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AMEDEE
AMEDEE, FORD TECHNICIAN
Category: Ford
Satisfied Customers: 21666
Experience:  ASE MASTER TECHNICIAN ADVANCED LEVEL SPECIALIST. Wisconsin certified emissions state inspector
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1990 Ford Tempo: Ignition switch..run fine..warmed..I rev it up it

Customer Question

I have a 1990 Ford Tempo that I have replaced the Ignition switch and the Starter Solenoid on. The problem is that the car will start when it has been sitting over night and run fine until it is warmed up, or I rev it up to high RPM. When I rev it up it starts to miss and then all together quits. Then the car will only start and run if the key is kept in the "start" position. Once this occurrs it will remain running if the wire to the solenoid is removed. It seems as though the ignition is being grounded out. Can someone explain why the car will remain running with the wire disconnected from the starter solenoid, buut as soon as I go to hook it back up the car dies? And, once it is hooked back up, why the car will only run with the key in the start position?
Submitted: 5 years ago.
Category: Ford
Expert:  AMEDEE replied 5 years ago.
Hello!

Did you replace the lock cylinder and key?
Customer: replied 5 years ago.

Yes, that was the part that I did not include in my description. New lock cylinder and key was the first part replaced, then I replaced the actual ignition switch located a little further under the steering column, then I replaced the starter solenoid.

Expert:  AMEDEE replied 5 years ago.
With the key in the on position, is the check engine light on?
Customer: replied 5 years ago.
I did not notice it on, so without actually going home and trying it I would have to say no. I can give you a more solid answer after 7:30 PM PST tonight though.
Expert:  AMEDEE replied 5 years ago.

Sounds good!

 

Let me know!

Customer: replied 5 years ago.
Ok, so the Service Engine Soon light is on when the key is in the on position.
Expert:  AMEDEE replied 5 years ago.
Ok... good!

now lets get it warmed up and get it to act up to the point where it will not start. I want you to check fuel pressure and check for spark on all spark plugs when cranking when this happens. Also, see if it will run on starting fluid.

Let me know what you find.
Customer: replied 5 years ago.
Ok, at this point it will not run on its own. It will start and run fine as long as the key is in the "start" position. Once released the engine shuts off.
Expert:  AMEDEE replied 5 years ago.
See if it will continue to run on starting fluid after you let off of the key.
Customer: replied 5 years ago.
No it does not.
Expert:  AMEDEE replied 5 years ago.

Ok.. good!

 

Now lets check for spark. I want to find out the very second you stop cranking, if there is any spark. You might need somebody to help you out and crank it over for you.

 

This is really important!

 

Let me know!

Customer: replied 5 years ago.
Ok, pulled the plug from No. 1 cylinder and it does not have spark when I release the key from the "start" position to the "run" position.
Expert:  AMEDEE replied 5 years ago.

Excellent! We are getting somewhere!

 

Now, we have to figure out if we are loosing power to the coil when this happens, or a ground signal to the coil when this happens. We should be able to test this just with the key in the on position.

 

So... turn the key on and check the wires going into the coil. We should have power to at least one of them.

Customer: replied 5 years ago.
This will take me a while. I have to go down to the store and buy a test light. It is 2:45 PM now, I should return by 6 PM.
Expert:  AMEDEE replied 5 years ago.

SOunds good!

 

Let me know!

Customer: replied 5 years ago.

The test light goes out when the key is released. Further playing around with it it still runs great if I disconnect the lead to the solenoid after it starts. When I ground out the lead it shuts off, and when I plug the lead back on to the solenoid it shuts off.

Expert:  AMEDEE replied 5 years ago.
Ok... We are going to have to do some pinpoint testing.

What I want you to do, is go to the ignition switch wires (coming out of the ignition switch).

THere should be a red wire with a light green tracer. Turn the key on and tell me if you have power on that wire.

I will be waiting.
Customer: replied 5 years ago.
Yes there is power.
Expert:  AMEDEE replied 5 years ago.

Ok.. good!

 

What we are going to do next, is check for power with the key on on this same wire but down further in the circuit. I want you to go to splice 112 and check this same wire for power.

 

Splice S112: Engine Harness, Near Take Out To EGR Vacuum Regulator

 

Or, you could go to splice 105.

 

Splice S105: Dash Panel To Engine Harness, Near Take Out To Ignition Coil

 

Either way, its the same. You should have power on this wire with the key on.

 

Let me know!

 

Here is the wiring diagram.

 

graphic

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