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Fuel Pump Woes


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Hello Bimmerheads,


I've been fiddling around with these cars over 3 decades. So, I've come across a lot of odd things, but I've never come across this one.


I'm running a stock spec early style 2002 engine with the 121 head and single barrel Solex. The single barrel Solex carbs can easily flood and bog if an incorrect fuel pump is used. For example, if you mate a 2002 mechanical fuel pump to a 1600cc motor with a single barrel Solex, you will easily overwhelm the carb.


But, what if you take the 2nd generation mechanical fuel pump as used on the 2002s with the 2 barrel carb and mount it on an early style 2002 engine and carb combo such as in my case ?


It seems to work well while you are moving, but the carb might be getting a bit overloaded. When I shut off my engine and wait  5 minutes, I have a hard time restarting. I have to depress the accelerator pedal to the metal and hold the butterfly wide open to start after 5 to 10 full cranks. But, when starting cold, the engine fires up immediately. It seems the carb is flooding after shut off.


So I tried to hunt down an early style 2002 mechanical pump with the lever style actuator. I found one, disassembled  and cleaned it, but I need to get a new diaphragm. I ordered a VW fuel pump rebuild kit which contains the same diaphragm as the 1600 and early 2002 pumps. But it has yet to arrive. In the meantime, I had credit with a parts vendor who provided me with an Italian made pump which mimics the early style 2002 pump with lever actuator. It is made by BCD. Well, I mounted this pump to my engine with the correct length rod and gave it a try. It seemed to improve the warm start issue, but the pump only works for a couple of days and then just quits. When I  prime the pump with fuel and refill the carb fuel bowl the pump will usually come back to life, but within a couple of days it quits again


I have all new fuel lines and I've inspected the sending unit. The fuel filter is new as well. I also disassembled the Italian pump and the diaphragm is new and looks good.


When I remount the other later style 2002 pump, no problems expect with the warm starts. I've also noticed that the later style 2002 pump hold a lot of pressure in the line between the pump and the carbs after shut down. This is not the case with the Italian pump which may explain why my engine is flooding with the newer 2002 style pump.


Has anybody had any issues with the Italian pumps ?

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You got my curiosity aroused. According to Mr. Haynes, 1600 pump is 4.12 lb/in2; 2000 is 4.27 lb/in2. Another old French manual says 0.21 to 0.25 bar for all models. That hardly seems a significant difference between pumps. Unless the rods have some effect.


 As to your symptoms, I would have thought fuel boiling off in the bowl or fuel filter, or the pump losing prime. I have trouble understanding  how the pressure at rest would be high enough to overpower the float, but at say 4000 rpm it wouldn't. Maybe I need more coffee.

As to why the emplacement pump poops out, I'd check its innards/filters if it was used, but otherwise that makes no sense. I use an electric pump with a regulator.

Maybe someone familiar with old Solex can help. I seem to recall some idiosyncrasies discussed on FAQ>

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I have both a 69 and 73, the former with its original 1 bbl Solex, the latter with a Weber 2 bbl.  I have used both early and late style pumps on the '69 with absolutely no problems at all.  In fact, I've never had a hot start problem with the 1 bbl Solex, but have with the Weber.  


According to the factory parts book, all 1 bbl Solex engines (1600.1800/2002) use the same part number fuel pump.


Does your 1 bbl Solex sit on a bakelite heat shield to insulate the carb from the manifold?  IIRC that's the way they came from the factory.  Also, are you making sure the fuel line that runs from the firewall to the pump isn't touching either the manifold or the cylinder head--and if you have an in-line fuel filter, is it standing clear of surrounding metal.  All the above can cause fuel boiling once a hot engine is stopped.  You might also check the float level in the carb to see if it's up to snuff--too high and the hot gas in the float chamber will spill over into the carb throat as it expands whlle sitting in a stopped, hot engine, causing flooding.  


As for the Italian fuel pumps--I used one for many years on my '69 and it worked fine until it quit!  Cause of quitting was the pad that the pushrod presses against was soft steel, and the hardened pushrod wore a hole in it!  I dismantled the pump, mig welded up the pad and then ground it down smooth, reassembled and it worked fine once again.  Also, if the pushrod itself is worn at an angle on the fuel pump end, it won't be long enough to operate the Italian pump.  Both pushrod ends should be at  a 90 degree angle to the rod's length.


Let us know what you discover.



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The factory specifies one fuel pump for the 1600 and 1800 while a diffrent fuel pump is specified for the 1800ti, 2000, 2002 qnd 2002ti. I believe the 1600ti is also a part of this latter group. I tried using the 2002 fuel pump on my other 1600 equipped with the original 1600cc motor and the single barrel Solex, and it just bogged and stumbled. It was way too much fuel.


As far as the Bakelite spacer under the carb, it is there. I never leave it out.


The Italian fuel pump is a mystery. It is new and the actuating lever is not worn. The rod is also in very good shape. I have plent of them, and I picked the best one with no wear. I have no clue as to why it gives out after a day or two of operation. I've narrowed the problem to the bottom half of the fuel pump which houses the diaphragm. I've used a factory stock 2002 top half withthe Italian bottom, and it yielded the same results. Maybe the rubber diapragm rocks itself off center and looses its ability to pump adequate ampints of fuel. I will try preloading it during assembly as suggested by the VW rebuilders. What can I say, it was built by Italians. I've owned a couple of Fiats including the twin cam Fiat 124 Spider. I don't like motors with timing belts. Otherwise it was a decent car. Italian cars from that era have an erratic interior layout. They pay no attention to ergonomics. Even the Alfas are affected. A different mindset was involved in designing those machines.


The fuel hose does not rest on the manifold, but it is near the manifold. The original 2002 inlet on the fuel pump is canted upwards at bout 30-45 degree angle which helps keep the fuel line away from the manifold, but the later fuel pumps that came with the 2 barrel carbs don't have this feature.


I've read that difficult warm start issues may arise from a weak coil. When a faulty coil gets warm, it puts out less juice. I use the Bosch Blue Coil. It has an internal resistor, but it is rated less than the stock 2002 coil. I can use a stock 2002 coil, but my chassis is a 67 with a 2002 motor installed and lacks the external resistor which should be used with the stronger coil. While the blue coil is an upgrade for the 1600, it is a downgrade for the 2002. I will try the stock 2002 coil and install the necessary external resistor. Perhaps this is the problem.


I've tried usiing another Float needle valve which did not change anything.


The Devil is somewhere in the details.



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Did you check float level? Even though the pumps are different, it would appear the pressures are not all that different. Plus 2002s came  with I bbl Solex too.


I would think the cold starts would be harder than warm starts, if you had an ignition problem. Blue coil should be fine - I have one. But no harm in reviewing ignition system.

The heat source to avoid is the head, not the manifold. Where is the fuel filter?


Perhaps get it hot, let it sit, then pull top of carb to see what's going on in the bowl. Then stick feed hose to carb in jar and turn over motor to see if fuel is delivered.

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1 barrel Solex on 1600 is not exactly the same as the 1 barrel Solex on 2002. They have different size internal fuel passages, different size jets, different size venturi, different size main butterfly. The 1600cc has less demand for fuel. Installing a 2002 pump on a 1600 leads to flooding, running rich, overloading the carb with fuel, bogging etc. The 1600 and the 2002 use a different fuel pump. If the factory could have gotten away with using the same pump on oith, they would have done so because they would have saved money. Nevermind what most parts vendors tell you. They lump everything into the 2002 category including the 1600 which in many respects is a very different car despite the obvious similarities to the 2002.


One of my 1600s is equipped with an early spec 2002 motor, 5 speed OD tranny from a 320i and a long neck limited slip diff diff in a 4.11 / 1 ratio. This is the car with which I'm having the hard starting issues when it is warm or hot. There are absolutaly no cold start issues. The car starts on the first crank at 6:00AM in the morning. But, after driving it and parking for a little while, it has a very difficult time restarting. I need to depress the throttle wide open before it finally starts. My battery is in the process of going South as a result of all the hard starting. My timing is spot -on because I'm very meticulous about that. I replace the points once / month.


I will temporarily install a fuel shut-off valve between my carb and the fuel pump where I will shutt the fuel off after I park, like on a motorcycle. In this way I will ascertain whether this problem is related to excessive fuel pressure making its way past the float needle seat.


I've also inspected the plastic fuel line which lloks good, but I will take a second look. I think that the 1600 fuel line is about 1mm smaller in diameter compared to that of the 2002. While most of the mechanical pumps on the 02 series run at about the same pressure, they deliver different amounts of fuel. The difference might seem negligible, but even a small difference will affect the way in which your carb works. It is enough to either starve or flood the carb.


Everytime, I look for a part for my other 1600cc car, there are vendors and people who always say "Why don't you just use the 2002 part".





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