Young Enthusiast 740i No start HELP!!

[Nueron]

I have a 1998 BMW 740i I that I received with a no start issue. I put a battery charger on it and the car still would not start but it sounded like the starter was trying to hit on some instances. I turned the crank to make sure the engine wasn't seized and then put it in neutral and towed it about 50 yards to a slab of concrete to further diagnose put it in park and tried to crank it again and the starter turned over continuously on its own for a few seconds. Don't think the fuel pump came on though and I couldn't get it to happen anymore. Noticed that the temp gauge was stuck in the red zone and if i played with the switch and unplugged the water temp sensor on the thermostat housing I could get the gauge to go down and the car would make the starter hit sound as opposed to the nothingness when the temp gauge was up. Disconnected the battery with key in switch (heard this can cause problems) found out battery had a dead cell. Replaced water temp sensor and put recently charged deep cycle battery in car and couldn't get the temp gauge to go back down(think key may no longer be synced with​ EWS and DME) to see if car would would turn over. Need to know what to do next should I buy the cables to hook it up to INPA (already have it installed on my XPS) The 20 pin connector is under the hood and OBD inside. Pin 15 in 20 pin connector doesn't have voltage so shouldn't have ADS(let me know if I'm wrong) and will theses cables work?
1.http://www.ebay.com/itm/BMW-K-D-CAN-...53.m1438.l2649


2.http://www.ebay.com/itm/BMW-K-DCAN-O...53.m1438.l2649


or did i mess up the key and should try to get one from the dealership or buy an AK90 and fix my own. Or if it's something else entirely any help would be appreciated
I have access to a shop with a lift and a decent assortment of tools not afraid to work on this car just need info

[Pelican Parts]

Hello and welcome to the forum! I would suggest pulling the codes; it'll likely make it easier for you to troubleshoot the issue. I'm also attaching a link to our section with scanner/reader and accessories. Please let us know if you have any questions!

http://www.pelicanparts.com/BMW/cata...scan-tools.htm

[Mayorchuck]

Welcome to the forum. Was the plug on the thermostat housing wet or burnt? Coolant is known to leak from there and work up the harness into the DME connections. Take a look at this page on Tim's site. I would check the DME connection and those fuses in the fuse carrier:

http://www.meeknet.co.uk/E31/BMW_M62...e_Problems.htm

[Nueron]

Welcome to the forum. Was the plug on the thermostat housing wet or burnt? Coolant is known to leak from there and work up the harness into the DME connections. Take a look at this page on Tim's site. I would check the DME connection and those fuses in the fuse carrier:

http://www.meeknet.co.uk/E31/BMW_M62...e_Problems.htm

No the plug was neither wet nor burned this is the sensor I replaced.

http://www.autozone.com/engine-manag...sor/328994_0_0

- - - Updated - - -

Very Relevant Info also remember hearing very faint alarm sound coming from under the hood on the last attempts to crank

[Mayorchuck]

I would still check the wiring loom and DME connection, and get a proper battery. Going immediately to red is one of the symptoms of this. The alarm sound is a long known mystery of this car. Can't remember if anyone ever figured it out or not.

[Timm]

It sounds that the battery is dead - not just low on charge. The things you have described are perfect for low battery cranking Amps.....

[Nueron]

It sounds that the battery is dead - not just low on charge. The things you have described are perfect for low battery cranking Amps.....

Yes the original battery that came in the car when I got it had a verified dead cell
just to test if this is the primary cause do I need the exact correct battery found here

http://www.autozone.com/batteries-st...20339_909408_0

or can I get something with the equivalent cold cranking amps cause I don’t have the money immediately but my brother is a car audio nut who probably has a comparable battery for the mean time

[ibumpers]

When I bought my 1995 740i it was the same issue, I just got it towed to BavarianAuto & got diagnostic & it was my DME now just waiting on a new one to be rebuilt

[Nueron]

I would still check the wiring loom and DME connection, and get a proper battery. Going immediately to red is one of the symptoms of this. The alarm sound is a long known mystery of this car. Can't remember if anyone ever figured it out or not.

I have gotten the proper battery for the car and replaced the thermostat housing. Once replaced the temp gauge dropped to normal levels and allowed me to turn the engine over I did this a few times with no luck checked to see if i was getting fuel ( I wasn't) checked fuses they were fine so then bypassed fuel pump relay and turned the engine over once. No luck but then the temp gauge went back to red and i could no longer turn over the engine anymore. All suggestions welcome I believe this is an electronic issue and I think the next step is to buy obd cables so i can do a proper diagnostic. If my info in the first post is correct on what cable to buy i will proceed when I get some more funds some one let me know if those cables are ok

[740iSport303]

Check the DME like Chuck mentioned and see if the coolant wicked up to it from the temp sensor on the thermostat. That could be your problem. and doesn't cost anything to check for corrosion.

[Nueron]

Check the DME like Chuck mentioned and see if the coolant wicked up to it from the temp sensor on the thermostat. That could be your problem. and doesn't cost anything to check for corrosion.

Forgot to mention I also already Checked for corrosion of the DME wires and it's completely dry with no damage in sight

[740iSport303]

So you did check the DME connection directly? It's the pins in the connection that get damaged and sometimes break off.

[Nueron]

So you did check the DME connection directly? It's the pins in the connection that get damaged and sometimes break off.

I opened the ebox and disconnected the wiring harness leading into the DME and looked at the pins sticking up from the DME they were pristine. When I looked at the the wiring harness end there was no corrosion but I didn't check the wires to see if any of them were broken inside the housing.