Engine/Transmission (1994 - 1998) Low Power

[bramage]

Here's the scenario. A few weeks ago I installed a #11 TST fuel plate in my truck. At the time I had very limited time so after a test drive I tried to adjust the star wheel but it was nearly all the way forward so I turned it a few more clicks and left it. The power seemed to be an improvement over stock but not nearly what I thought it should be. Now after pulling the trailer several thousand miles since I can tell you that the low end power is hardly improved at all; and the top end only marginally.



The truck. It is a '98 Quad cab 4x4 5 speed with 3. 54 gears. It has 235/85 tires so the gearing maybe a little tall but I have seen many trucks with this combo and newer 4x4's came stock with them.



Observations. It seems a little slow to build boost off the line. Power seems low up to 1800-2000 rpm and only fair beyond that. Max boost is only 30psi and it takes a while to get there. Smokes black some on the low end but very little on top.



Adjustments. Yesterday I moved the plate forward (eventually all the way) and the AFC housing. Checked the gov. arm; it was fine. Checked the wastegate; it is free. Plugged the hose to the wastegate; still only 30psi. I did a visual check of the intake plumbing and every thing looked fine. Today I changed my fuel filter and put my #6 plate from my old truck in. None of these things improved performance. From what I understand the #6 in a 215 pump should run VERY HOT but I couldn't get it over 1300*.



In comparison to my old truck, ('97 auto, sold) with a #6, the modification seems very mild. This truck has half the miles and is rated 35 hp more stock. I could push 36 psi with the same boost elbow reading on the same guage. I could see 1400* very quickly with the '97 and have a hard time getting past 1250* with this one. This truck still has the cat and muffler allthough the previous owner did install a 4 inch cat-back (soon to be 4 all the way). I don't think the kitty is plugged because it will turn 3000 rpm's in the first 4 gears fairly easily without high egt's; so that should not be an issue right now.



I guess it just doesn't seem to set me back in the seat like my old truck and I am not sure why. My next step is to pressure test my intake system and look for leaks but I don't know where to go after that. It seems like I either have a leak on the charge air side or not enough fuel to build boost. Lift pump?!? The truck runs well and has sufficient power for everyday driving but does not feel like a performance truck. Bottom line: max. boost is 30 psi and seems slow to get there no matter what I do. Thanks in advance for any suggestions or help; and please correct me if I am wrong in any of my conclusions or diagnostic methods. I am still kinda new to this stuff. Sorry for the long post but I tried to include every thing I have done to the truck.



Junior

 

[JohnE]

Start with the overflow valve.

That 215 hp pump should pounding those training wheels.



Charge air leaks usually produces smoke.

Does the AFC diaphragm check out?

Is the AFC housing straight and not hanging up on the fuel plate?

Check the boost sense lines. you may have a leak.

 

[Deezul1]

Overflow valve spring should measure . 500 minimum when removed. Try stretching to . 550 and reinstall and see what happens. If it is improved then a new valve is in your future and Piers has the best price I have found

 

[bramage]

Thanks, I'll start there.

 

[bramage]

Well I just checked the overflow valve. It measured just over 7/16" and I stretched it to just under 9/16". Test drive showed no improvement, still only 30psi. Is there some other way to test it??



John and others:

When I checked the wastegate I only made sure it wasn't stuck by turning it with a pair of pliers. I could not turn it with my fingers but with pliers it turned without too much effort and quickly srung back whan released. Then I plugged the line to the wastegate and could not get anymore boost. Do I need to pressure test the actuator with these tests already done??



Thanks Jr.

 

[FATCAT]

Had the same thing almost ....

I had the same symptoms almost like you are having.



1st, my fuel presure was only at 20 psi, 10 at idle. Put in new overflow valve from Piers and presure improved a little. Took out spring and streched it, now I get 40psi fuel pressure.



The "no smoke at 30psi turbo pressure" problem is because the engine is not getting enough fuel. Try this to see if the problem is the AFC or the fuel plate:

- Remove the fuel plate completely, this will allow the rack to

move full forward. If you get full boost and (nice black) smoke

the top end, then the problem is the fuel plate. (rack is binding

on the plate somewhere).

- If you don't get full boost and black smoke, the AFC spring is

set way to tight.



The only other thing I could think of would the "gulp" the P7100 pump ... it may need a rebuild.



All this is provided there is no leak in the turbo pipes or intercooler.

 

[nfox]

Slow power

I would check the line that goes from your intake manifold to your afc housing and make sure it is not cracked or leaking, and then i would check the diaphram in the afc housing and make sure it does not have a pin hole in it. Thats my 0. 02$ worth of thoughts. Later!!

 

[bramage]

Any more suggestions?? I notice a tick from my drivers side till about 1500 RPM (probably the lift pump). Do you think this is my power problem also?



TIA,

Junior

 

[Howard Durand]

You are apparently not getting adequate fuel.

With the AFC star wheel that far forward you should be getting plenty of low end acceleration and gobs of smoke.



There is a fuel volume test described in the service manual. That might be a good place to start.

 

[Rams-n-Hogs]

When I first installed my #11, I seemed to have a similar problem. The fix for mine was adjusting the AFC diaphragm. Also, check the fuel return line, if you haven't done that already. If it's sucking a little air, it will cause low power. At least mine did.



Jim

 

[JohnE]

Have you checked the timing?

Have you checked for full throttle control? This requires someone to hold the hold up the solenoid and watch the linkage while the other person steps on the pedal. I remember someone with a manual commenting there is a lot of power in the last litle bit of throttle travel.



Did you get the pressure testing done? charge air, AFC diaphragm, WG actuator. I see you tested for free moption of the WG itself, but no mention on the actuator.



It could be the lift pump. Have you pressure tested? Flow tested?



-John

 

[bramage]

TTT

TTT:



Still trying to get to the bottom of this. No boost sensing leaks. Plate full forward. Afc full forward. Star wheel forward. New lift pump. New fuel filter. Fuel screen is clean. Stretched the spring in the overflow valve. Checked the governor lever, it checks out. Boost seems to build okay now up to 34psi in the cold weather with wastegate plugged. It will smoke abit if you lug it but smoke is gray not black.



Truck has better power then a stocker but DOES NOT feel like a performance truck. I am leaning towards timing. Perhaps it is very retarded, it starts instantly with some white smoke and has a slight hesitation/miss on the first acceleration on a cold engine if outside temps are low. Any other suggestions would be very appreciated.





TIA

Barry Jr.

 

[nfox]

Timing

I would get your timing checked to make it is at 16* or so, this will make it start better and have better fuel economy and more power. Oo.

 

[bramage]

The only thing that I don't understand about it being a timing problem is the low EGT temps. One would think with all the fuel (if in fact the pump is fueling properly) the EGT's would be off the guage.

 

[DSiemens]

Did you find a hole in the AFC diaphragm?

 

[bramage]

No holes in diaphram. It will hold pressure.

 

[bramage]

Problem solved!!

For those of you who remember this thread... . My fuel shut-off solenoid failed this summer, so I removed it and wired it open. It seems that either the original one was adjusted wrong or never lifted up all the way. 40 psi and 1600* we're fuelin' now. Now I need to install my CON FE.

 

[nfox]

Fuel Shut Off Adjustment

How far should the fuel shutoff lift when the truck is running, is there any certain measurment or specs?