Factory 2000 Tahoe pump

 

Small Update:

Got my PCV/catch can issue figured out I believe. I ended up removing inline PCV I was running and rerouted my catch can lines properly. At least that is one potential issue ruled out now.

Started the truck last night and it fired off perfectly, zero hesitation (cold start, no prior starting attempts). Ran and idled great for about a minute. Then it choked and died, just like before. I checked my coolant sensor readings and confirmed the sensor is reading accurately - 15C cold reading and rose a couple degrees after running.

I've attached a couple pics of some data off my scan tool. Honestly not sure if any of it is useful, but grabbed the info just in case.

Next step is to check fuel pressure. I'm waiting on a gauge and some other parts to arrive and will be able to check then. Would a bad corvette fuel pressure/regulator be a potential cause of all of this? Perhaps it is not regulating pressure properly and giving the injectors more fuel than it is tuned for?

 

MAP sensor will make it dump fuel, verify that also.

 

Pull each of the plugs and take pictures so you can compare.


While you're waiting for the pressure gage, you can some more diagnostics:

• pull the fuel rail assembly away from the manifold (WITHOUT disconnecting the fuel lines)
• slide some catch pans underneath (a set of old large baking pans work)
• put shop towels under each injector tip
• key to on (DO NOT CRANK), to build fuel pressure
• look for leaks at the tips

this will confirm if one or more injectors is stuck open dumping fuel (since you have excessive fuel in the oil)

 

Update:

Got the fuel pressure gauge hooked up last night. Cycled the key a few times to hear the fuel pump kick on and build pressure. I can hear the pump run for about 3 seconds, then shut off as normal. Immediately after tuyrning the key (key on, engine off), pressure is right around 40 PSI, and drops almost immediately to 0 PSI. Just from the time it takes me to turn the key, then walk to the gauge at the fuel rail, pressure is already dropping. With a corvette regulator, shouldn't I be at 58 PSI and hold that pressure for at least a few minutes? Once I cranked the engine over, it ran for only about 10-15 seconds and the gauge looked like it was way higher than 58 PSI, but honestly I'm not sure that I read it right - I was a little distracted and didn't get a great read on it before the truck shut off.

So does this look like an injector issue? Not building enough fuel pressure to keep the engine running, and fuel ending up in the oil sounds like an injector has a serious leak, but some confirmation from you guys. Best method to check them is jsut by pulling the rail (with injectors attached) and cycling the key?

If I get no leaks from the injectors, where should I be looking next? Again, this is a truck style tank (2000 Tahoe) to a corvette filter/regulator, single line to the fuel rails.

 

Should be holding pressure for much longer. Likely either the regulator or injector(s). Corvette filter/regulators are known not to be reliable. But fuel smell does point to injector stuck open.

 

GameTech - he commented above - solved a very similar sounding problem with my Catalina engine. He thought that I had my O2 sensor connectors swapped to the wrong side so I switched 'em. And voila!! Problem solved.

Rick

 

Just out of curiosity, how would this indicate a bad corvette filter/fpr? Wouldn't a failed fpr show too high of fuel pressure, where the pump would be "pushing" through the regulator and not regulating it at 58 PSI, but rather exceeding it?

 

Not if it has an internal leak.

 

Yes, but that wouldn't explain fuel ending up in the oil right?

 

Is there any way to test this without cutting apart my harness? The connections for the o2's are not long enough to swap to the other side.

Also, I'm not sure this could be it, as it really doesn't explain the fuel pressure issue

 

No, the pressure bleed down would not. That would be attributed to be over-pressure, excessive richness, misfire, PCV related, or injector leakage.

The tip leakage could explain both. But, you could also have more than one issue too.

I'm leaning towards injector tip until we get more information.

 

Another update:

Pulled the fuel rails with all injectors in place - key on, engine off - absolutely zero leaks. My pressure will shoot up to about 40 PSI and drop immediately. It seems like with this sort of rapid drop in pressure, if it were an injector, it would be extremely obvious (ie, not a small drip, but shooting out).

Bolted the fuel rails back on, primed the pump a few times by cycling the key. Truck fired immediately, zero hesitation, fuel pressure was at ~65 PSI with zero fluctuation, even when I gave it some throttle. It ran for about 30-60 seconds before it died.

I ordered another corvette filter/fpr to throw on because at this point, I'm not sure what else to check. I know these are known to have issues sometimes. The one on it currently is a genuine AC Delco, the new one ordered is a WIX.

Any ideas? Appreciate all the help so far guys.

Also found this thread below. Not too much help, but simiar symptoms...
https://www.ls1.com/forums/showthread.php?t=180422

 

I had same thing with my car and it ended up up being crank sensor

 

can you explain what this means?

 

If it runs fine for a bit then acts up and starts overfueling consistently then it's either a pcm/tune or sensor issue... almost sounds like as the pcm enters closed loop it reacting to a sensor that's faulty or programed incorrectly.

To verify O2 sensors are on the right side unplug one and look at the data

Verify map sensor reads near baro with key on engine off.

I wouldn't worry about fuel system holding prime as long as pressure is correct running

 

PW at low spaeed?. Likely means using Pulse Width modulation of the fuel pump - but this is still my guess as to that question. Do you have a PWM style of PCM or operating system?

Rick

 

Honestly not sure, PCM I guess? It is a completely OEM 2000 Tahoe pump

 

When I unplug one O2 at a time, what info am I looking for? What would indicate to me that the O2's are acting up? I'm pretty sure my map sensor (key on, engine off) reads around 100kPA but will confirm later today.

As far as fuel pressure, I don't understand how this couldn't be of concern? Where is all the pressure going once it the key is turned and then bleeds off? Back into the tank? Something tells me this regulator has to be having issues...

 

Unplugging the O2 sensor on one bank and seeing if the same side in the data stops reading will tell you if they are wired up to the correct sides


The fuel pressure is leaking back into tank...not an issue...will make for extended crank condition when starting but if pressure is good while running then it is not causing your running issues