Fuel System Air Leak

[abfiegen]

My truck had been sitting for 5 months before I got it started a few days back. It started up with only 4 cranks to get the fuel system primed. If the truck sits for approximately 12+ hours it will start progressively harder the longer I wait. Classic air leak symptom. My question is where would you start with repairing an air leak? I doesn't appear to be severe enough that fuel leaks out so visual inspection won't do the trick. Would the optimal solution be to start replacing fuel hose downstream of the injection pump and hope that solves the problem or are there alternative methods? I perceive the return lines to be the most common source of air leaks. Any particular line that would be best to start with as it is the most likely culprit? Are leaks common prior to the injection pump? I wouldn't imagine so as it is a much lower pressure. I'd also considered installing an electric fuel pump in the past so if I were to implement this it may mask the air leak problem by priming without cranking.

As a secondary question, my diesel has been sitting for 5 months in the tank. Should this diesel be siphoned and replaced? I've heard diesel forms solids after 2-3 months that can gum up injectors. I've also heard these trucks will run on anything and everything. I don't want to find myself in a position to where I need to replace injectors which would then possibly cause me to have to replace the IP.

Thanks for any input.

 

[IDIoit]

if you cant find a visible place where fuel is leaking,
i would suspect the WFS first. located on the driver side in between the brake booster and fender.
every 87-91 truck ive worked on, leaked air, but not fuel.
those things are straight garbage.
you can just loop it, for now, but get a water separator back in asap.

draining the tank isnt a bad idea, it will do more good than harm.
and youll have fuel for starting fires

 

[abfiegen]

Thanks for the advice.

I installed a new FWS before I went to trying to start it up so it's brand new. What else could be done to prevent air leaks at the FWS?

 

[IDIoit]

Thanks for the advice.

I installed a new FWS before I went to trying to start it up so it's brand new. What else could be done to prevent air leaks at the FWS?

did you delete the stock one?

 

[abfiegen]

I replaced a Wix fuel filter with another Wix.

 

[Agnem]

Conventional wisdom, is that if you have any years on your return lines that you just install a new return line kit. Once you start fooling with the existing ones, the leaks will only get worse and be more numerous. You can put pieces of clear vinyl tubing in temporarily to locate the source of the leak, but it is time consuming, ******* the starter and ultimately leads to the same thing.

 

[IDIoit]

I replaced a Wix fuel filter with another Wix.

a 90, also has a tube on the firewall with a plunger. it collects water from the incoming fuel line, separate from the filter itself.
when the rubber tip of the plunger gets old, brittle, and filled with crud, they sometimes will suck in air.
a kinked rubber fuel line will also let your system suck in air.
if i were you i would replace every single piece of rubber line, not nylon.
buy a new return line kit, with properly lubed viton 0-rings before you twist the return caps on. and go from there.

ive installed a few return line kits from various venders, Mel's kit is the best IMO.

and on that note, make sure the brass fittings for the return lines ( at the fuel filter outlet, and the "return line manifold" thats located by your throttle cable mount on the firewall)
are the same size as the return lines. thats a great place for these engines to suck in air when you have 3/16" nipples, 1/4" line, and compression clamps.

Green = 3/16 6.9L
Red = 1/4 7.3L

 

[abfiegen]

So I found my leak. Opened the hood and diesel was spritzing out of the first injector on the passenger side of the engine right next to the fuel filter. It appeared as though the injector cap is different than all the others on that cylinder. Should it be that way? I haven't ever heard of that.

 

[IDIoit]

pictures are priceless.

 

[abfiegen]

Yeah I figured that would be requested. I'll get those taken and posted tomorrow after work.

Thanks again for your help.

 

[abfiegen]

This first photo is what the injector and injector cap assembly in question looks like.

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The following is what the remaining 7 injector cap assemblies look like.

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That gold component above the first union and that second union are the parts that I am unfamiliar with. This is for the injector right next to the fuel filter housing as you can see. It was my impression that all return line kits only come with the two o-rings, new cap, and washer for each injector. The top union is quite stuck and when I try to wrench it off the steel injector line gets torqued. I don't want to damage that obviously...

 

[abfiegen]

I apologize. The first photo is actually what the majority of the injector cap assemblies look like. The second is the assembly in question.

Thanks.

 

[IDIoit]

all those caps are the same, the nipples are clocked different for the ease of line routing.
the difference youre seeing is the timing pulse adapter all 7.3's have them.
only on #1,(for trucks, #4 cylinder for vans) this is the line you attach to, to time your engine. this is correct.
those caps are for a 6.9 FYI
if you switch to 7.3 caps, make sure you address the 3/16" brass nipples.
you are in need of new caps and return lines.
post back once you swap them out.

 

[abfiegen]

Okay, I had figured that was going to have to be done. I was looking at a return line kit from Conestoga as I'd heard good things about their kits. How can you tell the difference between a 6.9 injector cap and 7.3 injector cap just by appearance? Are you suggesting that the nipples on the caps will be a different size if I install 7.3 caps and will therefore need new hose? Is that what you meant by "address the 3/16" brass nipples"? I'd assumed new hose was in order as well.

Thanks for all your help!

 

[IDIoit]

take a top view picture, i will help you that way.
yes i can tell the difference in the size of your return line, just by looking at the picture.
how? because i have a Mechanical eye that was installed in my eye socket at birth.........

seriously, did you read my earlier posts?

for not reading my earlier posts CAREFULLY! you must repent, and read this site 5 times. or more, until you understand it.
http://www.conestogadiesel.com/support/fuellineroutingoptionsforfordidiengines.html


new return line systems come with new hose, o-rings, caps, clamps, and a few olives. among some other misc. pieces.
if i were you id buy extra olives(rubber grommets for your fuel system) and do your fuel inlet and outlet lines from your filter also.

i will not tell you to not come back until you understand that site, and post a picture.
as i am not a figure of authority for Oil Burners.net. im just a pawn, with my queen in my pocket in this game called chess.
but i wont open this thread again
thank me by getting your truck running tip top!