Detroit won't start when cold????

some engines are more cold blooded then others
detriots are the usual suspects
older engines with less compression are also main contributors
might not be anything but an old trired engine that likes starting fluid

if previous owner used it has probably washed down the cylinders
reducing compression and a bottle of ether and acceptance is the answer

 

There is a check valve on the back of the Davco fuel filter where the inlet line hooks up. It screws into the filter base and the fuel line screws into it. They can go bad, and I have seen junk from the tank get stuck in them and hold the valve seat open. This will cause your problem.

 

You still have an air leak somewhere. I'm going to guess either the filter assembly or fuel pump fittings. I'd buy a new Davco before I started pulling injectors.

 

+1 for the Davco check valve. It is very simple to pull them out and clean them, just don't lose the little spring, do it over a clean pan. If that's not it, I'd guess that you have a small leak somewhere and it loses prime.

 

That check valve at the back of the head should have just been replaced, not inspected. It doesn't take much to have them leak back. I doubt you can tell by just looking at it.

 

How did he check it>shake it, blow into it?

Replace it and rule it out as being the problem.

 

A 60 series needs 195 RPM to start and it needs an SRS signal. when you try starting it, look, with a flashlight into the fuel tank, you will see two tubes usually the front one is the return, if it is sucking air it will blow out air. Never in all my years of working on S60 have I seen a check valve fail. It is a ball and seat with a spring.
For years either cans were yellow, color coding for what they were used on. You can destroy the rings on an engine abusing either.

 

Check valves with a ball seat usually just don't fail by their design, but I definitely have seen junk from the fuel tank hold open a check valve on a Davco filter. Also, using WD40 instead of starting fluid will not cause a big explosion in the cylinders like starting fluid, and it also will provide lubrication at the same time, while starting an engine the same as starting fluid will.

 

They took the stuff out of wd40 that made it a good starting fluid