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Thread: 1995 6.5L electric fuel pump/oil pressure sender circuit

  1. #1
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    Default 1995 6.5L electric fuel pump/oil pressure sender circuit

    Hello all-
    I just picked up a 1995 6.5 diesel, 1/2 ton, non-turbo diesel. It is a pretty sharp old truck and thought it was kinda somthing different since it had the non-turbo diesel engine. Anyways..., it has some issues that I have been straightening out, but had a question regarding the oil pressure sender circuit that energizes the electric fuel transfer pump. I remember on some of the later 6.2 diesels, people would do a conversion that would make it so the fuel pump would run whenever the keyswitch is on, rather than waiting for oil pressure to build and engergize the fuel pump. Does anybody out there know for sure which color of wire and where it is located so I can try this conversion (i am aware of the liablity/safety issue involved in doing this conversion). I would like to see if it would make any difference. Thank you in advance!!
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    Last edited by ccole; 10-20-2007 at 17:49. Reason: add pic
    ** ccole **
    Past Rides: 1978 Chevy 5.7 Dsl; 1982 C-20 6.2L Dsl; 1984 Chevy 6.2 Dsl; 1986 Suburban 6.2L Dsl; 1989 K2500 6.2L Dsl; 1994 F250 7.3L; (2) 1997 F250 7.3L; 2004 Duramax; 2005 Duramax; 2006 Duramax; 2007 Duramax; 1995 6.5 Non-Turbo; 1994 6.5 Turbo; 2001 F350 7.3L, 2005 GMC Duramax (Current)

  2. #2
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  3. #3
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    Default

    Jim- Thanks for the reply. Do you happen to know where a good location is for energizing the wire that energizes the electric fuel pump? I was thinking on the later 6.2's, there was a wire on the of the glowplug controller harness (near the rear of the engine) that worked well. Thank you
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    ** ccole **
    Past Rides: 1978 Chevy 5.7 Dsl; 1982 C-20 6.2L Dsl; 1984 Chevy 6.2 Dsl; 1986 Suburban 6.2L Dsl; 1989 K2500 6.2L Dsl; 1994 F250 7.3L; (2) 1997 F250 7.3L; 2004 Duramax; 2005 Duramax; 2006 Duramax; 2007 Duramax; 1995 6.5 Non-Turbo; 1994 6.5 Turbo; 2001 F350 7.3L, 2005 GMC Duramax (Current)

  4. #4
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    Default 1995 6.5L electric fuel pump/oil pressure circuit

    You should be able to energize the circuit by jumping from the large hot 'lug' located under the hood at the fuse box there. The cuirit / fuse is located there also, can't remembver the exact location , but it is labeled / in owners manual. My truck is also a '95 ( Turbo but shouldn't be diffrent.) I installed a relay from Kennedy to power the lift pump and it has it's own 'switch' to energize / prime the pump / fitler .
    '95 GMC K2500, "Bullet"Ex. cab short.4X4, 377,000kl on truck, 177,000kl on AMG engine, auto. 3:73 Ltd. slip, FSD remote mount, OPS relay,AFE air IN, Kennedy 3 1/2" OUT . '83 F250 HD3/4 " Robert The Red Ford"4x4 460, 3:55'posi . 2005 GMC : G WHIZ" crew short box, 5.3, 4:10. , '88 Bronco II 4X4, '95 141,000kl Ford F150 EX. short box, '92 "Toy" 4 runner 273000kl ,'63 Mercury 45000miles !!!! Auto insurance co. is my mistress !!!

  5. #5
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    Default

    Quote Originally Posted by More Power View Post
    The two wires used for the lift pump circuit are gray & black.

    Nice looking truck!

    Jim
    Jim- Is one of these (grey or black) wires located on top of the Oil Pressure Sender that can be energized for the fuel pump? Thank you
    ** ccole **
    Past Rides: 1978 Chevy 5.7 Dsl; 1982 C-20 6.2L Dsl; 1984 Chevy 6.2 Dsl; 1986 Suburban 6.2L Dsl; 1989 K2500 6.2L Dsl; 1994 F250 7.3L; (2) 1997 F250 7.3L; 2004 Duramax; 2005 Duramax; 2006 Duramax; 2007 Duramax; 1995 6.5 Non-Turbo; 1994 6.5 Turbo; 2001 F350 7.3L, 2005 GMC Duramax (Current)

  6. #6
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    Default

    There's no need. The lift pump is powered by the pump relay while the starter is cranking and by the oil pressure switch while the engine is running.

    If you insist, the red wire in the ALDL connector goes straight (unfused) to the lift pump.
    The Constitution needs to be re-read, not re-written!

    If you can't handle Dr. Seuss, how will you handle real life?

    Current oil burners: MB GLK250 BlueTEC, John Deere X758
    New ride: MB GLS450 - most stately
    Gone but not forgotten: '87 F350 7.3, '93 C2500 6.5, '95 K2500 6.5, '06 K2500HD 6.6, '90 MB 350SDL, Kubota 7510

  7. #7
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    Default

    On the OPS, the wires for the lift pump are orange and gray. The orange wire is always hot (key on and off). The gray wire is the output of switch. So, neither of these will work for an ignition source.

    The pink wire on the FSD connector and the pink wire on the fuel shut-off solenoid are hot when the key is in the run/start position.

    I would encourage you to not permanently power the lift pump this way (whenever the key is in the run/start position). I have not seen or heard of a 6.5 burning down after an accident, but a high school classmate of mine lost his life in a fuel fire following an accident. In his case, he was a passenger in a 1955 Chevy that was running a 409 with dual quads..... and an electric lift pump.... A carburetor cracked on impact, and fed fuel onto the hot engine for several minutes. Bad, bad situation.....

    Jim
    Last edited by More Power; 10-22-2007 at 15:47.

  8. #8
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    I just wanted to say thanks for all the very informational replies. Also, Jim-- thank you for the "heads up" regarding the danger involved with a bypassed lift pump. My sole purpose of wanting to know how to do this is for testing purposes and for re-priming after repairs/fuel filter changes/etc. Thank you....
    ** ccole **
    Past Rides: 1978 Chevy 5.7 Dsl; 1982 C-20 6.2L Dsl; 1984 Chevy 6.2 Dsl; 1986 Suburban 6.2L Dsl; 1989 K2500 6.2L Dsl; 1994 F250 7.3L; (2) 1997 F250 7.3L; 2004 Duramax; 2005 Duramax; 2006 Duramax; 2007 Duramax; 1995 6.5 Non-Turbo; 1994 6.5 Turbo; 2001 F350 7.3L, 2005 GMC Duramax (Current)

  9. #9
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    Post Here's another trick

    Quote Originally Posted by ccole View Post
    I just wanted to say thanks for all the very informational replies. Also, Jim-- thank you for the "heads up" regarding the danger involved with a bypassed lift pump. My sole purpose of wanting to know how to do this is for testing purposes and for re-priming after repairs/fuel filter changes/etc. Thank you....
    As for repriming the filter, I believe you can put the Drive Selector in "D", then turn the ignition key to start position. The starter will not crank, but the lift pump circuit will be energized while key is in crank position. If this works, you will be able to hear the fuel pump chattering when energized.

    Yet another way is to pull the fuel pump relay in the under-hood fuse box. You can then jumper across the open contact terminals positions in the fuse block to run the fuel pump. I could take a pic of how to do this, if you'd like to see how it's done.
    2016 GMC SLT 2500 CC 4x4 Duramax All Terrain 59K
    1995 GMC 2500 EC 4x4 6.5TD,236K,Custom Tuning,HX40W-II turbo,Amsoil Bypass Filter,KD Exhaust,FSD Cooler,KD Headlight booster,Hi-cap Cooling
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  10. #10
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    Default

    Good Day!

    "My sole purpose of wanting to know how to do this is for testing purposes and for re-priming after repairs/fuel filter changes/etc."

    "I believe you can put the Drive Selector in "D", then turn the ignition key to start position. The starter will not crank, but the lift pump circuit will be energized while key is in crank position." You are correct! You are the lucky owner of a 95 - this is the ONLY year truck this works on. (You may note that I'm the lucky owner of TWO 95s - a coincidence. I sure didn't buy them for this feature. )

    Actually, If you put the gear selector in any position EXCEPT park or neutral, when you turn the key to the "crank" position, the lift pump will be powered through the above-mentioned cranking LP relay circuit, but the engine won't crank. This is VERY handy. It allows you to prime the fuel system, & check everything in the LP system except of course the OPS.

    Blessings!
    82 6.2NA K15 4X4 pickup, 4spd man w/ OD, 335K+ "In Rust We Trust" (parked)
    95 6.5TD 2500 4X4 pickup, Gear Vendors Aux. OD, > ¼ million miles - gone
    95 6.5TD 1500 4X4 3/4T Suburban, Kennedy exhaust, > ¼ million miles
    93 6.5TD 3500 4X4 1T crew cab LB pickup, 230k miles

  11. #11
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    Arrow

    The "out of P/N and crank" trick is unique to 1995 models. Some late 94's would do it, but no rhyme or reason to the build dates. True that. Very handy.

    If it pumps during this process, and doesn't pump with engine running, you can pretty much conclude any problem to the OPS circuit. Not that they would ever fail......
    1985 Blazer 6.2
    2001 GMC 2500HD D/A
    dmaxmaverick@thedieselpage.com

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