injectors not firing?

[02sweet]

Hello all I have spent the past 2 days trying to fix my 74 spider with a 83 FI motor in it. I bought it used drove it daily for a month or two and two nights ago it wouldn't start. I figured it out to be a fuel pump problem. Replaced the fuel pump and now I am not getting fuel to the injectors. The motor turns over and doesn't run. If I dump fuel into the motor it runs till the fuel is burned out.

So here is what I did so far:
Tested the double relay
Tested the temp sensor via the ecu
What else can I do to diagnose the problem?
Checked and tested the grounds on the valve cover

Is it as simple as a bad ground?

[kmead]

I would use go through the trouble shooting in these manuals.

Start with this download:

http://dl.dropbox.com/u/3359580/Bosch%2 ... Master.pdf

and then look at this:

http://dl.dropbox.com/u/3359580/Spider% ... 0%2081.pdf

[02sweet]

I would use go through the trouble shooting in these manuals.

Start with this download:

http://dl.dropbox.com/u/3359580/Bosch%2 ... Master.pdf

and then look at this:

http://dl.dropbox.com/u/3359580/Spider% ... 0%2081.pdf

Thanks I haven't seen those before. I will look into them and see what I come up with.

So I pulled the tps sensor and I am getting .2 resistance when closed and at wot and nothing in between. Is that a bad sensor or good?

[kmead]

The TPS only tells the brain that the throttle is either on the rest (closed) or open, this injection system doesn't use the throttle position to do anything beyond enabling the rudimentary idle control valve or AAV.

This is a good article, its about an Alfa but LJetronic is LJetronic:

http://www.hiperformancestore.com/Ljetronic.htm

[02sweet]

I have replaced the double relay and still having the same problem. I went through all the steps on just about every manual I can find and the injectors still won't fire.

What are the requirements of the ecu to fire the injectors?
How do I test for it?
Is it something in the ignition?

When I put fuel into the TB the car will run but when it runs out of fuel it doesn't

I checked all my grounds and I am really stumped.

I read somewhere that a bouncing tach means something. When the car was running the tach would bounce at times.

[divace73]

is your fuel pump running when you crank your ignition? (if not then check the safety switch in you AFM)
If we assume you do have pressure behind your injector, then ensure the tach wire that goes to computer is getting pulse from the low tension side.

You also have to ensure the circuit is complete for your injectors?
The ECU needs to be grouned as well and the ground wire that should be connected to the intake manifold.

hope this helps

[rlux4]

The dual relay sends power to the fuel pump whenever the engine is turning over. You've changed out the dual relay, now you need to check that you're getting fuel at the injectors. An easy way to do this is to disconnect the hose at the cold start injector and have a helper crank the engine. With the hose pointed into a jar, see if you're getting a good, solid stream of gas. Be careful when you disconnect the line from the cold start injector, if you are getting gas it'll spray out pretty hard. If you're getting fuel to the fuel rail, the next step is to check that the injectors are firing. A noid light is the best way to do this. You can get one fairly cheaply at an auto parts store. It plugs into the connector for the injectors and it's light will pulse if you're getting signal. I've tried a test light and an VOM to test here and neither one worked as well as a noid light.
Ron

[02sweet]

is your fuel pump running when you crank your ignition? (if not then check the safety switch in you AFM)
If we assume you do have pressure behind your injector, then ensure the tach wire that goes to computer is getting pulse from the low tension side.

You also have to ensure the circuit is complete for your injectors?
The ECU needs to be grouned as well and the ground wire that should be connected to the intake manifold.

hope this helps

The fuel pump does run when i crank the ingition.

Yes I have fuel pressure behind the injectors.

To test the tach wire that goes to the computer which one is it? what pin on the ecu?

What are the grounds for the ecu. The grounds for the injectors going to the intake manifold have been removed cleaned and reinstalled.

[02sweet]

The dual relay sends power to the fuel pump whenever the engine is turning over. You've changed out the dual relay, now you need to check that you're getting fuel at the injectors. An easy way to do this is to disconnect the hose at the cold start injector and have a helper crank the engine. With the hose pointed into a jar, see if you're getting a good, solid stream of gas. Be careful when you disconnect the line from the cold start injector, if you are getting gas it'll spray out pretty hard. If you're getting fuel to the fuel rail, the next step is to check that the injectors are firing. A noid light is the best way to do this. You can get one fairly cheaply at an auto parts store. It plugs into the connector for the injectors and it's light will pulse if you're getting signal. I've tried a test light and an VOM to test here and neither one worked as well as a noid light.
Ron

I didn't test the cold start injector yet. I will try that out tonight.

I tested the injectors and they are not pulsing like the should. I removed the entire fuel rail and and not one is firing.

Do you think the fact that my tach was bouncing for a week or two before this problem happened is something to look into?

The PO of the car didn't do a clean job on the wiring when he put the 83 motor in. So its a little hard for me to diagnose what is connected.

[rlux4]

I don't understand how you can have fuel at the injectors if your fuel pump isn't running. And you may have misunderstood what I was saying about the cold start injector. It wouldn't really matter if it's working or not unless your starting in very cold conditions, and then it only runs for a few seconds. What I suggest is that you use the fuel line going to it to test for a strong, steady flow of fuel. However, if your fuel pump isn't running this is moot. First off you need to get fuel to the injectors; you can do this either of two ways. With a helper, put a test light on the brown with white strip wire at the dual relay. When the ignition is turned to "on" it should have power. If it doesn't, look for the inline fuse on that line up behind the main fuse panel. If it does have power, turn the key to "start", check the green with black strip wire at the dual relay, it should have power (it goes to the fuel pump, and should have power whenever the engine is turning). Then check that you have power at the pink with black stripe wire when the key is "on". With power at these two wires you should get power at the green with black stripe wire when you crank the engine.
Once you've diagnosed why your fuel pump isn't running it'll be time to check why you're not getting pulse signal at the injectors. It's most likely a ground issue if all four are affected. Check that the two ground wires are connected at the rear outer intake plenum hold down bolts. There should be two of them, each having two grounds in the sheath for the injector grounds. The circuit to pulse the injectors is controlled by the ECU, by interrupting the ground signal.
There are very good diagnostic manuals available to help you, do you have any of these?
Good luck.
Ron

[02sweet]

Ron,
The fuel pump is working. I do get power through the relay wires.

I replaced the fuel pump b/c the one that was in the car went. I tested the old one with 12 volts and it was dead.

I can remove the grounds again on the valve cover and clean them. I have followed just about every manual I can find. That lead me to replacing the double relay and fixing a the brown fused wire.

What gets me is that I had a friend spray fuel into the TB while i was starting it. Car fired right up. As long as he kept putting fuel in the TB the car would run.

This has stumped me big time, and the only thing I can think of is the ECU is the problem. But not to the point that its bad but just that one of the wires is cut or a bad ground!

I printed two diagrams off of Marks website to go over tonight for the wiring and see where this goes. I find it funny that I d/d this car for 2 months and put 4,000 miles on it. Then one night I went to leave to get something to eat and it wouldn't start. That night I diagnosed the fuel pump wasn't getting power. Fixed the fuse, noticed the fuel pump wasn't turning on and replaced that too.

[rlux4]

Check your private message.
Ron

[nadman009]

Did anyone ever solve this problem? I have the same exact issue on my 82' FI and I'm in the process of changing the dual relay. But i get the feeling that replacing it will have no effect. How exactly should the ECU be grounded?

[narfire]

I have the same exact issue on my 82' FI and I'm in the process of changing the dual relay.

Have you done all the other checks regarding fuel flow, spark, grounds, timing ect? I believe the relays and ecu have been known to fail, but from my experience most issues have been the grounds and or perhaps a sensor conection not right.
An injector could be plugged but not all 4 at the same time(pull conectors to see if there is a difference)
Chris