M50 1991 525I No Spark

[Emmett0000]

A few years ago I got a 91 525I standard with the idea of using engine in some thing else.
The engine ran good and after sitting one day I tried starting and nothing. I sprayed gas into intake and nothing. I presumed no spark.
I tried the stomp thing to get any codes but couldnt do.
I now have engine out and sitting in test stand I built.
Im sure I have wiring hooked right and have 5V reference at TPS also have hooked up CEL. I have coil 6 out with test plug mounted , no spark. I see maybe I should check all 6 coils but I would think spray of gas would have done something even if missing 1 or more sparks.
I have new cam position sensor and both old and new test at about 1280 ohms.
I have 2 Crank Position Sensor and both test about 500 ohms
Corrected ohm, had them backwards.
TPS also tests correct
Original DME is # 405 and I have a 413 I tested with, no spark
I now have carsoft 6.5.06 and it tells me correctly which DME is mounted but module not respond for anything else.
Im not familar with carsoft, I thought it should give me codes but I guess not, of course I guess it has no codes stored as battery not connect all time. Does it do tests on individual sensors?
Ive tried stomp test on stand and still cant get it to work.

Any and all help and/or direction of where what to do/go would be gratefully accepted.

Thanks - Emmett
PS
does DME need to see fuel pressure or can it before it tries spark?

[ross1]

DME needs to see rotation from the crankshaft position sensor. No signal, no spark, no fuel. Do you have fuel pressure? Presumably something failed before you removed the engine and mounted it your test stand but it's worth mentioning that the crank and cam sensor connections are easily exchanged.

[Emmett0000]

DME needs to see rotation from the crankshaft position sensor. No signal, no spark, no fuel. Do you have fuel pressure? Presumably something failed before you removed the engine and mounted it your test stand but it's worth mentioning that the crank and cam sensor connections are easily exchanged.

No fuel pressure as not hooked up yet, no use gas until spark.
Sensors seem to test OK, I think thats right ohm reading.
I was going to swap crank sensor but I had to heat mount to get hold down screw out and since Im in the rust belt the sensor itself is corroded in. I have it soaking now and Il prolly have to light torch again. Dont want to break mount cast into block.
I decided to check voltage from crank sensor. I got between 1.5 - 2 volts AC with battery going dead so not turning over very fast. I would think that would be enough??

[demetk]

Test the crank sensor for a/c voltage at crank. I haven't tested an E34 cps with the 60 toothed wheel but you should see at least 2 volts a/c.

[Emmett0000]

update
I checked the crank sensor right from the DME connector just in case some wire or connection wasnt connected.
Ohm reading OK AC voltage 2+ volts
I did use a good battery this time
I figured Id try the stomp test for the umpteen time, holy crap it worked. Maybe because I had full voltage ??
A short flash and long flash then rest? I think this means no codes?
I guess I will pull all coil overs and plugs so it turns over faster and see what happens.
Maybe I should conect LED to coil fire lines and see if signal??

comments - Thanks

- - - Updated - - -

more
I did pull all coils and plugs, while plugs out took compression 225 on all but #4, only 75. Darn I guess a bad valve, dont think dry rings for that low.
But thats for another day the problem is still no spark.
Fresh battery and no plugs crank sensor made 2.8 volts, cam sensor about .8V but cheap VOM and I would expect low, only pulses every other revolution.
What can be the problem? 1991 woudnt have EWS or does it have some thing that would stop spark?
Pulled TPS too create code, dummy you need tps to trigger CEL, pulled MAF. Should produce code?? no. OBD1 dumb??
Who know what carsoft6.5 does? I have looked at thread about carsoft but seems to be about what it cant do.

Beer time - Emmett

[demetk]

Some questions.

Main relay has two pins labelled 87?
Is the dme turning the main relay on?
Is ICV vibrating?

Whiskey time.

[ross1]

update
I checked the crank sensor right from the DME connector just in case some wire or connection wasnt connected.
Ohm reading OK AC voltage 2+ volts
I did use a good battery this time
I figured Id try the stomp test for the umpteen time, holy crap it worked. Maybe because I had full voltage ??
A short flash and long flash then rest? I think this means no codes?
I guess I will pull all coil overs and plugs so it turns over faster and see what happens.
Maybe I should conect LED to coil fire lines and see if signal??

comments - Thanks

- - - Updated - - -

more
I did pull all coils and plugs, while plugs out took compression 225 on all but #4, only 75. Darn I guess a bad valve, dont think dry rings for that low.
But thats for another day the problem is still no spark.
Fresh battery and no plugs crank sensor made 2.8 volts, cam sensor about .8V but cheap VOM and I would expect low, only pulses every other revolution.
What can be the problem? 1991 woudnt have EWS or does it have some thing that would stop spark?
Pulled TPS too create code, dummy you need tps to trigger CEL, pulled MAF. Should produce code?? no. OBD1 dumb??
Who know what carsoft6.5 does? I have looked at thread about carsoft but seems to be about what it cant do.

Beer time - Emmett

I've seen one M50 that after sitting for a long period had the hydraulic lifters bleed down enough to inhibit valve opening. Had no clue this was the issue until after checking and double checking everything, Finally, I just cranked the bejeezus out of it and it slowly came alive. Made lots of noise for a while but was absolutely fine afterwards.
The moral of he story is don't write off that cylinder until you have it up and running.

[Emmett0000]

Ive tore many a car apart but never have I seen so much wire!
Im glad the engine harness seems to be one. I think I managed to get the need wires hooked up from the harness but cant remember all diagram now, Il have to dig through again. All I know is I have the DME coming on, verified by carsoft65 and the CEL line as verified by finally getting stomp test working but no results.
Main relay 2 pins labled 87? interesting
DME turning main relay on, I thought would be since CEL light works. I thought when looking diagram how does DME control relay to turn itself on?
ICV vibrating, does it vibrate even at stop?

Do any of these effect spark?
Thanks
Gotta dig out wire diagram and notes.

[demetk]

Here's some more info.

1. Green wire from ignition switch supplies 12v to the engine harness green wire which supplies pin 58 of the dme with power. That tells the dme to turn stuff on, like the main relay. At the same time the same green wire on the engine will supply the coils with power. You have to power up the coils in order for the dme to spark them.

2. Battery voltage (always on power) should be supplied to the pins 30 & 86 of the main relay. Do you have some thick red wires on the engine harness? When I did a m1.3 conversion on my e28 I had a bunch of red wires on the harness close to the main relay. Those I connected directly to the battery.



I'm not familiar with the M50 harness but maybe you have the same bunch of red wires?

So send 12v to engine harness green wire and if you have the main relay wired up correctly, the dme will ground pin 85 on the main relay which will turn it on. That will get the ICV buzzing and it will supply power to the injectors.

You already have the CPS supplying the crank signal because you tested that.

[Emmett0000]

Thanks for reminder Ross. Im not worried about low cylinder until I get it running and yes it could be just simple like you say. The old and true saying, No use is abuse.

- - - Updated - - -

Here's some more info.

1. Green wire from ignition switch supplies 12v to the engine harness green wire which supplies pin 58 of the dme with power. That tells the dme to turn stuff on, like the main relay. At the same time the same green wire on the engine will supply the coils with power. You have to power up the coils in order for the dme to spark them.

2. Battery voltage (always on power) should be supplied to the pins 30 & 86 of the main relay. Do you have some thick red wires on the engine harness? When I did a m1.3 conversion on my e28 I had a bunch of red wires on the harness close to the main relay. Those I connected directly to the battery.



I'm not familiar with the M50 harness but maybe you have the same bunch of red wires?

So send 12v to engine harness green wire and if you have the main relay wired up correctly, the dme will ground pin 85 on the main relay which will turn it on. That will get the ICV buzzing and it will supply power to the injectors.

You already have the CPS supplying the crank signal because you tested that.

Thanks Demet
Some times I get ahead of myself. I assumed the ECU(DME) is on or off but I should know better. Part of controller has the stay alive memory and the engine control part is turned on and off.
Since I kept the complete engine harness together until I got an idea what was what the 3 relays are all in the harness.
I checked main relay and yes it is working right with the 2 #87 terminals going hot, confused me when you said 2 #87 but understand now.
It properly fed the fuel relay and O2 heater. Now when ign is on they did not activate. I dont know if they should or is DME waiting for another signal first?
Everything seems to be connected right and still no spark!
I have pin7 of connector X20 labeled as starter immobilizer, is this maybe screwed up and killing spark??
Some thing is the same as when in car as on stand and is killing spark, I thought maybe was bad main(DME) relay after you clued me in but it all checks good.
Green wire to pin (actually 56 on mine) for ign and since I kept engine harness together starter and main red wire feeds on intact. IAC I cant get at and I read buzz only when running.
Do I have RED wires? Oh yes and lots of other colours.
DSCF9314.JPGEngineStand (1).JPG

[Emmett0000]

Just thought I better make sure there is power to the coils. Yes there is battery voltage at coils when ignition on.
questions
Can you check sensors and operation with a scan/stomp when engine has not been run or only will produce codes after running?
It looks like all perimeters for running are there, what is the matter? What stops the spark? any safety things like no oil pressure etc.?
Some times I wish for points and coil etc. that I can see not relying on 1 and 0 from digital black box.
My buddy says stick a distributor on it!
insert picture of pulling hair out.

[Emmett0000]

Just thought I better make sure there is power to the coils. Yes there is battery voltage at coils when ignition on.

I wouldnt think all coils went out at same time but maybe a weird electric spike blew them so I external tested a few, all good.

There has be some one out there that has some answers or suggestions.
Maybe where I should go other then here? I havent been a user of gas BMW long.

Thanks - Emmett

[demetk]

TI checked main relay and yes it is working right with the 2 #87 terminals going hot, confused me when you said 2 #87 but understand now.
It properly fed the fuel relay and O2 heater. Now when ign is on they did not activate. I dont know if they should or is DME waiting for another signal first?
Everything seems to be connected right and still no spark!

Fuel pump relay only gets turned on by the dme when the dme sees the engine turning via the crank sensor. So if you're not seeing the fuel pump relay getting activated at crank then that should be a clue.

[Emmett0000]

update
With ign on there is no grd feed from DME for fuel or O2 relays. Also when turning over with starter. Now you say DME has too see crank turn to activate fuel relay. But the crank sensor is making over 2 volts AC at the DME connector, that would indicate the sensor and wiring are good?
Looking through wire diagrams I have notes pin 65 on DME feeds thru pin 10 on X20 (engine to body connector) to transmission and grounds in park or neutral. Mine is standard but has pin 65 but not 64 which is trans interrupt for shift. I thought maybe on standard it is clutch monitor and no spark when not depressed but that didnt solve problem.
Im leaning to bad DME but it will give stomp test, no code but does show flash and carsoft gives me DME version.
I have a friend trying to find me a 405 DME, As I said I have spare red 413 but it doesnt do spark ether but not sure if it will on 91 M50.

[ross1]

Are you sure the crank and cam sensor connectors aren't mixed up?

[Andrewk79]

The CPS's resistance is 540 ohms +- 10%. The Bentley manual got this wrong. The cam sensor's resistance is either 1024 or 1280 ohms +- 10%. You got them mixed up in your setup. And the dme does not need to see fuel pressure before it tries to crank. Not on an M50 engine anyway.

[Andrewk79]

The 413 and 405 dmes cannot be switched around. One is for vanos and the other is for non vanos. The pinouts are different.

[Emmett0000]

Thanks Andrewk79
Yes, I may have typed the info wrong but the crank and cam position sensors both test with correct ohms right from the DME connector so as to check wire harness also.
I didnt think the 413 would work but I thought it would give me spark as all the pins in the 405 are same in the 413 with the addition of knock and vanos etc pins.
My friend in California is looking for a DME at picknpulls but no 405 as yet just the 413.
There are many more BMW in CA then here in Niagara.
I would guess a 400 402 403 or 404 would also work as far as spark as they are all motronic ver 3.1?
I gotta let it rest a while but it sure has put a dent in my plans of placing M50 in different vehicle.

[Andrewk79]

Hello Emmet,The 413 and 405 dmes are not interchangeable. You are wrong about the pinouts there : Its not just about knock sensors and vanos unit. The coils and injector pinouts are purposely swapped. Check the Bentley manual for E34s (free downloads everywhere) to see what I mean.

It is clear to me that you've probably done something wrong. This is common when you pull an engine out of a car. Yes, without fuel, the engine should start with starter fluid. Fuel pressure not required.

Please answer these two questions and only these two questions : What is the resistance of your cps ? What is the resistance of your cam sensor ? And no voltage is completely irrelevant to this, ignore that. Don't check this at the dme clamp. Check this at the sensor harness socket. For both the cam and the crank sensors. Easy for you to do since the engine is on a stand.

Your ignition coils are easily checked. Check the resistance of each one against the value stated in the bentley manual. If they ohm out correctly, they are 99% fine. Anyway it is unlikely for all to be dead.

Yes one cylinder with no compression should not screw a startup. You've got good compression on the other cylinders, so you don't have bore wash to deal with. The engine will run badly though but that's not the issue here now.

If your cps is working and correctly installed and connected, and your coils ohm out correctly, and you did not screw up anything else, the only reason your engine does not start up would be a bad dme. Nothing else.

I use carb cleaner as starting fluid. Works like a charm.And yes 405 dmes are pre EWS so you don't have to worry about that.

Andy

p.s. I suggest you and correct all the factual mistakes in you made in your various posts in this thread if you made any. If you don't do so, it makes it very hard for those new to the thread to follow and respond.

[ross1]

Do you have 12v + at the DME? Pin 26 red wire

[Emmett0000]

Andrew, yes good to have right figures. I had the ohm reading backwards.
I checked again at the sensor connectors, brrr it cold out today.
Crank sensor at 500 ohms. Cam sensor at 1290 ohms.
==
Ross, funny you should ask. The last check I did was confirm all power feeds and grounds. They are all correct as they should be because I pulled engine with wire harness attached and complete. I only stripped the body side of the engine to body X20 connector. Added switch for ignition and starter. Also check engine light and oil pressure light.

[Andrewk79]

Well my friend I'm going to save your life today. I just remembered a very obscure problem I had with this early last year. The car wouldn't start even though the cps ohmed out fine. One of the wires at the cps's harness connector had broken. It couldn't be seen due to the insulating boot.

Do this. Put a wire in the two business ends of the cps's harness connector (the third one is for ground - ignore - be careful about this). Then check for continuity at the dme clamp. You'll need alligator clips and needles to get through the dme clamp's holes, and a multimeter to confirm continuity.

Check pinouts very carefully before you do this, and count them out on the dme clamp very carefully. Count the pinouts in the correct direction (there are markings on either end of the dme clamp). Mark the right slots with black ink lightly, you're bound to lose your position otherwise.

[And its a good idea to check the resistances of all your connected devices through the dme clamp in a similar way. And if you read zero, you should immediately check the resistance at the device itself, and if it is not zero, check the harness connector's continuity.

Resistance values are in the bentley manual. I know the iat and ects are the same at 1280 or something. Cam sensor is about 2x crank sensor. Crank sensor is 540 ohms. Forgot about afm and ignition coils.]

If your cps harness connector wire is ok, then its settled, your dme is screwed. Stop your diagnosis. The DME can't be repaired. Get another one, good used $60 max with shipping max. Ebay is the best source.

If i were you, I would do this anyway. A good used afm, good used dme, and two good used coils, are essential spare parts you should just have on you. The afm costs $60, dme $60, the coils about $10 each, about $150 with shipping, good insurance. Can be resold anytime for the same price.

[Emmett0000]

Well as I mentioned, I checked AC voltage at DME connector (dme clamp) . At the same time I checked ohm reading to check complete circuit, DME to sensor.
Ever thing checked OK.
Im waiting on my buddy in California to find a 405 and I guess Ill check around here. I really hate spending money on this project as Im not sure the engine is any good anyway until I get it running and checked out. It did run in the car at first but its been sitting for a few years now with some real cold winters and Im scared maybe something froze and cracked.
I took the DME apart to check for bad solder joints and such but it is a 2 board unit and for the life of me I cant get the top PCB with the ribbon cable away from the connector that looks like the pins go thru the plastic but the only picture I can find on the web shows just board no pins thru conector.
Il just have to wait for a 405 DME. Can anyone confirm a 400 402 403 or 404 would also work as far as spark as they are all motronic ver 3.1?

Thanks - Emmett

[Andrewk79]

Well as I mentioned, I checked AC voltage at DME connector (dme clamp) . At the same time I checked ohm reading to check complete circuit, DME to sensor.
Ever thing checked OK.

I see. Well be happy. You're troubleshooting and doubt is over.

Im waiting on my buddy in California to find a 405 and I guess Ill check around here.

If you buy it on ebay it will take you 5 minutes and $50-$60 including shipping and it will be in your hands in 4 days. If you go around your place, you might not find it, you'll waste alot of time and gas money, its not worth it. Especially since you don't need the engine to be running right now, running around looking for one is not efficient. They usually are gone anyway - one of the first things to be snagged on a car will be the dme.

I really hate spending money on this project as Im not sure the engine is any good anyway until I get it running and checked out. It did run in the car at first but its been sitting for a few years now with some real cold winters and Im scared maybe something froze and cracked.

Please its a BMW. Its not going to crack because the winter is so cold. They've tested all of this under all wear and tear conditions in the factory before releasing the car as they sell to markets in all climates. Don't worry.

And the $60 dme can be resold without difficulty for the same $60 online.

And its a very bad attitude to start a project and not be prepared for unexpected cost. The goal is not to avoid such costs. The goal is to be efficient about that, in both time and money. Once you've started a project, you can't stop, it must be finished successfully !

I took the DME apart to check for bad solder joints and such but it is a 2 board unit and for the life of me I cant get the top PCB with the ribbon cable away from the connector that looks like the pins go thru the plastic but the only picture I can find on the web shows just board no pins thru conector.

I advised you to avoid all of this. Complete waste of time. I've seen 3 dmes looking absolutely perfect but which did not start the car and transmission.

Il just have to wait for a 405 DME. Can anyone confirm a 400 402 403 or 404 would also work as far as spark as they are all motronic ver 3.1?

Yes they will. So you can get a dme from an E36 it will work fine as well as its for the non vanos M50 engine. An E36 or E34 dme from any market in the world will work as long as its for the non vanos M50.

[Emmett0000]

If you buy it on ebay it will take you 5 minutes and $50-$60 including shipping and it will be in your hands in 4 days.


The problem is Im in Canada and the only ones on ebay are over $100 and some wont even ship to me.
$50 US is $80 Canadian plus duty and tax crossing boarder.

Does anyone have one they will sell for $50 and send to Niagara Canada.

Thanks - Emmett