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75 - 79, 80 Fast Idle Control Valve "FIV" Working on a replacement

Started by 79 Eldorado, February 02, 2020, 12:47:23 PM

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79 Eldorado

It's taking some time, about 1 year so far, but I've been making some progress attempting to create a replacement for the 70's EFI "FIV". It mounts on the air intake throttle body and allows some air bypass, which raises the idle RPM until the vehicle warms up. The core years are 76-79 but some 75 Eldorados had EFI and it was carried over in California through 1980 because the 79 system was able to meet CA emissions in 1980.

The pictures are without the internals and I am probably still at least a couple of months away from a working prototype. I was pretty happy with how the housing came out and so I thought I would let others take a look.

The blue one was created to verify my model would fit. The black one with silver (tinned brass) terminals is my housing ready for internal electronics and the wax actuator. The black one with brass colored terminals is a broken original which Bruce Roe allowed me to borrow to create my model without taking apart my car.

Scott

Link to a great related thread:
http://forums.cadillaclasalleclub.org/index.php?topic=118518.0


MaR

What material are you using to 3D print with? If it's PLA, that will work for the prototypes but it will not stand up to the heat of the engine bay. You will have to at minimum go with ABS and you may want to have them professionally printed out of something else completely from some place like Shapeways. That's who I have printing my body fillers that I'm working on.

79 Eldorado

Hi Mitchell,
The blue one is plain PLA. The black one is an engineering grade high temp PLA. I don't know if it will be or can be the final material yet. The company I bought it from is 3D fuel. They produce in the USA and they sent me the complete specification sheet. I would need to look at it again to quote exact numbers but it was roughly in the same league as bakelite. As you are alluding to there is some risk with 3D printed material because generally not many are geared to a long time functioning part. Even nylon should be in the presence of moisture to have it's best strength. I've also noticed that some older car parts made from nylon break down and become brittle. There is a material from Zortrax which if as advertised may be up to the task. I have also considered having a mold built but there is a limited market for parts like this and at some point cost becomes a factor. I will add a high temp cut-out in addition to a 2 stage heating. The original material is not marked but it seems to obviously be some form of Nylon. Any thoughts are welcome.

Scott

bcroe

These things are always tougher than they first appear.  Glad to have
an owner take them on.  Bruce Roe

MaR

Quote from: 79 Eldorado on February 03, 2020, 10:37:39 PM
Hi Mitchell,
The blue one is plain PLA. The black one is an engineering grade high temp PLA. I don't know if it will be or can be the final material yet. The company I bought it from is 3D fuel. They produce in the USA and they sent me the complete specification sheet. I would need to look at it again to quote exact numbers but it was roughly in the same league as bakelite. As you are alluding to there is some risk with 3D printed material because generally not many are geared to a long time functioning part. Even nylon should be in the presence of moisture to have it's best strength. I've also noticed that some older car parts made from nylon break down and become brittle. There is a material from Zortrax which if as advertised may be up to the task. I have also considered having a mold built but there is a limited market for parts like this and at some point cost becomes a factor. I will add a high temp cut-out in addition to a 2 stage heating. The original material is not marked but it seems to obviously be some form of Nylon. Any thoughts are welcome.

Scott

I'm more referring to the PLA material itself and my own experiences with it in under hood environments. Most FDM 3D printers will allow for other materials like ABS and other printing types like SLS have a multitude of material available. The main advantage of an SLS print would be the lack of a distinct layer structure that could cause weak points and cracking between the layer structure over time.

79 Eldorado

From the housing material side there is certainly more investigation needed. Based on the research I did I felt that there is a solution available and possibly a few.... the best solution is still not clear. It could be FDM 3D printed and might require an industrial type printer. As you mentioned another technology 3D printer may work better. I planned to ask more questions of experts and test. I was more concerned about being able to assess the aging of materials than initial properties. That's normally where the data is not so plentiful with thinks like 3D print material. Some of the FDM materials gain a lot of layer strength with post processing and the industrial printers can do a better initial job. The 3D Fuel material is worth investigating by specification but it needs to be tested in similar situations to actual. By description it's not your average PLA. I think injection molding in something close to the OE material still needs investigating further. A third option might be a metal housing with isolation for the electronics.

I tried to approach this by breaking it down into different tasks. The housing is only one. I put this on hold early in 2019 primarily because I was looking for a wax actuator which could work for a long time. The housing design needs to be customized to what is available. The electronics and control is another item. Even the terminals weren't perfectly obvious. The originals extend from the housing farther than most I've seen and there are so many male blade terminals finding the correct one is like looking for a needle in a haystack.

Anyway more to follow.

Scott

MaR

Quote from: 79 Eldorado on February 04, 2020, 11:54:39 PM
From the housing material side there is certainly more investigation needed. Based on the research I did I felt that there is a solution available and possibly a few.... the best solution is still not clear. It could be FDM 3D printed and might require an industrial type printer. As you mentioned another technology 3D printer may work better. I planned to ask more questions of experts and test. I was more concerned about being able to assess the aging of materials than initial properties. That's normally where the data is not so plentiful with thinks like 3D print material. Some of the FDM materials gain a lot of layer strength with post processing and the industrial printers can do a better initial job. The 3D Fuel material is worth investigating by specification but it needs to be tested in similar situations to actual. By description it's not your average PLA. I think injection molding in something close to the OE material still needs investigating further. A third option might be a metal housing with isolation for the electronics.

I tried to approach this by breaking it down into different tasks. The housing is only one. I put this on hold early in 2019 primarily because I was looking for a wax actuator which could work for a long time. The housing design needs to be customized to what is available. The electronics and control is another item. Even the terminals weren't perfectly obvious. The originals extend from the housing farther than most I've seen and there are so many male blade terminals finding the correct one is like looking for a needle in a haystack.

Anyway more to follow.

Scott

Don't forget that you can 3D print it in metal also.

79 Eldorado

I modeled all of the related parts even a simple portion of the throttle body to make certain the wax actuator pin is at the correct height. The plunger Bruce sent has a metal disk inside which the wax actuator pushes (see photo). It looks a little like the "dime" he's mentioned but he wasn't certain if he had modified this one. We both thought Cadillac may have placed a metal disk in the "plunger" for the pin to push against.

My question: If anyone has a spare or their car is apart to the point the dimension is easy to check could you measure the depth from the top of the flange to the bottom of the pocket (in the case of the part I have to the top of the metal disk)? I'm looking for confirmation of the dimension indicated by the blue arrow in the attachment.

Thank you,
Scott
PS: Yes I am aware 3D parts can be printed in metal. As I know the parts from professional sources are typically very expensive. In comparison there are a lot of businesses in this area which machine parts at a reasonable cost.


Phil Weber

I don't have a proper depth gauge but using a std micrometer I measure it to be .750 in. The contact surface for the plunger is metal.

Phil


79 Eldorado

Thanks Phil. That's what I measured as well. The only other thing which could explain why the original pin seems longer than it should be is if it's slightly extended at the temperature which I'm measuring it. I'm measuring the pin at around 65-70 degrees F so if it's shorter at a colder temp that could explain it. I didn't want to trust the pin extension only because I assumed measuring a 40 year old part I would have no idea how much it changed over time. As well I measured two and one measured 7.17mm and the second 7.91mm at the same temperature. I think I'll try placing one in the refrigerator and see if it ends up getting shorter. Even if the old part does not get shorter that seems like a good explanation. One part I was looking at does reduce the extension between 68F dropping to 59F.

Scott

79 Eldorado

After 24 hours to equalize there was no difference in actuator pin extension at 45F.

Scott

79 Eldorado

I just received a sample of the wax motor. It's shown for now in the temporary part I printed. To make certain the final has the correct length I had this one custom made so that I can adjust the length with a machine screw threaded into the end of the pin and then lock it with a nut. I'm still working on the heating portion and the control. I found some parts which should work but replies have been slow.

Scott

bcroe


79 Eldorado

Thanks Bruce. I need to contact the place where I was trying to get the heating and control items from. If I had the parts I identified it could go pretty quickly but they have been slow to reply even before the pandemic.

One of the other members, "AFI", mentioned the Zinc oxide paste in the original. I strongly suspected that white "wax" or "grease" which can be found even in images of NOS parts was never actually in the wax motor itself. I think what he wrote confirms that. My plan as of now is to create a custom brass sleeve which assembles over the wax motor. The heating unit and temp sensors will be mated to the brass sleeve. I need the heating unit and the temp sensor before I can finalize the sleeve though. Due to the space available and availability of parts I may need to make the housing diameter slightly larger; maybe a few millimeters. The housing I printed for test fit is the same size as the original in the photo.

Scott

79 Eldorado

I put together a temperature sensor adapter harness to allow me to measure the sensor resistance easily with multi-meter probes without disconnecting the sensor from the ECU. I'm posting it here because my plan is to use it for this project. While I'm testing I want to measure as many parameters as I can at once.

It was a bit difficult getting 2 wires in each side of the Weather pack but I could reduce the gauge to make it a little easier. I have one of the old Radio Shack Multi-meters which I love. I have 2 newer ones which have some nicer features but the Radio Shack is my favorite. One reason is the probe style. It seems it's always easier to get them to stay in place when I'm doing a job which I should have 3 or 4 hands instead of two.

I was wondering if there is a block connector designed for putting the probes in. Every search term I could think of was so generic I couldn't find anything and since I had a lot of the Weather pack connectors I decided to use one.

Scott

bcroe

Quote from: 79 EldoradoI put together a temperature sensor adapter harness to allow me to measure the sensor resistance easily with multi-meter probes without disconnecting the sensor from the ECU. I'm posting it here because my plan is to use it for this project. While I'm testing I want to measure as many parameters as I can at once.  Scott

I do not think you can measure the the sensor resistance when
plugged in, because there are other resistors connected inside the
ECU and voltage applied when it is on.  What you might do is add
a switch to your adapter, to momentarily disconnect at least one
side of the sensor from the ECU and to your ohmmeter.  An alternate
method is measure the operating voltage using your harness, which
can be used to know the resistance.  Connecting a few known
resistors to the ECU and observing voltage (no need to start engine)
will give enough points to make a transfer graph.  Or I could try on
mine, not quite identical.  Bruce Roe

79 Eldorado

Quote from: bcroe on April 05, 2020, 11:50:05 AM
I do not think you can measure the the sensor resistance when plugged in, because there are other resistors connected inside the
ECU and voltage applied when it is on.  What you might do is add a switch to your adapter, to momentarily disconnect at least one
side of the sensor from the ECU and to your ohmmeter.  An alternate method is measure the operating voltage using your harness, which
can be used to know the resistance.  Connecting a few known resistors to the ECU and observing voltage (no need to start engine)
will give enough points to make a transfer graph.  Or I could try on mine, not quite identical.  Bruce Roe

Very good point Bruce. When I have a chance to get to my Eldorado I could see what it reads with the adapter connected and vehicle off. Maybe it doesn't add much information anyway. Before I thought of this I was thinking I would simply probe places with my IR pyrometer. I really just wanted to record temperatures so even with the extra harness I would need to back out the temperature.

Thank you as always for your valuable insight.
Scott

bcroe

Quote from: 79 EldoradoThank you as always for your valuable insight.
Scott 

Teamwork gets the job done.  Bruce

79 Eldorado

I discovered something today...a part which seems is not needed and may even cause a failure mode. The other night I was reading one of the Cadillac Fuel Injection Diagnostic Manuals and I read the following: "A “latched” FIV is a condition where the retainer clip becomes “latched” below the seat, thus holding the valve in its closed off position, Fig. 2. To check for this condition, remove the valve and visually inspect."

I immediately thought that sounds like the retainer clip slipped down below the "Derby" (the sleeve where the plunger goes through see capture below). The interesting thing is I've been wondering how the assembly could let enough flow past it to work if the retaining clip is below the derby. That was the position it seemed it should be in because if not there seems to be no reason for the retaining clip. Once the clip goes past the edge of the derby there is only a fraction of a millimeter gap and when the actuator extends the plunger goes deeper closing the gap. The coil spring which pushes the plunger back up is pretty strong so the fractions of a millimeter could be slightly more if the clip deforms (it does deform/deflect some).

A couple of days ago while working with the plunger assembly I accidentally broke one of the legs off the retaining clip. I was in a  panic because I'm sure it's a hard to find part and second because I wasn't putting a crazy amount of force on it when the leg broke.

Fast forward to today. I planned to measure assemblies in the spare TB Bruce loaned me. I realized I could measure the plunger depth from the bottom of the TB and I could compare the used parts to the actuator samples I had made. I decided to work on it today despite breaking the retaining clip because I questioned whether or not there was any functional reason for the retaining clip. Not only did I question the need I started to think it could break and fall into the intake manifold.

The only other function I can think of is as an assembly aid; keeping the spring on the plunger during assembly. I'm not sure that helps significantly. To assemble I placed the derby in the TB recess; I placed the spring on the derby; I placed the plunger on the spring and then I used the FIV heater to push straight down on the plunger flange. Once I pushed it to the proper depth I turned in CW 90 degrees and allowed it to come back up in the locked position (a locking tab is on the foot of the heater and there is a pocket in the TB which the tab sits in preventing rotation of the FIV heater) .

Based on the correct extended position the clip seems like a risky item. There just isn't a lot of room for error. I don't think I will run out and remove my clip but if I need to take the spring off I think I will remove the clip. My plan for the replacement is to remove the external switch and fragile arm. That's the only thing I can think of which might be at risk with the clip removed but even with the clip present you still need to compress the spring and turn the heating unit 90 degrees against the spring force (so it's still not really protecting the arm).

Unless something changes my mind I will recommend removing the clip if I am successful in creating a replacement. Keeping the clip is too much of an opportunity for a customer complaint for what seems to be a known, and avoidable, failure mode.

Any thoughts?
Scott

bcroe

Just a couple random thoughts here.  I wonder what current/power
at 12V your device will consume?  This is not very critical as the
circuit is large enough to run 2 pumps.  What matters is roughly
the right timing.  I note a couple different parts numbers for the
small and big block engines, though it probably matters little. 

Going backwards the Cosworth used a simple air valve that got
12V to add air, then abruptly closed at 125F coolant.  Just a step,
maybe no worse that dropping off a carb linkage step.  Cad has
an IDLE STOP SOLENOID in the throttle body, wired to add some
throttle air when the AC compressor is engaged.  Probably not
enough, wonder if it could be used like the Cosworth?  Bruce Roe