Engine/Transmission (1994 - 1998) Low boost problem, please help

[xrjeff]

I have a 95 Cummins 175 with a manual trans in a 4x4. It has the TST #5 plate which is supposed to be 230HP and 700lb. ft. torque. The last time I towed my trailer, I couldn't get more than 12lbs. of boost, and it normally would go up to 28 or 30. I have checked the rubber joint boots on the intercooler, and the little rubber hose coming off the replacement orifice elbow. All seems to be fine, so if anyone can advise where else to look, it would be greatly appeciated. The more replies, the better, so I can help fix it. I am towing again this weekend, and it would be nice to have some power back. Thanks in advance.

 

[Graphic man]

It sounds to me like your waste gate is stuck open or a boost leak somewhere

or a fuel problem

 

[xrjeff]

Any idea how to check the waste gate, or what else would cause the boost problem?

 

[Graphic man]

i had to take my turbo off to find out it was stuck closed

someone else my be able to tell you an easer way

but thats the only way i know

 

[Dave M]

Any idea how to check the waste gate, or what else would cause the boost problem?

You said you checked your boots. I checked boots a month ago and tightened the clamps... still low boost (9 psi). When I removed the passenger side boot at the intercooler I found it had rubbed against the body and had a 3 inch slit. Duct taped the boot and got 20 psi boost. Couldn't see it from above or below until I removed it. Got Piers intercooler boots ready to install this weekend.



Remove and Plug the boost line that goes to the wastegate and if that isn't it remove and plug the boost line that goes from the intake manifold to the AFC. It could be the AFC thats limiting the boost. Someone more knowledgable can chime in and tell you how to check to see if its limiting the govenor arm travel.



Have you checked the fuel overflow valve? Not sure it that will limit boost but will limit power.

 

[xrjeff]

Still need more help if possible

Thanks for the great posts so far. Please keep them coming. I tried pluggin the line for the wastegate, and it didn't do anything. I guess I will remove the boot like suggested, and also try plugging the line to the AFC. I don't know how to check, or where the fuel overflow valve is. More help on that would be great. Hoping to get it fixed by tomorrow night for a 300 mile towing trip, so please keep the ideas coming. Thanks.

 

[radixr]

I think the best way to check for a boost leak is to pressurize the boost system at the turbo inlet (or air filter outlet). There have been several threads on the ways to do this. Most use a rubber sewer coupling and 4" PVC end cap.

 

[xrjeff]

I could try that too, but it will have to wait until I get back. I just don't have the time right now. I did pull all 4 boots on the intercooler, and all were in excellent condition. For being 10 years old, they were all still as pliable as new. No signs of dry rotting, cracking, tears, or cuts. So the wastegate sticking, and a possible boot problem have been eliminated. I don't know how to plug off the AFC line from the manifold, since it's made of hard plastic. Any thoughts? Please keep the ideas coming, and I will try to chase it down one by one. Sure would be nice to have it done before tomorrow night though. Thanks to all, and please keep sending any ideas.

 

[Joe G.]

If the waste gate is stuck open, then plugging up a boost line will not affect it. You will have to disconnect the linkage and see if you can get it to move. You might try to lock it one way with some vice grips or whatever and take it for a ride to see what happens. Then force it the other way and do the same. I can't remember which way is open or closed. Maybe inspecting it will show you.

 

[Dave M]

A day late and a Dime short....As Usual...HeHeHe

Thanks for the great posts so far. Please keep them coming. I tried pluggin the line for the wastegate, and it didn't do anything. I guess I will remove the boot like suggested, and also try plugging the line to the AFC. I don't know how to check, or where the fuel overflow valve is. More help on that would be great. Hoping to get it fixed by tomorrow night for a 300 mile towing trip, so please keep the ideas coming. Thanks.

I found a link to www.dodgeram.org that covers the fuel overflow valve replacement. It is located in the front of the injection pump between the head and the inj pump , but on the pump in the return line banjo fitting. Its like a bolt with a spring in it that should measure 0. 5 inches. It would be bad if you had low fuel pressure and low power but I believe I'm wrong about it contributing to low boost. Since I mentioned it here is the link to that info:



Fuel Overflow Valve: http://www.dodgeram.org/tech/dsl/troubleshooting/injector_pump.htm#Overflow



You should follow the advice given earlier about removing the intercooler lines and pressurizing it with air to check it for leaks using a gauge. Others can provide more details on how to do that to see if it is leaking. Hopefully you will find a bad boot is your leak and not need to do that. Here is my thread with some pics of the torn boot I found in mine:



https://www.turbodieselregister.com/forums/showthread.php?t=127186&page=6&pp=5



And a pic of the torn boot by fender and the boot duct taped with a plastic milk bottle piece to protect it from fender.

 

[K5IP]

One more bit of info. If you have a boost pressure leak, (especially with a #5 plate) you will have higher than normal egt. If you have a overflow valve problem, (low fuel pressure), the low boost will be associated with lower than usual egt's.

Might help you understand it.

Rog

 

[surfbeetle]

I had the same problem!

I had the same problem, maybe you made the same mistake that I did. I have a 1995 175 hp with a manual trans, 2 wheel drive. I just put in the # 5 plate from TST. The truck had lots more power than previous to the plate install. I just put the combo boost and EGT guage in this past weekend. I was only getting 20 psi of boost. I checked the intercooler seals, all was fine. I called TST, they said that I should be getting 30 max psi of boost. In talking to them, they brought up the overflow fuel return valve and then I realized that during the install of the plate, I had neglected to install the boost control fitting on the turbo. In the TST directions http://www.tstproducts.com/INSRUCT98.pdf, mine is like "figure 2". In step 9, it says, "If your vehicle is like FIGURE 2 proceed to step 11 below. " So at that point during the install, we went to step 11 and didn't install the "barbed elbow" on the side of the turbo because nothing specifically said to do so and I did not know any better. TST was VERY helpful when I called them and at lunch time, I went home and changed the fitting and boost went up to 30 psi. Now, I will tackle the overflow return valve because I am not quite hitting top speed easily. Hope this helps.

Craig

 

[surfbeetle]

One more bit of info. If you have a boost pressure leak, (especially with a #5 plate) you will have higher than normal egt. If you have a overflow valve problem, (low fuel pressure), the low boost will be associated with lower than usual egt's.

Might help you understand it.

Rog

What would be a normal range for EGT with normal boost? With 30 psi of boost, would 1000 degrees be right? What is too much boost and too high of an EGT? Thanks in advance

 

[Dieseldemon]

Is there a lot of black smoke or no smoke?

 

[Dave M]

What would be a normal range for EGT with normal boost? With 30 psi of boost, would 1000 degrees be right? What is too much boost and too high of an EGT? Thanks in advance

Not sure... but from what I've experienced that would sound normal. When I had 9 psi boost max, I hit 1,250 F easily and could have pegged the gage if I didn't let off the pedal. After installing new Piers boots I'm running 26 PSI boost max and EGT's are below 1100 F. That's just from my experience in the past week.



Cummins spec's not to exceed 1250 F on EGT's (Pre-turbo). go to www.dodgeram.org for lots of info. Here is a link to that site for EGT's... go toward the bottom for EGT's and boost specs:



http://www.dodgeram.org/tech/dsl/Facts/94specs.html



From what I've read the max boost for the stock turbo is 30-35 PSI. Any higher and you need a bigger turbo.



Others more knowledgable will jump in here I'm sure. Hope that helps.



Dave

 

[Dieseldemon]

A lot of smoke and high egts is a leak in the intake system no smoke and low egts means no fuel AFC ?

 

[MultiSmith]

I have a TST #5 in the stock position using the template that came with the plate. I have an automatic trans with 3:54 rear gears. Truck seems to behave close to normal until I hit overdrive than it takes off of at around 50 mph. My boost at this point reaches 28-30 PSI and EGT reach 1200. I have little to no smoke from what I can tell. I also have the star wheel turned all the way for added fuel. I thought I would have seen a little more smoke than I am... I don't really want alot of smoke either but am wondering if what I'm seeing is normal behavior. I have yet to put in my triple disc ATS and Valve body and plan to do so now that the weather is better. I keep reading that I need lockup in all gears to see the power I wanting.

 

[Howard Durand]

When you installed the #5, did you check the governor arm adjustment? It may be going under the plate instead of following it up the curve.

 

[MultiSmith]

I used the template that came with the plate, Mark at TST made it sound that the only reason why I would have to ajust the governor arm would be if I moved the plate forward and recommended I put the plate in the stock position of the one I removed. Regarding the governor arm adjustment If I were to move the plate forward is this difficult to do, what is the procedure for do such a thing?

 

[ABorchard]

Click for Governor Lever Adjustment