What is the Correct Length for a Dummy Actuator

[Chipps]

I posted this in the Spider forum with little response, so I will try here. As I said there I now understand the problem historians and legal scholars have when they examine documents to determine original intent. I say this because I installed a rebuilt Spica pump sent by Wes Ingram for a 1973 Spider. Based on the instructions in Wes Ingram’s manual I bottomed the screw under the thermostatic actuator, and then backed it out two turns for the initial setting. At this setting the engine runs, but it is too rich. I then set about adjusting to achieve the 0.019” gap using a dummy actuator set I thought to the correct length. However, after achieving this gap I find the car barely runs. In doing further research I find the following.

You should set the dummy actuator length to either 25 mm to simulate 170 degrees based on section 109 of Wes Ingram’s manual or 27 mm based on the Centerline instructions from their web site or 31 mm as most rebuilt actuators will extend to 31 mm, hot also based on section 109 of Wes Ingram’s manual or the actual length of the actuator after you test it for maximum length based on the instructions sent by Wes Ingram with the rebuilt actuator. However, the 1969 to 1974 pumps require turning the screw clockwise until it bottoms to allow for the longer extension of the newer type actuators as section 109 says as well. So if the 1973 pump requires bottoming the screw, do you just leave it turned all the way in and not bother with any adjustment of the 0.019” gap at all?

[Roadtrip]

The dummy TA for a '73 model pump should be 27mm. In using a dummy TA, the assumption is that the TA meets specs, i.e. that the extension of the TA is 27 mm at 175F. Now, that said, the 27mm extension TAs are no longer available and almost all are the 29mm or 31mm models from the later year cars. That's ok, just put a 2mm/4mm washer-spacer(s) under the TA base to bring the apparent extension back to 27mm. The injection pump will never know the difference and think that it has an original spec TA. Also by using the spacers, cold start performance will improve and cold fast idle restored.

Don't get wrapped up in how many turns of the adjustable screw in the pump body. Just set the pump gap to .019" (long rod disconnected) with the dummy TA set at 27mm. The dummy TA is just a convenient way to quickly set the pump gap rather than using the actual TA and trying to keep the coolant temp at 175F while doing it. Also there is less stress on the fragile piping. In actual operation, as the coolant heats up past 175F and all the way to running temp (about 190F), the TA will continue to extend and probably drive the pump gap (again, long rod disconneted) to zero. That's ok, there is no change in fuel delivery at pump gaps less than .019". Once the pump gap is adjusted correctly with the long rod disconnected, re-connect the long rod and warm the engine up to full running temperature and adjust the long rod to hold the pump gap at .019". The reason we do this is that .019" is where fuel delivery starts to increase and when you step on the pedal you don't want to have to go through a small "dead" zone of fuel delivery.

[Chipps]

Thanks for the advice.

I emailed Mr. Ingram to inquire about the length of the actuators he supplies. However, I think I will just remove it from the car. Then cook it to see what the extension really is.

At first I assumed it should be 27 mm. This is the length I set the dummy actuator to yesterday. Assuming I measured the gap correctly, which I find very hard to measure, at this setting the car is very hard to start, and barely runs.

I still find these various conflicting instructions problematic to say the least.

[Roadtrip]

With the TA installed and the engine cold, is the pump gap fairly wide, like say 1/4" or so? I don't think the instructions are necessarily conflicting, but rather different ways to get to the same end. Does the engine run better as it heats up to running temp?

[Chipps]

I don't recall on either diminsion as I tried so many different combinations. I will revisit this tomorrow.

Mr. Ingram answered that the actuator he sent measures 31 mm, so I will start with that.

[lowmileage]

Wes told me to stick it. Stick a spark plug washer under the pump end cause his go to 31mm. He said that would be the right size. Mine will arrive back home tomorrow rebuilt.

[Roadtrip]

A couple of ordinary thickness washers add up to about 4mm. I don't know how thick a sparkplug washer is.

[lowmileage]

Actually, I was kinda suprised he said "a" spark plug washer. I tend to believe that won't be enough but then again, he did say to also bottom out the TA adjusting screw in the pump. Mine is 2 turns out so I guess I'm going to pick up a mm or so there.

[Chipps]

As I am working on this as these messages go back and forth, what do you mean by bottom it out? Do you mean begin with it bottomed out or forget the .019" gap and just leave it bottomed out? I ask this as I began with the screw all the way at the bottom, and the TA removed from the pump. In this setup the car starts and runs great.

Next I adjusted to achieve the .019" gap. I now have that gap with the screw brought back up 1.5 turns. At this setting the car runs like crap. The idle is erratic, with occasional gentle backfires.

Proceeding on I have just finished the butterfly plate adjustment procedure. All this leaves is the mixture adjustment at 2500 rpm.

[lowmileage]

My screw happened to be turned up 2 turns at the start. My TA performed satisfactorily until the end of last year so I don't know if the 2 turns was for an in-spec unit. My TA bulb was crimped so the mechanic that crimped it, might have also turned the screw up to add to the extension. I do (as I retrieve my Spica notes) believe that the first thing to do is set up a dummy TA and adjust the screw under the TA to achieve a .019 gap. Remember now all, we're not talking about adjusting the screw that is wire protected with the plastic cap because we all know that screw shouldn't be touched. Well, you can touch it but don't adjust it.

[Chipps]

Thanks for the update. At this stage the car will not run at idle. Playing with the throttle it will run poorly, while backfiring slightly, below 2500 rpm. Above 2500 rpm it settles out somewhat.

I believe I will go back to the screw all the way bottomed, and forget the 0.019" gap business as this car does not seem to like that setting. Which leaves the question as to whether to just remove the thermostatic actuator from the car entirely.

[lowmileage]

With the screw bottomed, what is your fast (cold) idle rpm and what is the hot idle rpm.

[Chipps]

Cold idle is about 1100 and very smooth. Fast idle is about 800 and just a little choppy, but not much.

I am just back in from attempting to set the mixture. This will not happen with the present 1.5 turns out setting, which yields the 0.019" gap, as the car will start, but not idle at all. Unless I sit in the driver's seat and hold the peddle, the car will not run.

The only non running adjustment I can see that can be made is the de-cel mixture adjustment that is supposed to be done at 2500 rpm. It appears there is a considerable range in this adjustment, so this may not be be an option as I do not know where to set it to begin this process with the engine not running.

[lowmileage]

Quote:

Originally Posted by Chipps Cold idle is about 1100 and very smooth. Fast idle is about 800 and just a little choppy, but not much. I am just back in from attempting to set the mixture. This will not happen with the present 1.5 turns out setting, which yields the 0.019" gap, as the car will start, but not idle at all. Unless I sit in the driver's seat and hold the peddle, the car will not run. The only non running adjustment I can see that can be made is the de-cel mixture adjustment that is supposed to be done at 2500 rpm. It appears there is a considerable range in this adjustment, so this may not be be an option as I do not know where to set it to begin this process with the engine not running.

[Chipps]

No, this is a rebuilt unit from Wes Ingram as is the thermostatic actuator. Here is what he said about the adjustment procedure in an email message on Sunday when I asked about the length of the actuator he sent me.

"31 mm at 180 degrees, but all that matters is that you set the gap for .019 and not zero, with the long rod disconnected and the engine fully up to temp. Do not use a dummy TA. See pg 33.

It may take up to 3 attempts removing the TA from the pump to change the screw in the pump. Leave the mid clamp screws off until you get it right. Be sure to adjust the long rod (engine still hot) such that it does not change the gap. Avoid other written material about the setup."

I have done what he refers to in the quote above, with the reported results. It seems to me one of three things is occurring.

1. I am an idiot. This setup and tuning procedure is beyond my skill level.

2. The mixture adjustment on the pump needs to be set somewhere or the other while the engine is still off for it to run properly once started.

3. The pump I received has a problem of some sort or the other.