[homer911]

Ok guys this is really starting to piss me off:grrrrrr: Lets start from the beginning again. Driveing down the road over 40mph start to slow down and sometimes not all the time when it hits around 20 shuts right off. No fuel getting to TBI. I have so far replaced MAP sensor, Oil Pressure Switch, Fuel Pump and Sending Unit (last night). If i pour some fuel down the TBI it will start and if i hold foot on throttle a little bit it will stay running. IF i let off she will die out. Other times like this morning started it up everythings good then shut down, but started right back up.
This malefunction is pissing me off so much i am about ready to take a long drive off a short pier :gasp:. Hopefully someone out there can run me in the right direction.

BTW 93 K2500 Burban 5.7L

 

[ChevyFan]

I know these can be frustrating, but you're working through the possibilities one at a time and you'll come up with the issue sooner or later.

 

[homer911]

I know these can be frustrating, but you're working through the possibilities one at a time and you'll come up with the issue sooner or later.

The only problem though is it is starting to get a little pricey and the pocket book its readding empty.

 

[GaryL]

Could be the throttle position sensor or the idle air control valve. I'm not sure how to test them, maybe someone else can help with that. You didn't mention changing the fuel filter, might check that as well.

 

[FireRed]

Besides the fuel filter mentioned, also have you checked the fuel line at the engine with a vacuum gauge to see if there may be a blockage.

Phil

 

[homer911]

I ordered a new IAC and TPS yesterday. They should be in friday. I ordered them from www.RockAuto.com . THere prices are far sheaper then local auto parts ecen after shipping. This will be the last time I throw money at her. If this dont work off to the repair shop.

I have checked for vaccum leake and found none and replaced the fuel filter about 2 months ago. Sorry for not mentioning it before..

 

[MrShorty]

It sounds to me like a possible fuel delivery issue. I don't know much about TBI, but have you verified that fuel delivery is good? Fuel pressure at spec? Fuel pump working? Injectors firing? Being intermittent, remember to check when it's acting up.

Maybe someone here who is more knowledgable in the early '90's TBI fuel system can help with specifics, but I think the first thing I would be checking is fuel delivery from the tank to the injectors.

 

[homer911]

Ok people yesterday i through some more money at her. Installed IAC and TPS. damn thing died over and over again. So i broke down and took it to the repair shop. Well he got a look at it yesterday and calls me. Say it is the fuel pump. I started laughing :rofl:. Told him that i just in stalled the fuel pump and sending unit monday night. He was dumb founded. He told me to make sure that it was not the fuel pump that he needed to drop the tank and do some more testing. Well i told him no ou dont. Lift up the back mat and there are 4 selftapping bolts that u undue and your right on top of the sending unit. So he does some more testing this morning. Calls me up just a few min ago and says its the computer. Now this kinda pissed me off but on the other hand i am releived. But he tells me that he cant find a computer. So i call around and sure as shyt i find one first place i called.

So anyways He will see if this finally fixes the problem thats been going on for sometime now.. I will give a update on this after a few days due to the irregularity of this problem.

OH BTW on my s-10 blazer lastnight on the way home. THe dash lights quit working. no blown fuse. so i beleave that it is the head light switch. Am i correct in this thinking??????

 

[homer911]

:grrrrrr::grrrrrr::grrrrrr::grrrrrr:

Why is this crap happiening to me....... The guy at the repair shop just called to tell me that it is still doing the same thing.... Says if he grounds the injector curcuit to the computer the injectors fire. WTF it going on here... New computer, sending unit, fuel pump, IAC, MAP, TPS, & oil pressure switch... IS there any electrical guru out there that may have any fricken idea wtf is going on here????????????????????????

 

[ChevyFan]

I know how frustrating it can all be.

When you say that it dies, what do you mean? Does the electrical shut down, or does the engine just stop running and everything else like the stereo and wipers still works fine?

 

[homer911]

I know how frustrating it can all be.

When you say that it dies, what do you mean? Does the electrical shut down, or does the engine just stop running and everything else like the stereo and wipers still works fine?

when it dies there is no power getting to the injectors unless u ground the injector curcuit. everything else is working though

 

[MrShorty]

I'm not familiar with the TBI setup, but, looking at the wiring diagram in Haynes, the injectors are ground side switched. This means that the injectors have a constant power supply (12V I believe), and the computer acts as a switch on the ground side of the circuit. I could be wrong, but this

there is no power getting to the injectors unless u ground the injector curcuit.

sounds sort of normal. If the injectors are functioning correctly, they won't fire unless the circuit is completed on the ground side.

That said, basically, what sounds like is happening is that the computer is not completing the circuit, and the injectors are not firing, which means the engine won't start or stalls.

A lot has been replaced, some of which doen't seem to apply to the specifics of the problem here. While replacing all of those sensors, has anyone asked the computer if it can see a problem (ie has anyone pulled codes)? As I said, I'm not familiar with the TBI system, but other computer controlled systems will store DTC's that may lead you to know where the problem lies.

Other systems (I would assumes the TBI system does as well) have "failsafes" in the programming that prevent the computer from opening the injectors if certain signals aren't present. For example, if the computer isn't gettinga crankshaft position sensor or camshaft position sensor (not sure which your engine uses) signal, the computer thinks the engine isn't rotating, and doesn't fire the injectors (after all, it would be silly to dump fuel into the engine if it isn't turning over). Sometimes this signal goes straight to the PCM, other times it goes through the ICM. Have you had the ICM tested? Are there any DTC's related to the ignition system or the CKP/CMP?

If nobody here can post the necessary information, the first thing I would do tomorrow would be to go to the library and see if they have a good manual that you can refer to to figure out exactly how the system works, and maybe even get a step by step diagnostic tree for this kind of problem. I looked up Howell, MI's public library, which claims to have a reasonable collection by Motor which, if they have the light truck volume for your year, should have all kinds of information.

 

[homer911]

I'm not familiar with the TBI setup, but, looking at the wiring diagram in Haynes, the injectors are ground side switched. This means that the injectors have a constant power supply (12V I believe), and the computer acts as a switch on the ground side of the circuit. I could be wrong, but this sounds sort of normal. If the injectors are functioning correctly, they won't fire unless the circuit is completed on the ground side.

That said, basically, what sounds like is happening is that the computer is not completing the circuit, and the injectors are not firing, which means the engine won't start or stalls.

A lot has been replaced, some of which doen't seem to apply to the specifics of the problem here. While replacing all of those sensors, has anyone asked the computer if it can see a problem (ie has anyone pulled codes)? As I said, I'm not familiar with the TBI system, but other computer controlled systems will store DTC's that may lead you to know where the problem lies.

Other systems (I would assumes the TBI system does as well) have "failsafes" in the programming that prevent the computer from opening the injectors if certain signals aren't present. For example, if the computer isn't gettinga crankshaft position sensor or camshaft position sensor (not sure which your engine uses) signal, the computer thinks the engine isn't rotating, and doesn't fire the injectors (after all, it would be silly to dump fuel into the engine if it isn't turning over). Sometimes this signal goes straight to the PCM, other times it goes through the ICM. Have you had the ICM tested? Are there any DTC's related to the ignition system or the CKP/CMP?

If nobody here can post the necessary information, the first thing I would do tomorrow would be to go to the library and see if they have a good manual that you can refer to to figure out exactly how the system works, and maybe even get a step by step diagnostic tree for this kind of problem. I looked up Howell, MI's public library, which claims to have a reasonable collection by Motor which, if they have the light truck volume for your year, should have all kinds of information.

Thanks for the info and your input. It is not setting any codes at all and there are no stored codes. The ICM has been tested and works. It gets plenty of spark just no fuel at times. I was looking in my Chilston book the other night and noticed that the fuel injectors curcuit runs to the TCC brake switch. I beleave TCC = torque converter clutch? Now i have no idea where that it located but would beleave it to be in the transmission. Does this sound like it maybe where the issue is?

 

[MrShorty]

the fuel injectors curcuit runs to the TCC brake switch. I beleave TCC = torque converter clutch? Now i have no idea where that it located but would beleave it to be in the transmission. Does this sound like it maybe where the issue is?

I can't get to my Haynes manual right now, so I can't see the wiring diagram. I expect that the link you are referring to is simply that the TCC brake switch and the injectors share a common power supply. As I recall from looking at the wiring diagram last night, there is nothing else between the computer and the injector on the ground side of the injector. I expect if you look further, you'll see that the injectors share that same power supply with much of the engine management system.

Because you are able to operate the injectors by manually grounding them, I wouldn't expect that there is any problems on the + side of the injectors. If I've misunderstood something, please clarify, but from what you've indicated, I gather that the injectors have a constant, uninterupted power supply. My interpretation of what you have posted suggests that the problem is in the ground side of the injector circuit.

Another thought, have you verified the condition of of the computer's ground(s)? It's an oft neglected element of the engine management system, but, because the computer is a ground switch for the injectors, the computer's ground(s) are a critical part of the operation of the injectors.

 

[84fiero123]

I just read threw both pages and unless my memory is getting worse, and that wouldn’t surprise me.

You didn’t replace the ignition module, under the distributor cap. About a $50 part. I had the same problem, on a trip to her mothers Melanie stopped to get gas a few miles away. It wouldn’t start after filling up.

I sprayed starting fluid into the throttle body and she started right up. Had her drive it home and tested the module. It was bad, they can do things like that. Work and then not, and then work.

Fords used to be famous for them going after getting hot. Then after cooling down they would be fine until they got hot again.

Make sure if you replace the module you use the heat sink grease.

To be honest I forget how my buddy told me to test it. But it is testable. I looked in the Haynes manual but they don’t give the test procedure for the module.


If anyone knows the way to test them speak up. if not i will give him a call tomorrow.

 

[homer911]

I just read threw both pages and unless my memory is getting worse, and that wouldn’t surprise me.

You didn’t replace the ignition module, under the distributor cap. About a $50 part. I had the same problem, on a trip to her mothers Melanie stopped to get gas a few miles away. It wouldn’t start after filling up.

I sprayed starting fluid into the throttle body and she started right up. Had her drive it home and tested the module. It was bad, they can do things like that. Work and then not, and then work.

Fords used to be famous for them going after getting hot. Then after cooling down they would be fine until they got hot again.

Make sure if you replace the module you use the heat sink grease.

To be honest I forget how my buddy told me to test it. But it is testable. I looked in the Haynes manual but they don’t give the test procedure for the module.


If anyone knows the way to test them speak up. if not i will give him a call tomorrow.

MAN MAN MAN!!!!! I am so upset with meself over this. Today the shop called me and he said he put in a ICM. Now i first thought that this may of been the problem but, i was getting spark the whole time and no fuel. So after all said and done ($700.00 later) it was just a $30 part. I wish that i would of gone with my first thought on this. But after all the mechanic that did the work does not understand it either. If the ICM is bad it normally shuts down spark and fuel or spark but not just the fuel. So hopefully others will find this info helpful and not spend a alot of time and money on crap they dont need!!!!!!!!!!



I would like to thank ya'll for your help in this matter. :great::great::great::great:

 

[GaryL]

I apologize. I had this same problem on a 92 S-10 Blazer my wife had about 8 years ago. I completely forgot about it (read "blocked it out"). I did as you did and started replacing parts (fuel injection "spider", tps, map, computer, etc.) and ended up spending $1,000 in parts. My neighbor, who was a Chevy Service Manager, told me to check the ICM. I kept telling him I am getting spark, just not fuel. I finally sent it to his shop and he replaced the ICM and I never had another problem.

Again, sorry I forgot this.

 

[84fiero123]

On these newer vehicles it also does control fuel, for some reason. And I can’t remember why. I knew once, but I forgot.

Glad to hear you got it running.