JoelP
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| posted on 7/9/22 at 02:37 PM |
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A few questions about carburetors
Afternoon all.
I finally picked up my little car from Bogg Brothers after 7 years off road! They've done a cracking job of sorting it, but I've got a few
questions for you all, if you could help.
It's a 2L pinto on webber 45s.
The engine doesn't always turn off with the key, so I just stall it. Is that just a wiring issue?
If you turn it off but leave the fuel pump on (separate switch), petrol starts to drip out of the air filter. Is that normal?
When I don't have the fan switched on, it creeps past 100 degrees even on the motorway. I'm assuming the thermostat must be not working, but
at least there's an override. Would you expect a locost to need a fan on regardless? I'm tempted to open some vents up.
Finally, after about an hour at speed, it started coughing if I applied full throttle too fast. And maybe a similar issue, it started misfiring after
hitting 105 degrees. Is that normal for carb'd engines?
Anyway, had great fun driving home. Hoping to get it 300 miles up to Islay in a few weeks time!
Any help appreciated!
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JoelP
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| posted on 7/9/22 at 03:44 PM |
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Just to add, the misfire is still there even when it's cooled. I'm pretty sure it's too much fuel - when I turned the pump off, it
pulled out beautifully, before starting to run dry after a few minutes.
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JoelP
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| posted on 7/9/22 at 04:01 PM |
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And idling at 2k after a run.
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gremlin1234
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| posted on 7/9/22 at 04:14 PM |
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what fuel pump are you using, and do you have a fuel pressure regulator?
[Edited on 7/9/22 by gremlin1234]
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adithorp
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| posted on 7/9/22 at 05:17 PM |
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If it was a stuck 'stat then the water wouldn't be circulating to the rad and the fan would make no difference. Is air able to get passed
the rad' instead of through it?
When you say it runs after you switch off, does it run normally or jvery lumpy? (ie. running on). Try backing off the ignition timing a couple of
degrees.
Fuel running out could be sticking/leaking float valves. That could also cause it to over fuel and result in misfire.
What exactly did BoggsBros do? Doesn't sound like such a great job.
"A witty saying proves nothing" Voltaire
http://jpsc.org.uk/forum/
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Sanzomat
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| posted on 7/9/22 at 05:53 PM |
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My pinto knowledge only comes form Cortinas and Sierras so a bit rusty but both used to run on. Ford fitted a solenoid operated valve (to let the
vacuum out of the inlet manifold when the ignition is turned off I think) to prevent the running on but they sometimes stuck closed and also may not
have been carried over to the kit so from my experience, yes, pintos running on is not uncommon. Can be a symptom of a coked up head though giving hot
spots of carbon that are hot enough to iginite the fuel without a spark. Can also by a symptom of general overheating.
I would have thought the electric fuel pump should definitely be wired to switch off when the ignition is off or it is likely to push fuel past the
float needles. Should be a low pressure pump for carbs but if it came from an injected car it could be too high pressure. If there is a fuel pressure
regulator that could be set too high too.
[Edited on 7/9/22 by Sanzomat]
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mark chandler
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| posted on 7/9/22 at 05:55 PM |
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Sounds like to much fuel pressure to me, the float bowls should never flood out! if the thacker washers are over tightened (the carbs should ‘float’
on the rubber ‘O’ rings) then they may dribble back a little at idle
Maybe not such a great job as above 
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JoelP
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| posted on 7/9/22 at 06:55 PM |
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Thanks guys. I'll look into it as soon as it stops raining! There is a fuel pressure gauge under the bonnet so I'll check that too.
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gremlin1234
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| posted on 7/9/22 at 08:13 PM |
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quote:
Originally posted by JoelP
Thanks guys. I'll look into it as soon as it stops raining! There is a fuel pressure gauge under the bonnet so I'll check that too.
I think for carbs it should be 2--7psi. aim for a little less than 4psi
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RedAvon
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| posted on 8/9/22 at 06:48 AM |
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Hi,
I have the 2L pinto on Webber 45s setup and with the fuel pump on, had petrol spewing out of the trumpets.
Although the car isn't on the road, I ran up the engine every six months. I see yours has not run on the road for a while.
I took the carbs apart and they were absolutely full of gum/varnish from old fuel which had blocked many passageways and made the mechanisms very
sticky due to me leaving the fuel in between start ups.
Might be worth popping the inspection cap off the top of the carb and looking in, and smelling, as it absolutely stinks!
Hope this helps.
Ian
Bricoleur
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nick205
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| posted on 8/9/22 at 07:19 AM |
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quote:
Originally posted by RedAvon
Hi,
I have the 2L pinto on Webber 45s setup and with the fuel pump on, had petrol spewing out of the trumpets.
Although the car isn't on the road, I ran up the engine every six months. I see yours has not run on the road for a while.
I took the carbs apart and they were absolutely full of gum/varnish from old fuel which had blocked many passageways and made the mechanisms very
sticky due to me leaving the fuel in between start ups.
Might be worth popping the inspection cap off the top of the carb and looking in, and smelling, as it absolutely stinks!
Hope this helps.
Ian
Echo Ian's comment here.
I had a Sierra 2.0 Pinto in my MK Indy with a Webber 32/36 DGV carb (manual choke). All ran well once I'd had the carb correctly setup (jetted)
for the engine. However if left with fuel in over the winter (not run for several months) the carb gummed up and the engine didn't want to start
or run properly. A strip down and clean with some isopropyl alchohol sorted it pretty quick and restored good function.
I was using the original Pinto mechanical fuel pump that came with the engine, not an electric one.
The engine never overan nor did the carb leak fuel though. When I got the carb I stripped it completely and rebuilt it with a Webber overhul kit of
new seals etc. Not expensive, just time consuming and needed some space to work cleanly and in order. Took plenty of photos as I dismantled and
reassembled to ensure I got things back in the right place/order.
BTW - did Bogg Brothers do any work on the carbs/engine while they had the car?
I've not used them myself, but heard the name mentioned on here a few times.
[Edited on 8/9/22 by nick205]
[Edited on 8/9/22 by nick205]
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JoelP
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| posted on 8/9/22 at 11:27 AM |
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Boggs Brothers have cleaned the entire fuel system, all new pipes and new pump too. I was pretty sure the carbs had been stripped too, but I'll
have to check with them I guess!
Thanks.
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Dingz
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| posted on 8/9/22 at 02:33 PM |
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Sounds like too high a fuel pressure overcoming the float needle valves, as suggested try 2-4 psi. The running on is probably the fan running
constantly, when you turn off the ignition the fan motor acts as a generator and provides enough current to keep the engine running. To test it turn
the fan off before the ignition. To cure it you need a diode in the fan circuit to stop any back feed. How do you know what temperature the engine is
running at? Gauges can be terrible liars at times, where and how are you measuring the temperature.
Phoned the local ramblers club today, but the bloke who answered just
went on and on.
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gremlin1234
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| posted on 8/9/22 at 03:14 PM |
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quote:
Originally posted by Dingz The running on is probably the fan running constantly, when you turn off the ignition the fan motor acts as a
generator and provides enough current to keep the engine running. To test it turn the fan off before the ignition. To cure it you need a diode in the
fan circuit to stop any back feed.
diode, or a relay
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JoelP
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| posted on 8/9/22 at 03:56 PM |
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Afternoon!
The gauge under the bonnet is steady at 2 psi, but the pump does keep clicking even once that's reached. Doesn't go over though, and in the
drive nothing leaked. Time will tell there I guess.
It was running so nice earlier though, hopefully I can work out the misfire.
Looking in the nose cone it's obvious what the problem is. The radiator is entirely obscured by the fan shroud, but totally open all the way
round. I'll try to block up around it I guess. There is an oil cooler too.
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adithorp
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| posted on 8/9/22 at 04:55 PM |
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In addition to cowling around the rad, what is the grill material? Expanded ally mesh, its doesn't flow sir very well. Try removing it (replace
with woven stainless mesh).
For the misfire; what are the plugs like? That'll give you a clue to the fueling. Also the fuel pressure guages on regulators have often turned
out to be giving false readings.
"A witty saying proves nothing" Voltaire
http://jpsc.org.uk/forum/
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JoelP
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| posted on 13/10/22 at 06:16 PM |
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It seems the misfires happens when you push 90mph for more than a few seconds. At 80 it's fine and still accelerates with gas. At 90 you push the
throttle and it just dies. You then have to back off for a bit whilst it recovers.
Can't quite work it out. Best guess would be not enough fuel coming through for prolonged max power - there's a swirl pot that would cover
brief bursts.
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SJ
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| posted on 14/10/22 at 01:19 PM |
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quote:
Originally posted by JoelP
It seems the misfires happens when you push 90mph for more than a few seconds. At 80 it's fine and still accelerates with gas. At 90 you push the
throttle and it just dies. You then have to back off for a bit whilst it recovers.
Can't quite work it out. Best guess would be not enough fuel coming through for prolonged max power - there's a swirl pot that would cover
brief bursts.
Seems strange to be speed related. what about if you drive uphill against the brake?
An AFR meter would help no end in diagnosing the issue. I used one to set up my Mikunis and it made it much easier.
Stu
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