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I'm unable to start my car (1991 BMW 525i) 147,000 miles. Car overheated bad, replaced thermostat, waterpump, radiator hoses, belts, spark plugs and 3 ignition coils - not fun. Compression checks out ok, no rattles, good engine, I'm getting fuel and fire - dash indicates Check Control. What else could I check?
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when the dash says "check control" what does it say on the check control screen? I dont work on these 5-series much, but all BMW's after the 80's have a check control.
Man, if it overheated it could be several things. So the car wont start, and you have spark? Well check fuel! If you have spark, the other side of the equation is fuel. The heat may have seized the fuel injectors, so make sure they work. You can take a 12v lead and touch to them to see if they work (take a ground and 12v wire and touch to the connectors of the injector and listen for "click". If they work, then you need to check for signal to the injector. If not, then it could be something in the ecu switched off or many things.
Hope this helps,
Josh
Thanks for getting back to me. I've got fuel and spark. Engine is turning over but seems as though it's not hitting right, like the timing is off. Any other ideas?
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I'm guessing all this happened after the engine ran hot? If so, it could be a blown head gasket. I would do a compression test on the engine, to see if there is any air leaking out of the cylinder before combustion takes place.
Also, check the oil, and see if there is any water in it. If there is, the oil will have a "milky" look to it. Also, check the coolant for oil. Open the coolant tank, and see if there is any oil floating on top. If you find water in the cooland, or vice versa, you probably have a blown head gasket.
Finally, you could have cracked the head, or engine block. look to see if you can find any coolant leaks or oil leaks that werent there before.
Most of the time when an engine overheats, it stresses the materials of the engine. Usually this means that the cylinder head will warp. If this had happened, then there will be small gaps between the head and block and this will allow for the head gasket to blow out, causing internal leaks.
Best thing to do is to remove a spark plug, insert the compression tester, and have someone spin the engine over. Watch as compression builds, it should reach 125-150psi at least. Do this on all 6 cylinders! If it is below 100psi, you have a leak somewhere. if you have a leak, the engine will not start, and that's probably what has happened.
Let me know what happens,
Josh
Last weekend I had a compression test run and found 190psi on each cylinder. I haven't found any extra leaks since it's ran hot. The radiator has no oil in it and the oil has no water. Everything seems to check out ok...I'm stumped. Can I pick your brain some more?
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Fire away I'm all ears! That's what I'm here for, ask 500 more questions, you wont hurt my feelings.
This just doesn't make sense! If you have fuel, and you have spark... something has to happen! Is the engine "trying" to start, or is it just spinning over? By "trying" I mean can you hear it sputter like fuel is actually being ignited?
With the 1991 you should have the M50 engine, and unfortunately I am not as familiar with it. I know the older M20's that would have been in the 5, and 3 series in the 1980's.
You have coil-on-plug ignition right? You took a spark plug out of the engine and plugged it into this coil and watched it spark? (You could use a screwdriver and stick in the end as well, and let it spark on the valve cover). If you did this, and you KNOW that you are getting fuel, then something is definately wrong if the engine wont start! If you are getting both fuel and spark, and yet the engine is not firing or sputtering, then it usually means that something is out of time. Since you dont have a distributor it would be next to impossible for the ignition to be out of time. The only thing that could be an issue with ignition is the crank angle sensor (timing sensor) that tells the coils when to fire. But since you are getting fire, this has to be working.
If you dont mind me asking what EXACTLY took place when the engine ran hot? Did you pull over right away when you noticed it? Where there any knocks or bangs? Did the engine just die, and it wouldn't restart? I guess what I really need to know is, did it just die alltogether and it wont restart, or has this gradually gotten worse? All of these things will give me some clue as to what happened.
I've been in your shoes before, My wife was driving my '89 525i, the Thermostat broke, and stuck shut and overheated. She didn't know this till it was too late. Never the less, I ended up rebuilding the engine!
Take care, we'll get this thing fixed
Josh
Thanks for hanging with me on this one. When it ran hot I got it pulled over and got it cooled off and then got it down the road some more and repeated until I got it home and by that time it nearly sounded like a diesel enginge - just making some god awful noises (not realizing the serpantine belt had broken - I'm not that mechanical, now I'm kicking myself because I should have realized it when there was no power steering). But once it cooled down and I was able to get it restarted (with a new belt), man the enginge sounded solid just like before. Since then it's gotten worse. The last time I got it started was 2 weeks ago but ran like it was on 2 cylinders that's when I replaced the plugs and spark plug coils. When trying to start it, it definitely sputters and sometimes backfires a little. Where is the crank angle sensor? That could be it. Because the engine is rolling over and sounds like it's going to start but just doesn't.
AnswerSorry for the late reply, my email has been messing up lately.
Anyhow, the crank angle sensor is "usually" located somewhere on the front of the engine, in relation to the Harmonic balancer. On the older cars the crank pulley had a ring with "teeth" on it, and a sensor mounted close to these teeth. As the teeth of this ring passed the sensor it could time the engine, and knew how fast the engine was spinning.
On the later Dual Over Head Cam (DOHC) engines, like yours, I'm not sure where it is located, but I know it has to have some apparatus to time he engine. If you are getting fire, I highly doubt this is the problem. I had one go bad, and it was as if you unplugged the coil(s) and the engine just spins.
What I was thinking is that if you heard any "knocking" or "banging", or felt any jerking or surging, then it's possible (however unlikely) that the engine jumped time. If this happened then it would have starting issues like your having. However, you said that it sounded great two weeks ago, and its been "going down hill" since then.
Is the "CHECK ENGINE" light on? I know you said something about "Check Control", but they are two totally different things. If you get a "Check Engine" light, that means that something is malfunctioning, and has "Thrown a code". A "code" or "fault code" is what the "check engine" light is one for. Usually if the Check engine light comes on, take it to a dealership/mechanic and have them plug their computer into it. When the computer is connected it will display a 4-digit code, such as "1234". The Mechanic then looks this code up and sees that "1234 = O2 sensor failure". Some of these systems already decipher the code and tell you what the problem is on the computer screen.
My point in all of that is: Since 99% of everything on that car is electronically controlled, it would be nice to see if the ECU has noticed any problems, and can possibly narrow it down for you.
Your car is a '91, so you wont have too many faults to choose from, maybe 4 or so. The late model cars have about 50 different codes they throw.
The check control is a totally differnt thing, it is a little screen that says "brake bulb blown" or "washer fluid low" or something like that. They want you to take the car back to the dealership to be fixed, so they aren't going to tell you what the problem is on the check control.
All I can think of at this point is that you ran the car without a serpantene belt. This helped to over heat the car, as the water pump was not turning and pumping coolant into the engine. This serpantine belt also spins the alternator that charges the battery. You could have drained the battery and that's why it seems hard to start. It sounds like it's definately an electrical issue, unless the engine jumped time (slipped a tooth on the timing chain).
One last question: Did the engine run hot BECAUSE the belt broke? Or did the belt break after the engine was running hot?
Good luck,
Josh
