Engine suddenly stops
 

I found a problem, after using the car for a long time (30-60min) at high speed (high temperature at the engine), it runs more or less good. But when i came from the highway to the city, if i stop at a traffic light, or another stop i need to do, the engine dies.

If i wait some time (10 min) i can start the car again without problem and it keeps on. But if i go again to high speed and return, it will die at any stop i do.

I don't know what is going on here, but it's very bad this because i can't use the car in the city, because i am afraid it stops anywhere.

Thanks!!

ariel

If this was a water cooled car I'd say it was a problem with the cooling like a partialy blocked radiator.

It really sounds like something is overheating. When the car is moving fast the airflow is enough to keep the part cool enough to function but when you are stopped the part overheats. Then it cools and is able to function again.

Will the engine still crank but not fire when this happens? Is Buenos Aires still very warm this time of year?


Perhaps the ignition coil is starting to fail? An oil thermostat stuck closed so the oil is overheating?

Need more details .

Check the mixture as a first step. Believe it or not, my 959 had this problem, and I tested a whole bunch of stuff thinking it was a bad component. Then Grant at Callas Rennsport suggested I go back to basics, and start by checking the mixture. It was way off...

-Wayne

I tried to check the mixture but apparently the mfi pump is not responding, i don't know if it's stuck or something like that.

Is it possible to open the pump and check it? or once opend never close again?

my mechanic told me that apparently the rubber pieces inside or the gaskets are bad, so i need to rectificate all the MFI pump.. :( are there spare parts to repair it or no more solution?

When my was dying intermittently like that, I traced it to the "green wire from hell" It was brittle causing the connection to be intermittent. It would shut off and then start after about 10 min or so after cooling. Then shut off again.. etc.

If i try to start the car, usualy it won't start. It cranks, but there is no fire, as you say. With my little knowledge in mechaic i usually think like it wont start because the car is receiveing too much fuel and i have to wait some time to let that fuel go and then it start ok.


Blanco, can you explain a bit more. I am not too familiar with it. What's the green wire?

Also today the car was failing a little bit, and i dissconect the wire behind the oil temp gauge and it stopped failing. Does this tell anything?

thanks

bump

i am stuck still here.. :(

You don't have a permatune CDI do you?

The green wire he's talking about comes off of the distributer, and is famous for needing replacement.

Babak

P.S. CDI is the box that sends a signal to your coil, which goes into the distributor.

There is nothing in a '73 MFI motor that would act as a safety kill switch on the fuel or ignition because of oil temps.

Like Wayne, I believe this to be fuel, or at least mixture related. A few questions:

1) What RPM does the car idle at when "cold". How about when "warm", but not "hot"?
2) When it dies, does it stumble for a bit and then die, or does it just die abruptly?
3) What condition is the air filter in?
4) What is the ignition timing set at?
5) What kind of electric fuel pump is fitted, and where is it located?
6) Is there a thermostat fitted on your MFI pump?
7) Can you post a picture of your motor?

Let's start with these. Also, I would NOT start randomly trying to adjust the mixture setting on your MFI pump. You do not have a baseline, and it is VERY easy to get that out of whack to a point where you will make your situation worse if you do not approach this systematically.

JA

My mechaic changed mi CDI to one of national production (made in argentina) it says something like NOZ or something like that on it. Myabe i can check if it's right if i have the specifications of the one that goes right to the model or buy another one here...

Jandrews:

1) When it's cold it idle at about 800/900 RPM
2) it dies abruptly.
3) Air filter is new, K&N just installed.
4) My mechaic apparently set it to the specifications at the CMA, but if you tell me how i can recheck it.
5) The electric fuel pump as far as i know is the original one, instaled behind the front left headlight at the fender.
6) I don't know how to determine it, maybe as soon as i can get the picture of it.
7) I will take some pictures this week and post them.

Thanks for all this help guys, it's very hard to find solution to this problems here in buenos aires!

You might read through this thread. This guy had a similar problem to yours:

http://forums.pelicanparts.com/porsche-911-technical-forum/386494-mfi-pump-adjustment-idle-problems.html?highlight=mfi+idle

Also, I am going to STRONGLY suggest you go through CMA in detail! I know you just want a quick fix, but CMA is the only rational way to go about diagnosing these systems. One element of CMA is ignition timing, and it is essential. You will need a timing light to check this, so if you don't have one, see if you can borrow one. They are common, and many people with marginal mechanical skills own one.

Here is the link to CMA - this is a must read - period!

http://www.scatliff.mb.ca/pelican/MFI_Check_Measure_Adjust.pdf

Regarding the electric fuel pump, please post a picture of pump and mounting location when you can, as well as a picture of motor.

Lastly, does your car have a hand throttle located between the front seats?

JA

i will do the CMA as it should this weekend i think.

I do have the hand throttle but the plastic piece has dissapear so i have to buy a new one.

By the way, i can borrow the timing light but i don't know how to do it i mean all the terms and where to check them. I tried to search in the forum but there is no explanation of that.

as soon as i can i will post pictures of the engine...

thanks!

ok, i have bought a new timing light so ready to start with CMA but have some questions.

Where should i plug the timign light and also, how can i check the dwell angle and then where is the TDC that i need to go throught timing.

Also i have the unysin, can someone explain how can i use it because i don't have a synchrometer which seems to be a lot easier :(

A i say.. i am a newbie but with all the brain open to learn all i need for this :)

Jandrews, here are the pics:

First the car (after a classic race):
http://forums.pelicanparts.com/uploa...1207925071.jpg

This is the engine:
http://forums.pelicanparts.com/uploa...1207925098.jpg

This is the CDI i have. This one is national and universal type. 12v with earth. it has platinum ("platino" in spanish):
http://forums.pelicanparts.com/uploa...1207925274.jpg

Here is the electric part. What are those 2 plugs not connected?:
http://forums.pelicanparts.com/uploa...1207925296.jpg

What is this cable?
http://forums.pelicanparts.com/uploa...1207925357.jpg

MFI pump:
http://forums.pelicanparts.com/uploa...1207925389.jpg

Engine without air filter:
http://forums.pelicanparts.com/uploa...1207925425.jpg

And as was opening i found this big problem, FUEL in the throttle boddies, and it reached the air filter:
http://forums.pelicanparts.com/uploa...1207925474.jpg

If more pics needed please tell me.

thanks!!!

This is the fuel filter:
http://forums.pelicanparts.com/uploa...1207966858.jpg

These are pictures from the oil - air filter hoses:

Hose from air-filter to oil tank:
http://forums.pelicanparts.com/uploa...1208034705.jpg

Hose from air-filter to engine?:
http://forums.pelicanparts.com/uploa...1208034750.jpg

Hoses coming to oil tank:
http://forums.pelicanparts.com/uploa...1208034806.jpg

I found this under the left fender:

http://forums.pelicanparts.com/uploa...1208034846.jpg

It sounds like to me that your oil is diluted with fuel and is overflowing into your air filter housing. You need to find the cause of the oil dilution (over-rich) likely, and stop it immediately. Serious dilution of your oil with fuel (if that is your situation) will cause damage to bearing surfaces in your engine that require lubrication.