New (to me) '70 E-Type 2+2 with perhaps odd vaccum and wierd plusing lights!

Hello folks - I just bought my 1970 E-Type and there are a few issues I need to correct. I’ve ordered some books and such, but I did a little diagnosis in the meantime, and wanted to run a few things past you all for feedback.

Issue 1 - This car doesn’t suck …no really…no vacuum?

The primary issue I am investigating is a miss at idle - worse when cold, better warm, but never completely clears. I actually drove home with the choke out slightly to keep the revs a little higher - seems to take a very long time to get warm, though as I said, the miss never clears completely. I checked spark and all wires are receiving good, strong steady spark, so I moved onto vacuum and encountered and odd thing that may be normal for these cars, or maybe not, so I thought I’d check:

  1. I tested vacuum coming from the front stromberg carburetor, the line that typically goes to the vacuum can on the distributor (vacuum retard on these cars, if I recall) . I only got 2 - 3 HG vacuum however - seemed really low to me. What should the vacuum reading be off the carburetor? and is it ported or manifold vacuum? As this is emissions, I suspect ported.

  2. There is a metal line that starts at each carburetor, runs along the passenger cam cover and connects to the head at the front - (Crankcase ventilation / precursor to PCV valve I suspect). This line then continues out of the “cap” on the other side, follows the driver’s side cam cover and eventually connects to a canister behind the battery, adjacent to the brake vacuum booster. This line had no vacuum at all. The line is broken before it gets to the canister beside the brake booster, and has no vacuum signal at all. I expected there to be a vacuum signal from the carburetors, to draw / ventilate the crankcase and draw the fumes back into the carb to get “reprocessed” - but nothing.

The brakes work very well however, so the car is making vacuum, but I’m not sure what to make of the lack of vacuum from the carburetors.

Issue 2 - The hypnotic pulsing lights

This, I think, is a alternator problem. The symptoms are these:

a) With the lights on, and any lights - dash light, map light, headlight, running lights - all of them, the lights pulse - brighter and dimmer, and do so in time with a noise seeming to come from the alternator. Increased RPM does not make the problem go away - they may occur faster, but still present. In addition, the more electrical load you add, the slower the pulses. So, for example, if I have just the map light on, and watch it get brighter and dimmer, I can flip on the headlights and the pulse will slow.

b) The alternator seems to make noise - either that or its something in the direct vicinity, such as a tension pulley. The nose is in time with the “light pulses” and I noted a deviation the alternator drive belt at the same time - it seems to be looser for a a fraction of a second.

My thought is that perhaps the alternator is increasing and decreasing output every other second - thus creating and releasing drag - so that would explain the belt and the pulsing lights. Similarly the noise might be when the alternator is under greater load. My second thought was a bearing in the alternator might be on its way out, and so its causing a noise and uneven drag. I also thought perhaps the voltage regulator could be at fault, but with a quick look I wasn’t able to locate it - I’ll look again tomorrow.

Would appreciate thoughts on these from you experienced owners. I have some familiarity with the MK2 and quite a bit working with U.S. engines, but the 4.2 emissions-laden XK is new territory for me.



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Hello Allan,
Search the archives for “70 XKE Tank Vent” and you will find a useful string with several diagram links and a complete explanation of the emissions controls on your car, courtesy of the Coventry Foundation.

Good luck and enjoy your car!

The vacuum source on the front carburetor is only for the distributor. It is modulated and not useful for diagnostic purposes. If you have to measure vacuum pull off the small hose at the back of the manifold and use that nipple. I would suggest you pull your spark plugs and note their condition. Then do a compression test. When is the last time your carburetors were worked on? It might be Time to rebuild synchronize and adjust them.

Will do - thanks for the tip.

OK - I suspected that may be the case, regarding the vacuum for diagnostic purposes.

I only got the car 4 days ago, so I have to go off of records and what the prior owner tells me, but apparently the carburetors were rebuilt - perhaps twice, including replacement of some linkage rod bushings as recently as this past year. Compression test is up next for sure, and even though I’m told ( and records support) a recent tune - I have ordered new plugs, wires, distributor, alternator, coil and a few hoses. It may be overkill given that it might just be a bad plug - but I like to start with a solid baseline and the more I examine the car, the more I believe whatever mechanic did the work, didn’t necessarily know exactly what they were doing. As a simple example, there is a metric ton of silicon gasket maker on the inside and outside of the cam covers - looks horrid - so I’ve got new gaskets coming as well. I also think the chain rattles a bit on start-up - I’ll check that when I have the cam covers off.


First off, to diagnose rotating noise, begin by removing all the belts. Yes, the engine will overheat eventually if you run it this way, but you don’t have to run it but a few seconds to determine whether the noise is present. Then add the belts one by one…so first, the water pump, then alternator, and finally a/c and p/s if so equipped

The pulstating lights suggest a problem with the alternator rotor…maybe a bad brush, dirty commutator or a bad rotor. Alternator noise may be a bearing or the alternator fan.

If you suspect a vacuum leak, disconnect the brake vacuum connection on the right inlet manifold. First plug the nipple to see if the miss goes away. If it does, then the vacuum leak is in the brake system. Otherwise, it’s in the manifold. To isolate a vacuum leak in the carbs or manifold, get a can of brake cleaner and spray it around the gaskets, spindles, and carb screws while the engine is running. You’ll know when you’re spraying the leak if the idle speed changes.

One way to tell if a miss is a lean condition, is while it’s missing, pull on the choke. If it stops missing it’s likely a carburetor adjustment. Or possibly an air leak at the manifold someplace. leaks can be found with propane or other gas, do a Google search on how to find manifold leaks

A loose alternator pulley may cause the pulsing and noise as may a loose alternator belt.
An open alternator diode may cause the pulsing and noise.

@ Michael_Frank, WWayman, Tommd55:

Thanks for the feedback. I’m headed to the garage to see what I can see, and I’ll apply the thoughts and ideas here - see what I find.

One thing I’ve found so far…that bonnet opening seems great…until you have to actually work on the front half of the engine.

You can get a little more working room by putting the front wheels up on something solid. Then undo the bonnet stay (if so equipped). That allows the bonnet to swing up vertical. Even so, the E-Type engine bay proves the phrase “so near, yet so far.”

Oh, I meant to say to use carb cleaner, not brake cleaner.

Evening folks - back with an update.

The Miss

So following the old “spray some carb cleaner” trick, as mentioned by @Michael_Frank, I did indeed find a vacuum leak, or perhaps better stated, an open vacuum source - see below:

So there was just nothing on that vacuum port! I put a plug on it and the idle got much better. There is still a noticeable miss, less so now at higher RPM, but still present at idle (8 - 15k range), so we’re not completely out of the woods yet, but it is much improved.

I also think I got an idle reaction from the carb cleaner around the throttle shaft of the rearmost carburetor, maybe the spacer as well, but not nearly as noticeable. So overall improved, but not yet fixed. Incidentally - what is supposed to go on that vacuum port? There is no line or anything adjacent that looked like it needed a home.

The Noise

As suggested by @Michael_Frank and also @Tommd55, I took a close look at the alternator and removed the belt. First thing I noticed was the alternator really wasn’t tight - you could move it by hand. So to the point made by @Tommd55, the belt was certainly loose. I ran the car with no belt on the alternator and the sound I was hearing (one of them) was gone. I reattached the belt - tight this time, and the light pulse seems to be gone. The sound did not return immediately, but it may have returned somewhat - so jury is still out on whether the alt needs to go, but the symptoms appear resolved, more to come once I can hear the Alternator sound over the other racket made by…

The Water Pump

One of the things I noticed upon removal of the alternator belt, is that there is some play in the water pump pulley. Its hard to say how much one can move it laterally, but the point is you can move it, and you shouldn’t really be able to do that at all. Second to that, I noticed a coolant drip that appears to come from the water pump pulley and drips onto the crank pulley. I observed this twice after start / cool down / start cycles and was able to actually see a drip fall by wiggling the water pump pulley. The volume of coolant leaking is, at most, three or four drops, but between that and the lateral movement, I think a new water pump is in order. I also think the water pump may be creating the rattly noise I can hear toward the front of the engine, it could be the chain, but sounds more mechanically hard to me. You can see / listen to a video here: (sound is most obvious at time index 0.27 onward). Naturally there could be many causes, but since the water pump needs changed anyway, I’m blaming it for the moment, and we’ll see how or if the noise improves.

The Compression Test

As noted by @WWayman, checking plug condition and compression test were on the list for today, and while the water pump was a bit of a downer, the compression test and plug condition restored some joy in the day, see below:

I’ve rarely seen more than 165 PSI even on a rebuilt engine, and so although these figures may or may not be less than achievable by a 9:1 compression engine, I was nevertheless well pleased. All values seem perfectly acceptable in my experience, and as far as a compression test can, they provide support for a generally healthy engine. A 6% deviation between highest and lowest values, overall average of 156 PSI seems well within the range of good to excellent, and the car does have 71,000 miles. I was using an analogue gauge and testing by myself, so its likely actual figures were 1 - 3 PSI higher had they been read immediately, versus after the few seconds it takes me to unfold myself from the driver’s seat and go check. In most cases I had an eye on the gauge, but not well enough to read precise results until I got out.

The plugs themselves all looked clean, generally consistent, and perhaps even a little too hot of a plug (these are Champion N12YC plugs, which are slightly hotter than the recommended N11YC). Gaps were a little varied but were between .025 and .032.

Next steps:

So I’ve ordered a water pump, and will take the opportunity to replace all the coolant hoses - upper and lower radiator hoses are cracked anyway and so were on the list already. I also ordered new belts - though seemingly nobody has any idea (including XKs) what belt is needed for P/S - so I guess I’ll measure it and go match one at the store. I also plan to check chain tension - its hard to hear over the other noise, but I think I hear the classic sound of a chain needing adjustment, and while I am there I’ll check the tappet cups and replace the “metric ton of silicon” with proper cam cover gaskets.

Point of note - as noted by @WWayman, the carbs may need help. Just for fun, I compared the lift on the pistons in each carb - the rearmost piston lifts with virtually no resistance, while the front has definite cushion from the oil in the damper, and has much greater feedback. If these were SU carbs, I;d know what to do already, but I’ve never worked with Strombergs, so I’ll need to read-up…but point is, they need adjusted.

That nipple without a vacuum hose was for the intake heat system. It went to a vacuum temp valve in the center of the air cleaner and then from the valve to the vacuum motor that controls the flapper in the intake snout. It mixes heated air from the exhaust oven with cold air to maintain a temp to the carbs.

In addition to the JL archives, this is a great site for Stromberg info -


My experience is the hollow floats in the ZS carbs can be prone to leak and start sinking. Float needle can stick too. Some of the usuals sell solid type floats. Mixture needles on my '68 were fixed so not much to adjust accept the float levels in those. Later ZS carbs had adjustable needles but I do not know when those were introduced. I got a set of adjustable piston/needle assys from the later style and dropped them into my carbs so I could easily adjust mixture. Joe Curto sells adjustable jets that should accomplish the same thing. I think most folks use his if they are going to convert from the fixed needle set up. If my car starts missing the first thing I check for is sinking or sticking float and next is to check for vacuum leak at any joint, seal, hose, gasket where air could get to the intake without going thru the carbs. My 2 cents.

68 E-type FHC

Morning -

So I’m familiar with the intake snout flapper, but I’ll need to open up the air cleaner off to check out this temp valve, make sure its still there and working. I’ve never been a fan of the varied gadgets used to heat and or control intake air on automobiles - not sure I’ve ever come across one I didn’t ultimately eliminate - usually because I had to use an aftermarket intake or air cleaner. BUT…if its useful, working and serves a purpose I’ll give it a go. I am chasing a vacuum leak though, so I may wait to hook it back up.

Thanks to @ryaskovic and @D_Barnes RE: Stromberg tips and links. I hate to bash things I really don’t know much about and heck, I’ve only just got the car, but the more I read on these Stromberg carbs, the more I feel like I will hate them with the passion of a thousand suns…non-adjustable jets, rubber diaphragms that split, multiple air leak systems (that become uncontrolled vacuum leaks when they fail). Even if you can adjust the mix, you can only do so with the engine off (makes it hard to tune with RPM or vacuum I would think) and whats this about two sets of butterfly valves? Insanity I tell you…insanity! :wink:

Like I said I do not know when Jaguar started putting the the adjustable needle type ZS on the cars. I have seen them on Series 3 but do not know about Series 2. Once I put adjustable needle/pistons on mine I was able to adjust the mixture with the engine running. Also it is easy to block open or remove the secondary butterflies. I removed mine soon after I got my car and improved the throttle response dramatically for me. Lots of discussions about this. Search for “five minute Strangleberg fix” and you will see lots of info. I no longer mind having ZS carbs especially when I considered the cost and trouble of making the swap to the 3 SU’s. My 2 cents

68 E-type FHC

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Well, I’ve no plans to replace the Strombergs, but it does seem alien to have carburetors where you cannot adjust the A/F mixture. Such an adjustment is part of the science of tuning your car, or at least it has been for me on all cars until this one. I did read somewhere that you technically can “adjust” the mix by setting the needle deeper into its mount hole in the piston - this will richen up the mix, but its not exactly “precise”.

I read the whole “5 minute fix” thread and having looked at the car, I think I’ll go ahead with that mod. General consensus seems to be that you’ll get 80 -90% of the gain (though some seem to argue there is none) by just jamming the secondaries open, as opposed to trying to remove the plates and or shaft. I like that because its fast, easy and reversible if need-be. However, if I find my secondary shafts are leaking air, I may go ahead with full removal since it’ll give me a good excuse to seal them up. HOWEVER… I must not get too far ahead of myself - Fix the water pump first - the noise is loud and obnoxious and unhealthy sounding - so I need to correct that and determine whether the water pump is the cause, or if its something else - the radiator hoses are also badly cracked, so good timing all around.

I do hate taking the car down when I just got it and have only driven it twice, but the hoses really can’t wait and I worry that the noise could become a catastrophic event if whatever it is that’s making it, explodes at 50 MPH. SO…better off just getting stuck in with some repair.

Just a quick follow-up.

I confirmed today that the water pump is the cause of the horrid rattling. With all belts off, the car sounded much healthier, with only a slight exhaust leak and the usual XK noises. The pump pully can be shifted in / out, side to side, back and forth - not by inches, but certainly enough to be well on its way out, and I confirmed its leaking. I also found metal (steel) particles in the coolant overflow tank, so I hope damage has been confined to the pump itself.

Not the end of the world, although your disappointment is palpable. Pump and hoses are a one day project, once the parts arrive. You’ll still have time for a few nice drives before winter hits. Since you have filings in the coolant, you will need a thorough flush. And you might do well to add a Gano filter to the upper radiator hose.

I’m looking at it as a positive. First-off, hoses needed done anyway and this gives me a good reason to get all the coolant lines refreshed. Second, when you consider the varied possibilities for an unspecified “engine rattle / grinding nose” an easy(ish) to replace water pump is by far the better of the options. This has also prompted good sense in replacing all the belts and will add to the confidence I have in taking the car for my 3hr round trip commute to work.

So often you chase an issue forever trying to pin down the cause, at least this one is, quite literally, front and center.

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