Engine/Transmission (1994 - 1998) Boost Pressrue Question

[jspringer]

I need a little assistance. My truck is a 97, 5 speed, completely stock, 170K miles. I have owned it since new so I know nothing else has been altered. Over the past few months I have noticed a loss of power. I have changed the fuel filter and pre-filter and plan to evaluate fuel pressure as soon as I assemble the parts to make a FP test rig. As part of my diagnostics I checked manifold pressure (boost). Having never monitored this parameter before and would like to know if what I am seeing appears normal.



• At idle no detectable boost pressure.

• Cruising at 60 MPH, level ground, truck unloaded 3-5 psig.

• Accelerating through the gears on level ground and shifting at about 2000 RPM, 10 psig max.

• Full acceleration in forth gear with engine at the governor stop 22 psig.



These numbers appear normal to me but I would appreciate a sanity check.



Also, if anyone knows a source for a pre-tapped fuel pump inlet banjo bolt for monitoring fuel pressure I would appreciate a heads up.



Thanks!!!

 

[JFaughn]

Your numbers look normal .
An AC supply house , a parts house that has a good selection of fuel injection fittings , then if & when you change the overflow valve [ controls fuel pressure from lift pump - by restricting the return ] .
You may be due for a lift pump & overflow valve , testing & symptoms-is it taking longer to start after sitting for 1/2 day or with a low tank ?
The best source I know of for the OFV & LP is Marty Tompkins , Performance Diesel Injection and Turbo , he did not have a internet site last I checked , so going by memory , may need to get a variation of names to find .

 

[CRohwedder]

I agree boost seems normal to me too. If i were you i would buy gauges, including a fuel pressure to monitor it at all times. To do that this is what i did, i slpiced in a t-fitting and bought a electronic fp gauge from autometer and added it to my gauge pillar, slpiced it before the fitting that goes into the pump. That is my recomendation or if you didnt want to get the gauge you coulde doe the same thing that i did only block the top of the t-fitting when not wanting to check fp, that way you could just hook you gauge up to it when you wanted to check it. Just an option.

 

[jspringer]

Thanks for the quick response. I thought the numbers looked OK but wanted a second opinion since I never monitored boost pressure before. I have already replaced the Overflow Valve with a replacement from TST ($60. 00). Same valve from Cummins was $164. 00 (I checked that price from two seprate Cummins dealers in Florida (Ocala and Tampa) becasue I couldn't believe the price). Anyway, based on your feedback it appears I can eliminate induction system issues and concentrate on fuel delivery. My next step is to run the FP diagnostic (TSB-14-07-96) but I suspect the lift pump will be the culprit since it has been ticking away for several years.



Thanks for your help and I will post the solution when I find it.