Slow crank

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Duster 72

Duster 72

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Hey guys need a little help. Just got the motor back in the car and it won't rotate fast enough to fire. New starter and new battery. Battery is located in trunk. Any thoughts on cranking issue? Its a 440 .40 over 10.5 to 1 piston compression with 915 closed chamber heads eddy performer comp cam thumper cam. I don't understand what's going on. Checked all cabeles and connections can't figure it out.
 
extra grounds are your friend, I've put lots of short ground cables from starter case to frame rail next to starter , fixed several hard starting problems.
 
You mention a new battery, but what is the battery size and cold cranking rating?
Typically when moving the battery to the trunk the battery must be up sized, due to the increased resistance of the longer cables.
Also if the motor is newly rebuilt and on its first starts, it will be tight.
Engines tend to loosen up after they get a few hours on them. If this is the case you may need to jumper in a second battery for the initial starts.
 
1...What are specs on battery, cranking amps, amp hours, etc
2...What size cables and HOW EXACTLY is it wired including the ground. How is the ground routed from block to body to battery, etc

3..Take some voltage checks. "Rig." a wire with alligator clips long enough to reach from front to back of the car, this does not have to be large, no 20 or larger.

"Rig" a couple of wires (or get a helper) so you can fire the start relay from the trunk area

Start up front. Clip your meter to engine block and to starter post. What is the voltage? If it's below 12.2 or so, the battery is "down" and needs to be discharged.

Crank engine and read meter while cranking. You want to see at least 10.5, the higher the better. If not...............

Run your clip wire back to the back and clip to NEG battery post. Connect that to meter ground lead, and leave other connected to starter battery terminal. Did it come up any?

If not go to rear, Figure a way (starter button, helper) to crank starter from rear. Stab meter direct into battery posts (tops) and read while cranking. Any better there? What is the reading?

What are you using for a starter. If this is the older "wound field" (original type) round you up a Dakota "mini" starter. They crank better and draw less current

NOTE If you are running the starter cable through a "Ford" type relay and then up to the starter, this type problem is why I don't care for that scheme. THERE IS voltage drop through EVERY SINGLE terminal, connection, and switch and solenoid. It all adds up
 
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Think about this. The original +ve battery cable is about 3 ft long . The new cable to the trunk is 12ft. If it is the same gauge cable, there will be 4 times as much voltage drop; if it had 0.2v drop, it now has 0.8v drop, voltage that is lost & cannot contribute to providing current to the starter.

Another way of looking at it: the new cable needs to have 4 times the cross sectional area of the factory cable to keep voltage drop the same. Think how much extra weight that is that the car has to move.............& you have just spent $000s on a more powerful engine to make the car go faster. Although more grounds will 'help' they are usually short lengths, when the real culprit is the long length of +ve cable.

This is a good example of why having the battery in the trunk is a bad idea, unless reqd to do so by some rule or regulation.
 
I ran a long cable from the trunk to a bulk head under the hood. I used that for my Pos. battery post and left everything else factory wiring. High compression race car worked just fine.

Most all new cars the battery is in the rear or under the rear seat.

The solenoid you see above it in the pictures is for a automatic alternator shut of . That was added but not needed unless running a 100 amp one wire alternator

The battery ground went right to the wheel house . I thought that is why the factory put that tab there. LOL

Increase the wire size on battery leads and engine ground!!!

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IMO, if you have only one cable going to the front, the problem will be in the connection to ground, probably at the back. I had to make a bare connection to the frame back there, and clamped the ground to the frame with a new 3/8" bolt; problem solved; same at the front, then painted over them to seal the connections. That was in about year 2000; so far no more problems.
 
On my first picture check out the size of the new battery cable coming from the rear compared to the old original going to the starter. You need a large cable to go the distance. But this may not be your problem starter engagement, tight engine, dirty connections.
I have seen the torque converter not install all the way and destroyed the front pump and bound the transmission. Only you can diagnose the issue. Start looking at the easy first. The first thing I would do is see how easy the motor turns at the damper.
 
have someone crank the engine then hold each cable until one of them gets hot ,you found the problem cable .
 
New High Torque Mini Starter is your friend.

Yes new Rebuilt Engines Are Tight.
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Notice the included Terminal Adapter that works for the Wire leads positioning.
 
Ok guys to see if its a cable issue in going to disconnect existing battery cable and run short factory style short ones and put battery on fender to see if its a cable issue or further in. Battery cable for positive was getting hot after attempting to start last night. Will report back after test!
Thank you all for the help!!!!
 
Duster 72 said:
Ok guys to see if its a cable issue in going to disconnect existing battery cable and run short factory style short ones and put battery on fender to see if its a cable issue or further in. Battery cable for positive was getting hot after attempting to start last night. Will report back after test!
Thank you all for the help!!!!
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PLEASE don't do that ****. It will not "find" the trouble. Use your meter and make some measurements as /similar to what I outlined. FIND the problem. By doing this kind of thing you change the problem so much that you are only guessing in the dark. This may be as simple as one bad terminal on one cable
 
AJ/FormS said:
IMO, if you have only one cable going to the front, the problem will be in the connection to ground, probably at the back. I had to make a bare connection to the frame back there, and clamped the ground to the frame with a new 3/8" bolt; problem solved; same at the front, then painted over them to seal the connections. That was in about year 2000; so far no more problems.
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WAAAAAAAyyyyyyyyyyyyback in the old days when I had the 70 440-6 RR I trunk mounted the battery. I had "obtained" some nice silver plated teflon insulated cable to the front. Added a big "6 volt" eye-to-eye "starter" cable from the block to a bolt through the front frame stub. Grounded the battery in the trunk to the floor. Another thing that helps high current body grounding terminals is to scare up such as Burndy terminals with the two eyelets in the terminals

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Bear in mind this was back when NO PM (Dakota mini) starters. That big 10.5 ***** always cranked just fine. It did not have a lot of overlap so it had a fair amount of cranking compression.

Nowadays many advocate a separate ground strap, which is likely better for electronics (EMI/ RFI etc)
 
Ok guys. Again thank you for the help. I started with the volt meter test until I popped the internal fuse and died! JML I went to buy another one sadly I live in one of those geographically challenged areas where no one is open on a Sunday lol started tracking down all the wiring. I think I may have found the problem! To me I think the starter bolt that the positive lead runs to is making contact with the block! Its tight. There might be enough room for a piece of paper to go imbetween the two. If I get some time thru the week after work in going to drop the mini starter out and put a different one in where the post face a different direction as well as run a few new ground wires.
While I was cranking not having a working volt meter I hooked up my timing light which will not regester with less than 12volts so obviously there's a huge voltage drop from point a to point b. But where is the question?
 
^^Be careful with meters. You sure you didn't get the leads into the current (amps) jacks? It's pretty hard, usually, to blow up modern meters, or even fuses, with the leads properly in the normal jacks. I've even accidently applied voltage to my Fluke in the ohms position, and did not hurt it.
 
You are working with a lot of unknowns here, so be careful what you assume. I provided you with a common sense approach in post #5, as an example of possible problem.

It is a new engine; might be tight & never spin fast with the thickest of cables. Measuring voltage drops across the cable probably doesn't tell you much unless you have data on the starter. Some starters draw less current than others & so the voltage drop will be less & they may crank ok.

What I would do: to get it started, connect another 12v battery in series so that the starter gets 24v. Be careful to maintain 12v to the rest of the electrical system. Engine should start, loosen up with some run time. Once loosened up, re-evaluate the starting problem, if it still exists.
 
Hey guys a glimmer of hope!!!! Well that or maybe you guys can give a little insight. I get off work too late to buy new voltmeter until Friday. However had battery on trickle charge all day got home went out and car cranked over nice and fast and popped to life for a brief moment! However after a couple minutes trying of cranking both battery cables were hot! Then battery got week. If that helps explain the battle? Battery is a CCA 850
 
Duster 72 said:
Hey guys a glimmer of hope!!!! Well that or maybe you guys can give a little insight. I get off work too late to buy new voltmeter until Friday. However had battery on trickle charge all day got home went out and car cranked over nice and fast and popped to life for a brief moment! However after a couple minutes trying of cranking both battery cables were hot! Then battery got week. If that helps explain the battle? Battery is a CCA 850
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The cables get hot due to resistance. As the cables get hot the resistance increases.
Either the cables are too small or there is a loose connection. Since it is both cables sounds like the cables are too small. What gauge cables did you use and how are the terminals fixed to the cables?
 
My 10.5:1 360 was the same way even with a new battery I switched to a high torque mini starter problem solved.
 
Hey guys fixed the problem. It was a combination of two things!!! First my new hi torque mini starter was crap!! 2nd found a burnt coil wire making contact and grounding out!!

I FEEL LIKE A DUMBASS!!!!!

THANK YOU ALL FOR YOUR HELP!!!!
 
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