Engine/Transmission (1994 - 1998) I'm stumped - Low boost & power

[Tom C]

I've seemed to have lost boost and power and can't find the problem.



With the stock injectors my boost would climb fast and peg 30PSI. I installed the new injectors and I did get a little more smoke but no real noticeable power increase. #@$%! But I did get a hesitation at light to mid power. I then found my 0-35 psi boost gage would only read to 30. So while waiting for the new boost gage (0-50 psi) I decided to put the stock injectors back in. With the stock injectors back in I noticed I had a hard time getting the boost to 28 psi and it would move up real slow and power was also down. After getting the new boost gage I put the DDP injectors back in and I got more boost but it only goes to 36 psi before leveling off 33 psi. This is with the turbo waste gate disabled. Truck will smoke good till boost kicks in then clears up with a slight haze at full throttle. I have 5-8 psi of boost at 70MPH which is what it did when stock.



I’ve checked:



Timing

Fuel pressure

Tightened all intercooler clamps & inspected rubber for cracks

Turbo waste gate is closing

Tried several AFC housing adjustment (spring, tension, position)

Tried cam plate in several positions

Checked all boost & vacuum lines. (Even replaced some)

New fuel filter

Removed fuel heater

Adjusted valves

New fuel





I have a strip of road I’ve been testing the truck speeds on when ever I add or adjust for performance. Its 2 tenths of a mile (street sign to street sign), up a 5% grade. Goes like this:



Stock = 54mph

Stock with stock cam plate full forward = 61mph

Stock with stock cam plate full forward w/transmission mods = 66mph

Added #10 & gsk = 75mph

Custom #10 (more off top) & meth = 85mph

Added ddp3 injectors = still 85mph and this were the problem started



I’ve talked with Piers and DDP and they seem to think my pump may have a problem. Could the demand of extra fuel from the new parts somehow cause a pump to go bad? The pump may have been on the edge of going bad and the extra demand for fuel may have put it over the edge. Any one else experience this? Anything else to check besides the pump?

 

[PKirby]

Have you replaced the overflow valve on the pump? They get weak over time. You might want to rig up a temperary fuel pressure gauge and run the hose from under the hood, tape it to the windshield wiper so you can watch it under full throttle.

 

[Tom C]

Yep, did that.



The pressure was a little weak at idle (17 psi) so I stretched the overflow spring which pushed the idle pressure up to 50 psi . I worked the spring and now have 35 at idle, 38 at highway speed and 28 and full throttle.



I would not recomend going to 50. I gave my self a fuel leak from the filter drain o-rings doing that. After getting the pressure down to 35 and turning the o-rings over it does not leak anymore .



Thanks for the suggestion.

 

[RKraiza]

had the ssame thing happen to me,,,... turned out to be one of the intake manifold bolts blew out, causeing a boost leak. check the 8 mm bolts that run the length of the plate attop the intake, if your missing one, thats your culprit. . hope this may help

 

[Vaughn MacKenzie]

Tom have you checked to make sure the shutdown relays are good and pulling the solenoid up all the way? A friend had a solenoid linkage hang up on him enough to keep it from pulling up all the way and turned his truck into a dog. Took a long time to track it down. I would check this adjustment to be sure http://dodgeram.org/tech/dsl/troubleshooting/12v_fuel_solenoid.html

 

[Tom C]

Vaughn, I had looked at that. The solinoid if moving its full travel but I will check the distance.



I think I found it or should I say stumbled on it. I had tried plate adjustments by itself and tried afc changes by its self but never tried changing both at the same time. I don’t like to change many things at once, that way if something goes wrong I know what it was. I moved the plate back 1/8" from full forward and tighten the star wheel 10 clicks rearward from full forward (using the light spring). Also checked to see I was getting full rack travel on the came plate which it appears I am and doubled checked the governor lever (no adjustment needed). Turbo now spools quickly and boost is up to 40 psi (still with the waste gate disabled). I don’t think this little turbo can push more than that, can it? Power is way up and my EGT’s are through the roof (at full throttle). So things are looking better except for the EGT’s. I plan to tighten the afc spring a few more clicks to clear up the low boost smoke at mid to full throttle.



This truck is the finickiest one I’ve had #@$%! . It’s my 3rd 12V and I modified all and got good results with little adjustments needed but this truck with any little thing I add it requires almost a complete retuning. I hope I don’t have to do all this again when I add a turbo. It's amazing how the littlest adjustment can make the biggest difference. Maybe my getting into the AFC again just joggled something enough (like the start solinoid) to get it going again. I still have what feels to be a hesitation/jerkiness in the power with light to medium power at 5 to 20 psi of boost. Any idea’s on that?



I have a date with a Dyno on Tuesday. I'll see if all this trouble was worth the effort. :-laf