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Discussion Starter #1 (Edited)
After 8 weeks of being in the garage the tuner has given up so its back to me. I've posted my issue before but the tuner thinks my carbs are over fueling and need smaller chokes. The ones in there are standard size 32 but he has tried to find size 30's but without any luck.

He and me have scoured the internet and I can't find any reference to them, does anyone know if these are available and if so where I can get these from?

thanks
 

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Simon, that diagnosis is completely ar*e about face. Smaller chokes will make matters worse, as they only determine the amount of air that can travel through, nothing to do with the fuel................
If you put smaller chokes in, the ratio of fuel to air will be greater on the side of fuel.
Have you checked what size main jets and idle jets are in your carbs, compared to what should be there ?
You definitely don't want 30mm chokes in a 2 litre.
Overfuelling is almost always :-

1. Idle jet. If the overfuelling is seen mainly at below 2000 rpm, then the idle jets are most likely the culprit, (too big)
2. If it's from 2000 rpm to WOT, then the main jet.

It's unlikely to be a (too small) air corrector, as that only has a big bearing from say 5000 upwards.
Steve
 

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Discussion Starter #4
Thanks both,

GTA R, it is below 2000rpm. It happens after about half an hour of driving in particular when you've been driving freely but then come down to a slower pace when hitting traffic etc. The feeling is actually like it's being starved of fuel as it starts to kangaroo but when you put your foot down it clears and all's fine again. The guy said it was overfueling and the fuel wasn't being used which caused the Kangerooing. The manual states the idle jets should be 0.50, I'm not sure what's in there at the moment but I'm going to collect the car now so I'll have a look when it's back.

I notice you can't be too far away from me, is there a garage you'd recommend? They were rebuilt by Chesterfield Motor Spares but have been in with JP Autotechnics this last time.

Thanks
 

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Thanks both,

GTA R, it is below 2000rpm. It happens after about half an hour of driving in particular when you've been driving freely but then come down to a slower pace when hitting traffic etc. The feeling is actually like it's being starved of fuel as it starts to kangaroo but when you put your foot down it clears and all's fine again. The guy said it was overfueling and the fuel wasn't being used which caused the Kangerooing. The manual states the idle jets should be 0.50, I'm not sure what's in there at the moment but I'm going to collect the car now so I'll have a look when it's back.

I notice you can't be too far away from me, is there a garage you'd recommend? They were rebuilt by Chesterfield Motor Spares but have been in with JP Autotechnics this last time.

Thanks
Simon, let us know what idle jets are in there first. If they are what they should be, then check that none of the accelerator pump and idle jets are blocked.
If both ok (and they have been rebuilt properly, have no spindle play & aren't dragging air in ), sounds more like a fuel pump (do you still run a mech pump?) or a spark / electrical problem to me, particularly as it manifests itself when it's got warm.
 

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Simon, just been reading your earlier thread on the starting / running problem.
Is the car a 1600 or 2000cc ?
I'd been replying on the basis that it was a 2 ltr, but if it's a 1600 then it does need 30mm chokes.

When you cleaned / rebuilt them , did you put the accelerator pump ball bearings and brass rods in the right way ?
The ball goes in first, followed by the brass rod & then screw cap. You'd be surprised how many carbs I get here with them fitted the wrong way round.

Steve
 

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Discussion Starter #7 (Edited)
Thanks Steve, mine's a 2 ltr and the carbs were professionally rebuilt ( so hopefully correctly!) to try and fix the issue which I've had since I've had the car but it didn't improve things, I did try the carbs from the Spider and it was still the same which led me to think the issue wasn't carb related. I did tell the garage this but he was sure the carbs were at the root of the problem, although he said the carbs were perfectly set up and it ran 'like a sewing machine' up until the point it started?

Thinking it was fuel or electrical when I first started, I've so far replaced the plugs, leads, coil, fitted a 123 distributor, all the fuel lines, removed and cleaned the tank, fuel filter, stripped and tested the fuel pump, new head gasket after skimming the head and reseating the valves, new thermostat. It's been to 2 separate different tuners and 1 Alfa specialist, none of which have been able to get to the bottom of it ��

Here's the old thread which I probably should revive.

http://www.alfaowner.com/Forum/the-classic-alfa-romeos/980314-hot-running-issue-2.html

My daughter took a video of it happening earlier, not brilliant but it might help. Ittook a while to kick in, we must have been driving for 40 mins and came on when we had to slow down for speed bumps, as you can hopefully see at the end of the vid I changed down and gave it some gas and it was fine.

 

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Simon, if you've already had a different set of carbs on, then it is very unlikely to be a carb issue, especially if you've checked the jets I alluded to previously and they're ok. More like fuel pump or a spark problem.
Did you actually change the pump ?
The original Fispa pumps are quite reliable but I've seen lots of the aftermarket ones (very often used after the originals have finally died), fail many times.
Steve
 

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Discussion Starter #9 (Edited)
i haven't had a chance to check the jets this weekend but yes I'm not so sure they're the culprit.

I didn't change the pump, it's still the original Fispa one, i removed it, gave it a clean and check, the push rod is free and working as it should, no leaks from the gasket. When performing a basic operation check, with the fuel line disconnected at he carb the fuel pulses out as expected when the engine is turned over. The garage did check the pressure to the carbs and this was fine too.

I suppose a drop in pressure could cause the symptoms resulting in under fueling ( not over fueling as the garage suggested) as this would make sense that it clears when I put my foot down. Not sure what could cause this though, the pumps functionality is pretty rudimentary and I'd smell any leaks??

The only other thing to mention, clutching at straws now, is that the fuel gauge only registers when half full to full, anything less than half and the needle just drops to empty. I've always put this down to a faulty sender but could this be part of an electrical gremlin. I have tested though and the car judders no matter how empty or full the tank is, no difference with standard to super unleaded either.

Edit. Just checked and the pumps are pretty cheap so happy to try a new one in case, looked at the Facet electric pumps too, maybe they're worth a try??
 

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Edit. Just checked and the pumps are pretty cheap so happy to try a new one in case, looked at the Facet electric pumps too, maybe they're worth a try??
Simon, I always fit an electric pump.
If you do try one, use a cylindrical, reciprocating one such as a Facet Silver or Red top. You can't hear it in operation unlike their cheapo box shaped ones which are very noisy.
I've used many of them in the past with no issues. I currently have a Mitsuba (best of the best) on my Ti Super Rep, and have the utmost faith in it. I couple it with a Malpassi Filter King to ensure 3.5 psi at carb height. It may well be that the Fispa is good enough to pump ok when cool, but at low revs when warm isn't up to snuff.
Did you check all the internals when you had it to bits ? If the diaphragm is weak or even slightly holed, it won't be pumping to its correct pressure, particularly at low revs.
 

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Discussion Starter #12
Save all this unknown, take it to a rolling road where they specialise in carbs. I use Pete Baldwin at wilsher garages in Cambs.
That's where it's been for the last 8 weeks but they couldn't sort it 😡
 

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Discussion Starter #13
Simon, I always fit an electric pump.
If you do try one, use a cylindrical, reciprocating one such as a Facet Silver or Red top. You can't hear it in operation unlike their cheapo box shaped ones which are very noisy.
I've used many of them in the past with no issues. I currently have a Mitsuba (best of the best) on my Ti Super Rep, and have the utmost faith in it. I couple it with a Malpassi Filter King to ensure 3.5 psi at carb height. It may well be that the Fispa is good enough to pump ok when cool, but at low revs when warm isn't up to snuff.
Did you check all the internals when you had it to bits ? If the diaphragm is weak or even slightly holed, it won't be pumping to its correct pressure, particularly at low revs.
Thanks Steve, I think it might be new pump time, I can't remember exactly what the diaphragm was like, not sure I'd know the difference between a good and a weak one without comparing side by side so for the sake of £25 I'll try a new one.

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You could try pulling out the choke a fraction when the fault's occuring? If the problem clears then it's too lean, if it gets worse then too rich, no difference then timing or something else.
At least you might get some extra info?

Also have you checked for small air leaks? carb mounts, servo vacuum pipe, crankcase breather pipe?
 
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