Permanent cold start.

[stickandrudderman]

I often say I'm in the 42nd year of my apprenticeship....
We had a customer's car in for rough running/cutting out/black smoke. Cold start was excellent.
A quick listen at the injection pump revealed constant suction at the auxillary air filter even when the engine was up to running temperature and removal of the auxillary air filter confirmed it.
https://youtu.be/TrsMgUlEUaU
We assumed, as is normally the case, that either the waxstat was defective or the piston seized but dissassembly revealed a perfectly working WRD.
We re-assembled and after some head scratching realised that the stat was not actually getting warm even though coolant temp was rising to normal.
Who can guess what we found next?

[Mike Hughes]

Collapsed/pinched coolant hose in the WRD circuit?

[mda]

low coolant level

[rwmastel]

What is a "waxstat"?  Is it thermostat?  Is there actually wax inside of it?

https://www.sl113.org/forums/uploaded/ja17/200662802329_20046281523_InjPumpWarmUpDeviceParts_1.jpg

I searched the forums for "waxstat" and it has only been mentioned 3 times in 20 years, all by UK based members.

"The Internet":  Why yes, Rodd, there is wax inside.  See here:  https://en.wikipedia.org/wiki/Wax_thermostatic_element

Back to the trivia contest, does it matter if the in/out hoses are reversed?  Blocked water path and insufficient water seem the most likely, but in the interest of giving a different answer, I'll say the hoses were swapped.

[Bshaunessy]

STICKANDRUDDERMAN:
  Ok….don’t leave us hanging.  My guess is …….I don’t know?

[WRe]

No, less, blocked coolant, mayonnaise, ...
...WRe

[stickandrudderman]

Some cars have throttle bodies that have coolant running through them; presumably to prevent icing in colder climates.
The coolant channel in this throttle body had become blocked so preventing the passage of warmed coolant reaching the WRD. Et voila!; permanenet cold start!
https://youtu.be/W_kbWAmeH7w
I am a little embarrassed at how long it took me to realise that although coolant temp was being reached, the WRD was not getting hot.

[Mike Hughes]

So I was on the right track.  That blockage must have taken a while to find!  How difficult was it to clear the blockage?

[Kevkeller]

Good info to know.  Thanks.

[wwheeler]

On my W111, you have to be careful to burp the air out of the WRD so coolant will flow. If not, the thermostat is sensing air, not coolant. The same thing happens that the engine warms up but runs incredibly rich. I now just remove the hose going to the WRD and burp the air. No more problems.

[Bshaunessy]

OK WRD experts ( or at least folks who understand how the WTD works):
  Does WRD introduce additional warm air into bottom of CSV ( and therefore into intake plenum) OR does WRD inteoduce a mix of fuel and air into CSV?   Description of process in TECH MANUAL is a bit unclear, as it says WRD allows extra "air and fuel" during warm up phase, and addresses extra air via a tubing line to the CSV but doesn’t clarify how the fuel gets added?

[wwheeler]

When an engine is cold, it needs a larger amount of air and fuel to run at an acceptable idle speed. It also needs a richer mixture at first which slowly leans out as the engine warms.  The WRD adjusts the injection pump so it injects more fuel per squirt (richer). But you also need more air with that fuel. The WRD also has an air valve that lets in additional air in through the small IP air filter and then into the intake manifold. This happens at the same time and is tuned to do so.

The air gong into the manifold is at the same location as the CSV but thy are not really related. Two different functions. The WRD is akin to a choke on a carbureted engine and the CSV is like the small pump on a carburetor that injects fuel into the manifold before or during starting.

[Bshaunessy]

WWHEELER
  Thx for clarification:
 I think I understand now:( During start and warm up):  WRD introduces more FUEL via  the normal injection system .  WRD also introduces more ( warm) air via tube from FIP  to bottom of CSV.
  As I’ve never had my fuel injection pump apart ( and hope to never have to!) I mistakenly assumed the extra FUEL referred to in the WRD descriptions was also introduced from the FIP via the air tube from the FIP to the CSV.
  Slowly, the pieces of this sophisticated ( for the era) fuel system are falling in place……pretty much one device at a time!   A slow process but necessary to troubleshoot fuel issues.

[wwheeler]

It is a complicated system. One of the hardest concepts I had to understand is that you have to treat the travel of the air and the travel fuel to the combustion chamber differently. In this system, they are separate until the intake valve. In most carbureted systems, they are mixed in the carburetor and all adjustments are done there.

Another difficult concept is idle adjustment. Idle in a carbureted system is done by a screw on the carb throttle plate. In the MFI system, it is done by adjusting the amount of fuel on the injection pump knob and then adjusting the air with the air valve on the manifold. Both systems do the same thing and that is to change the amount of air and fuel getting to combustion chamber to change the idle speed. But they do it in very different ways.   

[georgem]

What I think is remarkable is that this level of sophistication was done mechanically whereas now days a computer would control the lot PLUS PLUS PLUS