I recently installed a mechanical fuel pressure gauge (Westach), tapped the banjo off the VP used a snubber hose with a needle valve. I am pleased with the readings 10#min. 13#max. My question: When I shut the engine down How long should it take for my fuel pressure gauge to drop to 0? My pressure drops in about 5 to 10 secs. I would think that this line should stay pressurized longer than that??????. Im battling a recurring loss of prime problem, and Im wondering if the fuel is draining back down the line through the Lift pump. BTW:lift pump is relocated to frame. Thanks Frank

 

The pressure seems correct. The drain back is correct also. The other banjo bolt(return) has a bleed orfice.
I suggest looking very carefully at hose back to tank for vacuum leak. They will absolutelly wear you out. The short hose to VP44 could be replaced with a clear hose (for testing only and make long enough to see easily) and you can see air bubbles if has vacuum leak.

 

Mine is doing the same thing. As soon as my lift pump is off the pressure drops. I thought it was normal.

 

Hmmm, Mine to. Althought I have more pressure (close to 20 at idle) it drops town to 4-5 psi in 5-10 seconds and the rest of the way in another few. My gauge is post filter and pre vp44. I don't seem to be having any prime issues.
Should it really hold pressure after the ignition is off? I thought the return line should be as pressure free as possible.?.

 

If I may clarify one point. When I said shut down the engine, I flipped the key to Acc. the lift pump was not running but the sender still had elec. power to it. Another question: If its normal for the "feed" side of the fuel system to drain back, would my problem be on the "return" side, between the VP and the tank? There is absolutely NO fuel leakage or staining anywhere. I have tried all the commn fixes; fuel overflow valve on VP, new fuel tank cap, double hose clamps, the list goes on. Im getting ready to go down and buy new Banjo bolt gaskets. Ill try anything. Thanks Frank

 

The LP has a one way valve in it, so it should drain forward into the return line and back to the tank - right? If it held pressure I would be worried about a restriction on the return line, in my opinion. I will admit, I am guessing here.

Junkman - maybe the LP one way valve is shot and letting the fuel drain back via the supply line. Just a wild guess, but isn't that what keeps these things going? LOL

 

Following up on MikeBC s thoughts, I went out unplugged the hose from the outlet of the lift pump. Results: dry fuel hose, I attached a short length of Neoprene to the fitting and was able to blow air, by mouth, into the tank, which I could hear the gurgling. This was a NAPA pump which I replaced 2 yrs ago. If its a certainty that the lift pump should have a one way valve, I think I found my problem. If anyone else with knowledge of this could chime in I would appreciate it. Thanks Again Frank

 

Hey Frank, glad to hear my mindless thoughts might have helped. I can for sure tell you this, my new airtex does have a one way valve. The airtex is the pump autozone now carries vs the carter. I think the carter isn't supposed to let fuel go either way when off. I bet you just found your problem.

 

Mike: Did you wire your Airtex directly into the stock Lift pump harness? Will that harness carry the load of an Airtex or my second choice, Holly Blue? I checked with NAPA and my Carter is out of warranty, so Im not throwing any more money away on Carter junk. My plan is to throw away the Carter and replace it with a new one in the same place(frame Rail next to the tank). Frank

 

The airtex uses the smae wiring harness as the stock carter. If you're mounting it on the frame rail you'll need to either make an adaptor fitting, or get one from Eric @ Vulcan. I've been running mine on the frame for about 5000 miles now and I'm very happy with it.

 

Yep, it plugs right in, and the plug was over a foot long, might reach the frame if you go close. I had to zip tie mine up so it didn't hang down.