Converting SPI to Carb

[MPlayle]

The new thread:

The FI is better since the vacuum line replacements, but still has some hesitation spots - occasionally from idle, mostly when trying to give a small acceleration while cruising, such as starting up an incline.

From the research I have been able to do, it is likely an aging sensor.  The problem: most of the sensors are now NLA.

So, I will be converting it to a carburetor.

I have started the process of getting the necessary parts together.

Found a low pressure (2.5 - 3 psi, 42 GPH, model 42S by Mr. Gasket) fuel pump locally.
A carb model fuel tank from a seller on this forum.
The rest of the main parts from 7Ent:
- complete carb kit (carb, manifold, linkage plate, filter, spacer, appropriate gaskets)
- electronic distributor
- coil matched to the distributor (details below)
- accelerator and choke cables
- temperature sender
- manifold to head gasket

I plan on using the existing wiring harness and stripping out the unnecessary portions, retaining the necessary ones only.

The new coil is required as the later carb models used the ballast wiring to the coil and the SPI is not ballasted.  The coil is internally ballasted - a standard Lucas coil for the earlier, non-ballasted wired systems.

I will be attempting to plumb in the later carb style coolant temperature sender so that the factory temperature gauge still functions.  I will probably have to find an appropriate 'T' fitting to put it in the line out from the sandwich plate to the manifold/heater.  I don't want to pull the head to have it drilled and tapped for putting the sender there and the sandwich plate is likely too thin to drill and tap successfully.  I looked into the different sandwich plates as the MPI one has a sender hole tapped, but it does not have the stud hole for the top radiator mount needed for the existing side-mounted radiator.

For the wiring changes, I will be going back and forth between the SPI diagrams and the last of the carb model diagrams for lining up the changes.  They are not much - the temperature sender, ignition switch to coil/starter relay and fuel pump.

I will post the progress here.

[LilDrunkenSmurf]

As an SPI owner, I am interested in this.

[MiniDave]

A very common conversion in England - it has it's plusses and minuses - on the plus side it's less complicated and pretty much trouble free once done, the minus is you have to use the choke on starting and warmup and it's a little more maintenance - but reliable.

Which carb, HIF44?

[MPlayle]

I did a lot of reading on the UK MiniForum about the conversion.  If the full selection of sensors were still available, I would have gone with refurbishing the FI.  As it is, with most sensors already NLA or nearly so I am converting.

I plan on trying to do a decent effort at documenting the process for others here to follow if necessary.

I will be putting a HIF44 on it.  It will be with the BDL needle.  (The 7Ent kit part # SEVR0001.)

I am going with their electronic distributor 59D4E as well.

[MPlayle]

No real update, just a "bump" to keep the thread from falling too far.

The tank has arrived.  The other main parts are "in transit" a show due to arrive Thursday.

Then the "fun" begins.

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[tmsmini]

A couple of companies make the elbows that have the threaded port for the temp senders.
It does mean the temp is post thermostat open at that point, but I do not believe that is an issue.
I collected a variety of thermostat sandwiches and elbows before figuring out that I needed a custom version.
Let me see what I have, if the need is not immediate.
Terry

[MPlayle]

Hi Terry,

The need is not yet immediate.  I have not yet started the process - waiting on the parts from 7Ent.  The most I may do this week is see about getting the SPI tank out of the car as I may have someone interested in acquiring it for their project.

Let me know what you may have.  The temperature sender I have ordered is part number GTR0101.

I need to retain the SPI style sandwich plate for the mounting point for the top radiator bracket.

I will be taking the hoses from the SPI manifold and using those on the carb manifold and had thought about finding a 'T' fitting to plumb the sensor in that flow as it is pre-thermostat flow.

[tmsmini]

Looks like I must have given them away.
I had one like this:
http://minisport.com.au/mini-forward-facing-thermostat-housinga-with-temp-adaptor



Not sure the angle is completely right for your application

[MPlayle]

The DSN ones are shaped just like the factory one I have.  It has the same flat spot.  When I consulted with Jack at 7Ent, we both were concerned whether that part of the plate was meaty enough to be drilled and tapped for a sensor or sensor adapter.

(Jack pointed out the sensors have a taper to the end for seating into their port and sealing.  Easier to drill and tap for the adaptor that will flat seal and has the taper inside for the sensor.)

I think I have some adapters left over from a past project that might work for the sensor.  When it gets here, I will check, then see about either having the sandwich plat drilled/tapped or finding a 'T' fitting the adapter will fit.

[tmsmini]

This is what I ended up doing for an MPi engine:


It also required a custom top bracket. It could have been widened to accommodate the single bolt top bracket and that probably would have been easier.

[MPlayle]

Looks nice.  Did you put a temperature sender in one port and the heater take-off in the other?

Unfortunately, making something like that is beyond my resources.  I would also need to have either a custom top radiator bracket like you mention or the plate modified to permit using the stock top radiator bracket.

[tmsmini]

My purpose was to provide a port for the mechanical coolant temp gauge and a port for the coolant temp sensor required for the EFI. Even though it is an MPi engine, I reverted to the heater take off by cylinder 4.

Another Mini owner machined them for me as it is beyond my abilities as well.

[MPlayle]

Got started on the process today as I have a prospective buyer of the SPI tank.

I siphoned out the fuel from the tank as much as I could - transferring it into my daily driver to consume it.  I then removed the trim kit in the boot, the spare and the battery.  I also removed the bootlid from the car to make getting the tank out a little easier.

I disconnected the electrical leads to the tank (need to label them for connecting to the replacement tank), disconnected and removed the trap and line for the vent, cut loose the fuel feed and return and pulled the tank out.

I also removed the fuel pump and the sender to finish draining the tank and let it all dry out for being able to ship it.

I did not take pictures, but with take some tomorrow.

Removal from the car was very straight forward - remove the lower rear bolt for the tank strap, swing the strap back some and wiggle the tank to the side and out.

[MPlayle]

Some pictures of yesterday's progress:

The replacement "carb" fuel tank that is going back into the car shown with the new sender.  I need to do a little cleanup on it before installing.



The "empty" boot with the lid removed to make the tank swap easier.  I already have the old tank pulled out.



I will be cleaning up the routing of the wiring and trimming/removing the unused fuel lines.  One will get trimmed short under the car and the other two completely removed.  The one retained will become the hard feed line under the car for the carb.

I pulled the old sender and fuel pump from the SPI tank.  I need to let the tank and bits dry out completely for potentially sending to a new home.





Not sure what I am going to do with the vapor trap that was on the vent for the tank.  This connected to one of the hard lines going to the front of the car - presumably to the charcoal canister and purge valve to recycle the vapors through the intake.

[94touring]

What's up with the boot straps/chains?  I didn't put those on there.

[MPlayle]

The original style cable straps were a tad too long and the lid and license plate were hitting the bumper.  I got some jack-chain at the hardware store and put them there sized just a tad shorter to bring things just off the bumper.

I have since adjusted the positioning of the license plate and may go back to the original cables.

[MPlayle]

Not much progress - taking care of family medical issues with my parents ha been taking much of my time.

I did get a little done.  The old FI tank is packed and ready for shipping to a new home once I get the destination address.  I started the preparation of the replacement tank.  I put a stainless steel scrubbing pad on the end on a long screwdriver and "swabbed" out some of the surface rust inside the tank and vacuumed it out.  The filter on the pickup line inside the tank is still intact and looks in very good condition.  I'm not going to try to remove it.  I then took the scrubbing pad and "sanded" half the outside, then put primer on it.  I'll do the other side next and then a coat of Rustoleum 'Semi-Gloss' black before putting it in the car.

[MPlayle]

A bit of progress today.

I got the replacement tank all painted.



I also began the process of identifying things to come off.  I will need to remove the original fuel filter and select the appropriate hard line to keep and remove the other two.

Here is the original fuel filter to get removed.  I plan on trying to put the new fuel pump in its place.



The lines running to the front.  I will keep one - likely the one coming from the fuel filter as it already ends in about the right place in the rear.





Starting to remove stuff in the front.  I removed the air filter housing and began disconnecting the fuel lines and crankcase breather system in order to get a better view of the ends of the hard lines coming from the back.  One of the lines already has the right length of fuel hose for wrapping around to feed the carb.  Hopefully it is the feed line from the fuel filter in the rear.





The air filter housing and breather lines removed.  I may try to re-use part of the breather lines for connecting the breathers to the carb.  I can figure a way to carefully remove the one small line and cap the extra port on the bigger line.  That should let me use the main line again for taking the breathers to the carb.

[MPlayle]

A bit of progress today.

I removed the unused vapor recovery line and fuel return line from under the car.  I also removed the purge valve and charcoal canister.







Next I removed the fuel injection manifold and throttle body.  A couple of the studs came out of the head instead of the nuts backing off, but no big deal to fix.







I also got the new fuel pump mounted.  I have not yet hooked up the plumbing from the tank to the pump or the pump to the remaining hard line under the car.





Next was getting the replacement tank back in place and secured.





Finally, I separated the exhaust manifold from the head for replacing the gasket and removed the ECU.





Next up will be sorting the wiring changes.  I will be making a close comparison between the wiring diagrams for the last of the carb'd Minis and the SPI wiring diagrams.  I will make a list of the cross-overs by function and color code for others to reference.  This stage will entail unsheathing the harness sections involved to retain/adapt those segments necessary and removing all the no longer necessary portions.  I may tidy up some of the lamp wiring as well.

[94touring]

Spotted my backwards installed zerk :-[

[MPlayle]

No really any visible progress since the last update.  I've been reviewing wiring diagrams and identifying harness connections for the next stage.  Next will be stripping down the ECU wiring harness to remove all the no-longer-used connections and simplifying the relay connections.

By the way, would anyone be interested in any of the stuff removed?  (The fuel tank and pump have already been sold.)  The excess hard lines from under the car had to be chopped in order to get them out without dropping the subframes, so those are likely scrap.  The ECU, throttle-body-manifold assembly, and charcoal canister are available as is the purge valve and vapor trap.  The "distributor" will also become available soon.

A token amount plus shipping would be nice.  Otherwise they will all go to the dumpster.

[94touring]

Would using a new carb model harness work just as easy than going through the spi harness?  You'd need to pull out one and install the new harness but would it be cleaner and simpler?

[MPlayle]

It probably would be easier, but I am trying to avoid rewiring the lights and figuring out how to join the rear harness of the SPI system to the front harness of a carb system.

The easiest would be to follow the basic directions on Mini Mania where they leave the SPI's ECU harness in place.  For that, they jumper some connections at the big ECU connector and splice in a relay.  The drawback is it leaves all the extra connectors and unused wiring all over the place.

The big delay is I spend a big chunk of time checking up on my parents daily.  Mom is undergoing chemo treatments for a lymphoma and dad's health has been on the poor side for some time.  I am now their driver for appointments and such as well as the "sonny-do" person.

The contracting work I do from home gives me the flexibility to be caregiver.

[MPlayle]

A little bit of progress today.

I got some fittings for inserting the replacement temperature sender into the system.  I plan to run the coolant lines from the SPI manifold to the tube in the carburetor manifold and will insert the temperature sender in that loop.

I had some adapters left over from replacing a mechanical temperature gauge/sender on another Mini.  I selected one of those and soldered a grounding wire around it.





The next two pictures show the fittings for putting it all in line - including the 5/8 to 1/2 adapters necessary.





I also started tackling the ECU wiring sub-harness.  I pulled it back along the routing and unwrapped it for sorting out the lines I need to keep and which to remove.

[MPlayle]

A small amount of progress yesterday.  I forgot to take pictures during the work, but took some showing the end result of yesterday's effort.

I worked on cleaning up some of the wiring associated with the conversion.  In doing so, I had to unwrap the ECU sub-harness as shown in the previous photos.  I also had to unwrap a portion of the main harness to expose the wires for the purge valve and the unused auxiliary fan (was not re-installed during the front end restoration?).

The two yellow relays next to the fuel pump inertia switch were the aux fan relay and the Lambda (O2) sensor relay.  The O2 relay wiring was part of the ECU sub-harness and was removed with that.

The wiring for the Aux fan was traced back to near the 'Y' in the main harness where the ECU sub-harness connector comes in.  I clipped the feed lines (non-black) at different lengths, folded each end over and sealed in heat-shrink tubing.  One of the wires (Black with a green trace) went from the relay to the unused connector for the fan, so was just discarded.  The ground (black) wires I connected all together with a ring-lug and attached to the ground point where the dim-dip resistor is mounted near the radiator.

I then pulled the fuel pump inertia switch lines back to the 'Y' in the main harness, clipped them to remove the switch and used a butt-connector to bypass the switch function.  I covered the connection in heat-shrink tubing and laid it along the branch to the ECU harness connector.

I then re-wrapped those sections of harness and tucked them up out of the way.





I also cleaned up the stains from an apparent radiator overflow event and put wrapping (plastic wire conduit) over the portion of the main harness running along the clutch side inner fender to tidy its appearance.