Rebuilt 4.0...trouble turning over

madmodsranger · Feb 11, 2010

I just finished recently rebuilding my 4 liter with new pistons, rods, etc. Block was bored 30 over. I am having trouble getting the starter to turn the engine over more than 1 rotation. I have a new battery that is hooked up directly to the starter (no relay). Cables are in good shape.

I can turn the motor over by hand, but it takes a good amount of force. Can anyone tell me about how much torque it should take to turn the motor over with a wrench with sparkplugs in, no accessories? That would be a great help in diagnosing my problem. Thanks in advance.

Madmodsranger

Bird · Feb 11, 2010

With the plugs out, it should take no more than 40#ft of torque at the crank to rotate the engine.

Bird

madmodsranger · Feb 11, 2010

Thanks bird, I will try it out after work and report back

madmodsranger · Feb 11, 2010

Took exactly 40 ft-lbs to turn

rocks · Feb 11, 2010

Check your firing order.

madmodsranger · Feb 12, 2010

rocks said:
Check your firing order.

Im not trying to fire it up. Plugs arent even hooked up. Im just trying to get it to turn at properly.

With the plugs out the starter was able to turn the engine without accessories. I'm not sure it was fast enough but it worked. I wonder if the starter just doesnt have enough torque to turn it with compression. The starter is pretty old

Nhaz · Feb 12, 2010

Starters can develop "flat spots" which makes them appear weak. If you have the starter off its not had to take it apart and check its brushes and clean out any excess carbon powder build up.

The carbon powder is often the culprit for flat spots. In effect it creates a short between two points somewhere and diverts power away from the starter itself.

Badly worn brushes can also be a problem.

Or a worn out commutator.

TheBeast · Feb 12, 2010

Take it to advanced. Get it tested. Equally the same, check your grounds. Is the strap from the motor to the frame on? Bad grounds will make it act like it hates you.

madmodsranger · Feb 12, 2010

TheBeast said:
Take it to advanced. Get it tested. Equally the same, check your grounds. Is the strap from the motor to the frame on? Bad grounds will make it act like it hates you.

Both battery cables are going directly from the battery to the starter posts.

madmodsranger · Feb 14, 2010

Brand new starter, brand new battery connected directly to starter, and I cant get it to turn more than 180 degrees at a time with the plugs in. Plugs out it is just fine

Do you guys have any other thoughts? Was it rebuilt wrong?

BRUTUS_T_HOG · Feb 14, 2010

what cold cranking amps does the battery have? also you say you have the batt. connected directly to the starter? with what? if you're using long jumper cables it won't be able to deliver enough amperage due to "frictional" losses within the cable. a short fat cable is the best. the longer your cable is the bigger size it needs to be.

also NEW starter? or remanufactured? in my opinion remanufactured just means same as junkyard. all they do is test the commutator for shorts, clean it up, MAYBE replace the brushes and ship it out.

a simple test is to hook a voltmeter to the battery, when you try to crank what does the voltage drop to? it should not fall below 9.5V at about 50-70degrees F. ambient temperature.

being rebuilt wrong is the last possibility. it turns fine without a load but as soon as you load it up it can't handle it.

post results

madmodsranger · Feb 19, 2010

I took your advice Brutus and made up a couple of 2 foot 4 gauge battery cables to connect directly to the starter. I will just say that you are a genius! She turned over like a champ.

So I guess from here I have two options. Since the battery is located in the bed of this truck, do I take the time replacing the existing cables with 2 or 0 gauge, or do I just relocate the battery?

Thanks again Brutus you are the man!

BRUTUS_T_HOG · Feb 19, 2010

madmodsranger said:
I took your advice Brutus and made up a couple of 2 foot 4 gauge battery cables to connect directly to the starter. I will just say that you are a genius! She turned over like a champ.

So I guess from here I have two options. Since the battery is located in the bed of this truck, do I take the time replacing the existing cables with 2 or 0 gauge, or do I just relocate the battery?

Thanks again Brutus you are the man!

thank you.

and if you keep the battery in the bed i would upgrade to 0 gauge cables.

if you move the battery back to the OEM spot then 2 or 4 gauge should be sufficient, you can't exactly go too big lol

ZSK · Feb 23, 2010

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