Fail start in my E34 535i M30 1989
Try all
Coil ok
spark plug ok
distributor cap & rotor ok
battery ok
crankshaft rpm sensor ok
coil is powered +12v and -12v but there is no spark
the sensor in spark wire cyl N°6 how many Ohms work?
some suggestion??
Best regards
Big Time Poster
#6 Pickup
Hi,
Do you have a Bentley manual? Highly recommended.
However, I couldn't find the resistance specification for the #6 pickup but you should be able to check for continuity. If it's open, you have a problem. According to Bentley, you should see a pulse across pins 8 and 31 of the ECM.
I'm assuming that you have checked the secondary of the coil and it's not open?
Regards,
Adnan
Major Contributor
Do you have injector pulse? you need to know this to narrow your search.
Did you check for spark at both the coil and the plugs? did you check more than 1 plug?
What do you mean by coil is powered by +12 and -12 volts? the coil is only powered by +12v and is grounded to 0v.
The sensor on the the plug wire is for the tach? car should start without its reference, someone correct me if im wrong on this please.
If you have no injector pulse, forget about the coil and wires and look for problems that involve both systems. Most common cause is bad crank angle sensor, but can be wiring or DME itself.
If you have no spark at the coil, remove the neg terminal and verify 12v at pos. If good check at neg, if no 12v at neg, replace coil. If 12v at neg, attach neg terminal and verify grounding of coil using a tachomer. If you have a tach refence replace coil, if not then you have no ignition control and you need to dig deeper, do you have any anti theft systems? You did check for injector pulse already, right?
If you have spark at coil but not at plugs, check the cap and rotor, after market parts here are usualy pure junk. Verify ignition wires are hooked up in proper order, It is very easy to muck this up, and I had a car towed in from another shop because there "tech" got the firing order wrong, he clained it was a misprint in his service manual when the customer asked him about it.
Big Time Poster
Sensor is not for the tach...
Hi,
On the M30 with DME 1.3, the #6 sensor is required to tell the ECU which bank is which. Without it, the system can't operate. The M50 and M60 don't have it.
Regards,
Adnan
Major Contributor
Cool, thank you very much for the clarification. I am thinking that the computor would use a default setting based on the CAS while cranking so that it would have a reference to use, then use the wire sensor when the key is returned to run position. Please correct or clarify as needed.Originally Posted by Adnan
Super Moderator
Sorry Adnan, the #6 sensor is not needed for the system to operate
DME 1.3 has a semi sequential injection system which triggers the injectors in clusters of 3, 1,3,5 and 2,4,6 every other revolution when the #6 sensor is working. When its not working it goes into parallel mode which shortens the injector pulse by half and pulses them all at the same time every revolution. Many people say that they can't tell the difference between semi and parallel. but the semi is supposed to be more precise and control emissions slightly better.
Super Moderator
It does use a default setting running in parallel mode on startup on all of the
dme 1.3 engines until the engine hits 600rpm then it switches over to semisequential unless no pulse is detected from the #6 sensor, in which case it continues to run in parallel mode.
If the sensor #6 is bad, does the engine start?
My sensor #6 it is not opened, but I will check the pins 8 and 31 of the ECM.
crankshaft rpm sensor looks good by multimeter continuity and resistance, but I will check on the ECM
I have a Bentley manual
Another question: my coil is a regular bosh (not original)it is necessary to put a resistance?
thanks every one
Super Moderator
YES, the car starts and runs fine with a bad sensor on the
#6 plug wire, thats only for timing the semi sequential fuel injection. See my reply below.
Major Contributor
Read the replies above, as others have stated, the car will start and run with the #6 sensor removed. Also, If you read my earlier post, you can see you resistance checking is not needed. Yes, it really is that simple to diagnose ignition no starts. I always loved tow-ins, 95% of no starts can be diagnosed in under 15 minutes and pay 1.5 hours in most of the shops I've worked in. Don't over complicate things and cause yourself extra work.
If you want to use an ohmeter on your coil, make sure you remove the small wires from it. You have to test resistance on 2 circuits, the primary and the secondary. The primary is the low power circuit accross the pos and neg terminals. The secondary is the high voltage circuit between the big coil wire and the spark plugs. Basicaly the primary circuit is a wire wound arround another set of of windings that make up the secondary circuit. As voltage passes through the primary circuit it builds up a magnetic field, when the primary circuit is grounded, the field colapses and passes through the inner windings of the secondary winding, causing a high voltage that is discharged through the plug wires. The secondary is connected to the primary via a resister(simplified I know). This is the basic operation of all 2 wire coils. Armed with this information, you can see that the coil should ave a very low resistance accross the primary posts and a high resistance between the primary and the secondary circuit. Coils differ as to what the primary to secondary resistance should be, a bentleys will have the Bosch stats.
So, now you have checked the coil resistance and it is ok, so the coil is good right? wrong. Bad insulation in the primary winding can cause a short circuit and cause weak spark even though it seems to pass resistance check. So basicaly, if you have power and a tach signal at the neg terminal with no spark, the coil is bad.
Posting Permissions
Reply With Quote