Sad Cummins Power

[backroad]

I really sorry to say that I have what I consider to be a gutless Cummins. I'm hoping that someone might have some really great suggestions of what might help. So far the best idea that I've come up with is a stick of dynomite down the turbo inlet.

I have to tell you first, to see my signiture and see what is supposedly there an what this 93 Cummins is in. It is a way large PU, with 35" duals and get 14 to 15 mpg if its lucky empty.

The injection pump appears to be indexed on the stock factory marks. I can't seem to rationalize that this would really help all that much to bump up the injection timing, but I haven't taken the time yet to really mess with anything except to make it run and drive it for the last year.

The old 460 gasser(carburated) that was in the truck would absolutely out pull the Cummins. Way too sad to think about. With about 17,000 lbs gross, the 460 would pull Sunset ( a major grade going north out of Phoenix) at 60+ in 3rd gear with the orginal C-6, and the Cummins pulls down to 45mph in 3rd also, but it's only grossing about 13,000 lbs.

I desperately need help with this THING before I take my torches to it and turn it into an overtired and oversized rock crawler to run with my Willy's.

 

[JLEONARD]

 a stick of dynomite down the turbo inlet.

Oh no. . please don't do that!!!



Specifically, what have you done to/with the injection pump? Have you made any adjustments?

We'd also like to know what you get for boost and EGT numbers.

Jay

 

[JRussell3176]

What are your max EGT's and boost?



I see you have a "+10% VE pump". Have you tried turning up the full fuel screw and tweaking the AFC a bit? Your AFC fuel pin should be on the more aggressive side and your starwheel close to bottomed. These changes should make it a whole different truck... it sure did for mine!

 

[HRDROKN]

Make sure you are getting full throttle travel



Do you have gauges????

 

[jimnance]

Your economy issues are likely due to the tires you are swinging along with the fact that it is a dually. Unless you want to go back to stock tires your economy falls into what I would consider normal given your set up. Of course, despite the numbers this has got to be much better than the 460. The 460 was never noted as being fuel efficient though pretty bullet proof.



The Cummins ought to be able to at least run with the 460. Check for induction leaks. Are you getting at least 20 PSI of boost? If you don't have guages you could have a performance robbing leak and not know it. Run some injector cleaner through the fuel to be sure the injectors are clean and happy. Also, does it feel like you get to a point and the engine falls on it's face? Could be that the fuel supply solenoid isn't opening fully. Oh, and replace the fuel filter if you haven't already. This could restrict fuel flow.



Just a few ideas to check before you start trying to turn up the power. Lets make sure the engine is running right in the first place.

 

[Buffalo]

Backroads,



At 45 mph, going up Sunset Point, is your Torque Converter in lock-up mode? That's what my '91. 5 W-250 used to do. Maximum speed going up bigger hills here in AZ was 45-47 mph ( with my 7000lb trailer). I fixed that problem with an ATS trans with Triple-Lok TC. Easily do 55 mph. plus, now. No other performance work done on engine.



I had a 21 sqcm turbo housing on the truck from the factory. What a dog!!! Installed a 16 sqcm housing & it made a huge difference. I believe you have already addressed the turbo.



I took the truck to Diesel Performance Center, 4014 W. Van Buren, in Phoenix 602-269-5043. They removed the injection pump & "recalibrated" it on a machine specific to this pump. This, also, made a HUGE difference. At least as much as what the new turbo did. Fuel mileage is the same or slightly better. With a K&N filter in the stock filter housing, I could get over 30 lbs. boost. I since got rid of the K&N & am back to a stock paper filter & the boost now maxes-out at 25 lbs. (K&N let way too much dirt in).



I think your 35's are killing your performance, also. I'm still running the 235/85/16's (stock size).



Turning up the fuel with the fuel screw made very small differences in power. Did it twice. Second time, removed part of the limiting band on the screw so that it would go in further. BTW, I do not know what a 10%-VE pump is. It could be a pump that already has all the things I previously mentioned, done to it.



The trip to Diesel Performance Center, 16 housing & the ATS trans. all made significant differences, in my truck.



Good Luck.



Joe F. (Buffalo)



Sunset Point is a pretty substantial grade. A performance shop, here in Phoenix (Chuck's Speed Center), used to use it, very early in the morning, to test performance work they had done. They now have a Mustang Dyno that can simulate steep grades.

 

[tx_fireman1525]

What gears you got in the axles?

 

[dpuckett]

What gears you got in the axles?

With only 1300lbs in the trailer, it shouldnt really matter. Sounds like a possible fuel supply issue, either to the injector pump or from it. I have yet to own a healthy Cummins that could be outdone by any near-stock V8- diesel or gas. What is your fuel pressure coming from the lift pump, out of the filter housing? Should be no less than 3psi under load. ALso check on your filter and its age an dmiles. With a lock up TC, that issue should be fine. Sounds like time to have the pump gone through and refreshed if the others check out ok. If your internal pump or advance mechanism isnt up to par, you will get poor performance, along with sucking fuel. Dont feel bad, I'm down to the mid teens myself. Pump or fuel filter.



Daniel

 

[cerberusiam]

First, loose the K&N, FAST! That is not a good filter to be running in the desert.



Second, get some gauges, Tach, boost, pyro, and fuel pressure. Get a base line for what is going on with boost and EGT's before you deep six it. There are a lot of little things you can do before looking to bigger problems but you need some way to gauge your changes.



Don't give up. I have not seen or driven a 460 that can run with a well tuned Cummins.

 

[Kiohio]

You should dispose of it properly... .

I'll give you my address!

On the seriuos side, do what everyone else said... gauges and then start tweakin on the pump.

When I first picked it up the 89 would hardly pull it's on butt around empty.

What I found:

The throttle linkage wasn't adjusted to give full throttle and the pump had NEVER been touched.

It was as stock as stock gets!

I have started playing with it a little and it has made an AMAZING difference.



KO

 

[Regcabguy]

12-valve blues

Contact Fred Swanson @ Desert Diesel Parts. He's the whiz kid! #623-910-9575.

 

[backroad]

Whew! I'm overwhelmed with questions now that I'm back in town(bagdad, Az)... ... I currently have all of the guages except for NO fuel pressure and my tack isn't mounted yet.

I get 25-25 lbs of boost, like right now and my egt runs 1200-almost 1300 degress. The pyro is pre-turbo

I'm not delusional enough to be really complaining about my fuel mileage as I undertand large/dual tires and a 3XL style truck, and I am running 4. 10 gears.

The injection pump was supposed to have been fresh just before I did my convertion and was to have been built on a +10% basis. There is no cap on the fuel screw, but also I have not messed with it either. I have this terrific fear of opening the pump for the fuel pin, starwheel etc. I definitely am getting full throttle.

I have to admit that my previous Ford 460 was positively NOT stock, but back in 93 I had a new 2wd Dodge/cummins that would blow my Fordges door off and also had a 90 2wd with the fuel screw turned in a bit that would do the same thing to my Fordge.

Transmission is very well build, with a bunch of the billet stuff inside. The 518 has been converted to a lock up converter with a HD Hughes converter. The pulling aspect doesn't seem to be affected much by the lock up converter, except for the fact that it acts similar to another gear.


It does feel like it falls on its face when pulling hills but not empty. I do get significant SMOKE when moving from a dead stop and lots and lots of black stuff when started cold.

I really will not give up as I have way too much time a energy already put into this monster.

I'm planning on upping the injection pump timing but don't really beieve this will make a big difference.

Thanx for all of your input. Keep the good stuff coming please.

 

[Steve Graham]

With 4:10 gears your under geared, that is your engine is turning to fast for decent hiway speed, 37's would be ideal. I've been putiing up with this combo for years in my Dodge, best cruise is at 55mpg.

Steve

 

[HRDROKN]

He is running 4. 10's... ...





25 to 25 pounds of boost??? So you are getting 25 then Maybe a little low?



Your boost & EGT's sound about right... I have similar mods except I have POD's and I hit 30 psi



The remaining question is fuel pressure to the pump? You are running the stock diaphram pump still?

 

[backroad]

Yes, i am still running the stock fuel pump on the side of the block. Is there a better pump available?


I'm also considering removing the duals and going to a 40-42 inch tall tire and maybe switching the gears to 4. 56's. As I said before, my fuel mileage is not my biggest concern as long as I can get somewhere in the 15mpg range, which I am. I also am considering building this THING into a 3XL rock crawler as well as a tow rig. Power is my concern. 300-325 HP is the ultimate goal. Right now, I think I'd be happy with 200...

POD's are a big thought for the future as well as the PDR HX35 turbo but I believe there is still another something here that needs to be delt with. We will figure it out.

 

[HRDROKN]

The hot first gen set up seems to be the piston lift pump. Installs in the same location and all the parts are available from Cummins... do a search and you'll find the needed part numbers.



Also I remember some numbers comparing 185's to POD's ... If I remember correctly POD's offered a bit more HP. I need to go look at that thread again myself...

 

[dpuckett]

Personally, I would skip the lower gears. In Mom's auto, it actualy GAINS momentum at the lower RPMs of each shift, then fades as the RPMs increase. You have to do some internal pump work to get it to pull hard past about 2700-2800RPM. Even though I could REACH 3400RPM in my 91, It fell off around 2900-3000, depending on its mood.



Sounds like your drivetrain is beefed up enough. If you're going to do anyting with the timing, check it right- use a gauge and find TRUE TDC before hooking it up. Timing (even a degree or two) can make a world of difference in a diesel, esp these.



I would say check fuel pressure befroe you spend $200+ on a piston LP you may or may not need. But if you have the cash on hand, it wont hurt. Just make sur eyou get the right piston style pump. Seems like the stock LP is good to 350hp or so. Basically, if your FP dips below 3psi (I think- check the book to be sure) while you are still accelerating, you need more fuel TO the injector pump.



-DP

 

[cerberusiam]

Boost and EGT's sound low, offhand I'd say you need more fuel. You should be able to make 30 psi easily and 1500 degrees with that setup.



Under a load and pulling hard I like to see a nice grey haze out the tail pipe.



What kind of smoke is it making pulling hard?



What turbo do you have?



What rpm's are you reading running at road speeds?

 

[backroad]

I don't plan on doing a gear change to 4. 56's unless I decide to up the tire size a bunch.

I don't recall seeing any haze under full pulling, just a hole lot of exhaust.

I believe the turbo is the H1C... ... the same one that came on the '93 stock.

RPM wise..... don't know... ... . still don't have the tack stuff mounted to the alternator yet.

Looks like in need to make a call to Summit and order a fuel pressure guage before I swap lift pumps.

Thanx again... ..... & I'll be back... .....

Dennis... ... .

 

[backroad]

Any further thoughts on this from anyone out there? I'm planning on tinkering a bit with it next week and really hope it's whole world opens up in black smoke.