Time for injectors, or is timing off?

[quickster]

So I think I have my 87 dialed in with the timing. I used the lumi probe with the adjustable timing light, and got the mark close to the right edge of the plate for the mag pickup. I read that timing on a 7.3 is set @2000 rpm, and the 6.9 @1400 rpm. Well I'm running a 7.3 pump on my 6.9, and I wanted to see if anyone knows if the difference in rpm's is due to more fuel being delivered. I set my truck @1400, and it sounds fine, but when taking off in drive it smokes a little. White smoke, under load. At idle you can rev it and nothing. Think I should set the timing @2000 rpm? I figured I'd ask because I'm getting tired of experimenting. Thanks in advance.

 

[quickster]

And if the timing setup is right, maybe injector time?

 

[IDIBRONCO]

I believe that people just use the 7.3 timing specs for both. I have no idea why they were supposed to be set at different RPM's.

 

[quickster]

I was thinking maybe the difference in the amount of fuel, but I don't know. White smoke= retarded timing? Not a lot, but enough that someone riding behind me will say , look at that piece of **** blowing smoke.

 

[IDIBRONCO]

I think that by 2000 RPM, the timing specs are really close to each other. I don't believe that the differences in fuel output will affect the timing. You don't have to change the timing when you turn up the fuel screw.

 

[quickster]

I'm not doing anything with the fuel screw. Just wondering if I advance the timing some more, would the smoke clear up. It's slightly advanced now. Not even a dime. But if I go more I have to loosen the lines at the pump to get it to go over more.
That's pretty much the question--if I advance the pump more, would it smoke less. Second thing would be the injectors--if they were going bad it would smoke all the time; idle, while driving, right? It just smokes some while on the pedal.

 

[Thewespaul]

Advance it some more and run some fuel cleaner

 

[quickster]

That's what I was thinking but I just needed to hear it from someone else. Plus I keep forgetting that I still have some 6 year old fuel mixed in with the new fuel and 911.

 

[riphip]

Hotshot Extreme

 

[Cubey]

That's what I was thinking but I just needed to hear it from someone else. Plus I keep forgetting that I still have some 6 year old fuel mixed in with the new fuel and 911.

My RV had weak idle when in drive with stalling at idle sometimes on the unknown age fuel it had when I got it.

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Dunno about smoke, it's almost impossible to see the tail pipe in the mirror because it's so far back.

When I mentioned it, someone here suggested maybe the IP/metering valve was going out from sitting so much.

I had to drive it 300 miles "home" and so by the time I got there, the system was cleaned up and it no longer had the problem. IP was fine, it just needed the old crappy fuel diluted with fresh a few times and a good long highway drive.

How it idles now.

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So you might just need to take it out for a good drive, using a couple tanks of fuel. A fancy cleaner might help, but it might not too.

 

[quickster]

Just an update , and still need a second opinion. I STILL can't get my truck registered and insured because nothing is open yet. But I have ran a fresh tank of fuel with some hotshot to try and clean out the injectors. I've driving it up and down my street to get it good and warm, maybe loosen the crap up. I don't know what the cetane value is- I don't have a hyrometer. But I can smell the additive. So I timed the truck again, to see if there is any difference. I used the lumi probe-it's all I have, so be it. This time compared to last time the timing was way advanced. So much that I set the pump slightly to the drivers side now with the center mark. I took it down the road and it still smokes under load. You can smell the unburnt fuel. No difference. Rebuilt pump, new lift pump. Starts right up. Time for injectors, or is there anything else to check first? And while I was just looking at the exhaust for smoke I noticed a random puff. Injector time?

 

[Philip1]

When I had issues with excessive smoke mixed with puffs of smoke I found i had a dead cylinder. It also caused the exhaust to smell like raw fuel as well. Not saying this is your issue, but it might not hurt to do a compression test on it.