Engine/Transmission (1994 - 1998) Fuel Plate Tech question and opinion on DST #5 profile

[PGWIN]

turbo tag is faded but... Holset and 24xxxx on it.

the exhaust is stock with exception to the BD EXHAUST BRAKE where the valve is inline just in front of tha CAT.

 

[JKosten]

Check out http://www.myholsetturbo.com/identify.html of ID help.

But the model should be on that tag.

 

[PGWIN]

stretch the over flow valve spring to .055" just over 1/2" and yes that is in the ball park for boost from the era.Line Plugged should be little more.

MLee and GAmes:

OFV stretch: original spring was at 0.460", i strecthed it to 0.480 and added a 0.040" washer on top of existing shim that effectively compresses spring by its thickness when installed. After that i could blow a small amount of air through the valve quick simple test, leading me to believe perhaps the seat was eroded. So ordered and Torq Tek OFV and gauge. With gage installed on original OFV I got 0 psi, I/'m pretty sure taking it apart and reassembling it change the seal characteriistics because the truck ran noticably rough at idle where it did not do that before OFV spring stretch..

Fuel Pressure: Fuel pressure test gage installed (gage from Pure Deisel oil filled with atmosphere vent for temp correction) with Torq Tek banjo snubber installed, I added a Torq Tek adjustable OFV (020).


i get 18 psi at idle, and up to 1800 rpm the fuel pressure does not change. I did read from Torq that the average with their OFV is 23psi at idle and the valve is factory set to 31 psi.


I"m assuming there is not any flow through the OFV at idle (completely closed by default factory set to 32psi). However it would seem that it must be opening at 18 psi considering the psi does not increase with rpm increase.


Does this sound correct that i shoudd adjust it? The part that makes me wonder is the statement that it is factory set to 32psi by Torq.



(Recent Fuel System Maintenance: New fuel pre-filter, deleted fuel heater, new pre-filter to lif pump hose, new Cummins lift pump (broken check valve in original), new fuel filter in last 2 weeks.)

 

[MLee]

I have this same valve from Torq Tek and was @20 at Idle and 32@2000. 18 is good but better @ 20-22 for Idle. Use 2000 RPM for the top end. Recommended RPM's are Idle and 2000 for the pressure test.

 

[PGWIN]

Do you think this is indicative of an air entrainment leak? I thought it really odd that the pressure didn't move at all with rpm increase - even up to 1800 rpm!

It starts instantly (as always), but i thought it also odd on the rate of pressure increase, it probably took several minutes (2?) to reach max psi at idle. But it has the snubber on it, and the test hose from Pure Diesel kit is .5" I.D. by 4 foot long, so maybe that is normal?

 

[PGWIN]

Went for Test drive while monitoring - here are the STATS:

1. Idle~775 rpm: 18psi
2. 2000 rpm - out of gear: 20psi
3. 2000 rpm - flat on freeway: 18psi
4. 1700 rpm - in gear foor off accellerator: ~29 psi.
5. 1800 rpm up medium grade pedal to floor (oh this still is anemic cummins - so not a rocket fueling) ~ hard to tell what exactly was steady state fuel psi - but i think lowest was about 15psi in this condition.


Interesting. So #4 is higher rpm, lift pump flowing more fuel, and i think the pump may be at same as Idle fueling. So we have the case of max fuel, lift pump putting out proportional to rpm, fuel to injectors minimum, so the highest flow rate through the OFV and of course the greatest back pressure resulting in highest PSI fuel pressure. I'm confident all readings apart from #5 are accurate wrt snubber effects (reached equillibrium).

So what do you make of these PSI's?

Overall there is a little more pep and i may think it idles less "lopy" at idle which is something that had seemed to crept up.

Under hard acceleration from about 1200 - 1600 rpm i can get a haze of smoke until the turbo catches up. the turbo will build boost to about 13-15 psi in about 3-5 seconds, max boost is still about 18psi.

I'm hoping its now time for a fuel plate!

Thx,

Paul