No vacumm at all

barnyardmac

Registered Member
Original poster
Sep 22, 2022
11
61103
Got trailblazer 4.2 on trade running on 2 cylinders,did tuneup,replaced VVT, has no Cadillac converter, $173,000 MI went to start it tried to start it backfired hasn't started since or even tried no vacuum at all could it be timing chain slipped off intake cam because I can see the exhaust cam turning through the oil fill cap anyone got any suggestions
 

TollKeeper

Guru
Dec 3, 2011
7,159
Brighton, CO
If it was off either of the timing chain sprockets, it wouldnt turn the other from the slack in the chain.
 
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azswiss

Hobbyist
May 23, 2021
534
Tempe, AZ
How did you determine there is no vacuum?

Edit: If there is no vacuum then there is no way to get air/fuel mix into the cylinders => no start/run.
 
Last edited:

Mooseman

Master Blaster
Moderator
Dec 4, 2011
23,291
Ottawa, ON
It could be the VVT camp phaser that's permanently retarded. I know that if it's idling and you retard it manually with the Tech 2, the engine wants to stall. If you remove the valve cover, you can check the timing chain marks on the cam sprockets but not on the crank. Also check the chain tension for a failed tensioner. Before all this, do a compression test.
 

Mooseman

Master Blaster
Moderator
Dec 4, 2011
23,291
Ottawa, ON
Or maybe the VVT cam sprocket was installed off a tooth?
 

Joe_67

Registered Member
Aug 9, 2022
56
Central Virginia
It would be really nice to have some backstory (even if there isn't much of one). But at the very least, how do you know if there's no vacuum? If you know how to use a vacuum gauge, AND you are using one while cranking the engine AND you have no vacuum AT ALL (not even twitches on the gauge), the you have no compression.

So like Mooseman said, check the compression. Then, I suppose, if you want to take an incremental an cautious approach, tear down the front and see if you have a totally hosed timing chain/system. But it could be far worse...
 

barnyardmac

Registered Member
Original poster
Sep 22, 2022
11
61103
If it was off either of the timing chain sprockets, it wouldnt turn the other from the slack in the chain.
OK so here is how I got it ,it was running on 2 cylinders when I got it, the person I got it from ran it like that for a year like that around town,it ran out of gas setting on the street,before I put gas back in it I replaced,plugs,VVT Accuator it was leaking oil out the connector,put gas in it tried to start it ,it tried a few times the it back fired on me,that's why I thought it slipped of the intake cam,but you said it would have broken chain? Guess I have to start from scratch what would be your suggestion of where to start?
 

barnyardmac

Registered Member
Original poster
Sep 22, 2022
11
61103
It could be the VVT camp phaser that's permanently retarded. I know that if it's idling and you retard it manually with the Tech 2, the engine wants to stall. If you remove the valve cover, you can check the timing chain marks on the cam sprockets but not on the crank. Also check the chain tension for a failed tensioner. Before all this, do a compression test.
I replaced VVT it was leaking at connection
 

barnyardmac

Registered Member
Original poster
Sep 22, 2022
11
61103
It would be really nice to have some backstory (even if there isn't much of one). But at the very least, how do you know if there's no vacuum? If you know how to use a vacuum gauge, AND you are using one while cranking the engine AND you have no vacuum AT ALL (not even twitches on the gauge), the you have no compression.

So like Mooseman said, check the compression. Then, I suppose, if you want to take an incremental an cautious approach, tear down the front and see if you have a totally hosed timing chain/system. But it could be far worse...
The casing around the timing chain is all intact when I bought the truck it was running on two cylinders, they had ran it for a year like that when I got it it said on the street and ran out of gas before I put gas in it I replaced all the plugs put a VVT cam actuator on it it was leaking it's electrical connection then I put gas in it turned it over a couple of times it tried to start then it backfired and it hasn't hit a lick sense I took the vacuum hose off of the brake booster to check vacuum I put my thumb over it there's no vacuum at all
 

barnyardmac

Registered Member
Original poster
Sep 22, 2022
11
61103
How did you determine there is no vacuum?

Edit: If there is no vacuum then there is no way to get air/fuel mix into the cylinders => no start/run.
Okay so if there's no compression it's destined for the Boneyard I ain't got money to put in it right now and I ain't got nowhere to put it until I do have money
 

christo829

Platinum Donor
Dec 7, 2011
441
Fairfax, Virginia
Did you replace the coils when you replaced the plugs, and use the AC Delco 41-103 plugs?

If the previous owner ran it that long on 2 cylinders, no telling what's clogged up in there, but definitely check compression.
 
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TollKeeper

Guru
Dec 3, 2011
7,159
Brighton, CO
I personally think he needs to start by removing the bank one O2 sensor. He mentions that the prior owner drove for a long time on a misfire, which is a hugely big no no. If the exhaust is completely clogged, no exhaust, no vacuum can exist.
 

barnyardmac

Registered Member
Original poster
Sep 22, 2022
11
61103
I personally think he needs to start by removing the bank one O2 sensor. He mentions that the prior owner drove for a long time on a misfire, which is a hugely big no no. If the exhaust is completely clogged, no exhaust, no vacuum can exist.
I'll check it tollkeeper I'm sure it's clogged a little,but like I said before it tried to start it backfired and it hasn't hit a link since
 

barnyardmac

Registered Member
Original poster
Sep 22, 2022
11
61103
Did you replace the coils when you replaced the plugs, and use the AC Delco 41-103 plugs?

If the previous owner ran it that long on 2 cylinders, no telling what's clogged up in there, but definitely check compression.
Replaced plugs not coils,replaced
VVT actuator, crank sensor ok, cam sensor not sure but going to replace,and 02 sensor also when I have time
 

barnyardmac

Registered Member
Original poster
Sep 22, 2022
11
61103
Did you replace the coils when you replaced the plugs, and use the AC Delco 41-103 plugs?

If the previous owner ran it that long on 2 cylinders, no telling what's clogged up in there, but definitely check compression.
Haven't had time to check the compression yet got other minor things to do before I get back to work on the truck, I'll let you all know what I come up with when I get back to it thanks again for all of the possibilities
 

Mooseman

Master Blaster
Moderator
Dec 4, 2011
23,291
Ottawa, ON
I replaced VVT it was leaking at connection
That is the CPAS (Camshaft Position Actuator Solenoid) you repalced. The VVT is the variable cam sprocket, or cam phaser, controlled by the CPAS.

You have to do a compression test before moving forward with anything. The engine's mechanical health has to be confirmed.
 

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