Tuned too conservative???

[KenDavis]

New owner of a 1994 Chev Suburban, 6.5L turbo.

1- Is it possible to have the 6.5 tuned to conservatively. No matter how hard I push it there is absolutely no smoke. Reading past posts it seems I should see some.

2- I have the 5288 fuel pump and read a past post that the computer should have been readjusted for that, how can I tell except for running good? I have learned that this engine needs to warm up about two minutes before sticking it in gear and driving off. Any sooner and the engine will stall out and die. Wandering if it might be a fuel pressure buildup problem (too slow)? I have check the fuel pump, comes on when fuse is grounded. I have bleed the air out of the filter just in case and opened the water drain. Engine stalled and died when I shut the drain off, not when I opened it.

3- I also have an intermittent stumble, hiccup or kick. I have noticed it more after coasting down a hill or freeway off ramp and then applying pedal to get back up to 65mph. Engine does not stall or shut off, just a quick stumble (one or two noticeable), then all is fine the rest of the day. I'm reading all of the past posts to check things out one by one.

Despite reading about some of the problems with this engine, so far I am loving it. Purchased it in Dec. 2005 with 199000 on the body. Past owner had a new S&S Engine put in it at 184000. It was stock when I got it. I have since put on the AFE Stage 2 intake system and Jardine's Pinnacle Power Exhaust system, turbo back, 4''. My mileage went from 15.6 mpg to 17.5 mpg with just these two improvements. I bought it to tow a 2000 Nash 26X travel trailer, 6200# empty.

This site is great. I ordered the two repair books and recieved them in two days, what service.

[JohnC]

Sounds like your fuel lift pump is not running. Do a search for "lift pump" and you'll get enough info to keep you reading for a couple of days.

[kevin77]

I have 94' suburban with the 'F' engine - and even when I was having boost problems, I never got that much smoke. I do know my lift pump is working. I do have the newer 5521 which I replaced a couple of months ago.

Could it be a timing issue?

Also, according to John Kennedy's web site - the 94's had a 5068 pump in them and there is an update prom for the 5521 - How do you tell if the prom has been updated? Could that be the problem?

Kevin

[Hubert]

I think if LP is bad then the fuel output will be less.

Any one want to comment on conservative programming.

Just from reading the page and learning my truck. The 6.5 stock settings have potential for more power with your exhaust and intake mods. Since you already have guages to monitor EGT's. The stock settings are a little conservative for flat lands but can overheat and damage the engine towing hills, heavy weight, or heavy right foot.

Low miles on engine and injectors + better breathing will give less smoke than a stock truck. Also, you may have a lower fuel calibration resistor that will somewhat limit fuel output of IP.

I'd be happy with the less smoke if I were you (heavy smoke means higher EGT's normally and not necessarily more power). If your determine you need more power the next step is a little more boost than stock, the bigger fuel output resistor (higher # resistor), reprogram, charge air cooling, then maybe propane. Its best to go in incremental build up and for longevity of engine to only push as much as you need.

[KenDavis]

Finally replaced the oil pressure switch this past Saturday. Now I can hear and feel the fuel lift pump working, must not have been earlier. Cured my hesitation problem.

Reading all the posts on the problems and following the suggestions one item at a time saved lots of time and money. Thanks fellow 6.5 owners for your info.

Newbies, like myself, read read read. Tons of info at this site.

[Mark Rinker]

Hi Ken. Welcome aboard!

I think you are correct - there simply isn't enough fuel delivered with the stock pump to overfuel (black smoke) the truck. Sounds like its time for chip and some boost increase! From there, intercooling would be your next power increasing modification - and where most stop with their quest of MORE POWER for the 6.5.

If you want to continue to push the envelope with this motor, you'll have to convert to a mechanical pump, or add a secondary fuel source like propane - in carefully metered and conservative quantities.

[moondoggie]

Good Day!

"Finally replaced the oil pressure switch... Cured my hesitation problem." Thanks for posting this information. From years of reading the Page as often as I can, I thought the only symptom you typically get from failed LP system was a miss at WOT that felt almost exactly like a gasser ignition miss. By posting your cure, LOTS of us will more quickly get to a fix, if/when the same symptoms show up.

BTW, my two 95's make gray smoke that really can only be seen in the mirror at night with headlights behind me - otherwise, I can't see any smoke. The pickup is bone-stock; the Sub only has JK's exhaust & -1.94 TDC offset.

Thanks & Blessings!

[More Power]

Any one want to comment on conservative programming.

Rush Limbaugh? :D

Jim