Ghost in the machine?

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  #1  
Old 07-05-06, 11:53 AM
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Ghost in the machine?

Have a 1991 Dodge E250 van with a 318 throttle body injection. Starts every morning. after that it is hit or miss, more miss. Fuel is getting to the injectors, but not going into the throttle body. Like the injectors aren't opening. Have changed the fuel pressure sensor, MAP sensor, and the injectors. Did check the injector electrical connectors with a digital multi meter, reading was fine. Also had it hooked up to a dealers computer. It read that the map sensor was bad,hence the new MAP sensor

Steve
 
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  #2  
Old 07-05-06, 11:55 AM
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monitor your fuel pressure when it is not starting if your not getting fuel out.
 
  #3  
Old 07-05-06, 04:16 PM
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One time when it wouldn't start I pulled the feed fuel line, and turned the key. fuel was coming out in a steady stream. Did the same with the return line. results were the same.
 
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Old 07-05-06, 04:18 PM
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Did the stream look around 15psi

Can you feel the injectors popping if you have your fingers on them when cranking
 
  #5  
Old 07-05-06, 04:25 PM
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Yes,once it starts.
 
  #6  
Old 07-05-06, 04:29 PM
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bad coil !. when it's not started, do you have sparks?.
 
  #7  
Old 07-05-06, 04:34 PM
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He said he has no fuel spraying in, he has to feel the injector for popping or listen with a mechanics stethoscope/ really long screw driver when the no start happens. Then he will know if he has no fuel or incorrect pressure when the no start happens

Its intermittent so he has to test when the problem is happening or else he will never get usable results.
 
  #8  
Old 07-05-06, 06:28 PM
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When trying to start, but it won't. There is spark. there is low voltage power to the injectors, and fuel is getting to the injectors, but not coming out the ends into the throttle body. I have pulled the injectors when it wouldn't start. There is fuel pressure when I pop the injector out. Fuel sprays. But now that I think of it there does seem to be more pressure in the right injector than the left.
None of this started happening till after I did a tune-up.
 
  #9  
Old 07-05-06, 06:40 PM
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Forget the tune up that is coincidence. How are you measuring voltage to the injector do you have an oscilloscope, because a multimeter of anykind will not give you a correct reading when cranking.

That is a PWM signal and the multimeter will only read DC constant voltage correctly. So you will have a low reading with a multimeter.
 
  #10  
Old 07-05-06, 06:45 PM
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You need to try a noid light, those will kinda put a load on when cranking, but an oscilloscope would be best so you can see if the injectors are getting the correct signal.

One test you can do while it won't crank is leave the key on measure the voltage of the injector and see it is 12Vdc after you encounter your no start situation.

Could be bad injectors, maybe even bad drivers in the pcm. You probably need it thrown on a sun machine and have everything monitored to find the problem
you most likely need injectors if the driver in the pcm(mosfets) is fine and signal is there and fuel pressure is there.

Assuming this happens only on hot starts would also exhibit an electrical problem.

Put your hand on the TBI injectors and fuel for the tick or pop each time they are triggered let us know if they do when the no start is happening
 
  #11  
Old 07-05-06, 06:46 PM
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When it won't start/run..have you put a noid light on the injector wiring harness to see if it's getting a pulse? You said it didn't do any of this prior to you giving the vehicle a tuneup. What exactly did you do as part of your tuneup?
 
  #12  
Old 07-06-06, 05:47 PM
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Tune-up consisted of changing the plugs, dist. cap, rotor, & plug wires. Also an air filter.
Have not tried a noid light. Something different happened today. I was trying to check the code with the check engine light. Turned the ignition on, & off as was described in the Hayes manual. Light would not blink, but when the key was turned to start right after words the engine started. It has started everytime that sequence is followed. Idle speed sensor maybe?
Did also change the PVC valve.
 
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