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Amedee
Amedee, Former ASE Master Tech
Category: Car
Satisfied Customers: 26417
Experience:  ASE certified tech advanced level specialist. Wisconsin certified emissions state inspector
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2001 saab 95: Starts and runs great, When I trun car..agian

Customer Question

2001 saab 95, Starts and runs great, When I trun car off and try to start agian, it will not start. Wait 4 to 6 hours it will start up agian
Submitted: 7 years ago.
Category: Car
Expert:  Amedee replied 7 years ago.

Hello!

 

When the engine does not start, does it crank over and not start or does it not even crank over?

Customer: replied 7 years ago.
It cranks over, just wont fire, Like out of gas or no spark to spark plugs. We changed fuel pump 2 times, Both new and very expensive, and we just changed fuel presure vavle and oh yes, we put a new throtle body on.
Expert:  Amedee replied 7 years ago.

We will have to pinpoint what the engine is missing.


Spark


Fuel


Compression

 

All three of these are tested when the engine is being cranked over. There are two way of checking for fuel. Fuel pressure and fuel trigger. Both are very important and must be present for the car to start. Fuel pressure is self explanatory. You just hook up the gage and see what the reading is. Fuel trigger is check with a noid light. The injector gets unplugged and the noid light gets plugged in to the injector clip. With the engine cranking over, this light must blink. This is the signal to the injectors from the computer. You can have all the fuel pressure in the world, but it wont matter if the injector is not pulsing gas into the cylinder like it should! Compression tester, spark tester, fuel pressure gage and noid light are all accessible at your local auto store. All three tests play a very important part in diagnosing a no start condition. Be extremely careful when doing these tests.

 

A simpler test would be to see if it runs on starting fluid. If it does, then you know you have spark and compression and you simply have a fuel delivery problem

 

Customer: replied 7 years ago.

If fuel issue, are you saying change injectors or some control? The pressure was checked when we changed the pump.

 

 

Expert:  Amedee replied 7 years ago.

So the fuel pressure is good?

 

Do we have spark?

Customer: replied 7 years ago.

How to check spark when this motor has inclosed and cant get to spark plugs? Just check with starting fuid is best?

 

Expert:  Amedee replied 7 years ago.

You could pull off the cover and see if there is spark while cranking. You might need an assistant to crank the motor over while you watch for spark.

 

Does the engine run with starting fluid?

Customer: replied 7 years ago.

I will check all this tomorrow, It has sit for 4 hours and it starts now. So I need to drive agian so it will not start. See after it cools down it will start. So it has somthing to do with heat I think. Could this be a coil issue?

 

Expert:  Amedee replied 7 years ago.

It is possible!

 

The most common cause for this problem is a crankshaft position sensor. Check to see if there is spark when it will not start. If no spark, suspect a bad crankshaft position sensor.

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Customer: replied 7 years ago.
I tried the starter fuild, and it started back up and ran.
Expert:  Amedee replied 7 years ago.

SO does it continue to run as of now?

 

Or does it just run with starting fluid?

Customer: replied 7 years ago.

It will continue to run and only takes a small hit of starter fuild to get started. After starting will run forever until you turn car off. Then it will not start until the car sits for 4 to 6 hours. After sitting 4 or 6 hours it will start without starting fuild

 

Expert:  Amedee replied 7 years ago.
DO we know what fuel pressure is when it wont start?
Customer: replied 7 years ago.

I had it checked today and it was same as when would not start, the shop said it was fine, but I forgot to ask the exact pressure

 

Expert:  Amedee replied 7 years ago.

If you can find out the fuel pressure... that would be great...

 

Ask them to show it to you so that you see it with your own eyes. This is the type of thing that we need to be dead sure about before we make a diagnostic decision.



Edited by AMEDEE on 4/2/2010 at 2:08 AM EST
Customer: replied 7 years ago.

I will have to tomorrow. Can I buy a fuel pressue gage at Autozone and where does it screw into?

 

Expert:  Amedee replied 7 years ago.

It should just screw into the fuel rail. Here is a pic.

 

graphic

Expert:  Amedee replied 7 years ago.
YES... you should be able to purchase a fuel pressure gage at your local auto parts store.
Customer: replied 7 years ago.

I will buy my own gage tomorrow, What pressue should I be looking for?

 

If the pressue is good, As I said we changed the fuel pump 2 times, Would anything else limit the pressure to throtle body?

 

Expert:  Amedee replied 7 years ago.

FUel pressure should be about 43 psi. If the fuel pressure is up to par, then we check fuel trigger.

 

If the fuel pressure is low, then we check power to the fuel pump and check for restrictions in the fuel pressure line.

Customer: replied 7 years ago.

Fuel trigger is injector?

 

Expert:  Amedee replied 7 years ago.

Fuel trigger is the signal from the computer to the injectors. You would use a tool called a noid light. It simply plugs into the injector connector after the fuel injector is unplugged and should blink when the engine is cranked over. It looks like this.

 

graphic

Customer: replied 7 years ago.
I will research all this tomorrow and give results
Expert:  Amedee replied 7 years ago.
Sounds good!