Hi, all. New guy here seeking wisdom from cummins veterans:

I just bought a 93 D350 that starts instantly (regardless of temp) idles without missing a beat, has tons of low-end torque after warming up but runs horrible above idle when cold and only kind of decent when warm.

When it stutters there is a huge belch of blue smoke and back-firing. When fully warmed up it basically stops the blue smoke, but still stutters some and the max rpms is about 2200 (downhill with a tail wind).

Air filter, fuel filter, and lift pump are new. Injection pump is getting plenty of fuel (gushes out by the bucket full if the return line is removed).

Has anyone seen this before?

 

i don't now what the solution is but my truck dus the same thing but only when the wether get just worm enuff that the heaters dont turn on but if i floor it a couple time it gos a way......have wonder what the problem is also?

 

I don't now what the solution is but my truck dus the same thing but only when the wether get just warm enuff that the heaters don't turn on but if i floor it a couple time it gos a way so, it's not a big enuff probem to worry about......have wonder what the problem is also though?

 

Don't now how that happend but ooowelll

 

I will bet its a week or bad injector -s

 

Same thoughts here and the backfiring/blue smoke. Could the timing be too retarded?

2200 rpms? Check your throttle travel, make sure its hitting the stop on the pump at WOT.

 

Come to think of it, i real haven't notist the problem sence i bumped the timing up a 1/16!

 

I haven't checked the throttle linkage yet. I have heard it suggested to check the timing, but I don't know how. Anyone got a procedure and some tips on how to loosen the bolts? (maybe it's typical, but 2 of the 3 going to the gear housing seem nearly impossible)

 

Ya thay are, atlest the bottom one with out the cummin tool

most go a 1/8 but i only when a 1/16 and was vary happy with the throttle responce that it made!

 

I have a similar problem - a little blueish smoke all of the time. Injectors were replaced by the PO and are good. I already bumped the IP 1/8". Still smokes a little all the time. Should I bump the IP another 1/8"?

 

My truck would crank out blue smoke at idle... because the timing was way, WAY too high... 2.5 mm when stock is 1.25 mm. The 1/8" advance can be as high as 1.8 mm or 2 mm depending on the truck, so its very possible your timing is TOO advanced and should be retarded. When mine, with stock injectors, was set at 1.65 mm, it was TOO much! I set it to 1.4 mm and picked up 0.5 MPG.

 

how do i measure the timing? i assume that when people say advance 1/16 they mean to rotate the pumpm 1/16" from it's current spot. Right? But how do I measure what it currently is? I see that spec in terms of degrees and millimeters.

 

You can get a set of metric "S" wrenches from Harbor Freight for around $15 shipped. They make bumping the timing a lot easier.

 

basically, the problem is now solved. The timing was the culprit. I got some great advise here, and I want to thank all who helped. Here is the run-down of what went on:

gman07 suggested getting S wrenches from Harbor Freight for the purpose of loosening the pump. I did and he is absolutely correct, they make it very easy to do. (almost impossible otherwise) cost me $10 bucks in the store. I guess they're $5 more to ship.

another member offered me some tech answers regarding the pump timing (I want to offer up his name, but I don't want to get him flooded with questions if that is not his wish--I'll ask his permission first).

anyway, I bumped the pump a little at a time advancing first (which improved the condition) then retarding a little (which made it become the mobile, blue-cluod-of-stench factory) retarding made it horrible, so i continued bumping it forward until the blue smoke stopped. it ran great and the EPA took me off their most wanted list.

also, JD730 was correct that my throttle linkage was mis-adjusted. (the cheap plastic ball joint has just about had it) i took up the slack in the linkage and man does she go now!

oh, yeah-- i also steam washed the whole engine comartment first. that is well worth the effort before doing anything under the hood! (diesel scum was everywhere)

thanks again. hope my report helps someone else.

 

Can you give us a better description or part# for those wrenches? Metric/SAE? Tool collecting seems to becoming a hobby lately and I'm sure I'll need these before too long!

Tks..