Jaguar Repair: E Type FNC 4.2 /1969, vacuum gauge, co hc

Question
Hi, Last weekend I drove the car and suddenly the engine during the rit stopped I accelerated and the car went on going good.Then I parked the car and after one our I started and every thing seemed to be ok but after 300 mtrs the engine did not run well I came home with a sputtering engine [ca. 20 km]Next morning engine starts but only idels as soon as I push the accelerator it stops or works with backfire in the exhaust and carb[2xstromberg]I checked the ignitionpoints and placed a new petrolfilter also in the petroltank I also tried an other coil.The problem is stil there [ I Live in Holland sorry for my bad english ]I hope you can help me.2 M.Dijkstra

Answer
Hi Meindert,

In the Jaguar dealerships we had good test equipment like a scope and CO/HC test equipment but most people don't have that equipment. So you need to test with other methods.

All engines require the same things to run and that is only three items. (with conditions on each of the three)

Compression, fire and fuel.

Compression will not usually come and go. When it is bad, it usually stays bad so we can skip this item for now.

Fire (Spark), can do what you have but less likely so even though spark should be checked before fuel you can put that aside for now also.

If you can get it into the mode where it idles but you can't open the throttles, this is a good condition to run a simple test. Get a spray can of "Starting Fluid". It should be available at any auto parts store there as it is here.

Just as you try to open the throttles, spray a little starting fluid into the air filter intake.
If you can get the engine to rev up using starting fluid and not without it then you have proved it is a fuel problem.

If this does not make it rev up ok you need to first connect a vacuum gauge to the intake manifold and slowly start it open the throttles and watch vacuum. If vacuum goes away before the engine cuts out you need to loosen the exhaust at the exhaust manifold so you have a gap between the pipes and the manifolds. Then start the engine and see if it will rev up and if it does you have a partially stopped up exhaust system. If it revs up with starting fluid it is for sure a fuel problem and you need to continue.

To establish what in the fuel system is at fault you must start at fuel supply and put a fuel pressure gauge on the fuel line just before the carburetors. You want to see about 3 PSI.
If you have that, next is check the top pots for oil supply by unscrewing the caps and lift them up a short distance and push them down. If you feel hydraulic resistance they had enough oil in them, if not put a little engine oil in the top until you can feel resistance when pushing the cap down, then test run the engine. If it still does not run without the starting fluid spray,
If you have hoses connected to the float chamber vent pipes remove them for test purposes and try to run the engine without the hoses connected.

Remove the tops of the Stromberg carbs and inspect the rubber diaphragms for any damage. If they are ok look at the metering needles for any obvious damage. If all that is ok you need to remove both carburetors and check the floats, float level and float needles and seats and look for water or trash in the bottom of the float chambers. Be careful not to dump the fuel out when taking the carburetors off and dump the fuel into a clean pan so you can inspect for water in the fuel or trash.

Somewhere in all of this you should find the problem. Let me know.

Howard