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L03 TBI - Ran low on gas, is how this all began...
Hello all!
I'm going to start by saying I am a novice, and would appreciate assistance only as I've put in hours, and I mean hours into searching old threads, but no one has stated *solved* so the issue for me remains.
I was running rather low on fuel one evening, decided to push it home and get fuel in the morning. Well, a pizza run was required so I fired her up, drove along about 1.5 miles, noticed some performance issues, surging, RPM's all over so I went across the street, put in fuel, and the issues went on adding hesitation and stalling out when coming to a stop. After filling the tank, and adding in about half a bottle of Lucas Deep Fuel System Cleaner it ran no better over the next few days, and nearly killing me on the highway, the troubleshooting began...
When removing the Air Cleaner, I noticed that the passenger side Fuel Injector quit spraying, not even a drip. Just the sound of a loud suction.
-Tried swapping connectors on the injectors - Issue Remained
-Noticed taped wires, as if the pig-tail for the injectors was replaced by P/O. Removed tape, exposed wires, cut & replaced old pig-tail. - Issues Remained
-Replaced Fuel Filter - Issue Remained
The party whom replaced my fuel filter suggested a complete TBI Unit replacement from a Yard-Car...
Should I troubleshoot this situation from the Fuel Pump forward, or from the Fuel Injectors & TBI Unit backwards? Isn't it the Fuel Pump that would supply the pressure to the TBI & Injector Pod, thus if the pumps output pressure drops, there wouldn't be enough pressure to run both injectors, right?
Considering she ran fine before I was, what I now deem to be critically low on fuel.
Re: L03 TBI - Ran low on gas, is how this all began...
The fuel pump is cooled by the fuel in the tank. By running it extremely low on gas, you murdered the fuel pump. BT, DT.
An overheated pump might work so-so for awhile until it finally fails. You could rig a pressure gauge and test it, but it's a fairly common cause of death.
Re: L03 TBI - Ran low on gas, is how this all began...
Thanks Drew, Well I'll order a new pump tomorrow...
Now the question is do I find someone to cut the access panel or drop the entire a** and try and finangle a 3/4 full tank of gas down for the pump replacement?
Re: L03 TBI - Ran low on gas, is how this all began...
Drain the tank first. Pop the fuel line under the back end or under the hood, run it into a gas can and hotwire the pump either at the harness above the axle, or jump the red wire off the fuel pump relay to the positive batter post. It'll be the funny short red wire with a connector not hooked to anything.
Just drop the tank. The time spent cutting a hole, cutting fuel lines, splicing fuel lines, finagling the pump thru the hole, blah blah, you're really not taking a short cut by not dropping the tank.
Re: L03 TBI - Ran low on gas, is how this all began...
Dropping the a** it is, wow, I just had the rear end lowered today to install 2in coil spring spacers to keep from bottoming out on my 5th Gen Wheels... What else can I replace while it's lowered? Besides track bar, shocks and link pins (All recently replaced) on a budget?
Re: L03 TBI - Ran low on gas, is how this all began...
Originally Posted by 92RS-HeritageEd
Dropping the a** it is, wow, I just had the rear end lowered today to install 2in coil spring spacers to keep from bottoming out on my 5th Gen Wheels... What else can I replace while it's lowered? Besides track bar, shocks and link pins (All recently replaced) on a budget?
i just did this job 3 days ago. panhard/track bar, shocks, springs, and sway bar endlinks are whats needed to be disconnected. Everything else can stay connected to the rear. Exhaust needs to be cut in the back as well to lower the tank.
Re: L03 TBI - Ran low on gas, is how this all began...
Cutting the exhaust? I did want to modify my exhaust, to get more of a growl... but not under these conditions. You're sending me into a Code Brown Ghettobird52, any more surprises and i'll have to change pants!
Re: L03 TBI - Ran low on gas, is how this all began...
If the exhaust still has the bolt together flange at the cat-con, disconnect it there. Then remove the right rear tire/wheel and move the exhaust out from under the tank via the passenger side.
Re: L03 TBI - Ran low on gas, is how this all began...
Originally Posted by 92RS-HeritageEd
I noticed that the passenger side Fuel Injector quit spraying, not even a drip...
-Tried swapping connectors on the injectors - Issue Remained
You put the connector for the driver's-side injector onto the passenger-side injector, and the passenger-side connector onto the driver's-side injector. The injector that worked before continued to work, and the one that didn't, still didn't. One injector works, therefore you have fuel pressure and fuel supply from the fuel pump filter sock, through the regulator. Both harness ends supply power and ground, verifying the wiring all the way back to the computer, and to the battery.
You have a failed injector. It's plugged, or it's jammed internally so that the solenoid doesn't move.
I cannot believe that people are telling you to drop the tank without you having ever testing the fuel pressure. If you WANTED to replace the pump because you suspected that it was near the end of it's service life...fine. I did that with my 130K mile Trailblazer, and my 120K mile Lumina. But you aren't dropping the pump "because", you're trying to fix a driveability problem, and for that some logic is needed--not just flinging parts at the car and hoping for the best. Your fuel pump may or may not be worn 'n' wounded...but it's NOT the cause of the engine's performance problems.
Re: L03 TBI - Ran low on gas, is how this all began...
Originally Posted by Schurkey
I cannot believe that people are telling you to drop the tank without you having ever testing the fuel pressure. <snip> But you aren't dropping the pump "because", you're trying to fix a driveability problem, and for that some logic is needed--not just flinging parts at the car and hoping for the best. Your fuel pump may or may not be worn 'n' wounded...but it's NOT the cause of the engine's performance problems.
Hold up a second there, Chief... You seem to have missed this -
You could rig a pressure gauge and test it, but it's a fairly common cause of death.
Lemme break it down for you... If a person were so inclined, there are diagnostic steps to further isolate possibilities. It's up to him if he wants to be more thorough or jump ahead. He described a scenario, and I gave him one possible explanation. It's up to him to apply that information. No one told him to just jump in there and start throwing parts at it. He asked the second question if he should cut a hole, or disassemble, and I made a suggestion. That's no more telling him to do something than giving an equally theoretical diagnosis in bold text...
Example:
You have a failed injector.
And you better believe if you cook a pump, you'll have stalling, hesitation, backfiring, the inability to maintain speed on the highway, etc. Might still seem to run decent at idle or revving out of gear, and only act up under load. Might work fine for the first five or twenty minutes after a cold start, until it leaves you on the side of the road...
Re: L03 TBI - Ran low on gas, is how this all began...
Originally Posted by Drew
Lemme break it down for you... If a person were so inclined, there are diagnostic steps to further isolate possibilities. It's up to him if he wants to be more thorough or jump ahead. He described a scenario, and I gave him one possible explanation.
No, you didn't. Weak fuel pressure does not permit one injector to spray, while the other does not work at all. Fuel pressure affects both injectors equally. Your diagnosis was not possible.
Originally Posted by Drew
It's up to him to apply that information. No one told him to just jump in there and start throwing parts at it. He asked the second question if he should cut a hole, or disassemble, and I made a suggestion.
His further questions about replacing the pump are based on a faulty line of reasoning. Other posters added advice on how to change a pump without considering that the pump isn't the problem in this case.
I described what "only one of my injectors works" actually means; along with what it means when the connectors are swapped and the same injector still works--and the other injector is still dead.
Yes, his fuel pump may (or may not) be wounded--but that's not the reason only one injector is spraying. FIRST we get both injectors spraying, then maybe we get concerned about the remaining service life of the pump. As an acknowledgement of human nature, I suspect that when that vehicle has two working injectors and the spark plugs get cleaned, it'll run just fine...and the fuel pump will be forgotten about.
Originally Posted by Drew
And you better believe if you cook a pump, you'll have stalling, hesitation, backfiring, the inability to maintain speed on the highway, etc. Might still seem to run decent at idle or revving out of gear, and only act up under load. Might work fine for the first five or twenty minutes after a cold start, until it leaves you on the side of the road...
For the record, I spent all day driving 160 miles in a '93 Lumina that, when the shop finally tested it, was generating 7 psi at the fuel rail instead of 47. This includes stalling a dozen times in minor-holiday traffic through the Truckee/Donner Pass on I-80, and stalling some more in 5-o'clock rush hour traffic in Sacramento. I know what a failing fuel pump with crap for fuel pressure runs like. It does not include "some" injectors squirting just fine, and others squirting nothing. They all squirt poorly, probably with excessive duty cycle, and the engine still runs lean if the pressure is low enough. This fuel pump failed at about 140K. The shop charged me more than $600 to change the pump and strainer, apparently because I got the "You're stranded more than a thousand miles from home, you're completely screwed, and we own you now" special price. I've changed the pumps on my other vehicles (including my '92 Lumina) at around 125K, 'cause I never want to go through that again.
Re: L03 TBI - Ran low on gas, is how this all began...
Originally Posted by Schurkey
No, you didn't. Weak fuel pressure does not permit one injector to spray, while the other does not work at all. Fuel pressure affects both injectors equally. Your diagnosis was not possible.
I wasn't as interested in what one injector or the other is or was doing as much as the larger symptoms and series of events he described. I couldn't possibly care less if one injector or the other doesn't seem to be spraying, because I honestly don't consider it to be much of a valid diagnostic.
I'm not familiar enough with TBI to know how it'd react to low fuel pressure. All the ones I've owned, and been around, were virtually trouble free. I have however experienced a dying fuel pump, and heard from enough other people who have experienced the same, to suggest it as a possible cause of the drivability issues the OP described.
Re: L03 TBI - Ran low on gas, is how this all began...
Thank you all for your interesting feedback, but assistance is still required, and appreciated. So my mechanic is onsite... and it was decided to troubleshoot from the TBI Unit back to the fuel pump since the TBI can be replaced with removal of about 3 bolts and 2 fuel lines vs dropping the rear end, etc.
-Replaced TBI Unit w/ Injectors and Injector Pod from a GM TBI Truck Engine (VIN K) -issue remained.
-Retried connector switch test, and the issue migrated. (I DIDN'T NOTICE THIS THE 1ST TIME)
How in TF am I to troubleshoot this godforsaken electrical matter? Just rolling the dice on this but can the injectors be wired in tandem? What suggestions do you all have?
Re: L03 TBI - Ran low on gas, is how this all began...
If the issue migrated when you swapped connectors, the issue is electrical, as you are already aware.
Do you have power to the injector connector when the ignition is "on"? No power, look for popped fuse (or damaged wire harness.)
If you have power to the injector connector, then there's likely a problem on the ground side of the circuit. The computer controls the ground to make the injector spray. No ground could be a wiring fault (open circuit) or a computer problem. Pull the wire harness connector from the computer, use an ohmmeter from injector connector to computer harness connector on the correct circuit to verify no open-circuit in the harness. If the harness isn't open...replace computer.
I'm sure there are additional steps, and more/better information in the real, live, GM service manual. I strongly advise you to get one for your vehicle from eBay or other source. I typically pay from $25 to $80 for them for my older cars and pickup.
Re: L03 TBI - Ran low on gas, is how this all began...
Thank you Schurkey,
After...Swapping back to the original TBI (Since testing proved it NOT to be the issue)
Removed the panel under the dash and this is what I found tucked...
*** With the silver box un-tucked the car runs***
- Both injectors fire consistently
- Car made 2 successful laps around the block
- Car completed a 15 Mile trip w/ no issue
While I would consider the matter resolved, I can't ride with the panel removed and ECM propped up, although in this position there's no flex or tension on the connectors to the ECM...and no performance issues.
Re: L03 TBI - Ran low on gas, is how this all began...
Perhaps you should unplug the computer and clean up the connectors. Either moving it caused the issue to clear up(softer than a whack with a hammer) or stretching the wiring made the questionable connection fit tighter and work.
Sounds like this worked out better than expected. Yay!
Re: L03 TBI - Ran low on gas, is how this all began...
Originally Posted by 92RS-HeritageEd
@heneryd3 & RBob, Thank you.
You're welcome.
I will try unplugging and cleaning the connections tomorrow. @RBob, are the PIN Locations on the connector you described shown in the Haynes Manual?
I wouldn't trust Haynes if they did print the pin out. The letters and numbers are molded into the connectors. Both the ECM side and the harness connector side. Need good light to see them. This link shows were they are on the harness side connectors:
Re: L03 TBI - Ran low on gas, is how this all began...
Ok, so...
I've unplugged the connectors, blew them out like old Nintendo cartridges. I've also taken the ECM in the house, cleaned the ports the connectors go into w/ rubbing alcohol. Reconnected the ECM, still in a propped position, car fired right up, and ran as expected with no issues.
I believe I've found that a Hypertech HYP-122362 chip has been installed by the P/O. Since I'm not removing it, I can't confirm or deny, it's only an assumption.
03-26-2017, 06:00 PM
from a Yard-Car...
Should I troubleshoot this situation from the Fuel Pump forward, or from the Fuel Injectors & TBI Unit backwards? Isn't it the Fuel Pump that would supply the pressure to the TBI & Injector Pod, thus if the pumps output pressure drops, there wouldn't be enough pressure to run both injectors, right?
