Engine Searching on 81 SD22

[Delos]

Has anyone had experiences with the engine searching(revving up then down) on their diesel? It normally only does it when i run it on veggie oil but has recently started to do it all the time and even at high rpms. I have checked the vacuum hoses and fuel delivery. It stops revving when I partially work the fuel shut of lever on the IP. I think it is something to do with the diaphram in the IP, does anyone know about taking that apart and fixing it?

[59rollingiron]

I don't know much about diesels, I pretty much joined to learn, but I do remember a Cummins 3-cyl we have as a well pump hunting whenever we forgot to turn on the fuel line, so it was trying to suck out of a 10' hose. The vacuum in the hose was causing it to idle down, then it would idle back up as the governer kicked in (I think something along those lines). Check the filters, drain any water? The veggie oil is thicker than diesel, it carries contaminants further and is more likely to get lodged, just placing my bet that the filter(s) are catching a bunch of crap. Or maybe start it up and run it without the fuel cap on, just to see if this helps it first? (Lawn mower does this, too, for that reason, but I doubt this is the case)

[Delos]

I will make sure to drain the fuel filters next time I go out, but what I did last night was pull the 4 (8mm head) screws off the back of the diaphram on the IP. There was a bunch of brown/black goo in bottom of the cavity where the spring is. I cleaned up all that I could and put it back together without making any other adjustments. Now it starts easy and runs without revving up and down but it
1. Runs at a high rpm, wont slow down/idle unless I work the fuel stop
2. Smokes a TON
3. Throttle operates normally, other than starting from a high rpm

I think the issue now is TOO much fuel

Could this be a smoke screw issue? I have never adjusted the screw on this
Is the smoke screw the bolt on the rear bottom? A longer bolt with a lock nut, below the one for the fuel stop?

So everyone knows, this is in the 4x4 truck that I did a write-up about a few years ago, its the 83 silver king cab.
Thanks for your help!

[dn29626]

Delos

This thread reads as though you are running vo in a 81 Datsun diesel 720.

I have purchased two 82 Datsun 720 diesels recently for the same purpose.
How long have you been running vo in your Datsun?

I have been using vo in a 2001 F350 for years, so I am not new to vo.

[ecomike]

Did you ever solve your problem?

If you have the SD-22 with vacuum assisted governor, it may need a new diaphragm. There is a great thread on it if it is the same injection pump on yours.

Good write up here if this is what you have, and if it is your problem:

http://nissandiesel.dyndns.org/viewtopi ... =kiki+fuel

[Delos]

The problem was a faulty diaphragm. I got a new one from Southwest Diesel and it works good. I have been running vo for 4 years, mostly seasonally. I did run it up in Alberta this past winter and was burning vo in -20f weather so something had to be working right

[dn29626]

The problem was a faulty diaphragm. I got a new one from Southwest Diesel and it works good. I have been running vo for 4 years, mostly seasonally. I did run it up in Alberta this past winter and was burning vo in -20f weather so something had to be working right

How much vo were you running, 100%, 50% 25% ?
Is Southwest Diesel available on the web?

[kev76]

I've deen useing strait vegy oil I think I mest something up I'm new to all this so help if u can please I did go to cptc in lakewood wa but they don't teach diesel so I'm learning. My neighber is a retired diesel tech but still need more input. Thanks