No start 4.8 - The 1947 - Present Chevrolet & GMC Truck Message Board Network

yossarian19 · 08-02-2013, 03:54 PM

2002 Vortec 4.8 w/ modified factory harness & Painless Performance ECM flash.

I've got spark, I've got fuel at the rail (haven't confirmed injectors firing) and I've got oil pressure. No 02s hooked up
While cranking it coughs once per revolution, sounds like.
Injectors have been sitting a long time since the engine was run, so I'm suspicious that they are my problem, but really don't know.
Any thoughts? Likely culprits? Common issues ? I'm going to put a noid light on injectors now & check for power around the engine compartment...

BR3W CITY · 08-02-2013, 03:59 PM

assuming vats was removed (doesn't sound like its a vats thing but I have to toss it out there)

Clogged fuel injectors from sitting is a start, did you check fuel pressure to make sure your maintaining 58 or so?

Check the ground wires for the coil packs, and all the little connectors on the coil pack "rail"

Custom 68 · 08-02-2013, 04:37 PM

My original injectors were clogged from sitting too. I raised the injectors out of the intake leaving them hooked in the rail. I unhooked the coil packs and injector wiring except one. I put a rag under that injector and with my son he turned it over, I tapped on the injector till it fired fuel. unhooked it and went to the next one. I did all 8 hooked everything back up and it fired right up and ran great.
There may be other ways but that worked good for me. I also did use some injector cleaner in my fuel a couple times after that.

yossarian19 · 08-02-2013, 07:08 PM

Well, i got it running after a shot of brake clean on the air filter. I'm reserving judgement as to whether it's still running off brake clean or gas now... I've seen a Mustang run for a minute or so off a shot of brake clean. Weird.
Will update when it's conclusive.

Roostboy102 · 08-04-2013, 07:23 AM

If it is your injectors I had good luck removing mine, boiling them for 5 mins, then blow carb cleaner thru them... Just an idea
Posted via Mobile Device

yossarian19 · 08-04-2013, 01:47 PM

Yesterday I stopped in at the truck. It coughed once and fired up, ran fine. I'm going to say it was sticky injectors that loosened up once the injector cleaner got to soak in.
FWIW, I'd reccomend a strong solution of injector cleaner & gas go in the tank BEFORE getting fuel to the rails. Once you've got straight gas up there, you'll have to drain the rails & lines & re-prime with cleaner or remove the injectors entirely to clean them.
All I did was let it sit a while with a can of sea foam in 4 gallons of gas, got that mix up to the rails & ignored it a while.

BR3W CITY · 08-05-2013, 01:15 AM

Or soak your injectors in seafoam BEFORE putting junkyard injectors into your engine

Its nice knowing that they won't try to spray varnish into the engine.

Just sayin.

08-02-2013, 03:54 PM	#1
yossarian19 Registered User Join Date: Sep 2011 Location: Nevada City, CA Posts: 908	No start 4.8 2002 Vortec 4.8 w/ modified factory harness & Painless Performance ECM flash. I've got spark, I've got fuel at the rail (haven't confirmed injectors firing) and I've got oil pressure. No 02s hooked up While cranking it coughs once per revolution, sounds like. Injectors have been sitting a long time since the engine was run, so I'm suspicious that they are my problem, but really don't know. Any thoughts? Likely culprits? Common issues ? I'm going to put a noid light on injectors now & check for power around the engine compartment...

08-02-2013, 03:59 PM	#2
BR3W CITY meowMEOWmeowMEOW Join Date: Sep 2009 Location: MKE WI Posts: 7,128	Re: No start 4.8 assuming vats was removed (doesn't sound like its a vats thing but I have to toss it out there) Clogged fuel injectors from sitting is a start, did you check fuel pressure to make sure your maintaining 58 or so? Check the ground wires for the coil packs, and all the little connectors on the coil pack "rail" __________________ *'66 Short Step / SD Tuned / Big Cam LQ4 / Backhalfed /Built 4l80e / #REBUILDEVERYTHING* MY BUILD THE H8RDCPTR //\\ MY YOUTUBE CHANNEL REV J HD

08-02-2013, 04:37 PM	#3
Custom 68 Registered User Join Date: Nov 2001 Location: Springfield, MO Posts: 2,939	Re: No start 4.8 My original injectors were clogged from sitting too. I raised the injectors out of the intake leaving them hooked in the rail. I unhooked the coil packs and injector wiring except one. I put a rag under that injector and with my son he turned it over, I tapped on the injector till it fired fuel. unhooked it and went to the next one. I did all 8 hooked everything back up and it fired right up and ran great. There may be other ways but that worked good for me. I also did use some injector cleaner in my fuel a couple times after that. __________________ Dave 1968 Custom Chevy with turbo charged 5.3 gen III 4l80e swap 1967-71 GMC 3/4 ton long step 4x4 (not sure what year exactly?) "A good friend will bail you out of jail...but a true friend will be sitting next to you saying "that was frekin awesome". "If it doesn't fit force it...If it breaks then it needed to be replaced anyway!"

08-02-2013, 07:08 PM	#4
yossarian19 Registered User Join Date: Sep 2011 Location: Nevada City, CA Posts: 908	Re: No start 4.8 Well, i got it running after a shot of brake clean on the air filter. I'm reserving judgement as to whether it's still running off brake clean or gas now... I've seen a Mustang run for a minute or so off a shot of brake clean. Weird. Will update when it's conclusive.

08-04-2013, 07:23 AM	#5
Roostboy102 Registered User Join Date: Jan 2012 Location: Amish Country Posts: 138	Re: No start 4.8 If it is your injectors I had good luck removing mine, boiling them for 5 mins, then blow carb cleaner thru them... Just an idea Posted via Mobile Device __________________ 72 C10 - Multicolor, 4.8 ls, NV3500. Sold 72 K5 - Under Construction

08-04-2013, 01:47 PM	#6
yossarian19 Registered User Join Date: Sep 2011 Location: Nevada City, CA Posts: 908	Re: No start 4.8 Yesterday I stopped in at the truck. It coughed once and fired up, ran fine. I'm going to say it was sticky injectors that loosened up once the injector cleaner got to soak in. FWIW, I'd reccomend a strong solution of injector cleaner & gas go in the tank BEFORE getting fuel to the rails. Once you've got straight gas up there, you'll have to drain the rails & lines & re-prime with cleaner or remove the injectors entirely to clean them. All I did was let it sit a while with a can of sea foam in 4 gallons of gas, got that mix up to the rails & ignored it a while.

08-05-2013, 01:15 AM	#7
BR3W CITY meowMEOWmeowMEOW Join Date: Sep 2009 Location: MKE WI Posts: 7,128	Re: No start 4.8 Or soak your injectors in seafoam BEFORE putting junkyard injectors into your engine Its nice knowing that they won't try to spray varnish into the engine. Just sayin. __________________ *'66 Short Step / SD Tuned / Big Cam LQ4 / Backhalfed /Built 4l80e / #REBUILDEVERYTHING* MY BUILD THE H8RDCPTR //\\ MY YOUTUBE CHANNEL REV J HD

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