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How much fuel should the injectors and pump return?

T

tamohr

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NE INDIANA
Gentlemen, I recently purchased a 95 Suburban that is having hot start issues. I installed a rebuilt injection pump last week and was told by the previous owner that it has marine injectors. Even with all new return lines it keeps blowing them off the injectors. When idling at operating temperature it squirts out so much fuel I cant imagine why any of the return lines would stay on. Do any of you know how much fuel should be returned in ounces per minute or some other measure? THANK YOU!
 
Do you have the little clamps on them? I had a problem with one popping off so I use a zip tie like a clamp. Works great & has not come off since.
 
Burning oil said:
Do you have the little clamps on them? I had a problem with one popping off so I use a zip tie like a clamp. Works great & has not come off since.
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No but I use a high quality fluoroelastomer line that works on my other 6.5 pickups. It just seems like the return volume is too much. Any idea on how much volume to expect?
 
tamohr said:
No but I use a high quality fluoroelastomer line that works on my other 6.5 pickups. It just seems like the return volume is too much. Any idea on how much volume to expect?
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I've never measured the return. If the truck runs fine otherwise I'd just get some of the clamps. Auto parts will have in the help section. Or I have them also.
 
I'd check the return line for restrictions... I pinched mine above the tank when I changed the sending unit. When I blew the first line off I was pretty mad at the guy who sold me these "crap clamp less lines" and let my driveway know it. After the second line blew off I realized what I did... And took back all of the mean words and bad things I said about him and his product :)
 
If its returning a LOT of fuel, that fuel is bypassing the needle in nozzle body. The governer really shouldnt be an issue here. I would think the problem is in the nozzle(s).

-c-
 
Common, internal cracked injector body, nozzle body or excessive nozzle clearance rises fuel return pressures to the point of popping the hoses off.
 
The following images of the 6.5td stock Bosch injector show the high pressure "pop" circuit and the low pressure fuel return circuit inside the body.

6.5 td injector 002.jpg This image is the top of the injector upside down showing the high pressure port on the outside edge and crack in this port will rise fuel return pressure to pop pressure.

6.5 td injector 003.jpg This image shows high pressure port to injector nozzle any crack in this port will rise fuel return pressure to pop pressure.

6.5 td injector 004.jpg This image shows high pressure port at bottom that sits on the nozzle high pressure fuel flows through here to pop nozzle again any racks and fuel return pressure will reach pop pressure.

6.5 td injector 005.jpg This image shows the high pressure port and the nozzle after popping the fuel is low pressure returning to the injector top fuel returns from the center of injector nozzle to the low fuel return side.

6.5 td injector 007.jpg This image shows fuel return port inside body there are two of them.

6.5 td injector 008.jpg This image shows injector top upside down and all parts stacked for insertion into the lower injector body.
 
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