1974 Euro Carrera MFI cold start problems

[JTH 36]

Hello Everyone,

I am having problems starting my 74 Euro Carrera. It ran fine before the holidays but I began to notice difficulty in cold starting it a couple of weeks ago, but once started and warmed up and then shut off it would start and run great. I went away on business for a couple of weeks and just returned and now the car will turn over but not start or fire.

It is the original stock 2.7 MFI motor. I’m wondering if it is something with the cold start.

Any recommendations would be greatly appreciated.

Thanks
Jeff

[Grady Clay]

Jeff,

Since this seems to have ‘crept up’ and not suddenly happened, I would suspect the thermostat. The combination of dirty thermostat and/or leaking hot air hoses and decreasing winter temperatures conspire to finally not let the engine start. What is the condition (rust) of the left heat exchanger? Is the large rubber hose from the heat exchanger to the left tin in good internal condition? Are the two concentric hot-air hoses in good (like new) condition?

The thermostat function can be checked using a hot air gun (high power hair dryer) to see if it turns off.

The above issues usually prevent the cold running thermostat from turning off and causes poor running during and after warm-up, not problems with cold start. However a very dirty thermostat can stick and not operate when cold.

That said, it indeed can be the cold start system. That is easy to check. With the engine overnight cold (don’t try and start), remove the small cold start hose from the cold start solenoid valve on top of the fuel filter console at the connection behind the #3 intake stack. Put the hose in a suitable container.

Crank the engine. Fuel should flow for a while during cranking and then stop. If you immediately continue cranking, no fuel should flow. If you wait a while (15 minutes when cold) and again crank the engine, fuel should flow for a while and again stop. If the temperature isn’t cold enough, the fuel will not flow when cranking. No fuel should drip when not cranking. The fuel flow should abruptly start and stop – no dripping. This is normal operation.

The cold start system is actually relatively simple. Cold start system problems can be; wiring or issues with the Thermo-Time Switch located in the crankcase breather plate, Cold Start Solenoid Valve and associated hoses and nozzles and the Cold Start Relay and associated wiring and connectors. The two fast-on connectors at the Thermo-Time Switch are different sizes but it is possible to still force them on incorrectly. Be careful.

During this procedure, you are dealing with gasoline liquid and gasoline/air fumes. These are the most dangerous substances you normally ever come in contact with, unless you are into explosives or nuclear weapons. Please be EXTREEMLY careful. The life & 911 you save may be your own.

Best,
Grady

[kwikt 911]

Check your cold start valve on top of the fuel filter housing. Maybe the wire got dissconnected or no power to it. Then check the cold start feed lines going to the throttle stacks to make sure they are passing fuel while the engine is cold. Then check the temp sensor on the block under the air box. It has 2 wires going to it which controlls the cold start valve. I personally have my cold start dissconnected and lines plugged. I do pump the gas peddle a few times when the engine is cold and no problem starting. Hope this helps!

Kevin

[kwikt 911]

Dam Grady!!! You beat me to the post

Kevin

[Grady Clay]

Kevin,

Does 'fast on track' and 'fast posting' go hand-in-hand?

‘Pumping’ the gas with MFI does nothing for cold start. I suppose it is good to check for free throttle operation. It is important to have the ‘best’ throttle opening while cranking. The cold start system puts raw fuel into the intakes. For the engine to fire and not ‘flood’, there also needs to be additional air. This is part of the reason for the hand throttle. Part of successful cold starting is also not too much throttle opening. The intake atmosphere depression helps vaporize the liquid gas. So does the compression heating in the combustion chamber (high compression engines start easier cold).

If your MFI starts cold without the cold start system operating, I suspect the engine is too rich. That may be the main setting but it can also be the thermostat is set richer than normal.

A MFI engine ideally needs to have mixture help while cranking. Once the engine has fired and you ‘rap’ it to clear excess starting fuel, the cold running thermostat is the primary determiner of the mixture (still affected by main mixture setting). There are two aspects of the cold running thermostat: how rich it makes the engine and how fast it turns off. The mixture enrichment is determined using shims inside the thermostat. The speed of turn-off is determined by the load put on the engine and the condition of the right heat exchanger, rubber air hose, the concentric paper/aluminum/plastic air hoses and the cleanliness and setting of the thermostat.

The quantity of cold start fuel is built into the system and is temperature sensitive (unless you re-wire it for a manual momentary electric switch). It is determined by the Thermo-Time Switch in the crankcase breather cover. It is sensitive to both temperature and the length of time cranking.

I like a system that fires and runs on the first few rotations of the engine. I also like to tolerate slightly ‘too-lean’ running during warm-up as determined by the cold running thermostat. The initial ‘rap’ of the engine, the lean thermostat, turning the thermostat off soon and appropriate load on the engine helps prevent diluting the oil with gasoline – very bad for the engine.


Jeff, if you find no (or little) fuel from the Cold Start Solenoid Valve, we can help you trouble-shoot the issues.

As an aside, this is a good illustration as why regular and complete CMAs should be part of normal maintenance routine. This starting problem can also be due to a combination of issues finally conspiring to not let the engine start.

Best,
Grady