Re: cold engine acceleration problems (REALLY LONG!)

["Robert Rooney" <dmcvegas@xxxx>]

--- In dmcnews@xxxxxxxxxxx, "Walter" <Whalt@xxxx> wrote:
> I need some help figuring out my engine problems:
> 
> The symptom is that while my engine is cold or warm (but not yet 
fully
> warm), it idles okay, but any attempt at acceleration is counter-
productive.
> The engine coughs and sputters instead of increasing the RPMs. 
This doesn't
> happen every time I start the car from cold, but it happens often 
enough to
> be very annoying. I am wondering if this could be due to a bad 
warm-up
> regulator (a/k/a control pressure regulator). I paid a local 
mechanic $750
> to replace this part a few months ago. It was $500 for the 
regulator and
> $250 for the labor.
> 
> Question 1: Are these symptoms indicative of a bad regulator?

Depends. How is the acceleration after the engine warms up? I had the 
same problem, but after the engine warmed up it hesitated on it's 
exceleration. This was caused by the LAMBDA being unplugged. Check to 
make sure the frequency valve is buzzing.


> Question 2: Did my local mechanic rip me off for replacing this 
>regulator before?

Hard to say. What method did he use to conclude that the control 
pressure regulator was bad? If you are content with the work he did 
it is worth it, but I think that the prices he charged are very 
steep. The CPR thru DMC Houston is only $357.50, and is something you 
could swap out in around 30 minutes or so. Not difficult at all, you 
don't even have to remove the air box. Ask for the old part back.


> Question 3: If the problem is the regulator, is it possible to take 
>it apart and fix it? i.e., could it be clogging up with fuel system 
>crud?

Yes on both counts! A clogged control pressure regulator could 
defintely cause these type of symptoms. The cleaning procedure is a 
snap! Details and instructions are located in the Technical Library 
section of the DMC News web site. Just make sure if you do this 
procedure yourself that you use new seals on the fuel line. However 
it should be noted that if the diaphram inside the CPR has gone bad, 
it unit will then need to be replaced. But if your's is new this 
shouldn't be a factor.


> Also, I got busy reading the service manual and figured that maybe 
my
> problem was in the cold start circuit. So I checked the thermo-
time switch
> (a/k/a temperature switch). I found that it is permanently stuck 
in the
> cold position no matter how warm the engine gets.
> 
> Question 4: Since the cold start circuit is only active while the 
starter is
> engaged and failure of the thermo-time switch could cause flooding, 
is my
> problem a flooded engine?

If the thermotime switch is defective where it constantly activates 
the cold start valve, then you should replace it beyond a doubt! 
However this would probably cause the engine to run fine while 
warming up, but stall a bit when finally warm. After the engine heats 
up, unplug the switch to see if that makes a difference on how the 
motor runs.
However, activation of the cold start circuit is controled by the 
thermo time switch, NOT the start position. The hot start relay is 
what is activated by the start position. The hot start relay should 
NOT be a factor here anyway. Like I said, check to make sure that the 
LAMBDA system is operational.


> Question 5: Could flooding of my engine cause it to not accelerate 
>well until the engine is warmed up? Or is the warm-up problem 
>caused by something other than a stuck thermo-time switch?

Lack of fuel would cause the engine not to accelerate properly untill 
the engine has warmed up. This would show a symptom of the cold start 
circuit not working at all rather then all the time.


> Question 6: If 12 volts from the starter circuit is applied to the 
>heater in the thermo-time switch, how long will it take for it to 
>open the circuit?
> What I want to know is if these switches are meant to open-circuit 
>before the starter disengages. Or does it take continued starting 
>attempts to heat this switch enough to open the circuit to prevent 
>flooding?

I don't know off hand how long it takes for the heaters in both the 
control pressure regulator and the thermotime switch, though I think 
they may be mentioned in the workshop manual.
Both of these heaters will recieve power as soon as the key is in 
the "ON" position, or maybe it's when the RPM relay is tripped, can't 
remember... Repeated starting attempts should never be nessisary, the 
engnie should turn over immediatly. The starter has no impact of the 
function of the cold start circuit.


> Question 7: Where is the best place to buy a new thermo-time 
>switch? Do I get it locally, or should I buy it online? How much 
>should I pay, and what part cross-reference should I ask for?

Just buy it through DMC Houston. Not only are there no worries about 
compatability, but DMC Houston is ALOT cheaper! DMC charges $24.65 
for the thermotime switch. I called a BOSCH supplier in my area and 
they wanted $49.00. A Volvo dealership wanted $160!


> Also, while I was diagnosing the above problems, I noticed that my 
>radiator fan thermostat (a/k/a cooling fan switch) is dripping 
>coolant. And it also sounds like it is out of range.

How do you mean that it sounds out of range? If the switch is 
defective in turning the fans on, then it will need replacement. But 
since it has a leak it could be allowing air into the system causing 
a overheating problem. It may not be a defective otterstat (switch) 
after all.

> Question 8: See question 7 only now I'm looking for a different 
>switch.

Don't know of any compatible cross-over part for the otterstat.


> Question 9: Instead of replacing this switch with the same thing 
>that can leak, would it be better to plug this bad-engineering 
>fiasco and replace it with a surface mounted thermostat instead? 
>And if so, how, who and what is involved?

If you replace the switch you will also need to replace the rubber 
seal that goes in around it. But there is an alternative... No matter 
which style of coolant piping you have (on top or below the pipe), 
the otterstat is held into place by a simple clip. As DMC Joe 
reccomended to me, bailing wire can be used a a temporary 
replacement, but isn't really a fix. The solution: Home Depot sells a 
stainless steel hose clamp which is thin enough to fit between the 
electrical contacts on the otterstat, yet also long enough to wrap 
around the entire pipe. Installed it onto my car, haven't leaked a 
drop since!
I think that someone recently posted about having external-mounted 
otterstats to control the fans. I'd like to know more since they have 
different temps to switch the fans on and off. Even so, the self 
bleeding kit from DMC Joe would be a good investment here that you 
should probably keep at the top of your list to buy next.
> Good luck answering these!
> 
> Walt Tampa, FL

Hope this help a bit. Many thanks to DMC Joe for all the help he has 
given me which was also a source for this posting.

-Robert
vin 6585