That's just the way your meter displays. Some do that, I have one that displays similarly. In your case that means you have a resisitance around 580 to 590 ohms. Thats too high for that system. As @budwich stated you likely have either a poor connector somewhere or a failing sender.
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- Thread starter Stuntmanmike1977
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That's just the way your meter displays. Some do that, I have one that displays similarly. In your case that means you have a resisitance around 580 to 590 ohms. Thats too high for that system. As @budwich stated you likely have either a poor connector somewhere or a failing sender.
@Stuntmanmike1977
I just re-read through this thread and would like to know if I understand the current situation correctly.
For some time now you do NOT have the check engine light on, correct?
Is it true that the issues right now are (A) you cannot fill the tank in the usual fashion as it backs up the filler neck and (B) the fuel gauge is not working correctly. Is this an accurate statement?
I just re-read through this thread and would like to know if I understand the current situation correctly.
For some time now you do NOT have the check engine light on, correct?
Is it true that the issues right now are (A) you cannot fill the tank in the usual fashion as it backs up the filler neck and (B) the fuel gauge is not working correctly. Is this an accurate statement?
Yes, that is correct. No engine light and the fuel gauge goes to empty when I shut off the truck. Every time I start it, stays on empty and the low fuel light comes for a second or two as it should then goes a click past full. I think I ruled out a bad stepper motor cause it does cycle and cluster was rebuilt with the upgraded steppers about 3 years ago. I was hoping for something easy I overlooked but, this thing was never easy.
The ohm meter is displaying kilo-ohms. Some digital meters actual show a small 'k' to indicate the ohm scale.
.580k-ohms is 580 ohms.
Just wanted to get my understanding straight.
The fuel gauge issue is either a poor connection or a failing fuel level sender.
It is my belief that none of these electrical troubles or sensors or solenoids have anything at all to do with the problem of filling the tank.
@Stuntmanmike1977 have you tried adding fuel to the tank with the C101 harness unplugged so the pcm doesn't get any signals from the fuel tank?
Or better yet, disconnect the battery ground terminal then try to add fuel.
Or better yet, disconnect the battery ground terminal then try to add fuel.
Maybe back a few pages, but have you tried your gas fill with the vent valve hose disconnected?
I'll try both of those. Will let you know. It's weird, ever since my wife ran the tank dry and got stranded even though it said quarter tank left it's been doing this
Vent valve disconnected, computer harness disconnected or both, still overflows. Now the whole filler neck is full.
do you mean the vent valve is electrically disconnected or that the hose going to the valve is disconnected?
Ah, but this seems slightly different than your early results where the neck was slowly emptying ... or am I misreading the observations?
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That was with the hose itself disconnected. It's draining but even slower than it was before. And that's not even the pressure from the pump, still using a gas can to put it in. Maybe if I can get at it today I'll replace the valve on the side of the engine since it's the only one I haven't done yet if that will help. Don't know if it's pulling vacuum or not.
The Evap valve hose disconnected should allow the tank to vent to atmosphere albeit through the canister. With engine off the purge valve is closed so changing the purge valve can only help remove pressure (add vacuum) when engine is on. Plus it's not typically pulling vacuum at idle. You said earlier you could not remove the canister but could you disconnect the hoses to it then try to add fuel?
Other than that i hate to be bearer of bad news but the fix may require a tank drop and inspect.
I was supposed to replace the fuel pump and straps tomorrow (if the strap bolts don't snap off). What am I looking for on top of the tank? And no, could not get the lines off the valve that's on the engine thought you meant the one behind the tank. After much thought though, is it really a good idea to put in a new and fairly expensive fuel pump if I can't really put barely any fuel in it?
I was just stating at this point I don't think the purge or evap valves are preventing fuel from entering the tank. The last thing you should try is disconnect the hoses at the charcoal canister next to the fuel filter. It will allow the tank to fully vent so you will pinpoint if the cause is likely a fuel tank internal problem if still doesn't receive fuel.
AmpOverload
Member
@Stuntmanmike1977:
IMHO, I would definitely not put a new fuel pump in now. I've seen absolutely no evidence that you need one. Solve the fuel-filling problem first, then go from there.
Given that (IIUC) you've manually vented the tank by disconnecting the hose that goes between the EVAP system vent valve and the fuel tank and you're still having problems with fuel not going into the tank, it seems to me that the most likely source of that issue (ignoring any other EVAP system issues for the moment) is a problematic "rollover" valve (a.k.a. "fuel check valve" or "fuel inlet valve"). If that valve isn't open far enough, it would explain your immediate issue. In fact, @Mooseman (in post #75) and @Aroc (in post #139) have already pointed you in that very direction, but I don't see that you've ever fully addressed that possibility. Or if you did, I didn't understand you (e.g. "The original valve is free, just won't go in." -- I'm not sure what that means, frankly).
I've looked at various sources of information about the fuel system on a 2003 TrailBlazer. IIUC, the fuel check valve can only be replaced by dropping the tank, so if you're going to drop the tank, you should probably be prepared to inspect and to test (and maybe even to replace) that fuel check valve.
IMHO, I would definitely not put a new fuel pump in now. I've seen absolutely no evidence that you need one. Solve the fuel-filling problem first, then go from there.
Given that (IIUC) you've manually vented the tank by disconnecting the hose that goes between the EVAP system vent valve and the fuel tank and you're still having problems with fuel not going into the tank, it seems to me that the most likely source of that issue (ignoring any other EVAP system issues for the moment) is a problematic "rollover" valve (a.k.a. "fuel check valve" or "fuel inlet valve"). If that valve isn't open far enough, it would explain your immediate issue. In fact, @Mooseman (in post #75) and @Aroc (in post #139) have already pointed you in that very direction, but I don't see that you've ever fully addressed that possibility. Or if you did, I didn't understand you (e.g. "The original valve is free, just won't go in." -- I'm not sure what that means, frankly).
I've looked at various sources of information about the fuel system on a 2003 TrailBlazer. IIUC, the fuel check valve can only be replaced by dropping the tank, so if you're going to drop the tank, you should probably be prepared to inspect and to test (and maybe even to replace) that fuel check valve.
Try disconnecting the charcoal canister hoses. Let us know if that works or not.
AmpOverload
Member
That's a very good point. This image shows the EVAP system hose routing for a 2003 TrailBlazer:
- EVAP Canister Purge Solenoid
- EVAP Canister
- Fuel Fill Neck/Fill Cap
- Rollover Valve/Fuel Tank Pressure (FTP) Sensor
- Fuel Tank
- EVAP Canister Vent Solenoid
- Vent Hose/Pipe
- EVAP Vapor Pipe
- EVAP Purge Pipe
- EVAP Service Port
EDIT: Sorry! Hose #8, not #7!
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I meant that the spring loaded flapper in the tank inlet was free. Tested about 30 times by now.
AmpOverload
Member
OK, good to have that clarified. But that's not what's (potentially) preventing your tank from filling. It's this part:
https://www.rockauto.com/en/catalog...77,fuel+&+air,fuel+tank+roll+over+valve,19591
The valve your all talking about is that circular one on top of the tank? Never thought about that one. But, need to drop the tank anyway to check that valve. How would I test that and is it even available? Will try the charcoal canister line first. The one that goes to the vent valve is clear. The one that says To Tank is the one I have to blow out when I get the tank down. Was gonna replace the pump/sender unit to fix the stuck on full gauge issue. Have not had a problem with this issue since my wife Ran the pump dry and kept trying to start it. Still read quarter tank. That was about almost 3 months ago. Ever since then it just got worse and worse. Now, it's even starting to stall and runs like crap but I'm pretty sure that's the fuel filter which I'm changing too.
Just found the link for that valve. Hopefully mines not broken. Don't have the means to rig one up that good.
AmpOverload
Member
No, I think you may be confused. Go to that RockAuto link, click on the Dorman part, then download the PDF installation instructions for that part. In step 12, you should see a picture of someone using a big Crescent wrench to tighten that "rollover" valve that I'm talking about.
Did you click on my link?
That's wise (and inexpensive).
OK, well, in that regard, I moderate or even might retract my statement about "absolutely no evidence that you need one", but I meant evidence of the pump not pumping. Replacing a pump to fix the gauge is certainly done a lot, but it's not what I consider "cost effective".
Well, if you've already bought the pump and it gives you peace of mind, then it certainly would be a good time to replace it when the fuel tank is dropped to diagnose a possibly misbehaving "rollover" valve.
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AmpOverload
Member
The rollover valve I think you mean is that the aluminum one you have to feed through the fuel pump opening and cut the old fill inlet off the tank? About 120 bucks for that part. Kinda out of money when I bought all that other stuff. I'll have to wait on that one and get the supplies I need to smooth out the inlet opening to insure a leak proof seal. If that's the one your talking about.
Dorman 577-106 Fuel Filler Neck Inlet Check Valve Compatible with Select Chevrolet / GMC Models (OE FIX) https://a.co/d/04ow6vxC
AmpOverload
Member
Yes, that's the part I'm referring to. You do have one of those on your tank, don't you?
If your rollover valve is anything like the one in those instructions for the Dorman part, then you shouldn't be cutting anything. Did you see step #12 where they "Tighten locking ring"? You should be able to loosen that locking ring (assuming you decide to replace that rollover valve), after tying a cord around it, and fish it out of the tank via the same fuel pump opening atop the tank into which you'd fish the new rollover valve.
I have this uneasy feeling that you have not downloaded and read that PDF from the RockAuto Dorman page. If that's true, I strongly suggest you read that and familiarize yourself with the part and its replacement.
Also, have you been able to disconnect the EVAP cannister's lines as suggested previously, to be sure that is/isn't the problem?
there is still something funny, if you have the "venting" disconnected so that its allowing "free air flow", then filling should function "normally" especially with a gas can fill. I suggest you get a long plastic or solid copper / steel line of small diameter and feed in down the filler neck into your tank. Use you gas can and try a fill. The wire / steel line should be holding the flap open and allowing for both gas and air to flow in either direction.
My tank is 100% original. Still have the original molded to the tank plastic nipple.I can't see a link for the PDF. Yes, removing the canister line did nothing.
AmpOverload
Member
OK, I think I'm starting to understand why you said "cut the old fill inlet off the tank". That would make sense if GM failed to design the original rollover valve to be replaceable. Typical GM.
That RockAuto link to the Dorman "inlet valve" says:
I assumed that the original part was similar, based on that "direct replacement" wording. If not, maybe you do have to cut the original valve off somehow. Shame on me for assuming. Sorry for the confusion.
So, IMHO, I think you need to now see if that rollover valve is preventing you from adding gas. It seems like the last remaining suspect in this mystery, right?
I could link to the PDF directly, but there is useful information on that RockAuto page for the Dorman part (#577106) that you might want to look at. The PDF is on that same page, under the "Additional Resources" section, as "Install/Removal Instructions".