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Discussion Starter #1
1. Describe the problem you are having in detail: Glow plugs wont cycle, can use a jumper wire to get hot enough to fire, can get the truck running usually but it sputters and dies as soon as I give it pedal, then oil pressure drops to 0 and acts like its not getting fuel, did the turn over test and am getting fuel to drain tee, didn’t try after it dies, the weirdest part is that I had a buddy come to tow me home and I decided to try to pop start it and it fired right up, oil pressure went back to normal, I drove it home, I have replaced the ops already but guessed it went tits up again, so I ordered one of the internet and figured I would wait for it to get here, well I got impatient today and went and bought a lifetime warranty one just to see if that’s what the problem was, and sadly It wasn’t, I then decided to try the numerous new backup parts I have including another gp relay, and pmd, with no change in the outcome, ive replaced all the gps and wiring, added extra grounds, replaced pmd w relocation into bumper, new lift pump 4 mo ago, and a bunch more, about over the 6.5 bs, as a company truck I cant afford to break down and that’s what this truck keeps doing to me, just had the front end, t case, and 5 speed trans replaced 2 weeks ago, and now its stuck sitting outside the shop.

2. Year of truck/engine. 1995 6.5 TD
3. Odometer reading 212000
4. Indicate the model number on the Injection pump ds4
5. Indicate if you know if it’s a 1500, 2500, 2500HD, 3500, 3500HD. K2500
6. Do you have an EGR on the engine? (An F or an S engine code 8th VIN digit)
7. Air Filter condition (visual check). New
8. Fuel filter condition (freshly changed, mileage since changed). Lift pump replaced 4 mo ago
9. Location of PMD/FSD? (ex. on pump/remote over intake, behind bumper). New behind bumper
9a. If remote mounted, describe wiring harness (homemade or purchased from which vendor). purchased
9b. Indicate the location and condition of the FSD/IP grounding wire. On IP
10. Outside Temperature (C or F). _____ ° now -14 problem is during warm weather as well

11. Service Engine Light while running?- on/off/intermittent off
11a. Service Engine light does glow during start/cranking/bulb check: Yes
12.Have you scanned for engine codes? Yes/No doesn’t connect
12a. List exact results on engine codes.

13. Condition of Battery terminals (removed, cleaned and tightened). New
14. Known condition and age of Batteries. New
14a. Are batteries a matched set of same age? Yes
15. Condition of Major Grounds (removed, cleaned and tightened) Added grounds everywhere
15a Have the batteries been individually load tested? New

16. Does engine crank, or "turn over"? Yes
16a. Does engine start and run? Sometimes
17. If engine does not start- Crack injector line: do you have fuel? Yes/No havnt tried yet
18. Does your Wait To Start light come on? yes
18a.Number of seconds WTS light is lit. For ½ a second
19. Engine Cranking speed (if you have an accurate tachometer). 200

20. Are you experiencing Stalling? Yes
20a. Describe the event (upon startup only, down the road, hit a bump, etc...) all the above
20b. Do you notice loss of dash or instruments? Just oil pressure guage
21. Check turbo inlet and air filter for obstructions. clear
22. In a no-hot start, pour a bottle of room-temp water on the injection pump. Does it start now? Havnt tried
23. Lift pump test - Describe results. Had fuel at tee while turning over cold

24. Upon cold start, does the radiator hose get hard quickly? Yes/No havnt noticed
25. Upon cold start, do you have excessive white smoke? Yes/No no
26. Do you have excessive cranking time before the engine starts? Yes/No after it stalls yes
27. Have you used the block heater? Does it affect engine starting? (only try for starting problems). Always keep it plugged in
28. Are all glow plugs in proper working order? New

29. During hard acceleration, do you have excessive black smoke? Yes/No no
30. Do you have any unusual exhaust smoke issues? no
31. Turbo check out - Pass/Fail pass
32. Indicate fuel that you are using: Bio-Diesel, #2 Diesel, SVO/WVO, other winter1
32a. If running Veggie Oil fuel setup, indicate details of your conversion (homemade or packaged system).
33. Are you using any fuel additives? If so, please list. Dieselkleen winter additive
34. Upon unscrewing fuel cap, do you have a large vacuum formed in the tank? Yes/No no
35. Do you have any service history available that might pertain to the problem you are having? no
36. Please indicate any modifications to the vehicle that might help us diagnose better. Replaced almost all electrical components, just cant figure it out why it will die and wont crank back over but will pull start
 

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1995 GMC Suburban
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17,737 Posts
Did you replace the OPS with ACDelco brand?

The GP controller/relay is probably bad or the wires are bad.
 

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Discussion Starter #3
replaced with borg warner lifetime warranty, the one i pulled out was a ac delco replacement and the one on the way is ac delco as well which only hold a 1 yr warranty

i can jump the controller and the glow plugs work great, they are all new and so is the wiring, as well as the controller, the weird thing is the work sporadically, most of the time it just clicks on and off, other times it cycles well (8-10 sec) and the truck fires right up
 

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1995 GMC Suburban
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YOU NEED AN ACDELCO OPS.

Based on experience with myself and other members, the non ACDelco (BW, Wells, etc.) are not behaving correctly.

So is the GP controller has to be ACDelco.

BW used to be good but lately has been problematic.

By the way, NEW DOES NOT MEAN IT IS WORKING with this overseas made parts.
 

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Discussion Starter #5
but it still doesnt explain the fueling issue, has a new lift pump, new ops, new filter, additive regularly, i almost think i have a electrical gremlin in it, i jumped the gp relay today and got it running, and let it warm up for 15 min, then i jumped in and deciced to not move it but rather rev it like i was driving down the road, and sure enough after about a min or two it sputtered and died, so i tried a known good pmd and nothing, ive noticed the oil pressure gauge drop to 0 when it all happens, then when i crank it theres no movement in the gauge, but if i pull it in gear it fires right up, batteries are all new including all new connections, cranks over plenty fast, this problem is the newest of a ton of issues, and all of those have been repaired, it just baffels me how one min it doenst read any oil pressure at all the you pull it and it fires right up, and i sat there and cranked on it for 20 min before he showed up, does anyone know where to get a wiring diagram for a 1995 chevy k2500 4x4 ext cab 6.5 td w NV4500 trans? would be much appreciated
 

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When my truck stalls Ive watched fuel pressure gauge, when oil pressure drops after stall, lift pump stops also. Makes sense no oil pressure so off goes pump. Turning key to start does not get lift pump going again, turning key off and then trying to start does get fuel pressure back up again. Something about way PCM is programmed??? I have kennedy OPS kit so relay is turning on my lift pump
 

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I will lay odds you have battery cable issues, check the starter connection. When starter crankc, does the engine sound high pitched or low starter sound...
Especially in cold weather, the starter is very picky about full voltage. Slight voltage liss and crank speed reduces enought to prevent starting. It also weakens the battery connection further and could account for the ops dropping out the pump...


You might try synthetic motor oil... improves crank speed in the cold.
 

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Super Moderator Eco-Logistical
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4,271 Posts
Where do you live?

I will trade you my fully working z71 for your problematic 5 speed powered truck...
 

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Any electrical parts in nature you will need AC/Delco or you will experience Electrical Gremlins.

Replace the Glow Plug Relay.

Go through all of your grounds. Remove each one,clean the contact points and re-install using this link for reference.
http://www.dieselplace.com/forum/63-gm-diesel-engines/21-6-5l-diesel-engine/163087-grounds-grounds-grounds-importance-good-grounds.html

If your glow relay is still not working then read this link.
http://www.dieselplace.com/forum/63-gm-diesel-engines/21-6-5l-diesel-engine/474063-my-glow-plugs-wont-cycle.html#post4750177

And finally, just because you have a "new" lift pump does not mean it's good.
You need to test the lift pump to ensure it's good.

Wiring diagrams can be found here: Wiring Diagram Search Results
 

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1995 GMC Suburban
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On the fuel issue, the OPS runs the LP when engine is running.
This is a separate pin on OPS that controls the LP.

If the OPS is not behaving correctly, the LP is not running as soon as the engine catch.
So, that explains the fuel issue.

The non ACDelco OPS never get enough amps to pass to the LP and hence the LP is not pumping.

There was an old thread that actually test that amp, you can search it but it is about 7-8 years. The poster actually called the mfg and ask why the amp difference between them. The mfg said, that is the spec that they got from GM. So that is the way they make it. Granted ACDelco is not much better but at least it is in spec.

Someone above suggested the addition of relay to the LP-OPS circuit, that can alleviate the issue even without the ACDelco OPS but you have to troubleshoot first.
 

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1995....

94 & 95 had a few issues. The LP got DIRECT power flowing through the OPS switch once running. It has been "debated" many times that the OPS switches, sometimes even AC Delco/GM can not handle the load (amps) required of the LP....

That is why, folks here have recommended that the 94/95 years get the relay mod. Basically, you splice a relay into the OPS/LP circuit. There are threads on it, but basically, the original OPS activates the relay which handles the load of the pump. It is identical to putting auxiliary lights- switches are usually rated for 10-15amps....but some lights draw 20-25 amps or more. The relay takes the load off the switch and the switch doesn't overheat and burn out... diddo with the relay mod for the OPS.

Now, someone marketed a plug and play harness to add a relay. I think it was Leroy Diesel, but I am not sure.

Check all the connections, positive and negative. It is possible something is loose or dirty or both. Check the starter, make sure it is tight to the block.

How old are your batteries? And what is their CCA (cold cranking amps)? The more the better. Most people suggest 850CCA at a min. You might have a dead cell that is random... a friend at work is having issues w/ a 2 year old battery in their Honda car...go figure. Jump starts fine, almost NO waiting....but twice in 3 days, there is an issue (and his alt is charging).
 

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Check Fuses in the underhood electrical center. IIRC the one that needs looked at is ENG-I

If it is blown, fuel heater is bad. unplug fuel heater, install new fuse, and Glow plugs and turbo boost will return. I dont think OPS/LP is on that circuit though.

I highly recommend Leroydiesel.com's lift pump relay harness, I run it on a few of mine and love it.
 
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