I already have a fuel pressure gauge that I can hook up inline with it.I just dont have fuel pressure tester to check it at the rail. I will hook it up and see what happens. I already have a snap on DMM. But it doesnt have the ability to check duty cycle. I dont really want to go out and buy another one. I can probably get a noid light for less. I let you know what I figure out once I get it set up.

When you say disconnect the fuel pump and crank it and see if pressure drops. Won't the pressure drop from the return line anyway while cranking?

 

After disconnecting the exhaust. The car now turns over a lot faster but it still wont start. Still working on checking the injector pulse. Im pretty sure its not getting gas. Because after I disconnected the exhaust I could smell the carb cleaner that I had sprayed in there. But I can't smell any gas out the exhaust.

 

O.k I got the car started with starter fluid it died shortly after. I'm not getting any injector pulse. Is there a certain ground for the ecu that might have gone bad. Or did the ecu just go out?

 

The LED light will tell you if the ECU is problematic. Another thing is you'll only get injector pulse for the primary injectors and not the secondary injectors as is.

 

Which injectors are the primary's? The ones on top or the ones under the intake? Currently im hooking up the fuel pressure gauge.

 

Maybe fuel filter clogged? You sure your getting enough fuel?

 

The ones on top are the secondary injectors which will only fire at 3800 rpm or higher so to check the primaries w/o taking off of the UIM would require the use of the ECU.

 

Im not sure if its getting enough fuel. I have already bought a new fuel filter that I will install at the same time that I put on the fuel pressure gauge. I think even though the fuel pump is working that maybe it isn't supplying enough fuel pressure for the injectors to fire. I'm picking up a noid light here in a little bit so I will know for sure if the ecu is grounding out the injectors.


O.k I wasn't sure about the injectors. I will find out here shortly exactly whats going on.

Thanks for all the help guys.

 

If the light flashes at the ECU when set up properly that will tell you the ECU is okay when trying to fire the primary injectors.

 

You're not going to crank it. You're going to physically ground any injector after you have fuel pressure. Get a wire, insert one end from behind the connector on the ECU, and then ground the other end. That will open the injector allowing pressure to drop. Then re-hook the pump and try cranking. The fuel that was sprayed should be enough to get the engine spinning past 500 RPM. If it then dies, and you're sure you have both spark and fuel pressure, it points to no injector cycling.

The pressure will not drop while cranking if the injectors are not opening. That's what the pressure regulator is for. Return line is after the regulator.

PS- A timing light will let you know if it's sparking when cranking from inside the car. It's easier that way to check for spark. You will also notice if the engine dies because of spark loss.

 

O.k finally getting back to working on this car. I hooked up a fuel pressure gauge. I have close to 40psi while cranking it doesnt drop off. So I assume the fuel pump is still good. I grounded out the injectors manually and it tried to start. I then took a l.e.d probe and checked the wires for the injectors from the ecu. The ecu is not grounding out the injectors. So does this mean the ecu is bad or is there a ground or something that I need to clean/fix?

 

If the car doesn't run you can't read the secondary injector pulse because it doesn't fire until the engine is under load and 3800 rpm thus the only injector pulse to be measured would be the primaries only.

 

I read the primary injectors pulse. There isnt any pulse. The ecu isn't grounding out the injectors. I checked for pulse at the wiring for the ecu at the pins.

 

So you have voltage on the primary injector wires w/key to on and when the key is turned to start the LED light does not flash? And you have the positive LED wire going to pin 1B for example and the other LED wire going to either pin 3W or 3Y.

 

Correct. There is power at the wire. The l.e.d when hooked up doesnt flash. This means the ecu is bad correct? Also what could fry the ecu? I was talking to a guy and he said the only thing could fry the ecu would be the oil metering pump. Is this correct?

Another thing I found out today. The ecu in the car is a N351 but the original ecu was a N353. Does this make a difference? The ecu was replaced before I bought the car previously.

 

O.k so I got a hold of the PO and I was able to get the original ecu that was from the car. The ecu was replaced due to water damage. I reinstalled the computer and the car fired up and starting running. It has some issues because the ecu I got from him is bad but the car now runs.

What would cause the driver circuit to go out on the other ecu? Do I need to replace the omp? I dont want to drive the car because I'm afraid that this ecu will burn up as well.

Thanks for all the help so far. Appreciated.

 

The N353 was for a S5 convertible while the N351 is for an S5 coupe NA. I thought they were interchangeable. How about checking for codes. On the S5 just ground the Green single wire check connector located by the leading coil and with the key to on the error codes should be displayed.

 

I dont think the car is throwing any codes but let me go check it out and see. What would cause the ecu to burn up? With the old ecu back in that is water damaged the oil pressure gauge doesnt work and some other things.

 

The car isnt throwing any codes. O.k so I found a good N353 ecu but they want $250 for it. My car was running on a N351 and to buy one of those its only$150. Can I get away with just putting in another N351 ecu or should I get the convertible N353 ecu? Also where can I get a new oil metering pump from?

 

Anybody have the digram of how to check the OMP? I need to make sure its bad before I replace it. Thanks