XK120 engine test

I am ready to put my engine back in but want to start and test it first. I am not sure how to wire it up and don’t want to hurt anything by doing it wrong. Can someone tell me how to do it? I have a stand for the radiator, engine, oil and water gauges. I was thinking of using a small gas can mounted above the engine as gravity feed instead of using the fuel pump. Any help would be greatly appreciated.

white/black wire between CB side of coil and side of distributor
white wire between SW side of coil and a test toggle switch on the stand
white wire between test toggle switch and starting carb solenoid
black wire between starting carb solenoid and otter switch or ground on engine
large black cable between starter and solenoid RH terminal on stand
large black cable between solenoid LH terminal and battery negative
large red cable between battery positive and some ground point on engine
white wire between test switch on stand and battery negative
white/red wire between solenoid center small terminal and second test push button switch on stand
white/red wire between second test push button switch and battery negative

flip on the toggle switch and push the button switch and it should start
flip off the toggle switch and it should stop

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Gravity feed is OK. I used a lawn mower tank strapped to a step ladder. Make sure you crank it several times with the ignition OFF so as to get the oil circulating. You should see the oil gauge just start to pulsate.

Assuming the generator is not connected and you’re running straight from battery, you can run it as either positive or negative ground at this stage, but make sure you have the wires connected accordingly. If you do away with the ignition switch you can also do away with the solenoid at this stage and jump (heavy cable) directly to the starter motor with battery direct to coil. To stop it, (hopefully it started)- disconnect the wire.

Good Luck !

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I think @Nickolas has a video…:laughing:


Didn’t “Big Jim” in the U.K. run a preliminary engine test on his rebuilt XK140 engine prior to refit a year or so back, if memory serves? Should be in the archives somewhere I suspect.


I believe he did… a archive search will bring it up

Don’t yet know the backstory on this, but you may want to check with Jay Leno before proceeding

It wasn’t the first time it happened to Jay…

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It was one of my favorite episodes of Jay’s!

When I was a wee boy, one of my customers --actually my dad’s–had a Doble steam car and man, was I was fascinated with that!

so as to get the oil circulating
Pull the plugs to pump up some oil pressure may take a few seconds to register

Essentially yes, but may take several cranking cycles depending on the state of “prime” in your system incl. oil pump, filter etc. I wouldn’t run the starter for more than say 10-12 seconds each cycle without a break as it could overheat.

Here’s the link that CP120 was referring to… hopefully it links, if not search “Big Jim start up”


Sorry Jim - Mistakenly responded to you as the OP.

Directed to Bill M.

With plugs out you can crank longer. It can take a minute to build pressure…

Agree, but for clarity - don’t crank for a full minute (if your battery is even capable of that) or you will fry something - probs your starter . Break it down to several shorter cranks. you’ll see what we mean once you start. Common sense will prevail…

Beautiful. Thank you very much.

House keeping
blow the head off with compressed air before you pull the plugs so you don’t get any dust dirt etc sucked in

Cheers doesn’t matter :grinning:it’s the thought that counts