Engine/Transmission (1994 - 1998) Loss of Power

[Jack fr MO]

Since installing a 250 horsepower TST kit in my 98 12 valve, I have not wanted for power, while carrying our 11 ft. slide-in camper. Last fall while returning from IN on I 44, I experienced a loss of power on hills that had never been a problem before. I noticed a loss of RPM’s and subsequently a loss of speed. The truck still ran smooth during the loss of power. Recently running empty, in cruise, I began experiencing a bucking sensation of the engine, when the cruise control opened the throttle to maintain speed. I then found by cancelling the cruise & backing off on the throttle, that the engine would run smooth but with noticeably less power. The truck would run smoothly at hwy speed until that point then the engine would just lose power. I installed a throttle position sensor August 18, 2007 @127,445 Mileage. Truck now has 139,406 miles on it.

It appears to me to be a fueling problem when the engine calls for more power at the higher speed.

So where do you all think the problem most likely lies.

I see a similar issue in a recent thread but mine is just when it's already at speed and calls for more power for a hill.

 

[JDKammin]

I would start by changing fuel filter. After that, you can test lift pump and overflow valve.

 

[CWeaver]

I expirienced the same issue this weekend pulling a jeep on a car hauler trailer (5-6000pds)it was fine at 60mph, then hit a long hill & the RPMs drop & the EGT starts climbing fast, once the engine died.

sometimes a little engine shutter. Reminds me of when my old 85' Mercedes fuel filter gets clogged. Did you confirm what the issue was????



I'll start by changing my fuel filter... . was that it? please let us know !

I was at about a quarter tank later that day & filler up as much fuel as I could. When I left the fuels stop I had to give the engine throttle to get it to start, (which I never do)Once running. . this additional fuel seemed to help the problem a lot? Filter... or lift pump maybe?

 

[CWeaver]

Update: last night I replaced the Fuel filter & took the truck out for a short drive without any load. It seems to run fine... until I really romp on it. If I accelerate hard in second and third gear (I think I'm getting more smoke than usual but maybe not) Twice after getting off the throttle hard, the engine died. This is Not normal for this truck.



Should I suspect the lift pump is bad at 161,000 miles? Is it not able to supply enough fuel perhaps? I have occationally found in the last few months that when the engine is hot & I shut down & restart, it doesn't start as quickly or fails to start until I retry again.



Any help would be greatly appreciated!



Jack fr MO: Did you get your issue resolved yet ????

 

[snappy]

Most definitely check lift pump pressure, overflow valve but I suspect that something is sticking in the injection pump. When the engine died, did it die after a hard acceleration run and the throttle was let off rather suddenly? During the time it was dead and still moving, was there more noise than usual from the injection pump? When the engine died, how did you restart it? What I mean is, did you touch the accelerator and it came back to life without using the key? On a manual trans it will come back to life, but not sure if this symptom applies to an auto trans.

I experienced a sticking injection pump on my 95 Ram. I believe that the quality of our (mine) good Canadian Co-op fuel is largely responsible. I freed up my injection pump with the liberal use of Stanadyne Lube formula.

 

[CWeaver]

When towing I didn't let the throttle off suddenly, but on my (Drag race like) test runs I did. I don't recall hereing noticable noise from the injection pump?

I have a 5 speed (NV4500), I restarted each time by stepping on the clutch putting the truck in neutral & using the starter. I haven't heard of just releasing & touching the accelerator pedal..... I assume you mean while the truck is in gear & rolling...

When a engine dies, I'm used to automaticaly taking it out of gear so it will keep rolling well.



I don't know how to (or have guage to) check fuel pressure... I was debating just replacing the transfer pump rather than taking the truck to a Cummins shop to have it diagnosed. I think the cost might be that same to just buy the pump at $100.



I could of course run some Stanadyne Lube first if I can find some.

I do wonder if the 5 gallons of biodiesel I added pre-trip was bad, but

if this is the case it should be about through the system by now.....

 

[CWeaver]

Not to loose track of the original issue, let me try to better explain:

I expirienced loosing power on hills issue this weekend pulling a trailer (6000pds). I was fine at 60mph+ on the flats, this usually happened while using Cruse Control but not always. . when I hit a long uphill grade, sometimes I'd start to slow down. . when the cruse control added more throttle, the truck would keep slowing. The RPMs would drop & my EGT would go from around 8-900 up to 1200 before I kicked it off cruse & let the truck slow.

Sometimes I felt a little engine shutter. This only seemed to happen at speed on grades & seemed to get worse as my fuel tank got emptier. If I backed off the power it seemed to run better but not great.



Around a quarter tank The engine ran rough and stalled on one of the hills, & I decided to find fuel.

After filling up, the truck ran much better but still had the issue just not as bad. Part of this was likely due to I stopped using cruse control so I could ease back on hills & not push the truck so hard. I also found the engine oil was a little over full so I removed about 20ML of amsoil... . Later that night driving through Chicago (keeping speed under 60mph) the truck ran fine accept on one steep uphill ramp...

I've changed the Fuel filter, but have not towed yet to confirm how much difference this makes. I don't think the truck is running as it should yet... . ideas?

 

[snappy]

That is exactly what I mean, seeing as you have a 5 speed. Do not use the starter, leave it in 5th and work the go peddle. Make sure the return spring(s) are in place or the throttle might stick when the engine comes back to life and it should come back to life. The signs point to something stuck in the inj pump.

The high blend of bio diesel should have helped to lube the pump. It took quite a few tanks before my stuck pump came unstuck.

 

[CWeaver]

I found out my rear gas tank strap broke & the tank was angled back... this might have been part of the issue? but... I think I was still having issues at near a full tank?

Unless the angle was streatching or pinching fuel lines somewere?



I'll repalce the tank straps & check the lines. Anyone know what side lines to the tank?

3/8 or 1/2? I'd like to replace em with parker Bio-compatable lines while I'm in there.



I still wonder if the transfer pump is right. I'm driving it to work now with a ratchet strap to hold up the tank (to use up the half tank of fuel). I'll let you know if I have issues...

... but without a load & a grade to go up going over 55mph I don't know if I can recreate the problem..... any thoughts guys?

 

[GAmes]

"I experienced a loss of power on hills that had never been a problem before. I noticed a loss of RPM’s and subsequently a loss of speed. The truck still ran smooth during the loss of power. "



I had the same problem last summer. The plunger in the fuel shut off solenoid did not go fully up so there was a limited amount of fuel available to the engine. I removed the plunger, cleaned it and the bore of the solenoid. After reassembly and installation the problem was gone.

 

[budnate]

me to last week, truck ran but would not make power one morning, found a sloppy broken plunger, truck ran great till that morning loved how well it ran.



bought a new unit from Larry B and no BS truck runs better than it ever has makes more boost, it used to stop about 32 it now burries my 35" gauge easy , truck even idles smoother.



B.

 

[CWeaver]

Thanks Guys, I'll have to check my plunger.



I was running the truck hard last night to see if I could reproduce the problem empty on hills. The truck has a little less power accoss the board but really bogs in forth gear around 18-1900 RPM. Just sort of gets stuck there. if I change gears or get beyound that point I have power again until around 2200... .



I'll check the plunger as soon as I get a chance. Is it a time consuming job to get to it & remove it? Off hand I can't picture where it is in my head.

 

[budnate]

lean in on the driver fender you cant miss it, reach down under it gently and feal the rod going into the coil gently pull towards you, I bet you will feal the rod come up some if it does and stays up, go for a drive it should run right if it does not fall back down.



I dont have any pics of one do a quick search hear there are some good pics of the valve I looked at last week when I trouble shot mine.



B.

 

[CWeaver]

Hello, I believe the problem is solved... .

First I replaced the gas tank straps and found the plastic hoses from the gas tank to the frame rail were a bit pinched and restricted. I replaced them with longer rubber lines adding length but making sure nothing was pinched putting up the tank. This helped a bit but I still felt like the truck was missing some power.....



A few months later while driving the truck a fuel leak started in the supply hose that runs next to the block to the fuel filter, etc.

(Now the whole underside of the truck is coated in diesel & thus more rust proof)

This hose is at the right rear of the block with no easy way to get tools in to fix it.



To get to it I ended up moving wiring, the filter, the brake master & booster, etc, etc.

The line was fine (had been replaced) but the clamp was a bit loose, I added a second hose clamp and tightened them both.

Since I'd spent about 5 hours removing parts to access the hose,

I decided it was time to do some other work I now had access too.



With the brakes out, I could easily reach down and put my hand on the transfer pump! ding ding ding (I've read these are a pain to replace) , etc.



So I replaced the Carter transfer pump with a Cummins pump. I also cleaned out the fuel strainer & replaced the fuel filter. As I put each component on I filled it and the line with fresh biodiesel so I wouldn't have air to purge. ( I'd read pumping the full into the lines is a twenty minute job!). I then pumped the primer about five times and tried to start the engine. The engine fired right up and ran smoothly with no more fusing with priming... .



Next I replaced my Fuel shut off solenoid with a new one.

When I removed the factory one, it fell apart (the plunger fell out of the body).

The new Woodward Solenoid from Geno's in my case required new brackets and linkage, but no fine Adjustment.



After replacing everything, The truck runs happier and the power seems to be back to normal. I have yet to tow a really heavy trailer up hill yet, but all indications seem to say the issue is resolved.



Thanks to everyone that provided advice and ideas!

 

[Jack fr MO]

well I just now came back to see what was up here and since I am Jack's wife I had forgotten all about this issue. Jack replaced the fuel filter and the problem seems to be solved.
Sorry we didn't get back on here to report my fault not his. He doesn't do the computer and unless he nags at me I forget to get on the Roundtable. Thanks for the advise it was interesting reading.