528 position sensors car wont fire up

[johanswe]

Hello! My e28 528 with a m30b35 from a e32 wouldnt start up yesterday. The fuelpump is not running and i have no ignition. The fuelpump work tested it with 12 v and it works. So i assume its the sensors on the bellhousing? Can i resistance measure them? Because they are not reading any ohm the multimeter just say 1 on the display.

The part nr on the sensors are 0261210002 what can i replace them with? Dont looks to be in stock in Europe can only find them in USA.

Ive read that you can change the motronic system and disable them but i just want it up running for the summer.

And another thing my RPM dont work does it have something to do with this? Bought the car last year and i did not do the engine swap.

[1st 5er]

Do you own a Bentley manual?
It describes proper testing and results.
I find it odd that they'd both fail at the same time.

Did the tachometer (tach, RPM) work prior to this failure?
If yes, a no start w/ tach in-op indicates a failure either at or before the ECU. A no start w/ tach showing cranking speed indicates a failure after the ECU.

As far as I know there is no way to bypass the Cranking or Speed reference sensors.

Best of luck as you proceed with the fix.

[johanswe]

No the rpm gauge have never worked since i bought it last year. And i dont own a manual.

[Mike W.]

OK, lets go back a step. You said a 528 and a B35 engine, but what engine management are you using, the original E28 528i, with a conventional distributor sticking up in front, or the B35 Motronic which drives the rotor directly off the cam?

Next, search not for the part number on the part, but by what year and model should fit. Odd as it may sound, numbers on a part aren't necessarily the actual part number, or if they are they may be superseded by a different part number, so you might be searching for an obsolete number. Also I would recheck your resistance numbers, it's unlikely that they would both die at the same time and at least on the earlier ones they tend to go high to very high resistance, but not completely open. They might be on the 10K or even 100K scale, and make sure you're checking the right terminals. Also look at the number on the image below I copied out of a Haynes manual, and you might even be able to find it online, I just downloaded it some years ago from where I have no idea, I just save this stuff when I find it. The page is from working on a late, B35 motronic system.

[johanswe]

It seems to be the B35 because i have a rotor on the car. I recheaked the sensors today with 2 of my 15$ multimeters and even at 200k reading the display says 1. I will try to borrow a 400$ multimeter from work tomrrow if it even matter.

I have a grey and a black connector not grey and white.


Do you think this sensor will work? https://www.ebay.com/itm/387029025126?e ... HlByN5w4jd

Not the same part nr as 002 tho.

[Mike W.]

It seems to be the B35 because i have a rotor on the car. I recheaked the sensors today with 2 of my 15$ multimeters and even at 200k reading the display says 1. I will try to borrow a 400$ multimeter from work tomrrow if it even matter.

I have a grey and a black connector not grey and white.


Do you think this sensor will work? https://www.ebay.com/itm/387029025126?e ... HlByN5w4jd

Not the same part nr as 002 tho.

I believe that sensor is the old style that was used on E28s and read off the flywheel. I think yours reads off the gear like wheel in front, so no.

[johanswe]

No i have the diagnostic plug in front its not a connector for the one on the flywheel

[1st 5er]

If you read German, I do not.

https://www.ebay.com/itm/276452784614?m ... media=COPY

I searched for "e34 b35 crank position sensor".

[Mike W.]

No i have the diagnostic plug in front its not a connector for the one on the flywheel

I'm not sure I follow you. Do you have two, identical sensors actually on the transmission bellhousing? If so the one you linked to will probably work. If you have the gear like wheel in front it will not work. Which do you have, it's starting to sound like E28 era engine management, not what would have come on a B35.

[johanswe]

I have the green wheel infront not the gear wheel and i have two identical sensors in the bellhousing. I dont know if he who replaced the engine used the e28 engine harness i dont know he was a real bungler and should not own a car. But i have a rotor on the cam bought a new one a few months ago and i have no idea how the car was able to run looking like this








Tested with a multimeter from work still no sign of any ohm on both sensors. Ordered 2 new and will see who it goes, from what ive read they usally go bad? So maybe it was time anyway

[Mike W.]

OK, if it's got the two sensors in the bellhousing it's E28 era Motronic. But... I'm fairly certain in EU only 535s came motronic and 528i's came with L jet injection and a conventional distributor, so while they could have used the stock L jet on the B35 they did a conversion to B34 motronic. Odd.

Also, don't forget about the "Main" relay for the FI, they are slightly problematic and will result in a no run condition. It's a very specific relay unlike most 5 pin relays, and not interchangeable with the usual ones.

[johanswe]

2 new impulse sensors and the car fired right up!

Both must have been dead then but what does the second sensor do? You only need one to run the car right? Cuz the other one must been dead for a while

[Mike W.]

2 new impulse sensors and the car fired right up!

Both must have been dead then but what does the second sensor do? You only need one to run the car right? Cuz the other one must been dead for a while

Cool, a win!

Both are needed to start it, but once started only one is needed. The speed sensor that counts flywheel teeth keeps it running and firing on time. But since they're evenly spaced apart it doesn't have a starting point from it. That's where the reference sensor comes in, it reads the flywheel at a specific point. TDC would be logical and expected, but it's not TDC. But it doesn't matter, it tells the ECU where the set point is and once started the flywheel teeth are all that's needed.

[johanswe]

Very much appriciated!

Another question, my rpm tach is dead. From where do it get the signal?

[Mike W.]

It appears to be a Black/Blue wire that comes from the Motronic ECU. There might be some wire coiled up, it might be snipped short, who knows.

[1st 5er]

on getting it sorted.

the tach solution is as simple.