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1994 S-10 Blazer, 4.3 TBI. This truck was running great for the last two years. Recently it started running rough. After reading postings in forums some of the issues seemed to be alike. I have replaced the plugs, plug wires, EGR valve,ignition module, fuel filter, fuel pump. The distributor cap is fine.
Symptoms were that the truck would stall when I would get off of the interstate (approx 40 mi to work). Initially it started right up then it would not start until after it cooled down. When I got home Friday from work it died in the garage and when I went to start it on Saturday it would not start at all. I could not hear the motor on the fuel pump so I did change it last night (Sunday) Still there is no sound from the pump. There are two relays located on the drivers side firewall. One has two green/white wires, one solid green and one pink. This one is the closest to the fender. The other one has an orange, gray, green/white and a black/white wire. I tried to test the lines as I was advised there should be a three second power surge to one of the wires, I guess this would of been to the fuel pump. There was no movement by the meter at all. I wanted ten seconds between each turn of the key. I checked all of the fuses but they all checked out ok.Not being a mechanic I called a friend of mine and he advised it sounded like it was the computer located under the dash on the passengers side? I tried to jump the data link to see what codes it gave me but unfortunately, and a complete separate issue, the digital dash has been out for some time.
Any advise you could give me to get my truck up and running would be fantastic.
I look forward to your response and apologize for the length of this problem.
Since this is the first time I have posted such a question in this type of forum, do you e-mail me with your response?
Answer -
Hello Ray,
There is a fuse for the fuel pump, and it may be in a holder clipped to the firewall, but it would be near the relay.
If the relays look exactly alike, swap them, cause they probably are identical.
The codes are flashed on the service engine light, not through the didgital part. Jump A and B.
http://www.autotap.com/codes.asp
http://www.troublecodes.net/GM/
Check out these two links. You may be able to jump power to the G terminal in the connector under the dash, but that would depend on what system you have, so check that out according to those links, the VIN#, etc.
You didn't mention if you checked for spark.
Good luck,
Van
I replaced both of the sensors and no change, I do however hear a clicking. I went and bought a GM Code Reader. I plugged it in and turned the key and the service engine soon light did not light up. Again, I heard a click. Could there be a short in the harness somewhere. Also, I looked near the relays and could not locate a fuse. Does it look like a fusable link (fuse is enclosed), is it acctually attached to the firewall? I will recheck all of the fuses under the dash again just to make sure they are all in good shape.
Answer -
Hi Ray,
The relay you found with the orange, gray, green/white, and black/white wire is the fuel pump relay.
The orange wire is from the fuse, which is the ECM fuse, #9 in the fuse block, 20Amp. It should be hot at all times.
The green/white wire is the relay control wire.
The black/white wire goes to ground.
The gray wire goes to the fuel pump.
Test that orange, and make sure it is hot.
There is a redundant system for the fuel pump also. It is an oil pressure switch, which closes when oil pressure reaches about 3PSI, and connects that same orange wire to that same gray wire, so weather the relay works or not, the circuit from the fuse to the fuel pump is complete whenever the engine is running. The pump runs all the time.
The problem here, though, is if the fuse is blown, or the orange wire is open, neither system can run the pump.
The same goes for the gray wire. If it is open near the tank, the pump can't run.
There is also a black wire coming from the gas tank/fuel pump assembly that goes to ground, and must be good, since the tank is plastic.
I would check the orange wire for power first.
Then check the gray wire for power just after the key is turned on.
I might even jump the orange to the gray to see if the pump will run.
I don't think you have a short...shorts blow fuses.
You may have an open, though. Wiggle all connectors. May even want to see if there happens to be fuel pressure, and you are just not hearing the pump run.
Stay after it.
Still didn't say if you checked for spark.
Another possible problem could be the ignition switch itself.
Van
The truck has no power at all at this time. There is 12V to the battery but no volts to any of the fuses at all. Do you know how I can trace the wiring from the battery to the fuse panel. There is a purple wife comming off of the starter but I do not know where it goes. Do I need to pull the fuse panel to see where the wiring comes into it? I have a feeling I will need to pull the dash completly out to get to it. Do you think I have a damanged wire somewhere in there?
Answer -
Hi Ray,
There is not power coming to the battery, the power comes from the battery.
You can follow the cables from place to place.
The positive cable goes to the starter, then a wire from the same stud goes to the fuse block, and on from there. You can actually use a test light to see each step.
BUT..you must also check the ground wire. it goes from the battery to the engine block, and also to the body of the vehicle. All the connections need to be clean and tight.
To start tracing, using a test light, connect the ground clip to the battery ground, and the other tip touch the batt +, then the starter stud, then at the fuse block, etc.
Then after you get some light ups, move the ground clip to the engine, and do the same tests again. Then move the ground clip to the firewall or fender, getting good contact, and test the same places again.
Keep doing it and you can isolate where the power isn't getting through. It could easily be the plug through the firewall where all the wires run.
The purple wire, by the way, is the one from the switch telling the starter to work, so it should only have power when the switch is in the crank position.
Good luck,
Van
Ok, I think I have it narrowed down. There are two red wires that come from the alternator that go to the fuse panel via the firewall on the drivers side. They go in where the relays (fuel pump relay) are also located. They are connected, by what appears to be a clip. The wires do show volts up to this point by the way. There also appreas to be a little corrision on the wires. If I find these wires on the inside of the truck and if they do not show volts how to I repair them ? Do all of these wires that are going in run straight thru and the clip is there for stability reasons only or does it come apart? The clip is bolted to the firewall by one bolt. Also I noticed that located in the actual fuse panel there are two, what apprear to be fuses, two fuses labled "shunt", can you tell me what these are for? Could this problem, initially have caused the truck to start running bad or is this just another problem that came about? Hopefully once I get power back to the fuses it will start with all of the other additions I made, ie: fuel filter, fuel pump, ignition module, and relays. Any finally, one more question. When I replaced the ignition module I noticed that there were two wires coming from the distributor that had bare spots in the wires, in order to have fixed them I would of had to pull the distributor completly out and since I figured they were like that origionally I did not fix them, do I need to correct that, could that of been the spark that initiated the whole thing?
I have really appreciated all of your advice, I am sure it has saved me several dollars at the repair shop. I look forward to your reply and, no offense, I hope this is the last time I have to send you a question(s).
Thanks again.
Answer -
Hi Ray,
That place at the firewall...everything goes through the firewall there, and it is a connector. It unplugs, and is a good place to find a problem like that. Especially if there is corrosion there.
I have several times taken that apart, and found a very corroded connection. What I did was find the wires that were bad connections, and remove them from the connector.
I would cut them, feed good wire through the hole where the bad connection was, and butt splice the replacement wires, after reconnecting the block with all the good connections.
The red ones are probably big wires, and carry the main power, in both directions...to the ignition switch, and back out to the engine compartment. Just mark the wires, and make sure you connect the correct ones to each other.
As for the wires stripped bare, could a mouse have chewed the insulation off? I have tons of that problem. See if you can stick dome tape around the bare wires, and keep them from touching ground, or each other.
I don't know what the shunts are for...usually shunt means jumper.
Good luck,
Van
The bare wires I saw were under the distributor cap, I will see if I can get some tape around them. I have been all up under the dash and can not locate where the wires come in from the outside. Do they plug directly to the fuse panel? Does the fuse panel come off of the inside firewall?
AnswerThe bare wires, if they are inside the distributor cap, may be normal. As long as they don't touch each other, and don't touch any metal, you may leave them alone.
The wires coming through the firewall sure could go directly to the back of the fuse block. Take the plug off under the hood, and if you need to get to them under the dash, the fuse block will come out of there.
Van
