My 99 silverado 5.3L wont start or run

10

Asked by Feb 14, 2016 at 01:02 PM about the 1999 Chevrolet Silverado 1500 3 Dr LS 4WD Extended Cab LB

Question type: Maintenance & Repair

I took the rails off and witnessed injectors spraying, I took every plug and watched it spark. I checked compression cold (I have no choice), and I have 30 PSI each cylinder! I thought the only way all cylinders would loose compression at the same time is if I lost timing...opened up timing case and the gears marks are aligned. Is it possible that my gears could have jumped 180 degrees out of time? would I even get compression cold?

10 Answers

86,775

Cold compression will be somewhat different but in your case with 30 lbs it would not matter, and yes for all cylinders to loose compression is either timing, complete head failures, or burned through pistons but that would be caused by sustained preignition or pinging, there is another possiblity, is the valve train, you may want to check the rocker arm throw, there is such a thing as a broken camshaft. HTH

1 out of 1 people think this is helpful.
Best Answer
10

Just to make sure as I check timing...I should have compression building on #1 cylinder as the timing mark align, right?

10

Would compression be low on all cylinders if the lifters weren't pressed up? If the camshaft was broke wouldn't I have different compression pressures on each of the cylinders? Some with none, some with some...

86,775

To answer your the compression question, by the time the piston has reached TDC the maximum pressure will have been reached. If the cam broke just before the number 1 cylinder and was in the correct spot that would put the exact same pressure on each lifter to hold each valve open exactly the same amount, it could be that way but normally you would be right some cylinders will be high and others low. I have heard in a few instances that the oil pressure can get high enough that it pumps up the lifters and hold the valves open slightly, so that might be something else to check.

61,075

Ignition timing and valve timing are different. With only 30 PSI in all cylinders it's either jumped timing (most likely) or the valves are stuck open on all cylinders simultaneously (unlikely). HTH. -Jim

1 out of 1 people think this is helpful.
10

Thank you so much for the help...I changed to different compression gage, believing that mine may be wrong. The pressure was higher (80psi) the new gage is even older but has way higher reading. I put oil in the cylinder as well, and there was no pressure difference. When I rotate the engine by hand, I begin Building pressure at about 180 degrees, on the camshaft, before the timing marks align. This doesn't seem right to me but maybe it is. When I pass trough where the marks align Ive well passed compression and power (where I'm drawing a little vacuum).

86,775

That is about right, you will start building pressure just as the piston starts to move up on the compression stroke. However even 80 lbs is still very low. When the piston reaches TDC that is as high as the compression will get then you are in the power stroke and the piston heads down then back up for the exhaust stroke then just a few degrees before TDC on the exhaust stroke the intake valve will start to open just as the exhaust valve starts to close and you then are on the intake stroke and it starts all over again. So there is a spot where both of the valves are open at the same time, and this is what they call valve overlap, now there is what they call valve duration, and that is how long each valve is open for, and then there is valve lift and that is how deep or wide the valve is open at full rocker depress. Now your totally confused, right?

10

Yes I am, because it's seems my timing marks are aligned with the #1 cylinder at the top of the exhaust stroke. Perhaps for my engine 99 silverado 5.3 liter that is correct...but I don't know. Regardless the timing marks are aligned correctly, Camshaft timing mark at 6 o'clock and crankshaft mark at 12 o'clock so that the marks point at eachother. Thank you for your help, I'm walking away for a while because my head is spinning :)

1 out of 1 people think this is helpful.
86,775

Maybe this will help you understand GM's wired way of timing the cam. See pic.

61,075

Older Cadillac engines were like that as well. #1 is at top dead center (TDC) with the cam dimple and the crank dimple both at 12 o'clock. HTH. -Jim

Your Answer

Add photo

Related Questions

  • 1993 chev silverado wont start. i changed fuel pump relay and fuses 1 answer

    the fuel pump will run but truck wont start. 1993 chev Silverado,

    Chevrolet Silverado 1500

    -

    Maintenance & Repair

  • hard start when warmed up 99 silverado 5.3 15 answers

    MY SILVERADO PICKUP STARTS GREAT WHEN COLD BUT WILL NOT START WITH OUT CRANKING FOR PROBABLY AROUND 6 SECONDS. SOMETIMES MORE AND SOMETIMES LESS. IT WILL START BACK UP EASILY RIGHT AFTER YOU SHUT IT O...

    1999 Chevrolet Silverado 1500 3 Dr LS Extended Cab SB

    -

    Maintenance & Repair

  • Motor 1 answer

    Will a 2008 5.3L fit an work in my 2000 Silverado with a 4.8 L without any problems?

    2000 Chevrolet Silverado 1500 Ext Cab Short Bed 2WD

    -

    Maintenance & Repair

  • 2002 Chevy Silverado 1500 with 5.3L with low oil pressure 5 answers

    We have a Chevy Silverado 1500. At start up the oil pressure is at 40.. by the time it warms up, it has dropped to just under 20. It sounds completely normal. No knocking or anything. If you go drive ...

    2002 Chevrolet Silverado 1500 Ext Cab Short Bed 4WD

    -

    Maintenance & Repair

  • 99 silverado start up problem 5 answers

    i have a 99 chevy silverado 1500 2wd 4.3, ive been having problems with it recently concerning the crank. i would crank the truck up it seems to get a push to start up but immediately turns back off...

    1999 Chevrolet Silverado 1500

    -

    General

Silverado 1500

Looking for a Used Silverado 1500 in your area?

CarGurus has 155,163 nationwide Silverado 1500 listings starting at $1,395.

ZIP:

Search Chevrolet Silverado 1500 Questions

Chevrolet Silverado 1500 Experts

#1 John Carson
John Carson
Reputation 1,830
#2 Silverado_owner_2006
Silverado_owner_2006
Reputation 1,530
#3 Rowefast
Rowefast
Reputation 1,510
View All

Related Models For Sale

Used GMC Sierra 1500
941 Great Deals out of 62,271 listings starting at $1,395
Used Ford F-150
2,702 Great Deals out of 211,804 listings starting at $1,000
Used Dodge Ram 1500
530 Great Deals out of 12,828 listings starting at $1,995
Used Toyota Tundra
588 Great Deals out of 30,722 listings starting at $2,637
Used Toyota Tacoma
620 Great Deals out of 35,105 listings starting at $2,155
Used Chevrolet Tahoe
778 Great Deals out of 28,448 listings starting at $1,500
Used Chevrolet Camaro
282 Great Deals out of 38,302 listings starting at $1,250
Used Ford F-250 Super Duty
397 Great Deals out of 45,060 listings starting at $2,000
Used Chevrolet Silverado 2500
10 Great Deals out of 317 listings starting at $3,995
Used Ford Mustang
364 Great Deals out of 44,400 listings starting at $1,000

Used Cars For Sale

2017 Chevrolet Silverado 1500 For Sale
28 Great Deals out of 95,466 listings starting at $16,928
2016 Chevrolet Silverado 1500 For Sale
249 Great Deals out of 8,006 listings starting at $16,375
2015 Chevrolet Silverado 1500 For Sale
240 Great Deals out of 7,129 listings starting at $15,977
2014 Chevrolet Silverado 1500 For Sale
402 Great Deals out of 10,942 listings starting at $6,990
2013 Chevrolet Silverado 1500 For Sale
226 Great Deals out of 5,931 listings starting at $8,495