Djet starter upgrade?

[nashvillecat]

Can a so-called upgraded smaller starter (with only three electrical terminals) be adapted to work with the Djet models?

I have a newer style starter (smaller w/permanent magnets) that many of the early 70's and 80's BMW’s use as a common replacement/upgrade for their cars. It was a spare for a non-e9. Sticker with model number is missing. Unlike the OEM starter solenoid, the solenoid on the “newer” starter has only three electrical connections. The OEM starters have four prongs. I suspect some of the newer smaller starters actually have a solenoid with 4 connections, but this newer starter has only three.

From what I gather, only three terminals are necessary for the starter to function with carburetor models: 1. the negative ground; 2. no 50; and 3. No. 30 (from battery). I would expect the cs models might be able to do without the (16) terminal if they used some sort of pointless ignition system. But - the djet equipped models evidently need that fourth post (16) as part of a timed relay/bypass to the coil and the fuel pump during startup. Or do they?

Anyone use the three-terminal-solenoid starter on a djet? What was connected, bypassed, rerouted, or rerigged? If this is more trouble than its worth, I will look for another starter that will work.

FWIW, the realoem diagram is somewhat misleading in that it looks like a three-pronged affair. PN 12411272150. The usual replacement/upgraded starter looks to be an SR95X. As I said, the sticker on the newer 3-pronger is missing, so I can only guess at what it specifically fits (I have an inkling it is an SR41X for a 635csi but I am far from certain).

Thanks.

 

[DougE]

Starter

All of the early 4 cylinder and 6 cylinder engines use an SR71X Bosch, a couple of years back Bosch stopped remanufacturing the SR71X and started putting SR440X permanent magnet starters in the box with an SR71X sticker. The SR440x is what was used on the early M3 with the S14 engine. The part number you listed crosses to either the SR95X or SR41X which appear to be interchangeable and were used on the 5 and 7 series through around 1987 and the 6 series through 1989.

Doug

 

[nashvillecat]

The part number you listed crosses to either the SR95X or SR41X which appear to be interchangeable and were used on the 5 and 7 series through around 1987 and the 6 series through 1989.Doug

Appreciate the response.

I am aware that all of these starters are dimensionally identical, so they will bolt up in place of the E9's OEM starter. Unfortunately, that does not address the missing terminal 15 on the "newer" style starter. Since my initial post, I looked at 2 tii's, both of which had the four posts on their solenoids. I also looked at another M30 block and the solenoid bolted to it also had 4 posts. A friend tells me he thinks he has an SR41X with three terminals. But the starter is not bolted to anything and he can't tell me what car it is for or how it might be wired.

Again, my point is how to address the missing terminal (16) on the newer style starter. If this were for a non-injected model without a ballast bypass, I probably would not have been asking. Is the wire normally attached to the (16) terminal left unconnected? If so, does that not interfere with the ballast by pass and fuel injection cut off?

Although I can't think of one, that does not mean there isn't an obvious answer out there - (other than obtaining a starter with the four terminals). :wink:

Thanks

 

[Gosch]

The starter has 4 contacts
1. Masse = Negative Ground
2. 30 = Power Battery
3. 50 = Start command from the ignition switch
4. 16 = (not15) battery direct power during startup

The ignition coil has a resistor, either as a resistance incorporated in the cable harness, or later as a separate resistance near the ignition coil.
During the startup process is connected through contact 16, the direct battery voltage to the ignition coil to increase the ignition.
This is the only justification
Gosch

 

[nashvillecat]

Correction noted

The starter has 4 contacts
1. Masse = Negative Ground
2. 30 = Power Battery
3. 50 = Start command from the ignition switch
4. 16 = (not15) battery direct power during startup

The ignition coil has a resistor, either as a resistance incorporated in the cable harness, or later as a separate resistance near the ignition coil. During the startup process is connected through contact 16, the direct battery voltage to the ignition coil to increase the ignition. This is the only justification Gosch

You are correct that the "bypass" post on the solenoid is marked "16" and not "15." The initial post had question marks reflecting my doubt as to the actual number (15 or 16), and I have since corrected those posts. 37 years of cooking in an engine bay hardly makes for easily read numbers. (FWIW, my handwritten notes list three connections: thick black/red (30); black (50); AND grey/red (61)?.

Getting back to the original post, isn't this same circuit (16) tied to the djet fuel injection system as well as the coil ballast bypass? And, in any case, is there a simple-solution to wiring the three-terminal equipped solenoid to a csi model?

As I have said previously, this may be a futile exercise, but maybe not.

Thank you.

 

[JhwShark]

Getting back to the original post, isn't this same circuit (16) tied to the djet fuel injection system as well as the coil ballast bypass? And, in any case, is there a simple-solution to wiring the three-terminal equipped solenoid to a csi model?

As I have said previously, this may be a futile exercise, but maybe not.

Thank you.

Yes, they are in the #16 circut to fuel system (injected and carb'd) for Start purposes, once key is released to ON it uses the Black lead which goes there as well.

We would need to see the schematic of the SR41X to really give a solid answer?? Or find a 633i/733i wiring diagram link for me, and I could give further input.

Jon

 

[nashvillecat]

Yes, they are in the #16 circut to fuel system (injected and carb'd) for Start purposes, once key is released to ON it uses the Black lead which goes there as well.
We would need to see the schematic of the SR41X to really give a solid answer?? Or find a 633i/733i wiring diagram link for me, and I could give further input.

Thanks for kind offer. I am still not sure the 3-pronger is an unidentified SR41X or a who-knows-what. The fact that the solenoid has three terminals leads me to conclude this was from an even later model with sophisticated 80's spaceshuttle motronic injection and ignition. (As opposed to the project mercury M10's and M30's using 4-prong technology.)

Misplaced part of the manual dealing with this. Thought the (16) circuit was part of a time delay that deactivated the fuel pump, if the engine quit, - as a quasi safety feature. I was guessing the ignition ballast bypass could be overcome, or if not, the result might just be reduced voltage to coil and hard starting on cs models. If the circuit also controls idle jet solenoid shut offs, then maybe the same issues would afflict all e9 models.

As OEM starter seems to work, and replacing it with a much lighter starter would require more ballast to keep the front end too high above the water line, this is probably not worth the effort.

Thanks

 

[Gosch]

Forgive me if I do not understand something right. My English is not perfect and I use the Google translator.

Assuming that the ignition system is has a good working condition, or because a Pertonix upgrade and the engine is a clean setting / combustion, you need this start raising (# 16) not .....
This feature is only good for city vehicles with spark plugs are often smoke?? by short distances, or to improve the depth of winter in subzero temperatures started.

Injection:
The D-Jetronic needs this contact not at all.
The contact # 16 was only used on the L-Jetronic into the starting phase, for running fuel pump, which then kept the running engine through a contact in the LMM (AFM were in English)

 

[nashvillecat]

Forgive me if I do not understand something right. My English is not perfect and I use the Google translator.

Assuming that the ignition system is has a good working condition, or because a Pertonix upgrade and the engine is a clean setting / combustion, you need this start raising (# 16) not .....
This feature is only good for city vehicles with spark plugs are often smoke?? by short distances, or to improve the depth of winter in subzero temperatures started.

Injection:
The D-Jetronic needs this contact not at all.
The contact # 16 was only used on the L-Jetronic into the starting phase, for running fuel pump, which then kept the running engine through a contact in the LMM (AFM were in English)

Thank you for your response. I appreciate the participation. Wenn es zu den Mechanikern kommt, mein englisches IS-IS nicht sehr gut. Moglicherweise sollten wir Spanischen versuchen? :wink: :wink:

Ignition
I do understand that circuit 16 bypasses the ballast resistor and provides 12 volts to the coil - at startup. There are times, especially when you have a marginal battery charge, where this could be significant. installing a simple switch around the ballast resistor could make the lack of a circuit 16 terminal on the starter a non-issue.

Fuel Injection
This may be the hang up. I rebuilt my engine many years ago and runs and starts well. The original starter has some wear on her teeth and elsewhere; nevertheless, she continues to function, so I have continued using it. The starter solenoid has the 4-terminals. When I first noticed the difference in starters that prompted my original post, I tried an experiment. I disconnected the wire to terminal 16 on the solenoid and was unable to start the engine. Whether this was due to the ignition or the fuel system is unclear but I tend to think it fuel related.

I cranked the engine with the coil high tension lead disconnected from the distributor and observed a discharge of blue sparks although they lacked some of the "snap" I would have expected. By an unscientific process of elimination, I concluded the 16 circuit is vital to the djet. For fear of having a dead battery, I reconnected the wire and drove off. Later, while driving the car in a parking lot, the engine stalled unexpectedly. I looked at the wiring and noticed the wire to the 16 terminal on the starter was not connected. I reconnected it and have not had any problems since then.

You may be correct that circuit 16 is not related to or necessary for the djet system to function. Much of my wiring harness and fuel injection components are 35+ years old and there could be some wiring modifications that change the way things were originally designed to function. This could be significant as I have had my fair share of minor problems with corrosion and worn relays, sensors, fuel pumps, throttle position sensors, pressure sending units, grounds and ignition switches.

Other's experience may have different experiences. I find that leaving the j-jet equipped ignition switch in the "on" position for a few (20-30?) seconds - without starting the engine - results in the fuel pump cutting out or switching off. I have not explored this in depth, mostly because it has never been necessary. (I mentioned before that I have presumed this to be safety related.) Perhaps without justification, I have assumed this feature or function is somehow dependent upon or affected by circuit 16.

Again, my conclusions are not scientific and based only upon my limited observations.:wink:

 

[Arde]

Thanks for kind offer. ... Thought the (16) circuit was part of a time delay that deactivated the fuel pump, if the engine quit, - as a quasi safety feature. I was guessing the ignition ballast bypass could be overcome, or if not, the result might just be reduced voltage to coil and hard starting on cs models. If the circuit also controls idle jet solenoid shut offs, then maybe the same issues would afflict all e9 models.
...

Thanks

From looking at the schematic superficially I don't think the (16) circuit is related to fuel pump deactivation upon stall. The starter would have no way of knowing the engine stalled. Appears to be just a bypass for the ballast. In any case if you'd like to use a three contact starter you can reproduce the (16) circuit by adding a relay and whatever the old starter was doing will be done by the relay.

 

[nashvillecat]

Had I not received your encouraging responses, I probably would not have looked into this much further, so thank you all.

I found a very shopworn copy of the FI schematic. While I am not absolutely certain they apply to my current djet configuration, the lines clearly show that circuit 16 goes between the coil and the starter - indicating it is strictly for bypassing the ballast resistor when the starter is engaged. I also see no indicated connection (in the diagram) with the djet fuel injection on circuit 16. Moreover, it appears that the 30 terminal is directly involved with the fuel pump relay and presumably, the fuel cutoff. ( I say this with a slight amount of trepidation since this copy of the schematic contains both the original lines and blood spattered annotations.

Based upon this confirmation, I am relatively confident that the spare “new-style” starter can substitute for the 4-prong starters. Now, the only rub is determining why the car would not start and the engine would cut out if the wire to the 16 terminal was disconnected. I am not aware of anything obvious, like an intervening anti theft device and all of the electrics (excepting rear defogger) seem to function adequately. However unlikely, it is possible that there is an unseen broken wire or short somewhere - or something inadvertently connected to the coil or the starter.

Danke again.

 

[Arde]

...
Now, the only rub is determining why the car would not start and the engine would cut out if the wire to the 16 terminal was disconnected.
...
Danke again.

A naive speculation would be that when the wire was disconnected the cable was just casually hanging around and it sporadically made ground contact thus grounding the coil.
I had such an intermittent short from a lose wire that would happen at high speed only...

The no start could be because you really need that extra oomph, otherwise why the bypass at all?

 

[nashvillecat]

A naive speculation would be that when the wire was disconnected the cable was just casually hanging around and it sporadically made ground contact thus grounding the coil. I had such an intermittent short from a lose wire that would happen at high speed only...

The no start could be because you really need that extra oomph, otherwise why the bypass at all?

The side-of-the-road experiment was not done using rigorous controls nor did it involve double blind studies. The engine stalled in a parking lot so high speed was not involved. Nevertheless, you may be right, there could have been another loose wire (or two) involved and I had just started driving the car after it spent a long hiatus in a superhumid garage. I really can't say. The strange thing is I vaguely remember not hearing the hum of the fuel pump. May have to repeat the experiment when time permits.

Regarding the need for extra oomph, it does have higher than normal compression and does seem somewhat temperamental with the cold start valve enabled and the plug gaps are pretty wide and the blaupunkt is occasionally set to a loud FM station . . . . Hmmmm.

Thanks.

 

[Arde]

The side-of-the-road experiment was not done using rigorous controls nor did it involve double blind studies. The engine stalled in a parking lot so high speed was not involved. Nevertheless, you may be right, there could have been another loose wire (or two) involved and I had just started driving the car after it spent a long hiatus in a superhumid garage. I really can't say. The strange thing is I vaguely remember not hearing the hum of the fuel pump. May have to repeat the experiment when time permits.

Thanks.

I may have misled you. I meant the wire from the coil to the starter IS the loose wire.
I assume when it got unplugged it did not somehow get covered with electrical tape at its tip, so the experiment to repeat is to disconnect it but cover it with electrical tape. Good luck.