Expert: Skip Bollinger - 5/13/2007

Question
Sometimes I have a no start condition and other times it will start and run for a while and eventually die.

If I told you the whole story behind the car it would be to long.

Here is what is occuring now, when I have a no start condition. I am losing injector pulse. I hooked up a fuel gauge, spark tester and noid light at the same time. Fuel pressure runs 37 to 42 psi and 40 psi at idle when the car is cutting out when it will run it puts out around 59 psi. I have spark the entire time. When the car wont start initially I will have fuel pressure, spark, and no injector pulse, then it will begin giving small injector pulse for a few seconds and the car will act like it wants to fire, then the injector pulse will cut out again and it will not start. When this started notice a double click sound that sound like a relay popping when the problem occurs. I felt different relays etc.. trying to feel where the popping was coming from. I felt the popping coming from the abs ecu or abs computer attached next to the master cylinder. So I know this relay popping that never occured before this problem started is coming from the abs ecu. With this paticular car when you press on the brakes the engine will idle up, when I depress the brakes it idles down.

I have swapped out the ecm (car not abs), swapped out the map sensor, and changed the crank sensor. I am baffled and need help, this is my dad's car and he needs it back up and bad.

Couple of questions do you know what can cause this? Can you supply me with information or a diagram of everything that is responsible for sending an injector pulse signal to the injectors? My last question is I talked to a gm ase certified mech who told me the abs unit on these can cut out the injector pulse if the abs ecu is bad or the abs relay is bad? Is their anything else I have over looked? My last question where is the abs relay located.

Also forgot to mention the check engine light has not come on, has no codes, and the abs light stays on.

Please help me if you can and thank you my dad really needs this car and I am baffled.


Also a little before this I had an overheating problem I seem to have fixed that as when the car does run is cooling fine, I replaced the waterpump, thermostat, and flushed the cooling system.

Answer
Jeremy,
  WOW, you know more about this that I do. I could have just clicked that "I can't help with this" but I just wanted to give you some words of encouragement. I have NO idea what might be wrong. As stated in my Profile, I'm a Parts Professional, NOT a tech. Now let me look at your problems..
  The bottom line of your inquiry is about the location and wiring diagram for your vehicle. Not knowing what year the car is, I can't say if I have one or not but I can suggest you go to your local Public Library and look in the "Reference Section" to see if you can find that information. EVERY Public Library I have ever been in has such a section. IF they don't have the book you need, you can have it shipped in from the "Major Branch". You can't  check out these books but you can photocopy the information you need and take it home.
  In closing, one thing that bothers me is a traditional problem with a power brake system, the idle of the engine changes when you apply the brakes. This is a traditional vacuum leak. Obviously I can't tell you where, it could be a cracked hose, loose intake manifold or injection system. I'm not saying that is the problem since it makes NO sense to me. I'm grasping at straws but trying to give you a bit of direction to the Library.
 You can call me a Moron or and Idiot but just be gentle. I can't answer your question, I have told you that but have given you my best thoughts. Good luck to you and your father.
Skip