So, can you replace electrolytic caps with polypropylene caps?
Sure, if you can find one with the same required properties, not just the basic value. And it fits in the same space, and you have money to spend.
OMG, that capacitor plague explains some issues I had around that time! First I’d ever heard of that debacle.
I’ve got the capacitance and the voltage rating. I hear there’s other properties, but how do I tell what’s important in a particular application? These other properties aren’t generally written on the side of the cap, are they?
You may see the temperature range on the can. Otherwise you need to look at the datasheet to know things like the service life, ripple current and resistance at high frequency etc. Replacement of an electrolytic for another one is pretty straight forward. If using a different type, then you may need to know something about the circuit it is operating in.
OK, OK, replace electrolytics with new electrolytics. Hopefully they’re made better today than during that plague.
The saga is still continuing - I replaced the module in the in the voltage regulator - car stared perfectly ,so I went down to my golf club for a few beers - approx 3 miles - when i left the car again started perfectly - but died after a mile or so. My son towed me home and I connected a spark plug ,which showed a good spark , but would still would not start !!!
Any further suggestions - if a fueling problem or an ECU problem ?
Thx
again
Gerald
Does the 3.6 have the same stinkin’ coax wire from the ign amp to the ECU in the trunk?
With 8CU - same thing as with v12 version.
With 9CU version - nope, the ECU is located in the passenger’s footwell under the bulky metal cover.
ECU located in the RH side of the boot ( Trunk ! ) next to the battery
Might as well check, then. I dunno where your Lucas AB14 amp is located, but there are two wires to the pickup in the distributor, two wires to the coil, one wire to the tach, and one to the EFI ECU. On the V12, the wire to the EFI ECU disappears into a harness in which it is the only wire for a while as it passes over the rear of the engine. The wire inside the harness is actually a very tiny coax. With engine heat it gets crispy and cracks, and the cracks cause the core to short out with the shield. Engine stops dead. Wiggling can sometimes get it going again. To check, find that wire and peel back the wrapping. If it looks good, OK, but if not you need to chop out that length of crispy wire and replace it – whether it’s your problem this week or not.
This was just how the problem started with my car. Are you near the
South coast in UK, I could lend you an ECU? The intermittent capacitor
that needed replacing was a metal film, not an electrolytic.
Jim 1984 XJS 3.6L cabriolet
Hi Jim, Thx for your offer,BUT I am in South Africa !! My car starts perfectly when it is cold and runs well for a few miles,till it warms up and then it will suddenly cuts out . When my car cuts out and won’t start and I pull a plug wire and connect a spare plug,I seem to have a good spark – makes me think that it must be a fuelling problem,although there is no spluttering – car just suddenly dies – one would think that there bwould be some misfiring before she cuts out !
My car is fitted with a DAC 3531 ECU and I have a spare one DAC 3831,but when I fit the spare,the car does not start
Rgds
Gerald.
Progress report - I ran the car in our garage until it stalled and would not start. I pulled a plug wire and connected a spare plug and got a good spark . I noticed quite a strong smell of petrol .After cranking for about a minute or two,she spluttered and started - give me an idea that she was flooding ( If over fueling would the engine just suddenly die,or would there first be black smoke and some spluttering and misfiring ,before it stalled ? )
Can a coolent sensor cause this problem and is the fuel delivery regulated by the ECU ?
Unfortunately,being in South Africa means that there are not many people around with the required Knowledge to work on the ECU. Is there a specific part/capacitor in the ECU that controls the fueling and can it be tested and replaced ?Thx again for everybody giving me advice
Gerald
Sorry,should have mentioned that I pulled a plug which did not seem to be wet with petrol,so this may knock my overfueling theory on its head !!
To answer the question regarding the coolant sensor, yes it can cause over fuelling but I would expect spluttering prior to it quitting as you do.
There are 2 types of 3.6 XJS injection systems, my 1984 uses vacuum to
determine fuelling. Later ones use mass flow sensors.
To run the vacuum sensor type needs the following:
1/ Fuel with the correct fuel pressure regulator.
2/ Power to the ECU, coil & injectors. Both fuses & ignition switches
have been known to fail.
3/ A coolant temperature sensor. Failures are known & you can take it
out the car and measure its resistance against temperature, leaving it
at 95C for a few hours while you check the resistance doesn’t change.
4/ Signal from the distributor. If this isn’t present it definitely
won’t run. Have you a scope to look at this?
5/ Vacuum to the sensor in the ECU. These sensors do fail.
As it stopped suddenly, it would seem to be electrical. So start with 2/
by measuring voltages on the coil. I found the intermittent fault (very
similar to yours) by heating parts of the ECU & saw the signal cut out.
Jim
Actually, quicker test: When the car dies, pull the connector off the coolant temp sensor and short the terminals in the harness connector together with a paper clip or something. If the car starts and runs, replace the coolant temperature sensor.
Morning Jim ,and thank you for taking the time to reply and try and help me. Mine is the vacuuim operated ECU – My query is this – when the engine stalls and won’t start – if I connect a spare plug to one of the plug wires and try and start the car,I find a strong spark,which surely must mean either no fuel,or overfueling ?
I will try Kirbert suggestion next time she cuts out,and short out the coolent sensor and see if it makes any diff.and if the car then starts.
Rgds
Gerald
Does in then start when you get a strong spark on the spare plug? I
wonder if your intermittent fault corrects itself, so it can start? I
think you have to get it in failure mode & then make measurements.
I remember that with my problem with the ECU, you could get an
occasional firing if you pump the accelerator as this puts a pulse of
fuel in (whilst running the starter. I traced this part of the circuit
ln the ECU, it is separate to the rest of the ECU.
As usual Kirby’s suggestion is good.
Jim
Morning Jim ,and thank you for taking the time to reply and try and help
me. Mine is the vacuum operated ECU – My query is this – when the engine
stalls and won’t start – if I connect a spare plug to one of the plug
wires and try and start the car,I find a strong spark,which surely must
mean either no fuel,or overfueling ?
I will try Kirbert suggestion next time she cuts out,and short out the
coolant sensor and see if it makes any diff.and if the car then starts.