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ad 150 wierd fuel pressure

643 Views 5 Replies 4 Participants Last post by  demo_fever, 
D
ok i bought the truck and it had 143 thousand on it it now has 155 on it. the vp and lp has been replaced before i got it the lp is a ad150 and the vp is a bosh. i had autometer nv gauges installed right before christmass last year . the truck has allways burried the gauge at 15psi even at wot. about a week ago i started the truck and noticed the fp gauges was jumping from 13 to 14 psi just sitting there. as i drove the truck it would drop up and down and at wot in 4th gear it was reading allmost 11psi. i just replaced both ad filters and also the factory filter on the block and it is still doing the same. i drove the truck today for about 20 miles and the fp gauge was burried like it used to be. then this afternoon i took off and iit was back down again. is ad going south on me. i have check for leaks and cant find any truck is all stock except for a straight pipe. it hasnt lost any power and doesnt smoke any diffrent. any body have ideas thanks a lot
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Had a similar problem with my AD/ Glowshift gauge setup. I originally had no snubber/needle valve on my fuel pressure gauge. It worked fine for a few months but then my gauge started bouncing. it would max out for most of the time. One time during the winter the truck wouldn't start for some reson so i ethered it. Once it started I noticed the fuel pressure was at 0. I did some trouble shooting and found out my relay for the AD was . I made a quick jumper wire to get me home.
When I ordered the new relay I also got some higher pressure springs because my gauge was reading a bit low. After swapping out 2 springs (one was 30 PSI) and noticing my fuel pressure was not changing i decided to order a new sending unit for my gauge. I also went to NAPA and got a needle valve. I installed the new sending unit and snubber valve. That fixed my gauge. Now everything works great.
So make sure your gauge is reading right first. If it is check your fuel pump. It shouldnt sound weak. If it does it could be a corroded connection or loose wire.
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