e28 m5 no spark

UPDATE!! FIXED !! see post below...

me and the boy are trying to fix my m5. i bought from a friend over a year ago...drove it for a couple months then loaned it to a friend who had flown in for the weekend.

it died on him over the weekend. (he normally sports a 325ix)

so its been down at my shop for almost a year, just started workin on it again. i wanna get it fixed to drive out to the MIL today for dinner.

first condition...no spark, no fuel so i jumped the dme relay and the fuel pump relay, fuel pump now runs. but injectors not firing, still no spark (checked at coil and at plug) coil has 12v, and good ground.

i still have a no spark condition, and injectors not firing...seems like the computer is not working? any advice ideas?

In reply to jhaas:

If the pump does not prime when you turn the ign key to "start" either one or both of the engine position sensors have failed, or the DME is dead. The DME will not fire the injectors if it does not see a signal from the crank position sensor.

m

Crank position sensor, at the back of the engine on the bellhousing

Giant Purple Snorklewacker wrote: Crank position sensor, at the back of the engine on the driver-side, can't remember if it comes from the bellhousing or the from the block but it points at the starter gear.

7pilot wrote: In reply to jhaas: If the pump does not prime when you turn the ign key to "start" either one or both of the engine position sensors have failed, or the DME is dead. The DME will not fire the injectors if it does not see a signal from the crank position sensor. m

the fuel pump was dead untill i jumped the relay...now the pump primes and supplies fuel fine...the injectors aren't opening. i jumped the dme relay also, but still no spark

In reply to jhaas:

I would suppose that it is possible for the injectors to seal up with varnish in a year, but $$ seems to be on the engine position sensors. These sensors if bad will not signal the DME to fire spark or fire the injectors. They are best tested by using an oscilliscope. A lot of people test the resistance at the sensor plug and look for at least 860 Ohms iirc. Both these sensors, one is engine speed(counts flywheel teeth) and engine position (reads TDC from a pin just to the engine side of the flywheel teeth) are identical.

m

Drivers side engine compartment. There is a connector for the heater control valve, right effing next to it is the cps sensor connector. Check that, they are very very easy to disconnect.

Broken solder joints in the ECUs are getting common with e28s Ms included. Same symptoms as position sensors - no spark, no fuel. If you're handy with electronics - check the joints in the box. Otherwise a place called programma??? or time to do something different with the brain.

any new news on this? I have a similar situation with a buddy of mine. He has a E28 M20 E motor, and it wont fire either. Im having a sneekin suspiciousion its the CPS, but those are pricey to replace and want to knock out all other possibilites before throwin down some $$$ on that...

@ any responders to this thread,
I have an e-24 m635 (euro car) that will not accept any throttle input, It is relatively cranky about actually starting as well seems as if the fuel pump needs to prime for at least 30 seconds before it will actually fire up. If i dont leave the key on for around 30 seconds the car will just crank and not actually light up. Once she does light up like I mentioned throttle input has little to no effect on the engine speed. Any input would be greatly appreciated.

C

In reply to audifan:

Bad fuel pump maybe - you should have two pumps - sounds like one of them is dead (most likely the external one) and perhaps a throttle position sensor?

> oldtin New TPS will check fuel pumps and let you know

OK so I finally ordered a crank position sensor and went to install it today.

I get the M5 up on stands and crawl under it. There are two identical sensors!! Im not sure which one to replace, they both with the same part number on them. I removed both of them, and cleaned off the gunk, and reinstalled no change. Then I took an ohm reading on old both sensors, they were the same as the new part exactly 1000ohm!!??

I checked my DME with 12v and ohm meter...it works fine. I have jumped the DME and fuel relay and still no start!

still NO SPARK, NO FUEL

what the hell is wrong with this M5?

From my post above, check the other end of the connection. Mine has come lose completely on its own and shows the exact same symptoms. disconnect and reconnect the other end.

jhass:
You will never get anywhere working on this busted down old car. Your likely better off just scrapping it. Non-running, that should bring you $250.
Heck, on second thought, let me help you out, I could give you $1k for it and pick it up later this week ($750 if it is the less desirable black exterior.)
Just let me know - I am here to help.

audifan wrote: @ any responders to this thread, I have an e-24 m635 (euro car) that will not accept any throttle input, It is relatively cranky about actually starting as well seems as if the fuel pump needs to prime for at least 30 seconds before it will actually fire up. If i dont leave the key on for around 30 seconds the car will just crank and not actually light up. Once she does light up like I mentioned throttle input has little to no effect on the engine speed. Any input would be greatly appreciated. C

Since it seems to start, but not respond to throttle, I would check for fuel volume and pressure. I would suspect in this case that the fuel pressure regulator has lost function. m

Timeormoney wrote: From my post above, check the other end of the connection. Mine has come lose completely on its own and shows the exact same symptoms. disconnect and reconnect the other end.

I already checked and double checked those...I have the ECU out and apart...I am going to attempt to resolder some of the joints, I dont see any obvious cracks? both boards have some sort of scale on the back of them, kinda brownish, maybe old flux residue?

Im using this article as a guide... http://e28-535i.com/technical/e28-ECU_Repair.php

So if there are two sensors down there, right next to each other...which is which? If one is my CPS, and the other is engine speed? how do i determine which one is what? If my ohm readings are the same as my new part i can assume they are both good. correct? and if i was gonna swap out one of the old ones with my new part, which one of the sensors should i replace?

from what i remember, the closest sensor on the bell housing towards the motor is the CPS, the second, i dont remember what that one was, but they both have the same part number. I read somewhere if you swap them, and if it starts up, that means the CPS is bad. Read it on a E28 site, havent tried it yet...

oldtin wrote: Broken solder joints in the ECUs are getting common with e28s Ms included. Same symptoms as position sensors - no spark, no fuel. If you're handy with electronics - check the joints in the box. Otherwise a place called programma??? or time to do something different with the brain.

Well, I used a small 15watt soldering iron and resoldered all the large connections on both halves of the PCB...it fired up on the first try!!

I called programainc , very nice people, but they wanted $190 to resolder the board with no warranty, or they would 'rebuild' the board for $490 and give it a 3yr warranty. It only cost me $9.00 for a nice small soldering iron at radioshack...

Nice!

alright, i am at a loss with my buddy's E28. I pulled the ECU, opened up, all the connetcors are in great shape with no cracks or wear. Replaced the CPS, both pumps are working, whole ignition system is rewired. i pulled a spark plug out and checked to see if it has spark - NOTHING. No Spark.

So, where do i stand now? Coil? Distributer? Going back to look at it tomorrow, wanna have some points to look at when i get there...

my ecu didn't look like anything was wrong with it...i looked with magnifing glass and still nothing. i hit up all the 'large' solder joints on both halves of the ecu.

try it, it takes 30 min tops...

might have to. I mean, we have gone thru EVERYTHING! Both fuel pumps, ECU, plugs, wires, relays, CPSs....

Are you on mye28.com? Last time I had a weird might-be-an-ECU problem, I just paid someone $25 to ship me an ECU and let me keep it for a week to try in the car. E28 folks are nice and this one is common enough you should be able to borrow one no problem.