HELP! Losing Power in my TST boosted '94

[scaryfast]

I've got a big lose of power in my 94 that's been boosted with a TST 250/635 plate. The truck used to run awesome when towing my trailer but now it struggles getting up minor grades, what could be wrong? The EGT's are even low, I used to easily exceed 1200 if I wasn't careful, now it tops out at about 900 (pre turbo). It has a new air and fuel filter and the injector housing still is all the way forward. The truck only has 79K miles and the TST kit has only been in a year. Help!

 

[Bob Wagner]

has your boost pressure dropped? loose intercooler clamps?

 

[scaryfast]

No, the turbo pressure is still good.

 

[Cooker]

Have you checked your fuel pressure? Maybe a bad overflow valve?



Does the truck run rough, or idle rough?

 

[scaryfast]

The truck runs smooth. It actually runs like it did before I boosted it, I'd swear someone came in during the night and removed my TST! I asked Mark about my power drop and he suggested checking that valve, but I don't know where it is, I couldn't see it where he told me to look. Passenger side of the injector pump between the pump and the head. The only banjo fitting I could find was on the passenger side of where the injectors are towards the front on the engine. There was nothing inside when I removed that banjo fitting so I assumed I had the wrong fitting, only I can't find any other fitting?

 

[Steve Roseman]

Mr. Dee, The valve is located in the banjo bolt on the return side of the injector pump. The inlet is on the driver's side and the outlet is on the passenger side. They are the only two fuel lines connected to the SIDES of the pump. You will recognize the valve by a bolt head on top of another bolt head. Good Luck.

 

[scaryfast]

That was the banjo fitting I took loose! So the valve is inside the bolt? How does it come apart? There was barely enough room to take it loose and even then I had to bend the fuel line to look into the injector pump.

 

[RBoles]

Mr Dee,



On the early '94 engines the valve is not adjustable or repairable. The only thing that you can do is replace it. You can get them from Dodge, Cummins, Bosch, or many other places advertised on this site. However, I see that Piers has them on sale. He advertises on this site, you can find him at www.piersdiesel.com



I also have an early '94 with 120,000 miles on it and I have already had to change the valve (not on sale then).



Good luck I hope your POWER comes back, soon



Robert

 

[dieselburner]

Originally posted by Mr Dee

There was barely enough room to take it loose and even then I had to bend the fuel line to look into the injector pump. [/B]

Dee - I have a 98 and when I installed my boost guage I had to get my hand in there by the fuel line. I must have bent it or damaged it somehow because shortly after that I had fuel spraying out of the return line at the mounting tab where it is mounted to the engine. If you put a tweak on that line, I would keep an eye on it. I replaced mine all the way back to the fittings at the frame rail with flex line about 2 years ago with no problems. Not trying to get you worried but just something to watch for.



Edit:

Forgot to mention - Check your boost sense line from the head to the AFC. If it's cracked or loose you will loose the boost pressure to the AFC which moves the diaphragm in the AFC. Thats what gives you your fuel as the boost comes up.



Steve

 

[Howard Durand]

Sounds like you are not getting a good flow of fuel to the injection pump. Either that or the injection pump is having problems.

I don't think a weak overflow valve would cause that much loss.

Check the entire low pressure fuel system from the tank up to and including the lift pump. Check all of the lines, especially the rubber hoses. If there is leakage anywhere it can cause problems.

I replaced my fuel hoses recently. They were in terrible condition and I have about the same mileage you have.



If you can't identify the problem, Give Piers a call.

 

[scaryfast]

Thanks for all the great info guys. I'm ordering the pressure valve tomorrow from Pier or TST and then checking the rest of my fuel system including all lines and hoses. Is it possible that the lift pump screen could be clogged? When I change the pressure valve, will it be the whole banjo fitting and fuel return line as one assembly? Thanks.

 

[Howard Durand]

The new valve will come completely assembled and replaces the old one piece valve that is on your 94 now. You still use your original line.

I would replace the fuel hoses just as a matter of course.

My truck started losing prime recently and was hard to start. When I removed them, the fuel return hose was so badly cracked that fuel was leaking through the hose right under the hose clamp. The supply hose was not cracked but had an area that was nearly worn through from rubbing on something.

The easiest way to get to all of the hoses and lift pump assembly is from the underside.

To make it real easy, remove the starter and disconnect the front drive line at the differential so you can swing it out of the way.

It only takes about 30 minutes to do that and it gives you a lot more room to inspect the system and work on it.

Hope this helps.



HD



As an afterthoght you might check the fuel itself. Could you possibly have gotten ahold of some real crappy fuel lately ? Or maybe some algae growing in the tank?

 

[Alaskaskiff]

If low side fuel doesn't pan out, check the timing. There have been several revised specs for the torque on the nut that holds the pump in time. My truck was found at 8. 9 and reset to 14. 5. Huge difference.