6.0 Falls Dead, Cranks Up?????????

[clinebarger]

Originally Posted by BR3W CITY

Damn, thats a first DFW gets snow before Milwaukee.

Snow, What the hell is that?

[Zoomin]

Does the engine die even if you shift to neutral when braking?
Posted via Mobile Device

[Clyde65]

Jaab, I wouldn't be any help other than you can look mine over, I'm not a mechanic or guru. Clinebarger would be the one who could help you out. If I could help I would definitely help out. Clinebarger did a bunch of work on mine and I cant say enough about his ability.

[JJAB]

First, thanks Clyde65for the refernece and your response. Same to you BR3W City. I did reach out to Clinebarger and he responded, so thank you!!. Zoomin, yes, even if you were to shift the vehicle into neutral after decceleration and into braking, the moror will die. Actually, I went to look at the vehicle again on yesterday, just to see if something would hit me that hadn't before and sometimes, that damn thing is hard to start, almost like it has a carburetor on it, which it doesn't,????????????????

[Clyde65]

Ok stab in the dark here, could it be clogged/dirty injectors? Did the motor sit for a while?
Posted via Mobile Device

[ls1nova71]

I had a mail order tune once that whenever you unhooked the battery for an extended period of time would not run without your foot on the gas. It's like it had to relearn everything. But it only took it a few miles before it was right again so probably not the same thing as going on here.
This to me sounds like something mechanical since it happened all at once. Are you sure you don't have any vacuum leaks? Like maybe the pcv hose that goes to the valve cover. Maybe didn't get put all the way back on after tightening the rockers? Also, have you had the intake off? Did you put new gaskets on it if you have?
Other than that, you may need to put a scanner on it to see if everything is working right. Maybe your TPS took a dump on you, or the IAC. IAc could also be gunked up or the throttle body could be too. Have you had your tuner look at it yet? He should be able to scan kit to see if everything is functioning as it should
Posted via Mobile Device

[JJAB]

Clyde65, before installing the motor, I went to my local machine shop and had the injectors"flowed", or tested to make sure that were not clogged. But I guess one or two could still be clogged. I will look into it. Thanks!

Can the IAC or throttle position sensor malfunction without throwing a code?

[clinebarger]

Originally Posted by JJAB

Can the IAC or throttle position sensor malfunction without throwing a code?

The IAC can.

[faribran]

i am watching.... curious what the culpret is here....

[JJAB]

Just a FYI, I will be replacing the IAC sensor this weekend and rechecking fuel pressure once again. Thanks!

[4x4toy]

Keep us posted. I am curious also.

[JJAB]

I replaced the IAC. We started the truck and it idled for 30 to 60 seconds and settled down a bit. We then shut the truck off and was going to pull it out of the garage. When we went to crank it again, it wouldnt start.We turned it over again and again. We then turned it over and pressed the gas pedal and it started but would not stay running unless the gas pedal was pressed. I am really starting to think that the problem is either the computer itself or the tune. I am stumped!!!!!!!!!!!!!!!!!!!!!!!

[harnalien]

I had a similar problem and it was in my tune. I can't remember exactly where in the tune, but mine would shut off when I came to a stoplight. Now it only does it sometimes when I shift from drive to reverse.
Posted via Mobile Device

[502ms]

Wow. Any luck?

[JJAB]

No luck as of now. Our tuner went under the knife and he wont be able to look at it until early to mid January. Im really curious. Thanks for your interest!!

[JJAB]

Ran into a friend that helped me out a bit and he happened to be a lot more GM versed(he is a Master ASE technician)LOL, than me. Well we took a closer look at the blazer. When the Blazer acted up it threw a fuel pump driver circuit fault code. He explained it to me like this: The pcm controls the amount of amperage through the fuel pump by controlling the fuel pump ground wire with a driver module in the pcm. The pcm checks the amount of current draw coming through the fuel pump to see if it matches what it asked the pump to do. If it doesn't match, it sets a code. The code sets when the blazer starts acting up. Since this is the second new fuel pump installed since installation, most likely there is something wrong with the control module portion of the pcm.

FYI, fuel pump is being operated through a relay!!


Please chime in and tell me your thoughts. Plan of action at this point is that we are going to purchase a new PCM and have it tuned.

[BR3W CITY]

I'd assume that you could test this by just hot wiring the fuel pump and trying to drive it. Even if the pcm was throwing a code, it wouldn't affect the voltage to the fuel pump since you'd effectively bypass the pcm control.

Come to think of it....I'm pretty sure my fuel pump is just wired straight (just with the addition of a relay, iirc there is no pcm control on my pump at all, pulls same voltage at all times).

I'd go that route before buying a whole new pcm. I can't remember if it was brought up or if you tried it before but was the crank sensor ever messed with? The only pcm/fuel thing I really ever remember was that the pcm runs the fuel pump for 2 seconds on key on, but if it doesn't see rpm's from the crank sensor, it will not fire the injectors or coils even IF the fuel pump is working. So in that case the failed fuel pump would actually be a false positive.

[JJAB]

Well, I wired the fuel pump up seperately from the PCM and it didn't work. I guess I will try a different crank sensor like you said. Sooner or later, we will figure out whats going on.

[Jon01]

So it won't idle or stay running once it gets some heat in it unless you have your foot on the pedal?
If so it sounds like you need more idle air in the tune.
Are you DBC or DBW?

[Jon01]

Originally Posted by JJAB

Ran into a friend that helped me out a bit and he happened to be a lot more GM versed(he is a Master ASE technician)LOL, than me. Well we took a closer look at the blazer. When the Blazer acted up it threw a fuel pump driver circuit fault code. He explained it to me like this: The pcm controls the amount of amperage through the fuel pump by controlling the fuel pump ground wire with a driver module in the pcm. The pcm checks the amount of current draw coming through the fuel pump to see if it matches what it asked the pump to do. If it doesn't match, it sets a code. The code sets when the blazer starts acting up. Since this is the second new fuel pump installed since installation, most likely there is something wrong with the control module portion of the pcm.

FYI, fuel pump is being operated through a relay!!


Please chime in and tell me your thoughts. Plan of action at this point is that we are going to purchase a new PCM and have it tuned.

Your friend is thinking of a returnless system that varies voltage to the pump rather than having a regulator/return line.

[ls1nova71]

So it IS throwing a code now? I thought before it wasn't. Im going to put my money on this being a tune issue. Some tuners mess with things they shouldn't because they think they're better at it than GM engineers....
Posted via Mobile Device

[Jon01]

I'm with ls1nova71, it really sounds like a tune issue.

[JJAB]

Sorry for the delay in response. Yes , its throws a code just as it stalls and quits. Thing is, the code doesn't store or lock in. Well, I have an OBDII scanner and the code isnt there once the blazer's engine has already shut off. Anyways, my GM technician buddy said he couldn't remember the code #, but the code was a fuel pump driver circuit fault.

The blazer is drive by cable.

[Jon01]

You've eliminated the fuel pump and/or supply by hardwiring it around the PCM.
I really really think this is a tune issue.
You can crack the t/b open a bit more which should help till your tuner can get back ahold of it.

[JJAB]

Yes, we hard wired the fuel pump around the PCM the other day. That did not help any. Thanks for your information. I will try to open the throttle body a bit.