crazynights

iTrader: (3)

I moved my battery to the back of the car and now having very slow cranking. The battery was tested and passed. Optima Red Top with 800CCA. Tested at 780CCA
Grounds are as follows. One ground (1 gauge) off the battery to a cut off switch. Then off the other side of cut off and bolted to the rear frame rail. I attached another ground wire (1 gauge) to the bolt of the frame rail to the rear bolt on the back of the head. Lastly a ground (4 gauge) from the block to the K member.
Positive (1 gauge) goes to a remote solenoid and then to a TCI High Torque starter.
Never had any issue when battery was up front. I'm leaning towards grounds but unsure if this is the true cause. All grounds are bolts to bare metal. All cables are welding cable. Not the cable that was included with kit.
Any ideas? Thanks.

dlinger

iTrader: (4)

Does it make a difference if it is cold start or hot start? With that many grounds, I would not think that is an issue except I don't understand ground to cut off switch. I run the hot wire to mine (Moroso). Maybe by pass switch temp. Do you have shut down relay for alternator? Since you installed remote solenoid, did it have an issue with hot starts?

When I first installed my battery in trunk (75 Nova), cold start was very slow turning. I did not have the ground strap from valve cover to firewall hooked up. I installed it and it turned over normal on cold starts. Then I had to years of hot start issues.

crazynights

iTrader: (3)

No, basically does the same on hot starts. Maybe a little easier, but nothing drastic between the two to make a difference.

I may do a ground to the front frame instead of k member. Should one be installed from the block to firewall?

Starter is also fairly new also.

TTOP350

iTrader: (8)

With the engine running, the alt may keep the car running even if you turn off the ground switch.
I run the ground (00 fine strand) from battery to the bellhousing bolt and also a small ground to the body from the battery.

OrangeBird

iTrader: (1)

Don't most folks who do a trunk mounted battery use something like 0 or 00 instead of 1 gauge ? And have you tried it without the switch to see if that's where your loosing power ?

If you take a voltmeter and put one lead to the positive battery post and the other to the big stud on the starter where the battery's + wire connects to it , and then crank the engine , any appreciable volt reading indicates the loss is in your positive cable . Then do the same for the negative , put one on the battery's - post and the other lead right to the frame of the starter motor itself and crank the engine , any appreciable voltage reading then indicating you loosing it on the negative side . And if BOTH sides show appreciable loss , that will mean that your cables are indeed to small to pass the current required . I know you will need to extend the length of one of the meter's test leads since your battery is in the trunk , but any ol hunk of speaker wire will do since we're measuring voltage here . Remember , as you increase the length of your starter cables , the thickness must increase exponentially if your to see the same current at the starter as the shorter cables could deliver .

PS , since Destroyer was arguably the best KISS album of all time , How come ya ain't got that as your avatar ?

crazynights

iTrader: (3)

That's a good idea. I'll bypass the cutoff to test to see if that is the reason. Then will try those other tests you stated. What is a appreciable? For example should I look for a specific number?

As far as gauge thickness, I didn't think 1 gauge would be a problem. I can look into 0 and 00 gauge.

So my grounds seem sufficient. Just need to see where the voltage loss may be.

I'll test and post my results.

I do dig Destroyer, but the first record is what started it for me so it holds a certain nostalgic value.

Lurbie

iTrader: (3)

What OrangeBird is describing is called a voltage drop test and you should do that first. It is quick simple and tells you what, and where,the problem is. A general rule of thumb for most voltage dropping tests is less than 0.5VDC, HOWEVER, you're running quite a long length of wire, so you might see 2.0 VDC from battery to starter and be ok in this instance. (5th Gen Camaros have that much.) If you have 3V or more, you have found a concern, but because large gauge wire is crazy expensive try using a high quality jumper cable across the suspect circuit in parallel with that circuit. If your problem doesn't exist with the jumper cable connected in parallel over the suspect circuit, then you know that you need larger wiring. Keep in mind the voltage drop test is a great way to confirm proper connections too. When measuring connections, like ring terminal to frame, that's where you should see less than 0.5 VDC.

sofakingdom

iTrader: (1)

Cables from batt should go:

Pos to starter solenoid
Neg to BLOCK (NOT "frame", NOT "chassis", NOT NOT NOT NOT NOT... needs to go to BLOCK)

That's your malfunction.

Run your 1 ga. neg cable to THE BLOCK. Then, at the BLOCK end (give or take), connect the BLOCK to the "rest of the car" aka "chassis", "frame", etc.

If ya wanna see where your "voltage loss" is, put one meter lead on the neg batt terminal, the other on THE BLOCK.

Rule #1 of wiring:

PUT THE COPPER WHERE THE CURRENT IS.

When starting, that means, from the batt to the starter on the pos side, and from THE BLOCK to the neg terminal of the batt. That's where the copper needs to go.

crazynights

iTrader: (3)

Thank you for the tips. Will do the voltage test. Seems like a simple test.

Sofa, thank you. I have a ground wire from the cut off switch to the bolted to the rear frame. On that same bolt, I have a 1 gauge wire going to the rear head of the block. Are you suggesting to just have it run to the block without having any to the rear frame? Also, should I remove it off the head and bolt it somewhere else?

Appreciate it.

redneckjoe

i'd try running a jumper cable from one side of the cut off switch to the other. might be a bad/whimpy switch?

TTOP350

iTrader: (8)

Crazynights

Have you had the car running and then tried to shut it off with the switch?

crazynights

iTrader: (3)

RedNeckJoe: That's a good idea. I'll try that. It may be a switch going south. It's been on the car for about 15 years.

TTtop: No, I haven't tried that. If it stayed running, any idea what that would do with my slow cranking?

TTOP350

iTrader: (8)

Not 100% for sure but I have a few ideas and I know it won't pass tech if it stays running. (if that's what you are doing it for)
You may be spending time on a problem that won't be there if you have to rewire the car with the switch on the positive side.

dlinger

iTrader: (4)

I have always seen shut off wired with positive cable. It will stay running as your alternator will keep power to car. You need a shut down relay installed. I would still think that would be true by switching negative, especially since you have more than one ground installed. First thing I would do is by pass switch. I would also check all the lugs to make sure they are getting good connections.

As Sofa recommended ground from battery to block. Unibody, rubber engine mounts, painted bolts, etc can cause loss. Not saying it won't work as trunk kits come with a 2' ground strap.

Tibo

iTrader: (15)

There was a thread on this a little while ago, Sofa and I disagreed on the need of having a ground from battery to block. If everything is grounded with proper gauge there shouldn't be a need to run that ground cable. Then if you have subframe connectors I think the argument against a long ground wire is bolstered. But everything grounded means grounding the heads together and one head to the firewall or both heads to the firewall or frame, grounding the engine to the "frame," grounding the K member to the frame, battery negative to floor pan and preferably both frame rails. Lots of people make the mistake of only grounding one head and not grounding their engine block. Head bolts have the sealant that inhibits good grounding to the block.

The guy in this video has also written one of the an electrical wiring books I own, he makes the case for not needing to run a ground cable.
https://www.google.com/url?sa=t&rct=...ijyaNc1sAyAdBg

crazynights

iTrader: (3)

Update: Bypassed the switch. No change. I checked ohm readings as well. Seems to be good. No drastic change. Just need to get some additional wire to try the positive post to the starter positive.

Also, got a price on some 2/0 cable. However, my buddy says 2/0 is smaller than my 1 gauge. I told him he is thinking of just 2 gauge. This is 2/0. Good question though, what makes the "0"? That stating maybe negative 2?

dlinger

iTrader: (4)

#2 is smaller and less amperage than #1. #3 is smaller and less amperage than #2 and etc. 1/0 (1 aught) is larger than #1. 2/0 is larger than 1/0. After 4/0 it is starts at MCM.

https://en.wikipedia.org/wiki/American_wire_gauge

Tibo

iTrader: (15)

Have you made sure that your cable is the gauge that it is labeled? Many companies are making wire and claiming it to be a certain gauge but in reality it is 1-2 sizes smaller.

sofakingdom

iTrader: (1)

http://www.engineersedge.com/copper_wire.htm

Wire gauges are logarithmic. The base size is 0 gauge, which is 324.82 mils (.32482") in dia. This makes the cross-sectional area of 0 ga. just over .1 sq in, or 100,000 circular mils. There is an actual formula that makes it easy to calculate the diameter of any gauge:

324.82 * e ^ (-0.115929 * gauge)

Cross-sectional area can be calculated the usual way; pi * (dia ^ 2) / 4. If 0 ga. is a bit over 100,000 circular mils, then 4-0 is a bit larger than 200,000 circular mils, or equivalent to 200 mcm. Then once one gets to that size, the "trade" sizes commonly available above that are usually 500 mcm and 1000 mcm. "Wire" larger than 1000 mcm is rarely used as it kinda quits being "wire" and starts being more like bar stock.

Since it's logarithmic, the cross-sectional area (and weight, and current-carrying capacity, at DC anyway... AC is considerably more complex because of skin effect) doubles approximately every 3 gauges. E.g. 2 ga. is just about twice the CSA of 5 ga., and therefore about twice the capacity. Capacity is limited by heat generation and voltage drop; either of those 2 factors might be the dominant one in a specific application. Area decreases as the gauge number increases from 0; 2-0 through 4-0 are progressively larger than 0, with 4-0 being just about twice as large as 0.

You won't be able to "measure" the resistance with an ohmmeter.

Wire it like I said, which is, PUT THE COPPER WHERE THE CURRENT GOES. Pos term of batt to big post on starter, neg term of batt straight to the BLOCK (since that's where the starting current goes...). Short jumper between the block and the chassis such as the firewall, to carry the MUCH SMALLER current involved with the car's electrical system. Fusible links to the remainder of the electrical system to the big post on the starter along with the batt cable. Alternator big post to the big starter post also, via a #8 or at least #10 wire with its own fusible link.

Yes my employment is as an electrical & electronic engineer. Yes I clearly understand electricity. No I do not need "magazine articles" or "videos" to tell me how electricity works: I do it daily for a living.

Tibo

iTrader: (15)

My apologies if I offended you.

QwkTrip

iTrader: (22)

Starter motors are high current devices that are very sensitive to resistance in the motor cranking circuit. You need to make sure you have very good connections in the current path of the starter, positive and negative runs. The correct resistance of the entire circuit (battery positive to battery negative) is on the order of 0.0015 Ohms and that is too low to measure with a hand-held multimeter.


Follow advice that sofakingdom gave and you will find the problem. The starter is case grounded so it is depending on a clean, metal to metal, contact to the engine block AND ground the engine block back to battery. If the starter happens to have a ground stud (unusual in that size starter) then use it.

crazynights

iTrader: (3)

Great tips. I will redo the ground from the negative right to the block and ensure all connections are 100%.
I will also re-look at my positive set up. I have it connected to a remote solenoid so will ensure that's all good.
However, Sofa made a great point (as usual) to run the negative right to the block, maybe even to the starter bolt (may be a better ground contact)
Will make these changes and post my results.
Thank you everyone for the ideas and tops.

QwkTrip

iTrader: (22)

Don't put a ring terminal under the starter mounting bolt. The ring terminal is made of a soft material and will allow the bolted joint to relax and bolt will loosen over time.

Tibo

iTrader: (15)

I'm still skeptical that a 1 gauge cable is going to be a better option than a well grounded chassis. I read Sofa's remark and tried to read more about grounding. I checked out the electrical engineering message board over at electronics.stackexchange.com which is billed as "...a question and answer site for electronics and electrical engineering professionals, students, and enthusiasts." The searches I did over there didn't reveal members abdicating for long lengths of thick grounding cable.

The cliff notes version is for shorter distances (for grounding applications) thicker copper cables work better because they have less resistance than the metal in the chassis. When the length starts to increase (in the case of trunk relocations) is when the chassis becomes the preferred ground because it will have less resistance due to the increase in cross sectional area.

Directly from http://www.w8ji.com/negative_lead_to_battery.htm which was referenced on the electronics.stackexchange boards:

"Example of ground path resistance:
Resistance of any uniform conductor is inversely proportional to cross sectional area and directly proportional to resistivity and length. In simple words, if we double the cross sectional area of a conductor we cut resistance (and voltage drop) in half. If we double the length, we double the resistance and double the voltage drop.

A number 1 AWG copper wire has an effective diameter of about 0.3 inches. Area of a circle is pi*r squared. This wire would have a cross sectional area of about pi*.15*.15 = .071 square inches.

Let's assume a steel body shell is about 16 gauge, or about .06 inches thick. A one foot wide area would have 12* .06 = .72 square inches of cross sectional area. The physical cross section is about ten times larger than the copper wire's cross sectional area.

The resistivity of steel is about 15 ohms per 10-6 cm. The resistivity of copper is 1.7 ohms per 10-6 cm. We can reasonably assume steel has about 15/1.7 = 8.8 times the resistance of copper for the same length and same cross sectional area. While the body shell has higher resistivity material, the body also has much greater cross sectional area.

This means a one foot wide length of steel body shell, if that shell is only .06 inches thick, has about 10% less resistance than an equal path length through out copper wire. It's easy to see why a ground path through the car body, which likely is several feet wide and much thicker in many areas, is a small fraction of the resistance of a copper wire.

A four foot wide area of floor pan, just .06 inches in thickness, would have a cross section of about 2.88 square inches. The equivalent copper conductor would have to be 2.88/8.8 = .327 square inches, or a diameter = 2* sqrt of A/pi, or .645 inches diameter! Equaling the resistance of a thin 4-foot wide steel floor pan with a copper cable requires a cable larger than 4/0 , and we have not even counted the help from frame rails, rocker panels, or roof paths!"

More from that site:
http://www.w8ji.com/negative_lead_to_battery.htm
http://www.w8ji.com/battery_wiring.h...unted_battery:
http://www.w8ji.com/mobile_ground.htm

From what I've read if running a thick grounding cable the length of your car cures your problem then you probably were using bad grounds in the rear of the car or have bad grounds up front in the engine bay area.

As far as the not being able to measure resistance with an ohm meter remark all I could find on that was that if resistance was under 1 ohm it is most accurately measured with a Kelvin sensing technique or a Kelvin Bridge.

sofakingdom

iTrader: (1)

How much is that cross-sectional area reduced when it reaches the joints where the chassis pieces are held together by a handful of spot welds? How many of those spot welds are broken in his car?

How much additional unnecessary resistance, how many new intermittents, how much unreliability is introduced by the extra connections? (cable ends etc.)

PUT THE COPPER WHERE THE CURRENT GOES. It's so simple, so logical, so un-web-site-ly, so un-video-ly, it almost hurts.

You are correct, a 4-wire ohmmeter (aka Kelvin) is the correct method for measuring low resistances like that. What that does, is to provide separate terminals for the "force" current and the millivolt meter, so that the resistance of the leads, connections, fuses, etc. doesn't appear in the unknown (the thing you're trying to measure).

Back in the 70s I worked in a test eqpt lab. We were directly traceable to the Nat'l Bureau of Standards (now known as NIST). We used to get that sort of thing in for calibration all the time. I recall one interesting item that somebody had that we would see once a year... it was a decade resistor, with 4 dials, .001 ohm, .01, .1, and 1 ohm steps. Its rated accuracy was .1% if memory serves. It had 4 terminals, obviously. We had to be careful what the room temp was while calibrating it, to keep plenty of air flow through it so it didn't heat up, etc.

I bought a 4-wire ohmmeter for my work here not too long ago, for measuring transformer windings. A lot the same situation as this one except a much more critical application than a car. This particular ohmmeter is a cheap one, only good down to .005 ohms or so, can't recall the details. But it's OK for what we need, our lowest resistance xfmr windings are around .05 - .1 ohms, so it works fine.

Here's a typical method for measuring high currents. Same principle: it separates the high current path from the measurement circuit. http://www.newark.com/canadian-shunt...LFIBoCgkrw_wcB This one would be just about perfect for measuring starting current: you'd do something like, hook the end of the red batt cable opposite the batt to one of those big terminals on top, then add a cable from the other terminal to the starter. You'd then hook a DMM or the like, on the DC mV range, to the 2 small screws on the side of those blocks. Back in the day we used to use an actual moving-pointer meter... not too many of those running around today any more, except in cars, where precision and accuracy aren't ever really that much of an issue.

Big electricity is fun.

QwkTrip

iTrader: (22)

Tibo, there is nothing wrong with using chassis as primary ground as long as it is a good run of metal without interruptions or seams that add electrical resistance. Very common practice in the heavy machinery market where you have thick metal frames. A threaded boss should be welded to the frame where the battery cable attaches. However, I am not sure our uni-body structures qualify as an excellent primary ground...


No matter what you do, the engine should be attached to primary ground using a cable sized for the starter motor (same size as the starter B+ cable).

redneckjoe

i have my battery in the back. welded a stainless 3/8" bolt to the "frame" in the rear, and one up by the motor. ground runs straight to the block from the welded bolt. i also have welded in subframe connectors so that might help? i'm using welding cable, kinda forget what size? have a cut off switch for the positive cable. no problems.

sometimes wiring your ignition seperatly can aid in starting for high compression or over-advanced timing. get the motor spinning, then light the fire.

crazynights

iTrader: (3)

Great info here. I re-checked all my grounds and ran a direct, same size, cable from the negative to the block. No change. Also, noticed that the cable I'm using is 1 gauge but the copper are not fine strands. They are thicker and the wire is very hard to bend/move. I researched online and noticed many using welding cable with fine strands.

skinny z

Last time I read one of these threads the problem came down to the contact between the starter and the block. Seems the OP had used shims when lining things up and this caused the issue. Corrosion or oil/grime could be a factor as well.

crazynights

iTrader: (3)

Skinny,
I do have shims between the block and the starter. I need the shims though. Any idea how they solved it while using the shims?
I will remove them and clean them up if there is any buildup.

skinny z

I don't have the thread specifically as I never replied or subscribed. At least one of the posters here contributed to that thread. Perhaps they recall what happened.
That said, I would think that if the shims, block and starter are clean and the bolts properly torqued, then the connection should be sound. I have a single shim positioning my starter and while I don't have my battery in the trunk, I have zero problems with cranking speed.
FWIW, I have a ground at the front of the block directly to the battery (#1 awg). Another ground to the fender beside the battery (#10 awg) and another from the passenger side cylinder head to the firewall (large braided strap).

redneckjoe

i'm no electrician, but to my understanding electricity tends to want to "flow" on the outside of the wire. that's the reason fine strand works better, more surface area.

can you eliminate the ford type solenoid and just hook the positive up normally to the chevy solenoid on the starter? that could be your issue right there? especially if its not wired in correctly. perhaps describe exactly how you have the positive circuit hooked up?

TA89TPI305

Check each ground wire connection with an ohm meter. Each connection should be less than one ohm. Make sure each bolted contact is nice and shiny- no rust no paint no gunk. Make sure you have zero ohms between block and body and chassis.

skinny z

Any luck?

crazynights

iTrader: (3)

Finally had some time this past weekend to work on the Z. I took off the solenoid and needed to redo some of the wires to make it a direct to starter. Still slow on the cranking. I then looked at the starter and tried to get a cranking voltage reading at the stud, but since it was just me, I couldn't get a true reading as I couldn't maintain a strong contact as I cranked the motor.

Starting to think it may be my cable. Thicker strands, and 1 gauge. I contacted a supplier for some 2/0 wire. Fine strands may go that route.

My grounds now are battery to block, block to k member.

QwkTrip

iTrader: (22)

Just FYI -


The K-member isn't a very good ground either. It is painted metal butted up against more painted metal. Toss in rust, grease, dirt, and who knows what else over the years and it is an unreliable electrical path. If you want a ground to body then ground to the body. And remember, the electrical path is made by the ring terminal flats, not the bolt threads. The bolt is there just to hold the ring terminal in place.

crazynights

iTrader: (3)

Thanks. I'll make the change to a better grounding point. The inner fender or wheel well a better area?

skinny z

A ground cable from the battery to the block is a great idea. It's a lot of wire but will probably prove worthwhile.
Typically, a ground strap from the rear of the cylinder head to the firewall provides what's needed for the "chassis" ground.

oil pan 4

iTrader: (1)

I switched to a powermaster mini starter and ran it on 4 gauge wire and didn't have any slow cranking problems.