Hello everyone !!! First time I'm really stuck with my S1 after 15 years. When I have an issue I always manage to identify what is wrong. But this time I'm stuck : car starts and heats up : then as soon as the starter stops it shuts off like if it has no gas coming in.

What I did :

A, Carbs and fuel : I took apart the SU HD8, cleaned and changed all gaskets. No change. Floats are good, floats valves too. Checked the (recent) pumps. No issue. Fuel filter is absolutely clean. Changed the fuel hose just in case.... Still nothing.

B, Electrical : changed the plugs, changed the ignition coil (it dated back to the 90s...) and the platinum screws as well as the capacitor just in case. Old one showed no wear. Set at 0.4 as prescribed. Battery seems strong at 12.7V

Now, after all that im lost. What can it be? I see no vacuum leak, engine seems to have pressure.

How the car behaves : it starts and shuts about 10 seconds after the starter stops. After that first cold start : it starts and runs for 10 seconds. It dies like if fuel wasn't enough. However fuel is there !!!! Needles are fine and correctly positioned. Needle jet isn't worn. I've tried all settings to try to get it running.

Can someone help me? THANK YOU !!!!

 

Ignition switch or wire from it

rule it in or out. Jump 12v to coil +. crank up the engine. if it continues to run, you have the bad circuit identified.

If not, then look esewhere

Even if the fuel pump failed, the csarb bowls would ahve enough fuel to fire the engne for a lot longer than 10 seconds.

Good luck with the e;ectrickery!!

Crl

 

Hello, thank you for your response. Ignition switch really? I'd have that symptom of running out of fuel? OK, I'll check that to rule it out.

 

And a faulty ignition switch would allow the engine to run when cold? Mine runs when the starter is engaged. It dies after starter stops.

 

Cod is not involved. it is a switch issuel the coil gets juice when te sweitch is in the crank position. when released to the run position the coil gets no juice. hence the engine quits/

betcha beer that the jump worksin

 

So I just tried and also checked with a multimeter. Key in turned to activate the system : the coil reads 12.5. I crank : it starts and runs until the starter stops, then voltage drops at 5.8 and car dies. Next try : wire connected from the battery + to the coil +. Coils reads 12.5 of course. Car starts and dies immediately. No start after that. I hope I haven't fried my new coil...

An other observation : I had the gas pedal pressed while the car was running on the starter and I noticed it doesn't accelerate. Pedal feels dead and pistons don't lift up in the carbs. Like if there wasn't vacuum to pull them up. So I checked all vacuum hoses but all are fine.

REALLY LOST

 

I am not quite clear on what your exact problem is. You are saying that the car runs until the starter stops, but this seems unlikey as the engine will soon "overtake" the starter if it runs. Next you say it runs for about 10 seconds after the starter stops. You must isolate the problem to either fuel or spark. To eliminate fuel, put some fuel in a small squeeze bottle and run it into the manifold perhaps where the auxilliary carb enters, or into the carb bellmouth. Have an assistant start the car and if it starts keep feeding small amounts of fuel in. If the engine keeps running you have a carb/fuel problem. If not you have a spark problem and you are on the right track by connecting the battery directly to the coil. Next check the proper operation of the distributot with a timing light. Good luck.

 

Yea Im confused by the starter being engaged for 10 seconds with the engine running. Thats makes no sense.

 

Thank you for your responses. I know it's confusing ! That's why I'm here asking. As you can see in my post history I seldom come around the forum as in the 15 years I've owned that car I always figured issues myself without much difficulties. But as you say @brewtech it makes no sense :

When stone cold (so that can only be once a day) it starts like a charm as the starter kicks in. It dies when the starter quits. The 10 seconds is a figure of speach. To be exact it's less than that. Probably 4/5 and it dies.

Fuel is not the issue : pumps work great, and line is clean. Floats are set properly, float needle is good.

Distributor parts are new and I figure if it runs fine with the starter on it must not be the problem.

The faulty switch path makes sense really : but I couldn't keep the car running with the jump wire. But maybe did I do it wrong? Must I jump it after I started the car or before?

One thing I'd like to repeat and highlight is the fact that when it's running (only with the starter on) it won't accelerate. That isn't right. During the last start I had it started by an assistant to be near the engine, air filter off. When as asked my assistant to accelerate I could see both pistons staying still. Not moving up at all. COULD THAT BE THE ISSUE? Engine shuts off because it gets no air?

When the starter is on air goes directly to the manifold right? So it makes sense that once the starter device stops feeding air, if the pistons don't lift the engine quits.

@mekon : your 73 model has a diferent setup than mine for the carbs I think. You probably have the AED and I don't. See a picture of my bay for information

 

Better pictures of the SU HD8 setup...

About the starter : it stays on until the engine is warm enough. So that's about 2 minutes or so. And again : besides the fact I can't accelerate during that time engine runs great !

 

When you say "starter" - I now think you mean the starting carburettor device! And you have a manual switch to turn it on/off.
In that case it must be a fuel problem, or your switch is shorting something out.

And also your engine bay looks brilliant. Not many Jaguar cars of this vintage have clean engines.

 

I had an encounter with a friends 420 some years ago with similar problems.
I suspect you have a great big air leak into your engine inlet manifold.
Starting on the starter carby gives you a very rich mixture which combined with an air leak will allow the engine to run.
When you turn off the starter carby you now have an air leak with no fuel coming from the carbies because there is no air being drawn through them.
The first thing I would check is the vacuum hose/outlet to the power brake unit or the power brake unit itself for an air leak.
Another way is to allow the engine to run on the starter carby and use a length of flexible 6mm plastic hose with one end up to your ear and go around the inlet manifold and carbies listening for a hiss which is air being sucked in.
cheers

 

@Mekon, thanks for the kind comment on how the bay looks : rest is consitent with it. It's a very loved car. Yes : by starter I mean that device located between the carbs to heat up the car. I really don't think it's a fuel issue... I don't see how it could be given both pumps are good and all the way down to the jets pressure appears OK.

@Bill, I did suspect a vacuum leak so I changed both hoses (to the power brake and to that valve hooked at the center of the firewall). Both original hoses looked allright...

As for a leak in the manifold I have to investigate. But could it have happened from one day to the next? Because that's what happened. The car ran fine, and the next day it refused to run. Just like that.

 

Oh my lord! Now that the confusion is over. You have a fuel delivery issue.

 

Are there any flexible hoses from the base of the starting carby to the inlet manifold.? I have not owned a S2XJ6 for a few years but I do remember flexible pipes becoming dislodged in earlier cars.
I urge you to do the flexible plastic hose I mentioned earlier and look/listen for a major air leak

 

When you say "starter" are you meaning the electric motor that cranks the engine to start it, or the auxiliary carburetor that provides enrichment during starting and warmup?

 

Jagboi64
I believe previous posts have established that "starter" is referring to the auxiliary carburetor

 

Hi Bill, so I've started the car today and as usual it started fine when stone cold. No leaks at all to be heard on the intake manifold. After engine died I went to slightly pull the white plastic off the power brake and immediately I heard the succion sound of a well vacuumed unit. I think we can rule out the vacuum leak. Again : both hoses are new.

 

The "starter" (I don't know how else to call it) is indeed some sort of auxiliary carburetor placed in between the two HD8. I think it was only installed on '69 and early '70 models.

I don't have flexible hoses from the base of the starting carby to the inlet manifold : it's all brass.

 

About the failing switch idea : I can now say it isn't the case. I've tried several times to jump the coil but it never works. Whether I jump it ahead of the start or during the time the car runs with the starter auxiliary carb. And after the car dies it read 12.4 or so volts. So it has power. After all these attemps to start the car I must have fooled my new plugs... Tomorrow I'll brush them and keep investigating.