Generator Start Sequence Question: Onan 7.5 QD

[dmastroluca]

First coach, diesel pusher. Newbie tries to cold start his Onan 7.5KW Quiet Diesel Generator. He pushes either start button. The generator does not start right away, it clicks for about 5-7 seconds and then starts. Normal operation? Fuel pump?

[wildebill308]

Congratulations on your new coach.

That is the way it works. The clicking is the fuel pump. Let it run and warm up a little before loading and take the load off when shutting down to let it cool off.

Bill

[manholt]

Bill is right. Start Generator and let it run about 2 minutes with no load, then run whatever you want. My coach is all electric with residential refrigerator. I run my Generator while I'm driving and at the campground, I take the load off and let it run for the time it takes to disconnect toad and shut it off...Same with engine.

Enjoy your DP and happy trails!

Oh, there is no such thing as a Stupid question on this Forum

Carl

[huffypuff]

It is a good practice to run the generator once a month for a hour under load. It suppose to warm up the winding and dry out any accumulated moisture. It is also to flush out the fuel system of stale fuel.

[bm02tj]

Part of the delay is the intake heater and the colder it is the longer the delay.

[wayne77590]

My system manual states to hold the stop button until the green light blinks. This will activate the fuel pump, then puts the start. Once you have it running and shut it down as others have indicated, starting by just pushing the start button seems to work fine. Only when it hasn't been run for a time to use the stop as a fuel pump activator. (But then that is my manual) Onan 6k

[dickandlois]

Dan,

The clicking sound is from the engine fuel pump priming system.

The delay is caused by the preheat sequence for the Glow plugs. Once the engines are warm they will start quickly.

Should you run the unit out of fuel (happens often when driving with the generator running if fuel level is low) Holding the switch in the stop position for 30 sec. or more will prime the system.

This is handy when one replaces the fuel filter or fuel pump. Gets the air out of the system and then the only delay is generally caused by the preheat cycle mentioned above.

Rich.

[wolfe10]

Correct, no intake manifold heater-- it has glow plugs.

[dmastroluca]

Thanks for the replies and thread name change. I just figured since it was already 104 degrees here in Vegas that it would not need to preheat the glow plugs.

Good info in case I run the fuel line dry in the future.

[jleamont]

What fuel level does everyone's generator shut down at? Actual level on the gauge not in theory.

Mine shut down between 1/4 and 1/2, I thought my gauge was inaccurate, but it is correct, trying to figure out why the pickup is so high in the tank (first time I have ever let the fuel tank go that low). I expected it to stall at 1/4 or below. One of those things that is annoying but not sure if its worth adjusting or just be aware of it. Code 36 flashing. After refueling the coach and priming the generator its fine. You have to wonder...running the fuel injection pump dry cant be good for it.

[john_harris]

Sitting, mine has shut down pretty close to the 1/4 mark however i was surprised once while driving that it did cut out at about 3/8 while driving. I now refuel accordingly.

[blakeloke]

Morning Joe,

Our generator shuts down when our dash fuel gauge reads 1/4 of a tank (now).  When we bought the coach we had to have the manufacturer recalibrate the gauge as it would read "full" for 400 miles or so.

I start hunting down fuel when the gauge just gets below 1/2 tank.  I know doing so requires me to stop more frequently but I like the insurance of having plenty of fuel in case there's an issue where I need to "dry camp".....ie. breakdown or "tired of driving & let's overnight at this Walmart".

At home.....I always pull into the garage with a full tank and have several 5 gallon diesel cans on the ready.  With hurricanes and flooding I want to be prepared for extended power outages.

Blake

[hermanmullins]

One of the things on our coach is how inaccurate all of my gauges are. My holding and gray tanks readings are not reliable. My fuel gauge may read below 1/4 and will be flashing LOW FUEL. I will stop and fill up. I have a 130 gallon and will only take 75 gallons. I try to never get that low but sometimes it happens. Sometimes when fueling up I will raise the side I am filling  so I can get a full tank. Yes I am considered odd but some, ok by most.

Herman 

[blakeloke]

Hey Herman.......I do the same thing.  If the island is sloped a bit I use the fill spout on the uphill side to make sure I get as much fuel as possible!

I've long given up on our system levels such as propane, black, grey and freshwater readouts.  I've removed, repaired & cleaned all of the sensors, except the propane, and they work fine until the next time you use them!  Black and grey is a nasty job.  Now I guestimate when I need to dump those and just look at the water tank to see if what the level is.

Blake

[jleamont]

Herman, my fuel gauge never makes it to full. I will try and lean the coach next time to see if I can squeeze more in. I have a large cavity above the fuel level now so it looks like there is room for more without causing a concern. All of my dash gauges are horrible as far as accuracy goes. I bought a Scan Gauge last year and installed it above the camera monitor, I use that in place of the critical gauges since they are so far out of accuracy. My holding tanks all work correctly which is a first for us including the propane. Once that is empty if anyone wants the sensor from it I will gladly pull it since the tank will be removed from the coach and tossed anyway. I was driving when the Generator stalled which would put my gauge around 3/8 like John's does when the generator cuts off.

I always park it with a full tank of diesel and if for one night while traveling I will purchase the fuel where we are parked prior to shutting down for the night, or close by.

 

[kaypsmith]

If on a level driveway, one could use their leveling jacks, or pads, to accomplish the effect, "LOL".

[dickandlois]

1 hour ago, jleamont said:

All of my dash gauges are horrible as far as accuracy goes. I bought a Scan Gauge last year and installed it above the camera monitor, I use that in place of the critical gauges since they are so far out of accuracy.

With an accuracy issue with all the gauges. The first thing I would check is the ground connection(s) at the cluster assemble and then the point where the grounds collect at the common point. From there a single ground cable is often used to connect all the ground to one point on the chassis.

A slight ground resistance change will change the accuracy of the gauges by a sizeable amount. The gauges are reading a resistance change from some style of sensor and it is not a large resistance value wise, so a bad connection can through things off for sure!! A 100 to 150 ohm sensor with a ground resistance of 5,10 or 15 ohm ground resistance will cause a 5% to 15% error.

Rich.

[tbutler]

Good information Rich,  I'll have to get busy cleaning those contacts. 

I pretty much disregard the instrument dials on the dash.  We have the Aladdin System which monitors the engine and gauges electronically.  When I fill the diesel tank, I reset the level at 127 gallons on the Aladdin.  I tilt the coach (airbag leveling) so I can eliminate almost all the air space.  I do this only when we are driving following the fill-up.  If we are going to be parked I'll ease up on the tilting so there is some space for fuel expansion.  Anyway, the dial gauge will show over full and will stay there quite a while.  When Aladdin shows the fuel to be 1/2 gone, the dash dial shows 3/4 tank.  When the dash dial gets to 1/2 tank we're at about 40 gallons on Aladdin.  The pickup for the generator should be at about 32 gallons and that is where Aladdin shows it to be when the generator quits while parked, not driving.  When driving I've had the generator quit around 40 gallons due to sloshing of fuel.  How accurate is Aladdin?  The fuel used amount shown on Aladdin will almost always be within a gallon or two of the actual fill.  Aladdin does not monitor the fuel usage by the generator so this will account for small discrepancies.  I consider an indicator that can tell me I'll take 72 gallons of fuel and be within a couple of gallons to be pretty darn good.

There are exceptions to the use of Aladdin.  The oil pressure is not a live reading.  The dash gauge is the only live reading for the oil pressure.  The propane reading is unreliable, there are times when the indicator system (float?) seems to get stuck at 80%.  Driving will resolve this.  Aladdin is close but I rely more on the dial indicator on the tank for the most accurate reading.

The Aladdin fresh water indicator works well.  I long ago gave up on the indicators for the black and gray water tanks.  Having lived in the coach for quite a while, we have a pretty good idea of how showers and dish washing fill the gray water tank.  Between the two of us we keep track of the likely tank levels and plan emptying them before getting to full. 

[wayne77590]

4 hours ago, hermanmullins said:

One of the things on our coach is how inaccurate all of my gauges are. My holding and gray tanks readings are not reliable. My fuel gauge may read below 1/4 and will be flashing LOW FUEL. I will stop ancient fill up. I have a 130 gallon and will only take 75 gallons. I try to never get that low but sometimes it happens. Sometimes when fueling up I will raise the side I am filling  so I can get a full tank. Yes I am considered odd but some, ok by most.

Herman 

Besides yourself, please name one that thinks "ok."

I have only once (evacuation for IKE) been running the generator when the gauge got down near a quarter tank. we had been running for 3 days when power was lost at the CG due to the hurricane. (Nope! Did not evacuate far enough and 100 miles was not far enough.) The generator was running when we decided to find an area where there was electricity to pump fuel so I shut the generator off as we traveled. I barely made it running on fumes. So I am going to "assume" that our generator would shut off at 1/4 tank.  I really don't want to test that theory again.

[jleamont]

Rich, thank you for the idea on the grounds, not sure even where to look under that dash . My scan gauge monitors all powertrain gauges, including oil pressure and transmission fluid temperature, if it didn't I would be hesitant to drive it.

[five]

One comment regarding fueling.  As all know, diesel fuel foams and causes the pump auto shut off to do just that...stop fueling.  The last time I refueled at a truck stop using the big nozzle, after the pump auto stopped, I put in 33 more gallons by hand.  If I fuel it slowly by hand, I can still usually add about eight gallons after the first shut off before there is too much foam to get any more in the tank.

[jleamont]

21 hours ago, FIVE said:

One comment regarding fueling.  As all know, diesel fuel foams and causes the pump auto shut off to do just that...stop fueling.  The last time I refueled at a truck stop using the big nozzle, after the pump auto stopped, I put in 33 more gallons by hand.  If I fuel it slowly by hand, I can still usually add about eight gallons after the first shut off before there is too much foam to get any more in the tank.

I always look into the tank and check it for foam. Our coach only has a 6" neck on the tank and I can see inside of it, which is good and can be bad, high flow nozzles if not positioned properly will click after the fuel shoots out of the tank. I have to hold it and pick up on it so I do not make a mess.

[dickandlois]

The big fuel filler lines an Diesel fuel will foam up real easy. The one other item - it will not stop the foaming though, is the tank vent lines can cause issues if the metal portion starts to rust out. The big one is the rubber vent lines can have low spots in them when clamps or straps fail. The lines drupe  and fuel collects in the low point(s) and restricts air from venting out of the tanks. 

Those same vent lines problems also cause slow fulling issues of gas powered units!!

Think the fueling issue hijacked a Generator thread !

Rich.

[ccmsm]

We've had this coach since January of this year. It will be 2 years old this August. The fuel guage stops about half way between three fourths and full.  i know the tank is full because I can see the actual diesel in the fill spout. I wasn't gonna try to get it fixed because i thought it would be a major task. Do y'all think it could be as easy as having it recallibrated.   Thanks,   ccmsm

[dickandlois]

32 minutes ago, ccmsm said:

We've had this coach since January of this year. It will be 2 years old this August. The fuel guage stops about half way between three fourths and full.  i know the tank is full because I can see the actual diesel in the fill spout. I wasn't gonna try to get it fixed because i thought it would be a major task. Do y'all think it could be as easy as having it recallibrated.   Thanks,   ccmsm

Think the quick answer is to have a service tech read the resistance of the fuel sensor and compare the reading to the part specifications. There should be a chart that gives specific expected values for a given full level.

Then one needs to know if the error is do the mechanical location, failed sensor, or is it just a circuit grounding issue; or contaminated / compromised crimp / bad wire ?

Depending on the probable cause, that can have a definite affect on cost !

Regarding Gauge readings that are wrong. I first tend to check the circuit ground connection integrity. A bad ground can send any sensor into a tailspin.

Rich.