brianreed Report post Posted May 11, 2018 IN my 2006 Newmar Mountain Aire 4304 I have a smaller 7500 Onan. When starting it takes a very long time to prime. 30 seconds or more of holding down the start button, it is the same from outside or inside. From outside you can hear it pumping/priming. Once it starts it runs well, and will restart quickly if I shut it off for a couple of hours. But if it sits overnight it will take a very long time to start. I plan on getting a complete service from Cummins next month, and will include the generator service, but want to prepared for any costly repairs if needed.. Share this post Link to post Share on other sites
wildebill308 Report post Posted May 11, 2018 What does Cummings/ Onan say about the time? It doesn't sound to bad to me. You have to hold the switch down while it builds fuel preshure and heats the glow plugs. Bill Share this post Link to post Share on other sites
richard5933 Report post Posted May 11, 2018 Sounds to me like a problem with the check valve in the fuel line that's allowing the fuel to flow back into the tank. Not sure where/if you model has a check valve, but the manual will hopefully have that information. If there is not one, it would not be that difficult to add one. Share this post Link to post Share on other sites
abyrd Report post Posted May 11, 2018 I would check the glow plugs to make sure all of them are working properly, all check electrical connections. I found the main positive battery lead connection on the outside rear of the generator enclosure severely cooroded, cleaned connection and generator started much better and cranking speed was faster. I contributed the corrosion to the salt that is used for deicing roads during the winter. You will need to disconnect the common buss that power each glow plug, they are all connected in parallel. You can check each glow plug with a 12v test light, connect test light clip to 12 v positive then probe each glow plug for connunity, test light will illuminiate if glow plug is good. Jim Share this post Link to post Share on other sites
wolfe10 Report post Posted May 11, 2018 Agree, check with Cummins/Onan OR check in your Onan owners manual. Quite possible that the delay is to give the glow plugs time to heat up as well as the electric fuel pump to run. Share this post Link to post Share on other sites
dickandlois Report post Posted May 11, 2018 1 hour ago, Brianreed said: IN my 2006 Newmar Mountain Aire 4304 I have a smaller 7500 Onan. When starting it takes a very long time to prime. 30 seconds or more of holding down the start button, it is the same from outside or inside. From outside you can hear it pumping/priming. Once it starts it runs well, and will restart quickly if I shut it off for a couple of hours. But if it sits overnight it will take a very long time to start. I plan on getting a complete service from Cummins next month, and will include the generator service, but want to prepared for any costly repairs if needed.. Brian, When the generator is cold there is a delay that allows the glow plugs to heat up before it starts as Brett mentioned. There are service intervals set by the number of hrs on them. Just a note! if you run the fuel level is below around 3/8 of a tank - the fuel in the line feeding the generator can drain back into the fuel tank. When this happens you can prime the generator by holding the stop key down. This only runs the fuel pump! So the next time you start the generator - Hold the stop switch down for 30 seconds and then press the start side down. If the delay is the same - then everything is nominal . No fulling issues, just need the recommended service. The fuel pickup for the generators are set higher in the tank, The coach engines have priority for the last fuel in the tanks. Rich. Share this post Link to post Share on other sites
brianreed Report post Posted June 1, 2018 Thank you all so much for the advice, I forgot I even asked the question here. I took it to Cummins for a full service, fuel filter, oil change and filter, and coolant change. I was having the yearly engine and transmission service as well. I told them about the slow starting, but they did not address as far as I could tell. When I asked it was not in the notes, and when I picked up the only person there was the receptionist so I could not get any real answers. Good idea on checking the glow plugs so I will do that. However I suspect that it is just taking a long time for the fuel to prime. When I am holding the button down you can hear the fuel priming and them the sound changes slighting with the priming and it starts right up. Perhaps that "check valve" is where the issue is. My fuel tank has not been below 1/2 tank the entire time I have owned it. Share this post Link to post Share on other sites
jleamont Report post Posted June 1, 2018 Brian, how long do you hear the pump run before it begins to crank over and ultimately start up? I'll be using ours in 5 hours, i'll time it and let you know. Share this post Link to post Share on other sites
brianreed Report post Posted June 1, 2018 jleamont If it is totally cold and have not been run for awhile it will take about 30 seconds of constant holding of the start switch before it starts. If the generator has been run in the past ferw hours or so it starts within 2 seconds. Once it starts in either scenario it funs flawlessly. To me this is not normal. Share this post Link to post Share on other sites
jleamont Report post Posted June 1, 2018 That is normal, mine is the exact same way. Glow plugs can operate up to one minute before it will start, some engines they will actually stay on for an additional 3 minutes after it is running to keep the air cleaner from the exhaust. Share this post Link to post Share on other sites
five Report post Posted June 1, 2018 5 hours ago, Brianreed said: ... I was having the yearly engine and transmission service as well... If you would add your make/model/year of coach in your signature it would assist the rest of us in answering your questions. What "yearly service" are you doing to the transmission? If an Allison, there is not much to do annually except sample the fluid. Share this post Link to post Share on other sites
manholt Report post Posted June 2, 2018 Quote Allison Transmission I have a sample taken annually, just had my 90,000 mile service done in April...5K miles early, we will eat that up in the next 3 weeks. My point is that it will be another 7 years, before the next full service! My 10KW gets serviced every 300 hours, that's 3X a year! Share this post Link to post Share on other sites
brianreed Report post Posted June 3, 2018 I guess the Allison Transmission doe snot require yearly service, but this coach is new to me and I could not verify the last service. I thought I had my coach in my profile. 2006 Newmar Mountain Aire 4304, with the 400hp cummins. Share this post Link to post Share on other sites
manholt Report post Posted June 3, 2018 Brian. You do, some people can't read. I understand, had the same problem with mine...no service records! Share this post Link to post Share on other sites
wildebill308 Report post Posted June 3, 2018 It is always a good thing to zero out your maintenance requirements when you don't have records. Did they change the fluid and filters on your Allison? Bill Share this post Link to post Share on other sites
