Archived Help. Truck won't idle or idles with a lope

[JGK]

My apologies, this may be a bit long, but I have a problem and I'm at a loss for a reason.



The short: Yesterday, while driving home, in traffic, the truck just lost its capability to idle. Push in the clutch, step on the brake to come to a stop and instead of the truck settling to idle at about 750 rpm, it just drops to 0 and dies. It will start right back up again, but unless you work the pedal and keep the revs up, it'll drop right off and and die.



Right after it did this the "first" time, when I started it, the pedal sort of hung up slightly, but once started, it seemed normal. Also, just after starting it, it rev'd to about 1500 and I flicked the pedal with my toe once or twice to get it to settle down. After that, that did not happen again. It just wouldn't idle. Getting home in late Friday afternoon traffic trying to keep the truck running with a 5 speed is tricky!



Here's another odd part: last evening, after it had cooled down a bit and I'd changed the fuel filter I managed to get it to run, but it idles with a long lope. It will start up (takes a few more cranks). When I let it idle, it will settle down to about 750 revs for a few seconds, then over the next few seconds it will run up to about 1100 or 1200 revs, hold for a second so, then roll back down to 750 for a second or two, then run back up to 1100/1200, then back down. It will continue to do this as long as I let it. I can run up the revs with the pedal, but when a let off, it will cycle again. Takes about 6 or 8 seconds to do one cycle. What's up with that?!



Now the history. I've had a 3K GSK in it for years. Works great. Then a few weeks ago, I removed one spring and the shims behind the big idler spring and set the retaining nut per Smokem's instructions he posted in a thread on www.competitiondiesl.com forums. My friend with '98 auto (180 pump) did the same. All has been well on both trucks. (That mod has you remove an inner spring and retain the idle spring, but remove the shims behind it. )



But twice in the last week or so my truck had died while coming to a stop in traffic. Never did that before. Thought it was just a fluke and maybe heat related (been over 100 degrees most days the last few weeks). That's why i quoted "first" above.



What I've done so far: Replaced fuel filter, checked fuel pressure with gauge at fuel inlet banjo bolt on side of pump (20 lbs at 750 revs, up to about 26/28 lbs when it cycles to 1100/1200 revs), removed AFC and plate - both looked good, checked governor spring retainers - both in place and appear to be set where I left them when I did Smokem's mods, throttle linkages seem to work OK. Governor lever seems to be OK, though I need to check where it hits the plate.



I'm thinking of reversing Smokem's mods to see what happens. The only issue there is under one idler spring there was an extra shim, but I didn't note which weight assembly it was under (one set has a number stamped on the weight. ).



Anybody got any ideas? I can be reached by cell at 208-859-9233.



Thanks,

-Jay

 

[McLaughlin]

Could you have a bad injector?

 

[JGK]

Possible. But would that cause it to behave as it is? I would think that would cause to run rough, but not just die at idle, or cycle as it does. But maybe.



I've changed the governor springs back to the original 3K GSK. Checking a few other related and unrelated items before starting it. Should do so soon.



With fingers crossed (makes it hard to turn wrenches),

-Jay

 

[Missouri Mule]

Are you getting any smoke out of the exhaust?



I don't think bad injector would cause this.



But a bad injector pump or timming can cause a surge at idle.



Taking fuel pressure "at side of pump" I take it you mean the injector pump.

20 lbs is at the minimum you can go at idle. Your fuel pump mite be going or overflow valve mite be acting up to be that low. But I don't think it would cause stalling but it mite.

Recheck linkage and low idle screw again you mite have to put the spring set up the back the way it was.



The engine speed sensor connector if dirty or broken/bent pins has been known to cause engine stalling and engine will restart after it stalls.

 

[JGK]

Smoke is normal. No excess, and none has gone away.

You are correct, the fuel pressure reading was taken at the banjo bolt on the side of the injection pump. I had drilled and tapped it to 1/8 NPT for a fuel pressure gauge in the cab a few years ago but took that out earlier this summer and put a plug in the banjo bolt. I reconnected a flex tube and put a mechanical gauge on it to check it. Prior to checking the pressure, I pinched off the return fuel line and that made no difference to how the truck idled.

I reinstalled my original GSK springs as before. After a few adjustments of the retaining nut to get the idle down, it seems to be running just fine. I worked over the AFC lever just a bit before putting it all together the last time and when I took it for a test drive last evening it runs like a rocket! Gotta turn down the AFC star wheel a bit, though - too much smoke if I'm not careful with the foot! I still need to get it down another 100 revs or so, so I'm going out to fine tune it this morning. The only other thing is, I noticed yesterday after I got it running that I've picked up a tick that I'm sure is coming from the pump. That has me a bit concerned. But lots of pumps tick.

I don't know why the new spring set up worked so well for 2 weeks and then just quit letting it idle. Something had to change.

-Jay

 

[Missouri Mule]

My pump has had a tick in twice since I've had it. I ran a cleaner/lubricant in the fuel and that stopped the tick.

 

[JGK]

Problem solved, or shifted, perhaps.



Discovered last evening while looking at the governor assembly through the torque plate hole and barring the engine over that one spring assembly is cockeyed in the hole in the weight. Also noticed a circlip is missing on that weight assembly. Fished around with a magnet and came up with a bent circlip and 2 pieces of a broken pin about 1/16 inch diameter and about an inch long.



Tick almost went away after finding those.



Now to figure out who to take the pump to.



$$ :{



-Jay