Happy Easter all I have a 97 Case that runs great overall. Bought not too long ago and one issue is that the 4B engine surges at idle and a little above. Worse when cold but always present some. Off idle does really well. Starts great also. All filters on machine changed. Maybe a problem inside injection pump itself? Thanks
A little more information is required to get specific help @QLW Can you confirm that your engine is non turbo & has the CAV Lucas injector pump?
That is correct. No turbo, CAV
check the return line to tank for flow when idling and check when reveded up, if its a plastic or rubber line could be particualy closed
A surge is real hard to find on a CAV pump.. the only thing I can think of is the "non-return" valve.. meaning theres a check ball & spring in the outlet/return fitting on that application.. They are known problem areas..Sometimes the ball will get stuck & the pressure builds up & blows the front seals out & drowns the crank case in fuel.. A calibration check will not show this symptom.. Is it possible your supply pump is weak.?? I would change that out 1st.. they're inexpensive & a known problem w/ that engine..
I hope this helps. From the Case 4-390 service manual.