7.3L IDI Hard start hot

[joshbuys]

Got a '94 Econoline ambulance 7.3L IDI (non turbo) has a hard start hot. Previously had a hard start at all times, the county shop replaced glow plugs and controller and now has a hard start hot after about a 1 hour hot soak, if you try sooner, it fires right up. County shop replaced lift pump and injection pump with no improvements. Fuel is pulsing out fuel lines at injectors when loosened. Found one battery only has about 390 cca - will have a new one tomorrow.

 

I'm kinda at a loss on this one, haven't worked much on the old 7.3's at all! Any tips/suggestions would be greatly appreciated!

[Jeff_E]

My guess would be you're sucking air. I found a few threads describing similar concerns that may help.

 

http://www.forddoctorsdts.com/forums/ubbthreads.php?ubb=showflat&Number=10543#Post10543

 

http://www.forddoctorsdts.com/forums/ubbthreads.php?ubb=showflat&Number=2636#Post2636

 

http://www.forddoctorsdts.com/forums/ubbthreads.php?ubb=showflat&Number=2606#Post2606

[Bruce Amacker]

In addition to the threads, check the return line/switching valve for obstruction. I had one that the switching valve was blocked on the return side causing hard start hot. Using a 5psi regulator in your shop air hose should show flow to the tank when applied to the return hose on top of the pump. While you're there, check the little return check valve on top of the pump. It should be new, but look through it anyway. It's a little glass ball check valve.

 

Good Luck!

 

[joshbuys]

Alright, got the battery in it, finally got a chance to go through this thing, found a fuel leak at the rear fuel return line junction block - waiting for parts - I suspect the fuel system is becoming vapor locked, I'll let you know how it goes next week sometime when my parts show up.