Troubled new crate and turbo!

[johnsonusn]

I bought a new re-conditioned long block (from Rivera through a broker). Runs okay but when I was hauling my 10,000 lb travel trailer across country it was a horrible drive, 65 tops, 3rd gear up grades, high temps, at a best 9mpg realistically it was 6-8. I went from VA to CA along the 20 and 10, so it was the flat route. Even empty this thing seems to be a slug, and mileage is at best 9-10. Is this how these 6.5 perform stock? I expected a little better but what do I do to make this truck perform?

[Buddy]

Can you please put in a signature that says what you have and what modifications you have done to it.

We need to know what youre working with, because it sounds like you just put a diesel motor in a gasser truck and this is what you got.

What year and model, what was original motor, what size exhaust is on it, is it stock airbox?

[johnsonusn]

Didn’t want to bother you guys with all the details. This is the third motor in the truck 260k on the truck. Last motor was just enough to fire off, all the valves were ground to min specs, pre-combustion chambers not uniform pressed in, main bearings had uneven wear (I think the crank was slightly twisted if that’s even possible). I'm new to this truck, picked up and all the challenges. Due to time and shop constraints I opted for the crate motor now I wished I would have built one. Most of the truck is stock, the exhaust seems to be stock, w/ no cats.

[Buddy]

So is the shop that put it in a reputable diesel shop with 6.5L experience? This is an engine most mechanics know nothing about unless they are specifically diesel technicians AND drive some of these :) Dealerships are usually the worst. Find a shop that rebuilds the Injection Pumps (IP), has parts in stock for it like injectors, or one of the technicians drives a 6.2/6.5.

Was the IP replaced at all, is the PMD still on the IP? Could be you have a bad PMD, and you need to get a remote mount kit w/heatsink, Check out Ebay for them on the cheap with the improved D-tech type of PMD, versus the stock Stanadyne PMD. Did they tell you what TDC offset they set, should be close to -0.5, greater than -0.25, and what the set the timing as? Usually around 3.5 degrees.

You really need an aftermarket exhaust if it truly is stock. The crossover pipe stock is the worst, as in the rounded corners the dual pipe crimps inside and cuts off flow. And the factory downpipe and 2.75" pipes resitrict a lot. So if its more than 3" its not stock, but Walt at ssdieselsupply (SSDS) sells the best value exhaust system, and a crossover.

Get a boost and EGT guage before doing other great upgrades like the easiest one to get a performance ECM, SSDS sells an 80HP increase ECM, easy easy and cleanest upgrade ever.

Oh, and I have the original motor in my 94, originally used to tow horse trailer. It has great power, fast off the line like a gasser, and I get 17-22MPG unloaded.

[johnsonusn]

I did the install in my driveway, I'm a mech in the Seabees so i figured it was it something like the 6.2 in the hummers i did a little work on in the desert.

I had the dealer mech who had a 6.5 dial in the timing, he did say that my fuel rates where higher than normal. It was a while ago but i think it was about 9 when it should be @ 6-7.

IP was not replaced it does have a remote PMD and the stock one is still in there as well, I did not notice any difference in performance between them.

So I will look into those mods, PMD, exhaust, EGT gauge.

[Buddy]

Do you know if the turbo is working? You have a boost guage? If not that is a must, but I would assume you have hooked the turbo to the stock vacuum controlled wastegate controller. So make sure youre getting good boost, and if not probably that solenoid on the valve cover that controls the vacuum to it, or your vacuum pump itself can be iffy.

In MaxxTorque magazine, like their first article the debuted a stock Suburban that was just like your truck, and they detailed all the mods they did. Good reading, most of the stuff can get from SSDS. If youre towing youre going to need to upgrade the cooling, SSDS has what you need. That way you can safely run the extra power you will get from the modified ECMs.

[johnsonusn]

I don't have any aftermarket gauges, was hoping to keep this truck stock. But I can see what I have been missing will look into it. I would expect that if the turbo was not working I would have all sort of performance problems and smoke as well.

[Buddy]

sounds like youre having all kinds of performance problems, low mileage and low power, very indicative of turbo messed up.

[johnsonusn]

Yes I suppose it does sound bad. Boost pressure gauge would ansewer that but would a code be thrown first.

[Buddy]

Wouldnt necessarily get a code if your wastegate solenoid was going bad.

You should have a minimum of 15 inches of vacuum at the wastegate actuator, right by the turbo. If not check output at the vacuum pump. Should be 20"+ at the pump.

These are common failure items, and why a lot of people buy a manual spring loaded wastegate actuator and remove the vacuum pump completely. The ECM controls boost with that vacuum solenoid, and if you put a manual one on you can get more power, but it might mess with an aftermarket chip program, and fuel economy probably lower, but most people just want the power and simplicity.

Also, since you have a friend GM technician, you can just borrow a scanner and it will display boost pressure at the intake sensor. So you'd know after a quick spirited drive, where you can get it under load. Making sure you get a good 13psi or so.

You also need to replace that sleeve thing if its spitting oil out, as oil is normal, but its not supposed to come out the rubberish tube thing, and youre losing pressure then.

[johnsonusn]

Well, it's been a while since I could post anything; I got deployed for a quick trip. The week before I pulled chalks I had a massive noise appear in the vacuum pump. So two days after I got back I replaced the pump and also found a crack in vacuum hose. After I did this my mileage went up to 15mpg (but it was only over a 50 mile drive), that’s the highest mileage yet! I have not pulled with it yet to really see if there is a power increase. I just ordered a set of gauges from ssdiesel, boost and EGT. I’m hoping that will give me a lot better picture of what’s working and what’s not.

[MAGNUM SERVICES]

Buddy, how can you tell the improved d-type pmd over a stanadyne pmd ?

[johnsonusn]

Alright guys I have been lurking around the sight learning more about these motors, trying to read more and talk less. I have been doing a lot of wrenching, and upgrading. Still having trouble w/ the truck. My primary complaint is milage, I'm getting right around 12mpg around town and hauling. Don't really drive on the open road empty. My load is right around 5k and is usally up to the mountains. Next complaint.. boost pressure is maxed at 11psi with about 2psi sustained around. I'm wondering if this milage issue is one having to deal with my 4:10 gears and two with being a dually. Do they really hurt me that bad? The last problem I'm in denial about... hard starting all the time. This only happened after I installed the marine injectors. The truck always fired right up with out any smoke now when I start I always get a lot of black smoke. I'm thinking that this could be a damaged ops, maybe I broke a wire when installing the injectors.

[grancito]

I wouldn't complain about the mileage, hauling and around town. Nothing to do with the 4.1 gears.

[johnsonusn]

Intresting? I would think 12-13 mpg would be below what this truck is capable of. How do these guys get 17-18mpg? It's something to worry about, 40% better fuel mileage sure would be nice! What would you say about the hard starts anytime? The smoke?

[grancito]

I get 17 mpg highway, around town would be much less because of stop start driving of a heavy vehicle, but I do very little town driving. Hard start and black smoke on start up points to glow plugs, perhaps you moved the connectors to some when changing the injectors and they lost contact.

[johnsonusn]

Thats a good idea, I swear its the simple stuff most of the time.

[Buddy]

I do get a combined mileage of like 18mpg, and I drive pretty ridiculous, but my truck is only 6000lbs with me in it and 80 gallons of fuel. And I have smaller precups in the heads.

I got really terrible mileage when my turbo wasnt boosting correctly and I was under load blowing lots of black smoke, and over a mile high elevation to top it off.

4.10 gears around town no big deal on highway going to max efficiency around 55mph

[ZiGBlazer]

I have read a lot of posts here and it seems that the nv4500 usually gets 2-5mpg better than the auto. I've been chasing better mileage since I bought the truck. When I got it the best I saw was 11. Losing the duals and adding a topper and ssd exhaust I went up to 15mpg empty. With the rest of the mods my mileage hasn't changed. My best tank was pulling an empty car trailer, I got 18mpg.

Now pulling a 4.5k horse trailer and 6k car trailer I've been getting around 14mpg. Mine is an auto, 4x4, and 4:10s, but now 285/75R16s on aluminum wheels, instead of the 235 duals on steels. Almost 10lbs lighter per wheel, minus 2 wheels.

I've talked to a few guys and read a few posts saying the c3500 with a manual is capable of getting 21-22 constantly, with a few mods such as marine injectors, 4" exhaust, and 80hp ecm.

So if you figure out what is going on with yours let me know, I think I still have a few mpg to gain.

Good luck,

ps Forgot to add, I was getting a max of 5psi boost loaded before the chip, or if I bypassed the boost solenoid up to 18psi until it de-fueled, now it will go up to 15-16psi under full load. ECM controls it how it should be controlled now.