Engine/Transmission (1998.5 - 2002) FP behaviour with SPA Gauge

[Shelby Griggs]

I have a 2001. 5 with about 175K on the clock. I have had a SPA dual readout FP and EGT gauge since 2001. I had the FP gauge plumbed pre filter with a stock fuel system.



About 3 weeks ago I installed the Vulcan big hose/relocation kit and because of the large JIC fittings I didn't have room (without additional fittings or hardware) to put the FP sender on the filter input, so moved it to the VP44 input (post filter).



I have OK FP (indicated), but I had to set the Low Pressure point to ZERO and the average up to 5 seconds. It seems there are a lot of spikes, both high and low. The high as captured by the gauge is always in the 30-40 PSI when I check it, usually reset every fill up.



If I didn't put the LP point to ZERO, the LED would flicker occasionally. I was running the Low Pressure point at 5 PSI when the same gauge was mounted pre filter.



Are other users seeing similar behavior? Is an isolator or a remote sender mount in order? Maybe a failing sender unit?



Also does anyone know the operational sequence of the LP? I can hear the pump at idle since I relocated to basically under my seat. The pump sounds as if it is running at variable speeds while idling. Could this possibly be cavitation? Is this a mechanical bypass opening and closing to cause the change in sound?



While overall, my gauge seems to on average indicate adequate FP of usually between 10 and 15 PSI, the real high readings and real low readings concern me. It is possible that a mechanical gauge wouldn't pick up those spikes, but the SPA is sampling at 0. 4 seconds, the display updates at a user selected time interval, in my case the average of 20 readings and then updates the display every 5 seconds.



Any input appreciated.



SHG

 

[kscheffler]

Sounds like you might have air in the line between the vulcan "tee" fitting and the SPA sendor unit. Try to bleed the air out of the line. You might have to do this periodically so I have installed a three way valve prior to the SPA sendor unit. Don't ask me why we get air in their after it is bleed the first time but you will see it perodically since it is a dead line from the main line. Try it and see if it solves your problem

 

[TJSHOTROD]

Mine does the same thing but it only varies from 11 or 12 to 16 or 17.



TJ

 

[BarryG]

I had the experience that Kscheffler had. Mine would start to act erratically like that. I would bleed my fp guage line and it would go away. I seem to have had to do that once or twice a year. Not a big deal but certainly an eye opener when you start seeing low spikes as youa re driving down the road a hundred miles from nowhere.

 

[Shelby Griggs]

Well, maybe it is just air then. There really is no line, I have the sender threaded into the back of a tapped JIC fitting that is attached directly to the VP44.



I do have a small leak someplace near the attachment to the VP44, maybe it is getting some air in there. I can't find the leak, I have taken the sender out twice and resealed the pipe threads, but it is still dripping just enough to make a mess.



SHG

 

[JCyrbok]

Some people have problems with the sender attached directly to a fitting at the VP. The VP has some pretty wide psi flucuations/vibration during operation and senders this close to the VP are known to have problems. Try running a line from the fitting about 18inch to the sender to use as a snubber to absorb the psi flucutations and vibrations. My sender is tee'd into the line from the FASS to the VP about 1. 5 feet from the VP with about 1 foot of line to the sender.



If it was air in the line/sender it should be out in a day or two, providing there is no leak.



Also I have had problems with my SPA EGT/Boost gauage. The electrical connectors are not the best. I cut them off and soildered (sp) them and have had no problems since.



Hope this helps.



J-