Call me stupid, but my car ran great and for no particularly good reason I added a can of octane booster during the fill-up a few days ago. Now the car runs poorly and backfires a lot unless I keep my foot real steady, not too much gas, not too little. The motor is fed by Webers. I am assuming that the extra octane requires different timing. What can I do to get past this tank of gas?
Tom
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It so happens that my neighbor who owns a BMW repair shop probably has the answer to my problem. Even his wife noticed how rough my car ran, they can't help but hear me leave the house.
He does not believe that my sudden rough running has anything to do with the octane booster but that most likely I picked up water during the last fill-up. He said that since premium is not sold as much as regular, water condensation can build up in the gas station tanks once the temperature starts dropping. He is running back to the shop to get some dry gas that will break up the water molecules. I will post the precise name of this stuff once I get it and the results.
...Drain the Tank. Or, It can always be pumped out with a hose down the Filler, and a hand pump. Electric Pump??...watch the Sparks!!
The Engine runs a Mechanical Fuel Pump?? My First thought was, the Octane Booster was so Potent, it ate up the Fuel Pump Rubber Diaphragm. Starving the Webers of Fuel and causing a 'Lean' condition Backfire.
If You had said you were running a Holley (which you are Not)...I would have Guessed the Accelerator Pump Diaphragm, was damaged. Here in California, with 15% Alcohol, I have to run Speciallized Acc, Pump Diaphragms.
MJ
Marlinjack, from what I know Webers always use electric fuelpumps , Webers needs a higher and constant fuelpressure.
Simon
Hi Simon…
Not 100% of the time.
I’m certainly not a Weber expert on V-8 engines, but my TVR Vixen 2500 has triple DCOE 40s.
I am running a stock mechanical fuel pump, which feeds into pressure regulator. I have my regulator dialed down to about 2-3 psi feeding the Webers.
Apparently Webers are very sensitive to fuel pressure, but they like to have full flow, but only at pressures about 2-3 psi.
Rocky
Hi Chuck, you are right about the low , constant pressure , but my experience is that on (big) V8 engines a electric fuelpump is better .
starting is easier when the fuel bowls from Webers are full of gas.
Simon
Yep…. Definitely agree on the starting, and I know you have more experience with Webers & V8s than me!
Pull a spark plug and take a look at it
@simon posted:Marlinjack, from what I know Webers always use electric fuelpumps , Webers needs a higher and constant fuelpressure.
Simon
IDA Webers need only 3 to 5 psi fuel pressure. The electric fuel pump is used most often to prime the carbs when they are dry from sitting.
They run fine on just the mechanical pump. In fact, if you use the Holley mechanical fuel pump that puts out 7-8psi, you MUST use a pressure regulator to reduce the pressure to the carbs. Absolute max to them is 5 psi.
This is exactly how the original 289 Shelby Cobra factory race cars were set up but used the stock Ford Mechanical pump. That pump is rated at 3 to 5 psi.
Once the engine was started, the drivers turned off the electric fuel pump and ran the race on the mechanical pump.
It COULD be water in the fuel but it actually has symptoms of the roll pin failing and twisting on the distributor drive gear.
Why this is so prevalent on the Clevelands is beyond me but it does seem more then just coincidental that the distributors that have this issue often only after they were "rebuilt" and use a chrome molly oil pump drive shaft?
All due respect to your BMW guy but there are no "Clevelands" in BMW's that I know of. This is a unique problem to the Cleveland engine.
The popular wisdom on the 351C roll pin thing is twofold, the first is the stock roll pin is a spiral wrapped piece of thin sheet metal, instead of a real pin, and the second is that if the stock gear rotor pump hits small piece of debris it stops / slows for just an instant, placing a lot of load on both the pump drive shaft, and the roll pin.
Rocky
@rocky posted:The popular wisdom on the 351C roll pin thing is twofold, the first is the stock roll pin is a spiral wrapped piece of thin sheet metal, instead of a real pin, and the second is that if the stock gear rotor pump hits small piece of debris it stops / slows for just an instant, placing a lot of load on both the pump drive shaft, and the roll pin.
Rocky
OK, but this is the same with all Ford distributors. I have not seen this issue with other Ford distributors.
At my neighbor's advice I added a fuel system dryer, Isopropyl Alcohol, and the problem is solved, it runs great again. So, it was water in the tank.
On a second note, I used to run an electric fuel pump but changed to mechanical years ago. Beats me why, it was too long ago. If I let the car stand for more than two weeks it appears fuel starved and starts hard, so I pour a little gas in each Weber carb and it fires up immediately. An electric pump has been ordered and will be managed by the existing fuel pressure regulator.
@tomkuester posted:At my neighbor's advice I added a fuel system dryer, Isopropyl Alcohol, and the problem is solved, it runs great again. So, it was water in the tank.
On a second note, I used to run an electric fuel pump but changed to mechanical years ago. Beats me why, it was too long ago. If I let the car stand for more than two weeks it appears fuel starved and starts hard, so I pour a little gas in each Weber carb and it fires up immediately. An electric pump has been ordered and will be managed by the existing fuel pressure regulator.
The same "vent" holes in the top of the Webers that you have been pouring fuel in to prime them also will allow water in. (under the screens)
Once running 48ida's you need to take precautions to prevent that from happening, like no car washes, etc.
It isn't enough to just cover the stacks. You need to cover the carbs also.
Depending on what the blend is to your local gas, here in the North East, there is an addative to the mix at the refinery that when the car sits more then two weeks and the fuel in the bowls evaporates, tends to get sticky, dry on the Viton in the inlet valves and glue them closed.
When you disassemble a white sticky substance clearly shows on the inlet valves.
With Webers, it is an excellent idea to switch the inlet valves to the Gene Berg glass ball inlet valves. So far with them I have not had this issue, so it appears that it is a Viton valve thing.
My Holley carbs however continue to have the problem.
In my case, in 44 years of ownership the Webers only saw rain once and I ran air cleaners at that time. For the last five years or more I removed them because I have yet to see air cleaners that look as cool as the open stacks, and it runs better. Yes, the motor will ingest some dust and a few bugs but so far I see no side effects. Last year I drove it like a fool trying to stay ahead of friends with fast cars, got scared at 150 mph and backed off. It's in tip top shape but only 22 years younger than me. That means something unexpected, like a deer crossing the road, can decide to cause trouble. In Ralph Naders words, 'Fun at any speed'
You’re living the dream, as are all we Pantera owner’s!
It never occurred to me to cut in an electrical fuel pump while keeping the mechanical. This certainly can help with startup after longer times between running the car. Does anybody have information about the plumbing?
@tomkuester posted:It never occurred to me to cut in an electrical fuel pump while keeping the mechanical. This certainly can help with startup after longer times between running the car. Does anybody have information about the plumbing?
I did it on my car… electric fuel pump has check valve inside.. T before mechanical pump and T after..
very nice to get instant engine start … prime and go…!
