1994 Yukon 6.5 literturbo diesel

[beerqueen]

Problem: Explain your problem in concise language (ie: Cranks but won’t fire). ____________While driving the truck hesitates and stalls.________________

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

- Year: 1994______
- Truck model and class (ie: c2500) _Yukon 1500________
- Automatic or Standard ___Auto_______
- Mileage: (indicate miles or km) 131,000_________
- Replaced parts and mods (IP, PMD, chip/PCM, TM, injectors etc) __PMD and fuel pump_________
- Model: ‘S’ or ‘F’ engine, NA or Turbo, EGR? __Turbo____________
- Ambient outside temp: (indicate *C or *F) 50F__________
- What fuel are you using? (#1 Diesel, #2 Diesel, Bio, VO, WVO, etc) __2 Diesel_______
- What fuel additives are you using? ________None___
- Where are you located? Wisconsin_____________

General maintenance: inspect and evaluate the condition of each. When were they last changed?
- Air filter __Good_______
- Fuel filter __3000 miles ago_______
- CDR Valve? ___Don't know______
- Coolant – last flushed/replaced at ___Don't know__________
- Oil – synthetic/regular, changed at Regular changed every 4000___________
- Batteries – state of charge, (matched set) replaced at Good_____________
- Battery cables and grounds (removed, cleaned and tightened):Good ______________
- Glow Plugs - how many miles on them? _Not sure________ What type? _____________
- Injectors - last changed at ______Not sure_________


History: (Describe how the problem first appeared.)
- What were you doing when it happened? __Driving around 45mph____________
- How was the truck running fine before this problem appeared? Good_____________
- Has this problem ever happened before? _____yes__________________
- 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, normal time_________
1f] Does your glow plug light come on? ____Yes_____ For how long? Normal time _________
1g] Do you see smoke from the exhaust while cranking? What color? __No______
1h] Does the Service Engine Light Glow during Start/bulb check? Yes________

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

3] PMD / IP Issues
3a] Location of PMD (on pump, on intake, remote mounted) ___Remote________
3b] Condition of Extension harness (if used) Vendor or Homemade? _Good________
3c] Condition of grounds / ground wires to IP / PMD. Check Harness. __Good_______
3d] PMD Make: _______Stanadyne____
3e] PMD Age: ___Brand new__________

4] Stalling Issues
4a] Do you experience stalling only when hot? _No, it starts hesitating after 1 mile_______
4b] Does it stall under particular circumstances? (ie hit bump, or on accel) ___No___
4c] Does pouring cool water over the IP seem to help with restarting? _Havent tried it________
4d] Is stalling momentary (engine recovers)? _____Yes, most of the time. ____
4e] Does SES light come on when engine hiccups? ____Not sure_____
4f] Does cruise control quit working when engine hiccups? _Don't use__________
4g] Does re-starting seem to reset engine, restoring cruise and power? ___Yes______
4h] Changes to dash lights or instruments during stalling events? _____Not sure______

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

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

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

List and describe any other factors which are not addressed in this checklist. We can’t see, hear, smell, or touch your truck, so the more descriptive information you can give, the more likely it is that somebody can assist you.

 

[JiFaire]

Welcome to The Truck Stop ... good first post!

The first thing you need to do is see if there are any stored codes... your truck's computer will take note of events like stalling and store a DTC (Diagnostic Trouble Code) to help you diagnose the problem.

Fortunately, with a 1994, you can check these codes with a paper clip instead of an expensive code-reader, as long as your SES (Service Engine Soon) light is functioning.

Here's how to check the codes:

http://www.thetruckstop.us/forum/showthread.php?589-6.5-Diesel-Technical-Library&p=111592#post111592

Note that we have an extensive 6.5 section here at The Truck Stop, including a fairly well-stocked Technical Reference Library, and some extremely-experienced and knowledgeable members that love to help you out and welcome you to our community... this here is the best place on the web, and we hope you stick around to be part of it!

Once you have your codes read, get back to us in this same thread, and we'll help you figure out what they might mean... or you can look at this list:

http://www.thetruckstop.us/forum/showthread.php?2657-A-little-help-here...&p=50700#post50700

Jim

 

[ak diesel driver]

my internet guess is the oil pressure sending unit which controls the lift pump after the engine starts. also put a piece of clear tubing on the return line coming out of the Injection Pump and look for air

 

[bk95td]

:welcome2:
A couple free things to try first before we help you spend your money . Try driving with the fuel cap loose. Also check to be shure it is a "diesel fuel only" cap [gassers are very different] The wrong or a cap with a clogged vent will build vacume in the tank making it very difficult for the fuel lift pump to pump fuel.
Remove and clean every ground in the engine compartment. These trucks depend heavily on good grounds. The black and black-tan grounds on the rear of the intake manifold are the most critical. Just looking at the grounds doesn't mean they are clean in the contact area. They need to be taken apart and cleaned up with a wire brush. After reattaching the grounds a coating of dielectric grease will help slow down corrosion.

 

[beerqueen]

Thanks everyone for getting back to me so soon. I was out of town and just checked the codes. The truck does not start at all now. The SES light comes on, the glow plug light comes on for the normal amount of time, the engine cranks and wants to start, but seems like it's not getting any fuel. The codes are:

13, 19, 32, 33 and 98.

 

[JiFaire]

Thanks everyone for getting back to me so soon. I was out of town and just checked the codes. The truck does not start at all now. The SES light comes on, the glow plug light comes on for the normal amount of time, the engine cranks and wants to start, but seems like it's not getting any fuel. The codes are:

13, 19, 32, 33 and 98.

Courtesy of the DTC Code list in the 6.5 Technical Library,

13 - Engine Shutoff Solenoid Circuit Fault

19 - Crankshaft Position Reference Error

32 - EGR Circuit Error

33 - EGR Control Pressure/Baro Sensor Circuit High

98 - Cylinder Balance, Cylinder 8

I don't believe all those codes came up at once. Clear all of your codes by following this procedure:

http://www.thetruckstop.us/forum/showthread.php?589-6.5-Diesel-Technical-Library&p=111592#post111592

Then remove the jumper wire (or metal paper clip) and try starting it again, so see which ones come back.

I'm thinking you have a short in a wiring harness, or your PMD or PMD harness is being funny. Clean all of your grounds as per this thread:

http://www.thetruckstop.us/forum/showthread.php?3069-Melange-of-DTC-codes!

and check all of your connections to make sure they are all tight. These trucks run on computers, and computers run on a steady diet of clean electricity. One or two bad ground connections will introduce gremlins into your system.

 

[beerqueen]

We did a reset and now we only get code 13. Any ideas??

 

[1995yukon65]

The code 13 according to an above post is the fuel cutoff solenoid. It is located at the front of the IP. Have someone turn the key while you are listening to the solenoid to see if you can hear it click. If it doesn't then unscrew it from the IP and pull the plunges out of it. There is a snapring that holds the plunger to the body. If still no start then trace the wires for the shutoff solenoid and see if they are broken or cramped anywhere.

 

[JiFaire]

Yeah, the FSOL is the tall silver cylinder standing straight up at the front of your IP...

Go to this thread:

http://www.thetruckstop.us/forum/showthread.php?9494-Part-Locations

... and scroll down until you get to Fuel Shut-off solenoid or something that sounds like it. It will have 2 wires coming off the top in a loom.

If the FSOL is active (clicking when key is turned), you might want to pull the plunger out of it as described above, but if you are indeed getting fuel to your injectors as you described in the checklist, it is unlikely to be the problem...

Have you tested the Lift Pump with the engine idling? (open the brass T-valve with the engine running, to make sure the lift pump is delivering more fuel than the IP needs... if it is, you'll have fuel come running out of the hose and the engine will keep idling away. If it isn't keeping up with demand, the engine will likely stall.)

 

[buddy]

I have had two intermittent Fuel/Engine Shutoff Solenoids, that caused stalling. Its like my truck eats them somehow, maybe it was voltage related or something.

 

[beerqueen]

Thanks everyone. We checked/cleaned the grounds, the fuel cap is a diesel cap. We checked the fuel solenoid - it clicks. We started the engine and opened the brass T - valve while it was running. No fuel came out and the engine died after a while. - Less than 1 minute. The lift pump makes noise and was just replaced. We replaced the fuel filter around 3000 miles ago. The truck seems to run okay around 45-50 mph, but when I go up a hill, it starts to stutter. Could it be a dirty fuel filter or the filter in the tank? It's not my truck and I'm trying to help my Dad, so I'm not as famailar as I would be with my own truck.

 

[NVW]

LP can make noise but not work. I see you said it was new so I would put a fuel line on the LP inlet into a container of clean fuel and see if it pumps. If it does the sock in the tank is plugged or the fuel line into the tank is drawing air. If it runs but doesn't pump the new LP is NFG.

 

[buddy]

Or the OPS is not sending it enough voltage to pump fuel. On a 94 you really need the OPS relay mod, because the OPS will fail every year on most trucks.

But it will drop to like 7V because it cannot pass enough current through burnt contacts or whatever, and it might make noise but no pumping. You can check the voltage out of the OPS while the truck is running, just connect a meter to contact G of the DLC (OBD) port and see what the voltage is between it and ground. If it is not at least 13V then the OPS is bad. And it can be intermittent, go from 13V to 7V, ect...

 

[beerqueen]

When the engine is not running and I open the T-valve with the key on, I get fuel coming out.

 

[ak diesel driver]

See post #3

 

[buddy]

When the engine is not running and I open the T-valve with the key on, I get fuel coming out.

If that is the case then someone has previously modified the system, because in stock configuration the LP does not run with the key on, only when cranking, via the LP relay on the firewall, and while there is oil pressure, via the OPS. If someone tied the power to the ignition it may run all the time with the key. It would be good to verifiy the voltage at the DLC while it is running and misbehaving. Then you can chase a bad LP or clogged tank sock.

 

[JiFaire]

If that is the case then someone has previously modified the system, because in stock configuration the LP does not run with the key on, only when cranking, via the LP relay on the firewall, and while there is oil pressure, via the OPS. If someone tied the power to the ignition it may run all the time with the key. It would be good to verifiy the voltage at the DLC while it is running and misbehaving. Then you can chase a bad LP or clogged tank sock.

Dunno, buddy ... mine did this, too, even before I did the relay mod.

I agree with you that the contacts in the OPS are likely an issue... if he gets no fuel from the T-handle when the engine is running, then OPS or LP are prime suspects. Certainly, I wouldn't worry about the FSOL until I cleared those up.

Hey Beerqueen... your next step is to run a power line directly from a key-on power source to the LP ont he frame under the driver's arse... if you supply direct power to the LP, and this issue goes away, you done found your culprit - you will need to do the relay mod to the OPS, and you should be back in business.

***This is for diagnostics only... don't leave the LP directly wired like this. In an accident, power will keep flowing to the LP, it will keep on feeding the fire, and you'll be hooped. The OPS set-up is a safety feature, one that in your case, may need some attention.

 

[buddy]

The traditional relay mod doesnt add a key on LP powering, so if the LP came on with key before the mod or after then the LP power circuit had been modified and is not using the OPS as a safety feature. Now, I fully recommend modifying the system such that it primes during the glow time, like the OBD2 trucks do.

 

[beerqueen]

My Dad did modify the truck when he put the new lift pump in. I have to flip a switch to turn the pump on. (He's 81, hates computers and believes this is the cause of all his problems. He wants to put the truck on the curb. That's why the truck is at our house and we're trying to help out.) We checked the OPS when the truck is running and we get a steady 13+ volts. Check tank sock?

 

[oilslick]

change the fuel filter again, its cheap and the only way to know for sure it is not slowing down flow, had a buddy call me with similar problem after he replaced the pmd and fuel pump I suggested replacing filter even though it only had 2500 miles on it he said it is fixed now!