1993 GMC C1500

Tiny
FREEMAN_20071
  • MEMBER
  • 1993 GMC C1500
  • 6 CYL
  • 2WD
  • MANUAL
  • 89,000 MILES
The truck cranks up idles for about ten seconds then dies. After about thirty minutes of cranking on the truck it will finally run and it runs great. What could my problem be? It is throttle body is getting 13 psi at the back of the throttle body. An it is still getting fuel even when it dies. I have replaced pickup coil, igniton starter switch, coil, spark plugs, plug wires, distributor, rotary button, thermostat, tps, idle air control, egr, computer, icm, intake gasket. Thats all I can think of right now. An the intake gasket is not leaking. PLEASE help me I need my truck running.
Monday, October 4th, 2010 AT 1:11 PM

15 Replies

Tiny
JDL
  • MECHANIC
  • 16,098 POSTS
When the problem occurs, you can see an injector spray pattern? Any applicable trouble codes?
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Monday, October 4th, 2010 AT 1:19 PM
Tiny
FREEMAN_20071
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Yes and the check engine light has now went off cause it was bringing up a code saying it was running rich but that was from the Fuel pressure regulator inside the throttle body. My friend thinks it may have jumped time on the timing chain. If so would the truck run so good when I finally get it to crank up? I appreciate your help so much.
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Tuesday, October 5th, 2010 AT 5:04 PM
Tiny
JDL
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From your post, I didn't think it would stay running? I don't know.
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Tuesday, October 5th, 2010 AT 8:13 PM
Tiny
FREEMAN_20071
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It does run but when the motor is cold and you crank it it idles for about half a minute then dies. Next time u crank it it idles less than that then dies. As you crank on it it gets worse and worse but after about thirty minutes of cranking on it it will finally crank up and run. I do not know what else to try. Thank you for all your help so far and hopefully you can continue to help me.
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Wednesday, October 6th, 2010 AT 8:01 AM
Tiny
JDL
  • MECHANIC
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I'd want to check if the system is rich or lean. You might be able to tap the o2 signal wire. The purple wire is the signal, use a digital multimeter. You might be able to use jumper wires to hook everything up, take the read off the jumper.
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Wednesday, October 6th, 2010 AT 8:57 AM
Tiny
FREEMAN_20071
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And can you explain to me in a little more detail how I would do that? An when the check engine light was checked it was running rich and I could smell it and tell it was running rich but now it smells normal. Since the fuel pressure regulator has been changed.
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Wednesday, October 6th, 2010 AT 9:12 AM
Tiny
JDL
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You could use a straight pin in the purple wire for 02 sensor. Engine cranking, take reading off pin with digital multimeter. Or you could take the connector loose and jumper wires in between connector and 02 sensor, that way you wouldn't have to make a hole in the sensor wire. If you do make a hole, cover it up, clear finger nail polish or super glue, something. Right at the moment, I don't know what is wrong? There is more than 1 type of 02 sensor, if it is the type I'm thinking about, that should work.
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Wednesday, October 6th, 2010 AT 1:08 PM
Tiny
FREEMAN_20071
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So I have one side of the DMM on the o2 sensor purple wire and where else should I have the other? An what am I looking for? I know voltage but what is good and what is bad?
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Wednesday, October 6th, 2010 AT 1:27 PM
Tiny
JDL
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The ground goes to chassis ground, metal part of frame or engine. Use the milivolt setting. Below.450 is lean, above is rich. If just a point or so one way or the other, I don't pay any attention to that.
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Wednesday, October 6th, 2010 AT 1:49 PM
Tiny
JDL
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I may have steered you wrong, if there is a bias voltage, that may not work. The last truck I worked on close to your model year, I used a scanner that showed live engine data. For the o2 sensor the scanner showed.250. Then I used a fuel pressure gage, the vehicle had a faulty fuel pump.
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Wednesday, October 6th, 2010 AT 1:59 PM
Tiny
FREEMAN_20071
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So the DMM will not work? Cause that is about all I have. I have checked fuel pressure and I am getting 14 or 13 psi where in the haynes manual mine calls for 9-13psi.
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Wednesday, October 6th, 2010 AT 2:39 PM
Tiny
JDL
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Is that a single wire 02 sensor? Try it anyway, won't hurt anything as far as I know. If you want to talk to somebody else and get a fresh point of view, that's ok.

You can fool the computer to think rich or lean, then see if it makes any difference. You can take the 02 sensor connector loose, if you need to, use a jumper for the purple wire that goes to the computer side of connector, hold one end of bare wire in your hand, with the other hand touch the positive battery post, engine cranking, see if it makes any difference. Then touch the negative battery post, try again, any difference? Just speaking for myself, it's hard to diagnose these issues over the internet.
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Wednesday, October 6th, 2010 AT 3:17 PM
Tiny
FREEMAN_20071
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Yeah im just really trying everything to try and figure out what is wrong with my truck. I really do appreciate you trying to help if you can think of anything else it can be please let me know.
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Wednesday, October 6th, 2010 AT 3:58 PM
Tiny
JDL
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I understand what your going through. Without something to point us in the right direction, all I can do is hunt and peck.
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Wednesday, October 6th, 2010 AT 4:07 PM
Tiny
FREEMAN_20071
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Well it has been at the bottom of a lake the idoit befor me decided to put emergency brake down and it rolled off in the lake but I have replaced pretty much everything electrical and the motor and all has supposedly been cleaned out.
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Wednesday, October 6th, 2010 AT 4:17 PM

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