LS4 starter bumping and connections. (Page 1/4)
sourmash MAY 02, 04:43 PM
With an LS4 removed from an 2008 LaCrosse, I want to now check compression. The battery cables and connections are still attached to the starter and block. At the solenoid there's only the battery cable and one violet (or purple) wire on the solenoid which attaches with a plug. This must be the solenoid triggering voltage?
The questions are, do I just apply 12V to the solenoid where that wire plugs into the solenoid? It is a full battery 12Vs that's applied there?

The car was found in a pick and pull yard wherein you can't test them, and it has no accident damage so something went wrong somewhere.
fieroguru MAY 02, 08:00 PM
Ground to the block, +12 from large jumper cable to the large threaded stud on the starter. Then use a smaller wire with an alligator clip and clip the +12 jumper cable end and touch the other terminal where the purple wire connected... make sure your hands are free from the belt and accessories.
sourmash MAY 02, 08:29 PM
Thank you. I'm going to install the battery to the cable ends because that's the only place they go (the starter and bloc), and alligator clip to the purple wire connection.

[This message has been edited by sourmash (edited 05-02-2019).]

fieroguru MAY 03, 10:29 AM
This might be helpful as well:
sourmash MAY 03, 12:25 PM
Sweet.
Here are the plugs as pulled. Grody, huh?


[This message has been edited by sourmash (edited 05-03-2019).]

sourmash MAY 03, 03:17 PM
Well, I searched the VIN and found it's a 148,000 mile engine with engine noise. It was sold at auction last year with engine noise described. I expect it's a spun rod bearing.

What's the value of an LS4 as a core? I paid $256 with all accessories; power steering pump, AC compressor and alternator.
If it just needs a crank job I'm possibly interested in doing that if affordable.

COMPRESSION TEST:
The left bank values are:
235, 220, 230, 220

Right bank values are:
235, 230, 240, 220

I don't hear any noise but it's not cranking as strongly as the one in the video either even with the plugs out. Concerned that my gauge was reading too high I took the engine to Oreillys to use theirs and it was nearly identical on the one cyl I tried. BTW, Autozone wouldn't allow me and their employee to walk to the parking lot to try one cyl without renting the tool and returning at the end of the 2 minute session it took at Oreillys.

[This message has been edited by sourmash (edited 05-03-2019).]

fieroguru MAY 03, 08:21 PM
Every LS4 is a DoD engine and it isn't uncommon for a DoD lifter to collapse.
I would pull the valve covers and see if any of the pushrods are excessively loose. If removing the valve covers doesn't reveal the issue, then pulling the pan and rod/main caps to inspect the bearings isn't hard to do either.
sourmash MAY 04, 11:01 AM
Well, you called it correctly and are making me feel much better about the buy. Number 4(?) intake is collapsed, as you can see my 1/4" extension stuck underneath the sloppy rocker.
Kudos to you for that info!
So, I'm guessing the fix is to pull heads and remove the DoD lifters? EDIT: I've seen the video of CrazedPerformance using the modded pushrod to release the lifter. Will it last if the DoD is defeated permanently?
Additionally, If I go forward with a Fiero swap I've lightly read about issues with intake replacement and DoD internals conflicting?

[This message has been edited by sourmash (edited 05-04-2019).]

fieroguru MAY 04, 01:18 PM
The best way to fix it is to eliminate DoD/AFM. I should be getting around to deleting DoD on my LS4 in the coming weeks and will detail in it my build thread. Basically pull the heads, remove the lifters and the plastic holders, install LS2/LS3/LS7 lifters and retainers,install a LS2 or LS3 valley cover, reinstall the heads. It is recommended to also replace the camshaft as the DoD lobes are a slightly different profile than the non-DoD lobes. There are a lot of cheap OEM LS1/LS2/LS3/LS9 camshafts, as well as plenty of aftermarket ones that will get you even more lift and duration.

The two interference issues with intake swaps are the:
DoD connector on the valley cover (is removed/eliminated as part of the DoD removal)
Stock Oil Pressure Sending Unit and this can be relocated out of the way

[This message has been edited by fieroguru (edited 05-04-2019).]

sourmash MAY 04, 01:50 PM
That's almost like no obstacles on the intake swap then. My learning curve needs attention since this has never been my interest. I just seem to remember from your thread maybe that there is a choke point to the intake from the throttle body. And there's the TB mounting being different as well.
Bought this to flip but have about talked myself into keeping it for now.