Engine/Transmission (1994 - 1998) Power Loss

[BrentL]

1995 12 Valve has an occasion loss of power when towing at 2,500 RPM's (4. 10 ratio) for an hours time. The truck begins to miss and have no accelerator response at all. When I pull over to

the shoulder the truck will usually die. After I crank it for about 5

Seconds it will start back up and run fine with a normal accelerator.

This problem has haunted me for a couple years now. It was into the dealer at least 6 or 8 times before the warranty was out. This problem never has occurred in town, only when run for extended periods. This truck only has 51,000 miles. It has had the problem since it had around 28,000.

Any ideas would be appreciated!

 

[Joe G.]

Hard to say. Installing a fuel pressure gauge so you could see that when the problem occurred would help to solve it.

 

[Six_Man_Diesel]

I agree with Joe, sounds like not enough fuel, maybe a lift pump. I have never had a lift pump go out on my Cummins, but on my old 7. 3 phord, when the lift pump went, it went, truck wouldn't start at all. I would say check fuel pressure and go from there.

 

[scaryfast]

Like Joe said, since this has haunted you for a couple years, installing a fuel pressure gauge to see if you're getting a pressure drop when your power lose happens is the place to start.

 

[illflem]

I've had the exact same problem with my '95 2500 since it was new and have never figured it out either, but have a theory. For me it only happens when driving for three or more hours non-stop, less than half a tank of fuel and seems to always happen going uphill with no place to pull over. Had it to the dealer at least five times under warranty, they threw every fuel system part at it including a new injection pump, no luck. Unfortunately it only happens rarely and is hard to track down. Last time it happened to me it also coincided with the sender on my fuel pressure gauge being shot two years ago so that didn't help but I'm ready with a mechanical gauge next time.



Now for my theory. I think what is happening is that the fuel gets too hot from extended return though the pump after long runs and causes the spring in the overflow valve to weaken lowering the pressure. I've found that if I stop for just 10 minutes every couple of hours or keep the tank more than half full it will never do it. That's been my fix so far and if it is indeed the overflow valve causing the problem and don't see what else could be done. If you ever figure it out let me know. This question was also my very first post on TDR, in fact that's why I joined, I have never got a good answer even after asking again several times.

 

[A Johnson]

I agree with those that say to install a fuel pressure gauge. If the power problem coincides with a fuel pressure loss, you may have a restriction in your fuel syatem, possibly some foriegn material floating around in your tank that only gets on the fuel pickup screen after extended driving, and when you stop the engine or it dies the suction releases and it floats off. I see this quite often in bigger units, with bigger tank openings. A plastic pop bottle can cause all kinds of grief. Just an idea.

 

[illflem]

Wish it was as easy as a restriction for me. Dealer dropped the tank twice, pickup screen and was clean as can be both times as were the fuel heater and main filters. That was always the first place the dealers looked was for a restriction saying warranty wouldn't cover it if the filters were clogged. It would have been my first guess also.

 

[BrentL]

Bill,



I finally have a little more info to go on. I installed a fuel pressure

gauge as suggested and have been able to gather a little more

data to hopefully help diagnose the fuel related problem.



When the trucking is running okay at 2500 RPM's Fuel Pressure

is in the 32 to 34 range. When the truck has been run at, or near the 2500 RPM range for about an hour and acts up the fuel pressure increases to around 38 to 39. Also I might note that I think your onto something about the less than half tank theory. The last two times mine has acted up it was between 1/4 and 1/2 tank.

Is it possible that the warmer fuel is causing the by-pass valve

to stick? Or maybe an injector to stick closed? The increased fuel

pressure makes me think that something in the system is sticking

closed. I'm still wondering why the truck just has to die, and

then in a few seconds it will start back up and run again with a

full accelerator.



Any more ideas or suggestions? I'm thinking the by-pass valve

next!



Thanks,

Brent

 

[illflem]

Brent, I'm rather surprised the problem would crop up with higher fuel pressure, I would have thought it would be the other way around. I haven't had a problem since replacing my overflow valve but according to my fuel pressure gauge the old one was fine. I have the feeling the problem is just waiting to popup again when I least expect it.

Your normal fuel pressure is too high, it shouldn't exceed 28 psi, normal is 22-26. High pressure will cause problems. I would replace the overflow valve after first verifying that your gauge is reading correctly. Piers has the best deal going on overflow valves. http://www.piersdiesel.com

 

[SSchirmers]

I had a similar problem with my 95 it would start to miss bad after about 2 hours of driving at freeway speeds and I also had no throttle response. This engine would miss for 10 or 15 seconds then run fine for 5 or 10 seconds this would go on for 20 miles or untill pulled over then it would die. During the miss there would be no throttle response. had into dealer six times before I had them send it to cummings under warranty. The truck had 60000 miles on it and they replaced the pump and it has not happened since.





steve

 

[T. Baker]

Where did you tap your fuel gage from? I almost sounds like your problem is down line from the gauge. If you had a restriction down line from the gauge your pressuer would go up with the problem. I wan't to install a prussure gage as well.

Treven.

 

[BrentL]

The fuel pressure gauge line is attached to the top of the

fuel filter housing on the out-going side. I secured the sending unit to the fire-wall behind the hydraulic clutch reservoir. I had a

custom fuel-line built but, ended up using a 18" grease gun hose

since the custom line diameter was a little too large and bulky.

Geno's banjo bolt adapter that they advertise for the 24V fuel filter seem to work fine with the 12V also.

http://www.genosgarage.com/



The gauge I installed is the electronic Autometer. Summit Racing

had the best price I could find on the electronic gauges.

http://www.summitracing.com



Need more info let me know!

 

[GFreshour]

Some of the problems you describe (loss of power, dying then restarting) are similar to the problems I had with my fuel shut off solenoid. Easy to check, tie the fuel shut-off lever in the up (on) position, if the problem doesn't reoccur you have a starting place.

 

[BrentL]

Thanks! The very next thing I plan to do is tie up the fuel shut-off lever. I understand the selenoid tends to get weak when it gets

a little warm. Also, the fuel building up against the shut-down

flap may explain the slight increase in fuel pressure when it

acts up!

 

[jfrost]

This was very interesting to read because I just had this problem with my high mileage 1994. I went from my house in central Maine to The New England Truck Show in Boston and the darn thing crapped out on us once on the way down and about six times on the way back. It did the same thing as yours except mine made a loud knock while it was dying and then 10 or so seconds later it would come back to life with full power and no knock. I still have not found out why and it has not done it again since. Sorry i was no help, just wanted you to know you guys arent alone with this problem.

 

[illflem]

I have checked to see if the shutdown solenoid wasn't fully up when the mystery problem crops up, it was always fine. Of course by the time the engine died, I pulled over and popped the hood it could have fixed itself. I have done this without changing the key position after pulling over. Will try wiring up the solenoid next time if the problem ever appears again since once it starts dieing out it will usually continue doing so if I try to drive without adding fuel or cooling down. It does make sense if you turn the key off and restart after dieing that the initial solenoid pull up voltage may temporarily fix the problem. I've only experienced solenoids that either work or don't, never a partial failure, i. e. part open, almost seems impossible.



One thing that also makes me think that it isn't solenoid related is the solenoid isn't directly heated by the fuel. Once when my truck started acting up I pulled off the interstate, full throttle was barely above idle and crept into a gas station. While my friend continued to hold the throttle down to keep it running I added fuel, after less than five gallons was added it was running fine again and continued to do so for the next 200 miles. I hate these intermittent problems, wish it would just die once and for all so I could figure it out. Do know I'm not going to throw a new solenoid at it till I'm sure it's really the problem. It's been over two years since the last event, hard to say if it's fixed or not since adding a new overflow valve a year ago.

 

[KYOUNG]

running bad

illflem, i think you have apin hole in your fuel pickup in your fuel tank. it is a coil of tubing from top to bottom, it seems that there was a service bulletin on this problem years ago , when fuel level gets down to hole in pipe it starts sucking air. a little tip on emptying tank before working on it is pull return line at tank, start truck and fill containers. be ready because it comes out fast

 

[illflem]

KYOUNG thanks but... the dealer came up with that fix under warranty also since it's quite common due to a self tapping screw's sharp tip in the wrong place. It for sure wasn't the right fix for me since the mystery problem occurred again 600 miles down the road. My 3500 did have the pin hole problem though, the symptoms were different. Once it started sucking air and died it wouldn't start until the tank was full and the fuel system was bled all the way to the injectors. Luckily I was able to figure it out right away after my experiences with the 2500's mystery problem.

I still contend it's heat related.



The return line trick for draining the tank is great if you can keep the truck running. I use sort of the same method to drain tractor hydraulic systems, sure beats trying to squeeze a 30 gallon drain tub under the tractor. The times I've had to drain fuel tanks have been due to bad fuel plugging filters or folks filling up with gasoline. If that's the case the best way to drain the tank is to remove the fill tube from the tank to get past the rollover ball then siphon it.

 

[LarryB]

The solenoid does sound possibly suspect to me too. The heat soak in the coils could build resistance I guess. Next time it starts doing this, just turn the key to start quickly to give the solenoid a jolt on the "pull' coil possibly opening it up. The starter can handle the quick contact with the spinning flywheel as long as you do it quickly and not all the time. (My wife does this occasionally anyway. She's blond) If it starts running right again, you have your solution. If it makes no difference, I'd still try wiring it open. Problem is you never know when it is going to do it.



Just a thought.

 

[Forrest]

Pin hole? PIN HOLE!!!



Darn these guys, wish they'd get the simple things right! I changed the sending unit on my V-10 ... no fun!