Yesterday my truck was dumping a lot of diesel from the motor. I went to try to find out from where and now it's not leaking. Any ideas what it could have been?

 

Injectors, fuel lines? How much fuel are we talking about?

 

It was probably about a gallon of diesel. But all day today there was no leaks

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It looked like maybe from the top of the motor somewhere

 

Replace the copper washers on all of the banjo bolts on your fuel lines,
replace the O'ring on the fuel filter canister,
and replace the funny shaped O'ring on the fuel pressure regulator.

If you can't find out which it is, fix it all.

Have you replaced the spring in the fuel regulator (with the blue one)?
If you did this, I would suspect the regulator cover is not on right or the bolts are not tight (they don't have to be real tight, but the cover might have been cocked a bit when you tightened the bolts and then engine vibration caused it to slip, the bolts could be loose). You need to alternate tightening the cover bolts, a little at a time, until all sides are snug, and then tighten to spec. (and sorry, I don't know the torque spec, maybe someone will chime in with that one).

 

I haven't replaced anything. I thought it was just weird that it would stop leaking by itself

 

My truck did that one time bout a year ago. . . Never since and no explanation. . But it's really only about a pint . .little looks huge when you paying top dollar for diesel! Like a pressure regulator released but that goes back to tank. . .and you can eat off my engine compartment If I ever find out why I will share . . Guess a life mystery!

 

Mine smells of diesel almost all the time, which means there's a small leak somewhere.
It used to leak to the point of dripping on the driveway at one point, but replacing some of the copper washers got that under control.

 

Ya mine always smells like diesel. Yet to find the source.

 

It did it again but not as bad. It looks like its the banjo bolt on the passenger front head

 

OK,
So, have you tried to re-tighten it?

There are copper rings on each side of the banjo bolt.
If they start leaking, it seems logical to tighten them down again.
However, in many cases, it won't help. The best way to eliminate the leak is to replace the copper washers with new ones. These washers create a seal by crushing. If you try to use them again or re-tighten them they don't crush any more and start leaking.