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Discussion Starter · #1 ·
92 gmc 350 4x4. Truck cranks and you can take it down the road. After a minute or so, it starts boggin down or flooding out when u go up an incline or just simply give it a lil gas. Once it starts acting up, u can still be rolling down the rd, shift truck in neutral, turn it off, crank it back up and put it in drive and it runs on all 8 like a champ for a few minute before it starts acting up again. I have changed fuel pump, filter, radiator because pit cock blew
out, distributor cap, rotar button, coil pack, map sensor and cooling sensor. Still same thing happens.............. need help
 

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2000 Silverado Z71 4x4 5.3L 460k+ miles w/ GM rebuilt motor and trans
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Check your TCC solenoid. Your torque converter may be locking up and staying locked.

Caveat: I base this on your symptoms and my Google search for a TCC solenoid on your model year.
 

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I'm leaning towards your EGR. If its diaphragm is bad, when the PCM turns on the EGR, you get a bad vacuum leak. You can test it with a vacuum hand pump to see if the diaphragm moves and then holds suction.
 

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How do you know it was flooding out? Can you smell unburned gas at the exhaust?

Bogging down can be over fueling, under fueling, low compression or inconsistent spark.
 

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I'm going to blame a plugged exhaust, probably a bad cat.
 

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‘01 Silverado 2500HD 8.1/Allison 5sp xcab long bed
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I know the fuel pump is new, but it wouldn’t hurt to verify fuel pressure as well.
 

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Greg, what is the fuel pressure range for a 1992 350? (TBI?)
 

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‘01 Silverado 2500HD 8.1/Allison 5sp xcab long bed
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Factory spec is 9-13psi, but most of us have found that even 10 can be problematic.
 

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So shoot for 13psi?

I got a friend with a 1991 C1500 with a 350 that's also bogging down and asking for ideas. Not familiar with T/B injection.
Does it have to be 13 psi when priming the fuel line with ignition key ON or while engine running?
 

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‘01 Silverado 2500HD 8.1/Allison 5sp xcab long bed
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Ideally, yes, but many times you won’t be able to get that high without a new pressure regulator spring, or like Pete @PlaywithTBI has, an adjustable regulator.

I put a 14psi spring in mine.
 

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but many times you won’t be able to get that high without a new pressure regulator spring, or like Pete @PlaywithTBI has, an adjustable regulator.
Yep, here's some pics. It's pretty easy with stuff from RV Morse and only a little over $100. Note: I just looked at his website, unfortunately he passed away 08/07/21 - RIP. There are other folks that do this too, you'll just have to Google AFPR for GM TBI or something like that.
Here's an 18LB spring I bought a while back - it's somewhat of a challenge to get it installed fighting against the spring.
Hat Table Automotive tire Wood Drinkware


Installed in place.
Automotive tire Motor vehicle Bicycle part Rim Automotive wheel system


You need to drill a hole on the bottom plate below the regulator for the adjusting screw.
Audio equipment Gas Electronic device Recreation Auto part


And bend the MAP vacuum tube down a bit to fit
Automotive tire Motor vehicle Rim Automotive design Machine tool


And here it is on the engine with a 28LB spring. See? Easy peasy, HTH.
Motor vehicle Automotive tire Hood Automotive design Bumper
 

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Discussion Starter · #13 ·
Yep, here's some pics. It's pretty easy with stuff from RV Morse and only a little over $100. Note: I just looked at his website, unfortunately he passed away 08/07/21 - RIP. There are other folks that do this too, you'll just have to Google AFPR for GM TBI or something like that.
Here's an 18LB spring I bought a while back - it's somewhat of a challenge to get it installed fighting against the spring.
View attachment 170296

Installed in place.
View attachment 170297

You need to drill a hole on the bottom plate below the regulator for the adjusting screw.
View attachment 170298

And bend the MAP vacuum tube down a bit to fit
View attachment 170299

And here it is on the engine with a 28LB spring. See? Easy peasy, HTH.
View attachment 170300
So do I need to check my regulator spring for starters? Possibly wore out?
Yep, here's some pics. It's pretty easy with stuff from RV Morse and only a little over $100. Note: I just looked at his website, unfortunately he passed away 08/07/21 - RIP. There are other folks that do this too, you'll just have to Google AFPR for GM TBI or something like that.
Here's an 18LB spring I bought a while back - it's somewhat of a challenge to get it installed fighting against the spring.
View attachment 170296

Installed in place.
View attachment 170297

You need to drill a hole on the bottom plate below the regulator for the adjusting screw.
View attachment 170298

And bend the MAP vacuum tube down a bit to fit
View attachment 170299

And here it is on the engine with a 28LB spring. See? Easy peasy, HTH.
View attachment 170300
So do I need to check the spring on mine? Could it be wore out?
 

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‘01 Silverado 2500HD 8.1/Allison 5sp xcab long bed
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Negative. Check your fuel pressure. You will need a TBI pressure testing kit. The chain parts stores should have them available through their loaner tool program.
 
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Yep, here's some pics. It's pretty easy with stuff from RV Morse and only a little over $100. Note: I just looked at his website, unfortunately he passed away 08/07/21 - RIP. There are other folks that do this too, you'll just have to Google AFPR for GM TBI or something like that.
Here's an 18LB spring I bought a while back - it's somewhat of a challenge to get it installed fighting against the spring.
View attachment 170296

Installed in place.
View attachment 170297

You need to drill a hole on the bottom plate below the regulator for the adjusting screw.
View attachment 170298

And bend the MAP vacuum tube down a bit to fit
View attachment 170299

And here it is on the engine with a 28LB spring. See? Easy peasy, HTH.
View attachment 170300
Peter, the max on the acceptable fuel pressure range of 9-13 psi is only 13psi. Why install an 18 lb spring? Is 18 lb the max on the spring and 13lb is the mid range of adjustment?
 

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To Shane89, if you smell fuel at the exhaust, it's either the spark is missing causing unburned fuel to exhaust or a fueling problem.
Pull one spark plug wire at a time while idling and see which cylinder is not firing.
Then move on to fuel pressure check and T/B injector checks.
 

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Peter, the max on the acceptable fuel pressure range of 9-13 psi is only 13psi. Why install an 18 lb spring? Is 18 lb the max on the spring and 13lb is the mid range of adjustment?
No, I have some go fast parts on my engine - bored 46mm Throttle Body, Edelbrock intake, aluminum heads, cam, headers, high flow cat and straight through muffler. In order to achieve 14.7 AFR while cruising and ~12+ At WOT, i need more fuel. with my stock 61LB/Hr @13PSI injectors will put out 75.7 LB/Hr @ 20 PSI which I had the 18LB spring adjusted to. When I had the 28 PSI spring in I got 89.5 LB/Hr each. With just 18LB/Hr spring WOT @~5400 RPM my injectors were firing at 106% DC which means they were open all the time. With 20LBS I'm @ ~93%. With 28LB spring I was @ ~80% with ~12 AFR.

This is a trick when tuning rather than spending $$$ for different size injectors, springs are cheap! (y)

BTW, I have an AC Delco EP381 fuel pump from a 96 Vortec truck - 155L/Hr @ 60 PSI (which will support 450 HP) as apposed to ~75L/Hr @13PSI (which only supports up to 230 HP) for a TBI truck.

I was just using the pictures for illustration purposes, not suggesting going with bigger springs on a stock engine.
 

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