i keep losing prime

junior20762003

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can somebody help me out i already replaced all the fuel return lines and o rings with caps and cooper fittings on my injectors and im still losing prime:mad: any help would be apriciated thanks ;Sweet
 

Brianedwardss

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If you have a 7.3L, on you filter head is a small check valve. It's what the return line clamps onto on the engine side of the filter head. Unclamp the return line, then take a wrench or socket and remove the brass fitting from the filter head. If you can see light through it, it's bad. It's not unusual for this to happen with this new diesel fuel we have to burn.

I'll look the part number up in a bit. It runs $20-$30
 
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Brianedwardss

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'91 is the changeover year for check-valve size. 7.3l's from '88 to '91 had a 3/16" check valve, but late '91 and up had a 1/4" check valve. I'm not 100% sure, but I'd guess that you measure the return hose size that's clamped to it.

Part Numbers:

Early 3/16" check valves: E8TZ9K061A
Later 1/4" check valves: E9TZ9K061A

A little ways down this page on Oregon Fuel Injection, you can order 'em:

http://www.o-f-i.com/index.php?pid=12#FUEL_&_OIL_FILTERS_O.E.
 

Brianedwardss

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junior20762003

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like this
 

junior20762003

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ok when i removed the line there was no fuel would this cause this too happen as well as no fuel on passenger return lines either but the driver side has fuel in the return line
 

Brianedwardss

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The check valve keeps air out of the filter head, which is the supply side of the fuel system. As long as the supply/pressure side of the fuel system is sealed off from air, things stay happy. The check valve is an important piece in keeping the prime
 
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junior20762003

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so your saying my check vavle isnt holding pressure thats why im loosing prime so for sure the check vavle is the issue
 

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