Got the truck back this morning from the garage. I was assured the problem was the loose alternator belt. They also eliminated some leaky radiator lines that were running an auxilary heater or something and replaced the master cylinder and a brake line. $670.00 (including $150 for the tow)!!!

Truck fired right up. Drove it back 15 miles and parked it. A few hours later, I came back and started the truck, getting ready to head out and it started fine but only ran for about one minute before suddenly stalling. This is the first time the vehicle stalled while not in motion.

After the stall, it turned over fine again, just no start. I decided to hook up some jumper cables for the heck of it and after several tries, I got it to start for about 3-5 seconds. This time, as it stalled, I heard a slight descending whine or hiss. Does this indicate anything?

I've shared some of your comments with the shop and they seem disinterested in hearing it.

---AutoMerged DoublePost---

Oh yeah, these guys assure me this vehicle is equipped with an electronic fuel pump, rather than a mechanical.

 

So? They assured you they knew exactly what the problem was with the stalling! I wouldn't be surprised if they were taking you for a ride. You already shelled out 700 bones to them and they didn't fix the problem you brought it in for, why wouldn't they just continue to milk you?

The way you describe how it suddenly stalls, every single time, very, very strongly suggests that it is the fuel injection pump fuel cutoff solenoid. The solenoid could be bad, but the most likely case is that one of the wires leading to the solenoid is bad and the voltage is being interrupted by this bad wire when it heats up and/or is jolted. This is absolutely the first thing I would check.

Reproducing bad wire problems can be a nightmare, but here's some suggestions. Next time it dies, pop the hood and put a volt meter right on the fuel cutoff solenoid wire, it should be 12+. Take the wire off, put it on again, you should hear a "click" inside the injection pump as the solenoid opens and closes. No voltage means a bad wire (likely) voltage but no click means a bad solenoid (less likely).

No voltage means there is a break in the circuit somewhere between the solenoid and the battery. Start at the batteries and make sure those wires are good and solid, jiggle them with your hands and listen for the solenoid to click (or set up a lamp/buzzer/voltmeter). Something to try in your driveway: block the wheels and set the parking brake, start the engine, warm it up and then get under the truck and gently jiggle the wires bundle leading up from the starter (watch out for the exhaust!). If it dies, bad wire. Try the wire bundle running down the passenger side of the engine as well and the wires that route behind the engine. Just grab them and give them the kind of jiggle you would expect a pot hole to produce.

Also check that key like turbine doc suggests! Reach under the dash and jiggle the wire bundle leading up to the key. Troubleshooting electrical problems can be a pain but there is a method to it and once you find the problem it's easy to fix. I would try at least what you consider to be $700 worth of your time diagnosing the problem yourself before taking it back to a mechanic. Also, make sure your mechanic really knows diesels and isn't just a gas guy taking you for a ride.

I have never seen a 6.2 with an electric fuel pump but I have never seen a van, so maybe it does have one. Look on the passenger side of the engine block toward the front of the engine, below the exhaust manifold. You can also follow the fuel supply line back from the fuel filter to the pump. There will either be a fuel pump there with one fuel line coming from the tank and the other going to the filter, or a plate covering the hole where the mechanical fuel pump would have mounted. If there is a pump there you know your mechanic is lying.

---AutoMerged DoublePost---

Oh yeah, one other suggestion. Next time it dies, do the test for the solenoid "click" by removing the control wire. If it does not click, run a wire directly from the battery to the solenoid. You can even have this wire pre connected to the battery and neatly tucked away ready to be attached to the solenoid. If it clicks then the truck should starts right up, you got a bad wire somewhere. Drive it home and start hunting. To turn the engine off just disconnect the wire you made.

 

BULLETIN NO: 93-6C-110

SECTION: 6C Engine Fuel

NUMBER: 5

CORPORATE REFERENCE NO: 276301R

DATE: August, 1993

SUBJECT:
STALLING/HESITATION/LOW POWER/WHITE SMOKE (CHECK LIFT
PUMP/CONDITION; NEW OIL PRESSURE SENDER/SWITCH AVAILABLE)

MODELS:
1992-93 C/K TRUCKS WITH 6.5L TURBO DIESEL (RPO L65) OR 6.2L DIESEL (RPOs LH6 and LL4)

THIS BULLETIN CANCELS AND REPLACES GMC TRUCK BULLETIN 92-6C-142 (CORP. # 276301) DATED OCTOBER 1992, AND IS BEING REVISED TO ADD 1993 MODEL YEAR, ANNOUNCE A NEW OIL PRESSURE SWITCH PART NUMBER, AND ADD FURTHER INFORMATION TO THE CORRECTION SECTION. ALL COPIES THE OF 92-6C-142 SHOULD BE DISCARDED.

CONDITION:

Any one or combination of the following:

- Low power (continuous or intermittent)
- Occasional stalling or hesitation on cold start
- White smoke at high engine speed


Above conditions may occur on some 6.5L turbo-charged (VIN F) and 6.2L naturally aspirated (VINs C and J) diesel-powered vehicles.

CAUSE:

Improper electric lift pump operation, due to an inoperative lift pump electrical circuit OR a faulty pump. THE MOST PROBABLE CAUSE IS A FAULT IN THE OIL PRESSURE SENDER/SWITCH CIRCUIT which operates the lift pump during engine operation. The oil pressure sender/switch is located on the left bank, rear of the intake manifold.

A new oil pressure sender/switch, P/N 10243574, will be available from GMSPO August 30, 1993. This new part provides increased switch contact durability, and was introduced into vehicle production late in the 1993 model year.

CORRECTION:

Check the operation of the lift pump first. It is located under the vehicle on the driver's side frame rail.

Lift pump operation can be checked by feeling its pumping action while the engine is idling. You should feel the rapid end-to-end oscillation of the hollow plunger within the pump. Care should be taken not to confuse this oscillating with normal vehicle vibrations. If the pump is not operating, be sure to check the pump's electrical supply circuits along with the actual condition of the pump.







The two circuits powering the lift pump are shown in Figure 1; both circuits need to be checked. Intermittent supply circuit problems may require monitoring the voltage at the lift pump during vehicle operation. This can be accomplished on vehicles equipped with Data Link Connectors (DLC) by probing for voltage at terminal G while the engine is running (charging system functioning properly and batteries fully charged). A difference of more than 1.5 volts between terminal G and battery voltage indicates a problem in the oil pressure switch circuit.

Once diagnosed, the problem is resolved by either replacing the faulty oil pressure sender/switch, the faulty lift pump, or repairing the wiring.

---AutoMerged DoublePost---

SYMPTOM DESCRIPTION:

Engine won't start, requires excessive cranking time, or starts then dies immediately.



POSSIBLE CAUSE ACTION

Empty fuel tank or


Fill tank.
fuel tank vent blocked


Bleed fuel system.
Check tank vent.
Improper fuel


Drain fuel tank, flush system, and fill with proper fuel. Change
fuel filter.



Air in fuel system


Bleed fuel system.
Lack of voltage supplied


Check fuel solenoid circuit.
to the fuel solenoid



Fuel solenoid inoperative


Replace fuel solenoid.
Clogged fuel filter


Replace fuel filter.
Leaking, restricted, or damaged


Replace leaking or damaged
supply lines, or loose fuel lines or tighten connections as
connections needed. Bleed fuel system.

Wax buildup in fuel filter


Replace fuel filter, and
(cold weather only) verify that the proper fuel is
being used.

Incorrect injection pump to


Adjust injection pump timing.
engine timing



Air intake heating system


Check air intake heater relays.
malfunctioning



Check air intake system electrical circuit.
Fuel injection sequence


Check fuel injection lines
does not correspond with
firing order for proper routing.

Low or uneven engine


Repair as necessary.
compression



Restricted, blocked, or


Remove restriction or
leaking fuel injector lines replace lines as necessary.
Bleed fuel system.

Malfunctioning
injection pump



If injection pump is malfunctioning or will not adjust properly, replace as
a unit.

---AutoMerged DoublePost---

Fuel Pump Pressure 40 - 60 kPa (5.8 - 8.7 psi)

Fuel Pump Flow [1] 237 ml (1/2 pt) in 15 seconds

 

Ok! I will pick the truck up from the third and hopefully last mechanic tomorrow. I like this guy the most. He is a mechanic by trade but works on diesels on the side in a shop behind his house. After explaining my problems, he immediately started thinking about wiring issues, as many of you have suggested.

Here's what he determined. Appearently there was some sort of controller installed that relayed power to the injection pump shut-off solenoid. The device was designed to monitor coolant level, coolant temperature, low oil pressure and oil level. Basically an engine protection system, designed to shut the engine down during situations which may cause serious damage. Keep in mind that I did not start having stalling problems until after the vehicle got hot and was found to be significantly low on coolant as a result of an undetected leak. According to the mechanic, it is not uncommon for municipal/government-owned vehicles to be retrofitted with such systems (this vehicle was originally owned by the harbor patrol).

The mechanic found the original wiring harness still in tact with taped ends. He rewired it to its original configuration, bypassing the protection device. He claims to have had it running for hours with no problems at all. I'm glad but I've heard that story before and it's hard to get excited.

Does this latest theory make sense to anyone?

 

yeah a crappy wiring job by a government employee sounds about right

 

Awesome nick! An aftermarket device specifically designed to shut off your engine sounds like the perfect culprit. Not sure such a system is worth it vs just keeping an eye on your fluid levels. Glad you found the problem, at least they left the old harness in place instead of hacking and slashing it!

Sounds like the govt employee installed it right, it's purpose is to cut out the engine when it detects low coolant.

nick, where's the leak? How low did the coolant get? hopefully you didn't cook your water pump bearings which I believe require adequate coolant at all times or will fail prematurely.

 

Thanks. The leak was in some lines that ran out to an auxilary heater to the rear of the truck. The "truck" is really a utility box van. The radiator is filled via a resivoir. The resivoir was bone dry and thaough I can't say for sure, it's possible the radiator was as low as half full.

What is the outcome of failed water pump bearings? Just pump replacement, or can something worse occur?