Daimler Double6;stalls when hot
 

Hello every one,
Concerns a Series III Daimler V12 1979;Stall when hot; restarts after cooling. The longer it cools, the longer I can drive . (Max was 7 miles)
I have read many other threads on the subject... but still have some questions .
I suspect Fuel pump related causes and also vapor lock. But also ampli temp problems etc.
I saw that when stalling, the motor comp. was very hot (althought coolant temp 85°C within specs). I felt the fuel cooler. I think it was not functioning and that can explain a vapor lock.
Few questions.
1- Is a fuel cooler Always functioning even is A/C is off (as I guess it should be).
2- Can one feel (by 'r fingers) the difference in temp. of fuel goiing in to the cooler and at the output of it or does one need to measure it? And what difference is expected?
3- Is there a way to proof the existence (or absence ) of vapor lock.
K.regards

PreHE V12 common issues are what you have already stated.

Vapour lock is almost unheard off in my time with these beasts.

The fuel cooler only works when the a/c is ON, and it only cools the return fuel to the tank/s, NOT the incoming fuel, That is why I always remove them, and have had no issues with fuel locks etc, even in our 45c++ summers.

The Opus ign amp, originally fitted in the V, just forward of the distributor, fails regularly with heat, and works again when cooled down. Quick test, carry a cold water bottle, drive until it stops, pour water over that amp, try it. If it fires up, you have a winner. There was a kit, a very long time ago, to remove that amp from the V and relocate it in a cooler place.

Most PreHE engines here have the Crane XR700 ign kit fitted, and mine were some of them, and never an issue after that install.

A tired fuel pump will cause issues, of course, but rarely heat related that I have had.

The Coolant Temp Sensor (CTS), located at the rear of the LH thermostat housing may be going flaky, and that will cause a temp related shut down.

Thanks for all info Grant!! I'll try to dynamically monitor fuel pressure and secondary waves with a Bitscope, for which I have made some primitive pickup probes and hope to get somewhere from there on.
As for the CTS. I wonder how a CTS can recover from heat damage, it is simply a NTC and I guess that, when it dies (probably its resitance augments and the ECU thinks: its cold out there, and enriches), it doesnt recovers, or have U experienced otherwise?

As for the ign. amp? You mention the distributor. I guess that by "ign.amp" you mean the unit with cooling fins on the radiator (as in the pict.) or have I misunderstood?
Is there an answer to post #1 question 3?
Do I also have to consider cylinderhead problems (curved? when hot)

If the "legend" for that drawing states Opus Amp, then that is it. The original Opus amp was installed in the V, just in front of the distributor, and aft of the a/c compressor.

Memory, haha.

The first relocation kits had a longer wiring loom, so the amp was relocated, and I think??? the sedans were refitted to the rad top panel, and the XJ-S to the rear of the engine bay wherever room allowed.

I doubt you will feel the temp diferences of the rails, depends how sensitive the finger tips are, mine are rubbish.

As for head, head gasket issues, I seriously doubt it. The V12 is STRONG, and the PreHE even more so. If a head gasket were gone, the coolant would be pumped out instantly. My PreHE has now topped 500000kms and is untouched.

There are many other things that can be an issue, but when we are talking heat related, then OK when cooled down, the first item for as long as I can remember is that Opus Amp. The top of the radiator is NOT a cool spot, granted, cooler than the V, but not much.

My V12's have the ignition amp, and other heat sensitive components, outside the engine bay totally.

Which components do you mean? And where have you installed them?

The CTS can go "flaky", thus giving a signal that the ECU cannot recognise, so it shuts the fuel pulse down. I believe the resistance breaks down at certain points along its scale. Replacements are about $20.

This is so with the HE. Unplug that CTS with an engine running and it stops with conviction, and memory AGAIN, I reckon my PreHE does the same, but its been a looooooong time, and the car is now with a collectror 12 hours away.

Simple test, run the engine, and unplug the CTS, and see what happens.

Wherever they will fit. Wires can be as long as your heart desires.

The PreHE XJ12 had the relays along the radiator support panel relocated to the area in FRONT of the LHF wheel, and a cover fabricated to protect them from stones etc.

Mine has the Crane kit (Opus trashed) and the amp for it is under the passengers seat inside the car.

The XJ-S HE has most of the sensitive stuff in the panel aperture aft of the RHF wheel, which is a sealed panel to the outside world. The ign amp is out the front of the radiator, next to the 2nd coil.

Basically I used my imagination, and I have good imagination, and relocated one item at a time, until it looked better than it did, and opened up so much extra room.

I have already done this because I wondered if I had a lean condition and wanted to fool the ECU and the result was. Stalled immediately. I Think the ECU doesn not accept resistances much larger than 6Kohm...

Good tinking! I suppose you did it after having trouble with the Opus? As for the fantasy... I could guess it admiring yr avatar... unless it isnt fantasy this time of coarse....:icon_handball::icon_handball:

Yep, the Opus was playing up. I worked for Jaguar at the time, and simply ditched it on both PreHE cars.

All my Jags have always been daily drivers. meaning they had to run, and run correctly. School runs, work (both of us) etc etc.

I simply altered whatever I knew/thought could be an issue, and this was all pre computer days, so imagination and common sense was a daily part of life.

Some things still went hissy, so I kept records of what I did and what I used. That library is HUGE, and is slowly being computerised.

?Avatar, maaaaate, a gentleman never tells tales.

Goodo, that is now eliminated mostly from the equation.

I dont remember the PreHE, but on the HE, bridging that plug with a paper clip "tricked" the ECU to "normal" operating temps, or close enough. Worth a try to 100% eliminate that CTS. If it runs longer with that bridge, maybe the CTS is flaky at specific temps.

Thats certainly worth trying! You 'll hear from me.

Remember, here in Europe we are walking on yr feet...







May I ask how you (will) realise that? A kind of a knwoledge base?:icon_couchhide:

I just read about bleeding the coolant system. I remember when I bought the car, there was to little coolant in it. I guess normally they should have bleeded it because I think it was really low.
What is in fact the advised level to fill it to and
2/ is it possible that the motor stalls as soon as temp. goes >85°C because of air in the cooling system and if so, which mechanism would cause the stalling? Just by being to lean or other things?

I just discovered that after 5 h "driving" (in my case searching for the cause of the hot stall problem, so mostly idling), I had to add 2L of coolant. Before that, it was topped and bleeded. Temperature was never higher than 90°C. No water was expulsed. A few drops on both exhausts.
I am planning to a compression and leakdown test. Is it for both necessary to do it with a hot motor??
Is it possible that a motor stalls when hot because of a gasket leak or do I have to solve the "hot stall problem" first, always adding coolant?