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6.5L Diesel Engine Discuss the 6.5 GM diesel engine & associated components. Automatic transmission questions & problems belong in the 4L80/85 - 4L60E - 6L90 Transmission Forum

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Old 07-12-2019, 04:37 PM   #1 (permalink)
bigred1957
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Location: Hudson Colorado
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Crank sensor fault/ glow plug relay fault. Acts scarey! Help!

Hey folks, getting better with understanding my 6.5l, forum usage not so much. Couldn't find a similar situation here so here goes. Truck runs great finally, but recently it had a new issue. After 30-40 miles, engine at operating temp. Check engine light comes on but not much change mostly. However a sporadic run away short surge may occur. Freaked me out! Last time I was behind a motorcycle at a stop light when it happened. He gave me a dirty look like I was being impatient, I thought I was going to run him down (auto trans)! Freaked out it could turn into a more serious runaway problem! Pulled crank sensor fault code and glow plug relay fault code. Recently replaced the entire glow circuit with heavier setup from a quality guy on here making harnesses so I trust that totally. Have no idea where the crank sensor is at the moment but folks talk about stalling and hard to start, neither which is an issue for me, yet. It's a 94 k1500 w/4l80E. No major mods but ops relay mod, heavier gp harness, fuel filter relocation, and pmd relocated behind the grill. Please help!

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1994 Chevy K1500 4X4 6.5l Turbo and 4L80E trans.
Mods so far include:
--Marine injectors--Clear fuel return line
--PMD relocated to behind the grill
--FFM relocated to the drivers side wheel well
--Air bags for towing my home.
--Leroy Diesel stainless oil cooler lines
--FFM extension harness by Glagulator
--HD GP harness by Glagulator--AC Delco 60G gp
--Ops mod harness by Glagulator
6.5 haters are dumb

Last edited by OkDually; 07-12-2019 at 04:57 PM. Reason: sig
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Old 07-12-2019, 05:03 PM   #2 (permalink)
Glagulator
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Location: Very south TEXAS, Formerly Wisconsin
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What were the code #'s you got?
Engine running in park, can you hold the rpm's steady at 2000 rpm?

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There are 10 kinds of people in this world; Those who understand binary and those who don't.

99 CREW LONG SRW C3500 work truck 199k+ mi. orig. motor & trans 4.10, modded engine harness, new oil cooler & lines, all new front end parts and poly bushings, trans poly mount, all new brakes.
96 SUBURBAN K2500 wife's truck 210k+ mi. orig. motor & trans, 3.73...
95 C2500 Suburban 6.5td HO w/p, timing set, HB & pulley, all rubber hoses, modded engine & main harness, converted to OBD2, PMD to bumper...
95 C1500 Suburban 6.5td rebuild tranny, convert to DB2, replacing as many parts as I can.
96 C2500 Suburban 7.4L converting to 6.5td w/ DB2, 4L80, 3.73
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Old 07-12-2019, 06:58 PM   #3 (permalink)
bigred1957
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I got a 19 and 29. Thankfully that was all. Yeah it holds rpm nicely. One thing I forgot to mention is that when I get where I'm going and shut it off for day 15 minutes the check engine light goes off. If the engine is warm it will come back on shortly. I can run errands aground town and it won't com on but 10-15 minutes down the highway it will come on again. After that the surge could happen while driving or sitting. Hasn't done it in park yet though. Not yet anyway.
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Old 07-13-2019, 01:26 PM   #4 (permalink)
JMJNet
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The Suburban Club Member

Crank Sensor is on the driver side, attach to the timing chain housing.
The connector snake up behind the tensioner spring.

Theoretically, it should be easy to change but chances are you will not be able to pull it easy.
I had to take off the PS pump (set it aside) and alternator to have better access to work on getting something that can pull the part out.

There is a picture of the part here somewhere in the FAQ.

Edit: This is from the FAQ, that is the red section. You need to get to the website by using dieselplace.com instead of google and then go to 6.5L section. Click the link that say FAQ. Once you are in that website, do CTRL-F and enter "CPS".

https://www.dieselplace.com/forum/63...ml#post7219970
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1995 GMC Suburban:
PMD in Bumper
Leroy Diesel Flight System PMD
Leroy Diesel Oil Cooler Line
4" Warpspeed Exhaust
Kennedy Diesel LP/OPS Harness
Bosch Duraterm GP
Heath Turbo-Master
AD244 Alternator

Last edited by JMJNet; 07-13-2019 at 01:41 PM.
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Old 07-13-2019, 02:47 PM   #5 (permalink)
bigred1957
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Fantastic, thank you JMJNet! I've been reading that it seems to break off easily, is this so? Ordered a new sensor so I will reply when I get-er-don.
Mainly was feeling out the opinions if the CPS fault and GPR fault may have a connection to the problem. Got to thinking I've never cleared codes so the relay fault may be prior to my work doin on it.
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Old 07-15-2019, 01:42 PM   #6 (permalink)
Glagulator
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Join Date: May 2005
Location: Very south TEXAS, Formerly Wisconsin
Posts: 3,738
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Do you have PM's blocked?

Thanks for that, glad your getting it running well.

If you are getting a occasional "rump, rump, rump", like if you were popping the throttle, then that is a known problem and nobody has figured out what causes it. Every 6.5 I have owned has done it, some worse than others. My 94 was the worst, newer models seem to do it mostly when shifting into reverse.

The CPS usually will not come out due to dirt and crap that collects above the O-rings and jambs the sensor in the hole. Soak it good with wd40 to loosen up the crap and corrosion just below the hold down bracket in the hole. If everything breaks off then drill a hole in the center and run in a screw to jerk it out. Moving the P/S pump out of the way helps a lot. The replacement CPS should have a longer pigtail than the old CPS if it was the original.
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There are 10 kinds of people in this world; Those who understand binary and those who don't.

99 CREW LONG SRW C3500 work truck 199k+ mi. orig. motor & trans 4.10, modded engine harness, new oil cooler & lines, all new front end parts and poly bushings, trans poly mount, all new brakes.
96 SUBURBAN K2500 wife's truck 210k+ mi. orig. motor & trans, 3.73...
95 C2500 Suburban 6.5td HO w/p, timing set, HB & pulley, all rubber hoses, modded engine & main harness, converted to OBD2, PMD to bumper...
95 C1500 Suburban 6.5td rebuild tranny, convert to DB2, replacing as many parts as I can.
96 C2500 Suburban 7.4L converting to 6.5td w/ DB2, 4L80, 3.73
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