I have a 62 e that is suffering from what appears to be a fuel problem. It has been ongoing for years, and I'm yet to resolve. Need help! I have tinkered with it off and on, and to date have pulled and cleaned tank, replaced fuel line, and installed new fuel pump. Installed filter, changed float needles, also tried gross jet ball shut off, pulled carbs, cleaned and rebuilt, including new main jerseys and needles, replaced plugs, wires, distributor, tried electronic, and dual point.
extensively i have tried timing adjustments. Carb syncing, slow idle, and fast idle as stated in manual.

What it does id idle fine, starts fine,, runs perfect even under ecceleration in shop.. occasionally it pops during quick acceleration. However, on the road under load, its quick and pulls as it should up to about 2500 to 2800 rpm, then starts missing and falls flat on it face. Slowly the rpm increases, but with no power. I have had this car for 38 years and it always ran fast and fun, now frustrating.
hopefully a knowledgeable jag guy can help me, or point me at what im doing wrong.

 

Hi Coolbreaze,
Wow, you tried a lot of things! Maybe you already looked at it but I would check fuel pressure at idle, fast idle, under load, etc. Looking for any unusual behavior with fuel delivery. You mentioned trying different ignition systems. Is the cap and rotor also new? Not sure what is in the car now but I would remove electronic ignition.....it is hard to trouble shoot those and they can fail in unusual ways. If the problem goes away, you found the culprit. Did you change anything with valve timing, or replace any valve train parts? And lastly, I would do a compression check.....probably not an issue but it eliminates that as a factor.

Cheers,
Richard

 

First reaction: fuel delivery or timing out of whack.
To check the first: Get a suitable container and drop the hose into it. With ignition key turned one click, do a timed volume delivery check. I don’t have the spec at hand, but I trust you have no issues finding this. If delivery < spec check the entire run, especially the section under the car for kinks dents etc.

For the second: I trust you have a strobe light, if not get one from the usuals. Cheap...
Next you need to find the spec of your distributor. I think your’s probably has vacuum advance as well as the regular internal governing (retarding) weights in the distributor.
Get the whole thing setup and in idle make sure it’s correct (10 deg BTDC I think). Then run through the other checks... you may have to disconnect the vac advance. See workshop manual...
If timing is the issue, the distributor would be my first component to fully check...

good Xmas project !!! Have fun

 

Hi,
You have replaced a lot of parts and checked almost everything. I would recommend checking for vacuum leak, and the induction system for sucking in air.
Good luck.
Bill.

 

Stochiometric ratio for gasoline is 14:7:1. Stochiometric ratio for 10% ethanol fuel is 14:1:1. So an otherwise well running engine will lean out when you run modern fuel. This is particularly apparent in acceleration, because the enrichment mechanism doesn't account for oxygenated fuel. Temporarily replace the damper oil with something heavy, like 90wt gear oil. If that improves the situation, work backwards: 60w motorcycle oil, 10W-40, single weight 30W. Use the lightest oil that gives you good driveability.

 

Cool are you using a factory air cleaner or something else. From all you have done you are describing classic symptoms of an aftermarket air filter (or no filter) and the car going lean at higher revs.

 

Often misunderstood, a low restriction air filter has a similar effect as oxygenated fuel. Assuming the air cleaner is really less restrictive (which may be an unfounded claim in some cases), then it changes the rate at which pressure changes in the plenum. Unless there's been some other change to the engine, the A/F requirement remains the same and the response curve defined by the needle is fine. .At any given steady state, the carbs will still establish the standard air fuel ratio based on air mass, just as they should. So at stable cruise speed, the engine hum along as always. . But step on the pedal and the car will falter, because the pressure rise is faster than the SU's ability to provide acceleration enrichment. The needles affect only the algebra. To adjust the calculus, you have to change springs, damper oil or damper diameter, or monkey with the orifice diameters in the piston. These are the SU features that determine the acceleration enrichment and rate of change. The easiest to change is the damper oil. Changing the needles, as is often done, will change the A/F ratio across the entire performance range: the car will SEEM to run better, because it will finally be getting enough gas under heavy load. But it will be rich in steady cruise conditions, and will soot up over time..

 

Wow , thanks for the replies. They give me things to check. As an update to things I didn't mention. Im running a Mallory dual point now, but symptoms the same as they were with electronic or original. I also previously checked the fuel pressure with a digital pressure gage at idle, not running, or accelerating, but cant check it on the road, under the bonnet. I havent done a timed fuel mass test, but would be interested in that volume requirement.
I have unhooked the vacuum advance to time it at lower rpm so it wouldn't advance too much, all set for 10° BTC. I Tried adjusting it a degree or 2 either way from that also, as the actual mark is hard to determine, since the indicator was replaced. They are slotted and slide a bit either way.
I am using original air box, but it wasn't on for my tests, thats the first thing ill try. when I drove this car regularly, it didnt act this way with the air box intake off.. i have removed the vacuum air line and ran it without it hooked to anything besides vacuum advance.. i also checked it for leaks on the line and volume tank side, by pulling a vacuum,, then closing the valve to observe leak rate,, which it didnt have. Ill put the air box on, if that doesn't work, I'll try the damper oil next. I appreciate greatly the input, and if any other ideas pop up, please let me know.

 

Cool you need to take your engine to TDC which is simple on an XK engine with a dial indicator or even a dowel or screwdriver. Once you are sure you are at TDC reset the timing indicator making sure the harmonic damper has not slipped--some do after a lot of years. That will take the timing question out of play!

 

Thankyou Coventry, I tried it with screwdriver, but was unable to tell within 5° either way. But had son tending screwdriver as I rotated. I have many dial indicators, should have thought of that. Will give it a go soon. Might need to get extension for dial. Would be nice to know exactly, thus eliminating that component. Even a degree one way or another changes. Idle, mix, the performance already.

 

Just a thought (from someone who's not too clever mechanically!)
I had a problem with misfiring at higher revs. Tried everything, including all electrics (coil, dizzie cap, rotor arm etc)
I was running a normal dizzie but with an electronic module from SimonBBC. Hall effect thing a bit like pertronix I imagine.Spoke to them for advice. They asked about my plug/king leads. I explained they were new, copper ones. They said that was the problem, the copper leads set up interference with the electronic gizmo and that I needed a set of silicone leads. They sent me a set, problem solved. Never had a problem since.

 

I don't see that you mentioned replacing the ignition coil. That certainly could cause your problem and they are pretty cheap. Make sure you get the correct one for internal or external resistor, depending on what you are running. This also needs to be matched to the ignition system you are running, I believe Pertronix, and some other electronic systems require a internal ballast coil. Do I understand correctly that you have the same issue with air cleaners on or off? That would eliminate the possibility of an intake restriction. How about the exhaust? Does it sound normal and seem to flow freely? restricted exhaust could also cause your symptoms. A little hard to test on older cars, you would have to disconnect the exhaust in front of the muffler to test. If there is no problem in these areas, I would go back to fuel and temporarily install, as close to the carbs as possible, a fuel pressure gauge, on a long hose so it can be taped to the windshield while driving to determine, for certain, if there is a fuel supply problem.

 

Thanks again for the input. I am not running electronic ignition. I am running Mallory dual point that I went through. I have replaced could with new. No change. I also have installed fuel pressure gage online with carb feed, past filter. The pressure was right, if my memory serves, somewhere around 1 1/2, or 2#. Didnt change as I give it gas. Exhaust is ok also, I checked it, no apparent restrictions, seems easy flow. As stated,it pulls fine, high rpm achieved unless pulling car. At rest all good. I havent tried hooking up the air box yet. Its cold and snowy here. Need to drive it. As far as resistor, I'm running original I suspect. I replaced the condenser on the distributer with new, I had that problem on a boat one, acted exactly the same. Cant wait for a day I can test it with air box. Im hoping thats it.

 

Hi Coolbreaze,
I would suggest that you fine a shop with a dyne and exhaust gas analyzer and make a couple of runs. I will bet that your problem will be found quickly. My guess is that its either an ignition problem or vacuum leak.

 

Coolbreaze, I mentioned the HT lead and plug leads - are they copper or silicone? And if copper, do you run resistor plugs and caps? can have a big effect on ignition. Did on mine

 

Ok, weather finally nice enough to take for short drive. After hooking up original air box, the horrible lack of acceleration and missing at rpm went away. Its not quite where I think it should be, but the improvement was immediate and a wonderfull feeling. A few light tweaks should get the engine right. Thank you all for your support and help. I feel a bit stupid, but its worth it to hear the car purr closer to what it should.

 

Excellent---best wishes.