S5 Vert, Injector problems, no pulse
 

I have a 91 convertible, was my car sold it, then that owner took motor out to swap and then didnt, then I ended up buying back. Went out and bought a s5 motor from and auto (car originally manual) all the harnesses were still in the car, switched out flywheels. Got it installed, no emissions, everything blocked off. Now time to start it. I have spark, fuel pump works, lines have pressure, but theres no gas being sprayed in.I have started it on starting fluid. Ive been reading up on it and cant find a solution. I have oower at the ecu for the injectors( light green wires with red black and white lines) all read 12v with the key on... but still dont start. So thats where im stuck at! Any advice or other tips would be nice. Maybe im over looking something.

The voltage on the lead injector wires at the ECU should drop w/key to start as this indicates the ECU is trying to fire these injectors. An LED w/one wire to the ECU injector wire and the other LED wire to a ground and w/key to start the light should flicker, again indicating the ECU attempting to fire the injectors. Also, was the replacement engine a USDM or JDM. If it was a JDM then make sure you have the fuel lines connected properly as they are reversed from how a USDM engine has them orientated which would prevent the fuel from reaching the injectors properly.

Its a USDM motor, lines arent backwards. Got to mess with it last night. Tested injectors, they tested fine. Tested power at the ecu got it. Then tezted at the plugs, and I had power so in theory everything should work. Bolted intakes back together. Go to start it, fires up for a second then dies (which before it would only start off ether). So I must of over looked something csuse its all going now, but the timming and tps need to be adjusted. While starting it it will fire up die and still starting it fire up die fire up die.

Locate the circuit opening relay, under the dash and to the right of the steering wheel column. On the bottom row are two wires, one Black and the other Brown. Jumper these two wires. This will bypass the ECU's ability to cut the signal to the relay which would turn off the fuel pump. On an S5, the ECU is responsible for providing a ground signal to the relay immediately after the car starts. Without the signal the fuel pump would turn off right after the car starts.

If the above is not your issue then a large vacuum leak would cause a car to die after starting.

Okay, I think I have that relay jumped for the fuel pump to kick on. I should probably replace that relay. When it would start, if I could give it gas at thecright time I could keep it reved but at like 5000+rpms

The ground signal comes from the ECU to tell the relay to keep powering the fuel pump. You need to figure out whether the ECU is providing the signal or not. If it isn't then it's a function of the ECU and not the relay. If the relay is getting the proper ground signal but not providing power on the Blue wire (powers the fuel pump) then the relay would be at fault.

Yeah, that relay is bad. Thats why I had to jump it to turn the pump on. Didnt know what other functions go thru it. So ill try to grab new one tonight or atleast jump it to see if it works.makes sense.

Having to jumper the Black wire to the Brown wire to get the relay to power the pump does not immediately tell you that the relay is bad, which I'm not sure you understand the role of the ECU in the equation.

Okay, how can I test if the ecu is sending the signal??

Pin 3K of the ECU is where the Brown wire runs to. W/key to on and the engine not running it will read 12 volts. W/the engine running it reads below 2 volts. Since you cannot get the engine running it changes things. On an S4 all that would need to be done is to pull open the AFM flapper door w/key to on and the Brown wire has the ground signal on it. Not sure the same is true for the S5 as it doesn't have a flapper but a cone and am not sure that pulling the cone has the same affect as the flapper door opening on an S4 but you could try it. The thing is w/the jumper in place the relay is receiving the proper ground signal and should cause the Blue wire in the relay to have power and the car should start. If it does not start and stay started then the problem lies elsewhere.

Additionally, if the timing is not close the car will not start. There are many threads illustrating how to set the CAS close enough to spec where the car should start and run. And if the injectors are clogged (primaries) the car will not run. Not sure how you tested your injectors.

Ive put this cas in correctly a million times now and still starts dies..

Just checked the brown wire it reads 12 and for the couple seconds it runs it was under 2 volts

Remember, a vacuum leak will cause these very same symptoms.

hope you have the AFM installed....

can't count how many times i've seen people run around in circles with the most important part of the car laying in a box on the floor.

^^^^ So that kinda happend but with my idle control valve.. so...yeah it runs and idles now. I feel like a dumbass lol one of those things just completly overlooked. Cause ive blocked some stuff off.learnin as I go! Thanks guys!