# Cruze Eco gas tank volume solved!!!!



## cruze1953 (Jun 30, 2011)

The 2011 Cruze Eco has 3 seperate vents, 2 built into the tank and one on the fuel pump module. I could not get more that 9 gallons in the tank without the auto shut-off clicking and then fighting to get the other 3 gallons that the DIC would show I used. The vents are float type which shut off when the fuel level reaches about 3 inches below the actual top of the tank. 2 are heat sealed into the tank plastic and could not be removed or modified but the third one is on the fuel pump module. I designed a new vent tube way at the top of the vent assembly, above the valve seat and ran a new 1/4 fuel line vent to the small steel vent tube that runs along side the large filler tube. It worked perfectly the first fill, I could hear air coming out of the vent at the gas cap while filling which I never heard before and it went right thru 9 gallons. I had about 1-1/2 gallons left in tank, I drained out 1 gallon before removing and about 1/2 gallon remained, I put in 11.3gallons+1 1/2 already in tank would give me close to the 12.6 gallon factory rating. As long as I don't overfill the tank, new vent hole is about .187 inches, no fuel should make it back into the carbon vapor canister because the hole is directly under the top plate of the fuel pump module and the vent tube it at the very top of the vent connecting the fuel pump module with the canister. It seems like the tank was way over designed especially when they were cutting weight. Now I will use the DIC to get close to the fuel volume used and never try to top-off the tank completely. BTW 1 1/2 gallons showed as the first mark on the gauge before empty mark, now that I see the low volume of fuel left , I will start filling up at 1/4 tank left to aid the pump in cooling itself.
You should never modify fuel lines or gas tanks because of the fire hazard and leak hazard. I have 35 years experience, owning my own automotive shop and took special precautions when installing the extra vent line and fittings.
I checked ALL-DATA for the 2011 Cruze Eco car and diagnostics on filling problems which were of no help so a redesign and modification was the only way to solve my problem.


----------



## 70AARCUDA (Nov 14, 2010)

...you need to append the Mythbusters' obligatory statement words, _"...*DO NOT TRY THIS AT HOME*..." _(ha,ha)!

...excellent information!


----------



## maven (Feb 27, 2011)

if this is a fresh air vent good luck keeping P0455s from setting. You just created an EVAP leak.: )


----------



## sedanman (Dec 10, 2010)

First of all I thought it was a 15 gallon tank? Secondly, I never fill my tank more than half way for weight savings and to have fresher gas in it by filling it more often. Thirdly, I feel bad for the person who buys this car used and fills the tank all the way. Hope you inform them!


----------



## GoldenCruze (Dec 18, 2011)

The Eco has the smaller tank. The other trim levels have the 15.5 gallon tank. Smaller tank in he Eco for saving weight.


----------



## maven (Feb 27, 2011)

GoldenCruze said:


> The Eco has the smaller tank. The other trim levels have the 15.5 gallon tank. Smaller tank in he Eco for saving weight.


Its not a smaller tank, just a forced lower capacity.


----------



## montgom626 (Jan 16, 2011)

maven said:


> Its not a smaller tank, just a forced lower capacity.


Really? Wow, that is amazing. How do they force it to be smaller?


----------



## FatKidsCruze (Sep 2, 2011)

Basically a vent that creates pressure of a full tank at 12.6 gal instead of 15.5.


----------



## montgom626 (Jan 16, 2011)

FatKidsCruze said:


> Basically a vent that creates pressure of a full tank at 12.6 gal instead of 15.5.


Nice to know. Now, is there a "safe" way to allow 15.5 gallons? Imagine the range of an ECO!


----------



## FatKidsCruze (Sep 2, 2011)

There was a thread on here somewhere, not sure there is a "safe" way but it's possible.

Here ya go:
http://www.cruzetalk.com/forum/9-ch...542-every-eco-owner-needs-know-confirmed.html


----------



## limited360 (May 6, 2011)

I can put 13 gallons into my ECO without this modification, takes a bit of time and a patient hand.... I did over 700 miles on one tank of gas on a road trip in my ECO M6 this way...


----------



## tedstiles (Mar 24, 2012)

GoldenCruze said:


> The Eco has the smaller tank. The other trim levels have the 15.5 gallon tank. Smaller tank in he Eco for saving weight.


It's not smaller, but it does not let in the last 3 gallons. I've put in 3 extra gallons beyond the click shut off at the pump. I also drove it 271 km before the gas gauge started to move. Amazing!. 

QUESTION: why does cruze1953 mention 12.6 vice 15.6?


----------



## CHUV (Jun 25, 2011)

maven said:


> if this is a fresh air vent good luck keeping P0455s from setting. You just created an EVAP leak.: )


An evap leak would cause the engine to shut off...


----------



## NickD (Dec 10, 2011)

Fuel evaporative systems are a constant problem, essentially consist of a vent and purge solenoid valve, a way overpriced carbon canister, and a full tank pressure sensor. When cruising, the PCM is timed to play games in testing out this system.

A huge downfall with the Cruze is mounting both the vent and canister way back at the fuel tank, where subject to plenty of road debris. Were far less trouble free when mounted high in the engine compartment.

Due to the fact the fuel pump itself is a piece of junk and depends upon fuel flow for cooling and mounted in the tank, very labor intensive to change these with no easy means to drain the fuel from the tank. And that fuel pump is indubitably a throwaway item. Made of plastic in a tin can with a cheap permanent magnet brush motor, but they do use brushes that are about 3/4" long for longer life. The carbon in these brushes ends up plugging up your injectors.

We proposed using a slightly more expensive brushless DC motor, out of the question, but yet they have the never to charge anywhere from 100-450 bucks for these pieces of crap. Always has a tiny plastic ball that seats in plastic for a check valve to keep starting pressure so you are not cranking your engine for a half a day to start your vehicle. That is why your fuel pump operates for two seconds, but only if you leave your key in the run position for those two seconds. If like most of us, jam that key in and instantly switch it to start.

In theory at least, a sealed gas tank would explode if not vented, in particular with a full tank. In particular if you fill your tank on a cold morning and the temperature rises during the day and your car is parked in the hot sun. That vent solenoid valve has got to be left open and exhausts fumes to that charcoal canister. But they are never made large enough under worse case conditions, still will get fuel leakage.

When the engine is started and allowed to warm, that vent valve closes and the purge valve opens purging in theory, the fumes from that canister back into the intake manifold. This creates negative pressure in the fuel tank, not very much, about 0.2"/Hg, but with that filler with cheap rubber hoses, and three fuel lines, the regulator, any minor air leak, and you won't get that pressure so generate an evaporative fuel system code. This is all done electronically with connectors under the vehicle also exposed to road debris. In the north, primarily slushing salt ridden snow that causes corrosion in these connectors.

And not only fumes are drawn back into the intake manifold, but carbon from that canister as well that also gives problems with fuel injectors. That carbon also prevents that vent solenoid valve from completely closing generating a code. If you get on the internet with fuel evaporative codes, 99% of the idiots will tell you, you left your gas cap off, you should be so lucky. These are not easy systems to troubleshoot, beside mechanical, can be electrical as well. A smoke test must be used to determine if its a mechanical related problem, then electrical test equipment for the rest. The fuel sender and pump gasket on top of the tank is another source for an air leak. Would be nice if Cruze and others put an access plate under the rear seat for ease of maintenance, but your stockholders won't hear of that. 

Its never a good idea to fill your tank, drive a couple of blocks then leave your car parked in the sun. I only fill the tank when I know I am going to drive at least 40 miles to burn off at least a gallon of gas to prevent that overflow. Especially at over four bucks a gallon.

Fooling this this system, if caught, not every likely, but can cost you a $25,000 fine from the EPA. EPA also requires you jam that fuel nozzle until that rubber gasket on the neck of the filler tube. Not the least practical, the pump will click off before you engage it. To top off the tank, have to barely open that vent door in the tank and hold the nozzle exactly parallel with it, with short bursts on the pump trigger until gas starts to overflow on the filler.

Yeah, I would like to modify my fuel system as well, first move that canister and vent solenoid under the hood where it belongs, even the pressure switch can be move to eliminate all that under vehicle wiring. Get rid of that cheap thick film carbon fuel sender and install an ultrasonic fuel lever sensor, and use a quality external fuel pump.

But to do this, would have to go through the expense of having these modifications approved by the EPA, next to impossible, and show that documentation to my insurance company. Even if my car was parked and someone ran into it, would void the claim, because I did unauthorized modifications to my vehicle. So have to learn how to live with it.

I am not kidding on these issues.


----------



## obermd (Mar 3, 2012)

tedstiles said:


> QUESTION: why does cruze1953 mention 12.6 vice 15.6?


12.6 and 15.6 are the advertised tank sizes on www.chevy.com as well as in the US owner's manual.


----------



## cecaa850 (Apr 9, 2012)

cruze1953, did you ever pull the tank and look at the module itself? I would imagine that there is some sort of a float or ball in the module beneath the vent hook up line. Removing or lodging it so it wouldn't move should allow you to fill the tank completely without altering the external vents. Just a theory.


----------



## cecaa850 (Apr 9, 2012)

If the tanks on an auto and MT are the same, the difference in fill level must be in the fuel pump modules. The modules on the MT's and auto's have different part numbers. I'd love to have one of each on a bench to see what the differences are. I'd also like to know if an auto fuel pump module would work in a MT car. My guess is that it would.


----------



## obermd (Mar 3, 2012)

cecaa850 said:


> If the tanks on an auto and MT are the same, the difference in fill level must be in the fuel pump modules. The modules on the MT's and auto's have different part numbers. I'd love to have one of each on a bench to see what the differences are. I'd also like to know if an auto fuel pump module would work in a MT car. My guess is that it would.


Since the other Cruze Trim MTs use the fuel pump assembly that allows 15.6 gallons before "first click", it's a safe guess that that assembly will work in the ECO MT. It's only the ECO MT that has the "shorted" assembly. This design decision has got to be costing GM both in the manufacturing of a second part as well as the support logistics and training of their technicians.


----------



## ChevyCruzeLTZ (Apr 7, 2011)

CHUV said:


> An evap leak would cause the engine to shut off...


No, it would not. If you don't believe me unscrew your gas cap and start your car.


----------



## cecaa850 (Apr 9, 2012)

obermd said:


> Since the other Cruze Trim MTs use the fuel pump assembly that allows 15.6 gallons before "first click", it's a safe guess that that assembly will work in the ECO MT. It's only the ECO MT that has the "shorted" assembly. This design decision has got to be costing GM both in the manufacturing of a second part as well as the support logistics and training of their technicians.


If that's the case, I might just find out how much one runs.


----------



## cecaa850 (Apr 9, 2012)

obermd said:


> Since the other Cruze Trim MTs use the fuel pump assembly that allows 15.6 gallons before "first click", it's a safe guess that that assembly will work in the ECO MT. It's only the ECO MT that has the "shorted" assembly. This design decision has got to be costing GM both in the manufacturing of a second part as well as the support logistics and training of their technicians.


I just found out that the modules AND sending units (purchased seperately from the module) are different part numbers on the 2 different tank capacities. Maybe the 15.6 gal sender will reach the top of the tank. If so, it makes me think this is doable as the software in the 2 vehicles may be the same.


----------



## cruze1953 (Jun 30, 2011)

Not true on the evap code, all I did was allow vapor to escape from tank properly. One evap code was set after first start, then I reset and retested, vapor tank vacuum reading was normal and has never reset after 6 refilles. 

Gary


----------



## Ccantrell56 (Apr 24, 2012)

cecaa850, do you have the part numbers? i would like to find out how much the AT parts coud be purchased for and see if i can find out if they will work on the MT car. Thanks, ccantrell56.


----------



## cecaa850 (Apr 9, 2012)

Ccantrell56 said:


> cecaa850, do you have the part numbers? i would like to find out how much the AT parts coud be purchased for and see if i can find out if they will work on the MT car. Thanks, ccantrell56.


Let me make a call, I should have written it down but I didn't. My car should be in this week and I'm thinking about having the dealer swap it out before I pick it up, that is if they don't have a problem "modifying" a new vehicle. I can't see where it wouldn't work. Both sending units should have the same resistance when full. The new module should take care of the premature fill-stop issue. There may be something I'm overlooking however, it may be one of those "try it and see if it works" things.


----------



## NickD (Dec 10, 2011)

Suppose a definitive answer to this question would be to crawl under each vehicle with a tape measure. Tried to find part numbers, a bit too early for that now.

When we first heard about the Cruze, was nothing but the Eco. But then it occurred to me that Eco is short for ecologists and they are also using a green label for green people. Since I met just too many eco green people that really get carried away way overboard on this subject, didn't want to buy a vehicle that identified myself with this group of people. So got a 2LT instead. Actually an LT, while separate individual pasted on letters, looking for a matching "2".

Gas weighs six pounds per gallon, always top off before taking a long trip, so for the first 120 miles or so, we start of carrying an extra 18 pounds. But then, just like an Eco, well not exactly, still have a spare tire and cup holders in the rear seat. 

In our first experience with an Eco, wanted to see what was under that hatch in the trunk. I safely removed that plastic snap, salesman on the right side broke his off so we couldn't lift it. So still wonder what's under that hatch. Know whats under the hatch in my 2LT, doesn't have those cheap plastic snaps. Find a spare tire and a jack if I need that.


----------



## cecaa850 (Apr 9, 2012)

NickD said:


> Suppose a definitive answer to this question would be to crawl under each vehicle with a tape measure. Tried to find part numbers, a bit too early for that now.


If you're talking about part numbers on the tanks, they're the same.


----------



## Ccantrell56 (Apr 24, 2012)

cecaa850, i'm talking about the modules and sending units you mentioned in your earlier post. What are the part numbers for the AT versions? Thanks, ccantrell56.


----------



## cecaa850 (Apr 9, 2012)

Ccantrell56, I understood your post, my comments were directed to Nick. I'll see if I can get them tomorrow for you, I have to make a couple calls and I've been busy at work.


----------



## cecaa850 (Apr 9, 2012)

Here's what I've been told. The fuel pump module for the larger capacity tank is 13579908 and sending unit is 13504670.


----------



## Ccantrell56 (Apr 24, 2012)

cecaa850, can you get the part numbers for the eco MT also? I would like to see if I can find out what is different about them. Thanks, ccantrell56.


----------



## NickD (Dec 10, 2011)

Supposed I could have looked it up, 13580533 is the fuel level sensor with the 13 gallon tank, and 13504670 is the number without the 13 gallon tank, must be the 15.6 gallon tank.

So are they just changing the resistance of that thick film resistor or just making the float rod a tad bit longer? been fooling around with GM fuel senders for years, stay at full for half the trip, then drop to nothing the other half, seem to be doing a better job with that now.

Fuel pump also varies 13577825, 13580532 with the 13 gallon tank, 13321034 without it, expensive little suck for a piece of plastic. 









Fuel filler tube must also be different for that cut off feature, but can't find that.

By doing my homework first, just said the heck with the Eco for some of these reasons. With the 2LT 15.6 gallon tank, just stick the nozzle in half way and set the pump to the lowest speed. This gives me an opportunity to kick the tires and clean off all the bugs from the windshield. If I squeeze the pump trigger, just a tad, gas overflows from the top of the filler and have more to clean up. So don't do that anymore. Tank is topped off.


----------



## cecaa850 (Apr 9, 2012)

Ccantrell56 said:


> cecaa850, can you get the part numbers for the eco MT also? I would like to see if I can find out what is different about them. Thanks, ccantrell56.


The difference won't show up on the part number. The only way I'm aware of to see the difference is to have them both side by side on a bench. Everyone at this point is just speculating the differences between the two units as no one has pulled one out yet to the best of my knowledge.


----------



## cecaa850 (Apr 9, 2012)

NickD said:


> So are they just changing the resistance of that thick film resistor or just making the float rod a tad bit longer? been fooling around with GM fuel senders for years, stay at full for half the trip, then drop to nothing the other half, seem to be doing a better job with that now.
> 
> Fuel filler tube must also be different for that cut off feature, but can't find that.


A few more assumptions: I would think the float level arm would be the difference between the 2 units as MT ECO owners that force fill their tanks report extended mileage BEFORE the needle starts to drop as opposed to a normal fill up.

I would also think that the filler tubes are the same but the vent shut off feature may be built into the module itself.


----------



## NickD (Dec 10, 2011)

I don't care speculate, probably good that 1,500 buck additional rebate died last spring just ten hours before we came darn close to purchasing an Eco. Wasn't hot on getting a black cloth interior, but lived with that before, nor the 13 gallon fuel tank, not easy to find ethanol free gas, but maybe would carry a can with me, nor lack of a spare tire, but was telling myself the last time I had a blow out was twenty years ago. Was making compromises I didn't like. Also buying a 2011 at the end of the year, amazing how this affects tradein value.

Then just a couple months later, came out with the 2012 with a MT in the 2LT and all the other options and colors I wanted. Didn't have one within 500 miles of me, so ordered one exactly the way we wanted it. Was another short six week wait, but do have other lives to live.

See guys trying to add cruise controls, ha, the way I drive without cruise, would be in jail without it, would be going 108 mph, so that was an absolute requirement. Then you look at the ridiculous prices they want for parts to make these modifications.

Wife also wanted that radio navigation, said no way was I going to pay a thousand bucks for three bucks worth of a touch screen and two GPS chips. Chevy should be ashamed for these prices, then an extra 180 bucks for each map update, crazy. We don't even need that Garmin, have full GPS on our smart phones, but if a cop sees you holding a cell phone, can stop and hit you with a 70 buck fine.

It was also last spring I discovered my stepdaughters' ZX2 was unsafe to drive doing a brake job on it, rocker panels and suspension points were so badly rusted, the wrecking yard was the only safe place for it. It was in good shape the fall before. That put on family pressure on me to buy something new, used cars were out of the question, thanks to that clunker program, seen better cars at the wrecking yard.

To keep some peace in the family, handed my DeVille keys to my stepdaughter so she could earn five bucks an hour at part time job. She didn't like driving a grandpa's car, really wanted the keys to my Supra, said no way. But somehow she managed to survive and didn't care for my other option, she could ride her bicycle. But I got what I wanted.


----------



## cecaa850 (Apr 9, 2012)

Nick, is that the actual part? If so, can you tell what the red item is below the vent connector? Can you post a pic of the 12.6 gal pump assm?


----------



## tedstiles (Mar 24, 2012)

Hi Ed. I certainly wish you lived nearby because 'we' could do my gas tank over to solve the extra three gallon problem. Number one issue for me. I want 1000 km per tank. I'd fill up to the very top only when I'm going to do a lot of driving immediately afterwards. Ted Stiles 613 912 8747.


----------



## obermd (Mar 3, 2012)

tedstiles said:


> Hi Ed. I certainly wish you lived nearby because 'we' could do my gas tank over to solve the extra three gallon problem. Number one issue for me. I want 1000 km per tank. I'd fill up to the very top only when I'm going to do a lot of driving immediately afterwards.


1,000 KM (622 miles) per tank on the ECO MT is certainly doable. I've had two tanks well over that but normally don't care. If you trickle fill the tank after first click off you can avoid modifying your fuel pump assembly. 40 MPG @15.6 gallons will get you about just over 1000 KMs. 45 MPG will require 13.9 gallons, which if you are on the highway a lot is easy to do.


----------



## NickD (Dec 10, 2011)

Ha, besides not being able to pay a hundred bucks extra for a spare tire with the Eco with a manual transmission, three gallons less was even more motivation to look into the 1 or 2LT.

Like getting on the interstate with a full tank of gas and for the first 120 miles or so, see no difference in fuel economy for that first 120 miles, then the rest, gee I have an Eco now with 18 pounds less of gas! How come my fuel economy is not increasing?

But actually only have less than 9 gallons left, learned from years of experience, how many years? My 1970 Buick Riviera was the first vehicle I owned with an intank electric fuel pump. Need at least a quarter of a tank of fuel in these things for fuel pump cooling, if lower than this, darn thing will start burning itself up. So treat a quarter full gas tank like an empty one. Hmmm, this was 46 years ago.

So with an Eco you effectively only have a nine gallon tank. What you don't want to do is to toss a ten pound bag of sugar in your trunk, that will cancel everything out! So why does it even have a trunk?

Yeah, I know, more stupid questions, ha, I like asking stupid questions. You could carry a five gallon gas tank in the trunk, but not very wise, really exposed to a fire hazard if rear ended by a drunk driven SUV.


----------



## obermd (Mar 3, 2012)

NickD said:


> Ha, besides not being able to pay a hundred bucks extra for a spare tire with the Eco with a manual transmission, three gallons less was even more motivation to look into the 1 or 2LT.
> 
> Like getting on the interstate with a full tank of gas and for the first 120 miles or so, see no difference in fuel economy for that first 120 miles, then the rest, gee I have an Eco now with 18 pounds less of gas! How come my fuel economy is not increasing?
> 
> ...


Marketing and the EPA formula for figuring out city MPG. Even without trickle filling my car can still go further than my bladder.


----------



## NickD (Dec 10, 2011)

obermd said:


> Marketing and the EPA formula for figuring out city MPG. Even without trickle filling my car can still go further than my bladder.


Ha, nothing in, nothing out, problem solved. 

Before the days of bucket seats and safety belts, could move around to keep that blood circulating, more for the history books. Now have to stop every couple of hours and walk around a bit to do the same thing. Or those lower limbs will go dead, then eventually the brain. 

Electrically heated seats help a little, but maybe need vibrating seats as well. New problems, new solutions.


----------



## obermd (Mar 3, 2012)

Nick, you do realize that today's solutions become tomorrow's problems. It's how engineers stay employed.


----------



## NickD (Dec 10, 2011)

obermd said:


> Nick, you do realize that today's solutions become tomorrow's problems. It's how engineers stay employed.



Ha, don't we wish, engineers have to do what the government, marketing, and the bean counters tell us what we have to do. And either you do it or they will find someone else that will.


----------

