Car Wont Start ! Help

[maalmull]

Hey Guys

I just ported & milled (.025) 317 casting heads on my LS1. The car fired up immediately after the installation then I shut it down. next day I tried to fire it up but the car haven't started until today "its been 3 weeks now!".

Pulled the spark plugs and they are black coated (rich), cleaned them and put them back but no luck. Pulled 10% from the VE between 400-1200 RPM but nothing.

The car pulled a dtc p1516 & p1518.

I want to know if this is tuning problem or ignition/mechanical issue however the car was fine before the new setup.

Ls1 bottom end, Truck intake, 317 heads & cam 215/223 112 lsa.

any suggestions?

[joecar]

When it ran that one time, did anything happen...? Did you shut it off, or did it shut off by itself...?

Do a compression test on all cylinders.

Pull valve covers and inspect all valve stems/springs/retainers/rockers.

Did you get a bent pushrod or a failed lifter...?

Is timing chain ok (do rockers/valves respond to turning crank)...?

Do you have any intake manifold leaks...?

Are injectors leaking...?

Are you seeing correct rail pressure (does fuel pump run)...?

Are you getting firing pulses to injectors...?

Are you getting firing pulses to coils...?

Do you see RPM on scantool during cranking...?

[maalmull]

thanks for the reply Joe

I will go through these tomorrow.

so u don't think its tuning related?

[joecar]

It's hard to tell... but either way you want to first eliminate anything physical.

[cme265]

P1516:
Conditions for Setting the DTC
•The TAC module detects that the predicted and actual throttle positions are not within a calibrated range of each other.
•OR
The PCM and the TAC cannot determine throttle position.

•OR
Both throttle position (TP) sensors are invalid

•All of the above conditions are met for less than 1 second.

[cme265]

P1518
Diagnostic Aids
•DTC P1518 sets if the battery voltage is low. If the customer's concern is slow cranking or no crank because battery voltage is low, ignore DTC P1518. Clear any DTCs that may have set from the low battery voltage condition from the memory.
•DTC P1518 sets when there is a short to B+ on the TAC module ground circuit. Inspect the fuses for the circuits that are in the TAC module harness, such as the cruise, or the brake. An inspection of the fuses may lead you to the circuit that is shorted to the TAC module ground circuit.
•DTC P1518 sets if the TAC module ignition feed circuit is shorted to a B+ supply circuit. The TAC module stays powered-up when the ignition switch is turned off. When the ignition switch is turned on, the TAC module is powered-up before the PCM. DTC P1518 sets because no communication is detected by the TAC module from the PCM. Inspect related circuits for being shorted to a B+ supply circuit.
•Inspect the TAC module power and ground circuits and the TAC module/PCM serial data circuits for intermittent connections.
•Inspect the TAC module connectors for signs of water intrusion. When water intrusion occurs, multiple DTCs could be set with no DTC circuit or component conditions found during diagnostic testing.
•When the TAC module detects a problem within the TAC system, more than 1 TAC system related DTC may set. This is due to the many redundant tests that run continuously on this system. Locating and repairing 1 individual problem may correct more than 1 DTC. Keep this in mind when reviewing captured DTC info.
•For an intermittent condition, refer to Intermittent Conditions.

[cme265]

hope this helps...straight from GM diagnostics. sounds like you have a bent terminal or pinched wire

[joecar]

+1 I agree with cme265, DTC's indicate TAC modules, follow what cme265 said.

[maalmull]

Thanks guys I will have a look at the TAC connectors, harness & ground circuit


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[edwardzracing]

Make sure all those stupid and frustrating ground wires are good and tight on the back of the driver's side head. If all you did was a port job and slight milling; I can't see the tune being way different at idle. Certainly not 10% VE different. Good luck. Keep us posted.

[maalmull]

Found out it’s a ground thanks all.