e34 not starting, has yellow spark need help.

[gmannino]

I'm experiencing a non starting situation. It cranks over but will not fire up. I'm getting slight hicups. I pulled out one spark plug and cranked my engine. I was getting a slight yellow spark but nothing like it obviously should. I also has a battery charger connected to the car so I know its not a battery problem. Since my spark is so low, I am assuming that my car will not start due to a ignition problem.

Do you guys think a bad Ignition coil could cause this? I tested the coil with a multimeter and my readings are off from the bentley manual. But I've heard much about the Crankshaft position sensor. I know where it is but I have not tested it yet. What are some ways to test the sensor? What is the resistance that should be across this sensor?

Any help would be greatly appreciated!!

One more thing is, I had a coolant hose burst on me and after that my car would not start. I am thinking maybe the coolant got onto the cps sensor or something like that. Would a bad coil prevent the car from firing? how about a bad cps?

[Rustam]

I'm experiencing a non starting situation. It cranks over but will not fire up. I'm getting slight hicups. I pulled out one spark plug and cranked my engine. I was getting a slight yellow spark but nothing like it obviously should. I also has a battery charger connected to the car so I know its not a battery problem. Since my spark is so low, I am assuming that my car will not start due to a ignition problem.

Do you guys think a bad Ignition coil could cause this? I tested the coil with a multimeter and my readings are off from the bentley manual. But I've heard much about the Crankshaft position sensor. I know where it is but I have not tested it yet. What are some ways to test the sensor? What is the resistance that should be across this sensor?

Any help would be greatly appreciated!!

One more thing is, I had a coolant hose burst on me and after that my car would not start. I am thinking maybe the coolant got onto the cps sensor or something like that. Would a bad coil prevent the car from firing? how about a bad cps?

Bad coil can prevent the car from firing if its bad enough not to provide needed potential. Yellow spark - bad.

Bad crankshaft position sensor can prevent the engine from starting. I think Bentley manual does provide information on how to check it.

I think it is an induction sensor, so you can attach multimeter leads to the ends to check for voltage spikes while moving a magnet next to it. You can probably find the needed contacts by consulting the wiring diagram at the end of the manual...

Good way to check sensor connection is by measuring resistance at the ECU connector - this way you combine the test of the sensor with the test of the wires leading to it.

[cschollum]

are all your spark plugs giving yellow sparks? you say yo only pulled one, have you tested other leads apart from that one and with other spark plugs, so as to rule out faulty leads or plugs?
faulty crank position sensor wouldnt result in yellow spark, youd either get no spark or in the wrong frequency
possibly faulty coil
but test plugs and leads first

[gmannino]

I only tested one spark plug. All the plugs are brand new. I just installed a new cylinder head and I got the car to run fine. Then I had the coolant hose burst and then the car didnt start.

I'm pretty sure the wires are ok. I will check the CPS sensor tomorrow and see what I find. Also is there another way to check spark from the coil? I was thinking of turning the car over while holding the coil's primary wire close to ground and see if i can get a spark.

[joshua43214]

What car are you driving? What engine? what year? Check all the plugs for spark, check the coil wire at the cap (do you have a cap?), check the wires at the plugs(do you have wires?) Worry more about spark strength than color, It should easily jump 2 times the correct gap with a snaping sound if strong enough. Use a thin screwdriver pushed up inside the boot(you have boots?) between the boot and the end of the wire(you have wires?), hold the boot with insulated pliers and see how far it jumps to ground. You said a hose burst? maybe coolant got into the plug wire bundle (wires?) and is causing cross firing, or it got under the cap(cap?). Hope some of this helps since im just guessing.

[gmannino]

Ya its a 1990 m20 bmw 525i.

[gmannino]

Ok guys, I spend the whole afternoon troubleshooting the car and I still could not get it working. Here are some of my test results.

-Ignition coil is getting power and works(i swapped with my other bmw and everything worked great)
-The fuel line going into the fuel rail has a high volume of fuel.
-The distributor cap and rotor are still new and in good condition. Wires are in good condition.
-Spark is still yellow. One thing I noticed with this is on my 87 528e I pulled out the spark plug and tested for spark and I shocked the **** out of me. The 525 doesnt seem to have as powerful as a spark as the 528e.
-Crankshaft position sensor is clean and pretty close to the pulley teeth. It also reads 530 ohms like it should. That is read from the connector so the wires and sensor seem to be good.
-The most troubling of problems came from my compression test. I test cylinders 1 thru 5 at 70 lbs, while the 6th cylinder was at 140 lbs. This clearly indicates that the rings are blown on 5 of the cylinders. But my question is this... If my rings are blown and my compression is low, would that prevent the engine from starting like it does?

My car turns over and sometimes hiccups but it will not fire up. I can also see, when i pull out the spark plugs that there is fuel on them.

What do you guys suggest as far as finding the solution to this problem? I'm seriously running out of idea's and feel like junking the car. But i really like this car and I prefer to get it running. Please help.

[Blitzkrieg Bob]

When the hose blew???

It may not be the spark

[gmannino]

That's right, the hose blew and i pulled on the side of the road. When I came to a stop my engine killed. I went to restart and it never started again.

Also when I disconnected my battery and then reconnected, I recieved a code on my dash of "code tacho" Anyone know what Code tacho means?

[joshua43214]

[QUOTE=gmannino]When I came to a stop my engine killed.[QUOTE]


Not sure I understand your meaning here. Do you mean the car overheated and died? if so, that is very bad and you may have cooked the head gasket. Take the coolant cap off and verifi the system is full, crank it over and see if it produces bubbles, a good sign the head gasket is blown. Overheating to the point of stalling is something very few engines can withstand and not blow a head gasket. Since the engine is very flooded from your description, I would attempt to clear the flood as listed below before doing a wet compression check.

Or do you mean you pulled over and killed the engine? Or you pulled over and the engine stalled but never overheated? The coolant from a burst hose may have saturated the plug wires causing a no start/stall until the wires dried out. The low compression could be caused by the rings being washed out by fuel. This can happen from repeated atempts to start the car with no or bad spark.

Also flooded plugs will not start the car, and some plugs will still not function well even after they dry. Remove all the plugs from the car, unplug all the fuel injectors and ground the coil wire, crank the engine to blow out the remaining fuel. use a propane torch to burn the fuel off the plugs, be careful not to over heat the plug and crack the insulator, the fuel will catch fire, burn it off and then stop there, or buy new ones(probably a better idea since you have cheap plugs). put the plugs back in, hook up the coil, leave off the injectors, hold the throttle wide open and start the car. If all goes well, the car should start after a few attempts, idle for a moment, speed up then die, start it again to ensure the flooding is completely gone, then rehook the injectors and start as normal. Get new plugs if you didnt already.

On extreme cases of washout, I have had to wet the cylinders with oil to raise the compression enough to start the car. Follow the above method for clearing extreme flooding, then squirt a small amount of oil into each cylinder, or dribble it down a length of bent coat hanger if you dont have an oil can pumper, crank the engine to swish it arround and blow out the excess, install the plugs and try to start. the danger with this is that you may oil foul the plugs to the point where they wont spark properly, so be prepared to sacrifice a set of plugs and try again.

Also, you said the wires are in good condition. How did you arrive at this assumption? Are they new? if so, what brand? I have seen cheap wires from autozone cause no starts within days of installation and their ignition caps be dead out of the box. resistance checking is a waste of time on 95% of the cases for a number of reasons, the most notable is that it does not test the insulation, which is the most common cause of wire related misfire. You need to verify spark at the plugs and not assume that since you have spark at the cap, and everything appears good, you have spark at the plugs. The majority of tow-in no starts from Do IT Yourselfers I have seen, had some obviose problem that was missed from making assumptions like this.