Intermitent cold misfire on one cylinder

[EvergreenSD]

For what it's worth, I've experienced significant relief from these symptoms by cycling the glow plugs on the first startup of the day. I wait until the gp relay clicks off, turn the key to off then back on and start. It really seems to appreciate that little extra gp heat. The fact that I've had start-up problems in hot weather also make me think I'm getting a little air in my lines.

[philip]

For what it's worth, I've experienced significant relief from these symptoms by cycling the glow plugs on the first startup of the day. I wait until the gp relay clicks off, turn the key to off then back on and start. It really seems to appreciate that little extra gp heat. The fact that I've had start-up problems in hot weather also make me think I'm getting a little air in my lines.

When air finds its way into the injection pump, there is a reason. Once air is in the injection pump gallery, the only way out is through the injectors or to manually bleed the injection pump gallery.

I went to work on this deficiency and with some parts assistance from my local diesel shop came up with a solution that seems to have worked out well. I got the idea from examining some other brand diesels that also use the inline Bosch injetion pump.

In the meantime, when the OFV Valve fails to do it's job in one way or another, this device is how Nissan attempted to vent air in the fuel. Not real effective.

[philip]

Now that I have not been driving the Datsun so much (the Buick is much nicer ), the truck has sit for up to a week.

Well... the cold combustion rattle is back with one cylinder remaining after the coolant temp is normalized. This went on for two days. No good for me. With the engine rpm elevated to 1200 +/-, I cracked each nozzle line, hoping to find which cylinder was knocking.

#1. Drop rpm, knocking continued
#2. Drop rpm, knocking stopped
#3. Drop rpm, knocking continued
#4. Drop rpm, HARD LOUD knocking

Okay?

I let the rpm back down to normal idle and ran through the process again.

Same thing except this time #2 seemed to be spraying foam with each squirt. So I let the nut run loose for about 15 seconds and the retighten the line nut. Loosing #4 line nut seemed to spray even more foam for about 10 seconds ... then I tightened the line nut.

But now ... no more combustion knock at all.

And today ... the engine is still running fine.

[plenzen]

So! Where did the air come from? Sucking it in from around the hose on the "out" side of the filter Loose return line and when left over time sucking it in past there I had a similar type problem with my SD25 when the Racor "pre" filter was on it. ( dad installed it as a pre water trap/filter) I removed that and put on a small "in line" electric fuel pump ( 7psi max I think with full fuel bypass if not running) ahead of the filter assembly and the problem went away. I have had it on there for near a year now and it makes changing fuel filter a breeze. Just fill the filter half full of diesel, turn on the key and start the engine and wait for the stumbling to stop and the system is bled of all air. It will also tell you if you have a leak too. Perhaps the inline pump will not like this I dont know.


P

[plenzen]

Got the specs on my little inline electric fuel pump.

21.5 - 37.3 Kpa and at 400CC per minute Minimum. (approx 3.1 to 5.4 psi)

Yanmar Part # is : 119225-52102 $143.43 US as listed on Torrenson Marine Store.
http://shop.torresen.com/ships_store/in ... d&x=9&y=19

Paul