Diesel Warm Start and Idle Problem - Yanmar 4JH3-TE

[donradcliffe]

Classic fuel starvation symptoms.

1. When you have the problem, unscrew the deck fill fitting. If you hear a hiss and everything works, you have a blocked tank vent.

2. If it still has a problem, buy an outboard squeeze bulb and a length of clear 3/8 in tubing.

3 Take off fuel hose at Racor inlet and put it on inlet to squeeze bulb.

4 Put clear tubing on outlet of squeeze bulb and try to pump fuel out of tank into a bucket.

5. If it doesn't pump easily, you have a blockage between the tank and the filter--maybe the pickup tube, maybe an elbow, maybe the shutoff valve. A quick fix is to blow backwards through the hose until something pops loose.

6. if it pumps easily, but you see tiny bubbles, you have an air leak.

7. Repeat the process with the squeeze bulb after the Racor outlet. I have found air leaks in spin on Racors.

8. Repeat the process with the squeeze bulb after the secondary filter. A misaligned gasket on the secondary is a classic problem. You can also pick up air leaks in the fuel pump.

9. If you haven't found anything yet, hook the squeeze bulb up before the Racor inlet and put the output on the let of the Racor after bleeding the air out with the bulb. Run the engine until the problem occurs, then use the bulb to pump fuel while you are trying to start. If it starts, it could well be a dodgy fuel pump.

[capitansurfista]

Hi, had similar problem with similar engine. Practically new enginie and when warm hot at idle will fault and stop and swichting fwd / rev a problem stalling stops etc. All fine when cold most time.
3 years like this, nobody could fix this not even "Yanmar" mechanics here in Ecuador. Luckily I found a great mechanic close by by chance and we fixed it in one hour or less. Very simple. (Everybody said inhection pump etc I di not took that advice..etc)
Ok Check your solenoid on side (Stbd) of engine by throttle rod. You will see this small solenoid and shaft (small) by or below injection pump. This solemoid works at low rpms and especially while hot bringing rpms higher so wont stall when in gear and low rpms etc. aLUBRICATE THE LITTLE SHAFT WITH ONLY SILIOCN GREASE NOT OTHER LUBRICANTS . The shaft maybe hidden by rubber dust cover. You can do quick work by using solicon lubricant on shaft and try engine....hope it works...

[hpeer]

Captainsurfista,

That little solonoid thing is most likely the wax timing advance I mentioned above. The proof is if there is a water line running to it. If no water line the disregard.

You can actually remove it and the engine will run fine, just smoke a bit in cold weather.

[capitansurfista]

YEs, I thought about it but could really understand you well. Now all fine with just lubrication on solenoid shaft. Thank you anyway.