Well have appointment with dealer Monday , After finally installing westach electric fuel pressure I was pleased to see 16psi at idle and on full throtle only dipped to 10 ,but while cruising gauge will fluctuate between10 and 8 and at times 4-2 and even zero but will return to 10 , Put my foot in it 10 psi
go back to idle a rock solid 15. So any thoughts Bad lift pump? Why only while cruising

 

what kind of guage??
mechanical or electric??

 

electric 0-30 psi gauge
while cruising yesterday I ran wot for a while and after that gauge seemed to be better. Drove home from work this morning fluttering at 0 and below while cruising 65mph
2100 rpm , put my foot to the floor pressure will jump right back to 10psi. Tried bleeding line in case that was it but no better after another test drive.

 

May want to check pressures with a mechanical gauge, just to verify.
my 0.000002

 

How did you attach the sender? I've got an electrical FP gauge on mine and it is steady 19.6 at idle and 13.2 at WOT (Holley Black pump). I've got the sender mounted on a 12" piece of grease gun hose. It screws into a replacement banjo fitting that replaces a shcrader valve on the VP44. Some have said that if you mount the sender directly on the VP44, it will give wild readings from the pulsations of the VP44. I'd also see if you couldn't get another sender.

 

Well dealer didnt even look at , Service advisor said if it starts and runs lift pump not bad. If things get worse there is another dealer just as close to home as purchasing dealership. But now the strange part , after a good towing trip readings are now stable no flucuating at all. ????
I had tried all connections , bled air out , everything and to no avail. So I'm at a loss but all's well that end's well

 

Even if the lift pump is dead, the truck will still run. I've seen it before. Heck, at WOT on my lift pump, I had 0 psi and my truck still ran like a scalded dog. I'd take the truck back and make them check the FP. It doesn't cost them a dime and it only takes 5 minutes. If they still won't do it, take it somewhere else.

 

I agree with BigBlue on both issues, the truck will still run fine, for a while, with out pressure and check your sending unit mounting location. I have mine mounted on a home made bracket off of one of the intake manifold bolts. I run between 16 (idle) and 13 (WOT) psi consistantly.