I just installed a new set of F1 Mach1 injectors this evening. I ran the truck about 5 miles..truck ran fine. When I got back home I notices a hissing noise from my fuel cap. I unscrewed the cap and it blew off with what seemed to be 30-40 pounds of pressure. Any Ideas???? Thanks...

2001 HO 6-speed

 

You are leaking combustion pressure back into your tank, I have never done Injectors on a 24V, but I am sure someone will chime in with which O-ring you need to look at.

 

Sure you're not exaggerating a bit?
With 30-40 psi it would be impossible to unscrew the the cap by hand.
The cap and the vent on the tank are both set to vent at 3 psi pressure and 3 psi vacuum.

 

according to my shop manual the tank vent terminates in the filler tube, so the only time the tank would vent is when the cap would vent or removed. so maybe his cap is bad and not allowing pressure to escape ....but still, there shouldn't be any pressure in a diesel tank......

 

Thanks for your replies. I removed the F1's yesterday evening and reinstalled my original injectors and the pressure in the fuel tank is no more. I took a look at the injectors when I got home from work this evening and on one injector the copper gasket was half black which pretty much confirms that one was not sealing properly and causing my problem.

As far as the pressure in the tank being 30-40 psi....when I removed the cap s l o w l y and got to the last thread, it shot out like a cannon...along with some fuel. Maybe the pressure wasn't that high but it was close.

I'm going to try to get the Mach 1's back in this weekend...I'll let you all know how it goes.

Thanks again for all your help and suggestions to solve this issue.

2001 HO 6-speed