Need 6.2 help with a strange NO/hard start condition

[2DRTURBO]

I have a very stubborn 6.2 CUCV I'm working on and need some help. Already replaced the INJECTOR PUMP and NO DIFFERENCE. So here's what it does.... It has a strange condition I haven't seen much on these 6.2 CUCV's over the past few years of working with these. It truly has me stumped. Glow Plugs are good, fuel clean, lift pump working fine, no visible fuel leaks, new fuel filter, IP gets power, and it runs good once it gets going. But what it does is when cold it will start up, run up for a few seconds the FIRST TIME, then die. Then from that point, if I re-cycle the glow plugs and try to start it again, it just crank and cranks. But after maybe 2-3 long cranking sessions and some application of throttle it will hesitantly start up after some stumbling and coaxing. It will then more or less smooth out and run fine and idle nicely after maybe 30 secs. Now, when I turn it off and then fire it right back up, it starts. BUT, if I let it sit for 30 minutes or so, NO luck. It won't start at all, not even with coaxing. WHAT is going on with this truck? Its a clean truck, rust free, and the rubber return lines look decent, not leaking or too dry.

 

[ak diesel driver]

sounds like air in the fuel system. put a piece of clear tubing on the IP return line and see if you have air bubbles. Have seen lift pumps suck air and not leak so just because it pumps fuel does not mean it's good

 

[iamdave0887]

sounds like air in the fuel system. put a piece of clear tubing on the IP return line and see if you have air bubbles. Have seen lift pumps suck air and not leak so just because it pumps fuel does not mean it's good

x2 on the air in the fuel system.

Biggest issue was with the stock "box" type fuel filters, but the military units from what i've read did not have the problematic restriction switch like the civilian models. ON the civilian models if fuel pressure dropped below a set pressure the WIF light would come on, indicating a restricted filter.

Problem was the o-ring on said restriction switch wasn't designed for ULSD fuel, so it dries out and hardens up, causing a leak.

Mine leaked a tiny bit of fuel, but never enough to drip on the ground. I had the same issue you speak of. It would start fine, then die out. She'd crank over fine and eventually re-start, and then sit there and cough the remaining air from the lines and it would be fine for the rest of the day, until i went to start it again either after work on my way home or the next morning.

 

[2DRTURBO]

yes, this is the military version so no restrictionswitch. The filter is new and I took a look at filter mount on the firewall and it looks good, no cracked or dried out parts. Maybe try switching out my lift pump? Any other suspect places to look or ideas where/how I am getting air in?

 

[just a number]

first thing is follow AK's suggestion about the clear tubing. you'll need to do it to confirm that you've got the problem fixed anyway. you can have a leak anywhere from the tank hookup(even inside the tank,bad pick up) all the way to the front.

does the CUCV version get the dual tank setup?

how much fuel is in the tank right now?