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I've a very frustrating problem that I cannot quite figure out. I have a 1974 2002, 4 spd, with the Weber 32/36 on it. The car hasn't given me any trouble in the months that I've owned it. And then...

 

On my way to work last week, the car just died going down the highway. At first I thought it was electrical, though by the time I'd gotten off of the highway, it was running again. I wiggled some wires, it continued to run so I got in and drove off, but after a couple of miles it died again. Long story short, I finally figured out it was a fuel issue. At one point I removed the inline fuel filter, blew through it (delicious!), re-installed it and was on my merry way. For another couple of miles. It died again, leaving me on the side of the road once more. I was finally able to get it to a gas station, and thinking maybe my gas gauge was wrong I filled the tank. That wasn't it as I was only able to get about 5gal in the tank. Nevertheless, the car started up and I drove away. Only to have it die at the stop light. With traffic behind me. I pushed it to the side of the road and noted that there was no gas in the inline filter. OBVIOUSLY, it's the fuel pump.

 

I waited a few days for the pump to show up and I replaced it with no problems. After priming the carb, the car started right up. I test drove it for nearly 60 miles with no issues, until I got to the busiest part of Kansas City on I-70 and it quit. I had to do some pushing and got it off of the highwway, coasted down a side street and pulled into a lot. It would crank, but not fire.

 

After some thought, I decided to disconnect the fuel line off of the carb and see if it was getting gas, and it was not. So, even though I could still blow through the fuel filter I thought maybe something was going on with it so I cut the windshield washer line off and spliced it into where the filter was. At the same time, I remembered that there was a filter in the Weber, so I removed it as well. The car started and I took it home without an issue.

 

The next day I went to that part store and bought a see-thru inline filter with a removable element. I installed this on the car, and took it for another test drive. I drove it nearly another 50 miles, without issue, and made it back home.

 

Thinking I had the problem fixed, I drove it to work this morning. Guess what. 10 mins after I left home, on the side of I-35, in morning rush hour, and RAIN, it quit. Ran out of gas again. I was eventually able to get back to within a mile from home, but that was it. After work tonight I went to work on it. It started, and ran for about 2 blocks and died, of course, on a steep hill. Coasting back down, I parked it in a lot. I returned later and replaced the fuel filter with that same piece of hose, and disconnected the fuel line at the carb. After cranking a bit, there was fuel spurting out. I reconnected the line and it was running again. I let it run for about 5 mins, hopped in and began driving home, only to have it die once I got it on the road. I coasted back into another parking lot and there it sits. WHAT THE HELL?

 

A local mechanic says it's fine particle rust in the tank, but I don't know why all of a sudden I would have trouble with rust. It's never been an issue before and I've not seen any discoloration in the fuel filter. I'd sure appreciate some help here. I bought an older BMW because they are so simple and basic, but this little red head isn't playing fair.

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Things to check:

1.  Pull up your trunk floor and carefully examine the little piece of hose that connects the fuel pickup/gauge sender with the plastic fuel line that runs forward to the engine.  If this hose has a woven cloth cover, remove, discard (throw it CD's neighbor's pool) and replace with a new piece of US style rubber fuel line, held in place with a couple of hose clamps.  That cloth-covered hose is OEM BMW (probably original to your car), can crack (and you won't notice the cracks as they're hidden by the cloth covering) and will suck air.  Mechanical pumps don't function when they suck even a little air.  While you're at it, check the remaining flexible fuel lines in the engine compartment (plastic line to filter, filter to pump, pump to carb) and replace any old cloth-covered hose you find.   If that doesn't help, or all the hoses have been replaced...

2.  Remove the fuel pickup/gauge sender from the tank. (check archives on how to).  With a nearly full tank, remove slowly to allow the gas inside to drain into the tank or you'll have gas all over the trunk's inside and it'll smell for months.  Once it's out, check the filter screen at the bottom for crud and plugging.  It can be removed and cleaned.  Then shine a light down into the tank to see if there's crud in the bottom of the tank.  If that's the case, you'll need to drain the tank and clean it out.  When you drain, be sure and ground the car to the drain container to prevent static electricity buildup.  Sparks and gas don't mix outside engines!

 

Let us know whatcha find...

mike

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Thank you to all of you who replied with your suggestions. I'd say that you were all right on, though I will not yet qualify this as total success. However, the car is back home, so it's not total failure either.

 

Suspecting that there may be some material in the gas tank other than rust, I started there. I was surprised to find that there was no screen or filter on the pickup, and that kind of disappointed me. But after looking it over, I decided to look in the tank (which was, by coincidence, nearly full). I saw a glob of red silicone in there and a little foil seal off of the top of a bottle of Heet, or something similar. I expected the red silicone because the rubber elbow that comes from the gas cap to the tank was cracking at one point at someone tried to fix it using red silicone. Regardless, i was able to take a long screw driver and move the glob directly beneath the hole in the top of the tank, but was not able to pull it out.

 

I drove down to the nearest parts store and bought one of those T-handled "magic claw" things for grabbing dropped bolts, nuts, etc. It worked perfectly and I was able to remove everything that I could see in the tank. I was fairly confident that this was being sucked over to the pick-up and this would solve my problem.

 

Started the car, and it ran. I revved it up a few times, let it idle a bit and thought I'd try to make it home. Again, it ran until I got it on the road, where it promptly died. Luckily this was on a hill and I was able to coast/push it back where I began. I removed the fuel line and cranked the engine over, which ironically STARTED while fuel was being pumped into a small bottle. (Grrrr. It's just making fun of me now. I'm not sure but I think I heard a little laugh coming from the engine compartment.) I used the little bit of gas in that bottle to prime the carb, though there was not much. I then disconnected the coil (take that!) and cranked a bit more to see how much fuel I would get in the bottle. Not as much as I'd have thought. So I reconnected the coil and primed the carb. It ran for a bit and when it tried to die, I'd splash a little more in just to keep it running. After a bit, it continued to run. 

 

At this point, I noticed in one of the clear fuel lines in the engine compartment that there were a lot of air bubbles. Hmmm, I thought to myself. That didn't seem right. I checked a few hose clamps to make sure they are tight, and one was a bit loose. Then I went to the trunk because I had noticed that one of the hoses did indeed have the cloth cover on it. However, the other end of it disappeared somewhere behind the back seat, so I didn't pull it off. (I will do so this weekend now that it's home.) I watched as the fuel was moving through the lines and there were lots of air bubbles. Again, I thought this unusual so again I checked clamps. I turned the car off, trimmed the two hoses in the truck back about an inch and reconnected them both. I restarted the car (!) and there were still air bubbles moving through the line, but the car was still idling. I watched a bit longer and the bubbles seemed to nearly disappear, though there were still a few.

 

Back in the engine compartment, most of the bubbles were gone. Thinking this was a good time to make another attempt to get the LRC (Little Red Car) home, and hopped in and it now sits in my driveway. By most counts, this would be a success, but after betraying my trust so often over the last week, my trust cannot be earned so easily.

 

I think I've established that a line is sucking air somewhere so I am going to replace as many pieces of fuel line as I can this weekend. While the sender/pickup was out of the tank, I noted that there were some small rust spots here and there, but overall it wasn't too bad. I'll make sure that the new fuel filter is cleaned and re-installed, and then I will let it idle for about 30 mins after which I will drive around my block for the next 2 hours to confirm that it is fixed. (Never again will you quit me out on the road, damn you!) That being said, I am cautiously optimistic that I know the problem, I just need to find the location of the problem which I don't think will be too terrible. I am tempted to run all new lines throughout the car thinking that it may also help remove the gasoline/female-repellant smell from the car. 

 

Once again, thanks to all who offered their help and suggestions. Thinking of switching to a 38/38 DGES sometime soon so might need some help again.

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When you replace fuel lines, do not replace the white/milky rigid plastic line that runs from the gas tank to the firewall.  Unless, of course it's broken.  That is a special plastic that will collapse and seal itself if there's a fire nearby.  Since it runs through the passenger compartment, you want this feature in case there ever is a fire.  And it does work--I found out by actual experience.  Replace the short rubber lines, but not the plastic one. 

 

cheers

mike

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So I removed the back seat and followed the fuel line and did not see any leaks or cracks in the plastic line. Then I started to think about the other line coming from the tank but can't figure out what it does. I would think maybe it's a return line of some kind, but on this particular car, there is no place for the fuel to return, so I'm not sure about that.

 

Regardless, I replaced or trimmed back and rubber fuel line, reinstalled the new see through, cleanable fuel filter and started the car. I revved it up a few times, then after it was warm, I held it at about 3000rpm for a minute. No issues. So I let it idle for about 30mins, with no issues. Again, 3000 for a minute. No issues. I shut if off, it started right back up.

 

So I decided to venture out in the neighborhood. I drove around the block a few times, then around two blocks, and so on until it seemed as if it would be okay. Finally, I took it on about a 5 mile loop and it ran fine. I ran the engine up to 4000rpm a few times with no fuel starvation.

 

On the way home I decided I would attempt the big steep hill with a little S-curve in it, followed by another steep but short hill. It pulled very strong all the way up the long hill, thru the s-curves and then....yep. Starved. Due to my speed, I was able to get up the hill and over to the side of the road. I cranked it a few times and it would start, then sputter and die. I have found that for some reason, if I leave it in first (or any gear I presume) and crank with the clutch out, (which is hard on the starter, I know) the car seems more likely to start. Such was the case as it started and I drove it the last 3 blocks, up a hill, up my driveway (hill) and there it sits.

 

So...where should I be looking now? I don't think that its' just a hill that is causing the problem because this has happened several times on flat ground too. Two questions: what is that other hose coming from the tank? Is it possible that the clear plastic hose is leaking somewhere under the car (though I've never seen proof of it on the pavement) and letting air in?

 

Thanks for any suggestions.

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here's my story on topic.  My 1948 Chevy truck had this exact problem.  I discovered that the pickup tube inside the gas tank had 6 tons of crap wedged into it.  Overnight, sufficient amounts of gasoline would percolate through the crap, up to the gas level in the tank.  Upon starting, the engine ran fine.  But quickly enough the pump couldn't pull gasoline through the crap:  fuel starvation.


     I discovered the problem by forcing compressed air into the fuel line, in the direction of the gas tank.  Very little air actually went through the line, ergo, massive blockage in the fuel tank pickup tube.


     My solution:  I punched a hole in the side of the gas tank and installed a fuel pickup tube of my own design and manufacture, with a screen on it.  Problem solved.


 


Another fuel starvation problem with the same truck:  a pinhole leak in the rubber diaphragm of the mechanical fuel pump.  Fortunately I could buy a rebuild kit for those old pumps.


 


Cheers,


 


Carl


Edited by OriginalOwner
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There's another suspect, not mentioned yet, or at least I didn't see it in my speed read of the suggestions.  I had a '75 long ago that stalled after I'd been working on it, and just after filling the tank and heading up the ridge where I live.

 

I believe the problem was that I'd plugged the vent line the was supposed to/used to got to the charcoal canister.  Thus, there was no tank venting and as gas was burned, the tank drew a vacuum too great for the fuel pump to overcome.  This was especially the case with a full tank without air space in it.  If the tank had been nearly empty I might have gotten away with the setup, until the next fillup.  Apparently my gas cap was "ohne luftung" which means something like "without venting".  If I'd had a leaky cap, or other air leak into the tank, I'd have been okay. 

 

I suggest this because after I addressed it, no problems.  I never found a "smoking gun" to absotively posilutely confirm the vacuum tank, but the problem stalled me three times in rapid succession.  I could only get 20 yards before the motor coughed and died again.

 

Best of luck in your search for a resolution.

Edited by Honolulu
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  • 7 months later...

I finally found the problem with the fuel starvation that started 7 months ago. I ended up replacing the fuel lines, the fuel filter, the fuel pump, eventually installing an electric, removing and tearing into the carb, pulling out the pick-up tube; in short, everything that I could think of. At one point, I asked a well-connected racing friend about it and he thought that maybe it was the coil since nothing else worked. So, since it was a cheap fix, I tried that...to no avail. The car still continued to idle just fine, but when any kind of rpm was attempted, it would starve.

 

So I decide it HAD to be the pickup in the tank. I took it out (again), took a look at it, and decided to tear into it. Everything looked good. But when I tried to blow through it, it was evident that there was some blockage. After trying to dislodge whatever was in there a few times, I finally pushed a piece of wire through it and blew in it again. Out popped...a fly. A FLY! It was stuck in that 90 bend of tubing at the top of the pickup tube. (Perfectly preserved in the gasoline, by the way.) So, after "de-bugging" my fuel line, the car once again runs great. A fly caused me all of this trouble, all of this time.

 

So now I'm wondering if the electric pump was even necessary and thinking I could go back to the mechanical. However, I'm a bit scared of messing with it now that it's running. So, I'll probably leave it alone. Nevertheless, I had to share the simplicity of the problem with you all.

 

On the road again!

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  • 4 years later...

Just in case anybody wonders whether 'closing the loop' is helpful....I have a '76 with DCOE's and a mechanical pump. It was exhibiting some, but not all the behavior described by darrinos. But, after checking the pump, and after reading the 'fly in the pickup' post, I decided I had better have a look at my pickup. I found a nasty hunk of silicone sucked up about 1" into the pickup, with about 1/2" sticking out (enough to grab, fortunately). Oh - I also found the two round objects in the bottom of an otherwise clean tank. See photo.

IMG_5398.jpg

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