my Weber 32/36 equipped 1098 will sometimes behave like it's fuel starved when under load (cruising in 3rd/4th then accelerating).
I thought it was fuel pump so switched them out (electrics, ditched an SU for a Carter) it had no effect, so I replaced the filter right before the carb and it seemed to take care of it. Now it's back, so either;
a) there's crud in the fuel system plugging up my filter so that it can't keep the bowl fuel under high demand
b)the pump system itself can't cut it (both pumps were/are mounted in engine bay, I know I should move it back by the tank)
c) I'm on the wrong track and it's ignition related.

The solution is simply lay off the gas and wait or tickle the pedal, it seems to "catch up with itself" and I'm off again.

I can accelerate to redline in 1st or 2nd no problem but in 3rd or 4th it will induce the stuttering.

Thought I'd ask so I don't waste too much time fixing the wrong thing. Not too fond of running out of gas at high load, high rpm, could detonate, no?

If your sure you have cured the fuel delivery it may be the carb If this is happening at about 2 thirds throttle it is the secondary jetting.
could be its to rich or lean and on the secodary jets may even be the air corector tube is the fault.
Is that enough of a mouth full? Well fear not here is some info that will be help full on narrowing it down.This is one of the better articles on tuneing the DGV in plain speak.
http://dimequarterly.tierranet.com/articles/tech_weber_tuning02.html

Need some jets and a E tube or two? Find them on ebay reasonable.

I have the exact same problem. I just found that my pump cuts down to 1/2 pound of fuel pressure at times. I had purcolation in the bowl and vapor lock and all kinds of issues including running out of gas pulling hills. Gonna try a new fuel pump and see what that does for me.

The fuel inlet on my Weber is on the inboard side, should be swapped over the outboard probably, as it is I tied the water hose to hold it away from the inlet line but I've also since turned off the lines to and from the heater core. I should probably move the pump to the tank as they push much more effeciently then they pull, I did both of these to my old Opel and it helped fuel delivery alot. I've got the same issue with two different pumps though so I wasn't sure that was it. I'll have to do a flow test. I'm sitting at a coffee shop near work on the MG's first commute in, I'm REALLY nervous.

Someone check my math and my logic on this but.....
Logged some miles today. Had a couple episodes as mentioned above. Just pulled the line off the carb and ran the electric pump until it filled a cup's worth, took 36 seconds, so it would take 576 seconds (9:36) to fill a gallon (16 cups to gallon US) after an hour that's only about 7 gallons (US) per hour.
That stinks.
I'm not sure what volume a 32/36 needs but 7 gph isn't very much.
Guess I'd better move that pump back to the tank, eh?
Maybe re-do the line?

Check the pressure too. That is what I did and it showed the low pressure. With a higher pressure it can get more fuel past the float and keep the bowl full. Mine would literaly almost run out of gas on a hill if I gave it too much gas, just backed off and give it a little and it catches back up.

I checked mine with a quart jar on a high shelf and it worked out to about 9 gallon an hour so I thought I was good but the area their at that needle and seat is very small and you got to be able to force gas through there. Mine was only 1/2 lb of pressure. Find a gauge and check yours.

Am i thinking crazy or does 7 gal/hr seem like MORE than enough... let say you have it wound out in 1st gear, 5000 rpm going what 18 mph... that would be 18 miles/ 7 gallons,.. about 2 1/2 miles per gallon? seems to me... (and i don't really KNOW anything about these cars) 7 gallons an hour is P-l-e-n-t-y...


......."the book" say... 56 pints an hour.. for a MK III..oops thats imperial pints......67 US pints/hr..... so.. 7 gals is a LITTLE under...

Yeah, 7 gal an hour is a lot for any vehicle to burn and a midget is not going to burn out a tank of gas in an hour. you are doing just what I did, flowing gas out of the hose. Flowing through the needle and seat will be much less than that. Plus you got the gas under low pressure trying to boil in there and creating pockets of vapor that can hold back the flow. I can relate man, I can't wind mine up tight for long or it starts running out, then I back off and just touch the gas for while and it straightens back out. I can feel it coming on at times and avoid the herky-jerky.

I've got a pressure regulator on the car, set at 4. Haven't confirmed that is accurate though, gas does not seem to come out with much pressure, just sort of dribbles in the jar. I've not ever heard of too little pressure on a Weber, too much yes. I guess it could be.
BTW this same pump, when on my Opel GT gave 16 gph when mounted in the engine bay, moved to the tank and increased to 3/8" fuel line, it gave 23gph. Guess I'd better just mount the bugger where it should be. (BTW filter between pump and carb is new, not that it couldn't be clogging up again already.....)

That regulator is not going to raise the pressure, only lower it to whatever setpoint you have. If you have only 1 lb of pressure from the pump then the reg is going to only give out 1 lb.

Depends on the horsepower.

The brake Specific fuel consumption of an engine ranges from 0.35 to 0.6 lb/hr/hp. Average is about 0.5 lb/hr/hp.

This translates to:
The average engine, when putting out 100 hp, will require about 8 gallons of gasoline per hour.
D

Wow, that Dave always has a sharp pencil.

Just re-reading these posts and am wondering whether the problem is the tank itself? We're in Scotland tight now and every time I pour tea, when the teapot starts to run out the teabag gets into the spout and inhibits flow. Could you rig up a gas can "tank" and bypass the regular tank completely? This might point out if the issue is in front of or behind the fuel filter. I can't remember if you have a new tank? but my old one had a ton of sludge in it.

"so I replaced the filter right before the carb and it seemed to take care of it. Now it's back"

If that solved it doesn't it seem logical that is the problem - fuel filter is getting clogged? And if so than what is clogging it? Dirty tank?

I'd say...

a) Shake, or cut open that fuel filter... is it full of swarf?

b) Is the Carter a 'green' / 4070? If so, should be ideal... but yes, mounted down near the tank. I can certainly imagine that in certain high-load situations it might cavitate / have problems delivering enough fuel, if mounted high in the engine bay.

Or, as you say... might be the carb. The fact that fiddling with the filter seemed to fix things would suggest otherwise, though.

I also would clean the tank.

No idea if tank was ever touched up. Took several runs yesterday. No problem until 3rd run of the day, could barely keep her cruising on the level at 50 mph, finally slowed for a turn and then it took off and ran great, no reoccurrence, so it's very intermittent. I'd think if the filter was clogged it'd be more persistent. Oh well, I just created more pressing matters....tried to run a plug in the dipstick hole just to see if that's where a leak was...plug came out and I oiled the engine bay thoroughly! Might have to start a new thread on that one. This dipstick is weird.
Also I watched the speedo needle bounce and then fall to zero a minute ago......

The pump that is currently on there is of the solenoid variety.
Looks like this one.
Pump
Have the SU I took off, which is probably just fine too. Both were mounted in the front left corner of the engine bay, as high as the carb.

I would expect junk in the tank. Covers the pickup from time to time enough to shut it down or almost so then shakes off.

I'm inclined to think it's a tank/filter issue, too. I had the same problem. The car would run great around town, but as soon as I tried to push it to 55+ the filter would get completely clogged. I had a ton of sediment at the bottom of my tank. New tank + new filter = no more problems. If you have the old filter, blow some carb cleaner through it and see what comes out.

If it's the tank, then the filters will just continue to get clogged (at the worst times, I'll add). My second filter lasted all of ~40 minutes of drive-time before it got stopped up.

B

I had this problem years ago when I drove the car. I bought one of those clear glass filters that you can take apart and clean out. I put it right before the pump. You can just look under there and see how bad it is.

The filter I took off was see through, looked fine paper is a bit discolored. One I had on hand was a canister type so it is on there now, can't see into that one. I'll back burner it for a while while I tinker with other things.

Finally got around to moving the pump and it had no effect, that is still very low volume of fuel delivery-7gph. I figured I'd start with the pump move since it "should" be back there anyway. I had to cut the fuel line from the tank right near it's outlet (leak in the metal line) and I caught some gas it looked TERRIBLY dirty to me, I let it evaporate all day and the pan has a nice brown powdery crud in it. So it looks like I'll be dropping the tank next. Although I'd think it would eventually totally plug up or drop so low as to make it undrivable. This is not the case. I can run down the highway at 70mph for several minutes, then a bit later struggle to keep her going 40mph, could this be filter clogging and unclogging?
No matter, tank must come out and get treated, all filters replaced, then start over.

Yep, I would also bet that it is the in tank filter cloging and uncloging. Pull that tank have it cleaned and lined.

If your tank is rusty inside, you need to address it before driving too much. Loose crud in your carb will make it a bear to dial in later down the road. Seems you can never totally clean the small passages out. Rusty tanks have caused a lot of fuel delivery issues in many types of older cars.
JC

This could explain why the primary barrel on the Weber always looked so carbony, although the inside of the carb looked pretty good, likely thanks to inline filters. Alright, I'll drop the tank and fire up the grill. I have a Kreem kit already so I'll use that. That and new filters "should" resolve the fuel supply issues. I'll probably just nix the in tank filter and have an inline one right outside the tank, another just before the carb. As long as the original 1/4" ID metal lines are good yet, I assume I'll get close to 15 gph at an acceptable pressure after all is done.
Maybe if I'm lucky I'll be able to start tuning this thing before winter!

Make sure you are feeding the weber through the supply line and not the fuel return line. (assuming you have a DGV) Pull the lines off. One side will have a restriction in the line and the other will be wide open. The restriction is for cars that have a fuel return. Mine doesn't, I don't know about yours. Anyway, I made this mistake and was trying to push fuel through the orifice and had plugged the wide open inlet. The orifice is about 0.060" or so.

Just a thought,
JC

Interesting on the different inlets. I assumed they were the same, just right or left for different applications. I was going to move the inlet to the other side to get the supply line away from engine heat but now maybe I won't. Both Weber's I've dealt with had one side still "plugged" (as in never opened after the casting). Ironically my last Weber (38/38) had the inlet on the wrong side (its right), I moved it to the other with no negative effect. This 32/36 is on the carb's "right side" but should really be on the left/outboard side. Not a big concern though.
I suppose if you buy the Weber DGV for a certain application, it would come with one side or the other opened.
Anyway, my fuel flow measurements thus far have been right before the carb and it's a trickle, measured at 7gph. Where exactly the hold up is I don't know but since new inline filters didn't do it, and different fuel pump didn't, and moving the pump didn't I'm assuming the tank filter itself is clogged. There were actual chunks of goo that shot out when I cut that line.
Be nice to put this issue to bed and move on to the next. Soon I'll have this thing totally road worthy (although I've put 1200 miles on this summer as it is!)

Your engine consumes the same amount of fuel at a given RPM wheither the car is in 1st gear or 4th gear, so I'm wondering why the difference. Are you sure the ignition timing is correct? At cruise in 3rd or 4th you'd be seeing a lot of vacuum advance and then drop it back as you opened the throttle. I think I'd have the distributor and vacuum advance unit checked.

Oh sorry about the bum advice. I guess I should have read the whole thread. Good chance it is the inlet in the tank. You may have trouble with that after you seal the inside of it too. That is why I just bit the bullet and bought a new tank and sender from VB right after I bought the car. The PO had put a bunch of filters in series before and after the pump trying to capture the rust...lol What a mess.
JC

If you do seal it your going to what to poke a hole in the pickup screen Heck it may be all you need to do now... Then put a pre pump filter on it. Something clear and large.

That can't be true. Doing 3500 RPM in first, the air resistance is negligable compared to doing 3500 in fourth gear.

Also, that's assuming no accelleration or decelleration, which is rarely the case. Going from 2K to 5K in first and going from 2K to 5K in 4th is drastically different in terms of work performed, and therefore fuel required.

This is a tricky subject. I think it is dependant on engine rpm and not what gear your in. I say this because you can only cram so much air in a cylinder per stroke. That air moving is what is causing the entrainment of fuel in the carb. So at a given rpm you would use a given amount of fuel assuming the air/fuel ratio isn't changed by the slight increase in pressure under the hood from the speed.
I could totally be wrong though.
JC

Eingine is a pump if you could have a flat curve it would use the same amount of fuel for a given amount of work - time - distance but we know the curve is no where near flat.its al in the curve effenecy.

Went trolling around the archives a bit and found this in post 430436
"Did you check the flow ahead of the pressure regulator? If the adjustment is off or slipped, that might be where the restriction is. I'm a little wary of pressure regulators. In general, they work well only within a range of flow rates. In a LBC, the flow starts and stops as the float valve opens and closes, and I'm not sure how the regulator might respond. Might be better just to have a pump that puts out the right pressure (2-3.5 psi)."

So, for fun I pulled the line BEFORE the regulator, stuck the hose in a 1 liter bottle and turned on the pump....and quickly turned it off because it was filling FAST!
Regulator all along? Probably could have left the pump where it was!.
I did not check the flow rate but it has to be 3x what it was, probably more.
So I tore down the regulator expecting to find something. Nothing looked wrong. I have a spare but I really wonder if it needs one at all. The pump on the car now is a Stewart Warner and probably 5-7 psi. That's probably close to too much for a Weber.

Remember that it doesn't take long to reach redline in 1st and 2nd compared to 3rd & 4th. The extra time spent @ full throttle in 3rd and 4th could empty your float bowls. Where a short blast up to redline in 1st would not.

I put a different regulator on it, checked fuel rate.
1 pint in 21 seconds is about 21 gph (check my math!)
Bet that should do it!!
Pressure regulator set on 3. Not sure how a regulator that dials down pressure doesn't effect flow, I suppose it does. Seems hard to get 30gph at only 3 psi but whatever.
Not that the tank isn't filthy and could use a good clean but it sure looks like the pressure regulator was garbage.

I've got the Holley low pressure regulator on my car. It is a bit large for my taste but it sure does the trick. It doesn't seem to restrict flow at all down as low as 1.5 psi. I've since cranked it back up to 3.0. I can look up the model number later if your interested. Ok later just came. I got the 12-804 but the 12-500 will work too. The 804 is chrome. I picked it because I found it cheap on Amazon. Anyway, they are good down to 1psi.
JC

Thanks, The two I had are similar dial style, like :
these

I took the "bad" one apart, expecting goo or sludge or something, but it looked just fine. Probably the dial portion (simple tapered needle design) was not opening like it should.
The new dial one is the same design but is letting gas through much better, quick test drive last night (early this morning, truth be told) and I did not have any issues although too soon to know.

As you've discovered, those are fuel RESTRICTORS not regulators. The Holley one is what you should be using. Not to mention that the round ones did (and maybe still do) have problems with "modern" fuels... they leak, and the diaphragm perishes.

Peter C

Interesting that one seems to work fine (flow is great, no idea if pressure is actually what it claims) the other restricted flow to a trickle and did it on various settings. They can't ALL be useless? I'll see how it goes.

Quick report: the problem has not returned and I've run it hard, I think I'm ready to declare "problem solved" on this one. Remember to suspect everything, including those cheap pressure regulators!