6.5 stalls on accel

[rblaine1004]

Good morning to all. I have a 1994 Chevy K2500 Suburban with a 6.5 TD. Here are the particulars on my truck:

Problem: Explain your problem in concise language (ie: Cranks but won’t fire). __Stalls under accel.__________________________

Demographics: tell us about your truck and your ambient conditions:

- Year: __1994____
- Truck model and class (ie: c2500) _1994 Chevy K2500 Suburban________
- Automatic or Standard _Automatic_________
- Mileage: (indicate miles or km) _256,465________
- Replaced parts and mods (IP, PMD, chip/PCM, TM, injectors etc) _IP, PMD and Feed Pump__________
- Model: ‘S’ or ‘F’ engine, NA or Turbo, EGR? _F, non EGR_____________
- Ambient outside temp: (indicate *C or *F) ___40 F_______
- What fuel are you using? (#1 Diesel, #2 Diesel, Bio, VO, WVO, etc) _What is at the gas station________
- What fuel additives are you using? ___________
- Where are you located? __Falls Church, VA___________

General maintenance: inspect and evaluate the condition of each. When were they last changed?
- Air filter _Replaced ________
- Fuel filter _Replaced________
- CDR Valve? _________
- Coolant – last flushed/replaced at _Don’t know, looks new____________
- Oil – synthetic/regular, changed at __Molbil Delvac Super 1300 15/40. 256,465_________
- Batteries – state of charge, (matched set) replaced at _New____________
- Battery cables and grounds (removed, cleaned and tightened): _All_____________
- Glow Plugs - how many miles on them? _Don’t now________ What type? _____________
- Injectors - last changed at __Don’t know_____________


History: (Describe how the problem first appeared.)
- What were you doing when it happened? _Driving_____________
- How was the truck running fine before this problem appeared? _Fine____________
- Has this problem ever happened before? _Don’t know______________________
- Describe any related factors that might be part of the problem. _?_____________
- Have you checked for DTC (Diagnostic Trouble Codes)? (Y.N) _No___ And? ________


Diagnostics:

1] Starting:
1a] Does the engine start? _Yes________
1b] Does the engine crank over? _Yes_______
1c] Are your batteries fully charged? _Yes________
1d] Have you removed, cleaned, and tightened all battery connections? _Yes_______
1e] Does your Wait to Start light come on for a time? How long? _Yes. 2 to 5 sec.________
1f] Does your glow plug light come on? _________ For how long? _________
1g] Do you see smoke from the exhaust while cranking? What color? _Yes. White_______
1h] Does the Service Engine Light Glow during Start/bulb check? __No______

2] Fuel Issues (if not running):
2a] Can you hear your lift pump working? _ ___________
2b] Do you get a steady flow of fuel from the water drain (T-handle) ? _ ________
2c] Loosen the inlet line from the IP – is fuel coming out (Lift Pump on)? _ __________
2d] Loosen an injector line and crank the engine - does fuel come out? _________
2e] Do you hear a vacuum (hiss) when you remove the fuel cap? ___________

3] PMD / IP Issues
3a] Location of PMD (on pump, on intake, remote mounted) _Remote mount__________
3b] Condition of Extension harness (if used) Vendor or Homemade? _Vendor________
3c] Condition of grounds / ground wires to IP / PMD. Check Harness. _Good. Yes________
3d] PMD Make: _Stanadyne__________
3e] PMD Age: _New____________

4] Stalling Issues
4a] Do you experience stalling only when hot? _Yes___________
4b] Does it stall under particular circumstances? (ie hit bump, or on accel) _On Accel_____
4c] Does pouring cool water over the IP seem to help with restarting? _N/A________
4d] Is stalling momentary (engine recovers)? _If I only take my foot off the pedal________
4e] Does SES light come on when engine hiccups? __No_______
4f] Does cruise control quit working when engine hiccups? Haven’t got to that point __________
4g] Does re-starting seem to reset engine, restoring cruise and power? _No________
4h] Changes to dash lights or instruments during stalling events? _No__________

5] Running Issues
5a] On cold start, does upper rad hose get hard before engine warms up? _______
5b] Any bubbles or oil film in coolant overflow tank? _______
5c] Any white slime on oil surfaces (dipstick, CDR, oil Fill cap)? __________
5d] Excessive white smoke from exhaust on cold start? _________
5e] Excessive black smoke from exhaust under hard acceleration? __________

6] Performance Issues
6a] Do you have gauges (boost, EGT) ? ___________
6b] Maximum boost under load? ____________
6c] Have you added a performance PCM (reflash) or Chip? ______________
6d] Have you changed exhaust / downpipe / crossover? ________________
6e] Wastegate – mechanical or vacuum (OEM)? ______________

7] Temperature-related Issues:
7a] Single or dual thermostats? ____________
7b] Have you replaced them lately? Manufacturer of replacements? _________
7c] Have you pulled and cleaned Radiator and coolers lately? ____________
7d] Have you replaced the fan clutch? Manufacturer of replacement? ________
7e] (winter) Have you tested your antifreeze? Good to what temp? __________
7f] (winter) Are you using a winter grille cover? ___________

Does anyone know of a good diesel machanic in the Fairfax County, VA area. I need some help. rblaine1004.

 

[ak diesel driver]

could be several things. 1 possible PMD (not likely IMO) 2. failed OPS 3. dirty filter or tank sock 4. bad lift pump

 

[rblaine1004]

What is the OPS and where is it located? I've replaced the feed pump Delphi(OME). The PMD is new and has been relocated with a heat sink to the outside of the truck underneath t bumper.

 

[THEFERMANATOR]

OPS= oil pressure switch. On OBD1(94-95) 6.5's it powered the fuel pump while the engine is running. When it goes the lift pump stops pumping and starves the engine of fuel. With the engine running, go out and open the little t handled valve on teh front of the engine and see if you get fuel or if it stalls out. This will give you an indication as to wether or not your lift pump is working while running.

 

[JMJNet]

OPS= oil pressure switch. On OBD1(94-95) 6.5's it powered the fuel pump while the engine is running. When it goes the lift pump stops pumping and starves the engine of fuel. With the engine running, go out and open the little t handled valve on teh front of the engine and see if you get fuel or if it stalls out. This will give you an indication as to wether or not your lift pump is working while running.

x2, do this test to determine if OPS is failing to run LP/Feed Pump.
This is one of the weaknesses.

If OPS is bad, replace with ACDelco OPS only, not aftermarket part store brand.

 

[rblaine1004]

The truck will run fine in the drive way idling all day long, I've got 45 pounds of oil pressure on oil gauge.

 

[ak diesel driver]

OPS has a seperate set of contacts in it to run the lift pump, it won't affect how the guage reads. IP normally has enough suction to draw fuel past a dead LP/OPS.

 

[THEFERMANATOR]

The truck will run fine in the drive way idling all day long, I've got 45 pounds of oil pressure on oil gauge.

The injection pump can create some suction and still run, but to much and it will shut off or cut out. And the oil pressure guage and fuel pump portion are seperate inside the OPS. So even if teh guage is working, it does not mean the switch for the pump is working. Find teh t handle valve and open it while it is running to check for fuel first, and go from there. Your problem sure sounds like a classic failed OPS to me.

 

[JMJNet]

The truck will run fine in the drive way idling all day long, I've got 45 pounds of oil pressure on oil gauge.

It can show 100psi of OIL pressure but NOT FUEL PRESSURE.
Remember, OPS measure the OIL Pressure NOT fuel pressure.

As ak said, the OPS controller is on a different circuit.

You can also put an Fuel Pressure Gauge after filter to measure the fuel pressure.

Yes, it can run but it will choke plus you will ruin the most expensive part which is the IP.

My suggestion is to read some reference material in the Technical Library.

As there may be other things that may not be right that cause your issue.

 

[Burning oil]

All good advise^^^

My bet is a dirty sock as they will stall an engine where as no LP will just run slugish. IME anyway.

Any updates.

 

[rblaine1004]

Thank you Sir. You were spot on with the OPS. Thanks again.

 

[handcannon]

Now that apparently you have it running again you need to do the OPS mod.

Auxiliary 12V power is fed to a relay, which then can feed the LP. The LP circuit in the OPS is used to trigger the relay. The OPS can only handle just a limited amount of draw through it before the contacts inside it for the LP start to fry. This relay mod keeps the LP from drawing too much power through the OPS, keeping the OPS alive much longer.

Before I knew about needing to use an AC Delco OPS only I used another brand which only lasted six weeks, and this was with the relay mod having been already completed. I have now gone two years with no problems since I went to the AC Delco OPS and the relay mod.

Don