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Discussion Starter · #1 ·
I NEED YOUR HELP GETTING MY 1995 BMW 750iL (E38 V12 5.4L) running ...

Next week I am purchasing a 1995 BMW 750iL from a dealer. They claim the car ran fine until a couple weeks ago when they go to turn the key and NOTHING. Nothing lights up on the dash board, no power, no clicks, engine does not turn. It would seem that the problem is the 12 volt battery, right? Well they claim to have put in a standard sized battery (as evidenced by the normal sized battery connected up right now) ... This is the point at which I first looked at the car. I sit in the car, put the key in the ignition, turn the key, and nothing. They greatly discounted the price of the car since it did not start, so I decided to purchase the car anyway and take the chance. Unfortunately this car is over 100 miles from my house so it does not make it easy for me in. I am hoping that I can determine the cause and repair it myself IN their parking lot just after I buy it. Here is where I need your help ... everyone out there familiar with BMW electronics, ignition, electronics, fuses, etc please help me get this car running again ...

I need some help with what to check first, what tools to take, and parts to take along to maximize my chance of making this repair on the spot.

Things I thought to check:

BATTERY:
My plan of attack was to bring along a spare 950 CCA 12 volt battery just in case it is that simple. Keep in mind that the dealer already tried to replace the battery with a "seemingly" 450 CCA 12 volt battery (much smaller than that the vehicle calls for). I myself have not tested either batteries, but I can NOT imagine there is actually 2 dead batteries in the trunk now.

IGNITION:
I have put the key into the ignition and when turning the key on, nothing lights up on the instrument panel, even for a split second (I don't think anyway). This was with their small 12Volt battery hooked up. I am not even sure if this car NEEDS to have a GOOD 950 CCA battery installed to even turn on the instrument panel. I doubt that is the case, so if the batteries are indeed good, then the problem would be electrical, ignition switch, or a fuse. Where the fuses are and what one(s) to check is what I need your help with here.

ECU:
I know these cars came with 1 or 2 ECUs. Could a failed ECU be causing this? I can get 2 ECUs for $100 on ebay ...

At the time of picking up this car I am planning on taking some motor oil along, a new 950 CCA 12 volt battery, a handful of fuses, wire brush, sandpaper, a standard set of tools, volt/ohm meter, and perhaps some different gauges of wire.

I am fairly mechanically inclined, so I can handle some minor troubleshooting. However, I would not be able to do anything major since the dealer will likely NOT allow me to do anything requiring a lift and making a mess in their parking lot.

Any other ideas? Please bring them to my attention, and how I can check. I am trying to put together a step-by-step guide for a quick repair onsite. If I can't get it running I'll be getting it towed to the BMW dealer in town AND YOU KNOW how expensive that will be.

Thank you in advance as I am a NEW BMW owner.
 

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Even a 450cca battery would light the dash and power up electronics and might even start the car possibly but it would never last. My 1st guess would be a bad ignition switch. By the way a 1995 BMW 750il will only have a single battery. So there should not be 2 batteries in the trunk. 1995-98 pre-facelift did not use heated cats. When the facelift M73N motors were installed then they went to heated rear cats and added a 2nd battery in the truck. If it's been converted to dual batteries its hard to say without seeing it if its been done right which could always be the problem and depending if the battery isolator was installed then that might be part of the problem if its failed.
Paul
 

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Sure sounds like the iggy switch. I would add if it's completely dead, it may not give the results shown in the test above. There is a row of main fuses above the battery looking towards the front of the car. It would take a major event to blow them but worth a look.
 

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Discussion Starter · #5 ·
Battery

Thank you all for your suggestinos so far ...

There is no battery conversion going on here. The dealer just simply disconnected the original battery and connected a "known good" battery to see if that fixed it. That's why there are 2 batteries in the trunk.

Since I get NO lights on the dashboard when turning the ignition key I think it is a wiring problem from the battery OR the fuses OR the physical ignition switch.

I am getting to the point where I need to be at the car troubleshooting. However, any other suggestions are appreciated.
 

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I was referring to the ignition switch. If I had been referring what you put your key I would have said the ignition lock cylinder.
Paul
 

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Discussion Starter · #7 ·
I did manage to get the car started, but there are still some serious issues with the car. Perhaps someone can lead me to the cause/fix.

When I got onsite Saturday morning to buy the car, I noticed it was so low on oil that I had to put in nearly 3 quarts to get the oil level up to normal. Then I immediately put in a new battery. The car started up just fine. I noticed that much of the interior electronics did not work. However, the dash board below the speedometer that shows the trip mileage, etc. WAS working fine the first time I started the car, but the windows did not work, nor did any of the center console controls work. They did not even light up. Radio is dead too, as well as "some" (if not all) of the seat motors not working too. None of the steering wheel controls (radio, cruise) worked. I figured this may be a blown fuse or 2 causing this so I didn't think anything of it.. I left it run for about a half hour to see how if it overheated and if the cooling fans kicked on. They did. I decided to shut the car off and finish the paperwork, insurance, etc. as I was feeling comfortable now about driving this car 110 miles home.

THEN... after I went to start the car the 2nd time it was dead. I see a couple lights on the dashboard do turn on when I do turn the key (check engine light, and a couple others). Turning the key would cause a click, and not start. Repeated efforts and the same thing ... We're back to the same issue I had the first time I looked at the car. So since I just put in a brand new battery in the car I decided to take BOTH batteries (the original in the car) and the one I bought to ADVANCE Auto and had them test both. The one I put in was perfect, with nearly 1100 CCA, but the original battery in the car was down to 5 volts (so they practically drained the original battery that was in the car). ... I went back and put my new battery back in the car and same thing, a couple dash lights (check engine, the triangle explanation point, and maybe one other) ... Turning the car results in a couple clicks, and engine would not start, and would not even crank over.

At least I knew it was not a battery issue now. So I went around the car opening and closing doors, even disconnected the battery again, tugged on the cables, checked the battery block wires, all perfect. THEN ... after opening and closing the doors several times I noticed that when I opened the passenger door (with the key in the ignition), for the first time I noticed a buzzer went off, the kind that beeps when a car door is open. Something must have reset, or some connection restored during that event, because after hearing that "door open beeping" the car started. I shut the car off several times and it restarted every time. So, once again, I felt comfortable driving this car off the lot.

Now I only shut the car off once along my journey home while getting gas (mistake) ... and it did NOT start ... not immediately anyway. I took a deep breath, took the key out of the ignition and put it back in and IT STARTED. I did not shut the car of the rest of the way home. However, along the way home I noticed so many things do not work on the interior ... First of all the car must think it is cold outside because heat was leaking out of the vents (not blowing) and even the driver side arm rest was getting hot. The center console was also very HOT... I was worried that something was going to melt down, and since I can not get the dashboard lit up, it may very well be that something did melt between the center console and the firewall. Practically nothing worked on the interior, just the electric sunroof, and 3 lights on the dashboard, which were (check engine, the triangle explanation point, and one other ... I forget).

I should also mention that during my ride home I felt like the engine had a slight, but regular miss, seemingly running down a cylinder... when I accelerated, no matter what gear it is in (5 speed automatic), I felt a slight vibration in the engine, and that vibration is ONLY there during acceleration, so I am fairly sure one of the cylinders is not firing. Now even in this condition the engine was still pretty strong. HOWEVER, as my trip progressed I noticed the performance of the engine has degraded to the point where accelerating was a chore for the engine, seemingly losing yet another cylinder, and perhaps running on 10 cylinders (rather than 12) by the time I got home.

Now that I have the car home, it will not start. I thought for sure I would get it started by doing some of the things I did at the dealer when I had the problems getting it started, like opening and closing doors, checking the passenger side visor light (which was recommended for checking for ECU issues).

So, there are OTHER electrical issues with this car. Obviously it is NOT a battery issue. Here is where I need your help. From what I read, this may be an ECU issue, but I need some input from you experts out there what to try next. What should I try next?

Here is what was recommended to me by a friend:
-Check the wiring block just above the battery - This looks normal and clean, but I did not disconnect anything OR clean any of those connections
-ECU
-Fuses

HELP
 

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Discussion Starter · #8 ·
I should probably also add that I never was able to confirm whether or not the center console works at all (radio, climate controls, air conditioning, etc.) but for a brief time the instrument panel above the steering wheel (speedometer, idiot lights, etc.) DID work at one time.

The car also has 244,000 miles on it. I do think it was taken care of since both interior and exterior are nearly perfect.

PLEASE help me get this car back on the road.
 

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Discussion Starter · #9 ·
I have been looking online to see about buying a used ECU on ebay. From what I read online I need to find an ECU from a 1995 or 1996 750iL ... I can get one for $50 shipped ... so I am thinking of pulling the ECU to check the part number and if it matches the one for sale, I may buy it ... However, I am waiting to hear from some of you folks to see if there is anything else I should check before trying the ECU.
 

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Discussion Starter · #10 ·
I also forgot to mention that the temperature guage in the car DOES work as well as the fuel economy dial. The engine temperature gets up to 1/2 way and no further, so the engine is not overheating at all.
 

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Discussion Starter · #11 ·
Hmmmm ... I do wonder if I can check the engine diagnostic codes with a code-reader tool???
I am trying to see what code-reader tool would work with my Samsung Galaxy S5 phone OR one of my tablet computers. I would prefer to not spend over $100 for a code-reader if possible.

I have also heard that there may be an issue with oxidization causing resistance in the wiring harness connectors. Here is a thread describing that fix which just involves spraying the wiring harness contacts DLC pins, the crimped pin-to-wire connections (under the plug) and to the pins in the ECU harness connector plug (after removing the harness plug from the ECU).

Thread: http://blog.bavauto.com/1979/bmw-e32-e38-750il-no-acceleration-stalling/
 

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With the fact that the farther you went the weaker the car became and then once you reached home the battery was basically dead I'd suspect the charging system is 1 part of the problem. But I also suspect you have Many problems.
I hope you were able negotiate a few extra thousand off when you went to purchase the car with all the problems with it.
 

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Discussion Starter · #14 ·
I do not believe this is a battery drain issue as I believe I already proved that the day I bought the car when it was exhibiting the same symptoms and the battery tested good and the car started ...

Here is my plan of action, cleaning the ECU contacts first (in case it is an oxidization issue)..
If that does not work, next is replacing the ignition switch..
If that does not work then going to get an OBD2 scan tool and read the codes before proceeding.
If it gets to this point I suspect the issue may he with one or both ECUs...
 

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I would at least take the time to check the battery voltage. It's possible the no start with good battery voltage is the ignition switch, but also more highly likely it can be a failing starter.... But the loss of power the further you went isn't a symptom related to the ignition switch or the starter and the fact that even though the new battery they had was undersized that wouldn't explain the fact that it only showed 5 volts when you tested it. I've put 2 starters in my 1995 in a little over 100,000 miles of use by me. and the 95 I have is currently at 250,000 miles. 1st was shortly after I got it, last was about 5000-6000 miles ago. Symptom when trying to start a click and nothing happens other than lights dimming for the time allowed for auto start feature which I believe is about 20 seconds or so that it will try to crank the motor.
Just my 2 cents take it for what its worth 2 cents.
Paul
 

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Discussion Starter · #17 ·
The new battery (the one the dealer was trying to use) that was undersized was NOT one of the batteries that I had tested actually. I never put any faith in that battery in the first place since it was not the right size and because I did not know the history of the battery... I tested the original battery that was in the car as well as the new battery that I installed. I wanted to see if the original battery was bad in the first place. I am going to take both batteries to Advance and have them tested again before proceeding actually.
 

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Just occurred to me but clogged cats will cause a cars performance to get worse the further you drive and when clogged they Really get hot!! That may have contributed to the high heat condition you felt in the car if they are clogged.
 

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Discussion Starter · #19 ·
I just got back to working on this BMW. I have a known working OBD2 code reader tool and I am getting NOTHING from the display when it is plugged in NO MATTER WHAT POSITION THE IGNITION KEY IS IN. The battery is good as it has been tested numerous times (850 CCA). When the key is turned to the "start" position, I can hear the fuel pump run as well as an initial click under the hood (which is probably normal). Since nearly none of the electronics work I have to believe this is an issue with the ignition switch. I am going to order an aftermarket ignition switch on Ebay tomorrow.

Any additional suggestions are appreciated.
 

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Have you tried the 20 pin port (pacman plug) in the engine bay? I have a Peake that plugs directly into the 20 pin and it works great, but I recently bought an Autel because I also have a couple of Chevy's and it does not get anything but power from the port in the cabin. I'm thinking the port is bad (have not verified the Autel works in the Chevy yet, but my indie had a problem with that port last fall). Maybe you have a similar issue.
 
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