Primary injectors not turning on...
 

Hi everyone, first of all let me give you some details on the car: It's an 1991 FC S5 Turbo II, and I just finished rebuilding the engine a couple weeks ago. Now I've been trying to start it ever since, because there seems to be no fuel getting into the engine. I've narrowed it down to the primary injectors not spraying while the engine is cranking.

Things I've done:

- Checked impedence of injectors: all read 14 ohms, in spec
- Fuel gets to the rail, replaced fuel pump a couple days ago
- Checked ECU pins for voltage while key to ON: all 4 light green wires read 12V
- Checked ECU pins while cranking: wires show around 6V (which tells me the ECU is sending pulse since the multimeter cannot exactly show the pulse so it gives a value between 0V and 12V)
- Checked voltage at injector connector pins when key to ON: 12V on one pin (grounded to frame) and 0V for the other (grounded to frame as well)
- Tested the injectors by feeding them direct voltage from a 9V battery and they spray, even almost started the engine from the little bit of fuel after I cranked it
- All my fuses are good, tested each and every one of them (4 times for the EGI...)
- Checked and redid all grounds, sanded them and used dielectric grease to make sure they're all good

I really need your help...I'm running out of ideas. I have kind of ruled out the CAS since I have spark (starts a bit with starter fluid). Like you probably all know I've spent a lot of effort rebuilding it all, I just want to hear this baby run. Any ideas on why those injectors won't fire up?

Thanks a lot for the help!

Could you explain this in a different manner? W/key to on both injector pins should have 12 volts. The B/Y and Green wire w/stripe are to both have 12 volts.

Secondly, is this a USDM engine or a JDM?

Thirdly, do you have a spare CAS?

Hey satch, thanks for the reply

1) With the positive terminal of the multimeter on the pin from the green wire on the injector connector plug, and the negative terminal on the ground located under the UIM, I get a 12V reading when the key is ON. Then I tried the positive terminal on the B/Y wire pin and got a 0V reading. I'll check to see if the B/Y wires coming out of the ECU show 12V, which they should, right?

2) This is a USDM engine

3) Sadly, I don't have any spare CAS. However, from what I've read on other threads, shouldn't the CAS be pretty much okay since I get proper spark? I'm not sure if the working order of sparks and injectors are mutually exclusive when it comes to the CAS.

Thanks for the help

The B/Y wire does not come from the ECU. It comes from the main relay. The B/Y wire(s) at each of the coils is the same B/Y wires found at the injectors. If you do not have voltage at the coils w/key to on then check to see if you have this voltage at the relay. If you do not then check the connections at the relay. If you have voltage at the coil's B/Y wires then your problem lies near the ECU where wires coming to that area (some ending at the ECU and some not) reach 2 major connectors. On an S5 I believe they are labeled X-11 and X-12 and X-11 is the one which houses these B/Y wires. At one of these connectors you would find two B/Y wires coming from the coils and then they mate w/two like B/Y wires on the other side of the connector which then feeds the injectors.

Okay so I tested the coils, and they both show 12V on the B/Y wire. I also tested my main relay for continuity and it's good. Now I went down to check the ECU and the X-11 connector you told me about, and it all looked properly connected with regard to the wiring diagram. Here's a pic:

http://imgur.com/Dk4uIq1

What would prevent the 12V at the coils from reaching my injectors? Thanks for the help

You need to test both sides of the connector to see if you have the required voltage necessary on each side of the connector. Pics have little value here.

I thank you for all your help, but I've come to the realization that I'm an idiot. See those two plugs? Yeah, I left them unplugged lol. She fire right up! And then after 5 minutes I had to shut her off cause my front oil cooler line exploded and filled my driveway with oil. Any recommendations on good after market oil cooler lines? :)

Thanks!

I wouldn't know about the oil cooler.