I just installed a new ISSPRO mech gauge, used a needle valve on the top of the filter canister with a 200psi fuel rated hose direct to the gauge. First starting the truck the psi went to 10 psi and then dropped to 4psi, as soon as I hit the go pedal it dropped to 0. This was yesterday. NOTE: lift pump is only 6 moths old. Today when I started it, the psi went to 15 and then dropped to 5 when I hit the go pedal. I'm thinking that I have some air in the line and it is causing the problem. Does this sound right?

The fuel line is run under the power steering, through the firewall, down behind the brake and gas pedal, then the gauge sits just in front of the 4x4 shift lever.

Is there a way that I'm not aware of that I can bleed the air out of the line with out leaking diesel all over the inside of the cab?

I would be greatful for any help given.

Thanks

 

Air in the line shouldn't really affect the readings.

I'd say your lift pump is bad, probably was bad out of the box as more than should be have been.


phox

 

phox,

Hopefully this weekend I will be able to test it with another gauge. The LP wansn't bad out of the box, I have been barrowing my father-in-laws gauge to do once a month tests to make sure it wasn't going bad. It has always shown good readings with his gauge. I last tested it about three weeks ago.

Is it normal to have the gauge spike to 15psi and then drop? I'm wondering if I got a bad gauge out of the box.

 

I would say that you have a lift pump on the way out. Readings can be crazy at times. One minute they are fine, the next they are way down the scale.

 

I agree with the rest of the group...

The LP is going south.... And as for air in the lines... It don't make any difference if you bleed the air off or don't...

 

Air in the lines will not affect the guage much, if at all. You said you tested it occasionally with another guage before you got the full time guage. How did you test the pressure then? If it was at idle with the hood popped open you only get one pressure, the idle pressure. You need to get three readings to determine a bad lift pump. One at idle, cruising speed, and at WOT. The WOT is the most important as it will put the most "load" on the lift pump.

My lift pump is goig dead. I used to test it at idle with a guage and thought it was good (12 psi). When I put in my FP guage I got these readings

IDLE 11-12 psi
CRUISE 6-8 psi
WOT 3psi

Mine is going dead, I am waiting for the new one to show up at my door.

BTW the pressure should never fall below 10 psi. 14-15 is ideal but never below 10. Use that as the baseline to determine a bad pump.

 

roughly 3 weeks ago it read:
IDLE: 13-14
Cruise: 8
WOT: 6

Not good but not bad. When the pump was new the numbers were only 1 psi higher. The gauge I was using goes to 90 psi so it is not real accurate, but it worked.

Just found out that my current LP pump is a month 1/2 out of warranty

Thats just my luck.

 

Of course.
They put time release gel in them.
1 month out of warranty it releases.

Same thing with TV's, VCR's.

If you buy the extended warranty, they give you the "special" box which doesn't have the gel, thus it doesn't break when the others do, and you never use the extended warranty.



phox

 

Update:

Last night I slipped in my original stock LP that has 120,000 miles on it and the psi is reading 12, 9, 6.

What do I have to do to get another pump like this one, it lasted 120,000 miles and until I get another one a few more.

Like I said above the previous pump lasted me just over a year and les than 12,000 miles

 

Mine is going bad too

Going to Dodge Tuesday

Only getting 9-10 @ idle

7.5-8.5 cruising

As low as 4 PSI WOT

 

Be careful proclaiming minimum pressures. They are only opinions and everyone has them. 10psi as a prescribed minimum is very high for a MINIMUM. I know lots of other guys who prescribe their own personal minimums in the single digits and have been just fine. Heat seems to be the biggest killer of VPs... not minimum pressure. Tons of research on the topic regarding what creates pressure and what the VP needs as far as flow (GPH). I personally am comfortable with a WOT pressure in the 5-6 neighborhood.

Steve

 

Low pressure for the lift pump isn't as big a deal as low pressure for the injector pump. Anything under 10 is slowly killing it. It needs the fuel pressure for proper lubrication.

Scrap the stock set up. Chrysler knows it's bad and won't do anything about it.

I have the Air Dog system, the same IssPro gauge, ( a new injector pump ) and I idle at 17 psi and haven't got the guage below 14 psi yet. And I have tried.

 

kyot,

can you send me some info on your Air Dog System? I'm interested.

email me at guru98@gmail.com