We have a CAT 320E with 8k hours on the clock. Customer says there is a noise from top of engine. After inspecting, it's a fuel rattle/clatter from the rail pressure surging from 5k to 9k at low idle. All the while the demand pressure is 7200 and no active codes or events. Cylinder cut out passes. If you unplug the rail pressure sensor, the rpms flatten out and it runs perfect. We replaced fuel filters, Drained watered fuel from tank and supplied good fuel, replaced rail pressure sensor and relief valve (no change). Removed fuel control solenoid valve from pump and with key on, it just clicks. Replaced solenoid valve (no change). Attempted fuel pump calibration but it would not pass due to either, low rail pressure or low or high rpms??? Verified electric lift pump operating and has correct flow to and through fuel regulator. Ran product status report and sent to local dealer TC. He suggested a high-pressure pump as the fuel delivery volume was not changing in relation to rail pressure surge. We suspected the pump too. Changed pump (no change). Tried to recalibrate pump. Calibration finally took but only leveled out at low idle. if you run the rpm up it goes back to surging through all rpm ranges. Found injector command fluctuating as rail pressure does. We are leaning toward some degree of software/ecm issue, but does anybody know of another test or trick??
I'm assuming this is a 6.6? Has anyone checked return flow from the injectors? Are there any EGR codes?
Haven’t checked return flow rate on injectors yet. No codes active or logged for anything egr related.
I would start there. The flow rates are tiny on these. Like less than 2 ounces in 30 seconds. And you'll need a special banjo fitting for the transfer pump during testing.
Will do! I’ve haven’t been able to find any good specs on the return rate so thanks.
You have a serial? Ill look it up
Prefix is WBK on machine I’ll have to check tomorrow for the full.
This one is newer than I thought (tier IV). When they changed to bosch pumps, they did away with any specs to check return flow (dumb). All you can do is verify everything else is functioning correctly before injector replacement. Injectors or an EGR problem would be the most logical next steps. I have seen EGR valves not seating closed but not coding.
Well that sucks… I’ll keep digging on it and post back if anything is found. I appreciate the feedback.
I think I would try capping injectors off one at a time to see if that makes any difference you’ve tried most everything else
I meant to add we did try that and rail pressure still fluctuates the same and had misfires on each cylinder.
Can you do individual injector return flow a rate? Often a bad one will stick out simply a higher flow.
Did you try this at low, mid and high rpms? Does the 'delivered fuel volume' tell you anything? Also have you tried unplugging the engine speed sensors one at a time?
We did not try at mid and high rpm nor did we try the engine speed sensors. If weather permits, we should be back on it in a few days and ill report back.