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grannyknot

Trying to get the ECU to cooperate

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I have an 87 M6 s38b35 engine on a test stand with the proper Motronic 1.0 basic ECU 0 261 200 079 plugged in, I would like to get the engine/ECU running as an independent unit for testing purposes but ultimately it will go in my 72/240Z. The build thread is here,http://forums.hybridz.org/topic/122185-m-powered-z/
Everything is hooked up, engine is turning over with the starter, I have power at the main relay, injectors and coil but can't get the fuel pump relay to work, the ECU controls the #85 ground wire to the fuel relay and I guess I haven't met all the conditions that the ECU needs for that ground to be connected yet.
I think I have narrowed it down to pin 3, 4,5,9 or 14 on the main engine plug, all of those wires go into the cab, pin 17, the burglar alarm is what controls the main relay.
Pin 3 injection signal, I'm not sure what that does but the ECU should already have that , pin 4 coolant temp transmitter, same thing. Actually the ECU should have signals from all those systems before they come into the cab, this is what is making me shake my head.
Can anyone see another reason why the ECU is not connecting #85 on the fuel relay to ground?
Thanks,
Chris

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Looks like fun.  I'd put something about Motronic or BMW ECU in your title.  Otherwise it looks like a thread about a boring old Z or ZX ECU.  Beside that, I think that BMW calls theirs ECM's.

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Don't know if this helps, but I can across this little factoid while doing some research.

 

Seems it's the on board Dash display computer that actually grounds the Main relay for the Fuel Pump. So engine ECU is not actually grounding the FP Relay circuit directly. The Germans Auto makers can always over complicate a very simple thing... Grrrrr.

 

 

Next, we need to make sure it's getting power. In all 1983 and later model year E28s, the main relay gets its electrical signal to close from the on-board computer when you turn your ignition switch to ON or START. The on-board computer is the thing in the dash that tells you your fuel economy, outside air temperature, etc. This is probably the only really stupid thing in the E28's otherwise really good electrical system.  I can't believe they supply power to a critical relay through that piece of junk. Anyway you need check for battery voltage between terminal 86 and ground WITH THE IGNITION ON. Power goes to the on-board computer through the ignition switch. Inside the on-board computer is a little relay that closes when the ignition switch is in the ON, or START positions. The on-board computer also has internal fuses, but those are NOT involved in the operation of the Motronic system.

 Here's the link.

 

http://www.hiperformancestore.com/motronic.htm

 

Really, all you need to find is another circuit from the ECU that grounds on startup. Piggy back a ground from that.

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Another way you could do a work around is to wire a separate Generic Bosch 30A relay for the Fuel pump. But change it from ground actuated to Power actuated. Ground #86  terminal of new relay to chassis. The use a switched power from your ECU or Ignition switch  connected to terminal #85. Sometimes it's easier to find circuits that are Hot when On rather than Grounded when On.

 

Incorporate an Inertia or Crash switch between Terminal #86 of the new  Fuel Pump and the chassis ground. So fuel pump will shut off if you crash into something and are knocked unconscious.

 

The above method would enable you to not have to run the Climate Control Computer... which appears to be the source that actually grounds the fuel pump. Makes sense if you think in an over complicated  German way. Climate control is probably combined with the security system which is also tied into crash sensors. ( Most German cars do it this way )

 

On 2000 and later Audi's and VW's, the Engine ECU is actually linked to a specific Dash Module, because of the Immobilizer configuration.

Edited by Chickenman

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Chickenman,  thanks, I think I have bi passed the whole OBC/anti theft thing by connecting  #85 on the main relay to switched power, # 86 is a straight ground wire all the time, #30 and #87 are powered, main relay is working fine with power to the pos side of the ignition coil and power to the injector plugs.

The fuel relay has power to #86 and #30 because both of those terminals come straight from the main relay, but no power to #87 because #85 is grounded through the ECU.

When cranking the engine I have the fuel feed line off the fuel rail and aimed back into the yellow gas container, there is no power to the fuel pump when the ignition is in ACC or ON or while cranking, the pump only comes on briefly as I let the spring in the ignition switch push the key back to ON when I stop cranking. This is what is driving me nuts, it never did this when installed in the M6.

 

Now as you say I could just find an other circuit that grounds on start up or wire in a separate fuel relay circuit that is triggered by power on and not ground.  But something I think I remember reading years ago when I was just getting into the M6 said that the ECU shuts down the fuel pumps under certain conditions, so if I take control of the fuel pumps away from the ECU I may be setting myself up for more problems, or not, I just don't know that much about FI systems.

Can you think of a situation where the fuel pumps would need to be shut off while the engine is running?

Thanks,

Chris

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Hi Cliff. Glad you found this. Yes, the issue is if you crash.  Crash sensors   will shut down the Fuel Pump by disconnecting the ground side of the relay. In this case, the crash sensors are connected through the Dash Control Module. My Audi is the same way. Most electronic modules  always seem to switch the ground circuit on or off, not the Hot side.

 

 

If you bypass the factory crash sensors you should try and duplicate how they operate. That's why I said to incorporate an Inertia switch into the circuit if you decide to rewire and activate the FP relay by using a switchable Hot feed. IE off Ignition switch or Fuse box. These Inertia switches are readily available at Summit or Jegs. Used a lot on Ford vehicles.

 

https://www.summitracing.com/int/search?SortBy=BestKeywordMatch&SortOrder=Ascending&keyword=Fuel%20Pump%20Cut%20off%20Switch&retaillocation=int

 

Rock Auto also has them. And cheaper:

 

http://www.rockauto.com/en/partsearch/?mfr=STANDARD+MOTOR+PRODUCTS&parttype=10756&partnum=FV7&a=Referer+www.google.ca+URL+%2Fen%2Fparts%2Fstandard%2Bmotor%2Bproducts%2CFV7%2Celectric%2Bfuel%2Bpum

p%2Binertia%2Bswitch%2C10756

 

E-Bay:

 

http://www.ebay.com/sch/i.html?_from=R40&_trksid=p2050601.m570.l1313.TR1.TRC0.A0.H0.XFuel+Pump+Inertia+switch.TRS0&_nkw=Fuel+Pump+Inertia+switch&_sacat=0

Edited by Chickenman

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Hook the Inertia switch to the ground side of Terminal #85. You could also hook an Oil pressure switch, in series with the Inertia to the ground side. That way your engine actually has to be running or cranking to turn on the Fuel Pump relay. This prevents the fuel pump from constantly pumping if the ignition is on, but the engine is not actually running.

 

You want a low pressure sensing switch for this. 5 to 8 lbs.

 

https://www.summitracing.com/int/parts/crt-a68301/overview/

 

BTW. Terminals #85 and #86 are interchangeable. It doesn't matter which is the ground side and which is the Hot side. They are connected only to the Magnetic solenoid which doesn't care about polarity.

 

Terminals #30 and #87 are different. #30 should always be the Hot side feed. #87 ( or 87A ) should always be to the Device you want power fed to . The reason is that #30 and #87 have contact points that open and close. Often there is a condenser on the #30 side to stop any arcing of the points when they separate.  #87 and #87A terminals will have no such condenser.

Edited by Chickenman

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OK, I have given the fuel pump relay a common ground and power from the the ignition switch so the pumps start at the second key position,ON and START, I know I have spark, I know I have 12v on the injector plugs but she just won't start up.

The starter motor is making some really nasty clashing sounds after a few seconds of starting so I think I will take it in to be rebuilt and scratch my head a little more about what I'm missing.

Chris

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12 V at Injector leads doesn't necessarily mean Injectors are firing. Injectors are fed with a constant 12 with ignition on.  Injector Pulse circuit is opened and close on the ground side by the ECU. Best way to check injector is circuitry to use a NOID lite.....or several. They're pretty cheap. I paid $1.97 each for mine in a clearance bin. Any NAPA, Autozone etc should have them.

 

Once you confirm NOID lite is pulsing, you know Injector circuitry itself is good.

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The starter motor is making some really nasty clashing sounds after a few seconds of starting so I think I will take it in to be rebuilt and scratch my head a little more 

Dead/dying battery?  ECM's like proper voltage, starter motors lose their drive at low voltage.

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The battery is new and has a charger on it while I'm cranking and testing. The starter did need rebuilding and is working perfectly now, I bought a noid light and confirmed that no pulse is getting to the injectors.

I removed the ECU harness connector and chased down continuity on all 35 pins to the various systems and components where the wires start, all is good so I know the wiring harness is sound.

So the ECU is not releasing ground to the fuel pump relay, it's not sending any pulses to the injectors and it is not sending any signal to the Idle Control Valve. There may be other things it's not doing but I'm starting to think that maybe the ECU is fried and I need a new or rebuilt one.

The Bosch Motronic page you linked to on post #3 says that failure of the ECU is very very rare but I'm getting to the end of the line pretty quickly.

I just reread that page and I have done all the tests he suggests but I did a continuity test on the wiring harness, not a resistance test so tomorrow I'll switch to ohms and test those 35 pins again.

Programa will do a rebuild on the ECU for $500 which I'll spend if I have to but I'm thinking maybe I should cut my loses and put that money towards an aftermarket FI controller...I don't know.

As always, I'm open to suggestions.

Chris

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On a Project like this I would suggest a stand alone. Factory ECU's just have too much integration into other electronic control modules in the car... particularly High end German cars.

 

Note: There is also some mention of being able to Modify the ECU's to run with out the Factory security system. I suspect that this system is incorporated in the dash module... which you do not have... which could  be causing the issue with no injector pulse.

 

The new AEM Infinity series is very very good from reports on Audi/VW big Turbo forums... but it's expensive. Haltech has some excellent products but $$$ . Megasquirt is the most cost effective solution and there is a TON of support on their forums.  More so than just about any other manufacturer.

 

Edit: Check with DIY Autotune to see which MS unit best fits your needs. MS 2 would suffice for distributor based ignition and Multipoint / Batch Fire fuel control.

 

MS3 with MS3X expansion board gives you full COP ignition and Full sequential fuel injection control and  expandability range. 

 

Note: One last kick at the can......Do check the Camshaft and Crank sensors and make sure they are operating properly.  If one of these is defective it can cause a no injector pulse problem.

 

Here is a good diagnostic site for early and late Motronic testing procedures. Cam and Crank testing is about halfway down the page:

 

http://blog.bavauto.com/3562/no-start-1989-325i-e30/

Edited by Chickenman

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Some more operational information on the Motronic 1.1/1.3 ECU.

 

http://www.bimmerforums.com/forum/showthread.php?1430281-Bosch-Motronic-1-1-1-3-BMW

 

I'm thinking more and more that this may be a Security module issue. I'll have to do some more research, but apparently there are some specific work arounds to get the 1.1/1.3 ECU's to work without the Security system connected.

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Just because wires are going to the right places does not necessarily mean that the ECU has all the proper inputs to make it happy. I'd get together with somebody that has a lot of knowledge regarding the ECU for that car, i.e. an old-school BMW tech. Maybe there are good explanations online, although I'm sure you've done a lot of that research already.

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Leon, an old school BMW tech, man I would love to find one of those guys.

 

CM, This engine runs the Motronic 1.0 basic, and has no bell or whistles, the one wire for anti theft has been bypassed, no cam sensors, no crash sensors, all it relies on is the reference and speed sensors reading the flywheel, the TPS , the water temp sensor and the AFM. I did the resistance test on the all the ECU connector pins this afternoon and none of them have any more resistance then the multimeter probes touching one another. I even changed the ignition switch from the datsun to the bmw switch, no start.

The only time the fuel pumps start working is when I'm letting the return spring in the ignition switch pull the key back to the ON position from START position and that is the same on either ignition switch.

I have done all the tests from this page, http://www.hiperformancestore.com/motronic.htm and the only difference with my setup is my coil has a resistance of .9 ohms between the neg and pos instead of the .5 ohms he recommends and I have 7000 ohms between the center terminal and pos and he is recommending 6000.

Chris

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OK, I have given the fuel pump relay a common ground and power from the the ignition switch so the pumps start at the second key position,ON and START, I know I have spark, I know I have 12v on the injector plugs but she just won't start up.

 

 

 

The only time the fuel pumps start working is when I'm letting the return spring in the ignition switch pull the key back to the ON position from START position and that is the same on either ignition switch.

 

 

Might be worthwhile to take a step back and rephrase the current state of the situation.  You had the pump working on the 21st but it wouldn't start and the starter made noise.  Now you've rebuilt the starter but apparently the pump stopped working again.  Not clear which problem you're working on.

 

Didn't most manufacturers settle on a bypass circuit to the pump for Start, and then some signal, either alternator voltage or a tachometer signal or oil pressure, to keep it working?  Seems like you should easily get pump power with the key at Start.  The ECU shouldn't even be involved. 

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Leon, an old school BMW tech, man I would love to find one of those guys.

 

CM, This engine runs the Motronic 1.0 basic, and has no bell or whistles, the one wire for anti theft has been bypassed, no cam sensors, no crash sensors, all it relies on is the reference and speed sensors reading the flywheel, the TPS , the water temp sensor and the AFM. I did the resistance test on the all the ECU connector pins this afternoon and none of them have any more resistance then the multimeter probes touching one another. I even changed the ignition switch from the datsun to the bmw switch, no start.

The only time the fuel pumps start working is when I'm letting the return spring in the ignition switch pull the key back to the ON position from START position and that is the same on either ignition switch.

I have done all the tests from this page, http://www.hiperformancestore.com/motronic.htm and the only difference with my setup is my coil has a resistance of .9 ohms between the neg and pos instead of the .5 ohms he recommends and I have 7000 ohms between the center terminal and pos and he is recommending 6000.

Chris

 

I bet Dinan would have some great insight if they like to talk about projects like this.

 

http://www.dinancars.com/

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I think I'd seriously be looking at a MegaSquirt. For $350 I'd look into getting a good used MS 2 on E-Bay as a low cost Option.  You should be able to pickup a complete MS2 with MS3X expansion and harness for $350 used. They come up for sale quite often on E-Bay. 

 

Looks like you're pretty comfortable with soldering and electronics, so a new MS 2 DIY kit would be another cheap option.

 

I've played around with some Bosch ME5.3 ECU from my Turbo Audi... and it's an absolute PITA. I even built a Bench Flashing setup, with a chip burner  and starting learning Hexadecimal coding. Just way too much bother for me. 

 

I'm into Stand alone systems now, and they are just so much easier. Everything just works and is infinitely adjustable. Plus the new stuff will self tune, if you buy the right hardware.

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Might be worthwhile to take a step back and rephrase the current state of the situation.  You had the pump working on the 21st but it wouldn't start and the starter made noise.  Now you've rebuilt the starter but apparently the pump stopped working again.  Not clear which problem you're working on.

 

Didn't most manufacturers settle on a bypass circuit to the pump for Start, and then some signal, either alternator voltage or a tachometer signal or oil pressure, to keep it working?  Seems like you should easily get pump power with the key at Start.  The ECU shouldn't even be involved. 

Right, any confusion is my fault,  the situation the way it is now is exactly the way it was when I started, Chickenman suggested taking the ECU out of the loop with the fuel relay by powering it separately. I did that and the pumps came on when I wanted them to but the ECU was still controlling injectors, ICV and so on and if they are not working then nothing else is, so I put everything back they way it is suppose to work and concentrated on finding out why the whole thing isn't working.

Still haven't found the answer to that yet but I sure know a lot more about this system then when I started.

 

If I do go for a stand alone system how do you get the new wiring harness to match up with the existing sensors and control units, or do they have to be replaced as well?

Thanks,

Chris

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I don't know the BMW cars very well or their service manuals, but it looks like they were using L-Jetronic for quite a while.  I found a manual and downloaded (I save all old documentation on the off-chance I might actually get one in the future).

 

Could it be the fuel injection relay that's the problem?  Looks like they were doing the same as Nissan, a separate pump relay and an EFI system relay.  Could be that one powers the other.  Nissan started using a control relay to power a relay on their fuel systems in 1978.  I don't know if the EFI relay needs to work to run the pump relay, but I do know that my 76 car wouldn't start when the EFI relay started to die sporadically.  I had a fuel pump switch, kind of like where you ended up before the starter problem, so never figured out if the pump was working when the EFI relay went bad.

 

Here's a link and a picture (page 163).  Things were probably similar for the M6.  It's a big file. http://www.mediafire.com/download/tmn3nj4z2k2/bmw_e30_repair_manual_v7.pdf

 

 

post-8864-0-11555300-1467078640_thumb.png

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If I do go for a stand alone system how do you get the new wiring harness to match up with the existing sensors and control units, or do they have to be replaced as well?

There are lots of Options for making a new harness. 

 

You use a new bare harness that comes with your Stand alone system. ECU side is terminated with proper Terminals and there is usually a sub- harness for a Relay box ( Fuel pump, ECU Main Relay, Cooling Fans, Nitrous etc ) The sensor ends, injector, etc  are bare pigtails and you attach what ever terminal ends you need. Bosch terminal ends are widely available on the internet. DIY Auto Tune carries any terminals and parts you need.

 

https://www.diyautotune.com/shop/wiring-components/

 

You can also order the new Harness pre-terminated with all the correct ends from DIY Auto Tuning ( or any other supplier ) for additional money.

 

One of our members ( Fric Frac ) makes beautiful custom made harnesses. He also supplies the bare Bosch connectors ( new style with spring release ) for a reasonable cost. Kit includes enough EV1 connectors for all injectors and sensors, TPS and AFM ( if needed ). Terminals come with unwired terminal pins so you can crimp on the pins to your harness. I find that much easier than soldering wires together and then heat shrinking etc.

Edited by Chickenman

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I don't know the BMW cars very well or their service manuals, but it looks like they were using L-Jetronic for quite a while.  I found a manual and downloaded (I save all old documentation on the off-chance I might actually get one in the future).

 

Could it be the fuel injection relay that's the problem?  Looks like they were doing the same as Nissan, a separate pump relay and an EFI system relay.  Could be that one powers the other.  Nissan started using a control relay to power a relay on their fuel systems in 1978.  I don't know if the EFI relay needs to work to run the pump relay, but I do know that my 76 car wouldn't start when the EFI relay started to die sporadically.  I had a fuel pump switch, kind of like where you ended up before the starter problem, so never figured out if the pump was working when the EFI relay went bad.

 

Here's a link and a picture (page 163).  Things were probably similar for the M6.  It's a big file. http://www.mediafire.com/download/tmn3nj4z2k2/bmw_e30_repair_manual_v7.pdf

 

ZH has a very good point. German manufacturers like to use Multi function relays instead of individual relays. They have multiple sets of contacts inside controlling power to different circuits, such as Fuel Pumps, Ignition and Injectors. One set of contacts can fail while another still works. Might be an idea to get a new ECU relay or at least test the old one to make sure all the contacts are working correctly.

 

Sometimes it's faster just to pop the cover off and give it the old " Sniff " test. Burnt out coils have a distinctive odor.... and you can usually see any discoloration of the windings.  Pitted or corroded contacts can be viewed with a mgnifying glass.

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I don't know the BMW cars very well or their service manuals, but it looks like they were using L-Jetronic for quite a while.  I found a manual and downloaded (I save all old documentation on the off-chance I might actually get one in the future).

 

Could it be the fuel injection relay that's the problem?  Looks like they were doing the same as Nissan, a separate pump relay and an EFI system relay.  Could be that one powers the other.  Nissan started using a control relay to power a relay on their fuel systems in 1978.  I don't know if the EFI relay needs to work to run the pump relay, but I do know that my 76 car wouldn't start when the EFI relay started to die sporadically.  I had a fuel pump switch, kind of like where you ended up before the starter problem, so never figured out if the pump was working when the EFI relay went bad.

 

Here's a link and a picture (page 163).  Things were probably similar for the M6.  It's a big file. http://www.mediafire.com/download/tmn3nj4z2k2/bmw_e30_repair_manual_v7.pdf

NZ, your right, the main relay powers the ECU, the injectors and the fuel relay, the fuel relay powers the fuel pumps, O2 sensor and the ICV. I did try some new relays when I first started testing but I hadn't sorted out the anti theft wire or the starter yet,

so now would be a good time to try new relays again.

 CM, good info on the stand alone FI controller, I'm not feeling so intimidated now. I did a bunch of reading last night about Mega squirt, alot of guys love it but there also seems to be a lot guys who despise it. I'll keep an open mind but hopefully I'll get the bmw unit working first.

Thanks for the advice boys, I really appreciate it.

Chris

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Okay, I did some more testing with new and known working used relays for the main and fuel relays, same old story, so I'm done with Motronic, I'll save the wiring harness and convert it to use with Megasquirt.

There sure is a lot to read with MS, so far it looks like I will order,

MS2 extra board,

V.3.0,

a relay board,

Glen's Garage adapter for the 3 wire TPS,

a JimStim,

a GM intake air temp sensor,

a 60-2 wheel harmonic balancer from a m30b35 engine

and an old laptop with a serial port

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