Smoke at Idle

[Greenvans]

Hey Guys,

I'm getting excessive smoking from the tailpipe whenever the van is stopped and running. Still doing it after an oil change, and it's slightly worse when it's running on veggie. It's not so bad when I'm idling on diesel, but still noticeable. The van is a 99 7.3L with about 120000 on it. No mods, just the V3.
Any suggestions on what this could be?

Thanks!

-Andy R

[Marv]

Hard to say why it's smoking at idle when on diesel - I would suppose it could be a number of things. Can you give us a bit of history on the van/engine?

Smoke at idle is common when running vegi...and will increase slightly as you idle. Once you step on the go pedal, it'll belch out a nice cloud and then you basically don't notice it while running down the road. At least on a stock tune that is.

[Greenvans]

Yeah, I'm thinking it's all veggie related, maybe only partially burned fuel?
I bought the van at 85,000 in april and put in the V3 immediately. It's at 140,000 now, started noticing the smoke around 125,000. I have changed the oil regularly every 3k, did a diesel filter at 100,000, did a dealer service (ouch) shortly after I bought it. No engine work, just brakes, ball joints, coolant flush, etc. all in all it's in great shape.
I do, however, have to change the donaldson every 2k or so. I know a lot of people talk about getting 5k on those, but I don't ever have a consistent type of oil. I'm always touring around the country getting different types from different people with different filtering methods. Would the oil quality be causing the problem?

-Andy

[Marv]

Yeah, I'm thinking it's all veggie related, maybe only partially burned fuel?
I bought the van at 85,000 in april and put in the V3 immediately. It's at 140,000 now, started noticing the smoke around 125,000. I have changed the oil regularly every 3k, did a diesel filter at 100,000, did a dealer service (ouch) shortly after I bought it. No engine work, just brakes, ball joints, coolant flush, etc. all in all it's in great shape.
I do, however, have to change the donaldson every 2k or so. I know a lot of people talk about getting 5k on those, but I don't ever have a consistent type of oil. I'm always touring around the country getting different types from different people with different filtering methods. Would the oil quality be causing the problem?

-Andy

Sounds like the vegi is contributing to what you're seeing, however I suppose it's possible the engine is maybe just starting to show it's age. Sounds like you've done a great job with servicing it since you bought it, but I'd be interested in trying to find out what was done to it prior to you purchasing it.

If it was taken care of early in it's life, I probably wouldn't worry too much. I'm not real familiar with the 7.3's, but I wouldn't think 140K miles shouldn't be a problem for them. From what I gather, it's one of the strongest running engines Ford ever sold.

Have you talked to any other 7.3 owners to see if it's a common characteristic for them to smoke a bit more as they get older? I suppose variations in fuel (both vegi and #2) could affect this as well.

Good luck! :cheers:

[greasedltn]

I bought my 7.3 at 72k and now have 160k. I have also noticed slightly more smoke at idle, but everyone I've talked to said it's not a problem. From what everyone said, it's just starting to show it's age.

[Marv]

I bought my 7.3 at 72k and now have 160k. I have also noticed slightly more smoke at idle, but everyone I've talked to said it's not a problem. From what everyone said, it's just starting to show it's age.

Sounds like a common trait then...hmm. Interesting...I don't know that I'd sweat it much Andy.

[triplemoutdoors]

Smoke at idle is common when running vegi...and will increase slightly as you idle. Once you step on the go pedal, it'll belch out a nice cloud and then you basically don't notice it while running down the road. At least on a stock tune that is.

Marv
I have seen posts all the time that say their truck somkes a little more on vegi. My 2000 7.3 with 183,000 miles on it does not smoke at all. As a matter of fact it smoked more on diesel and I can't get it to smoke on vegi. I don't mind it just seems a little odd.

[Marv]

Marv
I have seen posts all the time that say their truck somkes a little more on vegi. My 2000 7.3 with 183,000 miles on it does not smoke at all. As a matter of fact it smoked more on diesel and I can't get it to smoke on vegi. I don't mind it just seems a little odd.

Hmm interesting. Like you said, most everything I've heard (and seen with my truck) is that vegi will result in some smoke.

Maybe your truck is just a little more "green" than ours. Not only does it run vegetable oil, but it doesn't smoke either! LOL...

[skyskijason]

I believe the problem is low combustion chamber temps at idle. I see EGT's as low as 200* after just a couple min's at idle!! I NEVER idle more than a red lite on VO. I've experienced significantly lower VO temps at idle and even no-load, low speed around-town type driving, VO temps falling as much as 50-60* when its cold outside!! After adding aux coolant pump this is greatly reduced - but I still do not idle on VO. These engines burn like 1/2 gal/hr at idle - I can afford the diesel.

Anybody here measuring fuel temp before the heads?

[Marv]

I believe the problem is low combustion chamber temps at idle. I see EGT's as low as 200* after just a couple min's at idle!! I NEVER idle more than a red lite on VO. I've experienced significantly lower VO temps at idle and even no-load, low speed around-town type driving, VO temps falling as much as 50-60* when its cold outside!! After adding aux coolant pump this is greatly reduced - but I still do not idle on VO. These engines burn like 1/2 gal/hr at idle - I can afford the diesel.

Anybody here measuring fuel temp before the heads?

That thought never crossed my mind, but it very well could be the cause. Lower temps = better chance of unburned fuel making it's way through the system.

Jason, how did the aux coolant pump help? Does this increase the flow of hot coolant back to the tank and vegi lines, thereby increasing the heat transfered to the oil? Or am I misunderstanding your setup?

Thanks!

[Marv]

Anybody here measuring fuel temp before the heads?

Forgot to comment on this...haven't seen anyone doing that, but I'd sure like to figure out how!!

[Clay]

white smoke means unburned fuek at low temps. Black smoke is unburnt fuel at high temps.

Also could be a valve issue. Maybe your valves need checked.

[skyskijason]

That thought never crossed my mind, but it very well could be the cause. Lower temps = better chance of unburned fuel making it's way through the system.

Jason, how did the aux coolant pump help? Does this increase the flow of hot coolant back to the tank and vegi lines, thereby increasing the heat transfered to the oil? Or am I misunderstanding your setup?

Thanks!

Yep, the coolant pump forces flow thru the VO coolant loop. The issue is low flow thru coolant loop at low rpm's combined w/lower coolant temps from no load on engine. Soon, I will add a temp sender to coolant return line and I can report exactly how much pump helps. Btw, it has virtually no restriction when off...

I measure VO temp via a tee in VO line right where it exits FPHE, easy as pie!

[Marv]

white smoke means unburned fuek at low temps.

That would explain the white smoke at idle then when using vegi...

[Marv]

Yep, the coolant pump forces flow thru the VO coolant loop. The issue is low flow thru coolant loop at low rpm's combined w/lower coolant temps from no load on engine. Soon, I will add a temp sender to coolant return line and I can report exactly how much pump helps. Btw, it has virtually no restriction when off...

I measure VO temp via a tee in VO line right where it exits FPHE, easy as pie!

Sounds like a good setup Jason. What brand and model did you go with on the aux coolant pump?

FPHE? I'm stumped on that one. I've seen the acronym before, but can't remember what it is.