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I have been trying to work through my starting issue as I had in another thread. My grounds checked out with the exception of one near the starter. There are two ring terminals that go together and the smaller one that doesnt have the tab measure 6 or 7 volts as I screwed them independently in the block to check. This was measuring voltage, one on the positive terminal and using the negative to confirm voltage at the ground locations. With both of them screwed in, it measured like 12 V at that grounding location. Next, I disconnected the battery and measured resistance back to the battery. The larger ring terminal was 47 ohms. The larger was like 22k ohms. It isnt open but think this could be my issue. I ran a independent ground from the starter to the battery and it was closer to turning over as I tucked the ground underneath the head of the starter bolt. I only had a 10 gage. What size ground should this be size? 6 or 8? Just curious. As mentioned in a previous thread. I removed the starter and it tested out. No other electrical issues experienced.
Question 1- Does anyone know what circuit that smaller ground grounds? I cut that ring terminal off just to see if it was a defect at the terminal. Nope.
Question 2- Has anyone ever run a independent ground to the starter?
First thing resistance is NOT the way to check grounds…loaded circuit voltage drop testing is…if you are having starting issues have you checked G303 which is the engine block ground ??…if you have a 12 volt incandescent test light connect it to battery ground and probe a clean spot on the engine (you may need a long extension wire) while attempting to start the car…the test light should NOT light…you can also if you have some jumper leads I’d connect one of the jumper leads if a thicker gauge or both to battery ground and the other lead or leads to a clean spot on the battery…see if the car starts…No need to an independent ground to the starter…the engine block is your starter ground so all current from the starter goes through the engine block to G303 and then through the negative battery cable to ground…if that current doesn’t get back to the battery that is why the test light illuminates.
I will check that. G303 is the stud that the negative battery cable connects to? I had my engine out and did the ground ohm just to confirm something didnt get broken or pinched during install. Looking at the diagram the two grounds on the passenger side of the block are the ECM and the starter relay coil? If I use the tester light and the block lights up, How is the engine grounded to that stud G303?
Yes, G303 is your ground for the battery negative terminal…and as I mentioned ohm checking grounds is really not the right way to check grounds…loaded circuit testing is…if for instance let’s say your battery negative cable has 100 strands of copper wire…if all but a few were broken you would still show continuity but the thing a lot of folks don’t really comprehend is that the current from the starter has to pass through the engine block and then through the right frame rail where I assume G303 goes to has to find it’s way back to battery negative from the negative battery cable…a few strands of the copper wire won’t allow the car to start with a BIG voltage drop but probably just burn up…having a battery in the trunk and not having your battery ground going to the frame rail instead of the engine block makes proper grounding of the car more difficult…also I don’t know if GM uses any “ground straps” in the ground circuit…didn’t know you had the engine out because that is important info we would need to know…as far as your question about engine grounding I’m assuming that the ground goes from the engine block then to the motor mounts and then to the frame rail ??…you can try connecting your jumper cable from the engine block to the right frame rail somewhere and see if the car starts…if you have the voltmeter connect one lead to a clean spot on the engine block and the other lead to a clean spot on the right frame rail… now attempt to start the car…now read the voltmeter as the car is attempting to start…you will be reading the “voltage drop” between those 2 points…if the voltmeter reads 7 volts that means 7 volts is dropping between those points and only 5 volts is getting back to the battery…with that big of a voltage drop the car will NOT start.
Thanks. I didn’t loosen the negative cable for the G303 but I may see if I can trace it on the underside. I have some ground straps on the way just in case. It is frustrating to literally have everything work as expected expect the starter which seems like the easiest of them all.
The metal positive strip that runs through the front fuse box snapped when I was removing it so I purchased a junk yard replacement fuse box. Tested a brand new fuse box and confirmed it was that. I am just working through a list of stuff that I thought it could be.
it isn’t the most complicated circuit in the world but it is being a booger for me for whatever reason. The lack of a ground on the starter is the issue. The motor mounts have rubber so I don’t believe they allow the engine to be grounded through them. I could be wrong.
I would just do either the test light method or voltmeter method just to confirm…takes 5 seconds to do so you won’t be going down a rabbit hole with this !!…there may be a big ground strap that goes from the engine block to frame rail and it’s pretty certain G303 attached to the frame rail.
The neg battery cable connects to the passenger side frame rail at G303.
The driver side of the block (G109) is grounded to the driver side frame rail (G103). This is the connection that the starter current flows through, back to the battery neg terminal.
Last edited by ersatz928; Sep 6, 2023 at 09:20 AM.
Here is a stupid question. I installed my catch can on one of the grounding straps in the last picture. I will relocated it and see if that helps. I work long days and nights so I probably wont have a answer till this weekend. I wasnt also sure where the actual ground on the engine went on the block and didnt have it in that exact hole.
It is finally cooling down enough now that I can work on the car for a period of time without heat rash. lol
My silly question is, isnt that where most people mount their catch cans on one of those two bolts?
I had mounted it on that same bolt as circled without a problem. Then I read about a few guys that did have issues, so I just moved both grounds to the non-circled bolt and never had a problem. But it's worth a look since it's something you added to the equation - never know.
The rearmost bolt is for the block ground.
The forward bolt is for the Power Steering rack ground.
As long as you have metal-to-metal contact, and a tight bolt, it does not matter where you mount your catch-can. But people were having some issues because the catch can bracket was painted, and did not provide good metal-to-metal contact.
I had my engine ground on a machined spot on the front of the block rather than the one in the picture. I didn’t have my catch can mounted there on the frame side like I thought. I got so hung up on the grounds near the starter, I didn’t look anywhere else. Put my starter and all back together and kicked right over. Ran to get some new fuel for it and fire tonight.
Thank you. Cut the hood yesterday. Not sure if I will leave as is or do a cowl.
For puttering around, I'd leave it as is. Assuming you plan to use it in anger, I'd put a cowl on it. I'm willing to bet that over 100mph you'll see some hood flex/flutter (unless you've added some hidden reinforcements). With no added bracing and enough runs the hood will fracture or even worse, break apart. Might not be the 1st run or even the 10th run....but it'll happen.
Engine grounding
