73-87chevytrucks.com
73-87 Chevy _ GMC Trucks => Performance => Topic started by: team39763 on November 26, 2009, 05:09:55 pm
-
I wanted to get a tune for my 94 Dually, but most people that I talked to told me there would be tons of problems trying to get it right with the mail-order tunes + it was a hassle to change the chip over and over. I had looked into the FlashMemory thing, but I didn't feel like it was worth it unless I had I really nice motor that just happened to be TBI.
The TBI system on my 94 S10 has gone crazy and I'm tired of trying to figure out what it wants. All that TBI stuff is being ripped out right now and going in the garbage. I couldn't figure it out for nothin' and nobody seemed to know anything about TBI systems around here. I know they're supposed to be super simple, but it's just not working out that way for me. I haven't met one person who could figure out these TBI systems...atleast not in my area. I agree with a bunch of others "TBI is the Devil".
-
Why didn't you ask on here for help? TBI isn't the devil.
-
I posted up in a few S10 forums, but none of the advice seemed to help. It was all good advice, but for some reason the system just won't work. Myself and several people agreed what should be the problem, but the truck still wouldn't start. We want the truck running ASAP, but we don't want to spend tons of money on stuff just to end up being wrong(atleast not at this time). Ok, maybe TBI isn't the devil, but it sure does make me say a lot of 4-letter words.
-
Care to elaborate on the problem?
-
The injectors won't fire. I got fuel pressure, I got spark, the distributor and wires are new. All wires going to the computer seem fine. At first the truck would just randomly stall with no warning and no indication of what was wrong. We would just start it back up and go on. Then it started stalling more frequently and developed a random misfire and the check engine light would flash. Then the misfire became a lot more frequent so I told my brother to stop driving it. The last times we tried to start it(didn't start though), the injectors were firing, we had spark at the two wires we tested. My neighbor told me to change the fuel filter first because it's an old truck - 217,000 miles. I did that and the injectors stopped spraying. That was the only thing I touched at that point. I swapped out the injectors for some known good ones and a new regulator, I swapped the coil, I inspected the module and rotor. All seemed fine and clean. We tried to manually fire the injectors, but that didn't work(I must have been doing that wrong).
I can get the truck to run by pouring gas down the throttlebody, but that's about it. I asked a few mechanics in my town and the next town and all say put a scanner on it. That doesn't work because the diagnostic port is unresponsive. Other than that, they say throw parts at it(dizzy,coil,injectors,pump,regulator,computer,new TBI,IAC,CTS,MAP) or swap it out for CPI. The guys online mostly said the pick-up coil or the module.
-
Disconnect the injector connectors. Key on, engine off take a test light to ground to the injector connector. Verify B+ at one terminal of each injector connector.
-
Scanner doesn't work? I might be suspicious that the computer may be at fault. A junkyard computer would probably be fine. If you have spark but no injector pulses either the "trigger" signal isn't getting to the computer or the computer itself is at fault. If you could get a schematic of the computer and check for power / proper signals at a few points it may get you started. I believe the ignition system is a more or less seperate entity from the computer. Do you have a 5V reference power on the coolant temperature sensor, or TPS? Does the check engine light light up when you turn the key on?
-
The check engine light doesn't come on anymore when I turn the key on and it won't flash with the scanner. I'll see what I can find as far as schematics...I had a haynes manual, but I don't know if that'll have it. I don't have any way to check for 5v power, all I have is a test light. Vile I'll give that a try, I just need to put back a few parts that I removed over the last few days.
Thanks for starting this thread for me. I appreciate the help.
-
Let us know what happens
-
We have B+ at one side of the connector.
I'm gonna try to figure out what's wrong with the data port. From what I've been reading, it's usually the cigarette lighter fuse that kills the data port.
-
It does have good fuel pressure for sure? I have come across a few that the rubber hose between the fuel pump and sending unit has a split in it causing low fuel pressure.
-
I'll check the fuel pressure again. We had checked it before the truck completely stopped running.
-
OK now go to the other terminal that didn't have B+ with your test light connected to B+, habe an assistant crank the engine. The test light should flash.
-
While I was gone I had my friend to run the test you suggested Vile. He said it didn't flash. So when I got back I changed the ignition module like some others told me to do. Now it won't start at all even with gas poured down the throttlebody. I'm sure I put everything back the way I found it.
I'm in a bit of a slump right now. I don't have anymore money for repairs and 2 of my 3 trucks are broke down. With the way my wife is, our 3rd truck will be broke down soon also. If it comes to it, I'll let her drive my race truck to work, but that won't be pretty since the seat is too small/narrow for her. I do have a 4th truck, but I don't have a title for it and it needs another starter which I'll probably get from my dually when my wife breaks it. I'm gonna go play with my race truck and try to cheer myself up. Thanks for all the help guys.
-
Verify the test yourself. B+ on one side, B- on the other side while cranking.
-
Ok, I'll give it another shot. It would really make my wife happy if I got this truck running. I'll post up what I find.
-
I verified B+ on one side and other side was unresponsive. I also had a problem seating the distributor in the motor. Like the gears didn't want to seat except in one position, anything other than that and it would sit about 1/4" out of the hole. So I just stuck it in there. I'm no longer getting spark after swapping in the new ignition module. I triple checked to make sure I put everything back where I found it and I can't see anything I did wrong. I may try putting the old module back in there.
-
OK, install the distributor correctly and on time. You need to engage the oil pump driveshaft and the distributor should essentially drop right in. You may need to bump the engine a little bit to get them to engage. Once you verify it make sure the rotor is turning when you crank it.
-
Vile, I got the distributor in correctly, but it still won't fire the injectors. I also found out one of the sparkplugs was partially out. I checked the injector plug/harness again and verified it was getting B+, but the other side was not getting B-. I tried to manually fire the injectors, but they didn't do it. I'm guessing my fuel pressure is too low for them to fire? I lost my fuel pressure fittings, so I can't check the pressure right now.
My wife offered to get a loan to buy some parts, but we have to for sure take care of the problem. It'll really suck to spend $300 and still not be able to drive the truck. Here's what I plan to buy: new distributor, new coil, new fuel pump, new computer, new injectors, new regulator. Should that cover anything that might be keeping it from running?
-
It's not fuel pressure... ok now that you've verified B+ to the injectors but they are not commanding on, disconnect the 4 way connector at the distributor. Key on engine off- take your test light to B+ (touch B-to verify your light) and tickle the purple/white wire (cavity C) at the distributor harness. This should energize the injectors. -Report
-
I typed this while vile replied - here is some other stuff to maybe help I hope, since it is so close to Christmas...
So you have spark but it's still not firing the injectors? I wouldn't go throwing parts at it. Perhaps a good place to start would be an alldata subscription that you give you some good schematics to locate splices and common grounds, and some diagnostic stuff.
You could hook up a test light to the injector connectors or even buy a set of noid lights to see if the computer is firing them. Where the check engine light is not coming on and you aren't getting codes by jumping the aldl, I'd verify the bulb in the dash is OK, the connectors on the computer is OK, and all grounds are good. The schematics would tell you which wire to check for on the computer connector to see if you are getting the ignition pulse that tells the computer the rpm.
If you pull the line off the throttle body and put it in a can or something similar, do you get gas for a second or two? If you crank it for 15 seconds or more will you get gas? The computer will prime the pump for around two seconds and stop when you turn the key to on to pressurise the system, and I know some other GM products will start the fuel pump after cranking for a number of seconds (as far as I can tell there was a oil pressure switch that would put power to the pump once it closed. could your supply and return lines be reversed, or the wires on the pump be reversed?
Hope this helps.
-
It's not fuel pressure... ok now that you've verified B+ to the injectors but they are not commanding on, disconnect the 4 way connector at the distributor. Key on engine off- take your test light to B+ (touch B-to verify your light) and tickle the purple/white wire (cavity C) at the distributor harness. This should energize the injectors. -Report
We checked that purple wire and the rest of them with B+ and none of them did anything. We did finally get B+ and B- on the injectors, but they still didn't fire.
Marc, I connected 12v to the pump to make it turn on. They key doesn't do anything for the pump. Right now I'm working on getting the distributor set correctly. I think we had it 180* off, but we're not sure...can't get a finger in the hole to check for tdc.
-
That doesn't make any sense. You tickled the terminal with B+ connected to your test light to cavity C and got no injector pulse? But now you have injector pulse but the injectors are not firing? So what are you saying? They are comanding on but no fuel is spraying out of them?
-
No, they aren't getting commanding on. The purple wire just doesn't do anything when B+ is added to it. There's no B- at the injector connector still. We grounded one side of the injector and added B+ to the other side and it lit up the light but didn't fire. It didn't light up before. We got the distributor in correctly and have turned the truck on with carb cleaner. The injectors just won't fire. I noticed that these injectors can't be manually fired. I tried the ones on my neighbors running TBI truck and we couldn't make his fire either.
What should I look at next?
-
If you do not have a noid light, disconnect one injector connector. Take a test light and install it across one injector connector so the probe end touches one terminal and the alligator clip end makes contact with the other end. Key on engine off take another test light connected to B+ (touch ground to verify your light) and tickle cavity c of the 4 way harness connector with the test light. this should make the test light installed in series blink. If it does not blink Trace the wire from Cavity C back to the pcm for an open or short. -Report
-
We did that test and nothing showed up. We found the wire at the pcm, but it was too hard to access the wire behind the motor(the local mechanic suggested removing the motor was the easiest way to get to it). I also checked to see if the pcm was grounded and it was. What should I do next? Can I just splice in some new wire for that purple/white one and connect it to the correct pin on the PCM?
-
Nothing showed up as in what? Infinite resistance?
-
Whoops, forgot to turn the key on. I'll try it again.
-
Vile, thanks for your help man. I really appreciate it, but this is just not working out for me. I did the test that you said and I'm guessing the wire is broken somewhere, but there's no way to find it. There's about 4 different wires of the same color and they are all tied into the same clump of wires tucked behind the motor aswell as being tied under the truck under the truck and routed all crazy. We attempted to trace the wires, but it requires removal of the motor just to get see them. I started taking it apart, but I'm just tired of it. We removed the TBI system and were thinking of converting the motor to carburetor, but There's so many wires going in so many directions that the truck may not even be functional anymore.
I don't understand why GM didn't just make things simpler. Why 4 purple wires with white stripes, 2 solid purple, 3 pink with black stripes, 4 white, 3 black? It was just frustrating along with the fact that most of them could barely be touched without removing the motor and front fenders/hood. And there's so many wires...I don't know what to do with this truck now. As it sits, it's probably only good as a parts truck.
-
You're giving up too easily. All you had to do next was a pinout test from the connector back to the ECM.
-
I tried that, but I must have done something wrong there too. We never could get 12v to show up on the other side of the wire. I put 12v to the connector - nothing, I put 12v to the ECM connector - nothing. Something was wrong somewhere and the truck was going to need to be completely dismantled just to trace the wire. I figure I may aswell just make it super simple and throw a carb on it.
Yeah, I know I give up too easily. This problem has been kicking my butt for a while now and I've thrown a few parts and some money at it and I'm nowhere near getting it running. Atleast with a carb it should be as simple as drop the distributor in, check the fuel pressure and go.
-
you aren't supposed to put 12v to it. you were supposed to take a test light connected to B+ and momentarily touch and release this terminal. When you do this it will energize the injector for a split second.
-
Well I've already screwed myself at this point. After pulling the truck apart, we found a few burnt wires and noticed a few bent connectors. After realizing that I could trace the wires without removing the engine and other stuff, I decided to put it back together and concetrate on my own project. My wife is gonna just buy a newer vehicle to drive to work. I'll get another shot at a TBI system soon...my dually is gonna need some attention next.
A neighbor of mine is pulling a carbureted 4.3L out of his truck and he told me I could have it if I help him remove it. I'm just gonna throw that carbed motor in the bed of the S10 and see if I can trade the whole project for whatever.
-
you aren't supposed to put 12v to it. you were supposed to take a test light connected to B+ and momentarily touch and release this terminal. When you do this it will energize the injector for a split second.
I thought B+ was a term for battery voltage and I could get it by connecting directly to the battery. Could you tell me the difference please? That way I'll know next time.
-
B+ is battery positive. B- is Battery Negative. Your test light should be connected to the B+ terminal during the last step I asked you to do. Connect the alligator to B+ and touch ground to verify the light comes on. Then perform the steps as described. If you just took B+ to the terminal which is what you said you did, you missed the part where I said to use a test light. In other words you said you put 12v to the terminal. This would indicate to me you took a jumper wire and put 12v to the terminal. The test light bulb will act as a resistor and will excite the circuit during the test.
-
Ok I understand now. I only had one test light and I honestly thought that a piece of wire connected to the battery was all the same. Next time I'll just ask if I'm not 100% sure.