Hard starting Onan

[Nomad Willy]

Compression is very important for starting.

If it’s low putting SeaFoam in the cylinders and letting it sit for a day or so the SF will/should penetrate the ring lands and loosed up the rings. Then the spring like force should increase sealing and compression.

I’ve freed up old outboards (in my youth) that couldn’t be turned over to running and starting well.

 

[High Wire]

No gauges eh? Pretty tough single handed. Bypass one and only one cutout at a time and see when you make it 1 hr+ run time. Start with the exhaust high temp. They seem to give the most trouble. Making it thru an hour is not proof of a failed switch, but only one data point.

 

[BruceK]

Don`t be too hard on the Onan. My previous boat had a 3 "button" MDKD 6.5 Kw, start solenoid played up, replaced, all good. The current EQD 7.5 Kw with the single rocker switch control has been good so far. Not at boat but doesn`t the Switch panel have an error display "screen"?
I feel your frustration, esp with the Seakeeper out of action, but in my experience Onan(Cummins) is a robust good product. What hours are recorded, I`d guess it`s run some feeding the Seakeeper. I hope you can easily find a tech. to sort it out and resume the journey soon.

 

[Hippocampus]

Been underway. No stops except to refuel in Tolchester. Believe whole issue is crud at bottom of fuel tank. Nothing to do with Onan. To hard to repeatedly change racor so went inside. Now ~1/2 down chessie. Refueled so we don’t burn bottom 1/3rd of tank. Genset draws from starboard tank. Cummins from port. Racors for main clean as is bowl. Will boroscope after arrival. ETA 1 am. Constant low tens.

 

[Gordon495]

Try and look at that stop solenoid and see if the linkage is hanging up somehow. Even with it running you can check to see if it opens all the way. It maybe that simple. Also I thought that maybe it's a card issue, When it warms up there maybe a break in the circuits that are causing it to shut down. I have no idea of your model or if it even has a card for the operating system but worth looking into. Hopefully you've got it figured out though. When it does it's shut down what position is that stop actuator in ?? is it open or closed ? If it's closed then something is telling it to shut off or maybe it cannot remain open because of a faulty card acting up. If it's in the run position then you know it's either injector pump or fuel starvation. Is there any chance you have any air trapped in the injector pump ? just look at the manual and see if you can bleed it. Also check your battery voltage and make sure your alternator is working and putting out proper voltage which should be around 14 volts if it's a 12 volt system which I'm assuming it is. If the voltage regulator is faulty then it maybe over charging and giving the genset high current. I would imagine these newer gensets have safeguards in place for low or high voltage being thrown at them. For the battery just use your volt meter...Connect the negative probe to your start battery neg terminal and as long as you can access the individual cells, then put the positive probe into the electrolyte and it will give you the cells voltage. Check to see if it's consistent right across. Programable cards can be trouble so there is a chance. Check that solenoid

 

[Trawler_traveler]

Our 8 kW Onan had two issues related to starting.

1st, it needed to have the glowplug on for at least 15 seconds. It was quite cold-blooded.

2nd, the electric fuel pump was slowly dying and weak. Replaced it and all was great after that.

 

[jrow]

Check the starter battery. If the engine doesn't spin fast enough to create compression heat, starting will be tough. Don't ask me how I know.

 

[Hippocampus]

As said believe troubles due to crud in bottom of starboard fuel tank

 

[DaveGibson]

It's one of three things. Fuel, fuel, or fuel. I had a problem with my Ford Lehmans quitting after running. After wracking my brains and blowing money on mechanics, I found it was a 1/4" elbow installed in the 3/8" fuel lines. I replaced that and problem solved.

Make sure your pick-up tube for the Onan is low enough in the tank and follow the lines back to the generator from there. Make sure the lines are the correct diameter and that there is no reduction in size. Replace the fuel lines if you can't find anything. I doubt the problem is the generator itself after all you've done.

 

[Hippocampus]

Yup. Think you’re right Dave. Will post results after boroscope.

 

[Alex F]

...Starting to believe it’s not an air leak as it runs fine once you get it going...

IMO, you just answered your own question. I've had my share of chasing an air leak for a while. However, the key symptom was generator shutdown after running for sometime (30min, 1hr, 2hrs...no consistency).

Based on my experience, I can't imagine how the genny can run fine if you actually had an air leak.

Your interpretation of the genny "running fine" could be not exactly valid. It may sound fine, but you can't be 100% sure what's going on inside until you do some detailed investigation.

To solve your issue, I'd start following the logical chain:
1. Does the lift pump deliver fuel to the specs? - sounds like yes, since it gives you enough fuel to keep the engine running, once it starts.
2. Does the high pressure pump deliver fuel to the specs? - you'll have to take it to the qualified shop for 100% answer. However, you can do basic visual test by opening each port and crank the engine to see if there's fuel coming out of each port. If there's anything abnormal, you should be able to see it.
3. Does the fuel get properly delivered to each cylinder?
4. Does each injector operates to the specs? - you'll have to take the injectors out and bring it to the qualified shop for 100% answer. BTW, the same shop should be able to service your HP pump and injectors.
5. Does the fuel freely returns back to the tank?

Until you start checking the items off the list, one at the time, we obviously won't be able to solve your problem. But depending on the age and the hours, I'd be focusing on items #2 and #4. If the HP pump doesn't deliver fuel 100%, you would not hear it. If an injector is not operating 100%, you would not hear it. That's where professional shop comes into play.

Lastly, let's assume that air got into the system. If you locate a bleeding valve on the HP pump, you can loosen it and let the air escape, until you see clean and bobble free fuel flow. If you don't see any bobbles, then theoretically, there's no air in the system. In any event, once there's clean (air free) fuel is getting to the HP pump, there should be no reason for your genny not to fire up quickly. If it doesn't, it's clear that the problem is elsewhere, meaning that you should be looking at what I've described in bullet-points above.

 

[Alex F]

.... It’s real hard to start. Once going it works fine. Doesn’t skip nor does output vary....

...As said believe troubles due to crud in bottom of starboard fuel tank....

I could be missing something, but IMO the symptoms and the cause don't add up. If you had bad fuel and line blockage, it shouldn't fire up and just run fine. With dirty fuel you should easily see the racor getting crud build up.

Dirty fuel issues are usually solved (at least temporary) with replacement of both filters (racor and secondary). I doubt that 3 mechanics were unable to solve this issue. I think there has to be more to the story.

 

[Hippocampus]

Think when still and flat draw for genset draws clean fuel after the bad fuel passes through.
At 10 kts bow rises. Fuel floats on water. With tank tilted fuel draw for that starboard tank is now in water and silt so genset fails. When restarting after boat has sat after a failure the line from tank and the genset still have the bad fuel/water/sediment in them so hard start. Once cleared thing runs fine as long as the boat sits still. Fuel draw is from aft end of tank.
Also on last day of transit starboard and port tanks didn’t self level. This boat has two 300g saddle tanks. There’s a crossover which is designed to always be left open. Main engines draws from port tank. Genset starboard. Port tank fuel level fell. The starboard did not at times and slowly at other times. (Using sight tubes so accurate). That suggests the crossover line was intermittently fully or partially clogged. That’s another suggestion there’s junk at the bottom of the tank(s).
So continue to believe all symptoms due to inadequate use of the boat for the last four years resulting in crap/water in fuel tanks. That being the case the above conversation is informative and appreciated but most likely not relevant. The first thing to rule out is sediment/water in the bottom of the tank(s). Await boroscope with interest. Occum’s razor “any single explanation that’s explains all symptoms is more likely to be correct than multiple explanations to explain each symptom “ . The razor usually works in medicine and also other settings as well. Crap in bottom of tank(s) explains all symptoms.

 

[JRO]

How old and how many hours?

 

[mvweebles]

Hippocampus - following this. Do you have a visible sight bowl on your secondary filter such as a racor 500? Wondering what is leading you to believe crud is at play. Not unheard of for thr tank on a sunny side of a boat to have more junk than the other.

Not sure how far you're going, but installing a small electric fuel pump from NAPA inline might be an inexpensive quick fix until you can fully diagnose and remediate at your destination.

Good luck.

Peter

 

[Hippocampus]

At destination. Have multiple projects yard here is going to do. Will go into shed shortly. Have changed genset primary filter twice within less than 30 h of use. Both times water and sediment. Running a brand new housing with R20 at 10u. Have drained bowl once while on recent transit and coffee colored with sediment lining bottom of clear container (empty water bottle) which I saved and let sit since we did landfall. Then a layer of water even more apparent. So there’s little doubt starboard tank has crud and water in it. Only questions are:
Does the port tank as well? Interestingly the racors on that side are clean and just fuel in the bowl.
How bad is it? Mild and polishing will suffice or bad and needs access holes to clean walls before polishing?
To my mind needs a look see with a ‘scope before proceeding further.
Do you agree?

 

[mvweebles]

I've never used a boroscope so interested in bigger TF brain. I would think that it would be better for open space vs liquid so interested in learned responses.

A good friend with a 2014 boat that carried 700 gals total had issues with one tank but not the other, so not unheard of. Was Florida and the sunny side of the boat.

Thanks for the candor Hippocampus

Peter

 

[crashley]

Valves

Why is there a connection between supply and return line
I think air is getting into the supply from the return line
Your symptoms indicate air getting into the system

 

[crashley]

Also if it starts instantly after priming it is most likely air getting into the system

 

[Alex F]

...This boat has two 300g saddle tanks. There’s a crossover which is designed to always be left open. Main engines draws from port tank. Genset starboard. Port tank fuel level fell. The starboard did not at times and slowly at other times. (Using sight tubes so accurate). That suggests the crossover line was intermittently fully or partially clogged. That’s another suggestion there’s junk at the bottom of the tank(s).
So continue to believe all symptoms due to inadequate use of the boat for the last four years resulting in crap/water in fuel tanks.
.....
..... Crap in bottom of tank(s) explains all symptoms.

This vital info was exactly what was missing in my picture of your situation. When giving my recommendations on troubleshooting steps, I assumed that all has been addressed on the fuel side, having clean fuel getting to the lift pump. Now it all makes sense. Obviously, until you ensure that both tanks have clean fuel, all bets are off.

 

[BlimpDriver]

Bad fuel, yuck!

Siphon the fuel tanks, yep, stick a clear 3/4 inch hose in the tank and have a couple five gallon tanks ready. Have enough siphon hose to move around on the bottom of the tank and remove the crude or crud or crap all the c words. If you have the ability to store this bottom crap for a winter it will separate out and you can use it in your old tractor, don’t pour out the crap. Pick ups are rarely at the bottom of a tank and years of fueling introduce all sorts of crap in a tank. Bad fuel is more common in diesel vehicles of all sorts, if simply is dirtier than gasoline. The hose nozzles are large and can be contaminated with dust , bugs and other impurities. Filters are a last line of defense, keep the tank clean.

 

[skipperguy]

Suspicion

On our new to us boat there’s an 11kw Onan. It’s real hard to start. Once going it works fine. Doesn’t skip nor does output vary. First thought it was an air leak as it will start after 2 minutes of priming and after 1 minute of priming if restarted within an hour of shutdown. So looked at all the fuel hoses and clamps. They’re fine. Then replaced the racor primary external fuel filter and the one inside the enclosure. Then the housing for the racor. At that point no joy so blew money on mechanics. So far 3 different mechanics have looked at it. Lift pump is fine. Weirdly it has anti siphon valves inside the enclosure. One seems to go from supply to return. They were replaced. At wits end. Can’t find an air leak. Don’t see any fuel on the diapers or on the engine. Starting to believe it’s not an air leak as it runs fine once you get it going.

Thoughts?

I have read the other responses but my suspicion in adequate cranking speed or a week “spark plug”. Had an onan 7.5 for 26 years

 

[halfmoon]

Onan problems

Previous boat was Albin 28, had been on lift for 3+ years. Engine stopped after few hours run. All attempts to fix problem including fuel polishing x 2 and multiple filter changes ineffective. Trailered boat home. Pumped tank dry, gained tank access and found many large, as much as 1/4" flat crystals in tank. Believe they were product of reaction with fuel stabilizer. Crystals dissolved quickly in water, not in acetone.So, put enough water in tank to cover bottom, let it rest and rock in boathouse
overnight and pumped salt solution out, wiped tank dry and problem was finally solved. Unfortunately, I don't remember the stabilizer used by PO.
Crud in bottom of tanks can be very large particles that take time to accumulate to slow and eventually block fuel flow.
Good luck in cleaning out the crud.

 

[Hippocampus]

Did boroscope today. Couldn’t see absolute bottom as still a bit of fuel in back outboard corner of port tank. But what we did see looked ok. Think we might get away with just putting a hose at the extreme bottom through the fuel guage hole running it to a pump and through filters then putting it into the starboard tank. Then reversing port to starboard. Do this with crossover closed. That in effect will polish the fuel but especially the bottom of the tanks. Hope that serves. Of course will boroscope each tank when empty but think we can get away without needing to cut access holes for a real cleaning job.
Believe the reason there’s much more water in the starboard than port is the engine draws from the bottom of the port tank so in effect was polished at a much great rate than the port one which feeds the genset. Think the crossover is just a bit higher than the draws which could explain why the port tank has less water.
As previously said the racors for the main are clean. The smaller racor for the genset had water. I let that drain into a clear bottle. After 24h of that bottle sitting just water for few inches and a wee bit of sediment at the bottom.
So now think all the troubles due to lack of usage for four years. Hoping we skated big expenses. Get rid of the water, use biobor and use the hell out of the boat. After a few more racor changes as we use the boat should hopefully be good to go.
Think our troubles keeping the genset running was due to the bow rising and being kept up for 2 1/2 days so water puddled in the aft portion of the starboard tank. Then the pickup saw nothing but water.

 

[Patclem]

Good thread

This is a great thread. Fortunately or unfortunately we don’t have stabilizers or generator on our Gulfstar 36. I hope I never have to clean the tank out because it’s fiberglass and access is pretty horrible.
Fuel pickup is usually towards the bottom of the tank. Water sinks as diesel floats. We have Racor 500’s on both Lehman’s, plus the two fine particle filters mounted on the engines. If I had a generator it would get a Racor 500 too.
Someone told me once that most of the fuel lifted (after passing the filters) to the engine is returned, so double or triple your burn rate and you’re actually getting polishing action on your fuel.
I’ve heard more stories of folks going into rough seas for the first time in a long time, get the bottom of the tank stirred, and engines konk out. I’d be interested in DIY methods of inspecting the cleanliness of the tank bottom. I don’t get any water in my 500’s.

 

[mvweebles]

Someone told me once that most of the fuel lifted (after passing the filters) to the engine is returned, so double or triple your burn rate and you’re actually getting polishing action on your fuel.

I’ve heard more stories of folks going into rough seas for the first time in a long time, get the bottom of the tank stirred, and engines konk out. I’d be interested in DIY methods of inspecting the cleanliness of the tank bottom. I don’t get any water in my 500’s.

Depends on the engine. DDs circulate fuel partially as lubricant and coolant. Many engines return very small amounts of fuel. Warm fuel does increase possibility of condensation though so there's no free lunch


No magic to inspecting tanks. Need a decent sized clean out port for each baffled section.

Fuel tanks are definitely a case of "ounce of prevention is a pound of cure." If you have deck mounted fuel fills, make sure the o-rings are sound.

Glad you've had good luck with fuel.

Peter

 

[rgano]

My Yanmar uses fuel via and internal cooler to reduce the oil temperature. It takes in 22 GPH at 2900 RPM and only uses 8.7. That returned fuel then goes through a fuel cooler. I do not know how efficient that fuel cooler is but at 35 gallons of seawater running through it at full throttle, I will guess the fuel going to the tank is not too warm.