Hi Everyone,
I encountered a strange problem while running some hotlaps at a nearby road course.

Warning long post.

The setup:
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Downdraft Webber 32/36, Mechanical fuel pump, Full tank of gas. Good Street Tires.
Healthy electrics, good spark, clean air filter

The symptoms:
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When running with plenty of revs and pulling g's (right and left) on the track, the car would start to stumble and eventually quit. (This stumbling/dying could take up to a lap to occur (I have a dramatic Civic) I would sit there for about 30 seconds and then I would be able to get it started with some difficulty. At this point, if I put any load on the engine, it would stumble and die. I would wait a little more with it idling or bliping it (Initially it would bog in the low revs (sometimes stall) and then slowly the bogginess on throttle tip in would dissapear)and then I could get back to the pits.

When lapping, the stumbling would not necessarily start immediately, I could get a lap or 2 in before the symptoms would start to appear. The first lap out usually being a little more reserved but then it was chronic, if I pressed on the car would stall and come to a halt even if I kept my foot down. It tried different variations by trying to alternate a hot lap with a more relaxed one, it did nothing to avoid the inevitable. I tried shortshifting (it may have helped a little) I tried not shortshifting, I tried waving rubber chickens over it... Nada.
Nothing seemed to avoid the stumbles.

All this being said, once I gave it time and it cleared up, (and I when I was not trying to corner on two wheels) driveability was normal...

The hypothesis:
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My fuel pump may be either:

1) Tired
2) Incapable of delivering the volume of fuel demanded by the aftermaket carb.

This in turn causes low levels of fuel in the float bowl and causes no end of havoc once I start sloshing it around with my antics on the track. This causes the metering to go out the window and and I get bogginess/fuel starvation because the float bowl is empty or nearly empty and cannot supply the fuel asked for.

Under normal conditions it works fine because demand does not outstrip supply.

I know about this Webber's tendancy to do funny things (under right hand turns is it?)but my stumbles would linger and do it in both right and left and once started in a straight line too. I would think that it would clear up shortly after the corner (or be felt shortly after) and then clear itself no?

Does my hypothesis make any sense here?
I know this is a fuel problem; it most definitely is not spark, nor is it air.

Possible Solutions?
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Is this a fundamental desing flaw with the Webber 32/36 or is it a deficiency in my fuel pump?

I can't see it being something else but if anyone has any brilliant ideas, I'm all ears.

If it is the carb, I know one can make an adapter that will turn it 90 deg. Will this completly cure the symptoms (what happens when I stand on the brakes reall hard or accelerate??? the same g-forces are still there) I don't see how this remedies the situation.

Is a different type of carb the way to go?

If it is the mechanical fuel pump, will a rebuild kit flow enough to keep the 32/36 happy under all conditions or is an electric pump a better solution?

Or... could it be a little bit of both? In that case a different carb setup and an electric fuel pump?

The only other thing I can think of is a gummed up carb, but I would think it would run like garbage all the time if that was the case.
(A selectively gummed up carb?)

I apoligize for the long post but with fewer words I would have left something out.


Thank you again for all your help and insight,

~andre~
Left scratching his head

By 79EK1 (63.195.80.15) on Sunday, August 25, 2002 - 10:52 pm:

Hi Andre,

First, let me say that I'm jealous of your track time today! I sounds like it was a blast.

Concerning your fuel delivery problems, the Weber should be going lean on hard turns in one direction only. The problems you describe seem to be fuel starvation under hard load. It could be the Weber float needle is sticking, the mechnical fuel pump can't keep up with the Weber because of flow or pressure, the fuel filter could be restricted, or the gas tank isn't full and the fuel is sloshing around.

I would inspect the carb, especially if it is old and hasn't been rebuilt recently, check the pump for pressure and flow, and replace the filter if it hasn't been in a while. Webers are picky about the fuel pressure at the seat, so you may want to install a good regulator right before the carb.

Finally, Top End Performance says they can fix the hard right hand corner stumble and miss with modifications and jet changes for 150 bucks. They don't describe what they do, so I can't say it's worth it, or not.

http://www.racetep.com/weber.html

Hopefully, that helps. Let me know how it turns out.

By Dan (Dan) (207.90.20.58) on Sunday, August 25, 2002 - 10:54 pm:

Sounds like you should do an EFI conversion j/k

--Dan

By Nikolaj (130.161.173.24) on Monday, August 26, 2002 - 03:54 am:

Hey, those double Keihins do the same cornering right and it is not good to say the least..

I have a problem is just as hard to find:
When I rev the car sometimes it totally loses power at around 5500 rpm's. The thing is sometimes it'll pull to 7000 with no problem and then it goes well for a while..
I have my cam retarded like 3-4 degrees and the timing is good on the crank. I use an EN engine with head shaved to the max.
I have looked everywhere electronically, though I haven't yet checked my timing-advancement in the distributor...maybe it sticks and then sometimes it doesn't (that could mess things up). Otherwise I'm gonna look at the fuelpump.
Anyone have some ideas on where to look further??

BTW: have problems with your starter turning your high CR-engine?? Stick in the starter from the second gen, it is a lot stronger..

By Andre (Andre) (216.191.101.254) on Monday, August 26, 2002 - 06:47 am:

Hi Nikolaj & 79Ek1 ,
(Sorry, I don't know your name)

When it has trouble past 5500 will it still rev to 7000? If so, I think you are on the right track with the distrubutor timing. If not then I might suspect intermittent fuel delivery problems.

As for myself,
the tank was full, there isn't much in the way of baffles in them (slosh, slosh slosh)

I also changed the fuel filter right away thinking that it might be that, no change in the behaviour.

Thanks for the links, I would like to get this sorted asap.

~andre~

By Bryan (209.187.165.130) on Monday, August 26, 2002 - 07:16 am:

I would suspect a fuel delivery problem. Either the fuel filter, or the pump.


1 more thing to check Andre, is the fuel pickup in the tank. It has a prefilter screen on the end. If you have trash in the tank, then prolonged running at high RPM's will suck the trash onto the end of that screen. I have seen that many times.

By Roger Edens (Zippy) (63.64.159.2) on Monday, August 26, 2002 - 07:20 am:

The persistence of the problem is troubling. How about vapor lock? I also wonder if it's possibly and electric problem. I assume that your engine and components are running hotter at the hot lap. Could it be a breakdown of your coil at high temp?

By Andre (Andre) (216.191.101.254) on Monday, August 26, 2002 - 10:21 am:

I don't think it's vapour lock as the temps were not abnormally high (25 deg celcius) and I'm running a wagon rad). The engine water temp was very cool out on the track with the temps even below normal. I doubt that if the water temps are low, it can get hot enough under the hood to cause vapour lock after only 2-3 laps.

All the electric components are in good shape. I also checked my plugs the other day and they were the normal chocolate brown; nothing out of the ordinary. If it was electrics I would think it would occur in other circumstances than the ones that I described.

As for the fuel pick up, that's an intersting idea. But if it was clogged would it not be clogged all the time and not just when I'm cornering? Or is the fact that I'm running high rpms that is sucking the debris to the screen and then falling away when I let off. Hmmm, that too I wonder about because I tried short-shifting at the track (4000k) and the effect was the same.

It's a reconditionned tank so it shouldn't be dirty. Nevertheless, something that I should check. How hard is it to remove the pickup from the tank to have a look?

~andre~

By Bryan (216.175.78.74) on Monday, August 26, 2002 - 10:54 am:

I am not sure, but if I remember correctly, it is under the back seat area on the driver's side. I may be wrong......been too long.

The easiest way to determine if it is fuel delivery is to hook up a fuel pressure guage in line with the carb fuel line. Get it as close to the carb as possible and then drive the car at high RPM's. See how low the pressure goes.

By bruce (Bruce) (66.20.228.70) on Tuesday, August 27, 2002 - 09:26 am:

I know the fuel pump is under the back seat drivers side, I just yanked a tank out and sending unit was on top of tank, at least with cvcc, but tank is not hard to drop, loosen front two screws, then remove back two screws, tank slides out, You will have to unhook some of the hoses.

By Andre (Andre) (64.228.241.41) on Saturday, September 07, 2002 - 08:16 pm:

Well, today I had a little fun.

I took my Webber 32/36 apart and gave it a good cleaning.

I think I may have found the culprit. I had a bad gas tank at one point and was causing me no end of grief so I put in a new one, flushed the line, changed the filter and gave the carb a quick once over. All was good with the world and so I thought no more of it.

Unbeknownst to me, on the underside of where the fuel line goes in there was a brass bolt about 18mm in diameter or so. I take it out but what do I find? A small metal basket type filter filled with crud!!! It had actually collapsed inwards because of all the stuff in there. Hmmm, maybe this was the problem.

So I cleaned it all out, put Humpty Dumpty back together again and whad'ya know, she's running muuuuuuuch better. I still have to test this at the track to see if all the symptoms have cleared up but seeing how clogged the inlet was, I think this could very well explain the high rpm fuel starvation issues.

So, if you're having driveability issues with your Webber 32/36 this is definitely something to check.

And now, back to your regular programming

~andre~