Engine/Transmission (1998.5 - 2002) No Power - can it be the turbo?

[telliott]

Dont quote me on this, but i'm pretty sure i heard that the bosch spec for needed fuel pressure is 14. 5 psi. However i had a lift pump slowly go bad on me and was seeing significantly lower numbers with out loss of power. i have since replaced with a walbro and now get almost exactly 15 with very little variance at WOT, but i still didn't notice any change in power or idle. I would doubt that fuel pressure is what is causing the poor idle.

 

[telliott]

As far as the "correct" pressure, it all depends on who's doing the talking at the time. If you do a search you'll find all sorts of answers. Basically, high pressures (~18+psi) may cause hard starting and could possibly cause premature wear to the internal valving, and low pressures (~6 psi or less) won't supply the surplus "cooling" fuel the VP44 and may cause excessive wear/overheat. I think about 15 psi at idle is the goal for most with a psi or two in either direction. The key is not going below 5-6 psi under load.

I would also agree with what PC12Driver said. From everything i know, your pretty safe anywhere between 6 and 18 psi and wont cause damage to your vp, however from personal experience, you can have less than 6 and never notice a difference in the way it runs.

 

[draymorris]

OK

The cooling aspect makes all the sense. And I think I have seen that in a thread somewhere before.



Think about this theory - I have 6 psi most of the time at hwy speeds. Today I go on the longest hwy trip yet with the truck and in town driving as well. Maybe the pump was getting gradually hotter. The fuel in the tank gets hotter as I go - the pump gets hotter - the electronics in the pump are affected, but only enough to be noticed at idle.



Is this a good theory?

Where is a good place to get a Walbro?

Maybe in Fort Worth area?



Thanks for the info! PC12 and Telliot.

 

[draymorris]

Also, if I get my lift pressure up and the idle problem goes away - it would be a good learning experience as well as make my vp last a while longer.

 

[telliott]

i got the whole system from glacier diesel, it'll cost you a little more than the just replacing the pump, but i think it is worth it. you can find it here. Glacier Diesel Power - Product Detail

 

[draymorris]

On another thread "I can't stand it anymore", someone recommends a possible injector problem.



Opinions?

 

[ToolManTimTaylor]

Maybe the pump was getting gradually hotter. The fuel in the tank gets hotter as I go - the pump gets hotter - the electronics in the pump are affected, but only enough to be noticed at idle.



Is this a good theory?

Yes as the fuel return brings warm fuel back to the tank. Have you looked into the possibility of a cracked head? The 99-02 heads I don't care how mint suffer from cracks. Plus being "Abused" I will bet 10-1 odds ... ... And not the "oil in anti freeze/ anti freeze in my oil" kind but they crack from intake to exhaust 85% of the time.



Turbos in general do not loose power over time without some sort of tell tale sign that they are going into quisinart mode. Yeah oil is a sign but that could be from a K&N or somethin'



Is the truck an auto? The TC could be weak and balloned as heck or the clutch worn if a std trans.

(Easy to slip in stock form)



VP44's usually die shortly after a 216 code or can live for years after getting one. They are fickle and can be THE root of power issues from day 1. (Have seen a member dump thousands in their truck and gained marginal numbers on the dyno and was angry at the results. CHanged his VP44 and he got the missing 90 hp ... . 90!

 

[draymorris]

Thanks for the info Tool Man

Having heard of the head problem before - just a block leaking water on these year models. I hope that is not it.

I think I have a plan of attack at this point:

First the lift pump/pressure - get it up to 14 or so and see if the rough idle goes away and also try to keep the vp cooler and last a while longer.

After that, a steering stabilizer and other steering components to get it driving right.

After that focus on the power. I can drive it OK now and once I install my guages I think I can keep from doing any further damage if there is something wrong causing EGT's or low fuel.



Maybe by then I can afford to have the pump rebuilt and maybe gete a set of injectors.



The clutch - a brand new Luke Gold series - no problems there. I replaced it myself - that is why I have this truck. Not going to mention the price I paid, but I could not pass it up. The old man that had it I think rode the clutch - it was thrashed - I had to replace the flywheel as well. Anyway the clutch and transmission feel good.

On the thread about the idling problem some people recommended injectors, but I have heard the same thing about them as well, - they usually just go out as far as electronics are concerned. If an injector was plugged it would run rough all the time.



Any thoughts on injectors?

 

[Wooter]

Check The Hose (boot) At Turbo Inlet - Make Sure Its Not Leaking (loose Clamps Or Cracked). That Was The First One To Go On My Truck (98. 5) Model, And When It Does, Ya Loose A Bunch Of Power And Ittl Really Smoke! Check All Of Them To Be Sure. If All Of Them Are Original, Would Be A Good Idea To Replace Em! Geno's Has A Kit To Do The Job.

 

[draymorris]

Update:

Hoses check OK

Filter OK

Don't want to even think about a cracked head as mentioned in an earlier reply.

Put on different lift pump last night - now I get 9 psi at idle and can pull it down to 5 at WOT - Carter specs said it would produce 14 - 16 psi. Maybe I have more fuel bypassing in the VP44 than I should? Has anyone heard of this before?

Still have the rough idle after warm issue and the pump did not make a difference in the power.



I think I will start a new thread to get more exposure - no offense to anyone who has posted here - I really appreciate your input and help.

Thanks

 

[ToolManTimTaylor]

Yes I have seen bypasses go bad.



All the posts on loose boots, hoses, plugged air filter, bad turbo, bad intercooler, Theese things would produce soot at the power loss levels you describe.



Allbeit great places to start looking there are a few others that may also be a culprit. Check the aux vent tube at the fuel tank line bulkhead. Theese have been known to get plugged up with all sorts of crud and on some 99 models a cap left in place has been known to seal the airway. The tank will try and draw itself down to a semi vacumated state making it hard to move fuel. Ever take your fuel filler cap off and hear air sucking back into the tank as you losen the cap?



Check and make sure air is not entering the fuel return line at the Tee fitting just above the factory LP. Air bubbles can travel to the high spot of the engine (Front) and create a "pocket" that can absorb pressure out.



Leaking fuel transfer tubes are also a HUGE culprit. The end of the tube that enters the injector can be mashed a bit so that an uneven seal takes place. This in turn bleeds pressure and causes a foul idle too at times of warm vs cold operation as the dissimilar metals of the tube and iron heat up at different rates and expand at different rates too.

 

[draymorris]

Thanks again ToolMan. I never did start another thread, so I think I will just continue this one for now. Is ther a do it yourself fix or troubleshoot for the transfer tubes. I have done a lot on these trucks, but I am least experienced on the fuel systems.

 

[DFerverda]

I think your low power issue is something different from the small miss you talk about. I had the same problem a few months back (the miss). It ended up being the grounds on the truck. It is cheap and easy to check. Just take them all off and sand the surface's and put some electrical grease on em and tighten them back down. Do all of them, battery and every ground you can find on the engine and body. I also used the same grease to lube up all the electrical snap connectors i could find. To date the truck has not had a single sputter or miss.
Dirk

 

[KLockliear]

Fuel supply pressure - stock truck with stock, properly working pump should put out 12-14psi at idle. Any less than 10psi, replace the pump. Never less than 6psi WOT for reliability. A good part of the fuel sent to the pump is used as lubrication and cooling, and returned to the tank, so you need more than enough.



As HP increases, the fuel system becomes a liming factor. We found that at 350rwhp, the stock fuel lines and banjo fittings were the first restriction. Changing to full size AN style fittings and 3/8" line would typically increase VP inlet pressure by 6psi WOT at 350rwhp.



Once that's done, the stock lift pump runs out of capability to maintain 6psi WOT at around 425rwhp. Adding a Carter P4600HP pump (rated 7psi) to the system would yield 18-22psi at idle, no less than 10psi at WOT at 500+hp.



A stock truck should make and register 18-19psi at WOT, full boost, on a scan tool. Snap On MT2500 series should read that no problem. Look at MAP voltage and boost psi. Holding different throttle positions should allow you to see all the numbers in boost pressure from 0-18/19psi, not jerky jumps.



Do you have a boost gauge in the truck? How much boost does it really make on a gauge? How many miles on the truck? Did you fix that boost leak under the heater grid element? Any codes come up on the scanner?

 

[draymorris]

Boost guage shows as high as 24 psi under the right conditions of course.

190k on the truck.

No I haven't done anything on the small leak.

No code on any scanner that I have used.

 

[KLockliear]

If the VP44 has never been changed, it's probably on the way out. Life expectancy is about 1/2 the mileage you have on the truck. When you replace the pump, make sure you also replace the overflow banjo on the outlet side of the pump. It is not included with the pump and can cause FP problems and hard start issues.

 

[draymorris]

What is the issue on the banjo fitting? Is it the that sends the fuel back to the tank?

I don't know much about the history of the truck.

 

[KLockliear]

There is a pressure relief valve inside it. Replace it at 100k or next VP change.

 

[DLMcpherson]

Any solution

Did you ever get to the bottom of your power loss prob/em?

i have a 2002 with basically the same problem

 

[jhoughton]

A friend of mine uses one of the Airtex pumps supplied by Vulcan Performance. You can get this for about the same money as a LP. They provide all the required fittings and was easy to put on. He shows 16-18 psi all the time on his 02 fully stock setup. He has an Air Dog of his other rig and likes it also. I use a FASS on my 99 and have been very happy to date. It's been on now for 4 years with 16 psi at idle and 12 WOT with the Edge Comp on 5x5. I really like the Mach 1. 6 Injectors. Hope you work it out as I still enjoy my 99 and have no plans to upgrade or replace. Jim