I just installed the new FASS titanium 95gpm pump today. While the truck is running the fuel pressure guage bounces back and forth from 10 to 20 psi and it seems like it's in rhythm with the engine. What is making my pressure guage do this? It levels out some when driving. Fuel pressure never drops below 15 psi at WOT. The raptor did something similar but it was more like a vibration in the pressure guage. Air in the pressure gauge line maybe? And I still think the vp is shot. Same symptoms as before. I tried to post a video but it wouldn't work.

Do you have a snubber or needle valve inline with the gauge?

What symptons with the VP44?

 

Ed

Where is the fuel pressure sensor for your EV2's installed at?

 

Most make the mistake of installing right at the VP44. Even with the snubber on it will still destroy the sensor. Like I done to resolve this I got mine remote mounted on the fender to give the water hammer distance to fade to the gauge.

 

http://articles.mopar1973man.com/general-cummins/36-fuel-system/458-electric-fuel-pressure-gauges

I have a needle valve in line and it's probably about 10 inches from the vp. The weird thing about it was when I did the draw straw a couple of weeks ago it was smooth as silk for about an hour then back top the same thing. VP issues include intermittent dead pedal, hard hot starts, codes 216 and 1689. The dead pedal isn't totally dead in that the truck will still accelerate but it's extremely slow acceleration and it seems to happen mostly when coasting and at lower rpms. It never does it if the engine is under load.

Ouch. The limited pedal worries me. That typically points to ECM issues.

 

Could you do a AC voltage test on your alternator? Basically just use a good quality digital volt meter and measure the voltage at the BATT terminal on the alternator. If the voltage is over 0.1 AC volts then the alternator failed.

 

How about the Wait To Start light? Does it come on instantly or does it lag a few seconds?

 

Hot start is typically excessive fuel pressure at start up. Check your cranking pressure it should be bouncing between 7-12 PSI roughly. Anything higher causes hard starting.

Everything works fine as far as wait to start and everything else. I don't have a volt meter being that I'm just a shade tree mechanic, haha. I can do most stuff they is just mechanical and straight forward but all the really technical stuff hems me up. As far as hard starting goes I had the relay grounded to the starter like you told me to do before but I didn't do it with this FASS because I figured if I'm gonna replace the VP I'm not cutting the power wire to the brand new pump. However, even with the relay wired to the starter I was getting hard starts anyway.

Edited January 21, 201510 yr by RubberDuck01

Well good at least the ECM appears to be working correctly then that means one of the errors most likely is the cause of the limp mode.

So do you think the gauge itself is toast?

Can you verify with a second mechanic gauge?

I don't have an extra one at the moment. In still going to take the line of the back of the gauge and see if there's air in it. Just didn't have time to do it today.