m50b25nv. VEMS plug and play. Crank no start.

[E30round2]

I made a duplicate post in the tuning forum, I hope that's ok. I just need help.

I bought the plug and play, sized my injectors (VEMS formula equated to 3.1), and she cranks really strong and healthy. Will not turn over. I am not getting any tach signal from my primary trigger (crankshaft position sensor), which I think is causing my startup issue. I tested the CkPS and it was dead accurate at 540 ohms.

If I set the secondary trigger to primary I get a tach reading, while cranking, of 140-180 rpm (I assume this means my camshaft position sensor is functioning properly). I have done some research and have read that running a secondary trigger is more advanced and is not necessary for initial startup (or at all in some cases).

If anyone has experience with VEMS and m50's specifically, please respond here or send me a PM. I don't want to waste time writing all of my findings here if no one can help.

Engine is 8.5:1 compression
80 lb Deka injectors

Thanks in advance,
Reed

[Greenday694]

I'm not sure if this applies to the VEMS ECU. But when I bought my link ECU, and installed it in my car, it would not do anything. I found out later that the ECU is locked. And I had to send the serial number To link in order to get the unlock code.

Sent from my VS995 using Tapatalk

[E30round2]

After contacting VEMS directly, it looks like the ecu is not getting a signal from the crankshaft position sensor. My concern is a broken connection in the harness, but I tested for continuity between pins 67 and 68 (harness side) and I have continuity. This makes me think the harness is fine, and something else is causing my problem.

A few more pieces of info:
I am using the non vanos harness that came with the engine. The s50 harness was removed with other motor.
The chasis the engine came from was a 1991 525i automatic.
The m3 it currently lives in is a 95 manual car.
Could this cause an issue?

Also, I have now tried 3 sensors. The original one that came with the donor engine, the brand new oem one, and the one that came with the m3 (I know it works as the car ran when I bought it). So I have tried both a VR style sensor and a Hall style sensor, neither one showed any difference.

I appreciate any insight,

Reed

[wazzu70]

You cant just plug in a VR or Hall sensor and expect it to work, both function differently. The setup on the board is also different for each sensor. If its a NV plug and play it has VR inputs.

Using the scope in the VEMS software are you seeing a crank signal from the sensor?

[E30round2]

I know the sensors function differently. I was trying anything at one point the other night.

The Triggerlog shows no input from the primary signal.

At this point I'd like to snip the black and the yellow wires near the terminal end of the harness, and connect the CkPS directly to them. Bypassing the entire harness, which I believe/hope may be compromised.

Regarding the sensor I know that the black wire is positive and the yellow wire is negative (thanks to user:
5mall5nail5).

I believe the yellow wire should go to pin 43, and the black wire to pin 16 (However, I think it would be easier to snip the wires than to try and mess with the pins that connect to the DME).

Can anyone confirm that this is a sound idea?

[E30round2]

I just used my multimeter to test for continuity between pins 16 and 43 (on the harness) and there is nothing.

When I test wires 1 and 2 on the sensor I get 540 ohms (which is spot on). Shouldn't I get the same 540 ohms across pins 16 and 43?

Sorry for posting like a maniac... I'm just really frustrated. This is my first swap and I feel kind of lost.

[E30round2]

While doing some more digging I came across this in an old post (user: goatthumper) that was for building a Megasquirt.

M50 NON VANOS

1- 37
2- Idle Board (ISV2)
3,4,5 Fuel Injector Pin 32,33
6 GND
12- 22
23- Coil 2
24- Coil 3
25- coil 1
26- Constant 12v- Banded end of 1n4001
27- Relay control Circuit (other end of 1n4001)
28- GND
29- Idle Board (ISV1)
31,32,33 Fuel Injector Pin 33,34
34- GND
36- GND (optional, evap purge valve)
37- GND
50- Coil 4
51- Coil 6
52- Coil 5
54- Pin 28 and idle board
55- GND
56- Switched 12v- Relay control circuit
59- TPS 5v- 26
67- VR sensor (24)
68- VR sensor (7)
70- 23
71- GND
74- Tach o (one of the IAC ports)
77- 20
78- 21

This shows the pins being 67 and 68, which when tested do show continuity.

[ba114]

Does the chassis have EWS? Is it possible that you still need to bypass the EWS module?

[E30round2]

It was the EWS! I thought the chassis had it, but I had removed the glovebox to check and didn't find the module so I disregarded the entire idea. With a little more research I found that some earlier chassis require you to remove the number 7 pin from the x20 connector. It's too late where I live to be out trying to start a car right now, but I couldn't wait so I hooked up the laptop and was able to crank it for a second and see that the ecu is now receiving the primary trigger signal! Thank you so much for the the suggestion.

I'll keep you posted tomorrow when hopefully she comes to life for the first time.

[E30round2]

Well, the plot thickens.

I came home from work today confident that I would be able to start my car. Hooked up the battery, plugged in the laptop, started Triggerlog, turned the key... NO PRIMARY TRIGGER.

Here is the log from last night that had me so confident:


I tried unplugging the battery, hooking up the disconnected pin 7 from the x20, plugging in the battery, and then removing the pin 7 again (I was trying to duplicate what I had done last night). Still no primary trigger.

I got out of the car, looked around a bit, seriously couldn't think of anything. Then sat back in the car and tried to turn it over.

Then this happpened:


My fuel pump relay wasn't hooked up so I got out and plugged it in. Got back into the car. Turned the key. No primary trigger.


At this point I blacked out from sadness. I tried to jijggle wires, put in known working main and fuel pump relays (even though I didn't think it would make a difference) and got nothing.

Randomly about 5 minutes later I tried again and this happened:


At this point I thought that maybe the wiring is messed up after all. I cut the yellow and the black wire that connect to the dme, and directly wired the CkPS to them. Turned the key and nothing.

Does anyone have any insight? I am about to give up.

Thanks,
Reed

[NOTORIOUS VR]

It sounds like you have the wrong ECU ordered for your setup... I seen above you have a different motor and harness, etc... You have to be extremely sure about what you're ordering because ECU's are NOT interchangeable when you choose a specific setup.

You just haven't given us any actual info for anyone to help you with either.

m50b25nv should be VR/VR - also looking at the info VEMS has posted, a 525 haness has completely different pinouts than an M50 from an E36. So likely you're issue is that your harness is not compatible with the ECU pinouts if I had to guess.

Whoever you bought the ECU from should be helping you with this. If you bought direct and not from a VEMS dealer then you should have read ALL the notes on the ordering page and confirmed the harness pinouts before ordering.

[E30round2]

From VEMS site:
The M50 and S50 engines are typically found in the BMW e36 platform. The M50 is also used in the e34. If you have an e30 or other car with an engine swap, if it used the original M50/S50 engine wiring harness, it will work with this standalone ECU.

I used the harness that came with the M50 from the e34. Are you saying that this is incompatible? Everything else works fine.

I do have the S50 harness still, but I was advised to use the harness that came with the engine.

I appreciate your help. The customer service at VEMS is non existent.

[NOTORIOUS VR]

Are you saying that this is incompatible?

It seems that way looking at the XLS they posted - so you should get an E34 and E36 wiring diagram and check each pin on the ECU side and verify for yourself if you have doubts.

I have installed plenty of VEMS 88-pin PnP units in BMW's OBD-1 and 2 without issue.

[E30round2]

I tore into my harness yesterday and traced the wires for both the camshaft position sensor and the crankshaft position sensor all the way to the 88 pin connector. I thought that there may be a break in the wires somewhere (sporadic trigger signal had me thinking this). I found that I had continuity, but noticed (after reading VEMS xls file) that I had the two sensors hooked up to the wrong plugs. I had the CkPS going to pins 44 and 16, and the CPS going to pins 67 and 68. I swear I tried swapping them before I tore it all apart, but it didn't make a difference (I think this was due to the ews not being disabled).

Now that I know the wires have continuity, and that the sensors need to be swapped, I tried a suggestion that Marc at EFIexpress gave to me. I started a Triggerlog and grounded pin 67. Using this method I am able to see a primary trigger signal, though it only lasts a few seconds. Once the signal disappears if I remove the ground, wait a few seconds, then ground it out again the cycle repeats.

While grounding pin 67 I noticed that the sound of the hum coming from my icv changes tone. I have read that the engine should run without the icv (not necessarily well, but should run), so I unplugged the icv and grounded pin 67. No primary trigger input. If I plug it back in and ground pin 67, I again can see a primary trigger on my log. Additional info: I am using the s50 icv as the m50nv one was not compatible with the Maximum PSI m50 boost-proof icv hose kit that I am using.

Any ideas as to why my icv would need to be plugged in for me to see the primary trigger signal?

My next steps:
Install the m50nv icv and see if I have the same issue
Trace the icv wires back to the 88 pin connector the verify continuity and integrity of wires

Thanks for any input.

Reed

[NOTORIOUS VR]

I tore into my harness yesterday and traced the wires for both the camshaft position sensor and the crankshaft position sensor all the way to the 88 pin connector. I thought that there may be a break in the wires somewhere (sporadic trigger signal had me thinking this). I found that I had continuity, but noticed (after reading VEMS xls file) that I had the two sensors hooked up to the wrong plugs. I had the CkPS going to pins 44 and 16, and the CPS going to pins 67 and 68. I swear I tried swapping them before I tore it all apart, but it didn't make a difference (I think this was due to the ews not being disabled).

Now that I know the wires have continuity, and that the sensors need to be swapped, I tried a suggestion that Marc at EFIexpress gave to me. I started a Triggerlog and grounded pin 67. Using this method I am able to see a primary trigger signal, though it only lasts a few seconds. Once the signal disappears if I remove the ground, wait a few seconds, then ground it out again the cycle repeats.

While grounding pin 67 I noticed that the sound of the hum coming from my icv changes tone. I have read that the engine should run without the icv (not necessarily well, but should run), so I unplugged the icv and grounded pin 67. No primary trigger input. If I plug it back in and ground pin 67, I again can see a primary trigger on my log. Additional info: I am using the s50 icv as the m50nv one was not compatible with the Maximum PSI m50 boost-proof icv hose kit that I am using.

Any ideas as to why my icv would need to be plugged in for me to see the primary trigger signal?

My next steps:
Install the m50nv icv and see if I have the same issue
Trace the icv wires back to the 88 pin connector the verify continuity and integrity of wires

Thanks for any input.

Reed

Again, you seem to have an issue where the harness is wrong for your ordered ECU - there are far more things different between the 5 series harness and the 3 series harness according to the XLS.

Not quite sure why want to fight this - get the proper harness for the ECU that you ordered and the car should fire right up.

[E30round2]

I have been trying to keep this harness because I read it was best to keep the harness with the engine. I really thought it was my best option. Are you saying that I can buy this (or please recommend a better option), swap the harness out, and be good to go?

https://www.ebay.co.uk/itm/113885411...m=113885411876

Thanks again for your help.

[NOTORIOUS VR]

I have been trying to keep this harness because I read it was best to keep the harness with the engine. I really thought it was my best option. Are you saying that I can buy this (or please recommend a better option), swap the harness out, and be good to go?

https://www.ebay.co.uk/itm/113885411...m=113885411876

Thanks again for your help.

I don't know what you ordered (for the VEMS) - so without that info I cannot help much, but from what I've gathered here I'd have to say you didn't order the right unit for your application.

Did you purchase this directly from the VEMS webstore? From a dealer? I see you have been in contact with Marc is why I ask... If you purchased this from a dealer they should be assisting you with this and should have validated your application - if you got it directly then it's going to be different and unfortunately more difficult.

I'm the Canadian VEMS dealer but I'll need the ECU's SN to get any further with this to see how the ECU was configured when it was ordered. Shoot me a PM if you didn't purchase this from a dealer.

[jrockbk]

I don't know what you ordered (for the VEMS) - so without that info I cannot help much, but from what I've gathered here I'd have to say you didn't order the right unit for your application.

Did you purchase this directly from the VEMS webstore? From a dealer? I see you have been in contact with Marc is why I ask... If you purchased this from a dealer they should be assisting you with this and should have validated your application - if you got it directly then it's going to be different and unfortunately more difficult.

I'm the Canadian VEMS dealer but I'll need the ECU's SN to get any further with this to see how the ECU was configured when it was ordered. Shoot me a PM if you didn't purchase this from a dealer.

i just purchased a m52 pnp unit for a s52 in a e36ti i followed the instructions given to me but i get no start as well im a total noob to standalone, but figured the obd2 vems pnp would bee a good place to start since its supposed to be compatible with my harness. Info on my car is a 98 318ti with a s52 swap bolt on mods include Shrick mild cams, Bosch 24lb ford blue top injectors and 3.5'' maf (although maf is disconnected) with vems. I dont know where to begin to troubleshoot, im still waiting for an answer back from support@vems.hu. thank for the help in advanced