Lez,
You wrote:
it is noticeably hesitant at low revs
How low is "low revs"? The Idle Circuit feeds the engine up to the 3200 rpm transition point, then the Main Circuit takes over from there. If all the hesitation and rough running occurs below 3200 rpm, then the problem is most likely in the Idle Circuit. If any of that activity carries over to above 3200 rpm, then it also involves the Main Circuit, and is a broader problem.
Is the problem immediately apparent, right 'off idle', or does it kick in at some slightly higher rpm? In other words, is the accelerator pump a problem, or is it all Idle Circuit?
If it's Idle Circuit only, then I suspect you have some partially blocked Idle Jets, despite having inspected them and taking a shot at cleaning them.
You wrote:
Ive checked the jets - holes were all clear
Holding the jets up to a light (or the northern sky), looking through them, and seeing light doesn't mean they're clean. There can be enough varnish on the walls to effectively reduce the inside diameter and restrict fuel flow, and still pass enough light to seem bright. And a soak in a solvent may not be enough to clean out any varnish without some vigorous brushing action.
There are nozzle/ tip cleaners for oxy-acetylene welders (search eBay). It's a little (fits in your palm) flip case with a number of different diameter wires inside. Each wire is rough enough to 'chew' carbon out of a welder's nozzle... not exactly a 'file', but rough. Select the largest diameter that is still a free slip fit through a jet, then in a bath of solvent (carb cleaner, brake cleaner, lacquer thinner, etc), scrub the jet's bore.
I recommend that 'WITH SOME HESITATION', since rough steel wire can chew away at the brass bore, and enlarge it. You do NOT want to make the jet larger, you just want to clean it out. Proceed with care, and a delicate touch.
Similar but different (more safe)... Start with stranded electrical wire. Finer strands are better. Strip the insulation off of a 5" or so long length of wire, then twist the strands together into a bit of a 'rod'. If it's too large to fit into the jet's bore, then peal out a strand or two of wire, and twist it into a 'tight' rod again. When you get a good fit into the jet, scrub away. Copper is softer than brass, and the twisted copper 'rod' won't chew-up the brass jet.
Or, if you really don't want to mess with it, just buy a set of new replacement Idle Jets of the same size. Install them and take the car for a drive. If the problem is gone, you and 'clean' jets have solved the problem. If not, you just wasted money on jets... life goes on.
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Accelerator Pump -- It's effect is more temporary, and during initial acceleration. From your description, I get the impression that the rough running is more constant below a certain rpm (like maybe below the 3200 rpm transition speed). I'm not optimistic that messing with the Accelerator Pump will solve the more constant low speed problem... ie, slow cruise.
However, the Dellorto accel pump uses a rubber diaphragm, and the common failure mode is for the diaphragm to perforate or tear. In that case, it will be less effective a pumping fuel, and may result in a hesitation/ stumble on initial acceleration (but not steady cruising at slow speed).
MORE IMPORTANTLY, if the diaphragm perforates, it becomes a fuel leak source. In that case, poor running is less of a concern than burning the car to the ground. Never put-off checking (routine maintenance), or replacing the rubber diaphragm!
Turn the ignition switch to 'On', and let the fuel pump run until you hear it slow down, indicating the float bowls are full and the inlet valve is closed. Then let it run a bit longer just to 'pressurize things a bit before switching 'Off'.
Lean into the engine bay, and swipe your bare hand across the bottom of one 'CARB BODY'. Inspect your hand for any... even the slightest bit of petrol-wetness. Then repeat with the second carb body.
If either swipe returns even the SLIGHTEST BIT OF WET PETROL (ANY!!!) on your hand, then give the keys to your wife and tell her to hide them from you. Disconnect the battery (+) cable. Any fuel wetness indicates a pump's diaphragm has perforated, and is leaking. And gas leaks drip downward, and the distributor and starter (both 'sparky' things) are right below the carbs. Don't even think about re-connecting the battery cable until after you have rebuilt the two accelerator pumps to LEAK-FREE condition.
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If it's none of the above, then find something else. I know, the pressure is on. But you're there, we aren't. We can only react to what you tell us.
Later,
Tim Engel
05/17/2023, 2:54PM, Dave Everett, <daveeverett01@...> wrote:
If your Esprit has Dellorto carbs, there is a banjo pump on the bottom of each carb, a lever squirts raw fuel into the inlet, if you remove the carbs from the manifold and operate the lever by hand, you should get a squirt of fuel. If not, the banjo is punctured and may explain the performance issue.
Dave
05/17/2023, 1:38PM, lindsay mclair, lezmclair@... wrote:
Hi Tim,
I have twin Dellorto 45's.
I only use E5 fuel.
I use the car on a regular basis. It had a long run (well 100 mile round trip) about a week before this all started. It doesn't sit idle. I used it in the winter as well, so it is well used.
Cheers. Lez
p.s. It is a Federal car I imported into the UK in 2018.
Regards. Lez
05/17/2023, 5:36AM, lindsay mclair, lezmclair@... wrote:
Hi Guys. My 1977 Esprit S1 has been running fine for some time now. However, I jumped in it recently and it is noticeably hesitant at low revs.?Its happy at speeds over 50 mph with no problems. 70, 80 and 90 likewise. If I accelerate hard (away from the traffic lights for example) there's no problem. But if I'm just trundling along at 20-30 its like kangaroo petrol!! (if you know what I mean!) [not as bad but you get the idea!]
Ive checked the jets - holes were all clear, but I gave them a soak in some brake and clutch fluid and a blow with the airline anyway. Checked the float chambers for contaminates - they were fine.
Cleaned the filters so they are nice and clean. But still have the same problem. Checked the spark plugs, distributor - all seems ok.
What else can I try? Any ideas
