Hey guys, this is my very first post on here because Im a brand new member. This may be a very common question for many of you. I have an 01 with 90k, injector pump appears factory, and I just installed Isspro guages. At an idle, the fuel pressure is about 7-9 psi, partial throttle is 6 psi and full throttle and boost will bring it down to 2 psi. Is this normal?

 

Too low.

Have you changed your fuel filter lately?

If so, it may need a new one.

My LP is the stock setup, I have 13-14 at idle, 9-10 driving normal, can get it to drop to about 5-6 WOT with a Smarty set on #9. I'm upgrading the fuel system in the spring.

You may have a weak LP or a clog in the system in the tank or fuel filter.

 

I just bought a new WIX fuel filter today and am going to install it tomorrow. Could it make that much difference?

 

2 psi is low. Verify your guage. Remember its all about volumn not pressure. There is a simple volumn test you can perform. I would verify the guage first. If it is correct most likely the folter is plugged or your lift pump has just about had it.

 

Yes.

BUT, so could a failing lift pump. With a health LP (and properly functioning gauge) you should see about 14.5-15.5 at idle. With no real mods, you shouldn't be able to pull it much lower than 11 or so.

 

Where are your manners boys!

Welcome to DTR

We're glad your here. Take your shoes off, sit a while, and enjoy the show.

Trust your gage, get a FASS II lift pump to replace the stock LP.

I've tried doing a volume test doing 70 WOT, I don't recommend it. It's all about pressure and 2 psi is too low, anytime.

 

That is too low if the gage is correct. When my FP was first installed it read low as there was some problem at the isolator. I did not do the install myself.
Mine 11-12 idle 8-9 hwy cruise WOT5-6. Read lower on a cold morning with the grid heaters on, lo voltage. Flow test at dealer when fuel fiter was changed was full flow, filled the beaker.
What is FP when you bump the starter? Mine 13

 

If I bump the starter it goes to 8 psi then slowly drops. I have no isolator....the pressure is sent via diesel flowing from the injector pump to the guage with no interferences; ie. isolator
BTW, I just bought this truck out of Collinsville, OK last weekend so the history I know about it is nonexistent.

 

Yes thsi is normal for a 2nd gen truck. The LP system on them sucks and should be upgraded ASAP. I installed a brand new factory style pump(Delphi) 2 weeks ago. At idle I got about 16psi, with the Juice on setting 1(milage) I could pull it down to 6psi, on setting 5 I could pull it down to 1psi.

TodayI installed a Holley blue pusher pump on the frame, now I have 29psi at idle, 26 cruising and cann't get below 15psi a WOT with the Juice on 5.

 

Mine is stocker pump is rock steady at 14psi @ idle 10.5 @ WOT.


not trying to hijack here but what the most recommended psi to the pump/. I've heard of exxessive psi to the pump damaging something?!?!?! I'd going to install a walbro shortly after I get the HRVP in, but I'm not sure what to set my relief at. I've read Glacier sets all his at 17-18psi? How about 20? 25?

 

When I change my filter, I buy about a quart of diesel fuel to fill the filter housing 3/4 full after I drain the filter housing and remove the old filter. When I install the new filter on the cap and put it in the housing, a little fuel may dribble out, I just screw the filter top on and wipe up the mess. When I'm done, I turn the keyswitch just enough to "bump" the starter then quickly release it to get the Free 25 Second Lift Pump Run. After the pump quits, I start my engine.

 

You'll be upgrading that pump once the Smarty arrieve's!