Yanmar 4JH2E struggles to start

[JebLostInSpace]

So I'm having an intermittent issue on my Yanmar 4JH2E (55HP) (1998) when I try to start it. Sometimes, it fires right up no problem. Other times, it will crank weakly for several seconds but start. Other times, it will crank weakly and fail to start. And still other times it will fail to even turn over.

At first I thought it was temperature related, but as the problem has persisted, it has turned out not to be correlated to outside/ambient temperature.

The problem has also gotten more frequent in the past couple of weeks so that it almost never starts right away anymore, and usually takes a couple of tries.

The exception is if the engine has run in the past ~5 hours, it will almost always start back up without issue.

The weak cranking, and better performance when it had run recently made me think the starter battery wasn't getting the job done. I figured if the battery was recently charged up from running earlier in the day, it would start. But after sitting overnight with no benefit from the solar, it would struggle.

I also thought I had confirmed a battery problem when I figured out a way to get it going reliably: If I start my generator and switch on the battery charger, the engine is able to start easily every time.

Sadly, I installed a brand new battery today, and there was no change in the engine's behavior. It still struggles hard to start on its own, but it still starts easily after I run the generator.

Does anybody have a good theory that explains this behavior? It seems something must be going wrong in the starter motor, but this is not a part of the engine I've ever worked on or know much about...

Any thoughts/suggestions appreciated, and I will endeavor to provide more details if I left things out. I'm far from a diesel expert so not entirely sure what's important to mention here.

[Dsanduril]

The #1 place I see problems like this is where the negative connection from the starting battery connects to the engine block. Need to look at all the connections (presume you looked at the battery end when you replaced the battery), but the negative to the block often gets overlooked. All the starting current passes through this connection, so if is has corroded.... Especially if the problem worsens over time - corrosion never sleeps, and once started...

[jkishel]

Suggest you start by checking the battery cable connections; positive to the starter solenoid and especially negative to the engine block. Remove, clean and retighten the terminals and let us know if the problem persists. I assume the connections to the new battery are clean and tight.

[Stu Jackson]

It's a wiring issue, most likely a connection, and most likely your main engine ground.


This is a recurring issue on every single boating forum, and is not engine specific.


Good luck, and let us know if you perhaps have already done something with the wiring.

[JebLostInSpace]

Wow, 3 quick replies all suggesting the same thing. Makes me simultaneously quite hopeful this will do the trick, and foolish that I didn't manage to find this solution on my own

Very much appreciate the quick suggestions here. I'll try first thing tomorrow morning and let y'all know how it goes

[VanIslandGuy]

I have the same boat and same engine. I suggest buying a can or two of this stuff first.

Contact cleaner



The nice thing with this product is that you can use it in the plastic connecting plugs that lead to your wiring harness, sea-talk plugs, autopilot connections etc. This and a wire brush are your best friends. If there is corrosion in one place it likely has company elsewhere to surprise you later. I'd spend an hour or two and just get every single electrical contact point cleaned. Afterwards treat each connection with dielectric grease. This will serve you well for years going forward.

Also consider doing the connections behind your engine instruments, and your ignition key switch. On my boat I fixed an intermittent problem with my autopilot by cleaning the ground connection and positive electrical lead where it connects to the computer in the port stern locker in the manner described above.

These engines are self bleeding. Once started if there is a little air in the system it may chug a little for the first few seconds but it will sort itself out. Consider going through and checking/tightening each fuel hose clamp connection from the tank forward to your racor bowl, and from the racor to the engine. Also look at all the bleed points on the engine to make sure nothing is loose. It could be that a little air is entering the system somewhere, but once started it sorts itself out. This may explain why once started it is easy to restart as it was recently bled itself of air.

Finally if you've done all the above, look at your fuel filters, and make sure they aren't dirty. If they are change them of course, but also make sure that your tank isn't harbouring any of dirt/slime that could be partially blocking the pickup tube.

[CarlF]

I believe you have two problems. That’s why this is so hard to diagnose.

1. I suspect a problem with the cable or connection from the battery. The genset/charger output is going directly to the engine starter without going through the cable closest to the battery. With a multimeter, measure voltage at different points while cranking with and without the genset running. I suspect corrosion has gotten into one of the cables. Or if any of the cables attached to the battery look suspect, replace it. This fellow makes excellent custom cables for a great price https://www.genuinedealz.com/

2) I suspect you also have a small air leak in the fuel line. ‘Hard Starting” in a diesel is almost always air bubbles in the fuel. The reason it starts right away after running is there hasn’t been enough time for the air to leak back in. After five hours, the air is there. Likely candidate is the rubber gasket on a fuel filter has a nick or is twisted. Also check all fuel hoses near the clamps. Is there any cracking of the rubber? Fuel hoses over 10 years old probably should be replaced anyways.

3) Finally, until you get this fixed be careful not to flood the engine with seawater that is accumulating in the muffler while cranking. If the engine hasn’t started after 10 seconds, close the cooling water seacock until it starts. Once it starts, it blows the seawater out the exhaust.

[NYSail]

Agree with all other post regarding your negative connection. My engine looked fine e but when I took the connection apart there was significant corrosion. I added a meg buss bar to help thing stay uncrouded and clean.

Let us know

Greg

[JebLostInSpace]

Okay so I went this morning and tried cleaning up the connections. I took apart the negative lead to the engine block and found a fair bit of corrosion between the washer and the lead. So I sprayed that with some rust inhibitor, wiped it off, then sprayed with the electronic cleaner and put it back together. I also gave this treatment to a few other connections that looked slightly janky. Finally, I sprayed all the connections I could see with the electronics cleaner, but didn't take them all apart.

I started the engine and it fired right up! I was feeling great! Let it run for maybe 2 minutes, maybe a little less. Shut it down, put everything away, closed everything back up. As I was getting ready to go, I decided to fire the engine again just to celebrate and... it cranked weakly for 5 seconds and failed to start.

I was out of time by then to keep working on it, so I left it there.

I did look at the fuel lines. There is one that is maybe a little suspect. But the fact that it started easily the first time, after sitting cold overnight, makes me think air in the fuel lines is likely not the problem?

Is it possible the vibration of the engine wiggled one of the connections I worked on and messed it up?

[TheOffice]

Often there is corrosion in the wires at the panel, especially with older Yanmars. The wire from the switch to the starter is undersized, so any corrosion will lead to problems. Keep hunting. You will find a bad connector or corroded wire.

[NYSail]

My prior boat had a 1986 3hm35F. Starting issues were due to an under-sized wire harness. To check if that might be your issue go straight to the starter and jump the ignition with a screw drive..... If it is the harness or ignition wiring it will start up every time as mine did. Some replace the main wire, I just added a solenoid and that solved the issue.

With my current boat, besides the neg connection, I did have some old wires from the battery that you could see corrosion inside the wire on the wire side of the crimped connection. Made all new battery cables.


Good Luck!

Greg

[jamhass]

Don't forget to R&R the starter itself. It is grounded through its mount and corrosion there is possible.

[taylormobile]

I had similar issues with my Yanmar and Edison pedestal. Suspecting an undersized wire from the pedestal to the the starter I ran a new #8 and it did not help. Our boat had no start relay so all current used to start when from battery to pedestal and back to the starter. I added a relay at the engine near the starter and have never had an issue since (7 years)
Steve

[CaptJohn]

I had the same issue same engine 1997 model year. In my case I replaced the main engine ground cable to the battery bank to restore proper operation. The original cable had enough resistance between the conductor to the fitting to cause trouble. Nothing was visible to the eye on inspection but the replacement solved it. Good luck!

[jkishel]

If the negative cable connection to the engine block is clean and tight, the next thing to check is the positive cable connection to the starter solenoid. Make sure the battery is turned off, then remove, clean and retighten the positive connection.

From the description, there is no reason to suspect the fuel system. If the engine cranks well with the generator running, there is a bad connection which the higher voltage from the generator overcomes.

Also as noted above, the wire from the ignition switch to the solenoid is undersized and many 4JHE owners have installed an external solenoid to deal with that.