Old timer told me I was killing injectors with my fuel filter change routine

I had a guy who's been turning wrenches since the 80's watch me change a fuel filter on a Cummins ISX last week and he stopped me mid-job to say I was letting too much air into the system by not pre-filling the filter housing. He showed me his trick of cracking the return line banjo bolt while cranking to purge the air fast and I swear my next start up ran smoother and quieter. Has anyone else got a weird old school trick like that that actually works better than the book says?

3 comments

3 Comments

cora5181mo ago

Oh man that IS a good one. I had an old diesel mechanic show me the same trick with the return line banjo on a 5.9 Cummins and it absolutely works better than prime and pray every time. I swear the factory procedure of just cranking until it fires feels like you're torturing the starter and glazing over the cylinder walls with raw fuel. Another one I picked up from a guy who worked on Detroit 2-strokes was to put a little ATF in the fuel filter before you screw it on for the first prime, it lubes the injection pump and helps it purge faster.

victor7791mo ago

The ATF in the filter trick is solid, I've done it on a few old Powerstrokes too and it definitely cuts down the dry cranking time. It's basically just giving the injection pump a little insurance policy on its first few strokes before the fuel gets there. The only thing I'd add is don't overdo it on the ATF amount, a couple ounces max or you'll smoke like a freight train for a few minutes.

jennifer8331mo ago

Used to think you were crazy putting ATF in a diesel fuel system but I tried it on my 7.3 after a filter change and it fired right up with barely any smoke at all... definitely changed my mind. I was always one of those guys who just cranked and prayed but that trick saved me from replacing a starter that was already getting tired. Now I keep a quart of ATF in the truck just for this.