6.0 Falls Dead, Cranks Up?????????
 

Ok fellows, you have helped me throughout this swap. I have completed the swap and the tuner has come and completed the in person custom tune. It has since been two weeks since the tune. Four days ago, the blazer would crank and run for thirty seconds or so and die out; would only stay running with your foot on the gas pedal. Long story short, I had to re-vent the gas tank. Prior to reventing the gas tank, I had vented the tank by the vent tube or hose that goes to the charcoal canister. I guess it wasn't sufficient. Nowm while driving the blazer, when I come to a stop, sudden or not, the blazer falls dead, but will crank right back up. Thing is, this was not a problem when the tuner was in the vehicle. Help me out if you can.

Here's a little more information:

Single gas tank with EP381 fuel pump, ECM is pulling no codes, fuel pressure regulator is new,truck intake, all sensors are new.

I am running a very short, straight air elbow with a rather cheap, short a filter. I just haven't upgraded it. Couold this be my problem?

Re: 6.0 Falls Dead, Cranks Up?????????
 

stock or aftermarket tank?

sounds to me that when you stop suddenly, your motor runs out of fuel....

Re: 6.0 Falls Dead, Cranks Up?????????
 

It is a stock blazer/suburban tank with the efi sending unit with an EP381 fuel pump.

Re: 6.0 Falls Dead, Cranks Up?????????
 

Only stays running under heavy throttle and dies on a stop?
The only running wide open part suggests either a vacuum leak, or a problem with the MAF.

Dying on a stop can be a few things; if you don't have tank baffles and were low on gas, then the engine might have just starved. A full tank will reduce the problem, but getting some tank foam or baffles should stop it.

Vacuum leak is still plausible, as the brakes require a deal of vacuum, and with a big lopey cam, its not unheard of to stall out of die under heavy braking (hence the use of hydroboost or vac cannistor).

Last option could be the lockup if your running an auto; I was just dealing with some problems regarding lockup and big cammed auto's; the solution involved the misfire count from the cam, causing erratic lock and unlock.. Staying locked up on decel can "bog" the engine and stall it out for a second. Sometimes its not even a "full" stall, it will drop to 1rpm, not throw lights and then pop all the way back up to 790 at idle.

Re: 6.0 Falls Dead, Cranks Up?????????
 

I really appreciate the insight. The tank we have does have a factory baffle. I have probably went through a entire can of carb spray searching for leaks. I have started making this a part of the install. So, no leaks. Actually, it runs just as smooth as a baby's bottom idling, even after it may cut out or die after stopping, when you crank it back up, it runs just smooth. Other than that I will explore(evaluate) the other things you mentioned.:metal:

Re: 6.0 Falls Dead, Cranks Up?????????
 

Let me mention another thing. The sending unit has four "outlets", so to speak. I have them connected to the following:

1. Large outlet - Fuel feed to the intake
2. Medium outlet - Designed to go to fuel filler neck - open as a vent
3. Next to smallest - Fuel return line to intake
4. Smallest - connected to hard line that goes to charcoal canister up front,
but it is currently not connected to a canister

I don't know why but I just thought this may have something to do with my problem. What do you think.

Re: 6.0 Falls Dead, Cranks Up?????????
 

I was confused because in the first post you said it would only run with your foot wide open, but now you say it runs and idles fine...

So it STARTS fine, IDLES fine, and ACCELS fine, but only under ANY sort of braking, it starts to die...then you can start it right back up just fine, repeat?



I don't think the small line would matter, I'd just cap it if you have the other one vented.

Re: 6.0 Falls Dead, Cranks Up?????????
 

Sorry for the confusion. Yes, keeping my foot on the accelerator was the only way to keep it running prior to me venting the tank via the filler neck vent hose. Now, since venting it(tank), it starts and idles fine. Now, upon sudden or quick braking, the engine dies, but re-starts just fine. Ocassionally, upon normal braking, the motor will die too.

Re: 6.0 Falls Dead, Cranks Up?????????
 

After driving the blazer again and trying to get very specific sysmtoms, this is what it ooing exactly. First, PCM is throwing no codes. Under normal driving conditions in the city, normal stop and go, the blazer(engine) does wonderful no issues. If you get into the throttle or goose the motor from "light to light", when braking or coming to a stop, the engine dies and really you dont really know its dead until the steering wheel freezes up; cranks right back up. Or, if you get onto the highway and decelerate from highway speeds& rpm's, the engine does the same thing, but will crank right back up.

I am going to cap off the vent tube that goes to the vacuum canister. I am also going to re-attach the larger fuel filler neck vent hose and purchase a vented gas cap to see if this solves my problem.

To those who are using blazer/suburban gas tanks, I am curious as to how you vented your tank. Any information would be helpful. All other things considered, the 6.0/4l60e combo is awesome and runs great. But as you know the little things can sometimes drive a person crazy. THANKS!!!!!!

Re: 6.0 Falls Dead, Cranks Up?????????
 

Mine used to go exactly this, you had to *blip the throttle getting off the freeway to stop it from dying. It was staying locked up too long, and bogging the engine....blipping the throttle released lockup and let it coast down. After the misfire count was adjusted by my tuner, it doesn't do it anymore.

Re: 6.0 Falls Dead, Cranks Up?????????
 

Thanks, last question before you had your tuner adjust that lock up issue, was your computer throwing a code. This blazer is throwing no code. Thanks for the info.

Re: 6.0 Falls Dead, Cranks Up?????????
 

Do the brakes make it stall while sitting still? If they do, you may look into a faulty brake booster. If that is not the issue, is it possible your brake switch is hooked backwards and causing the TCC to lock with the brakes applied rather than making it unlock? If it occurs only while driving, sounds like a TCC fault to me.

Re: 6.0 Falls Dead, Cranks Up?????????
 

Thing is, i dont even have the brake switch hooked/wired to the tcc. Could this be my problem?

Re: 6.0 Falls Dead, Cranks Up?????????
 

No codes were being thrown, we had it hooked up to HPT watching the misfire count and watched to see when it commanded lockup. We just put 2+2 together, then found out that it was a problem a bunch of people had but didn't know how to fix.

You NEED to connect that brake switch to the TCC, get a 4 post brake switch if you don't have one currently.

Re: 6.0 Falls Dead, Cranks Up?????????
 

Okay, you say hook it up to the TCC, where is that connection going to. Will that wire be coming out of the pcm? Do you have a schematic to show me where to hook up to the tcc?

Re: 6.0 Falls Dead, Cranks Up?????????
 

I have an aftermarket harness, and a new body harness that uses NONE of the stock colors....might prove trickey for what your doing.

IIRC there should be 4 wires, mine were pink, purple, green and white, but yours won't be.

http://67-72chevytrucks.com/vboard/a...1&d=1335141912

and here's what I used.
http://i112.photobucket.com/albums/n...y/DSCN0094.jpg
http://i112.photobucket.com/albums/n...y/DSCN0091.jpg

Re: 6.0 Falls Dead, Cranks Up?????????
 

THANK YOU!!!!!!!!!!! :metal:

Re: 6.0 Falls Dead, Cranks Up?????????
 

I spelled Ignition wrong;)

Re: 6.0 Falls Dead, Cranks Up?????????
 

hahaha, was it you i stole that from? Credit for the spelling error is all yours :)

Re: 6.0 Falls Dead, Cranks Up?????????
 

:lol:

Re: 6.0 Falls Dead, Cranks Up?????????
 

Gentleman, no solution as of yet. Lets be more exact of the symptoms. First of all, on initial crank up, motor cold, truck cranks fine. As the truck/motor warm to operating temperature, the motor will begin to stumble/bog down and shut off. Now at this point, the truck is in park. I also have a fuel pressure guage attached and while idling, the guage is reading constant 50-52psi. When the key is turned to the on position, the guage reads 60 and then after crank it settles at 50-52psi. That being said, this is not a fuel pressure issue. After re-cranking the truck about ten different times, the truck began to idle and run longer and better. As I drove the truck this is what it would do. Normal driving, 20 to 30 mph, drives fine or balls to the wall, it responds, but either scenario, when I ease or come off of the accelerator, the motor bogs and and goes dead. But everytime, it will crank right back up. Also, battery tested 13.5 to 14 volts before and during the test. Any help is appreciated.

Re: 6.0 Falls Dead, Cranks Up?????????
 

Bad relay? getting hot, maybe to the injectors or?

Re: 6.0 Falls Dead, Cranks Up?????????
 

50-52 still seems low as on-rail pressure should be around 58... 50 should get it to run but it still seems a tad low. That pump should be able to maintain 80-90 psi (unregulated, according to the manufacturer).

I'd think about the possibility that your internal regulator is not working properly, or maybe your fuel pump isn't wired properly and overheating, or over-drawing on the wires. Is your fuel pump hotwired, wired off a relay, direct, which?

Re: 6.0 Falls Dead, Cranks Up?????????
 

It is wired off of a relay. This truck has a custom harness made from Nelson in San Antonio. We are just totally mind boggled because we beat this 6.0/truck nearly to death during the tune and it didn't exhibit any of these problems. I guess stuffhappens, huh?

Re: 6.0 Falls Dead, Cranks Up?????????
 

Not sure if I mentioned it before, but the pump os an Airtex 3270. It is supposed to be the equivalent to the AC Delco EP381just a different brand. Specs say there two different EP3270 pumps with the same part number, one supplying 65psi and the other supplying 80 to 90 psi. Either way this pump should be sufficient, right? What would cause the pressure to be backed down to 50 at idle. The regulator is new but maybe I need change anyway.

Re: 6.0 Falls Dead, Cranks Up?????????
 

Here is something i just thought about. I am running a Sorenson fuel pressure regulator, autozone part #800-329. In the part description it says it is for a returnless fuel set up and it is supposed to regulate pressure to 50psi. But it says the regulator is ajustable. How is it adjusted.

Ok, I have the truck intake on this 6.0, what fuel pressure regulator do I need to get that will install in the truck intake but regulate the pressure at 58to 60.

Re: 6.0 Falls Dead, Cranks Up?????????
 

Also, just a thought. You know how the 80's trucks come with the vacuum restrictor in line on the vacuum hose from the booster to the carburetor. Well I have a factory 2002 truck vacuum hose, straight hose no restrictor, going from the booster to the back of the intake. Could this "open" hose be choking the motor down during braking or sudden decceleration?

Re: 6.0 Falls Dead, Cranks Up?????????
 

Do you have a return or return less fuel rail? 50psi isn't enough.
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Re: 6.0 Falls Dead, Cranks Up?????????
 

It is the return style fuel system. The truck has the "truck intake" with the feed line and the return line.

Re: 6.0 Falls Dead, Cranks Up?????????
 

http://leftwingnutjob.net/wp-content...012/05/WTF.jpg

Dude you are confusing the effing heck out of me.

I don't think a vacuum resistor has anything to do with anything on these motors, as I sure as heck don't have one.

You have a fuel pump that don't know the output of....the 80-90psi pump will be regulated back properly, I would be concerned that a 65psi (peak) pump might run the risk of being insufficient under certain load conditions.

That FPR listed doesn't fit LS series truck according to the "make it fit" listing on the autozone website....how did you end up with this one? Did the original one fail, or are you for some reason (please tell me no), running 2 fpr's?

Re: 6.0 Falls Dead, Cranks Up?????????
 

My apologies. No I am not running two regulators. When I told you the two different psi of the pump, I was reading online about the airtex fuel pump and it stated that with the same part#, EP3270, some of the pumps are 65psi and some are 80-90psi. Also, the sorenson 800-329 regulator sold at autozone is the replacement regulator for an 2002 Chevy 2500. No jerry-rigging, it fit right in place on the fuel rail of the intake. The reason for purchasing the regulator was just instinctive amongst buying other new parts when doing the swap.

As far as the vacuum resistor, I was just throwing something out there as a possibility.

Re: 6.0 Falls Dead, Cranks Up?????????
 

Aight, thats just me being frustrated that I can't help you fix it so far :(

Ok, so even if its a new regulator, we've thrown out all the easy stuff, time to start looking at the less-likely problems. I'd see if you can trade the reg in as defective, just to try a new one to look for improvement.

Might be worth it to doublechekc the fuel pump wiring and make sure it didn't ground out or come loose or something like that....my brain hurts on this damn thread...I need your truck running.

Re: 6.0 Falls Dead, Cranks Up?????????
 

BR3W CITY, man i appreciate your dedication to this thread!!! I will be trading the regulator out tomorrow. I will definately get back to you ASAP. Thanks again to all. :metal:

Re: 6.0 Falls Dead, Cranks Up?????????
 

This is the kind of thread nightmares are made of! But first off, I wouldn't put much faith in that Autozone website. It also says the regulator bolts on! Anyway, have you checked to see what the pressure is with the engine running with the vacuum line to the regulator unhooked? Also, is this a DBC set up? I've seen IACs not be able to open fast enough when you let off the throttle and cause stalling issues. Also not having a VSS will cause quick stop stalling since the PCM doesn't know you're stooping it doesn't adjust the IAC.
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Re: 6.0 Falls Dead, Cranks Up?????????
 

Awesome information!!! I have not checked for fuel pressure with the vacuum line off the regulator, but I will do this today before installing the new regulator. Yes, this is a drive by cable setup.If it turns out to be the IAC not opening fast enough, what is the fix? Thanks!!!!

Re: 6.0 Falls Dead, Cranks Up?????????
 

Good thoughts Ls1Nova!


I'm also wondering if its possible that a problem with the MAF could be involved? I mentioned it earlier but it didn't seem like the prime suspect. Usually it would throw a low-input voltage code, but MAF failures can cause stumbling and stalling, weird engine response etc. If the MAF isn't placed within a reasonable (but not too close) distance from the TB, and on the correct portion of the intake, it can be problematic. What are you running for an intake elbow or CAI or?

Re: 6.0 Falls Dead, Cranks Up?????????
 

I have a question, if your running the truck intake and the return style fuel rail, why a regulator? the fuel rail has its own regulator. I would personally change to a Walbro 255 pump or a Pierburg pump, or at least one that puts out about 100psi, let the regulator do its job.

Re: 6.0 Falls Dead, Cranks Up?????????
 

Clyde, first thanks for the question to aid me in fixing the problem. The regulator that i am referring to is the regulator on fuel rail. That is the regulator that i was referring to that i replaced or bought new while doing the engine swap. Lastly, will either of the two pumps you just mention fit in factory EFI sending unit from a 1990's model suburban gas tank/sending unit?

BR3W and LS1 Nova, truth is the MAF is placed not more than 4 to 5 inches from the throttle body, directly in front of it. My friend, whom I did the swap for, hasn't bit the bullet to buy a kit with proper elbow, etc.. to properly located the MAF. So, from your comment, I see this could be a real big problem.

Thanks!!!!!!!!:metal:

Re: 6.0 Falls Dead, Cranks Up?????????
 

GM recommends 6-12", and on the upper 1/3 of the pipe, between 12 and 3 usually...and the issue with having a super short intake or putting the MAF right in front, is that supposedly the air turbulence is too great that close to the TB, and the subtle changes in TB position cause erratic changes in air flow across the MAF and can trigger running and fueling issues. IIRC, MAF failure can cause the pcm to use a different or adjusted table (don't quote me on that part, but i swear I've discussed it with someone here before)

fwiw, this is the intake setup I'm using. The MAF is about 11-12" inches away (max that my harness reached), and clocked to about 2 oclock.
http://i112.photobucket.com/albums/n...y/DSC_0681.jpg

Re: 6.0 Falls Dead, Cranks Up?????????
 

I got you. I cant ask for a much better visual pic than that. As always, the knowledge gained here is plentiful. Thanks!! :metal: