Engine/Transmission (1994 - 1998) Low power problem still persists ...

[FATCAT]

Last time I wrote about my low power problem, I had just installed the TST fuel presure adaptor which showed my fuel presure at: 10-14 psi @ idle

20 psi @ 2000rpm

22-24 psi @ 2500rpm

from the bleader screw.



Illflem suggested that the lift-pump might be defective. I had the lift pump check out by my machnic and his fuel presure reading at the fuel pump banjo fitting read low as well.



Had the lift pump replaced (153,000 miles on the original) and gained maybe 1 psi to the numbers above, but still have that low power feeling.



The fuel filter is only a month old and the overflow valve is only about 4 months old.



One thing is that it seem my presure drops when the engine is hot (especially at idle to about 10 psi).



It just doesn't have that snap anymore ... seems that the truck revs up good, but you just don't pick up the speed (mph) that you would think. There isn't that "growle" that use to be there when I installed the turbo and injectors.



My machanic thinks I may just have a fuel volume problem and maybe need larger delivery valves?????



I do have another brand new overflow valve from Piers and am thinking of installing it this weekend, then disecting the old one, but I can't help think that maybe the P7100 is wearing out????



Does anyone make a banjo bolt that us 12 valvers can use to replace the one on the fuel pump that would have the 1/8" NTP adaptor? I just don't feel comfortable pulling the existing one and drilling/tapping it for a fitting (Murphy's law ALWAYS strikes me when ever I have to "modify" something on the truck). I would rather take fuel presure readings off the banjo bolt then the bleader screw.

 

[HoleshotHolset]

How about:



Governor lever adjustment

Rubber fuel feed/return hoses

Clogged fuel filter/strainer

AFC is getting boost - right?!

Shutdown solenoid is pulling ALL the way up - right?!



Give us your Boost #'s and EGT's - just to see if they're 'normal'.



I'd like to hear the outcome..... heck, bring it to the dyno on Saturday and we'll tune it right up.



If you want your very own banjo bolt - buy a new one as a backup and drill out your existing one. That way if you mess it up you're not dead in the water.



Matt

 

[illflem]

Don't let anyone talk you into thinking it's the injection pump. With only 10 psi the problem has to be in the fuel delivery system (or the gauge). Since you have a somewhat new overflow valve and filter other problems could be -



One of the other two filters are clogged, you have one in the fuel heater and another in the tank.



Kinked fuel line- I saw one from underneath just last weekend that was badly kinked where the rubber line connects to the steel one at the top back of the engine.



I'd also switch the overflow valve just to rule that out.

 

[A Johnson]

Time and again I have seen engines that will reach rated boost, yet they have a crack in the CAC. Symptoms are usually poor acceleration, poor economy, or just a bit sluggish type of feeling.



Just an idea.



A Johnson

 

[fox]

Have you run some Biocide to make sure the tank filter is clean?

Or remove the line at the lift pump and blow air back to the tank.

I have seen them plugged so bad one took 50 psi to move the debris. I believed it was algea, so then shocked it.

 

[FATCAT]

I can get the truck to boost up to 35psi and EGT's get up to and over 1,000 if I really throddle it.



I replaced the fuel return line about 10 months ago, and I did have a small fuel leak under the driver side where the metel line connects to the flexible line, and had that fixed.



I will try some Boicide at the next tank (thought will have to find some place that sell that stuff).



The screen at the fuel heater was cleaned out about 2 months ago when (I think) I got a bad load of fuel and had to have it towed the shop. My machanic said that the fuel just froze and he replaced the Overflow valve and cleaned the screen.



The only other thing I could think of or what the problem "feels" like sometimes is that the clutch is sliping a little (rpms increase but I don't feel I am accelerating as fast as I should have). Now I have a Con-O clutch that holds a rated 1,000lbs so I would think that that would be impossible.



Matt, where are you in Gardner Mass? I would like to take you up on the offer, though this Saturday is out since I have orders from the high-command to get the remaining 2 cords of logs cut, split, and stacked. How about on May 24th? I would like to get this "problem" solved ... though my neighbors think I'm nuts and that I am just use to the new power of the truck.



Matt, let me know.

 

[illflem]

All the biocide will do is kill the bugs, if you have them, in your tank. Their dead bodies will clog filters just as bad as live ones. If an algae bloom is indeed your problem about the only thing you can do is remove your tank and flush it or plan on changing filters frequently until they're all worked out.

 

[FATCAT]

Damm Illflem, I hope thats not the problem. That would definitely be a "dealership" trip.

 

[illflem]

Easy to tell if you have algae in the tank, just cut open a fuel filter, it looks like brown snot.

 

[FATCAT]

MPG is still good ...

One thing I know is that my fuel economy is still good. Just filled up last night 16. 88 gals. @ 335 miles = 19. 85 MPG.



Hoping to hear from HoleshotHolset about dyno work and his offer to check out my old truck.



HoleshotHolset ... you out there????

 

[98rammer]

35 pounds of boost? doesn't seem right. shouldn't you be running 38-40?

191 DVs wont do much except for more low end smoke from what i've heard.



btw, is your truck an ext. cab silver long bed?

 

[Dieseldemon]

Low Power

Check the orfice behind the AFC housing where the line from the intake goes into the afc if it is pluged it will cut your fuel on the upper end

 

[illflem]

root of the problem

You guys all have good suggestions but aren't addressing how come FATCAT's lift pump pressure is only 10-14 psi even with new parts.

 

[A Johnson]

Ok, first isn't the banjo into the P7100 inlet a 14mm? If it is you should have no problems drilling and tapping it. I've done several of the 12 mm for the VP44 and it's tight but can be done, I don't think a 14mm will be a problem. Shoot just go down and pick up a new banjo bolt before you start. If the first one taps fine, tap the next one for prefilter readings.



As far as fuel pressure goes, can you plumb in a vacumm gauge before the lift pump and check for fuel restriction? The max spec for inlet restriction is 4" of mercury by the Cummins manual. I have noticed the 24 valve engines are running around 6" restriction which is above the max spec by the Cummins manual for the ISB.



If you are holding a new overflow valve in your hands from Piers, plug it in and see what happens. There's nothing saying the recently replaced valve is not defective. Pinch off the rubber return line with a pare of pliers and see if the lift pump will raise the inlet pressure. If it doesn't then you have a problem with the lift pump or a fuel supply restriction. Also either change the filter again or take pre and post filter readings to see if it's over the 5 psi max drop.



My Cummins manual says fuel lift pump maximum output pressure is 25PSI, and it doesn't say what RPM. I have no idea what people are seeing in the real world, but from illflems' post I have to assume 12 valves are somewhat higher or at least normally higher than 10 at an idle.



A Johnson

 

[FATCAT]

98rammer - "is your truck an ext. cab silver long bed?", yup ... sure is. Its gettin a little beat up these days, starting to look its age, but the "garbage scow" is still doing prety good.



As for the banjo bolt, I think I will go get another one and do the drill and 1/8" NTP Tap. Is this a dealer item only. I don't know of any Cummins auth shops around where I work here in Littleton Mass ... or maybe I can order it online from somewhere.



Had no time this weekend to replace the Overflow valve but will have time this holiday weekend.



A Johnson ... I just don't feel comfortable cutting into the fuel lines prior to the lift pump ... the banjo bolt ideas would be the best for me now and I can pick up a second guage so as to have pre- and post- fuel pressures.



Also I'll look into the other suggestions this weekend ... man time is at such a premium for me that I only have a small window on weekends to get things done.

 

[HoleshotHolset]

FATCAT: I hope you got the PM I sent you... .



I've been off the TDR since Thursday PM... . I know - I won't let that happen again!



Matt

 

[FATCAT]

Sorry about that HoleshotHolset, from your first post it sounded like you had a shop with a dyno and all.



So when is the next dyno day in the New England area????



I think its time to stop by see what my old rattle trap can do.

 

[HoleshotHolset]

The next dyno day will probably be well after Thunder in Muncie..... it'll take some time for us all to recover from that event. :-laf



Keep us updated on your low power situation - this thread has lots of good suggestions in it.



Matt

 

[FATCAT]

And the answer is ... the overflow valve!

Well, had time this past weekend to install the new overflow valve from Piers ... this fixed my fuel pressure problem and a lot of my presieved performance loss.



Now my Fuel presure at the bleader screw is 32psi at 2500 rpm and 28-30 at 2000 rpm.



Now I need to get some more air into the engine, the Amsoil air filter just ain't gett'en it done these days.

 

[HoleshotHolset]

Cheap, quick fix... . gotta love that.



Thanks for the update...



Matt