I can't believe it, but for the first time ever my truck doesn't run right. It started all of a sudden, but is somewhat intermittent. When it acts up it idles very erratically, sometimes loping like a hopped up P-pump, then the idle will go way up to 2500-3000, then it might settle down and idle normally for awhile. It has a steady 15 psi of fuel pressure at all times. Driving down the road it surges and is just basically annoying to drive. If you step on it, it pulls smooth and has full power. When it idles way up it shuts off just fine with the fuel shut off (that I run manually.)

Anyone ever experienced this? I am guessing there is something wrong with the top hat spring, as I believe that is the idle buffer? It's been years since I was into a VE pump. Any input appreciated.

Thanks

 

Sounds like at times it is trying to run away. What adjustments have you made to the pump? As for the other symptoms, I'd start with pulling your fuel filter and check for contamination. Then go from there.

 

I wouldn't call it "running away", as it cuts fuel with the shut down lever just fine.

The power screw is turned in about as far as you want to go, been that way for the last 15 or so years I have had it. I haven't changed any of the pump settings in over 10 years. The problem showed up all of a sudden.

I have been just dealing with it while I get my spare parts rounded up, waiting for it to warm up a bit, and finish some of the other things I have torn apart right now. I found a spare "top hat" assembly I am going to try swapping in. I also got to thinking it could be something in the governor arm. I had forgotten how complicated that part was until digging thru my hoard of pump parts.

I really doubt it is fuel supply related. I have a big filter on the frame ahead of the factory filter, both are relatively fresh. It has plenty of fuel pressure and starts just fine. Still runs like it always did when lay into it.

 

Maybe one of the two large springs under the injection head has broken thus causing an erratic and unpredictable injection pulse? Most of the time when one breaks the other does as well causing a no run situation, but strange things can happen. I'd pull the IP and tear it apart and see what is going on inside and even if that is not your problem I'd toss in a new DGK-121 re-seal kit and put it back in. Then you'd at least eliminate that as a potential source for your engine woes.

 

Well I had a chance to tear into it this weekend, and I pulled the top cover off.

The top hat spring was intact and looked just fine. I used a syringe and removed all of the fuel out of the pump housing. The plunger return springs looked fine. Everything inside looked good. The governor arm didn't have any unusual wear or slop in it.

It has pretty much quit the high idling thing, and just cycles between a normal idle and a super low idle. As a band-aid I turned the idle up a little so it doesn't drop so low when it goes into "super low idle mode"

I took a video of it, but can't figure out how to post it on here. Here is the audio part of it: