MFI thermostat questions

Mr Beau · 08-16-2003, 10:51 AM

I've been playing with the thermostat system on my 911 for a while, and eventually I removed all the guts. I threaded the cap, and have installed a bolt that I can use to move the rod in and out to adjust the mixture.

Can someone confirm the position of this rod when the car is fully warmed up? Is it all the way in? One way to verify this is by opening the access port on the top, and pressing down on the "other" rod in the pump. I want to eliminate the thermostat's influence in the system while I make some of the other adjustments.

Also, can someone confirm the number of discs that should be in the system? I've seen the exploded diagrams showing the order, but not the quantity.

Thanks!

Matt
'73 911E

Paul Thomas · 08-16-2003, 11:45 AM

As the thermostat heats up, its pulls the rod out enrichening the pump. Did you consider making a small plate to go in place of the thermostat with a bolt for adjustment? Thats what i did and it works well.

Paul

Mr Beau · 08-16-2003, 01:34 PM

Paul,

That's essentially what I've done, but I'd like to set my temporary kludge to where it will be with the thermostat once it's hooked-up and working properly (holes in the HE are one of the problems right now).

And doesn't the thermostat push the rod in as it warms up?

Thanks,
Matt

Tyson Schmidt · 08-16-2003, 02:27 PM

Yes, the thermostat expands, and the rod pushes in on the plunger. Once it's pushed all the way in, it's done. So I guess that means you need to tighten the bolt until it stops, and it will be at the full warm position.

Mr Beau · 08-17-2003, 07:30 AM

Anyone know how many disc set are in the thermostat?

Also, has anyone used this choke adapter from Supertec, or fabbed one of their own?

Thanks again.

JSDSKI · 08-17-2003, 08:33 AM

I thought the number of discs were set at the factory and were different for each car/pump/thottle body combination. The number of discs and their postion were dependent upon the settings for the whole system.

When I asked about cleaning out the thermostat in my pump - the MFI pro's on Pelican made sure that I used a diagram to return the discs to the exact same position.

See if there is a procedure in the "Check, Measure, Adjust" MFI manual in the tech section of this forum.

304065 · 08-17-2003, 06:07 PM

From the articles page so you don't have to look it up. . .

First, check that your thermostat is working correctly:

Start motor and warm to operating temperature (180°C).

On the MFI housing behind the thermostat is a small triangular cover plate.

Remove this inspection plate and observe if the thermostat rod is pushing against the cam-shaped lever. This lever should not be able to move back further. (Use a small angled screw driver or similar to gently check the there is no movement). If there is, continue as below.

If you need to clean out the thermostat I would do it this way:

To remove the bottom screw on the thermostat cap, grab your air cleaner with your fingers while placing your thumb on the thermostat cap, remove top screw (cap is spring loaded).

Remove cap, set aside, (don't lose cap gasket, mine was broken so I made another

one — this thing will not work without the gasket, it's also a spacer).

Draw out the rod with elements — I would not take them off if it works!!

(There are 25 pairs of expansion elements (mounted like cymbals) fitted first, followed by three slightly larger flat washers).

Clean with carby spray cleaner, set safely aside.

Remove bottom screw on thermostat housing (kind of hard to get at), hold on to housing,

remove top screw, remove housing.

You should have a cross shaped gasket with a hole in the middle, and a metal spacer.

Should also have a small rubber "o" ring type gasket in the flange on injection pump.

Clean them up using parts cleaner or carby cleaner.

Next, hold thermostat housing, install rod with elements, spring seat, spring, and compress cap with your thumb, install screws.

Check for movement on thermostat rod...about 3/16" (4.75mm) or so..

Now reinstall thermostat.

The reason for installing the whole thing assembled is, if you install just the housing, and then the rod with elements, it gets warped and doesn't move right.

http://www.pelicanparts.com/techarticles/911_MFI/TipMFI.htm#MFI%20thermostat%20R%20&%20R

ed martin · 06-28-2004, 11:16 PM

Well there's the answer right there, in the Pelican tech articles under MFI/thermostat. Just as John said, lifting directly from the text, 25 pairs of discs and three washer spacers. I remember referring to this article and the whole MFI text years ago. I still don't remember that extra washer, or is it a spacer? But I would trust the veracity of this text over that of my memory.