Onan Preheat Sequence 10000 10 HDKAA

[Pat Long]

I am wondering fi anyone has or knows how to prolong the timing sequence for the glow plug preheat sequence?  Mine is set for around 5 seconds and it is not enough time to get the glow plugs to actually start glowing red hot.  Have taken out and tested them and they seam to just start warming up then the engine will start.  If I could get them to temperature I know the engine will start with less hard cold knocking under initial starting.  Its not real cold here in CA can only guess what it would be if it were freezing.

[Bill Lampkin]

Have the same gen unit as you (HDC, I think). I just push the dash sw and, after a few seconds, the gen fires right up. I did notice that after I replaced the fuel filter, it started up more quickly and ran smoother.  Colder here in N Ca!

[Mike Shumack]

How did you set the "glow plug On" time (you mentioned 5 seconds)? There is no adjustment for this that I have seen. The controller turns on/off the glow plugs. Although you saids the glow plugs are getting hot (I assume you have them pulled from engine) it is not enough to watch them get hot - to conclude they are good.

The test for the glow plugs is to use an Ohmmeter and check resistance from + terminal to ground.
They should all read the same (you could find out the exact specs by locating the part number and searching on-line for the part - but if they all measure the same they are probably good.

The OEM glow plug is (Cummins #) 187-1289 which crosses to a NGK 5392 Y720U. The plug resistance is 5000 ohms according to the part spec.

[Pat Long]

My question was has anybody ever increased the preheat time on their genset from the factory setting.  Mine is set at 5 seconds, barely enough time to get the glow plug hot.  The timing sequence needs to be long enough to allow the plugs to Glow Red Hot.   I did pull one ran trough the starting, preheat sequence, did not start the engine, and it only got warm and not glowing hot.  I know its preprogramed into the control board but if you never ask you never learn, so I am asking if anyone has increased the timing sequence?

[Mike Shumack]

The Onan manual says the glow plugs "on time" is controlled by the Controller according to engine temp.

Maybe your engine temp sender is bad (telling the controller the engine is warmer than it actually is).
You might be able to add a resistor to temp circuit to fool controller to thinking engine is colder so glow plugs stay on longer - but you shouldn't have to if everything is working properly.

[Chuck Jackson]

I agree with Mike. There is no set time for pre-heat. The colder it is, the longer it will delay the start for the pre-heat sequence.

[Bill Lampkin]

Pat, Have you checked to see if your chassis battery is  fully charged before cranking the gen? Just a thought. 

[Gerald Farris]

Pat,
I would recommend very strongly against putting a resistor in the engine temp sensor circuit. This will cause the loss of the proper overheat shutdown safeguard that can severely damage your engine. Especially since most all of the generators have at least one or more overheat shutdowns in their life from an unnoticed coolant leak or worn fan belt.

If your Onan engine temp sensor has the proper ohm readings, other than replacing the $1,000 Onan controller in the hopes of getting a longer glow plug cycle, the only way to extend your glow plug on time is to press the start switch and release it just before engine start, then immediately repeat the procedure. There is no adjustment that can be made for glow plug run time.

Gerald

Gerald