Dave Whipple

My 12 valve 91.5 will not idle until it warms up? It's like hitting a switch! VE pump.... I've replaced all sensors, new fuel pump stock , New filter, Delete fuel heater . Just stumbles like a timing issue , but I hold it above idle for 15 minutes and boom...... runs fine idles perfect! Anyone ever seen this?

BHD

Does it idle rough or not at all? White or gray smoke out the tailpipe?

thrashingcows

Grid heater and KSB working properly? Does it seems like a miss fire or as BHD mentioned is there any smoke out the tail pipe?

u2slow

KSB seems more likely... I run without grids, and i can idle nicely long before 15mins are up, even when its below freezing.

If its only happening when its quite cold out, the deleted fuel heater may not be helping.

BHD

The '91.5 engine in my '74 W200 doesn't have the KSB or the grid hooked up and is quite angry under 35 degrees F. But, it starts and idles like any other cold mechanical pump diesel. Once it warms up a little its good to go all day.

u2slow

Idle could be borderline low too.

Dave Whipple

Black smoke , but starts right up....just rough running will not idle until it warms up... I'm thinking could be that regulator valve I guess it governs the pressure in the pump it has a spring inside of the nut I seen it on some other videos?

Dave Whipple

Forgive forgive me I'm trying to figure out this thread but it will not idle at all until it's warm, I would say black smoke but not heavy I responded but I don't know if it was in the right area

Dave Whipple

No no misfire it just will not idle seems like the timings off and I must keep it above idle with my foot until it warms up then it runs fine , Yes grid heater and ksb works fine?

thrashingcows

Do you know what your idle is set at? Regulator valve...are you referring to the KSB? Also does your motor have an ECM, Is it intercooled or Non-IC?

Dave Whipple

Yes, it's intercooled... This valve is next to the inlet pipe closest to the head, I am away from home but when I get back I'll pull that valve.... It supposedly controls the pressure in the pump and is connected somehow through the body to the ksb? Don't know about ECM, it's got me stumped! Starts and idles perfect when warm? So how could the idle be off?

BHD

Does it idle the same way if you plug in the block heater until the upper hose gets warm?

thrub

Could maybe be that pressure control valve on the front of the pump. I had one come apart before. My truck produced lots of white smoke and didn't run well at all. If I recall it did run a bit better once it was warmed up.

Dave Whipple

Good idea, I will try plugging in the water heater also.....

Dave Whipple

Yes, I will pull this valve also, from what I've seen on some videos this valve has a spring inside that gets stuck..... hopefully this is it...