Thread: Ground issues

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Hey guys. I'm new to the forum... Thought you guys may be able to help me out a bit... I've got a 1994 S-10 with the 4.3 TBI V-6. I'm sure you guys are more familiar with the older vehicles so I'm not asking for in depth info here, just a few pointers.
OK, I think my problem lies in a ground problem. I've got something that keeps slowly frying computers. Basically I'm not getting a signal to my injecters. I tried a used computer out of a '93 Blazer with the chip from my truck and it ran fine for almost a week until it did the same thing. Maybe you guys can lend a bit of support here. My questions I guess circle around, where to ground, what to ground, and what to use to ground for the best circulation? Is there place in paticular I should be looking at for a bad ground that would affect my injecters?
Thanks for your help...

Suggest getting a real shop manual and look at the wiring diagrams.

Your computer does not supply 12 volts to the injectors, it "sinks" them to ground. Has anything been touched before it started, like the computer disconnected/reconnected, something added/removed under the dash, some other seemingly unrelated problem happening, etc.

If the computer had been disconnected, look at the plug to see if one of the receptacles had been pushed out of the shell or if a wire seems broken. It is hard to tell with the backshell on the connector. For any computer, look at the pins and see if one is bent.....unless you have had the connector off, pins dont bend. If a pin is bent more than about a pin diameter, the odds of straightening it reliabliy are slim.

Again, a factory manual should help guide you.

mike

Originally posted by Fonzy
Hey guys. I'm new to the forum... Thought you guys may be able to help me out a bit... I've got a 1994 S-10 with the 4.3 TBI V-6. I'm sure you guys are more familiar with the older vehicles so I'm not asking for in depth info here, just a few pointers.
OK, I think my problem lies in a ground problem. I've got something that keeps slowly frying computers. Basically I'm not getting a signal to my injecters. I tried a used computer out of a '93 Blazer with the chip from my truck and it ran fine for almost a week until it did the same thing. Maybe you guys can lend a bit of support here. My questions I guess circle around, where to ground, what to ground, and what to use to ground for the best circulation? Is there place in paticular I should be looking at for a bad ground that would affect my injecters?
Thanks for your help...

the first thing i need to know, have you checked for codes? do you have spark at the plug wire, do you have fuel pressure and can you hear the inj. click when you turn the motor over. should be ale to fix that problem without guessing what it is. but you got to check a few things.

ps- check all of your fuses.

I can't think of anything that I did to it before this started happening. I do have a B&M shift improver that is hooked to the computer harness but it's been there for almost 3 years now. I haven't had any problems that I can think of, the latest work I had done to it was a water pump last year in October I think it was. Here's some background that may help. One Saturday my girlfriend and I were driving around for a few hours,(we did drive on a rock orad for a bit, could have knocked something loose) when we returned home, the truck sat for about 2 hours and when we went to start it up again, it wouldn't... Turns over fine, all that good stuff but found that it wasn't spitting fuel. So we checked the fuel filter, which had horrible flow and replaced it, still nothing. The fuel pump was kicking on and we had checked the fuel pressure and I was getting plenty. Sunday afternoon, I ended up replacing the fuel pressure regulator. After that was done, it fired right up and ran great. Sunday evening I drove it around for a bit and it ran perfect, it ran better than when I bought it... Got it home, parked it, hosed it off a bit and tried to start it and it wouldn't start... I tested the injecters for signal and they wern't getting any. The next morning I went out and if started right up. Narrowed it down to only happening when it got hot. After several frequent visits to mys10.com which I'm a member, we came up with the idea that maybe my computer was going bad. So that weekend I went to a somewhat local junkyard and pulled a computer out of a '93 Blazer with the same engine as mine. As you know, it worked untill this past Friday and it just wouldn't start. I have a new computer sitting on the kitchen table but I don't want to throw away that one to... I figure there has to be something causing the computer to go bad unless I just got real unlucky both times... Could the chip have an issue that would cause this problem? I've got a new one on the wasy, won't be here till Thursday or so but I wanted to figure this out before I put the new parts in... THnaks for your responce!

Sorry lt1, I was replying when you posted. OK, I have enough fuel pressure for sure. With the code reader that i have (isn't the best but has served well in the past) I have no codes... I know I have spark because I can go out right now and put a bit of gas in the intake and it will fire right up. Hell, I can go put my new computer in it and it will fire right up, I'm just not sure for how long... All the fuses are ok, I've had this problem three different times now without doing anything execpt for changeing the computer.
As for the injecter click, I'm not sure. They have a constant power to them and but don't seem to get the signal to acually pump the fuel.

Ok, thats funny... God must love playing tricks on me over the last few weeks. Per the advice of Robot, I went to look at the pins in the used computer I had in it. Now this still doesn't make much sence why it would keep it from starting when it got hot but I had a bent pin. I bent it back and pluged it back in and it fired right up. Now, I'm going to go run it for a bit and come back, shut it off and try to restart it. We'll see what happens...
That bent pin doesn't make sence though. If it was bent this whole time... Wait, I bet it got bent at 3 am on Friday when I was so angry at it in the first place and only running on a few hours of sleep, I bet I forced it in just right and bent it. That doesn't explain why it wouldn't start Friday morning though... Really confuseing if you ask me... Any ideas guys? lol

next stupid question is: Do computers make noise when your vehicle is running??? lol... Well, I've got what sounds like alternator whine in my computer. It's got a real fast tick type noise to it that increases as the rpm increases. I don't think this is normal is it? So far everything works great. Still seams a bit off when it runs though. I've got the new computer in hand and the Hypertech chip on the way so I'm not to worried about it, I just want to make sure that I take care of the problem before I put the new computer in. I wonder if the dinky little ground wire that was connected to the frame by the battery had anything to do with it, it runs into the harness somewhere, I had to tighten it because it was loose... Oh well, all is well for the moment. I'm going to let it sit for a bit and try it again...

Originally posted by Fonzy
next stupid question is: Do computers make noise when your vehicle is running??? lol... Well, I've got what sounds like alternator whine in my computer. It's got a real fast tick type noise to it that increases as the rpm increases. I don't think this is normal is it? So far everything works great. Still seams a bit off when it runs though. I've got the new computer in hand and the Hypertech chip on the way so I'm not to worried about it, I just want to make sure that I take care of the problem before I put the new computer in. I wonder if the dinky little ground wire that was connected to the frame by the battery had anything to do with it, it runs into the harness somewhere, I had to tighten it because it was loose... Oh well, all is well for the moment. I'm going to let it sit for a bit and try it again...

maybe you run the bat. down and the alt. is working overtime to get it back up. all grounds need to be hooked up. hope that takes care of it.

I hope so to. Actually, the volt meter is up just a bit from where it has been, but not higher than it used to be... thats an awefull simple fix. If thats all it is, I'll be happy and angry all at the same time!...lol

Next time you have the computer unplugged, look at the mating connector on the harness and see if you pushed one of the recptacles backwards in the connector shell....

Bent pins are common at the factory; we are quoting robot cells to 100% inspect the pins at computer assembly.

mike

Yeah I checked the female end on the conector and it looked ok. Does this mean I shoudl rule out any other problems such as grounds??? I'm probably going to run it a few days and see what happens but I really don't want to put the new comp and chip in it with an existing problem... Thanks guys for all your help on this

You might try checking out this web site ZR2.com, they might have some more suggestions.

Thanks Rick, I'm a member at mys10.com and they always help out greatly on things but it's always nice to get other input, a second opinion if you will. This site is great. I hope to participate in it more down the road. Thanks again for the help

ok guys. no dice on the loose ground and bent prong I fixed. Again I drove it all after noon on and off and I juist went to start it and it wouldn't start... Wonder if it would have anything to ro with rock roads? Shouldn't but I was on one today and it did it and the first time this started I was on one earlier in the day. Doesn't make sence though... Any more info? What are the odds that I have a bad chip? and can I get one from the dealer??? Thanks guys

when the truck cut off will it start back up if you spray fuel into the air intake? if it will then you need to use a fuel pressure tester to check to pressure, because its hard to look at 60 lbs of pressure and know what it is. that pump should be 60 lbs. max. and at least 38 to 40 to run the truck. there is suppose to be 12 volts at your inj. all of the time, but should flash when they fire, or click. the 12 volts come from the fuse box. put a gauge on the fuel line. never seen a chip keep the car from running.