Weber 500 problems....still

ghce

ghce

Well-Known Member
Well I thought I had solved my hard restart problems with my W 500 carb by installing an edelbrock heat insulating gasket as it seemed to be ok and the power had increased when taking off from sitting at the lights when hot as well, no more hesitation. However as the weather has improved I have been taking the car out more and it appears that my earlier prognosis of a cure was not as well founded as I had led myself to beleive :( What really has me puzzeled is that the engine has to cool right down (3 or 4 hour) before it will restart not just 30 mis or an hour. The car has an electric pump which I might relocate to somewhere cooler as it's currently in the engine bay mounted close to the washer bottle, so hardly the coolest of environs to live in and maybe I should re rout the fuel line as well? once I have done all that I might have to look seriously at the carb, though I dont know really where to start I cant imagine it's a float level problem really a bit odd with the way the carby or engine has to be cold to restart???? any ideas??? any one????


Graeme
 
The heat gasket I fitted comprises of four heat resistant gaskets and three interleafed aluminium heat dissipators.

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I also had a major problem of manifold heat. The S/S tubular headers gave off so much heat that it would melt anything susceptible under the bonnet, and also, as heat rises, it would heat up the carb and inlet system when I stopped because the throughput of air stopped. I wrapped them up which helped a great deal but have now ceramic coated them.

manis.jpg


When I bought the car, the fuel hose came up from the back of the engine, over the manis to the regulator which was sited behind the servo, then back out, turned left to go back over the manis again then turn right into the side of the carb. I re-sited the regulator behind the power steering resevoir, and the fuel now enters the carb from the back. All of these things made a difference.

1071208enginesm-2.jpg


What pressure are you getting from the output on the regulator?

Richard
 
Progress report

Earlier this week I reinstated the fuel return line to the tank as on the initial instal we had just blanked off the return line as the electric pump was rated at 3.5 to 5 psi and the carb was rated at 6.5 pounds, all good when the engine is running and the fan blades pulling air thru, how ever when in the non start condition I noted that when I loosened the clamp on the fuel inlet pipe to the carb that there was a considerable psi build up of hot fuel with no way of the pressure being releived, so with the return line that excess pressure is releived. However still no joy on restart so stripped carb to inspect float levels and yes they were out in both directions so adjusted to a lower float level, also found a manufacture defect in a venturie (hole) which I soldered up, reassembled and tested still no joy (reset idle adj as well).
Next step I took a can of freeze spray to the distributer capacitor as by this time I am thinking maybe it's not a carb related fault.....still no joy! Grrrrr.
At this stage the fuel pump is still located by the windscreen washer bottle and like the rest of the fuel line it gets toasty however I have petrol in the carb and fill line to the carb so it's not a vapour lock problem (may still be boiling internally in the carb however). Next step is to buy an infrared thermometer and do a heat profile on the carb from cold to hot running and then to the non start stage and progress that heat reading point to where the engine will restart. Dont know if this will ultimatly help me but it will give me a handle on the temps that the carb see's. I know there could be a few off the wall solutions that will work ie seperate cool air feed blowing on carb or other non standard fixes but I just cant beleive that it can not be tamed by more traditional methods, after all this carb works on thousands of other Rover V8's and yank tanks.

Just rechecked my fuel pump rated pressure and see on the box some one has written7.5 psi??? this might require some investigation also!

Graeme
 
I do like a good mystery! First off are you quite sure you are dealing with a heat soak related problem? Absolutely no problems when running?

Assuming affirmative, then I suggest widening the search to everything that might be heat influenced. In particular the ignition system. As you noted, capacitors are supect in these circumstances, but so are coils and ignition leads. Any engine that's had enough attention to warrant a Weber really ought to have electronic ignition of one sort or another with a directly fed 12V coil and in particular Magnecor plug leads. You know you're going to do these sooner or later, so do them now and eliminate a complete category.

Next step I would suggest is to try to eliminate the heat soak by having a nice fast run and then immediately you stop opening the bonnet! If that doesn't allow a swift restart then the problem isn't heat soak! If it does then the search is on again for things that are susceptible to underbonnet heat.

If it doesn't restart OK then you're looking either for faults in the carb or for something really bizarre such as a faulty changeover for the coil voltage.

If you were in the UK I'd suggest you take it to a rolling road that understands the V8 and Webbers. Quattro now knows one (in Blackpool?) and I know one just outside Swindon - but a bit far to bring your car!! It is clearly established that Webbers don't work straight out of the box but need rejetting on a rolling road to suit the engine they are on. And it's a really specialist job, in theory simple, but experience is everything. Has something like this been done to yours?
Chris
 
The engine will still restart after switch off when hot for about 5 to 10 minutes, but once sat longer than that it won't, so you can drive down the road and whip into the local dairy buy a paper and likely be ok for the restart :) .

The motor when running is faultless, no misses no rough running and stacks more acceleration than the hif6's, when I got the carb I emailed RPi for the needle and jet sizes and duly followed their recommendation.

Changed the coil to no effect, still have spark in the fault condition when veiwing an externally connected spark plug.

Another avenue for me to try is maybe change the thermostat for a 78 degree rather than the 82 thats in it and see if that improves it though I am a bit loathe to go that route as the car has a lot of kilometres ( aprox 200,000) done at a working temp of 82 and any thing less will mean that the rings and bores will be operating at a less than optimal point.

you are of course right about the electronic ignition and this serves as a good excuse for the upgrade, had my heart set on a mallaroy dual point but the cost at the moment has stopped my plans on that, ultimatly that should happen.

I doubt if I could find any garage with expertise on Webers here in NZ as the agent for them here in NZ wants over NZ$1200.00 for a weber 500 :shock: , so not many around :LOL: I bought mine from the US for about NZ$250.00 from an online retailer about the same sort of cost for the inlet manifold so for most people weber ownership is a bridge too far.

Graeme
 
OK, so it really is a heat soak problem. If the coil's been changed, what about the capacitor? There's known to be some bad batches around in the UK and heat soak into the innards of the distributor could be expected to be quite slow? Only other thing I can think of is some sort of vapour lock problem. Start by leaving the fuel filler open while it is going on. Likewise make sure you have venting open from the float chambers, whether to atmosphere or back to tank.

Chris
 
ghce said:
The engine will still restart after switch off when hot for about 5 to 10 minutes, but once sat longer than that it won't, so you can drive down the road and whip into the local dairy buy a paper and likely be ok for the restart :) .

The motor when running is faultless, no misses no rough running and stacks more acceleration than the hif6's.......
Click to expand...

Exactly the same problem I had when I fitted a Weber to our old SD1. Never did get the bottom of it unfortunately, but for reference we also fitted a new Mallory Unilite distibutor and Amp, new coil, new Magnecor leads, new fuel pump, exhaust, starter, inspected/cleaned engine earth leads ect, etc.

The car was very well serviced, low mileage and made good power when running, as well as driving really well. We also had it tuned and set up a couple of times (including a rolling road session), by people that knew what they were doing but couldn't find fault with the ignition, jetting or fuelling anywhere in the range.
It must have been a heak-soak problem then, or something similar. Not quite sure why it would be so sensitive to that though, as the SD1 engine bay in particular is fairly large with good air-flow, and we were still running the standard cast-iron exhaust manifolds.

What I mean is, throwing new/better parts at it didn't offer us any solution ultimately, though the engine was very resposive, made good power and was relatively economical when it was running because of it. It was just starting the damn thing!
 
:D I am glad someone else has had the same experience with this carb, bearing your comments in mind maybe a more radical solution might need to be employed. A friend of mine has played around with smalll heat exchanges of a basic type (water cooled) i have been thionking to interface the carb and inlet manifold with one, this would provide a very controlable heat level to the carb, but it is pretty radical........


Graeme
 
ghce said:
Richard, what psi do you run into your weber?


Graeme
Click to expand...


I run mine at 5.5PSI

I had a mallory dual spark and to be honest, it wasn't very good. When I fitted the SDI contactless dizzy, it ran a lot better.

It could very well have been heat damage with the mallory, but I will never know.

Richard
 
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