Engine/Transmission (1998.5 - 2002) Pump Pressure Loss - Replacement Pump

[garylmoore]

I replaced the pump head on my Fass Titanium last week. All seemed well when I drove the truck to work and back, gauge at 16 psi.
I was running errands this afternoon, looked down at the pressure gauge and was reading zero, I was a mile from home so kept driving. A few minutes later, the pressure jumped back to 16.
I checked the pump when I returned back home, shut off the truck and restarted. The pressure came up to 5 psi and the pump sounds normal. Not sure what to think of this.. Am I sucking air somewhere?
I would appreciate all thoughts.
Thanks Gary

 

[BigPapa]

What kind of gauge are you using and are you using a snubber?

 

[garylmoore]

ISS Pro column mounted. I have not had issues before, but I guess I could have air in that line also. I cannot remember for sure, but I believe there was a snubber installed.

 

[petersonj]

You make no mention of engine performance issues, so I am assuming there is none.

I would temporarily install a mechanical gauge with a long length hose and strap the gauge to the driver side wiper arm. Go for a test drive and observe the performance. If gauge performance is normal, then you have a problem with the ISSPRO gauge / sending unit.

If gauge performance is the same, then you will need to look further.

Diagnosing lift pump pressure problems without a known working gauge can lead to wrong conclusions.

- John

 

[Ozymandias]

You are definitely not sucking air, with air the engine would stumble or even die.

 

[garylmoore]

"You make no mention of engine performance issues, so I am assuming there is none."

Yes, no engine problems, my concern was overheating the piston pump due to lack of fuel flow.

 

[garylmoore]

You are definitely not sucking air, with air the engine would stumble or even die.

Thank you Ozmandias..

 

[petersonj]

my concern was overheating the piston pump due to lack of fuel flow.

This is why the first step should be to install a mechanical gauge to prove that the lift pump circuit is or is not working. Then go from there.

If the lift pump circuit is not working properly, we can guide you from there - but, not until it is proven one way or another.

- John

 

[garylmoore]

I never considered the gauge until Big Papa posted, then I thought maybe I had air in the line from the changing the lift pump head.
I pulled the gauge feed line last night, turned on the key and the pump failed to run.
I pulled the pump relay and it had green crusties on the tangs. I will replace it and try again this weekend.

 

[garylmoore]

I will also buy a mechanical gauge and verify my fuel line pressure.

 

[BigPapa]

I will also buy a mechanical gauge and verify my fuel line pressure.

I'd try the relay first.

 

[garylmoore]

Yes, I will Sir...
When I wiped the crud off of the installed mini relay, the specification came off with the crud. It was from the original Fass install kit so I emailed them to be sure of the specs.
That was the first time the pump had failed on startup, thank you for your help BigPapa..
Gary

 

[Ozymandias]

It's a standard relay, you might wanna think of changing it to a sealed unit right now as it has apparently a problem with corrosion where it sits now.
Check Amazon for "sealed automotive relay with base", they go for less then 10$.