RPM decrease when motoring
- Thread starter med2463
- Start date
I suggest you check your fuel filters and your air filter/intalke. That engine is going to keep running as long as it gets fuel and air...so too little of one or the other is likely the problem.
Engine slowed smoothly from 2500 to about 2200 held for 5- 10 seconds then accelerated back up to 2500. We live with fully charged batteries thanks to 420 watts of solar. I am looking into alternator kicking in,sensing state of charge, then shutting down. Didn't get to see battery monitor, was busy watching fuel filter vacum gauge. Maine?
If it was not pushing black smoke when it slowed, most probably fuel starvation. could be a small air leak (banjo fittings and hose clamps and hose itself) but most probable is filter (s) or if ya have one, the little screen in the fuel pick-up dip tube in the tank.
It is the throttle governor's job to maintain RPM under changing loads. Usually any lag from the alternator energizing is hardly noticeable. Clogged filters usually starve the engine for fuel and become a continuing and worsening problem until replaced; they just do not clear themselves in a few seconds. It will not hurt to replace the filters and drain the water separator. The likely culprit is having or getting a little air in your fuel lines. A fouled connector or a pin hole in the fuel pump diaphragm can trigger an air leak. I have seen similar problems in boats that have had their fuel delivery systems modified by the addition of aftermarket filters or add-on fuel pumps or have had worked done which required the removal of the lines. I'm not saying not to upgrade but to be wary about any add-ons and the connections made to install them.
Thanks all. Gonna change both filters even though vacuum gauge is fine. Also gonna check alternator connections even tho we both heard change in engine before I looked at tach. Will check hose clamps too, but I never heard of a short term air leak. No water in separator, fuel in bowl looks fine .
Won't get a chance to run it up for at least a week while we recuperate in Marathon across the street from Keys Diesel.
Won't get a chance to run it up for at least a week while we recuperate in Marathon across the street from Keys Diesel.
Gonna change both fuel filters even tho vacuum gauge is fine. Gonna check alternator connections even tho we both heard the change in engine rpm before we looked at tach. Gonna change air filter 'cause I found one the PO left. Gonna check fuel line connections even tho I never heard of a self healing air leak, then we will see when we leave Marathon in a week or so.
I tend to agree with Kloudie1. I had the same symptoms, and sure enough, it was a small leak at the banjo fittings. Re-tightened them, and all was well. Never forget what those vibrations can do over time.
A dirty fuel filter makes a lot of sense too.
A dirty fuel filter makes a lot of sense too.
Racor filter was dirty. Very dirty. Surprised engine ran as well as it did. When we get home after Memorial Day I will take off vacuum gauge and get it tested.
Thanks all for your advice.
