure out which wire should be sending power to the starter from the ignition switch? Have you traced it out with a test light to make sure nothing is broken or shorted out somewhere?

BigEd_72455

iTrader: (7)

you indicate power is on during key ON/RUN.. but what about when you turn the key to START??

smokin91rs

iTrader: (16)

yes if the truck pcm does not have a prindle or nuetral saftey turned off it will not start. i went through this with a 10 swap i beleave the starting circuit rns through the prindle. i remeber jumping a wire or relay and we were able to fire it up and let it run. look at a schmeatic

78rado

Hey guys thanks for your time and helping a fellow builder with my prob....this isnt my first build but its my first fuel inj. Swap like this....
BigEd: yes I do have a good wire with a solid 12+v with key on and start run...as far as I can tell ( using lt1swap.coms directions its wired correctly..another note, when I pulled this motor I left the harness pluged in to everything as it was from factory so there shouldnt b any probs there...shouldnt be

Smokin91rs: this was my thought ...if I could just jumper it or if it needed to be resisted to trick the pcm in thinking its in park/neutral....
ive checked and rechecked so many times with this...I feel its godda be somthing easy (small) that im missing....ground maybe....also I found that with using the factory fuse block not all the relays/fueses are being energized...so maybe im missing a hot wire to the block....but im pretty confident that its wired right....ugghhh...

ls1nova71

iTrader: (4)

So you are using the whole fuse box that came with the 4.8 engine harness? If so, the starter relay is in there and with out the range sensor on the side of the transmission hooked up, it won't complete the circuit to the starter relay. Hook up your ORIGINAL purple wire that comes out of your firewall junction block that went to your original starter to the 4.8 starter, and it should start, or at least crank.

78rado

Yes nova if I touch that purple wire to the s4.8 starter wire it will turn over....ok so is there a way to bypass that range sensor? Ill buy the adaptor if thats what it takes but for now id just like to be able to move it around to work on it....

ls1nova71

iTrader: (4)

So what do you have that purple wire hooked to? It should be hooked to the big 4.8 fuse box, but why not just hook it to the starter? If you want to bypass the range sensor and use the starter relay, you'll need to jump two wires on the range sensor plug. Should be a purple/white wire in location E, and yellow wire in G.

78rado

Ill have to go out and look at what its hooked to... its been a few weeks since i played with it...If I run it directly to starter will the pcm recognized the engines running and still take over? Or do I still need to send that signal through the pcm?

ls1nova71

iTrader: (4)

Yes, it will work fine if you just hook it to the starter, the PCM doesn't know what the starter is doing, Once the engines starts, the PCM will see a RPM signal so it will know it's running.