kpracing

Ok look @ my earlier post about my truck cutting out/ loosing power.
https://www.dieseltruckresource.com/...ad.php?t=89738

Today I was @ a rest stop; truck had been driving good for the last month or so.
I had the supply pump changed and gauges installed a wile back.
When I went to take of from about 20 min stop the truck would do the same as it have done before.
It will idle but rough and kind of rolling up and down.
Hit the gas the truck dies. My fuel pressure did never go under 9psi in idle
But is going up and down when doing this.
I started the truck 2 times and it would still do it, let it sit for 1 min started it and it was gone.
But now my fuel pressure is rolling up and down and much higher than before.
On the FW @ 75 with 10 psi on the turbo my pressure is now 21-23 psi.
Before it was about 19 psi.
Also the gas pedal is really hard to press down right after I let it sit after it has been acting up.
The truck is driving fine again now. But I need to find out what is going on.
Any ideas?
Also the turbo gauge would go up to 32psi I have never seen it over 29 before.
EGT is 700 driving down the FW.
This is driving me crazy I need to pull my trailer soon but I don’t want to before I know what is wrong with the truck.
Thanks

RCW

It sounds like you have two distinct problems, one if fuel related and the other is likely related to the automatic transmission linkage.

Regarding the fuel system, a 12 valve is pretty simple. They require a good transfer pump, and it sounds as if you have dealt with that issue; they require good fuel hoses from both the frame to engine and from the tank to frame - they should be replaced every two years, four years if you use USCG approved marine fuel hose; the fuel tank pick-up hose is a real problem on older trucks, and the sender unit needs to be pulled and that hose replaced with the same frequency as the other fuel hoses. Also, check the screen in the tank for algae or other scum buildup. The screen in the bottom of the fuel heater is frequently overlooked and rusts, once it starts rusting it has to be replaced. The electrical connector for the fuel heater also develops air leaks, and can most often be sealed by simply unplugging the connector, filling the plug with dielectric grease and replugging the connector. The fuel injector overflow valve must be in good shape, and the spring and follower intact and holding the check ball firmly.

Another thing to check on the 12 valve is the air fitting at the back of the AFC housing. Make sure all the connections are sealed and that the AFC is functioning. Sometimes, something as simple as the connector to the wastegate will work loose and allow the pressure to drop enough to partially close the AFC.

Lastly, check the AFC diaphram itself. Your truck is of the age that that diaphram may be cracking and not pulling the rack lock all the way back, that will cause initial runability problems as the engine will be real slow to develop enough rpm's under load to generate enough air volume to overcome the cracks, and it makes for a nightmare.

Then there is the human error issue. Sometimes the rod on the fuel shutoff solenoid gets a bit bent when it is rocked over out of the way to access the fuel cam. If it gets bent it will bind the rack follower shutoff in a partial open condition, and is like running at part throttle. Double check that to be sure the rod is straight and that the solenoid is fully opening the lever on the pump.

I am leaping to a conclusion regarding the automatic transmission. But, nearly all throttle binding on a 12 valve is from the automatic transmission throttle valve cable either snapping one of those ends or a cable release working loose and binding that cable causing the throttle bellcrank to bind.

kpracing

Ok what is AFC housing?
Just came back the truck is doing it again this time I had to let it sit for a long time before it would run normal. And start it probably 30 times.
It idles rough and has a ticking sound from the engine when doing it.
The ticking doesn’t follow rpm's but is about every 2-3 sec.
I really need help fixing this.
Today I was pulling my trailer and everything was fine until I got on the FW and kept it WO to get up to speed then it started doing it.
FP did not get under 15 psi.
Losing power and the engine rpm won’t fall down when I let off the gas pedal.
it will stay up for about 3-4 sec then fall down and then the truck will die, starting it back up then it will idle rough and if I give it gas it will rev up but when it come back down in rpm it dies.
Please help on this one.
Thanks

Scubasteve

Is there not an issue with the fuel supply lines on the 94 and up 12 valves? I would check to make sure its not sucking air. Some of the symptoms you posted suggest air in the fuel supply.


Jason

kpracing

Ok so replace all the fuel lines from tank to fuel filter.
I don’t see any leaks!
What size is the line I need?
Would this happen like this is, it won't do it every day only sometimes.
Specially under heavy load
I would think if I had a leak I would see it all the time
.

Dr. Evil

In most cases you dont see leaks....the holes are microscopic and the fuel doesnt leak - the holes allow air to enter the fuel system and cause it to lose prime. Yes, this can be an intermittant problem like you describe. You can get the line at a marine supply house or from Larry B:

http://www.fostertruck.com/dodge/

The supply is 3/8" and return is 5/16" - 2 hoses at the front and 2 at the tank. Make sure the line you use is USCG "diesel rated fuel line" or you will be doing the job again in a short time.

Another item to look at replacing is the overflow valve:

http://www.dodgeram.org/tech/dsl/tro...p.htm#Overflow

http://dodgeram.info/tsb/1996/14-07-96.htm

kpracing

I took out the overflow valve. it just look like a needle I don’t see a valve.
The needle don't move in or out is that normal?
I also took off the bottom of the fuel heater to check that.
It look good the oring look good also I applied some grease when I put it back on. I also did put grease in to the plug as said before.
What fuel pressure is normal? Right now I have 15psi idle and @ 2000 rpm I have 23psi no load. On the road it will go up to 26psi right after I let of the gas
Is this normal

Dr. Evil

Your pressures do seem low for a 12V., Could be the lift pump but I cant remamber the numbers off the top of my head at the monent...I think you should have at least 23 psi at idle and up to 35 or so at cruise (no load).

Someone correct me if Im wrong.

kpracing

Lift pump is brand new.

kpracing

Just got all my new hoses to replace the old ones.
I'm going to replace them all the way from the tank to the front, not using the metal tubing anymore, I can do that with no problems right?
For now I just installed a clear piece of tubing just before my IJ pump.
I want to see if it is air causing this, and now I can’t get the truck to do it.
Anyway I'm going to drive with the clear tubing until I can get it to do it so I know what is going on.
Thanks to all of you, I will keep you updated what is going on.
Thanks

Scubasteve

Loss of power, high idle and slow return to idle(poor fuel management due to air in the system) and stiff pedal are all signs of air in the fuel system.

If you have never replaced the fuel lines it is a very good chance that after 10 years they are cooked as many people after 5 or 6 years were having issues.


Put those fuel lines on and you will more than likely solve your problems. Any weather checking or cracks in any of the lines are a NO NO..




Jason

Dr. Evil

A new overflow valve would also be a good idea.

kpracing

Thanks to all of you.
I did all of the stuff I was told to do, the last thing I did was changing the overflow valve.
After each change I made I test drove the truck.
It kept doing it until I changed the overflow valve, now I just wish that I would have started with the valve.
Anyway my fuel pressure went way high now with the new valve in there.
Idle I have 26psi and driving it is over 30psi I don’t know how high it goes that is as high my gauge will read it that normal?
The truck runs great now have way more power, I had the trans slipping, so I guess that will be my next problem.
How is it to install a 5 speed manual trans in this truck
But for now the truck is pulling great.
Again thanks for the help.