cold start problem 75 450 SEL
 

Have a 74 450 SEL , electronic fuel injection, that won't start cold.
If I spray starting fluid down the throttle body it starts right away.
When it's hot it starts right away and the engine runs great hot or cold.
Can someone outline briefly the best way to test the starting valve, thermal time switch etc.? is there as start valve relay and if so where is it? Anything else it could be?
Thanks!

Try connecting a voltmeter OR test light to the plug on the cold start injector & operate the starter. UP to 60F there should be a voltage signal for at least 1-2 seconds. WITH a cold motor (30F) the signal should last 10 sec durning starter operation.

THE coolant temp sensor can also cause hard cold starting.
AT 65-70F the resistance should be around 2500ohm.

ALSO have the valves been adjusted lately?? Tight intakes will make the engine hard to start as well.

I would also suggest cleaning the tirgger points for the fuel injection along with the ignition points. Dirt or oil on the ignition points will make for very hard cold starts (do you smell fuel?).

Also inspect for leaking injector lines cold (this means low fuel pressure at the nozzles) along with cold start valve and thermo-time valve.

My 280 starts up instantly if I clean the ingnition point prior to attempting.

Another thing to check is wear in the distributor -- as the bushing at the base wears, the shaft will push off to the passenger side slightly under the pressure of the ignition points. This will prevent old trigger points from opening on the driver's side due to wear on the rubbing block, so you only have four cylinders with fuel, then usually six, and only eight when the dizzy starts to warm up. If you get surging during warmup, for sure this is the case.

New trigger points help, but the real cure is to replace the points with a breakerless system and re-bush the dizzy.

Peter