I have a problem where I can bleed all the air out of my fuel line for the sending unit on my fuel pressure gauge & the gauge will do well for a about a day......

After I park the truck & use it the next day the gauge seems to start going crazy bouncing back between 10 - 14psi. I'm pretty sure it must be because air is in the line cause I can bleed it & it will do fine for another day.

Is there anything that you're supposed to do to keep this from happening or is there something else causing the gauge to go crazy?.....

I've seen where some sending units are supposed to be mounted vertical.....I'm using an ISSPRO fuel pressure gauge......Can this cause problems like crazy readings on fuel pressure?........

Thanks for any help you guys can give.....

 

Do you have an isolator installed?
If so they seem to cause the problem you describe.
Solution is to remove it.

 

Hi,

The only thing I'm using to hook up to the sending unit is a Vulcan universal fuel line. I have the sending unit attached directly into the line using the fittings they supplied. ( http://www.genosgarage.com/installat...ANFuelLine.pdf ) I asked Geno's about needing a snubber but they say it's not necessary because the Vulcan fuel line has one built in? I don't have an isolator installed though. Only using fuel line.

It's just weird how it does fine after clearing the line but after letting it sit for a while & starting the gauge will start bouncing around again.....

 

Try positioning the sender lower than where it's attached to the fuel system with the hose all running downhill.
This way it should vent air on it's own.
If air still gets in you have a leak somewhere.
Very common for a fuel line leak to suck air but not leak fuel.

 

Thank. I appreciate it. I will try that and see how it does.

 

Wow....I'm starting to run out of options here.....

I re-did the whole thing....re-routed the fuel line all down hill from the VP-44 & the sending unit well below the VP-44. Cleared the fuel line & made sure there is no air in it.......

Same thing going on.....Gauge does well the first few times the truck is driven. Fuel pressure gauge is getting correct readings at first.....Things start to get worse from there & gauge starts bouncing & jumping all over the place after a few times driving it......Starting to get frustrated with the thing......

I emailed Geno's to see if they might have encountered the problems like this with these gauges.........

 

I'm using the same line kit for my GlowShift FP gauge. I used a WeatherHead Needle Valve 6820 from NAPA $8 and connected that to my sender and just crack the needle valve and have rock steady reading all the time. If that don't work your sender might be bad.

 

I just had the same problem and ended up replacing the sending unit yesterday.Now it works perfect.

 

Thanks, I probably need to get one of these & try it to see if it helps. I don't have a NAPA locally so I will probably have to try to order one. I'm starting to wonder about the sending unit possibly being bad too.....

The thing seems to do just fine the first two to three times driving it.....but it just gets worse as you drive it.....gauge bounces all over between 10-20psi......

 

Hi,

I was just wondering if you happened to be using an ISSPRO gauge and sending unit that you were having problems with?

 

Hi,

The only place I could find that valve Weatherhead 6820 was on ebay.....Is the the right valve that I need to get? This the one that you're using?

http://cgi.ebay.com/Weatherhead-6820...3286.m20.l1116

Thanks for the help....

Mike

 

I'm sorry, my bad! WeatherHead 6820. Thats it. Just make sure it don't leak from the needle nut, if it does give it a slight turn, too much it won't stop leaking!

 

This is the one I use http://www.grainger.com/Grainger/items/6MN31

 

Well.....I Should have listened to your advice in the beginning......

The needle valve did the trick & got the fuel pressure readings stable......

I was really surprised though that you only have to barely barely open the valve to get a good pressure reading......anything past barely opening it would just cause the gauge to start bouncing around again.....

Thanks for the advice.....The valve seemed to do the trick.

 

With a sender its always important to make sure you have a good ground for the guage - scrape paint if you have to.