Yanmar 4JH4-HTE - Hard to restart after 30 min

[sony2000]

After shutting down the engine, close the valve to the fuel tank. Try the restart in 30 minutes with valve closed.

[NoTies]

I would also take a look at the electrical side. Look for volatge drop across the start circuit when the engine/start is warm and compare it with voltage drop when cold.

[01kiwijohn]

Some "mechanic"!
Did you try by passing that secondary fuel filter? If Yanmar has had some concerns, and actually issued a bulletin, it would certainly be worthwhile to just by-pass it, temporarily, and see if that eliminates the problem.
If the engine usually runs properly, for extended periods, that basically eliminates any fuel supply blockage/ fuel tank vacuum/ injection pump issues so it either has to be losing its' prime or that shut off solenoid is not working as it should. Disconnect it and make sure the fuel shut off returns to the run position. The injection pump should go into "full fuel" when stationary, the governor adjust the delivery once it begins to spool up, after starting
Don't give up, its got to be something fairly basic.

[WickedG]

Yesterday I Tried the following with NO success:

- connecting jerry can directly to Fuel Injection Pump
- connecting jerry can directly to Priming Pump
- connecting tank fuel line (Racor included) directly to Injection Pump.
- priming with tank open = fuel circulation ok
- priming with tank closed = priming pump hardened
- tried with tanks fuel cups closed and open.

As per the above, I'm striking out fuel/air leaks prior to Injection Pump.

Possible "new symptom": as suggested, I used transparent hose when connecting jerry can to Injection Pump. Stopped the engine and noticed a small amount of bubbles coming out of the pump. I only experienced this once so don't know if it qualifies as symptom).

It must have been I suck my share of diesel... I now realize I missed testing Sonny2000's suggestion. It should help preventing fuel from backing up.

Originally Posted by sony2000

After shutting down the engine, close the valve to the fuel tank. Try the restart in 30 minutes with valve closed.

If injection pump goes into "full fuel" when stationary and solenoid remains open, what should prevent fuel from backing up? Why would it back up if there is no suction from tanks? Injectors are tight, no visible leaks in the engine and it shouldn't be related with the fuel return line, correct?

[01kiwijohn]

Ref your items #4 & 5; Are you talking about the fuel tank cap being on or off? If so, that's significant as it means you do have a restricted vent line preventing air from displacing the fuel being drawn from the tank. this usually also causes other performance problems though, as the engine begins "starving" when running under load, for extended periods.
- "tried with tanks fuel cups closed and open"; pls explain 'fuel cups'.
On many fuel injection pumps, the injection pump governor holds the rack in Max fuel when at rest. This ensures it gets plenty of juice at the initial start, but then the governor immediately cuts back to the rated settings once the engine spools up. The two check valves, inside the primary pump, will prevent any back flow to the tank....if they are working properly!
"new Symptom" may not be an issue as some Yanmars have the excess fuel return line Teed back into the line between priming pump and injector pump (3GM for instance). If so, it could cause a few very small bubbles to form at that point.

[WickedG]

Originally Posted by 01kiwijohn

Ref your items #4 & 5; Are you talking about the fuel tank cap being on or off?

Originally Posted by 01kiwijohn

- "tried with tanks fuel cups closed and open"; pls explain 'fuel cups'.

Yep, sorry; I meant caps not cups. Tested all with caps in place and with caps removed so as to verify if tanks where creating a vacuum. It seams they are not thus also assume tanks vents are clear.

[unclemack]

Sorry, post I just deleted was meant for somewhere else

[01kiwijohn]

OK, now take a look here;Boatinfo - Yanmar Service Manual for 3JH4E, 4JH4AE, 4JH4-TE, 4JH4-HTE
Looks like there are two governor types so you'll need to ID which one is yours.
on pg 6-25, fig 6-30 there are two little valves which could cause symptoms such as you describe. #2 is the regulator valve, controlling pressure from the feed pump (not to be confused with the priming pump. this could be stuck, or have a weak spring. #12 is the high pressure plunger and, above that you'll see #11, which is the magnetic valve, which should normally be open. This shuts off fuel to that plunger. You might be able to test that and see if it is, in fact, open and has electricity to it.
Otherwise, assuming you've checked all the fuel supply items, the intake and exhaust (including turbo) are unrestricted, it looks like a job for the injection pump shop.

[rognvald]

Originally Posted by 01kiwijohn

OK, now take a look here;Boatinfo - Yanmar Service Manual for 3JH4E, 4JH4AE, 4JH4-TE, 4JH4-HTE
Looks like there are two governor types so you'll need to ID which one is yours.
on pg 6-25, fig 6-30 there are two little valves which could cause symptoms such as you describe. #2 is the regulator valve, controlling pressure from the feed pump (not to be confused with the priming pump. this could be stuck, or have a weak spring. #12 is the high pressure plunger and, above that you'll see #11, which is the magnetic valve, which should normally be open. This shuts off fuel to that plunger. You might be able to test that and see if it is, in fact, open and has electricity to it.
Otherwise, assuming you've checked all the fuel supply items, the intake and exhaust (including turbo) are unrestricted, it looks like a job for the injection pump shop.

This was the exact problem I had with my Yanmar 3GM30F. The check valves in the injection pump were bad. Once rebuilt, problem solved--about $250.00. Good luck.

[01kiwijohn]

By the way. would you please let me know if my diagnosis is correct; I try to help as many sailors as I can so would really appreciate the feedback.
Thanks, and good luck with the repair.

[WickedG]

Originally Posted by 01kiwijohn

By the way. would you please let me know if my diagnosis is correct; I try to help as many sailors as I can so would really appreciate the feedback.
Thanks, and good luck with the repair.

Absolutely. I'll continue posting all results as I get a chance to test them.
Thank you and everyone else for your help.

[WickedG]

Thank you all for your help.
As mentioned, I'm not much of a mechanic so I ended up calling a Yanmar dealer.
Problem is now solved and my engine runs great.
Here's the technical explanation I asked them to provide me with:

Quote

We found that your Injection Pump
may have been removed, or not.
Possibly the previous attempt to
remove it was aborted due to the very
difficult accessibility.
The Injection Pump repair company
said the pump was never dissasembled
for reapir. They found the Internal Fuel
Control Lever in the pump was dragging
and not moving freely. This combined with the
engine temperature which eventually
reaches approximately 180 degrees +/-
resulted in the injector lever sticking
inside the pump and not returning to the
cold start position until the engine and
injection pump cooled down. At which
time the lever moved to the cold start
position.
This may have been a problem from when
the motor was new.

Unquote

Thanks again.

[GravityCoaches]

I know this is an old thread, but I will give it a bump just in case anyone else has this issue, and so I can add a temporary fix.

Sorry I did not see this when you originally posted it.

We had the exact same problem with the Yanmar 4JH4-HTE, also on a Cyclades 50 (Moorings 51.5). After months of chasing the issue, replacing stop solenoids, changing fuel lines, cleaning the fuel tanks, changing countless filters, pressurizing the fuel lines to check for air leaks, all to no avail, and despite assurances from many diesel mechanics that there is no way it could be the issue, we had the injector pump pulled and rebuilt in Puerto Rico. The company that rebuilt it said that it looked like it was varnished on the inside, probably from crappy fuel, and that parts were dragging because of this. The engine has run like a top ever since, It really is a great engine.

As an aside, if anyone else has this issue, the temporary fix to get it running again is to, no joke, tap on the injector pump with something solid. We would put a dowel against the injector pump just in front of the stop solenoid and then very lightly tap the dowel with a hammer, and it would start right back up.

And for all of folk suggesting air in the lines, which would be a great answer on most engines, these engines are self bleeding and do a great job dealing with a little air, just so you know.

[hpeer]

I had a different problem, would not go above 1600 in gear or in neutral. Manet pump out to repair, the report back was nothing wrong, just dirty inside.

[dbbd]

I am having the same problem with yanmar 4jh4-the

Yesterday had to drop anchor at port entrance after engine stopped (my bad) and would not start.

Seems like the thread is pointing at the injection box. Need to identify where it is