When I come off the throttle the rpms drop below idle and it almost dies. But it catches itself and comes back up to idle. It doesn't matter if I come off easy or hard, it does the same thing. I did a search and found complaints about this happening when it's hot out, but it's not hot here yet. Also I didn't plug in the other morning and it was 40 deg out. It had a hard time starting and would barely idle. After it warmed up it was fine.

The idle problem started about 6 weeks ago. It has progressively gotten worse in the last 3 weeks. I just started running a 50/50 WMO/#2 mix 3 weeks ago. I'm wondering if that is making it worse? Or if my pump is getting worn out and it's coincidence? It runs awesome and has more power than my clutch can handle. Any thoughts?

 

I bought a spare pump from a guy about 10 days ago from a guy that was having the same problem. He changed out his pump and went on. I tore the pump down a couple of days ago and it had a plunger spring broke and the dynamic timing plunger was completely stuck. With this pump having the same problem it may be one of these two things. I'm new here and I'm just learning. So let some of the pump guys on here help you. To me it sounds like a govenor problem but I didn't find anything wrong with the governor in this pump. These guys will help you out. Good luck!

 

Try running straight diesel and see if that helps. The waste motor oil might be causing the issue.

Does the lift pump prime?

 

I resealed the pump a year ago. I replaced the two springs in the head because they were broken. Everything else looked ok, but it's got 320k on it. The lift
pump does prime. I put it on when I upgraded the fuel system 3 months ago. When I run this tank out I'm going to refill with straight #2. But the idle issue started before running the WMO. I'm think I might need to rebuild my pump anyway. Its got a lot of miles on it and the last 30k it's been cranked up.

 

Yup...Use regular diesel. Mine did the same w/ bio. ran a tank or two of regular diesel, cleared it up. 6 mo later ran a tank and a half bio, did it again.

Mine would only do it dropping from a sharp stab of the accelerator.

 

It'll take me a couple weeks to run a full tank through. In the meantime I've been trying a few things. I figured out that my intake temp switch doesn't work. I hot wired the ksb to see if it makes a difference and it still acts the same. The rpms dropping below idle happens all the time. But when the engine is cold it dies. It will start right back up again and idle. As soon as I'm on the throttle and let off it will die.

 

I finally switched over to straight #2. It's working fine now. It starts up fine when it's cold and not plugged in. And the rpms still drop a tad when I stop at a light but its hardly noticeable compared to before. So now my question is this. What is it about the WMO that is causing this? Is there something in my pump that needs to be changed to run thicker fuel? Or with 320k on it maybe it just needs rebuilt? Or maybe I'm not filtering it well enough? Thanks.

 

Stude are you processing the wvo? Or are you just filtering it? If your just filtering it it has glycerine in it that's very hygroscopic, meaning it takes water molecules out of the air. I've seen claims of pure glycerine left open for a few days draw in 20% moisture. This may be one of the problems?!?! I've read where wvo is also a great cleaner processed/unprocessed I don't know. This could be causing problems?!?! Sounds like a great idea to save a buck on fuel but also sounds like a bad idea too. Read up on the good/bad of wvo and it might tell you how to run it to save a buck and not cause problems. Good luck!!

 

He was running waste motor oil.

 

That's what I get for not reading throughly huh!! Well duh on my part!