Truck stalled, wouldn't restart, then started fine hours later

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Kens1990K2500

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I've owned my 1990 K2500 with 5.0 TBI a little over a year now, and it always ran well, until yesterday. The engine stalled as I pulled into a parking spot at work yesterday morning. I tried to restart it. It cranked fine but would not start, or even attempt to start. I had a coworker listen for the fuel pump whine when I first turned the ignition on, and he said he couldn't hear the pump turn on. At the end of the workday, about seven hours later, I called AAA for a tow. As the wrecker pulled up, I decided to turn the key, and to my surprise, the truck started right up! I had him tow it home anyway, since someone had dropped off another vehicle to me, and I was afraid the truck might stall again on the road.

After the tow guy dropped the truck off at my house, again, it started right up. The truck has never had an issue with refusing to start, and intermittent problems can be a bear to diagnose, but I'm afraid to drive the thing now. My first suspect is the fuel pump. Truck has about 180,000 miles. I don't know if it's the original fuel pump. Can they work sometimes, and sometimes not work, as opposed to just stalling frequently? Years ago, I had a '97 4.3 Vortec truck that began stalling at drive-throughs, and it ended up being a bad fuel pump, but at least that truck gave me some warning, and it would restart.

For background, spark plugs were replaced a year ago, and distributor cap, rotor, plug wires and coil were replaced about four months ago, as general maintenance.

As stated, it's tough to diagnose something intermittent, so any suggestions appreciated (first thing I will check is fuel pressure, I am looking for 11 to 13 psi, right?). From reading posts with similar issues, I also see a lot of issues with the distributors, especially the ICM and magnetic pick ups. I'm wondering if it would be work getting a rebuilt distributor just for peace of mind, and the age of the vehicle.

Ken
 

Kens1990K2500

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Also worth mentioning, it seems like the truck idles very high when I first start it in colder weather, but it has always done that (not sure how high, since truck does not have a tach), I'm guessing it might be 1,500 to 2,000 rpm? Idle speed does drop down as truck warms up though.
 

Schurkey

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As you said, verify fuel pressure when turning the key from "Off" to "Run". Should have a 2-second "prime". The pump should also provide pressure when the engine is cranking or running.

Connect a scan tool, look for RPM signal during cranking. No RPM signal = no spark, no fuel injector spray. Even with no RPM, when the engine cranks long enough to build oil pressure, you should then have fuel pressure, but the injectors won't be triggered.
 

PlayingWithTBI

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Beat me to it, ha ha. For high idle when cold, check your CTS near the T-Stat housing. While you're there clean the grounds on it too.
 

Kens1990K2500

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As you said, verify fuel pressure when turning the key from "Off" to "Run". Should have a 2-second "prime". The pump should also provide pressure when the engine is cranking or running.

Connect a scan tool, look for RPM signal during cranking. No RPM signal = no spark, no fuel injector spray. Even with no RPM, when the engine cranks long enough to build oil pressure, you should then have fuel pressure, but the injectors won't be triggered.
Forgive my ignorance, but the scan tool I have is for OBDII vehicles. How exactly do I connect a scan tool to an OBDI truck? Or do I need a different type of scan tool?
 

evilunclegrimace

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I've owned my 1990 K2500 with 5.0 TBI a little over a year now, and it always ran well, until yesterday. The engine stalled as I pulled into a parking spot at work yesterday morning. I tried to restart it. It cranked fine but would not start, or even attempt to start. I had a coworker listen for the fuel pump whine when I first turned the ignition on, and he said he couldn't hear the pump turn on. At the end of the workday, about seven hours later, I called AAA for a tow. As the wrecker pulled up, I decided to turn the key, and to my surprise, the truck started right up! I had him tow it home anyway, since someone had dropped off another vehicle to me, and I was afraid the truck might stall again on the road.

After the tow guy dropped the truck off at my house, again, it started right up. The truck has never had an issue with refusing to start, and intermittent problems can be a bear to diagnose, but I'm afraid to drive the thing now. My first suspect is the fuel pump. Truck has about 180,000 miles. I don't know if it's the original fuel pump. Can they work sometimes, and sometimes not work, as opposed to just stalling frequently? Years ago, I had a '97 4.3 Vortec truck that began stalling at drive-throughs, and it ended up being a bad fuel pump, but at least that truck gave me some warning, and it would restart.

For background, spark plugs were replaced a year ago, and distributor cap, rotor, plug wires and coil were replaced about four months ago, as general maintenance.

As stated, it's tough to diagnose something intermittent, so any suggestions appreciated (first thing I will check is fuel pressure, I am looking for 11 to 13 psi, right?). From reading posts with similar issues, I also see a lot of issues with the distributors, especially the ICM and magnetic pick ups. I'm wondering if it would be work getting a rebuilt distributor just for peace of mind, and the age of the vehicle.

Ken
When is the last time that the fuel filter was replaced?
 

Kens1990K2500

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When is the last time that the fuel filter was replaced?
Fuel filter was replaced two months ago. Metal fuel lines had rotted a few inches forward of the filter, so as a temp fix, I found a metal fuel filter with barbed ends, so I could splice rubber fuel line to the filter's inlet and outlet, and splice the other ends of the hoses, to rubber hose on either end, using barbed couplings. God only knows how long the previous filter had been in there, but apparently a very long time, as the fuel line nuts were seized into it.

It may also be worth mentioning that I've always had to crank the truck quite a few seconds before it starts (I feel like it should catch sooner than it does, being fuel injected). It has never started with a blip of the key. Warm or cold weather makes no difference on the extended cranking time, although in cold weather, it helps to hold the accelerator pedal down about a 1/4 of the way.
 

Schurkey

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I've always had to crank the truck quite a few seconds before it starts (I feel like it should catch sooner than it does, being fuel injected).
Verify 2-second fuel pump "prime" when key is turned from "Off" to "Run".

No prime = failure somewhere in the fuel pump relay circuit. Engine has to crank long enough to build oil pressure; oil pressure switch bypasses fuel pump relay.
 

Kens1990K2500

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Can a faulty ignitiion control module allow the truck to run sometimes, and not run sometimes (like when the engine gets fully warm)? Or do they usually just die and the truck won't start ever again?
 
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