big plume of blue smoke

[dustoff]

at cold start-ups (overnight temps in the 30's... i know that is summertime to some) i get this big plume of blue smoke with or without the heater plugged in during the night... . the Cummins manual suggests it is due to , among other things i have ruled out, the pump timing out of specs and/or the valves needing adjustment..... anyone have other suggestions i should consider on the smoke issue... . i will be adjusting the valves this weekend and will have to find an authorized Bosh dealer or good diesel shop to do the pump timing... . the local cummins dealer said they would not do it if the pump had never been off the engine... thanks

 

[Steve Roseman]

Do you notice whether your grid heater kicks on or not? I don't get smoke until I'm down in the low teens or single digits.

 

[**ICEMAN**]

a bad overflow valve will produce lots of smoke on cold starts. you might want to check it if you haven't already.

 

[dustoff]

steve... . yes it smokes whether the grid heater comes on or not... and the heater does come on if i do not plug it up on some borderline mornings temp wise...



iceman... . i have not thought of the overflow valve simply because it idles great and no problems with it starting... . just smoke big time on colder morning... smokes just a tad on warm mornings...

 

[**ICEMAN**]

Originally posted by dustoff





iceman... . i have not thought of the overflow valve simply because it idles great and no problems with it starting. .

mine did too!!! spring was broke inside the valve.



is it an eye burning,very rich fuel smell type of smoke?

 

[dustoff]

iceman..... cannot say about the eye burning but it does small like good ole diesel... ... can the overflow on a 94 be replaced?... i read a thread sometime back that the 94's had a sealed unit or something like that... . thanks for the input... .

 

[Cooker]

What about a faulty fuel heater/prefilter? HemiDart reported a reduction in smoke when replacing the top O-Ring in the prefilter?



One way to rule out timing is when you start the truck cold and rev it to 1200 rpm, maybe a little more, does it run rough? If so it is likely timing.

 

[**ICEMAN**]

Originally posted by dustoff

. can the overflow on a 94 be replaced?

yes sir,,i'm pretty sure it's a one piece unit. i'm on #3 right now counting the one that came with the truck new. the last one was a revised version,, $70 i believe. do you know how to check it?

 

[dustoff]

cooker... the pre-filter/fuel heater is on the list to be checked this weekend and thank you for your response... . i remembered

reading the thread about that maybe being a cause... .



iceman... i do not know how to check it but it should be in the manual somewhere i hope... is there a simple test... . thanks...

 

[Cooker]

A fuel pressure gauge is a good way to test fuel system problems, including the overflow valve.



You can disassemble the overflow valve and measure the length of the spring, but IMO this is not a sure fire method.



Also I don't think the stock overflow valves on the 94's could be taken apart.

 

[Reddog1]

Mine always gives a black puff when starting. I wait for light to go out, slightly press pedal, and it starts on first crank. It does smoke a tad more if I do not wait for light to go out.



It is definitely not valve adjustment on mine. I adjusted the valves last week. I used a dial indicator, only had two-exhaust . 005 inch too loose, and four intakes about . 006 inch too tight. Adjusting the valves did not change anything I am aware of.



I adjusted the star about two months ago. It did create a little more smoke.



As you can see by the signature, mine is a ’96.





Wayne