I have done a lot of work on the fuel system on my truck and I cannot seem to bleed the air from the supply line of my new ISS PRO gage.
I am also getting an occasional miss at idle that was not there before the:

rebuilt injection pump install,

lift pump install,

and fuel sending unit install.

When replacing the sending unit in the fuel tank, I had a LOT of trouble removing the lines when I dropped the tank. Those hoses took a good stretch in the process and I am thinking that the problem is coming from those lines being damaged.
I have replaced the oring washers between at all banjos.
How do I test the airtightness of the system?
I put a gage on the line right before the injection pump and cranked the motor to get the lift pump to come on, I have 20 lbs. up until the lift pump goes off and then the pressure drops off immediately. I figure to check this I will have to find a way to plug the return line. I really dont think i have a way to plug that line, most of my on hand fittings consist mostly of flare.

I hooked the gage directly to the bottom of the fuel filter which gave me mixed results. I drained the filter housing so as not to make a mess. I accidentally did not get it all the way closed and was able to get 20 lbs reading on the gage. Once I realized that the drain was open (so much for not making a mess) I tried it again and could get no more than 3 lbs on the gage.
I did not understand that at all, thinking I had air in the gage line I broke the connection and made sure there was fuel in the line, still 3 lbs. Could this be the filter huosing filling up again?

Any ideas for me?

thanks...gary

 

i use a dirt devil vacuum to pressurize the tank (hook the hose to the exhaust side of the vacuum) put it in the filler tube of the tank with a rag wrapped around it...if you have any leaks, you should see them as the tank pressurizes

 

not with a home vacuum

 

Looks like I am going to have to use the shop vac, nothing else in the house I can reverse the hose on...
thanks Johnh.
...gary

 

My fuel pressure also drops after the LP stops runing, i did not think that was a bad thing. I bet if you run the truck you will know if you have a air leak. mine seem to run with a miss if i had air in the lines.

 

Use a clear piece of tubing before and after your lift pump. Make it long enough to put a 3 inch hump in it. Put the hump up and start, watch for air.

 

You don't have to bleed the lines of the ISSPro gauge. I run mine direct with no isolator & haven't had a problem.

My fuel pressure goes to 15# measured at the VP input. It drops to 0 after the pump shuts off. Perfectly normal.

My fuel line was leaking at the T fitting at the back of the head where the return lines meet. Easy repair (installed 3 rubber seals that look like 1/4" of fuel line $8 each) with the stock filter removed. Climb under the truck & see if your fuel lines are wet.

 

There has been some great ideas for checking for leaks in the fuel lines given here.

You guys are a great at figuring this stuff out!

The whole thing that started this thread was that I could not stop the wild swings in my fuel pressure gage.

I put the truck back together after the failed attempt to check the fuel pressure and took the truck for a drive. On a fuel stop, I found that I had diesel running off the back of the engine. I eventually found out that even though I had cranked down the injectors after bleeding the air out, that one of them was leaking.

I am not sure if I fixed something when I put it back together or whether it was the loose injector, but the gage quit the wild swings.

I drove the truck to work for the first time friday with nary a hiccup in the run.

After losing an injection pump, lift pump and a fuel sending gage in a short period, I have started regaining confidence in the truck again.

Thanks for the help!

gary