2000Silverado wont run

BrianF

Original poster
Member
Jul 24, 2013
1,192
West central Sask.
Friends 2000 5.3l 290K km has a few issues. First it was running rough, scanner showed it was running lean, a cylinder misfire and the o2 sensors had issues. Of course I didnt record the codes. The tb was cleaned, but not removed, battery disconnected. The egr cleaned and so was the maf. It ran better, threw the same codes and then began an intermittent start issue. It would crank, fire briefly and then stop. We kept it cranking and it continues to spark but wont fire again. I dont have a fuel pressure gauge but there seems to be pressure at the rails as it shoots out with some force. When it was idling its timing was jumping from 14 to 25 degrees and back frequently.

Now it wont start, the codes were wiped and it wont run to get them back again. I want to re-clean the tb with it removed but wondering what would cause a no start. Surely issues with the o2 sensors wouldnt cause the no start.

any thoughts?
thanks
 

gmcman

Member
Dec 12, 2011
4,656
What did you use to clean the TB?

What did you use to clean the MAF?

Have you ever replaced the plugs?

Are you sure there are no vacuum leaks?

Have you ever changed the fuel filter? Are fuel filters serviceable on this vehicle?...I don't know.

How old are the O2 sensors?

What condition is the air filter?

The engine needs fuel, air, and spark to run..compression as well so I assume that's sufficient since the no-start was abrubt.

Could be a crank sensor, plugged fuel filter, TB electronics damaged during cleaning.

Make sure all the connections are clean and tight at the sensors.
 

gmcman

Member
Dec 12, 2011
4,656
I want to add you really need to verify correct fuel pressure. Also could be a security issue now but if it's sparking then I would doubt it.
 

stormsurge

Member
Jan 29, 2012
386
I had this happen to me on my 99 Z71. I replaced a sensor on top of the motor and it ran great. Ill try to figure it out and get back to ya. Dam thing cost me $80.00 at the dealer.
 

djthumper

Administrator
Nov 20, 2011
14,950
North Las Vegas
Waiting to see that answers to GMCmans questions.
 

jimmyjam

Member
Nov 18, 2011
1,634
the lean codes kinda make me think there's an issue with fueling, perhaps clogged injectors if the fuel pressure seems ok and in the absence of a vacuum leak. Hard to diagnose with such limited information.
 

RayVoy

Member
Nov 20, 2011
939
BrianF said:
Surely issues with the o2 sensors wouldnt cause the no start.

any thoughts?
thanks
A cold engine does not use the O2 sensor(s), they need to be at their operating temp before the PCM talks to them.
 

BrianF

Original poster
Member
Jul 24, 2013
1,192
West central Sask.
I figured the o2 were not used on a cold engine, is the maf as well? Or is it just using predetermined measurements? I am trying to find a fuel pressure gauge to use as well. I think it would have the external filter. Next up is to replace the o2 sensors as well, they are just plain old. The maf and tb were cleaned with tb cleaner but I will check them again and take the tb off to do a more thorough cleaning.

once it is running I can trace the misfire, change the o2 sensors and chase the lean condition (will spray down the intake to find leaks). My buddy tells me there used to be some sort of command start on it and it had a security feature. Now I have no clue how to trace that sort of issue if there is some sort of electrical gremlin.

edit: plugs and wires are new.
 

Wooluf1952

Member
Nov 20, 2011
2,663
Milwaukee, Wisconsin
A dirty t-body shouldn't cause a no-start and the 5.3 doesnt have that problem, like the I6. :twocents:
 

gmcman

Member
Dec 12, 2011
4,656
I'm trying to figure out why it was running so bad before it came up with the no-start problem.....:undecided: Can you give us a timeline of repairs and symptoms? I don't know about how picky the 5.3's are with plugs but which plugs did you use?

You may have fuel fouled plugs, I would pull the misfire cyl and maybe another and note (post pic) of the business end of the plug. Could be caused by leaking injectors, dunno but if there's no security issues, then you have a fuel or spark issue, can't imagine it's not getting air unless you damaged the TB.

Pull the intake tube and see if the throttle butterfly opens when you step on the gas.

Will it try to start if you crank it with the gas pedal to the floor? Don't pump it but hold it down.

- - - Updated - - -

Did anyone accidently fill it with diesel? Don't laugh.
 

BrianF

Original poster
Member
Jul 24, 2013
1,192
West central Sask.
I will get a timeline of the repairs. I believe it got ac plugs in it, I remember telling buddy they are the only plugs to use. I figured the o2's were the main cause of the rough running but I cant scan their output at the moment.

I will get a plug pulled and check what color it is.

We had continued to crank it after it partially fired and quit. The spark continued and I checked the tailpipe and could not smell raw fuel. I was told the cats had been removed and dummy o2's or some sort of fooler was used on the post cat sensors.

As for the diesel, God I hope not. Seen that in the army, gas for the diesel and diesel for the gas. Great times had by all.
 

gmcman

Member
Dec 12, 2011
4,656
BrianF said:
We had continued to crank it after it partially fired and quit. The spark continued and I checked the tailpipe and could not smell raw fuel.

Have you checked the fuel pump relay? Swap with a known good one.

Does the fuel pump energize with the key turned to ON? Should hear a click and a faint whine then whine should quit after a couple seconds. Could be a failing pump, bad relay. Among what else we have discussed.

Definitely need to verify fuel pressure.
 

BrianF

Original poster
Member
Jul 24, 2013
1,192
West central Sask.
one of the times we fiddled around with it I could hear the pump whine. I will check the relay as well. I finally started some vacation days and will source out a pressure gauge.
 

DJones

Member
Jan 21, 2012
701
St. Petersburg, Florida
Wooluf1952 said:
A dirty t-body shouldn't cause a no-start and the 5.3 doesnt have that problem, like the I6. :twocents:

The 5.3 actually sticks, so when you put it into drive, you're flying across the parking lot after it breaks free.
 

Wooluf1952

Member
Nov 20, 2011
2,663
Milwaukee, Wisconsin
DJones said:
The 5.3 actually sticks, so when you put it into drive, you're flying across the parking lot after it breaks free.


Agreed. They can all stick if not cleaned.
I was putting my daughters '96 Olds Bravada w/4.3 V6 on ramps for an oil change. I almost went up and over the ramps because of a sticking t-body.
:redface:
 

BrianF

Original poster
Member
Jul 24, 2013
1,192
West central Sask.
So she lives again. Issue came down to ecu issues. It was beyond what I normally do so another buddy checked the computer and swapped it out. It appears it was an issue relating to the theft protection (possibly) and the command start. Now that she runs its on to diagnosing the misfire and o2 problems.
 

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