'84 533i shut-off, won't start - FIXED

[David9999999]

Hello all-

My '84 533i stopped running this morning. The first problem signs occurred last evening when it began running a bit rough and the engine spontaneously shut off, as if the key had been turned off. However, it restarted immediately. This morning, the car was running rough, seeming to misfire/stumble/idle poorly about 50% of the time. Then, I was sitting in traffic and the engine "sputtered" and shut off. Attempting to start yielded nothing. Flat-bed back to my house.

The engine turns over but no sputtering/coughing or any indication of starting. I just recently replaced ignition cap/rotor/plugs/wires, and the car was running great the past 2k miles. From what I've read thus far I am thinking it could be a faulty DME or crank position sensor. I already have a known good DME coming to me in the mail. What else should I be checking while I wait? Thanks!

[Fedaykin528e]

After recently going through something like this, I would invest in a multimeter and start checking things out. I would start with testing your ignition coil, followed by ref and speed sensors. My money is on the ignition coil.

These links proved very helpful for me:

http://www.hiperformancestore.com/Motronic.htm
http://forum.bmw5.co.uk/topic/31961-e28 ... ing-guide/

[ahab]

Remove the fuel pump fuse (red) in the upper left. Place a jumper wire between the two terminals in the green circles. You should hear the fuel pumps come on and within a second or two hear fuel flowing through the rail and FPR. This will rule out a fuel pump problem in a no start. If you hear fuel, try to start the car. If it starts you have a bad fuel pump relay. If you don't hear pumps/fuel you have a pump problem.

In addition to ECU and speed reference sensors, also check that the relays are seated properly, main and fuel pump. Search here for info on jumping out the main relay.

[David9999999]

Thanks for the responses! I will check out all those items this evening and post up with the results.

[trevmmeister]

Ahab most likely has it right, the symptoms sound like the problems i had with a loose fuel pump relay.

Since no one has mentioned it though, also try giving your ECU a couple solid palm smacks, then try to start.

[David9999999]

Quick update:

Smacking DME had no result (though I'm not sure that rules it out)
Jumping the fuel pump fuse caused the pump to run and I hear a hissing type sound from the FPR area, I assume that means the fuel rail was full of fuel. Car did not start after trying that.
I unplugged and replugged relays and that had no effect.

Next step: go get a multimeter!

[CT533i]

Try wiggling the plug going to the Air Flow Meter. That cleared up a rough running situation after washing the engine compartment when I owned this car. Did you wash the area recently or get it wet?

Also, when going over large bumps, the engine would shut off. Happened maybe 3-4 times a year - first 5 years of ownership never occurred - so maybe a fracture in the Motronic board was expanding overtime? May have relevance now.

[David9999999]

Looking more the relays now, the main and fuel relays are both 4-prong. Everything I've read thus far (including checking the wiring diagrams) indicates the main relay should be 5-prong.

However, the plugs that the relays are in both have only 4 connections on them. What gives??

EDIT: I was looking at the relays wrong. The main relay is a 5-prong and I attempted to jumper it (30 to both 87's) to start the car- no luck. What happened was: if I jump 30 to the further 87 first, I hear the fuel flowing. If I jump 30 to the closer 87 first, I hear nothing. Then, when I put in the second jump from 30 to the further 87, I do not hear fuel flowing. Not sure what this indicates.

I also did not mention the car has an alarm- whether aftermarket/dealer installed/etc. I can't tell. I'm afraid that may be another potential cause of problems.

[trevmmeister]

Smacking the ecu rules out the ignition circuit being fractured from age. Maybe. Before I soldered mine, smacking it only helped half of the time.

What is the history of your fuel filter? Also a faulty FPR could also cause stumbling and rough running issues(it did for me).

Does that alarm have a killswitch that you know of? Any kind of fuel-cutout type mechanism when tripped? I am thinking something could have shorted?

The relays are cheap enough to throw at a problem, just pick up new main and fuels and try them out. Make sure you get the main relay that has 87 and 87, not 87a and 87b, if I remember correctly(I sincerely hope I am not remembering that backwards, its late). Also you will most likely need to buy them online, not one auto parts store near me had the right one, only the 87a/b model.

Nonetheless a DMM is super helpful here because until you get one we dont know if youre even getting spark or not.

[Mike W.]

Smacking the ecu rules out the ignition circuit being fractured from age. Maybe. Before I soldered mine, smacking it only helped half of the time.

What is the history of your fuel filter? Also a faulty FPR could also cause stumbling and rough running issues(it did for me).

Does that alarm have a killswitch that you know of? Any kind of fuel-cutout type mechanism when tripped? I am thinking something could have shorted?

The relays are cheap enough to throw at a problem, just pick up new main and fuels and try them out. Make sure you get the main relay that has 87 and 87, not 87a and 87b, if I remember correctly(I sincerely hope I am not remembering that backwards, its late). Also you will most likely need to buy them online, not one auto parts store near me had the right one, only the 87a/b model.

Nonetheless a DMM is super helpful here because until you get one we dont know if youre even getting spark or not.

87b is ok, it's 87a that's the problem.

Technically, if anyone really wants to know, 87b has a second contact in the relay. 87/87 uses one contact with 2 terminals attached to it. They function the same. 87/87a is a normally open/normally closed relay so it acts completely different and is not interchangeable.

[Mike W.]

Have you checked the reference sensors yet? Ohmed them out? They can lead to a no start and are a whole lot easier than the flywheel tab. Pay attention to the readings while you're testing them, they seem to have crimped connections and moving/bending the cables can change the readings.

Does the tach do anything while you're cranking? If it's dead as a doornail that kind of points towards ignition. I say kind of as it's hard to see any reading while cranking, especially with plugs in.

[trevmmeister]

87b is ok, it's 87a that's the problem.

Technically, if anyone really wants to know, 87b has a second contact in the relay. 87/87 uses one contact with 2 terminals attached to it. They function the same. 87/87a is a normally open/normally closed relay so it acts completely different and is not interchangeable.

Thank you much for clearing that up, Mike. Just make sure you get the same one(its a good idea to have a spare).

[David9999999]

My spare ECU/DME should be arriving in the mail later today, so I can try that soon.

I got a multimeter, and will have a friend over this evening to help with cranking it over and checking for spark. Will need to look into the reference sensor tests more- I haven't searched that thoroughly. On the coil, do I simply measure the voltage across the two leads going to it? If I see voltage there, how do I test if the coil is bad? Arc a screwdriver against the body from a plug wire? Lol.

I will definitely order some replacement relays, and I'm going to look into the alarm system more. I don't know if it has a cutoff/kill switch. There's nothing that looks like a switch, though I do see relays on the alarm as well.

Fuel filter has been on my to-do list for sure. FPR I have no reason to suspect is bad. Car always started right up before this and seemed to be fine with smoothness/power delivery.

[trevmmeister]

how do I test if the coil is bad? Arc a screwdriver against the body from a plug wire?

Lol no, that coil puts out thousands of volts, don't remember the number exactly, but that is most definitely a bad idea. I kind of feel like you knew that...

To test the coil check the resistance on the primary and secondary circuit, as user "Cactus" put it back in 2011, "primary as .5 ohms and secondary as 5-6k ohms."

Also; (edited with (...) to reflect your situation)

stuff related to spark:

ecu (New one incoming)
main relay (Helps to replace to cross it off the list)
reference sensors (Search for testing procedures)
coil (Check per the above)
cap&rotor (new)
ignition switch (Have you checked this?)
fuses (you sure they are all making solid contact with no corrosion built up?)
obc relay (Found underneath the driver's side dash, search for how to jump this out, I personally did.)
engine grounds (Part of baselining, theres a thread somewhere around here with every ground point listed. Get sandpaper and some di-electric grease and clean them up. Some are in the bay, some are under the driver's dash)

thats pretty much it

Also, do you have a Bentley Manual? That's rule # 1.

[CT533i]

My spare ECU/DME should be arriving in the mail later today, so I can try that soon.

I got a multimeter, and will have a friend over this evening to help with cranking it over and checking for spark. Will need to look into the reference sensor tests more- I haven't searched that thoroughly. On the coil, do I simply measure the voltage across the two leads going to it? If I see voltage there, how do I test if the coil is bad? Arc a screwdriver against the body from a plug wire? Lol.

I will definitely order some replacement relays, and I'm going to look into the alarm system more. I don't know if it has a cutoff/kill switch. There's nothing that looks like a switch, though I do see relays on the alarm as well.

Fuel filter has been on my to-do list for sure. FPR I have no reason to suspect is bad. Car always started right up before this and seemed to be fine with smoothness/power delivery.

Remember, the 'DME' is really a Motronic system. They didn't call it DME in 1984. DME wasn't until the E32 a few years later. I know what you mean, just want to be sure you are getting the correct ECU/brain. The 533i, 633csi, 733i used a different one than the 535i, 635csi, 735i.

[CT533i]

Fuel Pressure Regulator was replaced in 1999 or so at like 134K mi. And the car now has around 234K mi. I suspect. It's probably worth changing. When changed, once I got on the hwy. lots of black exhaust trailed behind. The tech. told me this would be the case for a few miles. It went away - car idled much better after. The rough running came on rather suddenly.

One other thing, the Coolant Temp. Switch the one on top, close to thermo (most towards front) has two wires from it - the base of that should be yellow. Had a purple one replaced, 0 celcius and it ran horribly. Replaced it with the correct yellow one, and all was so much better. The idle and cold start idle are effected by this part as well. Once it got below 32F the car would not start with the purple one. Make sure it has not been replaced with a purple one - wrong part for a 533i. The 535i has a different switch, green I believe, with a more simplified/wider hose coming from it - it should not have this. The part can create havoc if it's not the right one, shutting off while driving, smoking etc... I remember it all in Spr. 2004. I recall the two wires coming off that yellow, Coolant Temp. Switch were looking a little, 'eh', so I put electrical tape on them. That was 12 years ago. So worth checking to see if all is correct.

[trevmmeister]

535i uses a blue Bosch CTS.

[David9999999]

Yes I know not to arc a spark plug wire, that was a joke!

Thanks for all the tips. I'm going to start going through and checking all the remaining items. Didn't know about the coloring differences of temp switches 533 vs. 535, I will check that as well. This problem did start happening in the cold weather, so who knows.

[David9999999]

Spare DME installed and no change.

Temp switches appear to be the right items. I tested the coil and the resistance (0 ohm and 5600 ohm) were in spec, and it has 12V with key on.

I can hear the main relay "click" if I plug it in while ignition is on- can I conclude this means the main relay is functioning? Is it still possible the OBC relay is causing an issue if I hear the main relay "click"? The OBC has never worked while I've had the car. Nothing visible on display.

Next I need to have someone crank the car while checking voltage on reference sensors. I saw 960k ohm across 1-2 pin and could not find consistent connection between 1-3 and 2-3. It seems those might have a very high resistance across them, which I think is OK.

[trevmmeister]

The display not working is irrelevant to the OBC relay preventing spark. The screen's light bulbs are probably just burned out, which is really common. But there is a circuit where you can program a password to start the car(atleast in my 1988 535, if this feature wasnt present in 1984 OBCs, I apologize and disregard this), and if the password is not entered correctly after so many tries, you will be locked out from starting up until you reset the computer(by removing the battery for a moment). That is given that the OBC and said relay are in working order. I am not completely sure what happens internally to cause the problem, but a "fix" is to just bypass the circuit into always reading "correct password".

Search and thee shall find. Just cut a two inch piece of wire and find which pins to jump. Again, this relay is located underneath the driver side trim panel, left side of the wheel.

Also yes I am pretty sure the click indicates an actuating, healthy relay. Or it could indicate it is just getting power but might not be fully engaging. corrosion can make its way around the aluminum casing and well, corrosion+electric current do not mix, especially when youve only got 12v to make that contact actuate.

[ahab]

OBC I is different in the early cars. You may want to get the ETM and start reading. Here's the page for the OBC with the start cutout relay wires to jump in red. According to this schematic if pin 86 on the main relay is hot with the key on then that would rule out the code relay. You should also go back to some basics. Does a spark plug spark? Pull a lead and plug a spare into it, then crank. For $20 Autozone will sell or rent you a noid light kit which will tell you if the injectors are being pulsed. These simple tests can rule out a lot of things too.

[CT533i]

The fuel pump was never changed during my ownership and prior (0-223K mi). Could this be a possibility?

The Fuel Filter was changed every 1-2 yrs - or 20K mi.

[CT533i]

The display not working is irrelevant to the OBC relay preventing spark. The screen's light bulbs are probably just burned out, which is really common. But there is a circuit where you can program a password to start the car(atleast in my 1988 535, if this feature wasnt present in 1984 OBCs, I apologize and disregard this), and if the password is not entered correctly after so many tries, you will be locked out from starting up until you reset the computer(by removing the battery for a moment). That is given that the OBC and said relay are in working order. I am not completely sure what happens internally to cause the problem, but a "fix" is to just bypass the circuit into always reading "correct password".

This is a 533i which has OBCI/II version. 1st was in 1981/82 which looks virtually the identical to the 2nd version last used in 1984 US-spec 5,6,7-series. The early OBC in the 533i, has a different key-pad, LEDs, Display, control unit and offers more functions than the one in the 535i and other `85-on models. Apparently there are 2 control units on the early OBC. The OBC worked perfectly during my ownership, other than the 4th display digit was dim, and the right column of LEDs were dim (next to buttons) when the 4th display digit was dim -when the 4th digit was bright (at full intensity) so were the LEDs on that side. So the control unit for the lighting display - is not a simple bulb as so many think, who are mostly familiar with the far more common and simplified `85-on OBC.

The Code function on the early OBC works similar to the later OBC versions. 3 attempts to enter correct code or 3 attempts to start. If code not matched, (on the 533i) a unique horn (different tone than main horn) will sound in fast repetition. Entering the correct code will kill the alarm. If all else fails, remove the OBC fuse in the main fuse-box, then install and start the car. Disconnecting the battery is not needed. When the correct code is imputed it will not read 'correct password.' The LED next to the Code button will go off - telling you the system is not armed. When imputing the wrong code it will reset to 0000 indicating, start-over, you're wrong. When arming the system, pressing the code button will display 0000, enter a 4 digit number, after 3-5 sec. the led next to the Code button will illuminate, showing the system/function is activated.

[trevmmeister]

Yes i know it does not literally say correct password that was for lack of a better wording, which I figured was obvious.

[Mike W.]

I'd forgotten it was an early car. A non working early OBC will often be due to a blown fuse in the OBC unit, BTDT. How it might impact starting I can't say, but bypass appears to be similar.

Fuel pump is a possibility, they can die with no warning, completely. Do a pressure test or just disconnect the hose out of the FPR and if you have flow you should have pressure, but I think I recall you did some test on it. Or bang on the pump with a screwdriver handle, that will usually get it going long enough for troubleshooting. It's not a fix, just a troubleshooting tool.

[David9999999]

Fixed!

New ignition coil arrived in the mail today. Swapped it in and it started up, and is running fine now. It's odd to me because the old coil had the correct resistance across the two circuits and had 12V to it.

Thanks to everyone for the help- I learned a lot testing everything and am glad it's up and running!

[Mike W.]

Insulation can break down at high voltages so ohming it out isn't a perfect test. I am surprised, coils don't fail often. Glad you got it figured out/