Generator slow to start

cardude01 · Jun 18, 2021

Lately my Maspower Yanmar-powered generator is slow to start. It used to start immediately after I pushed the button but now it takes quite a few rounds to fire up. When it’s warm this doesn’t happen.

Is it possible the “pre heater” is no longer working? How would I test that?

rgano · Jun 18, 2021

Take your IR thermometer and aim it at the point where the electrical connection to the glow plug is while somebody goes though the start procedure. If if doesn't heat up, the connection is bad or the plug is burned up. Warm engine might start with no glow plug heating; it depends on the engine.

Another thing to check is the battery to see if it has enough umph to spin the engine up to starting speed. It does not take so much juice to spin a warm engine.

Fuel leak-down is a possibility too meaning there is no fuel immediately available at start. An easy way to check is to disconnect an injector feed and hit the starter a click while watching the end of the injector line spit into a paper towel. Leak down may not have had time to occur if the engine is still warm.

STB · Jun 19, 2021

After the slow cold start, how does it run? What does the smoke look like?

Glow plugs usually are resistive heaters. If you have a DC clamp meter, you can clamp around each wire, turn on then preheat, and look for a few amps of current, either steady or pulsed, through each.

Similarly they usually have a small few ohms of resistance, which you can check after disconnecting each one. They usually fail open or crazy high resistance.

Some preheat systems, the one for Perkins 6.354s comes to mind, work very differently, e.g..as heating diesel torches vs electric heaters.

I don't know yours at all. If you post the make and model, I can look for a schematic.

cardude01 · Jun 19, 2021

This is the generator I have. The engine is the Yanmar 3TNV76.

http://marineenginestall.com/index.php?route=product/product&product_id=345

STB · Jun 20, 2021

Hey cardude01,

I didn't find much on that generator, but the service manual for the engine shows it to be a fairly typical yanmar 3cyl.

For a smownstart, the first thing qid check would be battery, and associated wires and connections. Low starting current could make a slow start.

The next thing I'd checknwould be fuel filters and valves. A fuel construction could do the same.

The next thing on my list would be glow plugs. They are resistive, according to the manual. So, they can be tested as I described above.

Next up would be the starter motor. Any electrical shop should be able to test.

Beyond that...we are in unlikely space that is likely for someone
...clogged air filter, bad tank vent, bad fuel hose, valve timing or pushrod, injectors or pump.

Happy hunting!

cardude01 · Jun 20, 2021

Thanks so much for the ideas. When I get back to the boat I will check those out. I’ve never changed the fuel filter or adjusted the valves on this generator. It has about 900 hours.

STB · Jun 20, 2021

[Hey Cardude01,

How often fuel filters need to be changed depends so much on fuel quality and age that it is hard to estimate, I think. But, at 900 hours, heck, I'd feel really good about changing them, primary and 2ndary, if so equipped. I change mine every few hundred hours or couple of years. I might be wasteful, but it brings me peace of mind.

Did the slow start creep up over time? Or start getting worse quickly once it started? Or just start happening one day?

Any observations w.r.t. smoke?

cardude01 · Jun 20, 2021

Slow start seemed to have crept up over time.

No smoke noticed.

I have a brand new start battery so don’t think that is the problem, although it does *sound* like it’s turning over slowly. I always cringe when it has to turn over so long before starting.

twistedtree · Jun 20, 2021

I'd start with the fuel filter(s). They need to be changed anyway, and could very well be the problem.

cardude01 · Jun 20, 2021

twistedtree said:
I'd start with the fuel filter(s). They need to be changed anyway, and could very well be the problem.

Will do. Thanks. I’m a little embarrassed I’ve neglected the generator. I change the oil and filter often, but that’s about it.

twistedtree · Jun 20, 2021

I think the usual guideline is to change once per year even if you haven’t reached the hours interval. I’ve let filters go 2 years, but beyond that I think you are inviting problems.

STB · Jun 20, 2021

Hey Cardude01,

Another thing I forgot to mention that I've seen do this on engines a few times and be really hard to debug....a suction leak on the fuel line. Basically, with a leak upstream of the lifter pump, where there is suction vs pressure, air could get in, but not fuel out. The result was that, as the engine cooled off, it sucked air in. Then, when starting, it needed to bleed this little bit of air before it got going, and then ran great, easily able to m manage whatever little bit got in very slowly while running.

I chased one of these for months on an engine, rebuilding the injectors and pump and replacing the lifter unnecessarily out of desperation along the way. I think I ended up finding the leak at the lifter pump.dont really remember.

I ran into a similar problem once where, when the fuel level in the tank was low, fuel could drain back into the tank putting air into the line. Fill up, let it bleed itself, and no problem.

A problem with these creep-up problems, at least in my experience, is that, as often as not, they are a bunch of things aging together vs a single thing. A little bit of fuel filters aging, a little bit of fuel aging, a little bit of electrical connections corroding, a little but of injectors varnishing and weakening, a little bit of valve timing changing, a tiny suction leak, etc, can all add up.

Often I find I start out checking that fittings are dry and tight, then foing the top one or two things on my guess list and then, if that doesn't do it, deciding it is time for a tune up, knocking out all the tuning and maintenance items. Usually then I am good.

Then, if that doesn't work, I go for the hard stuff, like looking for suction leaks or gravity back flow.

If you aren't seeing white smoke, I wouldn't bet on a drippy injector.

Happy hunting!

ofer · Jun 20, 2021

i am having this exact issue i believe. would a check valve work to prevent fuel from going back?

gkesden said:
Hey Cardude01,

Another thing I forgot to mention that I've seen do this on engines a few times and be really hard to debug....a suction leak on the fuel line. Basically, with a leak upstream of the lifter pump, where there is suction vs pressure, air could get in, but not fuel out. The result was that, as the engine cooled off, it sucked air in. Then, when starting, it needed to bleed this little bit of air before it got going, and then ran great, easily able to m manage whatever little bit got in very slowly while running.

I chased one of these for months on an engine, rebuilding the injectors and pump and replacing the lifter unnecessarily out of desperation along the way. I think I ended up finding the leak at the lifter pump.dont really remember.

I ran into a similar problem once where, when the fuel level in the tank was low, fuel could drain back into the tank putting air into the line. Fill up, let it bleed itself, and no problem.

A problem with these creep-up problems, at least in my experience, is that, as often as not, they are a bunch of things aging together vs a single thing. A little bit of fuel filters aging, a little bit of fuel aging, a little bit of electrical connections corroding, a little but of injectors varnishing and weakening, a little bit of valve timing changing, a tiny suction leak, etc, can all add up.

Often I find I start out checking that fittings are dry and tight, then foing the top one or two things on my guess list and then, if that doesn't do it, deciding it is time for a tune up, knocking out all the tuning and maintenance items. Usually then I am good.

Then, if that doesn't work, I go for the hard stuff, like looking for suction leaks or gravity back flow.

If you aren't seeing white smoke, I wouldn't bet on a drippy injector.

Happy hunting!

STB · Jun 20, 2021

ofer said:
i am having this exact issue i believe. would a check valve work to prevent fuel from going back?

A lot of tanks have a non-return/anti-siphon valve that...

(a) prevents fuel from flowing back into the tank, thereby helping to keep air out of the fuel lines, and

(b) requires a certain amount of force to overcome, even forward, such that it is easily opened by the lifter pump, but not opened by gravity. In this way, it prevents a failed fuel line from allowing a siphon to start and draining all of the fuel from the tank into the bilge.

Because gasoline vapor is explosive, these valves are, to my knowledge, required for gasoline engines/tanks.

When it comes to diesel engines/tanks, except when required by the installation to maintain the fuel system air-free, they seem to be commonly somewhat of a religious issue. Some people believe that they are useful protection from a failed line draining fuel into the bilge (and possibly bilge pumped out into the environment). And, other people think that they are a potential point of clogs and other failures, and routinely remove or defeat them.

At any rate, to answer your question, yep, they can be added. No problem. But, do check for a suction-side air leak. Often times it is the ability of the air to get into the line that enables it to displace the fuel into the tank. And, if the air leak is fixed, the fuel won't drain down. No valve needed. It all depends upon the installation. And, heck, perhaps your installation needs one, and has one -- but it failed.

Simi 60 · Jun 21, 2021

twistedtree said:
I think the usual guideline is to change once per year even if you haven’t reached the hours interval. I’ve let filters go 2 years, but beyond that I think you are inviting problems.

Racor FAQ

How do you know when it's time to change a Racor fuel filter?
As a guideline, change a fuel filter element every 500 hours, 10,000 miles, every other oil change, annually, or at first indication of power loss, whichever occurs first. Ideally, you use a vacuum gauge to monitor filter restriction, and change your filter when the gauge reads 5 to 8 inHg above the starting vacuum (about 7 to 10 inHg is typical). This insures that your filter is still removing water at high efficiency

https://www.racornews.com/racor-faq

But they have a vested interest in selling more filters

twistedtree · Jun 21, 2021

Another thought on this....

How much has the fuel level in your tank(s) changed over the time that the generator has become harder to start? I think it's common for the tank level to be above the generator when full, then the same height, then below as fuel is consumed. So the generator experiences gravity fed fuel, fuel that's easy to suck up, and eventually fuel that's hard to suck up. Perhaps this si what's exposing your problem, and might provide a guiding clue?

cardude01 · Jun 21, 2021

twistedtree said:
Another thought on this....

How much has the fuel level in your tank(s) changed over the time that the generator has become harder to start? I think it's common for the tank level to be above the generator when full, then the same height, then below as fuel is consumed. So the generator experiences gravity fed fuel, fuel that's easy to suck up, and eventually fuel that's hard to suck up. Perhaps this si what's exposing your problem, and might provide a guiding clue?

Fuel in the tank was about two years old until recently when I filled up. We have not used the boat much at all since the last time we were in the Bahamas in 2019. When I filled up recently there was a little more than 1/4 in the tank. Maybe the generator picked up some gunk in the tank?

Porgy · Jun 21, 2021

You said it sounds like it’s turning over slowly? I’d go back to the battery. Is it getting a full charge? What is its resting OCV? Did you clean, check and tighten positive and negative cables at the battery and at the gen? When you restart after it’s been warmed up, does it sound like it’s turning over faster?

Just thinking out loud but, glow plugs will suck down volts on a marginally charged battery possibly enough the starter will complain. When warm, you don’t need to preheat the glow plugs for 20 seconds to get it fired up.

MVDarlin · Jun 25, 2021

Sounds like fuel pressure bleed to me. Tighten all injectors and connections.

cardude01 · Jun 26, 2021

Thanks for all the ideas. Will check them all out when I get back to the boat.

RickyD · Jun 26, 2021

I have the same issue with my Yanmar gen engine. It started this after I changed all of the oil and fuel filters. Now it runs well but takes 6-8 seconds or so of starting to get going. I'm going to look for the suction air leak. Tanks are full and clean so no problem there. Mine has 900 hours also. It is a secondary generator that was installed with the operator side up against the bulkhead. Total extreme PITA to even check oil level. Took some effort just to find the dipstick, and much much longer to figure out how to get it back in the hole. Dropped my mirror in the process making it even harder.
Changing the oil filter was a nightmare. The PO never used it so I asked the PPO (previous, previous owner) and he said in the years he owned the boat he didn't think he ever even changed the oil. He mostly used the other genset. Ok, now I know why.

Generator slow to start

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