My setup was on a 1993 7.3 factory turbo. The concepts and methods will apply to any mechanically fuel injected vehicle, whether an old Volvo gasser sedan, a Rabbit Diesel, or N/A 6.9/7.3.
Supplies:
1) Clear vinyl tubing, obtained from your local hardware store. Food grade vinyl is fine, this is a temporary set-up. If you want permanent clear line, get fuel rated or bio-fuel rated inexpensively at McMaster-Carr. My size is 1/4" ID.
2) hose clamps, 7/16".
For my test, I connected:
a) from my electric lift pump to the filter housing
b) from the filter housing to the #1 return cap
c) from the IP to #2 return cap
d) from the #8 cap to the tank return.
Make sure the vinyl is pushed all the way on and the clamps are tight, or you *will* get air leaks back from the vinyl connections which kills any chance of this test helping you.
Clear Line Test Filter to #1 Description: Line from filter housing to cap #1. It is looped to catch air bubbles, which allows one to view the travel of bubbles to identify the source of bubbles. The fitting on the filter header contains a check valve, which is a small glass or hard plastic ball and a tiny spring. The ball is against the housing, the spring is in the barbed fitting. This prevents fuel from traveling back to the tanks from the filter side, and allows excess fuel to run from the filter through the return lines back to the tank while running. This design also allows an electric lift pump to push air out of the return lines before I start the truck.
If one sees air from the filter housing there are several leak areas to check, including a bad check valve, holes in the fuel hard lines from the tank, seals at the housing for the fuel heater, filter, or drain. You can see a big air bubble at the top. That bubble didn't travel or expand during the test, so I consider it a pass. (Keep in mind that replacing a line, even to do this test, introduces some air into the system at first.)
Fuel Clear line #8 to tank return Description: This hose is running from #8 to the tank. Air coming up from the line behind the block (tank return) indicates possible damage to the hard line running to the tank. Air coming from the #8 cap indicates a leak at a cap.
Clear Line Test Pump to Filter housing Description: This was a new pump installation, so I wanted to verify my lines from the tank were good, in addition to verifying the pump was good. Notice the big loop to trap any air bubbles, again.
Clear Line Test Filter to #1
This is showing a lot of air bubbles. In this case, the bubbles were because I had just installed the clear lines. In reality, there were no air leaks at the pump or filter housing.
Clear Line Test IP to #2 cap Description: This verifies the pump seals aren't leaking, and also verifies the pump hard line from the filter to the pump isn't leaking. Air coming from the #2 cap, once again, indicates a leak at the cap. The first cap is gray in color, and is a factory cap. It's dull, dry. The second cap (behind it) is black and is a new cap off ebay. It is wet around the top, indicating a fuel leak. Air will get in there for sure. Don't try to cheap out on return line/cap kits. I ended up buying ford o-rings and caps after this cheap cap failed so badly. I have heard there are several better places to get the kits, but I needed to fix this right away. There is a huge air bubble from the pump side, this went away after a while of running, and was due to the swap to clear lines for this test. What one is looking for is NEW air being introduced after getting rid of or monitoring existing air in the lines.
I tried to embed my photos, but it didn't go so well. When I finally figured out how to make it work, I maxed at 4. So I gave up and put a photobucket link.
Useful info, many thanks for sharing. I'm about to hunt down an air intrusion problem the days after Thanksgiving if the weather holds. Curious... what kind of electric lift pump is that, and where did you get it?
Useful info, many thanks for sharing. I'm about to hunt down an air intrusion problem the days after Thanksgiving if the weather holds. Curious... what kind of electric lift pump is that, and where did you get it?
Thank you, sir, for the compliment.
It is a Facet Duralift 40223, the same one that ThermoKing uses on their trailers. I purchased from Yacht Supply Depot.com for around $100.
Pricey, only have about 2000 miles on it, but so far so good.
the same one that ThermoKing uses on their trailers
It ought to have enough lift for my application. I have a generator with a Kubota engine that has trouble lifting fuel from the belly tank when winter hits. It's about 5' from the base of the tank to the inlet of the IP, and there's a filter on the suction line. It runs fine in summer and will start right away in winter, but if you don't slow idle it for for 5 minutes before winding the governor up to operating speed it will die after about 30 seconds, then start hard. Renders it useless in an automatic application. I've thought about adding a timer and actuator on the governor lever, but it requires more pull and stroke than a typical solenoid can provide. I've tried heating the fuel in the filter and lines, that gives me a little longer initial run time, but once cold fuel from the tank hits the filter she dies, so I'm thinking a little force-feeding would help. 5' is a long way for the IP alone to draft, especially through a filter.
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