Fuel is getting to injectors, but the injectors arn't spraying - 3000GT/Stealth International Message Center
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Old 07-04-2007, 06:16 PM   #1 (permalink)
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Default Fuel is getting to injectors, but the injectors arn't spraying

Ok, adding on to my no start problem, I've narrowed it down to something that controls the injectors. I physically popped the front rail up and made sure it was the injectors not spraying. Fuel is getting to them, I took the rail loop off and turned it over... gas came out. I've tested the resistor pack, 6.1ohms across all of them.

From the rear injector harness (held onto passenger side of plenum) I've tested the voltage with the key in the on position. I've read that one row of the 2x3 pins goes to the resistor pack and should get 12V, and that the other row goes to the ECU, which fires the injectors when grounded (by ECU).
One row of pins showed 12V across, the other row showed 11.97V across.

Is this right? Is my ECU bad? could it be the MFI relay (not sure if it has anything to do with my problem)? It's a '91 so I have the head-mounted CAS, could a faulty CAS cause this?

I hope this is the final stretch of my trouble shooting, so thanks everyone

-Evan
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Old 07-04-2007, 09:43 PM   #2 (permalink)
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Default Re: Fuel is getting to injectors, but the injectors arn't spraying

Sounds like the ECU isn't grounding the injectors. Check your fuses--Engine fuse under the dash-- And the MPI fuse under the hood. I am positive the MPI fuse will kill the injectors. It's a 20 amp fuse. If that dosen't work ask around for a ECU to slave in.

All your troubleshooting sounds really good so far. If your MFI relay was bad you wouldn't get fuel to the fuel rail.

If your CAS was bad you wouldn't have any spark. Ensure you use the metal clip on the CAS cannon plug. If it comes loose just a little it can cause you to loose spark.

Last edited by 3000hybrid; 07-04-2007 at 09:51 PM.
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Old 07-04-2007, 11:34 PM   #3 (permalink)
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Default Re: Fuel is getting to injectors, but the injectors arn't spraying

What about spark? Do you have that?

If you have neither, I would lean towards there being an issue with the pickup sensor or whatever they call it on these cars. Without a pickup signal, the engine computer is not going to fire injectors or fire the ignition coils because it doesn't think the engine is actually spinning.

I am not sure what CAS means, but that sounds like the pickup sensor I am thinking of.

Last edited by phantomrt; 07-04-2007 at 11:36 PM. Reason: .
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Old 07-04-2007, 11:38 PM   #4 (permalink)
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Default Re: Fuel is getting to injectors, but the injectors arn't spraying

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What about spark? Do you have that?

If you have neither, I would lean towards there being an issue with the pickup sensor or whatever they call it on these cars. Without a pickup signal, the engine computer is not going to fire injectors or fire the ignition coils because it doesn't think the engine is actually spinning.

I am not sure what CAS means, but that sounds like the pickup sensor I am thinking of.

CAS= Crank angle sensor

Yep it's the pickup you are talking about.

*Remember you can have spark with fouled plugs. It will be no spark or even weak spark on a fouled plug.
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Old 07-05-2007, 12:41 AM   #5 (permalink)
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Default Re: Fuel is getting to injectors, but the injectors arn't spraying

spark is good to go, i even tested as far as to pull a few plugs at a time, plug them to the wires, ground them, and crank the car over. bright spark. I am possitive that its something that controls the injectors.

I've checked all the fuses that it could be and they all check out, but I will look at them tomorrow again.
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Old 07-05-2007, 08:24 AM   #6 (permalink)
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Default Re: Fuel is getting to injectors, but the injectors arn't spraying

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spark is good to go, i even tested as far as to pull a few plugs at a time, plug them to the wires, ground them, and crank the car over. bright spark. I am possitive that its something that controls the injectors.

I've checked all the fuses that it could be and they all check out, but I will look at them tomorrow again.
It sounds like a bad ECU.
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Old 07-06-2007, 02:52 PM   #7 (permalink)
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Default Re: Fuel is getting to injectors, but the injectors arn't spraying

Is there anyway at all a bad CAS cause this? Also, when i loosen the fuel loop and try to start it fuel comes out, but isnt very very preassurized.

Do the injectors require preassurized fuel to spray? There IS fuel in the rails, but the injectors arnt firing.

I'd think the fuel would really pour/spray out of the rail loop when trying to start the car.
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Old 07-06-2007, 08:09 PM   #8 (permalink)
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Default Re: Fuel is getting to injectors, but the injectors arn't spraying

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Originally Posted by eko87 View Post
Is there anyway at all a bad CAS cause this? Also, when i loosen the fuel loop and try to start it fuel comes out, but isnt very very preassurized.

Do the injectors require preassurized fuel to spray? There IS fuel in the rails, but the injectors arnt firing.

I'd think the fuel would really pour/spray out of the rail loop when trying to start the car.
Fuel isn't going to pressurized when you open the fuel rail. It should come out pretty good, but not pressurized. That's the FPR's job to regulate the fuel rail pressure. It can't do anything on an open rail. A bad CAS would not send a signal to the ECU to let the ECU know when to send a spark signal. Hence, no spark. But you have spark. Also from this CAS signal the ECU will know when to send an injector pulse signal. If you have spark the ECU should be recieving it's signals from the CAS, but it seems to me the ECU is not sending an injector pulse signal to the injectors to coincide with the spark signal. Pull your ECU out and check the caps for damage. Especially since you have a 1st Gen TT. Original caps are known for going bad when they are that old. Below are directions from Setealth316 on how to pull the ECU to check it. It's not very difficult to check. Let me know what you find.

http://www.stealth316.com/0-frames.htm

Last edited by 3000hybrid; 07-06-2007 at 08:14 PM.
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Old 07-06-2007, 11:11 PM   #9 (permalink)
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Default Re: Fuel is getting to injectors, but the injectors arn't spraying

I checked my ECU and it looks fine, but I guess it could have leaked directly under the CAPS? I'm not sure, but anyway, i took the chip, looked on both sides and it looks perfect.
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Old 07-07-2007, 12:56 AM   #10 (permalink)
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Default Re: Fuel is getting to injectors, but the injectors arn't spraying

Well, try checking your CAS and TPS with a multimeter. Also verify the check engine light comes on with battery power and then goes off. If you have no check engine light you don't have power to the ECU. Let me know the results of the test. Especially if you have a check engine light or not.

Try spraying a little engine start fluid in the TB and see if it trys to start.

Do you have a factory anti theft system preventing the car from starting?

Last edited by 3000hybrid; 07-07-2007 at 01:09 AM.
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