1985 Chevy S-10 Isn't Getting Fuel

Yes the FI wire goes directly to the ECM. Usually the wire to the ecm is NOT red or orange(that would be the 12v power side. The ECM should ground that wire(pulsing) to fire it. You should have 12V on both sides of the injector (one side if unplugged). While cranking the ECM should pulse one side to ground to fire it. You wont be able to see the pulse because it is so fast with a normal test light. You need a noid light or a led type test light to see the pulse. just crank it and check with the noid light or check both wires with a LED test light, one side should pulse. Your blowing out the screen to fix it doesnt sound logical. Check for pulse, then check for fuel pressure. It should probably have about 30 psi. If it has pulse AND pressure only then would I buy a new injector. You should also be able to hear the thing clicking if it pulses. Might be kinda of hard to hear while cranking cause of the starter noise though. Do yourself a favor and check ALL the fuses to :) GL

All of the fuses checkout good. I belive I am not getting the pulse at the injector. Do you know what would inhibit the ECM from sending the pulse?

Clint,

Check the wiring all the way to the ECM. I had one of my injectors quit spraying on my '95 C1500 and it turned out to be a frayed wire going to the ECM was shorting out.

Cheers, Kyle

---------------------- Did you accually check it with a noid light? If the tps isnt telling it it's at wide open throttle (clear flood mode) its the wiring or the ECM. (you said it runs when you dump some gas in the intake right?) Are you *sure* its not pulsing? Are you *sure* there is fuel pressure? Are you *sure* *all* the fuses are good?

I wonder if splicing those wires to the injectors after the small fire have anything to do with this problem...

I have not actually checked it with a noid light. I tried with a diode though, and saw nothing. I measured the TPS signal at the ECM and saw the voltage changing with the trottle peddle, so I don't think it is the connection to the TPS or the TPS. Yes, it will run if gas is dumped directly into the intake. I believe (not sure) it's not pulsing because I didn't see anyting the the diode I used, and because it seems to inject gas when the voltage is dropped, by disconnecting the battery, disconnecting the connector on the ignition coil, or disconnecting the 4 wire connector that runs behind the dristributer cap. I am sure there is fuel pressure, but not neccessarily the right pressure. I will see if I can get a pressure meter to check it properly. But, it does inject gas when the voltage is dropped as indicated above, so it appeared to have enough pressure. I checked all of the fuses, but will check them again.

I sure appreciate the help. Clint

Impedence mismatch or something? I can try clipping on the diode back where the original wires left off...

What do you mean "a diode"? Do you mean a light emitting diode?(LED) That will work but not by itself, the voltage with smoke it real fast. To test

12v with a LED it needs a 1k resistor in series with it, and it will only work in one polarity. See if you can borrow a noid light set from someone, maybe a parts house like Autozone? Or you can make a test light with a LED and a 1k resistor.

I checked all of the fuses again - all good, checked various parts (fuel pump runs, fuel pump relay works ok) Still have fuel pressure, but no firing signal coming from the ECM. There is 12 volts on both sides of the fue injector. The ECM is never grounding the one side to make the injector work. Checked with a make shift noid light. Grounding the one side of the injector manually does make it work. Does anyone have a wiring list for a 1985 Chevy S-10 2.5L? My Haynes book only shows the 1987 model which has different connectors on the ECM and different wire colors at the ECM. A useful wire listing could be helpful. Also if anyone knows what the ECM might see that would keep it from firing the injector, please let me know. I have tried another ECM with the same results.

Thanks, Cl>

Or just a 12vdc led... or a 12vdc bipolar color-changing led so he doesn't have to worry about polarity.

Clint, go to radioshack and steal....er buy a 12 volt LED. The long side is the cathode, which you want to attach to ground.

to injector. If so, the only thing I can think of that will *normaly* stop the pulse would be wide open throttle (tps shows high voltage 4 to 5v to the ECM. ) Try unplugging the tps on the throttle body and crank it. Do you have a "crank" fuse, does it have power while cranking the engine? Does it show 12v on BOTH injector wires when UNPLUGGED with a regular test light? It shouldn't. If it does you got a short on the ECM wire to a 12v source. (and probably smoked the ECM) You probably better buy a book with a wiring diagram too so you know for sure which wires at the ECM you are messing with. Go to a parts store there only about $15. You just need to know the pin # and the color for the injector wire (blue I think). You might be able to look in the book without buying it. Follow the wire from the injector to the 12v and the one to the ECM. You know the 12v one is good. Check the ECM one and take note of the color and pin # .GL Check that stuff and post back.

yep, that would be easier......

Let me see if I can address all of that.

1) The ECM is grounded on several lines. I don't know if all required grounds are there since the Haynes Repair Manual for the S-10 82-93 only gives the wiring list for the 1987 ECM which has different connectors and wire colors than 1985. 2) The TPS checks out good. It's less than a volt normally going up to 5 with the gas pedal pushed all the way in. I have also tried unplugging it with no change in results. 3) I don't think there is a "crank" fuse. The 12 volts stays on the Fuel Injector while cranking. 4) 12 volts is only on 1 line when unplugged, the red one. The blue one does not have any voltage when upplugged, and is about 2 ohms from ground. 5) The wire from the injector to the ECM shows continuity.

In addition. I pulled the injector control wire from ECM and hooked the noid light directly to the ECM, so if there were any shorts in the wire to anything else, they would be taken out of the loop. Still have all of the same behavior. No flashing light. Also still have the 2 ohms between the EMC control contact and ground. It seems to me if there isn't a sensor that would tell the ECM not to fire the injector, the only 2 things left would be a bad ECM, or a bad or missing ground to the ECM. (I have tried a different ECM before. Maybe I need to try another.) There are several pins at the ECM that are at the ground potential. but without a proper wiring diagram, I can't be sure all the required grounds are there. I will look further at getting a wire list for 1985.

Thanks for the assistance.

Replies are inline.......

-------It should be VERY similar. You probably ok there-----------notice I said probably

----------OK ,perfect its working correctly.

---------------OK, thats good

---------12v on the red is good, the blue with 2 ohms from ground is shorted to ground, unplug the ECM and check it again. If it still shows a short, it should be open, then fix the short to ground on the blue wire on the injector all the way to the ECM, (or run a new one)

----------Thats good but it still is shorted to ground if it shows 2 ohms. See above.

Your last paragraph makes perfect since. check the blue wire unplugged from the injector and the ECM for a short to ground or power. So you hooked up the noid light (LED?) please explain your light you are using)) directly at the ecm without the blue wire plugged into the ecm but every other wire plugged in and the other light lead to 12v? Does it light but no flash right? If thats the case and it is a LED you are using, the ECM isnt firing the injector. Before you get another ECM you had better make sure nothing is shorted to any of the ECM wires (you mentioned a fire) or you will smoke the new ECM. And check the resistance of the injector too. If it is shorted (too low of an ohms reading) it will cook the ECM too. Hopefully your book will give you an idea of what it should be. Ill look at my ECM diag for my truck and see if it is any help. There has to be a wire telling the ECM the truck is running, rpm ect. too. That could be it. But please check the above first.

OK, forgot about one thing. the ignition module. AFTER you make sure there are no shorts, try unplugging the timimg bypass, it is probably a tan wire with a black stripe. Its the one you unplug to set the timing. look at the sticker under the hood or in your book for its location. It has a plug on it just for setting the timing. If it runs without it plugged in replace the module. The module also sends a signal to the ECM called "distributor referance signal". If that isnt getting to the ecm then no injector pulse. GL

change the ignition module and call me in the morning.

ScribAbell ~Next patient please~

change the ignition module and call me in the morning.

ScribAbell ~Next patient please~ ========= ========= Group: alt.trucks.chevy Date: Sun, Oct 26, 2003, 8:08pm (CST+1) From: snipped-for-privacy@cs.cs (cs) wrote back......

Tried that a couple of months ago. ========= =========

good input + bad output = bad ecm

change the computer and call me in the morning.

Scrib Abell ~next patient please~ ======= =======

What's the chances you have had to change out the heater core?

Scrib Abell ~:~