Hand primer (fuel) pump bad?

[Chuck Jackson]

I changed the primary (water/fuel separator) and started the engine. It ran for a minute or two and died. This seemed a bit strange since it usually runs and then I shut it off and proceed to change the secondary filter (followed by priming). So I started priming it with hand pump. After literally pumping off and on for an hour with no resistance, I decided to pull the primary filter and check to see if it had any fuel...it was bone dry...not even a drop of fuel. Do I really have that much air in the system and should just keep pumping or do I have a bad hand pump?

Btw - this is a C9s and I have used this procedure several time without issues.

[Dave Atherton]

Chuck, Cat 425 are we talking Cat C-12 engine. If that is correct there is a hex bleed plug on
your secondary fuel filter on the top, remove the plug and turn engine over 3 seconds and put the hex plug back. Engine should start right up. Note: the fuel transfer pump on the cat C-10 and up has
larger capacity gears designed for the C-12 and up. Last put a grease rag over the opening that
you removed the hex plug because fuel,will spray all over. Dave Atherton Retired Cat Mechanic5

[Chuck Jackson]

Hi Dave. No, this is a C9s.

[Dave Atherton]

Chuck, not first knowing the prefix ( C-9S 00001 & up ) Cat 425 can be in several engines. At
present looking at SIS program for Cat C9S engine fuel system service fuel filters. Operate the
hand priming pump ( if equipped which you indicated has one ) if excessive resistance is felt,
inspect the fuel pressure regulating valve. If uneven resistance is felt, test for air in the fuel.
Possible air leak at fuel filter base loose fuel line fitting. Check the primary fuel filter drain plastic
or gasket.

Examine the fuel system for leaks. Ensure that fuel line fitting are proper tighten. Check the level
of fuel in fuel tank. Air can enter the fuel system on the suction side between the fuel transfer
pump and the fuel tank. Last put a clear line on the return to tank hose and check for fuel flow
durning engine cranking. Look for air bubbles in the fuel passing through the clear line. If the
engine starts, check for air in the fuel at varying engine speeds. Dave Atherton Retired Cat Mechanic

[Chuck Jackson]

Hi Dave. My engine serial number is C9S00894.  I am not getting any resistance on the hand pump even after a couple of hours. Changed primary fuel filter again (cat) and no change. Checked filter after I felt resistance momentarily and temporarily and primary was half full of fuel and secondary filter (cat also) had maybe an ounce or so. Fuel tank is half full and where it is sitting, the front of the coach is higher than the back because of street grade.

Just to reiterate, this all started when I changed the primary fuel filter and started the engine and it died within a minute.

I will follow up with your suggestions.

[Chuck Jackson]

I decided to go ahead and try prefilling the filters starting with the primary first but as I started to unscrew it, fuel was coming out. Knowing that it was full, I just screwed it back in. I was very hesitant to prefill the secondary filter but did it anyway (in each case I plugged the center hole and poured fuel into the small holes around the periphery) . I only filled it about 2/3rds the way. I used the hand pump but still did not get any resistance. for what ever reason I decided to try and start the engine. It cranked but did not start. I then went back and gave it about 20 more pumps on the primer....still not feeling any resistance. I then went ahead and tried to start it and it fired right up!

Not sure why it behaved this way when in the past I never had this issue....I guess I had more air in the system than I thought.

A big thanks to Dave Atherton for reaching out and helping!