Fuel issues

[Ferrnt]

03 2500 Suburban (Dual Tank/Fore and Aft/No Switch) ​and I apologize up front for the length and amount of information.

 

Sitting in a parking lot waiting, the Burbans idle became irratic but never died. Put it in drive and it died 5 seconds later. Started right back up and drove for 5 seconds and it died. Did this 3 more times before I was able to get it to stay running and haul *** home (1 mile) and it died 50 yards from the house but speed allowed me to get it up into the driveway.

 

It would start right back up but die 3 seconds later for days. Trouble shooting with automotive mechanic friends they all said it was the fuel pump. I was getting about 12 to 15 psi for primer pressure. This is when I discovered I have two tanks. They both said it was the aft tank pump that has failed. Replaced it and the inline fuel filter. It started right up and ran for about 10/15 mins then died. Cleaned the MAF, throttle body, connectors, checked PCV, alternator connector, battery for a dead cell, and various others. Mechanic buddy was disconnecting various connectors (trying to isolate) while I started and still same 3 second run. While attempting starts, doused the entire engine compartment with Carb Cleaner and Starting fluid looking for a vacuum leak. No rise.

​I did get three error codes 171, 174 and 220 during this process. We looked into it, could not duplicate. Cleared them and now not getting anything with the 2/3 second start. After trouble shooting with the seasoned mechanic at the local parts store, ended up replacing the "fixed non adjustable" TPS on the peddle. Car still cranks but now do not get the 2/3 second run. I can run it by blowing through a can of starting fluid through the MAF. I did swap the fuel pump relay with another, same results. Cannot locate a fuel pump fuse. Also, no longer hear that 5 second primer pump run.

 

One question, my aviation experience tells me that the primary tank is the forward (larger) one and my secondary is the aft (smaller) one. However, my buddies tell me different. Which is primary tank and which is secondary tank. Also, there is a pump in each tank, however, is there a 3 pump that acts like a XSFR pump?

 

Again sorry about the length, but I figured I would eliminate some questions you guys may have. Your help would be greatly appreciated.

[Jsdirt]

I think you're right on which tank is which ... but who knows what GM says on that one.

 

What is the fuel pressure now after the pump replacement? Is it the same? Was there any change? If not, then the pump you removed is probably fine - you've got a wiring issue.

[Ferrnt]

The pressure was the same after replacement, however now that the TPS has been replaced, I get no pressure at all. That is why I started to trouble shoot electrical.

​Also, side note... Although purchased new, late in 03... I think I have a late 02, early 03... The pump I yanked out of my 03 did not match the 03 pump that was ordered. The aft pump that was ordered only had 1 electrical connector where as mine had 2. Turns out (at the auto store), we found out that the aft pump was an 02 model in my 03 Burban.

[Jsdirt]

Strange one there. The TPS is completely unrelated electrically to the fuel pump.

 

Sounds to me like some bad wires were moved around during the TPS replacement, and that caused the pump to quit. That was probably the initial reason for the low output.

 

Going to have to check all that wiring out section by section.

 

I sent you a PM, btw - check your inbox.

[Ferrnt]

Jsdirt... Thanx for the PM. I hated chasing sparks an ringing out wires on aircraft. Hate it more on my own car. If I find something I'll post.

[Jsdirt]

Oh I hear you there. I miss my '72 El Camino badly!

 

10-4, sounds good.

[Duelin]

I would be looking at the pump in the front tank. That should be the primary tank and primary fuel pump. And you say it will run if you hit it with starting fluid. Also you say you don't hear the prime. You could try hitting the front tank with a rubber mallet and see if the pump will run. Sometimes they will start running from the vibration. As far as I know the rear tank pump is just to transfer fuel from the rear tank to the front tank. I am sure if I am wrong someone will jump in and correct me. Also there is different pumps for different fuel systems. I think there is a system they call Robust Fuel systems. So If you have to replace a pump you will need your VIN and RPO codesto get the correct one.

[Ferrnt]

Update:

​Spent all night ringing wires, much to my 16 yr olds chagrin (he was helping). Dead ends or I just was wrong. However, finally dropped the "brush guard" off the main tank. Cycled the key. Nothing. Brought "boy wonder" out to cycle the key while I beat the bottom of the tank. Had noise. Wasn't the pretty whirl that a fuel pump normally makes. More like grumble, groan, slow buzz. Eventually got pressure at the fuel rail. Just took a bit. If this isn't my only problem, it is one of them. I now have to figure out what to do with 25 gals worth of fuel. I only have one "jerry can". They cost $20 a piece out here in California. Guess I'll do it 5 gals at a time and put it in other cars or even the neighbors.

​Gonna drop the main, and replace that pump. I'll keep you posted. TY Jsdirt and Duelin.

[Ferrnt]

So... after chasing my tail for weeks, seeking advice from mech friends and then coming here. Might (we) have figured it out.

​Finally drained the big tank. Mind you, my tank looks like my 5 year old got crazy with playdoh. It looks nothing like the pics in the Chiltons or online pic or self help video's online. My pump is no where near what I saw and I have less lines in one spot and more in another. I'll post a pic.

Swapped the FWD tank pump...Poured 5 gals in... didn't wanna run. On a hunch went and got 5 more. She fired right up and ran for 30 mins in the driveway. Took her on a 6 mile drive up and down hills... no hick ups... fingers crossed.

​Guess I can't upload a pic of the tank or and excerpt out of the Chiltons manual I had a few more questions about.

​That said thank you for your input. I hope I don't have to reactivate this thread.

​

[Jsdirt]

Nice - glad you got her going!

 

If you got the old one to make SOME noise by rapping the tank with a hammer, then it's got one or a few dead commutator strips in it - sounds like you made the right call swapping it.

[Ferrnt]

So update...

​I would like to thank those who have posted here to assist.

​She's good. Runs like a champ. Took her to L.A. and back with no issues

​However... this is something that has been happening since 2015. Every once and awhile I get a "Low Power" or "Reduced Engine Power" message. Cant get over 25 mph. I pull over, pull out my scanner (that I conveniently leave in the back of the burb now) read the code it comes out to 220. I clear it and it operates correctly. It states the same but adds "circuit B". It states that my TPS is out, however, I replaced it during my recent endeavor.

 

Any thoughts?

[Jsdirt]

Sounds like the sensor is bad, or you've got wiring issues somewhere. Sensor B is on the throttle body.

 

Here's a good article on troubleshooting. I didn't read the whole thing, but looks good from the 1st page:

http://easyautodiagnostics.com/gm/4.8L-5.3L-6.0L/p0220-tp-sensor-tests-1