Chasing a fuel leak/air intrusion problem that is beginning to really frustrate me

[92LongBed]

Hi All, I have a 92 F350 CCLB 7.3L Banks Turbo, the truck has been falling apart since last year in numerous ways, replaced the glow plugs/GPR last year and had it running nicely again. Then ran into some electrical issues and replaced 3 batteries before I finally got 2 that stood the test and could start this truck. I changed the negative portals on the negative cables but I am wondering if I need all new battery cables because my truck will sit for a week and the batteries will be weak to turn the new starter. I think I ruled out a parasidic draw on my electric system by testing for one with an instructional video on youtube but I dont think my multimeter reads OHMs/AMPs. I replaced the starter last month because it was cranking extremely slow with 12v in both batteries and now I have been having hard to start troubles.

Once I installed the new starter it took a bit to burp and cough and get started and I ran under the hood to try and see if anything was happening and I noticed a pretty big fuel leak on the passenger side return line so I went ahead and put all new fuel return lines in last week. No more leak when I can get it running so thats good. I attempted to bleed the system because I had to track down a rethreading tool to fix a minor issue on one of the injectors so i knew a ton of air and fuel drawback happened and starting would be very difficult and it was but I had my mom hold the schraeder valve in and left the front driver side fuel line cracked to help bleed all air out and the truck FINALLY started after about 7-8 cranks. It ran rough but stay alive until I ran around and closed the front driver side injector and it immediately started running weak and eventually shut off. (I need opinions on why this happened) I assume when I shut off the air being sucked out of the injector/fuel line i left open it began dragging air back in from wherever my air intrusion probably lies.

I've been digging all over Oil burners and have seen some discourse about bad fuel selector valves causing issues so I took mine off today. My tanks never had any issues switching, both ran the truck nicely whenever I needed to change so I knew it wasnt the malfunction but figured air could be entering at any of those 6 connections. (I need opinions on how to remedy air intrusion on that) would it be clamps? I am trying to learn how to be a better mechanic for my vehicles so any tips help immensely. Once I finally got the FSV off diesel was going everywhere so I am guessing all is good with the functioning aspect of the FSV I blew through all connectors and there seemed to be no debris or stoppage but I peeked into the fuel line connectors and there was some grime and dirt around the inside edges.

I am looking to this forum for things I need to check. I am running out of ideas and I know I still have the tanks and their parts but I dont know where to begin. I also have a rubber hose coming out of my front tank that is just dangling but has a connection to the top of the tank, is this an overflow mechanism or is it the root cause of air intrusion. I can add a photo if needed. I checked my front tank for pin holes and couldnt see anything. Havent looked at the back tank because its above the spare and I have been troubleshooting top engine fuel lines and now the FSV. the Lift pump under the engine block looks good with nice connections and I read on this forum that if you wait 24 hours and then try schraeder valve and nothing comes out you dont have an air intrusion unless the truck is trying to run or start. Well I did that trick and no air shot out after not having the truck cranked for 24 hours. I havent replaced or looked in the fuel filter yet but its spitting fuel when cranking from schraeder valve.

I believe i've shared all i have done. I'm sorry for the long post. I really tried to figured this out myself but I need some veteran help. Any questions or suggestions will be greatly appreciated. Thank you

 

[John_piv]

If you've got the time to do it, the best way I've found to locate a source of air intrusion is with clear hose. Tractor supply sells it for next to nothing. Run some clear hose from your tank outlet to the selector switch, then the switch forward. You can either replace the lines, or do what I did and splice into the lines. Although if you splice you could create a new source making false positives.

With the clear hoses installed, start the truck and get underneath. Look for bubbles in the lines and follow them as far back as you can. Where ever the bubbles stop and it's just fuel is where you leak is located.

Worth a shot if all else fails. Worked for me. Good luck on sorting it out!

 

[92LongBed]

If you've got the time to do it, the best way I've found to locate a source of air intrusion is with clear hose. Tractor supply sells it for next to nothing. Run some clear hose from your tank outlet to the selector switch, then the switch forward. You can either replace the lines, or do what I did and splice into the lines. Although if you splice you could create a new source making false positives.

With the clear hoses installed, start the truck and get underneath. Look for bubbles in the lines and follow them as far back as you can. Where ever the bubbles stop and it's just fuel is where you leak is located.

Worth a shot if all else fails. Worked for me. Good luck on sorting it out!

thanks man, i have some tests i'm going to run this week to rule some more options out. this is a smart one i hadn't thought of, ill add to it. thankfully this isnt my daily driver

 

[Danielle]

I find mine with a smoke machine turned to almost no psi, below where the Guage on the machine can read.

Smoke all the parts separately, and hang out with the machine. I use scented baby oil, sometimes I smell the leak before I see it.

Sometimes the leak is just a drooling wet line that you wouldn't think could cause all the trouble.

My most recent one I found was the fuel heater on top of my filter housing. It was dripping so slowly that I thought it was coming from my #1 injector area.

The one I just found on my idi bus was a weird "repair" someone made but was hidden so never saw the leak, just could see drools of smoke, had to use stick camera to see what was going on in what I thought was a solid line!

Our trucks are old and have had many different hands in them repairing them in creative and frustrating ways.

Even though people can brainstorm, sometimes with older vehicles it's something whacky no one could anticipate, can be super frustrating