Ronnie_W

I have no codes that would affect starting. The coupe of codes I have are ones that have been there for a while, ebcm and sdm. No critical codes on the DIC, efilive or the Tech 2.

I checked cam and crank position sensors. They look good. I manually turned the engine while checking voltage. They both gave me voltage and no voltage as I turned the engine over. I get a rpm reading on my efilive while cranking. I have fuel.

I removed the star connector shorting bar on the one with the 4 wires and still no start.

I have tried 2 different batteries. I try to keep them charged as I go and sometime use the start function on my big battery charger.

I have fire from the coils, and my noid light on injector connectors for 2-3 revolutions and then the spark is very weak and the noid light is very weak while cranking.

My battery voltage will drop from 12.5v or so down to 9.xx volts while cranking. Seems like a large drop to me.

I have tried another ecm, tac module, cam ps, and app. I also replaced the ignition switch.

I have check all power connections and ground connections.

That's all I can think of right now.

C5 Diag

Yes !!... a 3 volt plus is a huge voltage drop...that is why your spark and injector pulse are weak...was this done while cranking while checking across the battery terminals ??...make sure battery connections are clean and tight !!...you need to check the voltage drop across the positive and negative side of the battery...positive lead of the muti meter on battery positive and negative lead to the B+ side of the positive battery terminal at the starter...connect the lead to the STUD while cranking...do the same thing on the ground side....positive lead to battery negative and negative lead to starter motor case...a .3 volt drop or less is good...a .2 volt drop on ther positive side is good !!....is this how you checked all your power and ground connections ??...visual inspection is not good enough !!

bighank

Had crank no start. Also had code P1518 pointing to the TAC. Checked all wires from Accelerator to TAC to PCM, TB motor, TPS.. Checked almost new battery, Replaced TAC, Still no start.
Finally replaced Ignition Switch. Car started immediately and no longer had P1518 code. Low voltage caused by bad contacts can cause many problems. I just replaced the rear electrical part of the Ignition Switch as the lock cylinder and VATS sensor was OK. Lock cylinder is removed with key in the on position using a screwdriver pressing the release tang.

Ronnie_W

I will do this in a bit when I can get back out to the garage. Thanks

Ronnie_W

I forgot to mention that I have replaced the switch already. Thanks.

C5 Diag

Now is the engine cranking over normally or will only crank for a little bit and then not crank ??...I'm thinking with a 3 volt loss the engine shouldn't even crank over !!....where did you measure this voltage drop ??....is your fuel pressure good ??....HAS YOUR BATTERY BEEN LOAD TESTED ??....I shouldn't assume that it was checked !!

Ronnie_W

The battery that is in there now has not been load tested. The red top optima has been and they said it was good. I didn't trust them them so I put in another battery that has very little run time on it. It seems to crank over a little slower than usual, but every once in a while it will speed up to normal for a very short time. The batteries don't keep enough charge for very long to turn it over. Fuel pressure is good. I measured the voltage drop at the battery feed, at the hot terminal feeding the fuse box and at the injector plugs. I did the test you laid out for me. The positive test read 1.62 volts and the negative test read .66 or so (some fluctuation). I did not have time to start testing the cables. I'll check that out tomorrow. Thanks for your help so far.

C5 Diag

Hi !!...just trying to figure out what test you were doing ??..,.you said you checked between the fuse box feed and the injector plugs ??...you’re talking about the fuel injectors ?...don’t know about the “negative test” you were referring to (.66v)....I thought you would just do a voltage drop check on the positive side and ground side of the battery...thanks !!... good video on starting circuit voltage drop testing !!

Ronnie_W

Sorry to make my reply confusing. I did do the voltage drop test and .66v was the result of the negative test, battery negative terminal to starter frame. The 1.62v was the result of the positive side test, battery positive terminal to starter B+ bolt.

The other part of my post was referring to your question of where I was testing and saw the 3v drop while cranking.

C5 Diag

YIKES !!...looks like your voltage drop on both sides are excessive... max of .2v on the negative and .5v ( being generous)on the positive !!...looks like you need to get underneath the car and clean up both ends of each battery cable and retest !!...I usually go to the stud first on the B+ side !!

Ronnie_W

I'll be on it tomorrow and hope this leads to my engine starting. Thanks again.