GM 6.2 Diesel DB2 questions

[bob_442]

I installed a used banks turbo setup on a GM 6.2 diesel in an '83 K30 (big truck -- 4dr, dually). Behind the engine is a TH400, an NP205, and a Gear Vendors OD. While doing the upgrade, I installed gauges...boost, pyro, and fuel pressure. I also converted to an electric fuel pump (Holley 12-428) so I could use the mechanical pump's location for oil return. I turned the fuel screw 1/4 turn as widely-suggested on the internet when installing a turbo. Originally I installed a Holley 12-427 but the pressure dropped down as low as 1.5 PSI at speed, so I upgraded. It still drops as low as 3 PSI at speed. With the fuel pump running and the engine stopped, I get a little over 6 PSI of fuel pressure behind the IP. Both fuel filters are new.

I'm not getting the power I was expecting. At very high RPMs, I can get 9 PSI of boost, and about 900 degrees on the pyro (mounted in the exhaust manifold, pre-turbo). It feels to me like it's either not getting enough fuel or it needs the timing advanced. I checked and the pump is turned up against the stops towards the driver's side. If I send straight 12 volts to the cold start advance solenoid, the truck feels like it has a little more pep in its step taking off from a stop light, etc. Not a whole lot of difference at WOT that I can tell. Maybe a few extra degrees on the pyro. I haven't side hide nor hair of any black smoke since installing the turbo. I'm still working on the exhaust system. Currently the down-pipe dumps right below the frame right beside the transmission ear. Yep, it's a little loud. I had to delete the mechanical vacuum pump to make room for the turbo. A cam gear driven one doesn't fit because it interferes with the secondary fuel filter. I'm currently running a $9 aquarium vacuum pump just to keep the modulator, the heater/AC, and the cruise control working while I'm waiting for parts to come in for something a little more beefy.

Does it sound like my IP needs rebuilding/replacing? Is there anything I can adjust on the IP relating to fuel pressure (and thus timing)? Or anything else?

Bob

 

[Clb]

Lots of ip and turbo threads on here but to start with...
Db2 lifespans are usually agreed upon as being 100-125k.
Same for injectors.
Pump turned against the stops says either it's installed wrong or it's shot.
9 psi @900 deg egt is plenty safe for a 7.3, gm built 6.2 grenade I got nothing.
But you will find e pump threads galore and today ' it's not looking good.
Keeping the delivery psi, at the max torque and hp points is a big deal.
The max psi is open to determination, I haven't seen the max egt specific to the 6.2 tho...
Keep stirring the pot here...
Some one is going to come along...

 

[bob_442]

Other than turning up the fuel screw, I didn't touch the pump or injectors as part of the upgrade (I did replace all the glow plugs -- they were shot). So the pump was already advanced all the way. I *thought* it was operating OK, and that the anemic power was just the nature of a NA 6.2. Now I'm starting to wonder if it was actually more anemic than it was supposed to be. Back in the day, this pump did see a bit of filtered, but not 'fuged, WMO mixed with diesel.

I have read that if the feed pressure is a little on the high side, it has the effect of advancing the timing a bit -- similar to applying 12V to the advance solenoid. If the pump is a little long in the tooth, having (a little) higher pressure might nurse it along for a while. I'm wondering if there is anything I can easily do to the DB2 short of pulling it to increase the pressure. I can replace the (lift) fuel pump of course, but that will have diminishing returns if the feed pressure is being regulated within the DB2.

If I have to replace the DB2, I will, but I'd prefer to get caught up on other neglected vehicle projects first.

 

[DaveBen]

Do you have a few years to listen to what "WE" say?

 

[bob_442]

Of course. At least I hope so. But I must confess, I'm not sure I understood your reply.

 

[Clb]

You will find a plethora of information about your querry here, the search button is not perfect, but it's probably faster than waiting for the response you need from someone who has seen the same question posed repeatedly, fo grins' punch in
Facet, for the best meme EVAR!

 

[bob_442]

Got it'. I did in fact do a little searching. I found the posting regarding tweaking (drilling out) the fuel return regulator interesting. About 12-13 years ago, my 1981 Olds 98 with the highly desirable 5.7 Diesel, which I still have BTW, stranded me because of a pump failure (also a DB2). Apparently they were outfitted with a crappy o-ring inside which broke down over time and ended up getting little bits spewed all over the inside of the pump. These would plug up that regulator and high pressure inside the db2 would shut down fuel delivery. The get-my-butt-home solution was to carry a drilled out fuel return fitting in the glovebox and to swap it in, to allow the little bits back through the fuel return line, and to relieve the excess pressure in the IP. Unfortunately I didn't know about this in time to save a tow bill. But I did test the theory in my shop before pulling the IP. It did work. I still have the drilled-out fitting in the glovebox. The more I read, the more I think I do need to pull my IP. Very tempting to procure and install a rebuilt 4911 variant of the pump in the 6.2.

 

[Black dawg]

Just turn the pump up more. Egt is still low, and boost will increase as well.

The banks 6.2s and 6.5s that I have had never made much more than 10 to 12psi.
These dont require much fuel psi, and if you have a few psi at wot max load, it should be fine.

 

[bob_442]

Two questions. First, the fuel screw got very hard to turn towards the end. Is that normal? Second, if I turn the fuel up more, am I still wasting it by dumping it into the cylinder too late?

Bob

 

[Black dawg]

If the screw got hard to turn, it is probably bottomed out.
turning up these pumps just moves the limit to how far the plungers can move out. If I remember correctly, this actually moves the start of injection up, because the roller starts up the ramp of the cam ring sooner.

 

[Smitty 90idi]

Did you time the pump? Injection pumps do not need psi they need volume. 4-6 at idle is fine and 1-0 at speed is fine. 9spi at 900 seams away off to me. I have an 84 suburban with a banks 6.2 and a 89 k2500 with a 6.5 and banks. We only run 10 on the 6.2 and 12 on the 6.5 but very rarely see 900deg unless we are towing or going uphill too fast.

 

[Smitty 90idi]

Did you time the pump? Injection pumps do not need psi they need volume. 4-6 at idle is fine and 1-0 at speed is fine. 9spi at 900 seams away off to me. I have an 84 suburban with a banks 6.2 and a 89 k2500 with a 6.5 and banks. We only run 10 on the 6.2 and 12 on the 6.5 but very rarely see 900deg unless we are towing or going uphill too fast. I have fuel pressure gauges on everything I own and I never see 4,5,6 at higher rpm’s not on ford idis or the old chevys.

 

[Black dawg]

Correct that the injection pump doesnt need a specific psi, and that enough volume is all that matters. But since we cant measure volume easily, maintaining a couple psi under heavy fuel usage lets us know that there is enough volume.
All of the idi stuff that I have had, with the old lift pumps, not the crap we have now, would maintain atleast 1psi even towing heavy. These new lift pumps and the cheap electric pumps have a hard time keeping up towing if you drive 60 mph or more.

 

[Smitty 90idi]

well I see 0 on my fuel pressure gauge every day on all my diesels and never had a problem with the stock mechanical pump. They usually out out a lot of volume. As for the E pumps I see. Nothing but problems. Not to mention you would need an inertia switch so that if you wreck it turns off your pump. All of these injection pumps should never have more then 7-9 max psi input before they get ruined. It also messes with your timing. I also never tow over 55 or drive empty over 65. It’s the law and these trucks were never meant to do that. I’ve seen too much loss of life due to driving to fast with a trailer.

 

[Black dawg]

well I see 0 on my fuel pressure gauge every day on all my diesels and never had a problem with the stock mechanical pump. They usually out out a lot of volume. As for the E pumps I see. Nothing but problems. Not to mention you would need an inertia switch so that if you wreck it turns off your pump. All of these injection pumps should never have more then 7-9 max psi input before they get ruined. It also messes with your timing. I also never tow over 55 or drive empty over 65. It’s the law and these trucks were never meant to do that. I’ve seen too much loss of life due to driving to fast with a trailer.

Lol. I knew that would lure you out........