Cummins El Paso

Access is dependent on your unit side V rear rad. On mine it is very easy to open the hatch. It is not in the floor under the bed or in the closet. I opened it up but the mechanic was able to climb into the engine compartment and reach. You need a skinny mechanic. There is one other possibility for your problem. When they removed the filters were they full? Are the thick o rings installed? On mine there was one filter mounting flange that was not machined straight. Don't know how it worked for 7 years. BTW there is a new improved filter . I am sick today so cannot get it but hopefully will find the # tomorrow. If the only code is that 559 Cummins has a whole list of things to check or replace. But I would suggest to just do the things I did. Anything else is going to be mega bucks. Do you have those plastic fuel lines? Could one of them have rubbed on something and made a pin hole? Please keep us posted. ON EDIT: What brand of filter are you using?