Engine/Transmission (1994 - 1998) Can't break 60-65 MPH all of a sudden

[BlameCandida]

I have a 1998 Dodge Ram 2500 with the 12valve CTD, 5-speed, 4WD



Just last month, I thought I had fixed all the problems with my truck. I relocated my batteries to the bed and rebuilt the starter. I found where the vacuum line for the cruise control had been eaten through by battery acid and replaced that. I installed the Dodge Steering Stabilizer and replaced the bushings on the track bar. My truck was driving great for about three weeks. No death wobble, no throttle going out from the bad vacuum line, no trouble starting the truck.



Then this weekend, things started to go wrong again. A cold front came through (not sure if it bears any responsibility), and now the truck won't break 60mph. Up through 4th gear I have no trouble building up speed, but when I shift into 5th gear, I end up putting the throttle all the way down and still can't get up to 65. I'm guessing this is some sort of fuel delivery issue, and hopefully not the transmission I just had rebuilt this spring. It also shouldn't be an issue with the fuel shutoff solenoid -- I replaced the solenoid with a PTO cable a year or two back.



I also noticed a small fuel leak under the fuel tank yesterday. About two years ago I patched over a scrape in the fuel tank with epoxy, and never had an issue until now. And to top it off, I had death wobble on the way home, after thinking I had solved it after all these years.

Are any of these issues related, or is something else causing my trouble?

 

[DavidC]

Fuel Filter ?

Dave

 

[AEdelheit]

I would check the little plastic hose Between the intake manifold and AFC housing, make sure it didint crack, also double check the air filter to make sure it didint get wet or somthings not living in the air box, sounds funny but seen it happen.

 

[Dieseldemon]

Check your fuel filter

 

[wcoomes]

I would check the little plastic hose Between the intake manifold and AFC housing, make sure it didint crack, also double check the air filter to make sure it didint get wet or somthings not living in the air box, sounds funny but seen it happen.

That happened on my 2001, clamps broke

 

[Bob4x4]

That happened on my 2001, clamps broke

LOL the vp44 does not have an afc

 

[Bob4x4]

When ever testing for low power concerns always check fuel pressure first especially on a 12 valve

 

[hsmith]

And, always check the pre filter screen, especially if it is original.

 

[BlameCandida]

I checked both the fuel filter and the prefilter, and both needed attention. I cleaned out the prefilter, replaced the fuel filter and lubricated o-rings, and put everything back in place after filling them with fuel. Everything is tight in place. I have attempted to bleed the fuel system according to the service manual by cracking the 10mm bolt, and pumping the prime button. I had a few bubbles come out on the first few pumps, but no fuel comes out of the bleed hole. I have attempted this about 10 times now, and the engine will not turn over. Am I missing a step somewhere?

 

[JPS]

Not to break into a thread, but I found that plastic line today. Had read about it some threads back. Discovered mine is broke. A bummer to get at. Anyone have a part #. What is the function of the hose. Would think rubber would be better. At least it would cracking to two pieces. TIA jps

I would check the little plastic hose Between the intake manifold and AFC housing, make sure itdidint crack, also double check the air filter to make sure it didint get wet or somthings not living in the air box, sounds funny but seen it happen.

 

[Dieseldemon]

Check the fuel cap that the vent is clear it should allow air in but not out

 

[hsmith]

It's late, but I'm thinking that is nothing more than 1/4" plastic hose with some ferrels and nuts. Important piece also.

 

[AEdelheit]

If it won't bleed there are a few possible causes, if the pump is on the cam lobe it won't actually move the diaphragm, have to rotate the engine a bit, there should be a decent bit of resistance throughout the whole stroke of the pump. It may be sucking air between the pump and tank, look for any cracked rubber lines, the pickup screen in the tank is clogged, Or the lift pump itself is bad. How much did you'll loosen the bleed screw? Make sure it's out far enough, it can take a good bu of pumping to bleed them.

 

[JPS]

Do you have a part # for that little plastic hose? Anyone tried rubber hose?? TIA jps

 

[HHhuntitall]

From what I'm gathering, it sounds like the lift pump has quit... . That would make it weak on power, and not prime up like it should... . I'd pull the fuel line behind the pump and see if I could pull fuel very easy with a vacuum pump or siphon hose... . If so, then the pump has probably quit... . It's not uncommon for that hose between lift pump and fuel tank to develope cracks and suck air. Does it have the quick connects on the bellhousing? Check the O-rings, if so... ...

Do you have a part # for that little plastic hose? Anyone tried rubber hose?? TIA jps

Rubber hose would be fine, but likely you'll have to have two barbed pipe fittings and two clamps as well... . I believe the original fittings are 1/8" pipe that go into the cylinder head and AFC valve assembly..... Be sure your line will take whatever your boost is +.



Oh, the purpose of that hose is to allow fueling under boost. If you have a slid "cam" plate, it won't really help until you build boost, unless you've fully backed off the star wheel on top of the AFC housing. There is a diaphram in there that boost(manifold pressure through that little line) pushes forward, allowing the fuel levers to move forward against the "Cam" plate only after there is adequate boost in the manifold. Basically, it prevents black smoke and excessive EGTs at lower rpms..... Boost also comes in through that line and out to the wastegate on the turbo. That wastegate line is silicone rubber and has an 1/8" pipe and hose barb with clamp.

LOL the vp44 does not have an afc

I built an '01 engine for a guy that didn't have a VP44... ... but it did have an AFC.....

 

[HHhuntitall]

Tube, Air Fuel Control (Cummins part number) 3931519 (the short one from manifold to AFC housing)

 

[JPS]

Thats the one!!! Thanks much HH. jps

Tube, Air Fuel Control (Cummins part number) 3931519 (the short one from manifold to AFC housing)