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introduction new to diesels

P

Plaf713

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hi everyone

making an introduction here, ive been searching on this forum for a couple months now after i purcharsed my first diesel. Its a 1994 gmc 2500 with obviously a 6.5 in it. The truck has 168000 miles on it, its a 4wd truck with the 4l80e and 3.42 gears.

A little background, when i bought the truck it ran like shit, was getting no fuel at all and the past owner had the same issue. The previous owner replaced the injection pump and a new lift pump and the truck was still starving for fuel. So after a little research I ended up replacing the lift pump, ops and the pain in the ass fuel sock. After all that the truck runs like it should.

Forward to the present, for the past week ive been driving on the highway and i go to pass someone and the truck slows down and throws a code, goes into a limp mode. I do not have a scanner but i suspect an overboosting issues since im seeing 12-13 psi when it happens. Now a few questions i have about this, from what I can see the truck is totally stock. Why would the boost be that high? and what can I do to fix it?

thanks in advance
 
Get yourself a scanner from Harbor Freight. It will pay for itself with one use. With the code, you can really narrow down the problem. Otherwise, you have all of us just guessing.

Yes, it's hard to hit 12 to 13 psi boost on a stock set-up, unless you are towing a elevations above 5,000' and still climbing and stepping on it. I'd say wastegate solenoid is sticking, but could also have a faulty intake air sensor, etc.
 
My advice would be to spend a little extra money and do the supporting mods (exhaust, intake, gauges) then purchase a tune. Tunes don't have to be all about preformance. You could get one for economy or whatever you wanted it for and most of the guys making the chips will shut off that stupid overboost/limp mode BS for you. Then you will never have to worry about it again.
 
devil I was thinking on going that route, i was actually looking at one of heaths packages i think the stage 1 performance.

big T, i saw that leroydiesel sells a program for the 94-95 odb1 setups that may be worth it. About two weeks ago i did have it on a scanner when it happened but the truck wasnt warmed up yet. Not sure if that makes a difference.

ALso am i hurting the truck being at 12 psi? I would still like to drive it but it sounds like im going to keep my foot out of the gas until I can get the issue resolved.
 
With a stock GM turbo the rule of thumb is 12-14 psi is the safe limit. I routinely pushed mine to 16 psi on some hills pulling at 70-75mph and 15 or so empty. Other than blow out the rear main she is still running strong although I am sure I did shorten her lifespan a bit as at 16psi the little gm tubo is not a happy camper. I did however have gauges and the egts never got over 950-1000 or so at that boost and engine temps were steady and never crossed 200 degrees. The egts are the biggest issue and the stock exhaust and dp will cause them to rapidly climb into the danger zone. The factory water pump and fan in 94 sucked. A tune helps, good timing, lots of fresh fuel, guages, exhaust and cooling system mods are a must.
 
i dont tow much and i dont run around in it like its a race car but since its new to me i wanted to see how much boost i could get at full throttle, sounds like ill be spending money on supporting mods. I may try the wastegate solenoid for shits and giggles.
 
Welcome to The Truck Stop!
:welcome2:These guys will help you spend your money and keep you rolling. ..

Sent from my SCH-I535
 
thanks nvw, I thought there was a way to make the ses light flash, i used to do it in my 1994 z28. And yes, that scanner seems legit. Im actually excited to order and start learning more about these 6.5s
 
Yes there is a way to read the codes with just a jumper wire or paper clip. I think walking j or leroy sells the (key) to read your codes with. Correct me if I am wrong fellows but it think it is just a jumper between A and B and turn the key to the on position.
 
The first link in post #8 is a tutorial on reading codes with a paperclip.
 
If you're looking to do mods or improvements, the cooling mods are most important.

1) '98'and later hi volume water pump with spin on fan clutch.

2) HD fan clutch. Opinions vary. Hayden? Duramax? Whatever. You'll need a spin on to go with the water pump, so do it right. Search this forum.

3) Dmax 21" fan.

Then diamond eye exhaust and mandrel bent crossover pipe. Save your catalytic converter.

Get an adjustable tune from Buddy. Send me a PM, as he's not a vendor here (long story).
 
I would personally look into a 2000 model year AC Delco model water pump. Heath use this water pump in his kit. This water pump is pricey (about $250) but supposedly balances the flow between cylinder banks. From what I understand the older water pumps at like 27-2800 rpms are only flowing like 25% or so to the passenger side of the block!

The Scantech software is great as well. Works great and allows you to do everything from code reading to diagnostics to setting the timing.

BTW welcome. This a great site. Lots of 6.5 knowledge around here.
 
Big T said:
Get an adjustable tune from Buddy. Send me a PM, as he's not a vendor here (long story).
Click to expand...

He's not a vendor here because of HIS own choices to go behind the forums back and sell after he was warned not to unless he became a vendor here. So he moved onto another forum where they don't just let him, but the mods there even pimp his stuff for free. Just a nice slap in the face of there "PAYING" vendors, and to the members.
 
I mentioned him because his adjustable tune is one of the best for these OBD I trucks. I wish that I could get an adjustable tune for my OBD II truck. Don't understand why they can't. I see Edge adjustable tuners for all the Ford Power Strokes and Chevy Durmaxes.
 
Big T said:
I mentioned him because his adjustable tune is one of the best for these OBD I trucks. I wish that I could get an adjustable tune for my OBD II truck. Don't understand why they can't. I see Edge adjustable tuners for all the Ford Power Strokes and Chevy Durmaxes.
Click to expand...

I personally don't really see a need for it. I have a DSP2, and rarely set it to the #2 tune. A properly written tune is all that is really needed. As for his being one of the best, that is a pure opinion. I have read comments from people about his tunes, and the ones that stick out to me was how his tunes would blow black when you stomped on the peddle, or how much more power it has at part throttle. That isn't the measure of how good a tune is. A "GOOD" tune is CLEAN, responsive, and has smooth linear power across the entire RPM range. I haven't driven a truck with his tunes, so I can't comment on how they drive. But based of what I have read from others with his tunes, I wouldn't call them the best(but he is pretty much the only one doing a multiple tune for the 6.5). And as to why EDGE and others have adjuteable tunes for newer trucks and not the 6.5, it boils down to how the 6.5 works. It isn't like a common rail injected diesel or an HEUI where you can fool the rail pressure or HPOP reading to give it more fuel(or easily install an expandeable memory chip like the POWERSTROKE). The 6.5 requires true multiple programs in the ECM because of how it works, and that only happens with a larger PROM chip.
 
"He's pretty much the only one making an adjustable tune"

Well there you go, thus my point/opinion of his being one of the best.

We're running his adjustable tune in Colby's '94. I'm running Heath's ATT tune in my '99. With the adjustable tune on the maximum setting, it puts out as much smoke as the Heath tune on my '99. Performance is the same. When the adjustable tune is set on economy, there's no smoke. I don't have that option with the Heath tune of anyone else's for my '99. I don't want to give up the power when I need, but I'd also like a lot less smoke and economy for when I need that. No one provides that for OBD II 6.5 trucks; Buddy is the only one who does for OBD I 6.5 trucks. You may expose Buddy for his sales antics here, but you haven't driven his tune so your input is second hand hearsay. Mine is first hand and the product is good and he happily redid it gratis when Colby swapped it from his wrecked '95 to the current '94.
 
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