Engine falling over above 3000 RPM.

[WarWagon]

So I may have to break down and get a rebuilt 4911 pump.

This is on my 1993 parts guzzler that I just swapped IP on. The 6.2 IP did not fall over at any RPM, however, it did not start and idle well. Another 6.2 pump ran well with bad injectors giving me starting issues.

The 4911 feels stronger in the lower RPM's and I expected so with the bigger plungers. When the tach hits about 3000 RPM you can feel a power loss by the SOP meter then it shifts and has more acceleration at lower RPM.

This pump lights off immediately with 10-20 seconds of white smoke on start up - something this truck appears to have as normal.

Anything in the IP that would cause issues at higher RPM only?

Boost is limited to 14PSI and have a Walbro 5 PSI pump working well.

 

[buddy]

Probably just the pump regulating itself that way. It will be about no injection at 3500rpm. Like rev limiter. That can be adjusted, probably based on internal transfer pump pressure, which increases with RPMs. Maybe there is a screw adjustment inside the IP that will require higher pressure before cutting fuel.

 

[tanman_2006]

Mine is stock other than the fuel screw cranked and does the same thing. Powers drops quickly above 3000 and completely cuts off at ~3400, i can push that high with NV4500.

The guy at the local stanadyne shop said he adjust the rev limit to fix this but he wont touch the fuel advance or any of that (i'm not very IP literate).

 

[midniteplowboyy]

There is a 5/32" allen(same size as the stroke screw) screw in the IP fuel inlet fitting, screw the TP(transfer pressure) screw in 1/4 turn, that'll raise transfer fuel pressure(feed a little more to the plungers).

Screw the govenor spring(rear of th IP, 12oclock above the injector lines, usually has a plastic cap) all the way in. That should give you a couple hundred more rpm before it starts pulling fuel, say 2800rpm instead of 2600rpm before the govenor starts overcoming the spring. Carefull though your raising your max rpms, wont be a problem with an auto if the TCM is doing the shifting, but a five speed truck you'll have to watch the rpms. I dont recommend running them past 3k, but its nice to have it pull hard all the way up.

You only have 5psi, is that at WOT or idle? Where is this reading taking from? How old is the fuel filter housing screen, I changed mine and gained a couple psi even though the old one looked clean.

Have you tried advancing the IP some more for the start up smoke, sounds a touch retarded. See if you can get it around 6-8º BTDC @idle. When my 93 was set at 3º BTDC it would white smoke for about five seconds on a cold engine with working cold advance.

 

[WarWagon]

Can I get to the last ditch screen on the IP easy?

I was running out of power at 2100 RPM today could hardly get up to 45 MPH. It cleared up in the afternoon. Still has the loss of power over 2800. The EGT and boost indicate that I am running out of fuel, cutting the fuel back, aka plain less fuel going in.

I turned up the RPM governor some and it did raise the RPM limit 200 RPM. No difference.

Pump sat for 1 year after I blew the engine. Has 150K on it if it was the original on the GMC. It ran better before it sat.

Either the transfer pump on this is shot or there are other issues in this pump. So before I rip it out - any other ideas?

 

[buddy]

If you take the inlet fitting out, there may be a very last ditch screen there on the bottom tip of it. As well one around the outside of it. If feeding it bio maybe they got gummed up? the one around the outside I believe is incoming fuel to the transfer pump and the one on the bottom tip is from the housing where excess pressure from the plungers gets pushed back into the transfer pump. There there is the last ditch screen in the FFM if its still there. Getting the IP inlet fitting out isnt so hard, on the DS4 its two pieces, if you take out just the upper with the fuel nipple then you can get to that screw adjustment in the lower part of it.

 

[Acesneights1]

Becareful removing that cover on the back of the IP. It requires a special socket and needs to be torqued upon reinstall as it sets the preload for the transfer pump. Mine does the same thing. It's not a DS4 and does not feel like one. The DS4 definitely delivers more , but the sacrifice pays off in reliability.

 

[WarWagon]

The power falloff is beyond 'normal' as a DB2 6.2 pump does not have the same power loss curve. The RPM just about hangs after 3000 RPM WOT and then slams into a lower gear with more power. The EGT and Boost indicate loss of fuel over the 6.2 pumps.

Thanks Ace, Looks like I need to swap pumps as I do not have the tools to clean that screen properly.

Using a 6.2 pump has less throttle shaft rotation and gives me 4v at WOT vs 5v on the TPS.

 

[Acesneights1]

If you look on that cover you'll see it has a lock and it's probably sealed.

 

[WarWagon]

Found the screen in the FFM plugged solid with a yellow mass of some sort. Had to pull the screen out to see it. Much better without the plugged screen. Saved me pulling the IP again!

 

[6.2 turbo]

Tightening a DB2 nose with a open end wrench works every time for me. It simply tightens till it goes against.

 

[midniteplowboyy]

How clean is the screen in the fuel filter housing? When I replaced my filter screen I gained about 1psi, even though the old one was clean, guess maybe deposits had built up on the mesh.

Have you had the top cover off this pump? How clean is it, any rust? Sounds like my 92, it got to where it wouldn't pull. I guess it got a few batches of water over the years and caused the rack or something to stick and not go full travel, when I took it apart it was awfully rusty inside but she still ran after 18 years and 350k miles.

http://www.dieselplace.com/forum/showthread.php?t=232176 ,has a little info/pics.

The IP screen is a biatch to get to, almost an IP swap by the time you take everything off to get to it. The end cap is just snug(army manual says 30-37lbs, there usually not this tight), you can just mark where the locking tab is and tighten it back to there if you want. You dont need a special socket, a wrench will work, it has two flats on it. I'd practice on one of your bad DB2's a couple of times first, its not hard at all vertical in a vice, but horizontal on the engine, the little vane pump pieces can get out of alignment, dont force it, take the inlet housing off back off and realign the pump pieces and try again, it will thread all the way up easy when its right.

You could drill and tap one of your old IP inlet housings to 1/4" pipe and swap it over when you get it took apart and do the fuel filter to 1/4" pipe like I do mine and run 3/8" hose. That inlet housing is bad ass hard steel, so have a good bit/tap or take it to a machine shop. I dont know how much this helps, but it does some, I'd do it again. Be sure your inlet housing are the same, I saw one once that was a different depth(like 1/4" deeper), not sure if it was off a 6.2/6.5 though.
http://www.thetruckstop.us/forum/album.php?albumid=656

How much fuel pressure are you running? Where is gauged tapped into at. If you do the feed the beast mod, its easy to "T" in after the filter.

 

[WarWagon]

FFM is fuel filter housing - that is the screen that was plugged. I will have to get a new one when I drop off the injector.

Pressure is 5 PSI and down to 1PSI when I snap the throttle WOT in park. Water drain for pressure testing.

Thanks for the info on the DB2. I hope I don't have to go that far into it, in fact I would send it out for a rebuild if I do.

 

[midniteplowboyy]

You all beat me posting, I guess I had this page/tab open awhile, I do that sometimes, I'm on dial-up and I'll open a bunch of tabs so there loading while I'm reading other pages. Plus I'm a slow typing, lol.

Glad you got it figured out.

The filter water drain is pre-filter, next time you have the intake off tap in after the filter for your pressure gauge. One of the best mods I did, I payed for my gauge with filters saved.

I wonder if your sock in the tank is stopped up with that same yellow stuff. I'd think you'd have more than 5psi fuel pressure at idle.

Dont be afraid of that IP fuel inlet housing or top cover, just be clean and take your time, any deeper than that and it prolly needs to go to the pump shop.

How much adjustment is left on your governor screw? I'd go ahead and run it the rest of the way in, if your the one driving it.

I bet she'll run alot better now that she can have some fuel. Some say the DS-4 puts out more fuel, but my DS-4 with Heath chip dont, maybe up top they do since its not having to fight a governor spring. I'll keep my DB-2's.