Hard start and miss cold

[dieseldoc]

I have a 94 f-250 7.3 stroke with 238,000 mi. It is hard starting, once it starts it misses bad until it warms up. While it is cranking it smokes A LOT. Once it warms up it runs ok, has decent power, and doesnt smoke. Tested the glow plug system and found two bad plugs and burned up connector. Replaced all 8 glow plugs, vc gasket, uvc harness, and repaired engine harness. While I had the intake boot off I inspected the turbo for damage(signs of dusting),ok.I also found fuel down in the lifter valley, all hoses to and from filter base were hard. I replaced all the rubber hoses in the vacinity of the filter base. Cleaned out the filter base and replaced the fuel filter. It was ready for a service so I also changed the engine oil and filter. I have run KOEO, KOER, buzz test, cylinder contribution test; all come up system pass. All the injectors sound about the same as the tests are running. I checked actuation pressure while cranking when it wouldn't start,ok. I am going to put some clear lines on the return to see if I am getting air in the fuel system, as well as check fuel psi (what kind of pressure is good? around 70psi?), also going to do a compression test. Is there something obvious I am missing? I am about to start pulling my hair out here. I have to borrow a scan tool for now, but mine is on order. That should help that I can watch things while cranking. Sorry about the long post just wanted to give you all the facts. Thanks for the help in advance.

[DwayneGorniak]

I would check crankcase pressure and then compression. Assuming fuel and oil quality are good. If the base engine is good, I would then bench test the injectors. the Ford dealerships up here were all sent a tool kit for testing the injectors. I would have to look up the number if you need it. Can't remember it off the top off my head. Hope this gives you a start.

[Jim Warman]

A lot of smoke while cranking should indicate adequate fuel....

 

A couple of things that I would consider checking are cranking rpm and crankcase pressure.... Low cranking rpm can keep these things from firing up as can low compression. Both of these are quite easy to check and I would definitely look at these before I went to a compression test (mostly because they are so easily done but partly because both are checking for some fairly common problems....).

[dieseldoc]

Thanks for the suggestions. I will check cranking speed, and crankcase pressure. What are the specs for cranking speed(250 rpm?), and crankcase pressure? I personally think it has a base engine problem. once the engine warms up the miss almost goes away. It still misses when it is warm but much less noticeable. I guess it could be an injector to, they have 238,000 miles on em. I will check that stuff out thought thanks guys.

[DwayneGorniak]

Four inches of crankcase pressure-the engine is done. Two inches-it's on it's way out. Don't forget that a cylinder not contributing from and injector miss will increase crankcase pressure due to the fact that the cylinder is acting as an air pump and blowing compression past the rings. But the crankcase pressure is for sure the first thing to check.

[Bruce Amacker]

I will check cranking speed, and crankcase pressure. What are the specs for cranking speed(250 rpm?),

A good one cranks at about 180rpm warm, anything less than 150 can cause a hard start. Look at glow plug amperage, too, it should be about 190 amps initially, and the relay should have less than .2v drop across the studs.

 

Good Luck!