1Psycho

iTrader: (9)

Alright so I finally got around to swapping a gen 3 5.3 into my k5. For the harness I reworked a complete truck harness and made a fuse block all according to lt1swap.com. Have it all wired and hooked in to my car and I go to start it...it cranks over but doesn't fire. When it cranks it sounds like I don't even have the coil packs hooked up, like there's no compression or even a hint of trying to start. I checked the plugs though and it is sparking so thats not the problem. Fuel pump is fine and pumps for 2 seconds before start and is pumping fuel through it and it's getting up to the rails. Popped one side of the rails up to check the injectors and they're dry. Why wouldn't the injectors be pumping fuel? If it was VATS wouldn't it start for a second or two then shut off? The injectors are wired to go on with the coils and the coils are working so the injectors should be working....?

i r teh noobz

iTrader: (4)

VATS disables the injectors. Its supposed to work for a few seconds, but sometimes they don't fire at all.

Make sure you have power to the injectors. Then check to see if the PCM is pulsing ground (a test light works fine if you don't have a noid light set). If you have no ground pulse, suspect VATS.

A little starting fluid can rule out compression or timing issues.

jborders

I had problems with mine also. turned out to be a couple of things. One make sure all your power sources are hot while cranking i had one that was hot with key on but while it was cranking it lost power. The second was that if the injectors have been sitting for a while they get stuck closed. I had to let them soak all night in injector cleaner and tap on them lightly with the key on to get them all unstuck. it's a common problem i've read. worked for me good luck.

1Psycho

iTrader: (9)

Sprayed a little starting fluid in it and it fired right off.

I'll check that pulsing ground and see if it is or isn't, in the meantime I'll try cleaning the injectors out since they have been sitting around awhile so theyre probably stuck. Thanks guys!

psiconversion

iTrader: (5)

Agree with JBorders. Make sure that any 'KEY ON' power sources have power WHILE cranking.

Jon
PSI

1Psycho

iTrader: (9)

Well each bank of injectors is wired with that same bank of coils to the same fuse and the coils are sparking so they should be getting power while cranking but I'll have to check today

1Psycho

iTrader: (9)

Checked today briefly and the injectors are seeing 4-6 volts during cranking..is this normal?

busta9876

iTrader: (3)

simple check, helps to have a spare injector connector.

hook each injector directly to 12v+ and ground for just a brief moment, listen for a click noise. If each one does not click, they are not flowing any fuel.

do not hold power to injector, just tap power to it just as quick as you can apply and release , listen for the noise.

-Brendan.

1Psycho

iTrader: (9)

thanks man, found that one out a little while ago and also found out 7 out of my 8 injectors arent firing..awesomee

1Psycho

iTrader: (9)

anyone? how many volts should the injectors have during cranking?

i r teh noobz

iTrader: (4)

Should be somewhere around battery voltage. Cranking spec should be somewhere in the 9-10 volt range. The offset tables in HPTuners go all the way to 4.5v.

1Psycho

iTrader: (9)

So then if it's getting 6, will it not fire up and run? is that vats doing that? or just loosing current somewhere?

i r teh noobz

iTrader: (4)

Power comes from your fuse/relay setup. The PCM provides GROUND to activate the injectors. All VATS does is prevent the PCM from grounding the injectors. If you only see 6 volts to the injectors while cranking, you have a weak battery or bad wiring somewhere. It has the data to pulse the injector properly at 6 volts, but anything under 9 is generally to low for the engine to fire. I doubt 6 volts to the starter would even make it turn over.

You said the coils are wired to the same 12v source? Are they only getting 6 volts? What is the battery at while cranking?

1Psycho

iTrader: (9)

I'll have to check fri/sat when I'm back around it again. The battery has been sitting around a few months so that could be the problem but we'll see how it all goes then and report back