Fuel cell question

#1

I don’t think many people (if any) have gone this route since search didn’t bring up a load of answers.

This question is mostly hypothetical now, but would like to be prepared depending on the direction I decide to go.

Have been chasing a fuel starvation problem since day 1 with this car. It is a 90 325is so not the typical older tank / transfer pump issues.

Pump starts to buzz after running hard on the track (typically 20+ min.) then will start to cut out in hard cornering. Once it starts to cut out, it won’t really rev past 4-5k. Cool down or fresh gas will help, but once it starts car has to sit for a week + before it completely goes away and ‘resets’ so to speak.

Replaced (with new or known good):
FPR
ECU
Relays (both)
Fuel Tank Breather valve
Fuel Pump
Fuel Filter

Through trial and error (obviously) I now think it may be a dent in the tank that is making difficult for the pump to draw. First trick is to try and beat the dent out.

But I’m tired of chasing this and have considered going the fuel cell route. Now to the point of this rambling post. (Since I know everyone will say just swap out the tanks. I’m very lazy and this only appears on the track so it isn’t something that can be tested without the risk of losing track time, I’m trying -desperately- to fix this once and for all and move on to other annoying stuff)

I see where the fuel tank can be removed, does this apply to the hard lines and anything else that isn’t needed with the installation of new fuel lines and a cell, or is it truly just the gas tank. No problem either way, as always want to be sure before stuff gets cut / destroyed / thrown out.

#2

If it was just the dent in the tank would not just adding fuel do the reset? New tanks can be had. Fuel starvation is not a new issue with the E30. I would look to make sure that the return lines to the tank are not clogged. Maybe when it gets some air from the lack of fuel for the dent the air can not leave the system through the return line.

I have a whole mailbox dedicated to E30’s and a lot of the stuff is about starvation.

You may also want to check that the tube from one side to the other is not damaged or clogged. In you car it goes over the drive shaft and has to suck fuel from the other side.

Good Luck.

Michael O.

#3

Well I took the screen off the bottom for my last ‘test’ of the year, hoping to give it some more room to pickup. It still ended up cutting out but seemed to take a bit longer than normal. That is when I really started looking at the tank. There is a dent in the approximate location of the fuel pump pickup. That is why I’m leaning towards the dent as at least part of the cause.

A ‘new’ tank is I think in the $400 - $500 range, a used tank can bring its own host of issues to the party. Hence my consideration of the fuel cell.

I recently heard about the tubes between the saddles. My understanding is that there is no way to clean those out or check for clogging?

#4

Here is a copy of a post from the CR list about fuel tanks and where to get them. If you remove the pump in your tank you should be able to use a broom handle or something to just push the dent out. Especially if it is right where the fuel pump goes. I did this on my E24. Just look at the tube and see if it is crushed. May have to remove the tank. If the tank is removed you may be able to look or reach into the hole for the pump or sender and place a piece of tubing on the cross over and blow some air into it.

Michael O.

Below is the post:

==========================

The tanks in the earlier cars like my 87 325IS are smaller. My 1988 325IS
KP has the larger tank. THe after market guys stock both. Here is one
place that has them for cheap.

NB Gas tanks
Calais Maine
gastanks@nbnet.nb.ca
800-561-8265

They charge $129 delivered for the 14.5 gal (1987 and older 6 cylinder E30
PN#BM1A) and the same for the 16.6 gal.tank from the 1988 and newer 6 cyl
cars (part#BM1B). He tells me he gets them from Canada.

N B Gas Tanks
Old Ridge,
St. Stephen, New Brunswick,
Canada
E3L 2Y2

gastanks@nbnet.nb.ca
Tel: 506-466-5249
Tel: 800-561-8265

#5

Sweet. The rear subframe is on the ground now, so phase 2 after RTABs / Subframe bushing and clutch is the fuel tank. I had planned to beat the dent out, etc. Good info.

I can’t envision the tube thing yet, I’ll have to get it out to take a look.

Thanks.

#6

The tube is an upside down V that goes from one side to the other. It equilizes the fuel on both sides. As the fuel pump uses fuel, the lowering level of the fuel sucks fuel from the other side.

That is as good as I can do.

Michael O.

#7

I haven’t experienced the fuel starve problem, but I run with a full tank. I had to drop my tank due to my cage builder burning through the 3 return hoses to the vent/expan tank next to the fuel filler neck. They are routed through the body in a conduit. Two are plastic and the other is a cloth covered rubber fuel hose. It was a pia to drop my tank since I had a full tank just before discovering the fuel leak. After seeing what physical layout and inspecting the hoses, it’s gives a better idea of how the fuel supply could malfunction. My suggestion is since you already have the subframe off take the tank off, replace all the fuel lines. You need some 6 mm and 8mm fuel line hose, a $16 hose from the tank to vent tank and two plastic tube lines from the tank to filler neck. I just bought all that for less than $40. Also the rubber hose from the filler neck to tank was dry rotted thats about $15. You can’t see any problem hoses/lines without taking it all out.

I would first replace all that old crap with new and test for fuel starvation before buying a fuel cell. My car is a 89.
I’ve got pictures of my build at http://s13.photobucket.com/albums/a280/bmwbadboy/

#8

The PO said he cleaned the tank and replaced the hoses and filter when I bought it. He had purchased it from someone on the cheap since it wouldn’t run at all and a shop had told him it was a "problem with the engine". This guy determined it was fuel related, did the above and shazam it started and ran fine.

So far everthing this guy said he did, that I’ve followed up on has turned out to be true. Even still knowing now that I can get a new tank for $150ish or whatever worst case, puts the fuel cell out of the picture. I was thinking from looking at Real OEM that it was going to be roughly the same cost as a fuel cell since they list it I think around $350.

The real PIA on this is not being able to test it except at the track. It is very frustrating to make serveral changes and "think" you’ve fixed it only to be wrong. Anyway thanks for the advice, any more info is appreciated. (Also should mention that I was filling up literally between sessions, so this is happening even when the car is totally full).

#9

I wonder if this could be a failure of the fuel tank vent system? If the vent isn’t working properly the pump will have to struggle against the vacuum crated by use of fuel.

#10

That was the consensus opinion. Checked the charcoal canister and replaced the fuel tank breather valve. no dice unfortunately.

#11

I once had a Honda with a similar problem that turned out to be an improperly re-installed hose. On those there’s a short hose between the fuel pump and the tank. At some point the hose and pump were replaced, but the new hose was a smidge too long and was almost kinked. Under conditions of high fuel flow the suction would fully kink the hose and cause it to collapse. Once this happened the hose tended not to return to a more usable shape until the car sat for a while. Once I found the cause of fuel starvation the fix was easy. Just snipped a bit off the hose to remove the kink.

Not saying the same thing is happening here, but a bad hose can cause problems that may not be readily apparent. The obvious check for a vacuum problem would be to run a hose from the tank up high enough to avoid fuel spillage and run a free vent to see if that helps.

The behavior of your problem doesn’t seem to me to match up well with a choked intake to the pump. In particular if the pump’s intake were badly choked you’d think there should be starvation problems all the time. Or if the pump was working so hard that it overheated from intake starvation it should recover as soon as it cooled down or the tank was filled. It shouldn’t take several days for "things to reset".

#12

found this diagram which accurately shows a layout of the expansion side and tubes for my 89. The fuel filter side is not accurate. I have counted at least 10 rubber hoses or plastic tubing. This may be worthless info. At least I know where to put all those hoses back on

#13

bmwbadboy wrote:

nice…where did you find the diagram at?
Igor

#14

Got it off the CD man, that Shark found http://ee1394.com/bmw/docs/factory/repair/index1.htm

#15

I didn’t find it, leggwork did.

I just posted the PDF of the entire site…

Details & downloads here: http://spece30.com/component/option,com_mamboboard/Itemid,68/func,view/id,7370/catid,15/

#16

Give credit to leggwork

#17

Simply for posterity’s sake I’ve revived this thread. Quick update. Installed the new gas tank, all the lines in the back and put a new fuel filter on. The tank and the filter looked like someone tried to gas up with mud.

Problem solved - right? That is what I figured… Fast forward to this weekend at RA. Nope. Still there.

On Sat. wanting to hang myself out of pure frustration car was grounded since the fuel would "surge" on making it pretty unsettling in corners.

Checked and tried various things Sat. and Sun. running a lap or two and coming in, wash, rinse, repeat.

Finally last session on Sunday in a fit of whimsy I unplug the O2 sensor. Voila. Runs fine.

Now - the new question what does this have to do with the price of tea in China. It would only lean out in hard right hand corners.

BTW also finally met Laura Patton and her crew chief Robert.