Converting SPI to Carb

[MPlayle]

A bit more progress on the reworking of the wiring harness.

As noted, I am modifying the ECU sub-harness to remove all the ECU and sensor connections.  There are some wires in the sub-harness that need to be retained as they are(oil pressure light, alternator light, tachometer feed).  Others need re-connected through replacement relays for part of those in the factory relay box.

I am going with two relays - one 5-pin and one 4-pin.  The 5-pin relay with be triggered by the ignition switch to power the fuel pump and feed the coil+ side.  The 4-pin relay will be the starter relay replacement.

In removing the no-longer-used connections, I took a rather "destructive" approach and clipped out the "easily located" sections first, rendering most of the removed stuff pretty much useless.  Things like the temperature sensor connector, manifold PTC heater connector, fuel injector connector, stepper motor connector, throttle potentiometer connector, air temperature sensor connector just got traced back to the ECU connector, cut off and tossed aside.

I then began tackling the rest of the harness, labeling the lines I would need and tracing out the lines from the connector for the sub-harness to join the main harness.



Starting at the connector to the main harness:

• There were 2 thin wires I could not identify on the wiring diagram for the SPI system: a) red with a white trace, b) dark green with what looked to be a white trace.  Both of these went directly to the ECU.  I suspect they were part of the immobilizer? These both got clipped, folded and capped in heat-shrink.
  
• There was one thin white with grey trace that would be for the accelerator pedal switch if equipped.  My ECU did not use that switch.  That wire was also clipped, folded and capped in heat-shrink.
  
• The thin green with blue trace wire is the line from the temperature gauge to the ECU.  This will be re-used as the line from the gauge to the new temperature sender.  It got clipped at the ECU connector to retain the most length of proper colored wire.
  
• The thin white with brown trace is for the oil pressure light.  It is being retained as-is.
  
• The thin brown with yellow trace is for the alternator dash light.  It is being retained as-is.
  
• The thin white with black trace is for the tachometer feed from the coil- location.  It is being retained as-is.
  
• The thick white with red trace is for triggering the starter relay.  It will be reused for the same purpose on the replacement starter relay.  (NOTE: This starter relay is not the solenoid, but sends power to the solenoid.)
  
• The thick white with pink trace is the return side of the trigger for the starter relay - paired with the white/red in #7 above.  This wire is a color mismatch from the wiring diagram - the diagram shows it should be white/light-green (automatic transmission) or black (manual transmission).  The connection was confirmed by continuity test through the original relay box.  This white/pink wire will be re-used with the white/red for the starter relay.
  
• The thin white wire is the main switch line from the ignition switch.  It ran to both the relay box and the ECU and had a three-way joint in the middle.  It got clipped at the joint and will be the trigger feed for the relay controlling the fuel pump and feeding the coil+.
  
• The thick brown with grey trace is the power from the fuel pump relay back to the inertia switch that was already removed.  It still feeds the line back to the fuel pump, so it was clipped at the relay box for re-use on the replacement relay.
  

That covered the wires at the connector to the main harness.  There were the remaining wires at the relay box:

• The two thick solid brown wires are main power lines into the relay box.  Inside the box, they route to multiple relays in different manners.  For the conversion, I was concerned with how they feed to the fuel pump and starter relays.  Both of these got clipped at the relay box for re-use.
• The thick brown with red trace is the controlled output from the starter relay to the starter solenoid.  It got clipped at the relay box for re-use.
• The medium thick solid brown to the Lambda (O2) relay is the main switched power into that relay.  Rather than trying to remove it from the solenoid connection, I clipped it at the Lambda relay for re-use as a switched power in at the new fuel pump/coil relay.
• The thick brown with pink trace is a main power output from the relay box to multiple items, including the coil+.  It went to a multi-line joint shortly past the relay box.  I traced the feed from the coil+ to that joint and clipped it there for re-using that portion for the coil+ from the new fuel pump/coil relay.

This picture shows how the unused lines were capped off.  The same method was used for the lines in the main harness that I capped earlier.



Here are a couple shots of the reworked sub-harness coming together with the replacement relays in place.  I have started securing portions together for fitting and routing before wrapping in more of the plastic wire conduit like the re-wrapped main harness.





What I forgot to get a picture of is the O2 sensor removed from the exhaust down-manifold.  I had the port plug left over from adding an air/fuel ration meter on another project.  I pulled out the O2 sensor and installed the plug in its place.

[MPlayle]

More progress today.

Finished up the reworked sub-harness and tidied it with more wiring conduit.  From the connection to the main harness:



To the replacement relays:



Around to the front:



And over to the starter, distributor (still has the old one installed) and leads to the alternator:



Even tidied up the wiring for the auxiliary lights:



I then turned to installing the new choke cable and fully routing the "dummy" heater cable into the engine bay.  That way it is already threaded through the firewall in case the desire to re-install a heater valve should come up.

This shows the switch panel loose and the cables re-threaded.



To loosen the switch panel, I carefully pried out the rocker switch for the headlights to get a finger behind on the nut for the heater cable.  I then turned the heater cable housing slightly use needle-nose pliers to grip the casing just behind the knob.  This was enough to loosen the nut and then I fully undid the nut with the finger through the headlight switch hole.  The other side turned out to have the support bracket loose, so it pulled forward and out with the panel.  The support bracket was held to the back of the panel by the blanking button for where the choke cable would install.

Here is the blanking button and spring clip that held it in place:



A close-up of the cables through the switch panel and the mounting brackets:



The cables through the firewall into the engine bay:



For mounting the switch panel back up, it was basically the reverse of the removal.  I did find a proper fitting nut, washer and star washer for the choke side mounting bracket so it is now fully secured.

The switch panel back in place waiting for the headlight switch to go back in - I had just finished tightening the heater cable nut.



The switch panel all back together:



And the heater re-mounted:

[MiniDave]

You're making great progress......hope you get to drive it again soon!  4.gif

[MPlayle]

Thanks.  Juggling schedules (contract work and care-giver duties) has slowed things some, but I have been able to keep it moving forward.

Next up is mounting and plumbing in the carb.

[MPlayle]

Not much progress today.

Got the seats back in from yesterday's work under the dash.  Started the fitting of the carb and intake manifold - lots of trial fitting followed by filing adjustments to the intake flanges one at a time so that the captive-washer nuts will fit properly.  Then finding some appropriate thin fender washers to cut and use for shims.

It may be the end of the week before I get back to it.  Mom goes into the hospital Monday for her next round of chemo, so the "care giver" duties dominate for the week.

[tmsmini]

Although I am doing the reverse process from you, this is what I did with the breather pipe. I removed the piece for the purge valve, capped the one outlet in the middle and adjusted the tab to support it.

[MPlayle]

I am doing something similar with my breather pipe.  The SPI breather pipe appears slightly different to start.

I did get a bit of time this afternoon to actually get the carb mounted (including the breather pipe).  I still have a bit of the plumbing of it to finish along with hooking up the accelerator and choke cables.

[LilDrunkenSmurf]

See, at this point, I want to keep the SPI, but I just want to tidy up the very busy engine bay.

[MPlayle]

I would have kept the SPI, but it was getting hesitation spots in different places of the rev range that indicated potential sensor issues.

I went looking for replacements for all of the sensors and found 1/2 are 'NLA'  - 'No Longer Available'.  That coupled with the difficulty getting the ECU serviced and/or locating someone with the correct ECU reader/reset tool that would be willing to loan it, ... it meant time to consider the conversion or some for of replacement.  The conversion back to carburetor seemed the least costly and least difficult/complex.

[tmsmini]

For future reference, have reader, will loan..but don't expect a reader to solve an issue. The information they provide has to be considered along with everything else. It is still an A-series under all that extra stuff.
Terry

[MPlayle]

Terry,

Very kind to offer the loan of the reader - usually folks are reluctant to let them out of their sight.

I see the reader as it is meant: a diagnostic tool to assist in finding issues.

[LilDrunkenSmurf]

Not that it's cheaper or such, but did you ever look into a standalone ECU like megasquirt or something, where you could replace OEM sensors with some aftermarket/generic ones?

[tmsmini]

Smurf: I have two systems on the shelf, Microsquirt and Specialist Components. Well the SC one is in the car.

There is no question that there are some implementation issues. On the other hand I have over 100K miles on an MPi car with just normal A series issues.

[MPlayle]

I had followed several other folks threads on the changing to a standalone ECU system.  The costs for the basic system tended to start a significant amount higher than the total cost of the carb conversion.

[Merlin]

FI Gets really tricky with these engines because of the siamese intake ports on the heads. Typically the intake for cyl 1 will draw and then cyl 2 will open right after causing some interesting fueling issues with ensuring that both cylinders get the same quantity.

standalone would work better with an aftermarket head that was a 7 port or 8 port as the intakes for each cylinder would be dedicated and allow for better metering of the fuel.

Doesn't mean it cant be done though.... Typically I have seen a hybrid of the SPI setup with some new code added to the megasquirt so that the ECU looks for one injector instead of four.

[LilDrunkenSmurf]

What about micro squirt?

[tmsmini]

It is not clear to me that there are strong benefits to doing this relative to cost, but I am committed to and continuing to work on the systems.
This was more of learning project for me, but I am still looking for a reliable daily driver solution out of my learning project.

Microsquirt and Megasquirt are pretty much the same, but different packaging. There is code to deal with the port issue.
There are newer Megasquirt versions that deal with the port issue in a different fashion.

[MPlayle]

Costs so far are about $1300 all total.

I bought all the major components through Seven Enterprise for about $970 shipped (complete carb kit including manifold, spacers and filter, electronic distributor, coil, cables, temperature sender).

I've spent about $120 on the "incidental bits" such as the fittings for the temperature sender, hoses, fuel pump, clamps, relays, connectors.

The replacement tank was $175 shipped.

I could have saved some more if I had ordered from some of the UK suppliers and gone with a different distributor.

[MPlayle]

A little more progress today, but does not look like much.

I needed to put a thicker washer setup on the manifold mounting for the center exhaust branch to make a slightly better seal to avoid an exhaust leak.  That meant undoing part of the previous progress and then inserting the extra half washers.  Got that done and a bit more of the connections and plumbing of the carburetor in place.

The first picture shows the fuel line (with filter) and the manifold heater return line in place.  The second picture shows the accelerator and choke cables installed as well as the temperature sender fully installed.





I have one more connection to do for the cooling/heater system to be ready for refilling and burping.  Then it will be setting the basic timing and replacing the distributor and coil followed by testing and tuning.

The end slowly approaches!

[MiniDave]

Don't forget to put a grommet on the choke cable where it comes thru the firewall.....

I made my washers by starting with some really thick ones and welding a small blob on one side. then I ground the blob down till the washer lay flat on the manifold and still pushed on the exhaust manifold flange hard enough to seal it. I then marked the tops of the washers so I could always line them up right when I removed and reinstalled them again.

Do you think you have the end of the temp sensor far enough into the stream of water to get an accurate reading? My understanding is the whole end of the tube needs to be in the water.......

Lastly, make sure you have a good ground cable between the engine and the body, other wise your choke and throttle cables become the ground, and they don't like that!   ;D

[MPlayle]

I will be putting a grommet around the hole where the choke cable goes through the firewall.  I will probably re-use the rubber plug that was there and put a slot in it for the cable.

There is a thick braided ground strap on the clutch end of the engine.  I also turned the main ECU ground line into a secondary engine ground strap connecting to the head under the mount for the breather pipe at the clutch end.

The temperature sensor should be reasonably accurate in the setup I am using.  The adapter it mounts into has a gap all around the sensor tube with the end slightly proud of the adapter into the flow in the 'T' fitting.

[MiniDave]

I figured you were on top of it......just trying to contribute!   4.gif

[MPlayle]

I might not have remembered a grommet for the choke cable but for your reminder.

The other two items I was on top of.

I've read plenty over the years about other Mini owners experience with the choke cable becoming the engine ground strap.   :-\

I am using 1/2" ID fittings for the temperature sender.  It could have been done with 3/8" ID fittings as one of the adapters I have is that small; however, I did not like the very small amount of space for fluid to get around the sensor tube.  I also have a 5/8" ID adapter that would have provided lots of fluid exposure, but that would have made the whole assembly too large for that location.

The 1/2" fittings also matched the ID of the manifold heating tube.

The messy looking solder ring is a grounding strap for the sensor and runs back to the stud on the thermostat housing for the upper radiator mount.  I stripped back a long portion of wire and wrapped it both ways around the adapter the sensor seats into and soldered it all the way around so it is a solid connection.  Although some folks have suggested the coolant would be a sufficient ground for the sensor, I wanted the extra measure as the sensor is usually mounted in the head to get its grounding.

[jeff10049]

Yep, you need that ground wire coolant alone would not provide a sufficient ground. And would be a very bad idea you can turn your cooling system into a battery where electrolysis takes over and eats radiators, heater cores and engine blocks any time you have dissimilar metals water and add electricity you can get into trouble.

Some 3/4" heat shrink the good stuff with the glue in it over the fitting and wire with the wire bent to come out the top or bottom of the shrink looks cool and keeps the wire supported so it don't break off at the attach point.

[MPlayle]

Made some more progress today.

I buttoned up the coolant/heater lines and filled with distilled water.  (I plan to have the system pressure flushed again once running.)

I then started on the Distributor swap.  I marked the spark plug wires and removed the spark plugs - putting each plug back into the matching wire.



Next came addressing the cap for the old distributor.  I made note of which wire was for #1 cylinder for marking its position.



I removed and set aside the old distributor cap with the wires still attached.



This shows where I marked the body for where the #1 wire was located.



Next, I had to hunt for the timing mark on the crankshaft pulley.  The timing teeth are there, but rusty and so is the crank pulley!



I finally found it and put a small dab of silver/chrome paint into the timing mark on the pulley.



I then set it for initial static timing at about 7* to 8* BTDC.  That is just a starting point.  I will need to reference my manual for whether to use 7* to 8* or back it down slightly to 5* to 6* BTDC.



Here is where the old rotor ended up for that timing mark!



The new electronic distributor and new 3.2 ohm coil in place.  (The old coil was a 1.2 ohm coil.)



And ready for static timing.



I will need to check the manual for the static timing connections and procedure.  On Monday I will need to call Jack at 7Ent and verify it will be the correct procedure and connections for timing this electronic distributor.