What is that hose? (and other stuff)

[Mike129]

Howdy.



I am the new owner of a 1998 extended cab 2500, 4x4, automatic. Since I got the truck I have been concerned that it has not had the power and fuel mileage it should. (The power concern is just subjective; the fuel mileage has not been better than 14mpg empty; 12mpg towing ~3500 lbs. ) Anyway, while working through some of the obvious suspects (water in the fuel filter, fuel filter itself, pre-heater screen, air filter, cat, overflow valve) I noticed a hose attached to the inside of the right front fender behind the air cleaner that simply ends there in some sort of cap. What is this? It seems to be leaking something, but for all I know it is simply some sort of overflow.



On the power/fuel mileage front, the overflow valve spring was only ~3/8" (I stretched it for now) and the fuel filter was a bit dirty (I replaced it). I do not know if I have found everything. I hear a noise that I fear is the wastegate being constantly open, but I don't know if I have the tools to check that. I will also need look into the fuel pressure and potential vaccuum leaks at the turbo. Unfortunately, I don't have the tools to check the fuel pressure, and I'm not sure the best way to locate vaccuum leaks.



Thanks much for any assistance.

--Mike

 

[Evan A. Beck]

The hose under/behind the filter box is the breather for the front axle. There should be a little oily residue around it. Just wipe it up with a rag every now and then to keep it clean.



As for your wastegate problem, the best way to check its operation is to have a boost gauge. Your truck should make about 20 psi in the stock form, and if you crimp off the wastegate line, you should see upwards of 25 psi. There will be no vacuum in the turbo system, just positive pressure. Even at an idle there will be no vacuum. Perhaps you are referring to boost leaks, which are very common on all Cummins powered Dodges. Best thing to do is to inspect all the rubber hoses related to the intake system. Tighten the clamps with a 7/16" deep socket, and you should be in good shape. There is an A/C line that tends to rub a hole in one of the intake hoses. This one is located on the passenger side of the engine compartment, right next to the A/C compressor. Just push the A/C line out of the way.



Test your fuel pressure, it should be around 16-18 psi at idle, and 22-25 psi under load @ 2,200 RPM. To check lift pump output, briefly (1-2 sec) clamp off the return fuel line. The pressure should rise very quickly, up to 55-70 psi. If it is slow in coming up, then you most likely have a bad lift pump. Overflow valves usually last between 60,000-80,000 miles. Lift pumps can go up to 120,000, but typically fail before then. For best results, change your fuel filter everry 10,000 miles. Avoid buying a Prime-Loc fuel filter system. It's a POS.



You may want to do a valve adjustment too, since its probably been a while for this truck. Every 24,000 miles you should perform one. Its simple to do, and doesn't take very long.



Injection pump timing is also an issue with the 12V trucks. About half the time, the timing is retarded and needs to be reset. If you start up your truck on a cold day, and rev it to 1,800 RPM, watch for some smoke. If you got blue/white smoke and a sputtering engine, then your timing has slipped and needs to be reset. Correct timing can mean more power, a smoother running engine, and better mileage.



I have worked on hundreds of Dodge trucks, and the items I have outlined above are the most common perfromance-related problems. Best part is that they are all easily fixed.

 

[Missouri Mule]

Evan,

"Avoid buying a Prime-Loc fuel filter system. It's a POS. "

It seems like you have had bad experiences with this add on.

Lucky for me I wasn't plannning to waste my money on it any way.





" To check lift pump output, briefly (1-2 sec) clamp off the return fuel line. The pressure should rise very quickly, up to 55-70 psi. If it is slow in coming up, then you most likely have a bad lift pump"



Now this is the type of info I like. Also injector pump timing ( the Mule seems to run real good on some days and other days so-so, mite be tempature/ humidity causing this though).



Mike adding a good diesel injector cleaner or diesel fuel conditioner at every oil change should keep your injector pump and injectors up to par.



Could the noise you are hearing be the turbo?Wastegate should not close off the exhaust to tubine/turbo until your in higher rpms and speed.



The mileage seems to be to be to low but I have read and talked to Dodge/Cummins owners that complained about the same figures on mileage.



Evan covered all the basics.

I have noticed at the fuel pumps that not many people make sure their fuel cap is on tight (at least three- clicks, I do mine four).

Your rear end and tire size could reflect on fuel mileage.

 

[Mike129]

Thanks guys. Some replies and comments:

-------------------------

[from Evan]

"As for your wastegate problem, the best way to check its operation is to have a boost gauge"



> Unfortunately I do not. Might need to get something because right now I cannot check boost or fuel pressure.



"Perhaps you are referring to boost leaks"



> Argh, yes, of course!



"Best thing to do is to inspect all the rubber hoses related to the intake system. Tighten the clamps with a 7/16" deep socket, and you should be in good shape. There is an A/C line that tends to rub a hole in one of the intake hoses. This one is located on the passenger side of the engine compartment, right next to the A/C compressor. "



> Thanks. I'll do my best to trace out the system and check everything.



[from Missouri Mule]

"Mike adding a good diesel injector cleaner or diesel fuel conditioner at every oil change should keep your injector pump and injectors up to par. "



> Okay. Any recommendations on the "good" products. So many additives/cleaners aren't worth the bottles they fill.



"Could the noise you are hearing be the turbo?Wastegate should not close off the exhaust to tubine/turbo until your in higher rpms and speed. "



> Oh. I thought the waste gate closed off to build more pressure at lower RPMs. I guess I am just confused about that.



"I have noticed at the fuel pumps that not many people make sure their fuel cap is on tight (at least three- clicks, I do mine four). "



> I think I am okay here, but I'lll keep an eye on it.



"Your rear end and tire size could reflect on fuel mileage. "



> I have the 3. 54 rear end, and the tires are 286/75R16, but I did factor the tire size into the calculation (assuming the odo wasn't already corrected).



Thanks, again.

--Mike

 

[shendren]

i've got 85k on my truck. i guess i'll change the overflow valve. how much do they generally run. thanks. scott.

 

[gitchesum]

Give that tire burnin Canadian a call, they have them for around $55. I believe Cummins wants $75 or so for them.

www.piersdiesel.com

 

[Missouri Mule]

Mike,

Sorry wrong term. Open is correct.

Describe noise you are hearing?

The wastegate opens up to allow exhaust gasses to bypass the turbine at higher speeds / high rpms.



Our turbos have a small diameter housing so at low rpms and/ or low speeds our engines can produce a lot of torque. The smaller diameter housing compresses the air more, which is equals to more boost at low speeds.



The factory setting is around 20 psi (boost pressure). I understand on a stock engine (no horse power upgrades) we can go to 30 psi safely.

If overboost occurs the turbo and engine can get fried. But not likely on engines still stock Horse power.



Gauges ( boost and exhaust temp gauge) are a must if adding horses or increassing boost.



Buy a Dodge service manual for your year of truck its worth the $ 100 bucks.



Do a search for fuel cleanners plenty of info on them.

I use Amsoil fuel conditioner now and then on my Mule when a valve starts to tick in the injector pump. Good diesel fuel helps also. Usually stations where the big boys fuel up will have a good cleaner in it.

 

[Mike129]

"Describe noise you are hearing? "



> It is a sort of puff/tap sound, like air pushing a flap open and it letting dropping shut.



"Buy a Dodge service manual for your year of truck its worth the $ 100 bucks. "



> Done. (And I agree that it's worth the money. )



"Do a search for fuel cleanners plenty of info on them. "



> Will do. Thanks!



--Mike

 

[Missouri Mule]

Mike,



What type of speeds /RPM are you looking at when you hear the flapping?



Are you towing something ?

Going up hills?



I've heard of them flapping pulling trailer going up hills.



Boost gauge or follow manauls instructions on setting.

If set correctly already do as Evan suggested or I believe TST has a adjustable elbow(for ajdusting wastegate opening). You can check on this by doing a search.



Never heard mine flapping or open or close . Guess I have a lite foot.

 

[Mike129]

"What type of speeds /RPM are you looking at when you hear the flapping?"



> One the truck is warmed up, I hear it at almost every speed/RPM except for idle. Say 1500-2400 RPM.



"Are you towing something ?"



> Nope.



"Going up hills?"



> Nope. Just driving around... .

 

[Missouri Mule]

Looks like actuator or jam nut could be loose letting the control rod self adjust. Only things I can think of unless the spring is messed up (doesn't show in diagram but somewhere around lever and wastegate door).

If hose had leak the acuator would not get enough boost to open door.



GoodLuck