DDK - Die Deutschen Klassiker

Hello again all!
My car is very difficult to start when cold, I think because the Cold Start function through the air box isn’t working.
What are people doing for cold starts on their MFI engines?
Are you…
a) Using the factory system
b) Using a manual switch to activate the solenoid
c) Using some other system
d) Not using the cold start system at all
If your not using the cold start system at all, what is your process for getting the car started?
I would prefer to not have to use the system at all so that I can run individual air filters on top of the stacks but I cant do this if I cant reliably get the engine to start from cold.

I use the factory system. On our 69/70/71 cars the cold start fuel gets fired in from two brass rails in the air box.

Make sure all the hoses and rails are secure and no leaks. I have found the solenoid ontop of the fuel filter housing can stick if not used for a while. You can test this by just putting a live feed onto the electrical connector on the solenoid. This is usually enough to get it operational again. (make sure no fuel is around when applying the electrical feed for obvious reasons.)

The solenoid is activated only when you crank the engine and the thermal switch is made (Normally closed). The thermal switch is located onto of the engine breather cap. Its basically a bimetallic switch, so when the engine is hot the bimetallic switch opens so when you crank the warm engine the solenoid is not activated.

I find that the factory system is fine as long as all the systems work properly. You obviously need to be mindful of cracking a cold engine too long as you will be pumping neat fuel via the cold start brass air box fuel rails, this is what causes unwanted fires.

If your engine starts on the button when warm there should be no issues with re-commissioning the cold start solenoid. If hot starting is an issue and you need to crank alot then I would fix this before recommissioning the cold start system.

Also the MFI pump has bimetallic disc's in the cold start enrichment device. These discs need to be clean, the hose feeding air to the system needs to be in good nick, (there should be two hoses, one inside the other) when the engine is hot you need to check the MFI enrichment device has leaned off the rack. You can test this by removing the small triangular cover on the MFI pump and with a screwdriver prove the rack has been pushed fully closed.

My CS solenoid was always connected (but it hasn't been on the road for a few years). It was always a pain to start when not used very often and I always took it for granted.

There is a school of thought that says you only need the CS in really cold climates like Canada and Scandinavia.

I recently started mine up, after it sat without starting for about 5 years (see my thread), without CS connected to avoid flooding issues, but it was much warmer than currently. You probably already know, but if not its easy to check to see if the CS solenoid is working - just pull the wee pipe that goes to the TB and pop it in a jar or bottle - if the engine is stone cold, it will pi** out. Do the same when the engine is warm and there should be nothing.

Good luck!

b)
No squirting fuel down the intakes, so I am not using the solenoid on top of the filter unit.

Manual switch to operate the solenoid on the MFI pump, on the '69 car. All very lovely and neat, using an original rear wiper switch.
Manual cable to operate the cold start adjustor on the MFI pump on the '70 car.

No starting problems with either. You don't need the squirt in our climate, in my opinion.

Factory on mine and starts without fail in about 2 rotations of the engine .. 2.4 cold start is direct into stacks though

The '69 MFI pump is unique as it has 2 solenoids. Is your car fitted with a slow action relay (part no. 90161711500) and if so, have you tested it to see if it's working?

IanM wrote:The '69 MFI pump is unique as it has 2 solenoids. Is your car fitted with a slow action relay (part no. 90161711500) and if so, have you tested it to see if it's working?

Hi Ian. I do have one of those but I dont know if it works. I was thinking of testing the solenoid in the fuel filter first and working back from there. How do you test this relay? I'm not certain on the 69 cold start circuit. It is unique and seemingly complicated... Im not sure what the extra solenoid on the mfi pump does either.

Neil, here's my 69 S advice...
The two solenoids on the MFI pump are:
1) (Same as all MFI) fuel shut off on overrun
2) (Unique to '69) cold start enrichment
As I mention above, on my car I operate the cold start enrichment manually from a (rear wiper) switch on the dash.
Originally the system for the cold start enrichment was fairly complex. It's some kind of a temperature time switch and relay, which takes into account engine temperature and (if I remember correctly) cranking time.

My advice would be
For now, forget the solenoid on the fuel filter. The car will start fine without it.
Identify the cold start enrichment solenoid on the MFI pump. Apply 12v to it. Does it click? If so it works, good.
Now apply 12V to the solenoid again, and start the engine. Easier? If so, the temperature time switch arrangement isn't working but the enrichment is.
After that your choice - faff about with the temp time switch to get it working, or do what I did...

As an aside, when I first had mine none of the enrichment schemes were connected. It will start like that, but you need to crank it for quite a while on full throttle (to get some fuel in there), wait a short time, then crank on light-ish throttle. Much easier with the solenoid working....

inaglasshouse wrote:Neil, here's my 69 S advice...
The two solenoids on the MFI pump are:
1) (Same as all MFI) fuel shut off on overrun
2) (Unique to '69) cold start enrichment
As I mention above, on my car I operate the cold start enrichment manually from a (rear wiper) switch on the dash.
Originally the system for the cold start enrichment was fairly complex. It's some kind of a temperature time switch and relay, which takes into account engine temperature and (if I remember correctly) cranking time.

My advice would be
For now, forget the solenoid on the fuel filter. The car will start fine without it.
Identify the cold start enrichment solenoid on the MFI pump. Apply 12v to it. Does it click? If so it works, good.
Now apply 12V to the solenoid again, and start the engine. Easier? If so, the temperature time switch arrangement isn't working but the enrichment is.
After that your choice - faff about with the temp time switch to get it working, or do what I did...

As an aside, when I first had mine none of the enrichment schemes were connected. It will start like that, but you need to crank it for quite a while on full throttle (to get some fuel in there), wait a short time, then crank on light-ish throttle. Much easier with the solenoid working....

Ok so this is clearer for me now. I assume they decided the cold start enrichment solenoid was not necessary and dropped it in 1970? or was it somehow replaced with something else?

I just went out to the garage, I tested both the solenoids as not sure which is which (wire colours don't match my wiring diagram). Both of them clicked so must work. I know the fuel shut of works as my engine does the MFI rev cycling.

I also tested the solenoid on top of the fuel filter, this does work also, I blipped it with the ignition on and fuel came out. But for some reason obviously this isnt actuating when I try and start the car, so there is a problem somewhere either with the time relay (is this a known failure point?) or a temp switch on the engine breather or somewhere else.

I think I will take your advice, if it starts OK with the enrichment solenoid being manually activated I will run this and go to individual air filters.

This Happened to my 71 S and as I already had a hole in the dash, put a push button in to activate the cold start injection of fuel.
Worked a treat, two pushes of the button and fired up every time.
I think if I had the problem now though I would try and get it to work as it should.
But I suppose it depends on where the problem lies. If its in the loom then putting in an over ride is the easy option.

Karl

hashman wrote:This Happened to my 71 S and as I already had a hole in the dash, put a push button in to activate the cold start injection of fuel.
Worked a treat, two pushes of the button and fired up every time.
I think if I had the problem now though I would try and get it to work as it should.
But I suppose it depends on where the problem lies. If its in the loom then putting in an over ride is the easy option.

Karl

Hi Karl,
Can you show us a photo of the fuse box on the engine bay?!
Since the push button is an extra, I believe you should start to work out from there.

Best,
Den

Enviado do meu ANE-LX1 através do Tapatalk

I would love to post a picture but I sold that car about 18 years ago!

Karl