1457 1983 GL with weber 36TLP conversion requires choke

Car (1457cc GL 1983)has been laid up for about 4 years now, carb (which I think is a 36TLP - or whatever was available as a conversion from a 1B3 7 years ago) has been rebuilt as it wouldn't keep running without pumping the throttle.

Now it runs, idles fine, full throttle is fine - but part throttle requires 1/4 choke otherwise it misfires, cuts out and generally just doesn't run.

Inline filter is clear, albeit mostly full of air even after running for 10 miles and an hour.

Going to replace the fuel lines in the engine bay along with all the vac pipes (but they are producing vacuum at the ends).

Any other things to check?

Cheers.

Edit: Changed carb to 36TLP

If full throttle is fine its not a fuelling issue.

It might be timing, worth checking. But also worth checking is the tune on the carb, you need at least a CO meter to do this but ideally an AFR meter and a rolling road run. Its completely possible that it will have the wrong jets in the carb for your engine, for example.

Pumping the throttle puts more fuel in (via the acceleration pump) so it might be lean, but without the intruments its a complete guess.

The mixture is adjusted by a small screw which is recessed on a slight angle fitting on the front left of the carb, if its the Weber I'm familiar with.

The car before it was laid up was running perfectly, starting fine, running fine, no misfires.

I assume the timing hasn't been changed (I wasn't around when the work was being done) but I've ordered a timing gun to check.

Yeah its worth checking the timing but also mark the timing where it is now, in case you want to revert back to it if you start adjusting it and it no longer makes sense.

Have you looked at the spark plugs and/or changed them? If you do, clean out then spray plenty of WD40 or similar into their holes (while they're there) because they can get rusty and snap in the head, which obviously makes removal awkward.

Also would be worth closely looking at the condition of the ignition leads and a check inside the dizzy cap etc, not sure if a 1983 will have electronic ignition by then or have points.

With respect to the timing, is it supposed to be set to the tab or the diamond shape?

(I.e. there is a sticky out rectangle block then a diamond cutout, I assume the rectangular block is TDC, is the diamond the correct BTDC?)

All plugs look fine, leads were brand new.

Edit: Carb is actually a 36TLP, not a 32/34!

I think you've got it but not 100% sure - its in the manual though. One of the marks is 0 degrees and one is the timing mark, which is a little BTDC or something like that. I tend to ignore the timing marks and set it to roughly 0 deg then tweak it by ear once the car is running.

I have the haynes manual but as I recall it didn't actually specify what 13 degrees BTDC actually was.

Checked the timing yesterday - I think it was ~3 deg ATDC now it is ~5 deg BTDC (just about see the 0 degree mark - didn't push it further until this fuelling issue is sorted).


I'm going to change all the vac pipes and fuel pipes next time. I used some carb cleaner to see if there is a leak but didn't find one…

However it does hesitate under full throttle, so which jet is the cruise/main jet on the 36 TLP? I can't find anything useful on it!

I can't find any useful info on the internet about the jets on a 36TLP but obviously jets for a weber are a fairly standard thing and there's several firms selling jets, or rejet kits (ie with a selection of them). Do you have a way of measuring AFR to determine the problem is with the mixture though?

Nope - I'll have to take it to a garage for that.

Just want to take it apart to give it a damn good clean to see if I can sort it myself.

All very well buying the jets but without knowing where they go… not so useful!!

Cheers.

Replaced all the fuel lines, vac pipes etc and still splutters and cuts out on throttle.

Took the carb half apart and blasted it with carb cleaner, it was full of fuel so I don't think it is the pump.

25% of the tank is 4 year old petrol, 25% of the tank is new and 25% is year old.

So we are thinking bad fuel now, so going to run it with the choke on which should burn some of it.

 

How much is a wideband AFR gauge these days? I have one, but ideally need to weld a bung into the exhaust system to get decent readings at idle - currently the probe is in a tube at the end of the exhaust, it works with throttle but not idling due to the gas flow etc.

I think if I need to fiddle around with jets I'll just get a kit of various ones, then take the carb apart and see what goes where etc.

Its that or a rolling road session (or two) with someone who understands carbs as well as EFI etc

Just going to run it back to its new home now.

100 miles with choke out should burn a decent amount of the tanks (not a bad thing need to empty to replace the filler pipe!)

If however new fuel doesn't fix it then I'll look at stripping the carb again.

If running the car with the choke out you may need to clean the spark plugs once you finish as they will be black and covered in soot/un burnt fuel?

mark1gls said

If running the car with the choke out you may need to clean the spark plugs once you finish as they will be black and covered in soot/un burnt fuel?

It depends, if the car's already running lean then a slight adjustment of the choke can enrichen it and could either bring it to correct AFR, or go too far and send it rich. In days gone by people would pull the spark plugs and judge by reading (looking at) them. Nowadays, one would use an aftermarket AFR meter. Running lean is more dodgy than running rich due to detonation and possible engine damage. If too rich, you'd "bog down" before any further damage although massively too rich could wash the bores of oil and lead to greater wear there.

Really you need to get to grips with if the car is too lean, right, or too rich. Aim for 14.7 at idle and 12.5-13.0 above 3000rpm or so at wide open throttle. Sometimes you can go a little on the rich side and advance the timing a tweak more for better power too.

Its a shame nobody does an equivalent to something like Holley Sniper EFI, which is a kit which self-learns, is plug-and-play and is basically a drop in replacement for the carburettor.

Sniper EFI Self Tuning Kits - No Laptop Required

Pop in to a local friendly garage and ask them to put the car on there  CO2 machine (as used for an MOT)?
They may do it and tune the car for beer money?

I bought a 2nd hand CO2 meter from ebay for £40 as it's close enough to get my car set up, it's not going to be as accurate as a £1000 garage one.
One like this…
http://www.ebay.co.uk/itm/Gunsons-Gastester-MK-2-MOT-CO2-Emmisions-Tester-/262436941361?hash=item3d1a75ee31:g:NgIAAOSwSgJXN0p2

mark1gls said

Pop in to a local friendly garage and ask them to put the car on there  CO2 machine (as used for an MOT)?
They may do it and tune the car for beer money?

I bought a 2nd hand CO2 meter from ebay for £40 as it's close enough to get my car set up, it's not going to be as accurate as a £1000 garage one.
One like this…
http://www.ebay.co.uk/itm/Gunsons-Gastester-MK-2-MOT-CO2-Emmisions-Tester-/262436941361?hash=item3d1a75ee31:g:NgIAAOSwSgJXN0p2

1. Its CO, not CO2 but its a common error these days.
2. Its really only useful at idle, these types of DIY meters are only designed to cope with the gas flow at idling. Rev the car up a bit and it will not read properly. And try hooking it up during running (ie under load) and you'll get nothing useful - the reading needs to be a steady state one, its far from instantaneous. Also it won't tell you how lean you are on the lean side - CO basically drops to about 0.1-0.3% from just lean of stoich to the lean misfire limit. It does correspond not-too-bad on the rich side though.

As said before, you really need some kind of AFR meter to properly set the car up.

I'll be taking it round the corner for a quick check on their machine - but I can't change on throttle mixture?

Mixture screw will have an effect on idle but barely any effect at higher loads/speeds, for this you really need to get into swapping the jets etc.