1990 E34 535I "No Start"

[JD1]

Done all the obvious
engine cranks no fuel no spark
Checked CPS have required ohm on terminals 1 and 2
Checked Fuel pump and Fuel Pump relay, Have power to 30 and 85 on crank with ground on 86, No power to Green/purple wire to pump.
Fuel Pump works, and Relay works.
Replaced ECU with working ECU
Got good grounds
Checked Coil has 12v on ignition and is in specs of tests.
Am i Missing something?

[thejlevie]

No spark and no fuel is most likely to be:

No timing reference data to the DME (bad CPS, engine harness fault)
DME isn't running (bad DME, pwr/gnd problem, no START signal)
Bad DME

[JD1]

I traced wire back to DME and its putting out a Negative Signal is this supposed to be Positive? Yellow Lead?

[g00dwagen]

Jim gives good advice. If your DME does not know engine speed or position, it cannot calculate & deliver ignition or injection signals.

If your fuel pump is operating & you've swapped out a KNOWN GOOD DME, then the most likely candidate is no engine speed signal to the DME. The crankshaft position sensor is a good place to start. At this point an oscilloscope, along with a good wiring diagram, is the next step in diagnosis.

Bet you don't have one laying around. Here's the guided fault finding sequence without one:

1. With the ignition switch OFF, disconnect the engine speed/reference sensor connector X1522 located at the front and top of the engine.
2. Turn the ignition switch to the run (ON) position and make the following voltage measurements at X1522 (female half).

• • Black wire (terminal 1) and ground:

Expected result: = Approx. 5 volts.

If not: check the wire to terminal 47 of the DME control unit connector X1500 for an open and short to voltage or ground.

• Black wire (terminal 1) and yellow wire (terminal 2):

Expected result: = Approx. 5 volts.

If not: check wire to terminal 48 of connector X1500 for an open and short to voltage or ground.


If voltages are correct measure resistance of engine speed/reference sensor. Resistance should be approximately 540 ohms. Repair or replace wires or sensor as necessary.

[JD1]

Checking now, both terminal 1 and teminal 2 are grounded , Terminal 1 has low ground and 2 has high ground. Checked pin 47 and 48 no power or ground. Resistance on Sensor is right. There should be a voltage coming from DME through the Yellow Terminal 2 correct?

Pump will only engage if jumperwired Relay is good and have power to all 30,86 and Ground at 85 and 87 (power to pump).

[thejlevie]

Sounds to me like you may have a bad DME or a damaged engine wiring harness.

[bmwdirtracer]

Sorry, but I've got an issue with the relay thing. Let me review.

We've got crank, no spark or fuel delivery.

We've got "Checked fuel pump & relay, have power at 85 and 30 at crank, and ground on 86", with no power to Green/purple" Well, that's wrong, especially when coupled with Relay works" I mean, I'm prepared to accept that the OP accidentally swapped readings for 85 & 86, but even given that, if there's no power at 87, the relay is bad.

But that's just the fuel relay, so let's back up a step: He traced the cranksensor wire that Goodwagen should have 5 volts, and found a ground, instead,so obviously, the dme's not trying to start the car, because it's not delivering voltage to the sensor. And, the ground's not being delivered to 85 of the fuel relay by the dme/ main relay., and the dme isn't trying to start the car.

So what about the main relay??? It activates the fuel relay and spark, by activating the dme, but isn't connected to the "crank" circuit.

I'd start by CORRECTLY testing the main relay, with it plugged into a test plug and the car, so voltages and grounds can be read with circuit intact.

Or just throw a new, EXACT copy of that relay in, and crank it.

{Wrong relay can fry your wiring harness, make sure it workes EXACTLY the same!}

[JD1]

Main Relay - Ign On
30 +
85 -
86 +
87 +
87a -

Fuel Pump Relay - Ign On
+ on everything but 87 Witch is Fuel Pump Power Green/Violet

Put new Relay in on main same issue no + signal to CPS

[bmwdirtracer]

Sorry, I've still got an issue with the relays.

Main relay should have power out at both 87 and 87a, if it's only got power at 87, the relay's bad.

If the fuel pump relay has power on terminal 85, it's not being activated; that should be a ground.

The yellow wire (pin 2 of connector)to the crank sensor is a ground from the dme. The power is on the black wire (pin 1).

You don't really have to test the fuel pump relay for power out, just see whether fuse 23 is hot, that's how the power gets to the fuel pump, when the fuel pump relay circuit is energized.

[JD1]

Ok Double checked

I have power to 87 and 87a Ground to 85 and Power to 86 and 30

Both Terminals to CPS are grounded Ter 1 and Ter 2

Fuse 23 is hot

I am in my garage now workin on the vehicle so I can check everything precisely. On my laptop..with it sitting in front of me lol..

[bmwdirtracer]

Okay, if fuse 23 is hot, you've got power to the fuel pump, and it's working, is this correct?

Are you absolutely sure you're testing terminal 1 of the crank sensor plug, not terminals 2& 3, which are both grounds? Because if fuse 23 is hot, your dme is trying to start the car now.

I'd recheck for power at terminal 1, with voltmeter hooked from terminal 1 to terminal 2 of the connector, ignition on - that way you're checking power and ground to the crank sensor simultaneously (as Goodwagen stated above). And then I'd recheck for spark, perhaps directly from the coil, rather than at a plug wire.

Because it seems to me that maybe you've restored relay function, perhaps by just moving them around, and maybe your car will start now...

If you have spark from the coil, but not at the plugs, check cap and rotor.

If you really don't have power at the black pin 1 of the crank sensor, I'd guess the wire from the dme is bad. But that's not common.

EDIT:

Lastly, are you now using your original dme? You need to be very careful swapping them around this year of production, there were a lot of changes, even mid-year. Does your car have a throttle cable, or eml? Is the replacement/test dme from a car with the same system?

[JD1]

Tested Terminal 1 and it shows light ground, Terminal 2 and 3 have full ground. Ran Voltmeter on 1 and 2 had nothing.

Fuse 23 is hot ,Fuel pump is working but only jumpered. So Im assuming once I get CPS Pump should work fine.

I have 12 volt to both terminals at coil, but only 9 volts at coil wire.

Yes original DME.

Yes throttle cable.

Same model by number on the DMEs.

[bmwdirtracer]

Okay, getting there, we hope.

Fuse 23 is downstream of the relay, but upstream of the pump, electrically. So if fuse 23 is hot , the fuel pump should be on. Exactly what are you jumpering when you say fuel pump works, but only jumpered: the fuel pump, or the relay?

The fuel relay may only get ground when the car is cranking; not just ignition on; it would have power at 30 and 86, ignition on, but no ground except during engine cranking, or engine running, quite possibly.

Similarly, you might just not have power at the yellow wire until the start circuit is completed, or the engine is running: I would doubt this latter possibility, though, because the crank sensor will need power before the crank sensor will work. But measure voltage across 1& 2 terminals of the sensor with engine cranking, to make sure.

Measure resistance across Crank sensor itself, unplugged.

See if you get spark out of the coil wire when cranking engine, coil wire held 1/8 inch or so from a ground/ Don't become the only ground, you'll get a ferocious shock.

[JD1]

I want to say thanks for the input man and help

I got over 10 years working on cars and this is just a home project and it's making me grow grey hair lol! Was supposed to be fun.

Fuel Pump - Might be primed reason for not kicking on with Ignition.
Jumpered as in across relay

CPS - got 550 ohms resistance on sensor unplugged.

Checking volt on crank now..

DME - comes up with no fault codes as well if that helps. 1444 code.

[bmwdirtracer]

Crank sensor ohms are correct.

Check whether you have spark out of coil when cranking. Again, even if you've done it yesterday.

On your car's diagrams, it doesn't look like the pump primes until cranking, so if you want to test whether it's powered, do so while cranking.

http://wedophones.com/Manuals/BMW/19...g%20Manual.pdf

here's where I'm looking up wiring, in case you don't have factory diagrams.

[JD1]

Ok took a break for a few days goto check coil for spark today and no spark, but now lol my check engine light is off and there is no power to the main relay. None to the 30 on the fuel pump relay.. so I am assuming there is a break in the power somewhere? A fuse or Fusable link? Any thoughts..

Checked all Fuses inside and outside. All have power.
Welcome to my nightmare.

Ok found second Fuseable link 50a and fixed it. Should know more by tomorrow...

[JD1]

Ok checking coil for spark today soon as can. Workin on it now...

NO spark, I did see a faint spark once. I checked volts with key is 12 volt, when cranking takes it down to 10 volts.

Checked wire from DME to CPS plug and 1.2 volts when cranking to black lead.

Still no start.

[bmwdirtracer]

Personally, I'd expect to see 5 volts on that wire. Therefore, I'd ask you to verify (retest)only 1.2, making sure you have a good ground when you test. I use the strut tower nuts for ground. I'd also try putting a big battery jump-start cable between your engine block and a strut tower nut or other chassis ground - or better yet, unbolt, clean and rebolt the main engine ground wire.

You had no power to main relay: is that fixed? Was that by replacing the fusible link? And have you discovered what cooked the fusible link? That's a big piece of metal - if it fried once, and you don't know the cause, it may be fried again. (Until we find and repair the cause of the "nightmare", no test done yesterday is valid, necessarily,because we have continuing changes.)

Since you found the fusible link, I assume you're aware of the rear fuse box?

[JD1]

Working on it as we speak. Cleaned the Motor to Chassis Ground got great ground. Yes I am aware of the Rear Fuse box. Checked all fuses inside all passed test.

Running Voltmeter tests on CPS 1.2 - 2.0 volts max thru black lead on crank. Nothing on Yellow wire on crank. Double Checked mic on CPS to Crank .02 on distance.

[JD1]

2) Check the resistance across DME 47 & 48, which should be 500-560
ohms. If the CPS is dismounted, the resistance can be seen to change
from about 500 to 540-540 when a ferrous object is brought to the face of the
sensor. Neither pin should be grounded.

Are these the same pins on my 1990 535I DME? 47 and 48 to the CPS?

Another note.. On the Chiltons manual it states on the CPS plug Yellow is Terminal (1) and Black is Terminal (2).

[Bruce King]

Did you fix it yet?

Sounds like you forgot the air flow meter. A really bad one or bad wire to it will cause the same symptoms as the other items you have been working on.

[Martin85]

Hi, did you solved this problem. I have the same problem with my M5. I have ground on green/violet wire from relay to fuse.

[bmwdirtracer]

Hello Martin, and welcome to the forum.

The E34 M5 which I owned quite recently is forever The Best Car I've Ever Owned.

Don't concentrate on the fuel relay; you need to know whether the DME (engine computer) is trying to start the car. The best bet for finding this out is to test for spark. Pull a spark plug wire, stick a plug in it, ground the threads of the plug, and crank the starter. Do you get spark?

If you have spark, the engine computer is happy, and you have timing information, and we're now concerned with fuel. If you don't have spark, the fuel system is NOT the problem.

[MartinM50B25TU]

Hi guys! Just joined the forum. I have a bmw e34 with a m50b25tu engine and fitted wth a zf5hp18 tranny. Im currently experiencing the same issue. Funny thing before this happened Im not experiencing any issue with the car. Tried to follow the troubleshooting steps for the fuel system but habent done the steps for the dme. If you guys resolved this please advice. Thanks in advance and wishing you guys for your rides to run forever! 🙂😁

[shogun]

Please explain more in detail what you checked so far and what the actual problem is. Only no start?
What happens when you spray brake cleaner into the intake? Does it start for a moment?
Are the spark plugs wet of dry?
Did you already check the crankshaft position sensor?

download this, covers repairs for 5-Series (E34) 518i (90 to 91), 520i (88 to 91), 525i (88 to 91), 530i (88 to 91), 535i (88 to 91) https://e28goodies.com/wp-content/up...escomplete.pdf