what's with CRD fuel tank?

naturist · **Posted:** Wed Apr 19, 2006 3:12 pm

For those following the saga, today I got the CRD back from the Dodge dealer who took my Jeep in to complete the job the Jeep dealer dumped in the middle of the job.

I drove it 10 miles home, installed the Provent, and drove it another 10 miles to fill up the fuel tank, then another 45 miles to check it's operation. It seems normal again, no check engine light or anything.

I did encounter one wacko thing, maybe somebody can explain. When I got home, I hooked a Mityvac up to the fuel line at the fuel filter to drain the tank, since I wanted to be absolutely certain there was no crud in there. I managed to get about 11 gallons before sucking the tank dry, about what I expected. I will run that through a 1 micron filter and run it through the TDI.

Dumped 5 gallons of fresh fuel in from a can I had picked up for the purpose, primed the pump, and drove those 10 miles to the gas station, where I proceeded to need only 10.8 gallons for a fill up. Expecting to need more than that, I took the trouble of making sure; yup, there was no way to cram any more in. On restart, guage is pinned full.

Sooooo, if I do the math, I figure there is at most a tad over 15 gallons in there above what could be gotten out with the fuel line to the engine. What was really wierd, though, was all the way to the gas station the guage registered 2/3 full.

So what's going on here, any ideas? Is it possible for the fuel pickup to float? Fall off in the tank???

And what's with 5 gallons being 2/3 or 15 gallons -- or more precisely, 2/3 of the supposed 20 gallons the tank is SUPPOSED to hold?

wenied · **Joined:** Wed Dec 21, 2005 4:01 pm **Posts:** 107

I dont know man, Last tank i filled i put 19.25 gallons. (ran her a little too low.)

RFCRD · **Posted:** Wed Apr 19, 2006 9:45 pm

I hope you didn't give up on burning the good stuff. I got some strange returns for the gauge when I fueled once with it running. Went away after it was parked overnight.

One mod I would like to do to mine is installing a drain in the fuel tank. That's the easiest way to keep water from accumulating and to get rid of a tank of crud.

Goglio704 · **Posted:** Wed Apr 19, 2006 9:51 pm

The fuel gauge does not seem to update continuously. I have fueled mine with the engine running and been miles down the road before the gauge came anywhere close to full. I suspect the gauge is actually run by the ECM and that it only looks at it periodically and will only allow a certain rate of change when it does look at it.

pnorton · **Posted:** Thu Apr 20, 2006 2:45 pm

I filled up yesterday. Left it on but not running. Filled it up with about 18 gal. Got in started it and it read half. I turned it off and restarted it. Same thing, gauge read at half. I drove home and turned it off. Went aout a couple hours later and it was back to normal.

Peter

oldnavy · **Posted:** Thu Apr 20, 2006 3:17 pm

Yes the guage is a wacky do thing. I have shut engine off a filled and the gages come right up to full, but if I leave engine running and fill it takes a few miles down the road before it comes up to full. I can park in the garage and fill from 5 gal cans with engine off and after I finish and put the cap back on it will come right up to correct reading.

I think this is due to the monitoring of the fuel system by computer and the fuel cap/door off/open light monitor.

FarmDiesel · **Joined:** Thu Sep 15, 2005 8:49 am **Posts:** 132

I've put 21.11 gallons in mine...and the low fuel light wasn't on yet...

retmil46 · **Posted:** Fri Apr 21, 2006 12:13 am

I think sometimes that DC just likes screwing with our minds with wacky fuel gauges. On the '04 Dakota I had, it supposedly had a 22 gallon tank. First time I ran it down to the low fuel light, which came on consistently at 1/8 tank, it only took 16 gallons to fill it. WTF, a 6 gallon reserve? Did that on every fillup. If the MPG had been as consistent, I might have kept the beast.

retmil46 · **Posted:** Fri Apr 21, 2006 12:15 am

FarmDiesel wrote:

I've put 21.11 gallons in mine...and the low fuel light wasn't on yet...

What did you do, pull the old Junior Johnson routine and wrap 50 feet of garden hose under the Jeep as fuel line? :shock:

naturist · **Posted:** Fri Apr 21, 2006 8:08 am

Well, there is no doubt that the fuel guage is wacky. But what REALLY worries me is that the fuel line to the engine sucked air bigtime, and then I could only fit 15 gallons in. I'm about to run a little test: put a 5 gallon can full of fuel in the back and ride around until either the thing dies for lack of fuel or the low fuel warning light comes on (AND I'm sure I've used at least 15 gallons!).

But that does leave me wondering: even if it proves out that I can drive down to the bottom of the tank, why on earth was I only able to suck out 15 gallons? Do you suppose tapping the remaining 5+ gallons somehow requires the active cooperation of the ECU? Now isn't THAT a scary thought?

oldnavy · **Posted:** Fri Apr 21, 2006 9:07 am

naturist wrote:

Well, there is no doubt that the fuel guage is wacky. But what REALLY worries me is that the fuel line to the engine sucked air bigtime, and then I could only fit 15 gallons in. I'm about to run a little test: put a 5 gallon can full of fuel in the back and ride around until either the thing dies for lack of fuel or the low fuel warning light comes on (AND I'm sure I've used at least 15 gallons!).

But that does leave me wondering: even if it proves out that I can drive down to the bottom of the tank, why on earth was I only able to suck out 15 gallons? Do you suppose tapping the remaining 5+ gallons somehow requires the active cooperation of the ECU? Now isn't THAT a scary thought?

Any posibility you did an incorrect measure? Hey no one is perfect.

You should see the saddle tanks the LX cars have. You can't fill them up completely unless you have used at least 5 or 6 gallons. They have two fuel pumps and it has a plastic tank with baffles. Man you should have seen the look on my face when I did a measured 75 miles and stop back at same pump to fill up and could only get 1.2 gallons in the tank. It seems I have to be down to about 2/3 of a tank to get a full fill due to the saddle tank workings.

naturist · **Posted:** Fri Apr 21, 2006 3:02 pm

no possible way I coulda mis-measured. I bought exactly 5.001 gallons of diesel, put it all into a single Blitz can, and then sucked the tank dry. MightyVac got nothing but air for 2 or 3 minutes. Dumped in the contents of the one can, and drove to the pump, where it said bold as brass 10.804 gallons after I got done nursing in as much as I could. You do the math, Big Guy. Not much room for error, is there?

Anyway, drove 225.1 miles on that tankful, just over half cruising up the highway at 60, and it took 9.523 gallons from the same pump at the same station. In my book, that sorta confirms the pump isn't running slow by 50%. 23.64 mpg is about right, isn't it? (well, ok, shoulda been 2,364 miles per gallon, if God was home and all was right with the world, but it ain't, ya know?)

Oh, yeah, when I filled up, gas guage read just over 3/4 tank left.

naturist · **Posted:** Fri Apr 21, 2006 3:05 pm

oh, and RFCRD, I'm not giving up on the bean, but I AM running a coupla tankfuls of dino-juice to check mileage very carefully after the repair, and to "establish a baseline," so to speak, since the vehicle has never been run on straight petro before. And yeah, it does have a more pronounced diesel growl.

oldnavy · **Posted:** Fri Apr 21, 2006 3:48 pm

Have you got a factory skid for fuel tank? The reason I ask is I know of a Jeep gasser that had a huge dent in it and it could not be filled completely. The owner brought it in complaining about only being able to put 10 to 15 gal on fill up and gas gage didn't work proper. The Cherokee only had about 10k to 12k on the odo so the tech dropped the tank skid to remove the tank and the tank had a huge dent in it, only thing we could figure was it was damaged at the factory and someone was being a smart stupid by installing it on the assembly line. New fuel tank arrive a few days later and install, that made all right in the world for the owner. Wonder if you could have same problem, or if they like they did on some early Cherokee stick the small 16 gal tank on when it was suppose to have the 21.5 gal tank.

naturist · **Posted:** Sun Apr 23, 2006 9:33 pm

no skid plate, and no reason to suspect a dented fuel tank, but I'll crawl under it and have a peek. You never know, do ya?

oldnavy · **Posted:** Sun Apr 23, 2006 10:16 pm

naturist wrote:

no skid plate, and no reason to suspect a dented fuel tank, but I'll crawl under it and have a peek. You never know, do ya?

Hey crazy things happen. If no dents then go to dealer and explain what you did and have them to check tank, it could have something inside. Like a plastic bubble from mfg process, or 50' of coiled of plugged garden hose. Who knows what, but if you have measured fuel proper something is wrong. You might want to measure the tank for size and check it against another CRD. Since these probably use same tank as gassers, they may have stuck the small tank used on the 4cyl model. That has happened before and will most likely happen again.

RFCRD · **Posted:** Sun Apr 23, 2006 11:11 pm

oldnavy wrote:

naturist wrote:

no skid plate, and no reason to suspect a dented fuel tank, but I'll crawl under it and have a peek. You never know, do ya?

Hey crazy things happen. If no dents then go to dealer and explain what you did and have them to check tank, it could have something inside. Like a plastic bubble from mfg process, or 50' of coiled of plugged garden hose. Who knows what, but if you have measured fuel proper something is wrong. You might want to measure the tank for size and check it against another CRD. Since these probably use same tank as gassers, they may have stuck the small tank used on the 4cyl model. That has happened before and will most likely happen again.

One of the mechanical questions I have about the CRD is if this is the same fuel tank, transfer pump, gauge float, etc... as the gasser. Be nice to know when one fails if common aftermarket replacements are available.

oldnavy · **Posted:** Sun Apr 23, 2006 11:17 pm

RFCRD wrote:

oldnavy wrote:

naturist wrote:

no skid plate, and no reason to suspect a dented fuel tank, but I'll crawl under it and have a peek. You never know, do ya?

Hey crazy things happen. If no dents then go to dealer and explain what you did and have them to check tank, it could have something inside. Like a plastic bubble from mfg process, or 50' of coiled of plugged garden hose. Who knows what, but if you have measured fuel proper something is wrong. You might want to measure the tank for size and check it against another CRD. Since these probably use same tank as gassers, they may have stuck the small tank used on the 4cyl model. That has happened before and will most likely happen again.

One of the mechanical questions I have about the CRD is if this is the same fuel tank, transfer pump, gauge float, etc... as the gasser. Be nice to know when one fails if common aftermarket replacements are available.

Most likely they just use the tank and that's all, sort of like VW did or has done for years. All the hardware for a diesel would be different, but heck they may have done something stupid like use a different tank just for CRD.

what's with CRD fuel tank?

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