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

[Jon01]

Let us know how that goes. I'm curious what the deal is if that doesn't solve it.

[JJAB]

Guys, let me throw this out at you one last time. The owner of the blazer is 100% convinced that this is a fuel delivery problem so he wanted me to double check injectors . So, I pulled them and had them flowed and they were great. These are factory truck injectors. And again, what the blazer does is you can crank it and when you intially pull it out of the garage and go to hit yhe brakes it will fall dead. When you re crank it, it will sit and idle absolutely perfect. When you put it in gear and start to drive it, if you gently ease into the gas pedal, it acts as if it is about to bog down but if you drive it very aggressively and wide open it goes, but when you attempt to slow down and stop, it dies. Again, no vacuum leaks, Airtex E3270 fuel pump, stock fuel pressure regulator on truck intake, Hot Cam with 2500 stall.

There is a local tuner that tunes and does conversions, so we are probably about to take it to him. Thanks in advance for any input.

[vannatta20]

Might want to check your map sensor and that it is not loose. If its loose or the tabs are broken air will leak in messing up the readings and cause it to die and act all crazy..A scan tool will show map and if it is acting erratic.

[Custom 68]

guys, sorry I am late to this party. You really need to hook this up to a scanner to check all your sensors. This will ensure your MAF, MAP, AIT, and water temp is all correct. Any of those could cause running issues. If a temp reading is wrong it could think it is "cold" and dump lots of fuel in like a choke. I was working on my first TPI swap and had my water temp wired wrong it didnt like that.
Sounds like you tested your injectors but when I first started mine I had a few gummed up. I unhooked my coils and took the injector rail with the injectors in and raised it an inch or two and put a rag under them. I hooked them up one by one and tapped on them while my son cranked the motor till they all sprayed. Problem solved.
you may have covered all this as I just quickly looked over this post. I do think it is a questionable tune or a loose or bad sensor.
good luck

[JJAB]

Thanks for the advice. I am going to at least try and get the blazer to a place that owns a real scanner that can monitor the sensors. I do not own one, but I need one. Anyways, I will post the results when I find out something.

[Jon01]

What software was used to disable VATS?
HPTuners has a full scanner suite in it that could be used to monitor those functions.

I would almost bet $ that this is a tune issue.

[JJAB]

The tuner used HP tuner software. Thanks!!

[Jon01]

Did he tune it without running the scanner to ensure it wasn't getting KR!!???
Did he have a wideband in it while tuning it?

[BR3W CITY]

Originally Posted by Jon01

Did he tune it without running the scanner to ensure it wasn't getting KR!!???
Did he have a wideband in it while tuning it?

Interesting train of thought. He's running the GM hot cam from what I understand....I wonder if its throwing false KR from the lope of the cam and limping the car?

[JJAB]

Not that it matters, but what is KR? I have never heard of it and I intertested in what that is. Thanks!!

[ls1nova71]

KR is Knock Retard, the ammount of timing pulled out because the knock sensors are sensing ignition knock or "pinging".

[Jon01]

Originally Posted by BR3W CITY

Interesting train of thought. He's running the GM hot cam from what I understand....I wonder if its throwing false KR from the lope of the cam and limping the car?

A cam won't register KR, it will register misfires but that is an easy fix.

If the tuner played with the timing tables without running the scanner that's playing russian roulette with someone else's motor.

Excessive KR won't put you into limp home mode, it will put you into buy pistons or headgaskets mode.

I don't usually point fingers at the tuner but this is a case where the tuner didn't adequately do their job. Pure and simple.
With that cam it's going to have different idle/off idle air requirements than it did with the stock cam. DBW motors are super simple to tune idle quality on, it's the off idle transition that is trickier but not that difficult.
I could go on but in the end, OP needs to find a new tuner.

[JJAB]

Updating, for all you guys that scratched your heads along with me on this "ISSUE". The owner of the truck took it to a local tuner. Of course he began by checking all normal things, sensors, 02 readings, the tune itself ,etc... Getting to the point, he says that it is definately a fuel issue and not a tuning issue. He says the the pressure starts out at 60 psi on initial start and maintains at 55 - 58 for a certain time period. For some reason, the fuel pressure then drops or falls to 20psi, like the fuel system is getting air in the line. At this point he says he is serching for the reason it is doing so.

I installed the new tank and sending unit and I can remember that the sending had three ports. Fuel feed to the intake, fuel return, from the intake and a vent port. The vent port, I just left open. Originally, I ran it to the vacuum canister but later just left it unblocked. Could that be the problem.

Oh, I am running a 1987 blazer tank with the in the tank fuel pump, Airtex 3270(A/C Delco EP381 equivalent). One last thing, I also did not change fuel injetors, they are the stock truck injectors. I had them checked and they were verified to not be stopped up. What you think.

[Jon01]

Did he take it to a different tuner or the same one that tuned it before?

I don't see how this could be a fuel delivery issue, it will keep running if you feather the throttle right?

[JJAB]

No, he took it to a different tuner. And yes, to my knowledge it would keep running if you two feeted it. Note, this, if it died, it would take a minute to restart it. It would just turn ovoer and over as if it wasn't getting any fuel and then eventually it would crank.

[Jon01]

If it'll run 2 footed I don't see how it's a fuel delivery issue. But, I've been wrong before.

[JJAB]

My customer, the (blazer owner), took the the blazer to "LS tuner" and the tuner could not figure what was wrong with it. So I told him to bring it back and I would figure it out. Long story short, I finally figured it out. We had originally had custom lines fabbed up at a hydraulic/diesel shop and we first thought that the hose used was not fuel rated it was possibly collapsing. Turned out, the fuel pump that we had changed three times just wasn't supplying enough pressure under load. Originally we used an AIRTEX 3270 - the Oreilly brand of the A/C delco EP381. So, we went and purchased an A/C Delco EP381 and the blazer came alive.

For all that responded to my posts, Thank You!!!!!!!!!!!!!!!!!!!!!!!!!!

[Zoomin]

Glad to hear that mystery was finally knocked in the head.
Posted via Mobile Device

[Jon01]

That's surprising but good to hear that it is fixed and running strong!
Hope someone gets lots of enjoyment out of it!