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Fuel, spark, good injectors. Wont start (runs with carb cleaner)

Tiny
BUS933S
  • MEMBER
  • 1992 OLDSMOBILE CUTLASS
  • 330,000 MILES
GM 3.1. Was running, shut off went shopping come back out cranks no start. Has good spark, full tank and 42 lbs fuel at schrader valve, can hear pump at key on. Noid light in 1 plug showed no light key on, no light when cranking. Pulled plenum ohm'd all injectors are between 1.5-2 ohms. What else to check and how?
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Sunday, July 29th, 2012 AT 8:51 PM

65 Replies

Tiny
SATURNTECH9
  • MECHANIC
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So do you have power to the injector wire that is supposed to have power at the injectors with the key in the run position?
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Sunday, July 29th, 2012 AT 8:57 PM
Tiny
BUS933S
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With all injectors disconnected and key on, there is 2-3v on one side of each connector. As soon as I connect ANY 1 injector back to its connector, there is no power at any remaining open connector.
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Sunday, July 29th, 2012 AT 10:11 PM
Tiny
SATURNTECH9
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Alright theres the problem the pink wire with a black stripe should have battery voltage with the key in the run position. Its power from the inj fuse.
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Sunday, July 29th, 2012 AT 10:22 PM
Tiny
BUS933S
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I am amazed how quickly I received a response - this forum is great! Thank you.

So do you mean there is a short between the fuse and the injectors? Would this include possibly the injector control module? I am somewhat confused - I thought the injector connection should read battery voltage only when the pulse signal is sent.
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Sunday, July 29th, 2012 AT 10:31 PM
Tiny
SATURNTECH9
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No here is how it works you get battery voltage from the inj fuse on the pink wires with a black stripe. That power comes straight from fuse. The injector is plused and control by the ground side of the injector circuit. That would be the light blue wires going to the injectors. Then those wires change to a dark blue color and go back to the ecm/electronic control module. That is what controls the injector pluse. Lets start by seeing what the voltage is at the inj fuse in the fuse box with the key in the run position?Also make sure the battery is fully charged. Check both sides of the fuse. It could be a crossion in the fuse box causing a bad connection even.
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Sunday, July 29th, 2012 AT 10:58 PM
Tiny
BUS933S
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12v at battery, no reading at injector fuse. Fuse block in general is getting power (i.E. Fuel pump fuse reads 12v). I do have all the injector connectors and connectors that attach to anything related to the plenum detached, as I pulled the plenum. Do these need reconnected to get a reading?
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Wednesday, August 1st, 2012 AT 12:59 AM
Tiny
BUS933S
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Take that back. About.5v at the fuse (I didn't have a good ground on the tester 1st time).
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Wednesday, August 1st, 2012 AT 1:09 AM
Tiny
SATURNTECH9
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Then your problem is at the fuse box then. Was that 5 volts at the fuse?
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Wednesday, August 1st, 2012 AT 3:09 AM
Tiny
BUS933S
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In the group of the small 2 prong fuses, where 2 are labeled something to do with injectors, there is only 0.5v on both sides of each fuse. In the other half of the fuse box, where there are larger 5 prong fuses, such as for the fuel pump, there is 12v.
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Wednesday, August 1st, 2012 AT 11:59 AM
Tiny
MIKEDEROUIN88
  • MEMBER
  • 137 POSTS
Also check your crank shaft sensor conecter. That crank shaft sensor controls the pulse to your injecters. And it is common on the 3.1, 3.4, & 3.8 for the conecter to be bad. You can but it at any local part store. Part # PT5666.
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Wednesday, August 1st, 2012 AT 12:37 PM
Tiny
BUS933S
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I've heard there are 2 sensors. Is this the one on the back of the motor by the firewall, or the one behind the crank pully?
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Wednesday, August 1st, 2012 AT 1:06 PM
Tiny
SATURNTECH9
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Heres the problem with that theroy the injectors are controled by the ground side of the injector circuit thru the ecm. So no matter what you should still have 12 volts to the wires I told you with the key in the run position. With the 5 pins those are relays not fuses.
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Wednesday, August 1st, 2012 AT 4:45 PM
Tiny
SATURNTECH9
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Also bad crankshaft sensor no spark they have spark.
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Wednesday, August 1st, 2012 AT 4:50 PM
Tiny
SATURNTECH9
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Shpould be fuse number 7 in the diagram in the passenger side under hood fuse box. When you think you found the correct fuse pull the fuse out and see if there is no voltage going to the injectors anymore. That way you will know you found the correct fuse.I also posted part of the wire diagram so you can see how the battery voltage runs from the fuse to the injectors.
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Wednesday, August 1st, 2012 AT 5:11 PM
Tiny
BUS933S
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I started by reconnecting all the electrical connectors I had pulled to remove the plenum. Now the only things disconnected are all injectors. Now I have 12v at the injector fuse. I have 2.5 volts at every injector connector UNLESS I plug any 1 injector connector back in, then the remaining injector connectors have 0v. Thank you for the all the help - this one really has me stumped!
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Sunday, August 5th, 2012 AT 3:17 PM
Tiny
SATURNTECH9
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Your going to have to start out by seeing if there is 12 volts coming out of the fuse box. If not the problem is somewhere in the fuse box area. Open terminal loose connection etc.
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Sunday, August 5th, 2012 AT 4:47 PM
Tiny
BUS933S
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1. I HAD 12v at the fuse, but upon disconnecting then reconnecting the wiring harness (2 connectors) I have between 0v and 0.5v at the fuse. This leads me to believe there is a bad connector.
2. HOWEVER, regardless of the above, I have 12v on the pink/black wire coming out of the harness connector that runs directly to the injectors (the same connector I've been messing with that seems to have affected the fuse voltage).
3. At the injector, still about 2.5v and 0v if any one of them is plugged in.
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Sunday, August 5th, 2012 AT 6:18 PM
Tiny
BUS933S
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Oh, and I took an ohmmeter and checked for continuity between the pink/black wire end of the harness (male connector) and each injector at the power side. It was good at each one.
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Sunday, August 5th, 2012 AT 7:51 PM
Tiny
SATURNTECH9
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That really makes no sense because as you can see the power wire to the fuel injectors gets its power thru the fuse and then too the unjectors. Look at the wire diagram I posted you see where the power wires split off from the main power feed wire?I would find that connection point and see what you can find for power there?It could be all corroded up or loose etc?
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Sunday, August 5th, 2012 AT 8:20 PM
Tiny
BUS933S
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I know I am looking for 12v to flow to the pink/black side of each connector and will chase that wire. But I am confused why it drops from 2.5v to 0v when any 1 connector is plugged in. Are there 2 problems here? Also, what is the black box on the fender well right next to the fuse box, approx 4x6 inches with 2 large harness connectors going in? Is that involved in this circuit?
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Sunday, August 5th, 2012 AT 8:47 PM

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