Hello All
Thank you for all your suggestions on my post ,re no power to fuel pump after a while
Followed all advices given ,replaced both relays also to be sure
I am fortunate that I own a road test simulator and am able to road test the vehicle in the safety of my workshop .
After a thorough road test simulation last Saturday I would turn off engine at differing temperatures until I could re create the fault
After approx a good 3/4 hr of hard driving ,had the fans cycling on and off ,temp guage reading 1/2 ,i turned off engine and then tried to re start ,
No fuel pump operation audible on ignition key turn and tested no power to start relay plug ?
Keep in mind I went over all ignition items involved in the start up process again and all checked out correct
I decided to strip back the wiring harness at both the fuel pump and start relays to trace the wiring
I found on another Jag Forum someone suggesting to check the connection of the fusible link wires on the positive battery cable ,sure enough I found an interesting sight
Both the two positive wires have a plastic sheath over the terminals and the plastic protrudes approx 2mm past the female terminal
I cut the excess plastic back to the terminal ,re inserted both wires onto their male ends and had power and fuel pump operation and the engine started
Now I am waiting on a replacement Accellerator potentiometer to create the stutter the vehicle owner originally had reported to me
Will let you all know how it all goes ,again cheers to every one ,that is what I like about these groups
Two very interesting pieces of information in your postā¦^
I recently saw a six wheel road test simulator for sale from a local authority rescue divisionā¦never usedā¦
I guess Iāll just have to stick to the one for my push-bike.
Hello All
Received a good used Acc potentiometer , on Mon 11/03/24 and installed it.
Turned Ignition key on ,fuel pump primed up and Engine started instantly and idled
steady ,a few quick snaps of the throttle wheel and no stutter or dead stops engine sounded nice
As it was late in the day I decided to do a couple of laps around the block and the car run beautifully I was even starting to think I may had a win finally with the little red horror ,driving around for approx 20 minutes I began to taste the beer I had waiting in the Fridge (it was 34 deg C and very Humid)
Had to turn engine off to move a couple of cars into the workshop ,took about 10 minutes
Got in Jag and turned key and no fuel pump noise happening and engine cranks but wont start ,tried several times no go ,so fault I am chasing is still there
I had an off sider help me tow car in to workshop to attack in morning
Quick up date ,went to car this morning ,turned key and fuel pump primed up and engine started up and run very nicely
Any ideas would be welcome
Cheers
I tu
Next time it happens check if the ECU gives 12v to the fuel pump relay and if the relay activates.
Also check if the fuel pump runs when you power it directly with 12v.
Rig up a set of test lamps to monitor each +12v point and the pump Gnd.
Leave the lamps in a prominent position in the cabin.
Next time the car plays up one, or more lamps will fail to illuminate.
Question: Would it be practical to build a test panel with12, to however many 12V test lamps one wants, to use for testing the various components. Things such as, just to name one, are all the injectors firing properly? The 12 connected test lamps would all be flickering/blinking in the same pattern, any test light not following that pattern would represent an injector that is not firing properly?
For the injectors not that necessary, you can hear them clicking anyway.
For the rest it could be a great troubleshooting tool.
I did somewhat the same, Iāve put LEDs in most of the relays (primary circuit).
In a glance you can see what is happening.
If you have the time to build such a diagnostic panel it could be very useful for diagnosing intermittent faults, but the Ecu should be recording such faults anyway.
Injectors tend to either work, or not, but such diagnostic lamps are available: Noid lamps.
What the ECU probably cant record is failure in the power supply to the pump, which is the fault in this case, hence monitoring all the power and Gnd supplies required to make the pump function would be useful.
Alternatively install data loggers for each supply point.
I was going to suggest the same thing.
When I had an 85 with the 6CU ECU, it had very similar symptoms. In the end it was a faulty fuel pump control circuit in the ECU. I believe I temporarily solved it by running my own ignition controlled wire to the fuel pump relay.
You can listen to them individually, however, even if your hearing is able to hear them all clicking while standing over them, you wouldnāt know which one wasnāt working properly in its sequence.
Watching 12 lights, you could likely see the one(s) not in rhythm with the others.
Excellent idea with the LEDs in the relays. But I was thinking of having a test light panel which could be set somewhere when testing which grouped the lights together for convenience.
However, a light connected to that circuit could show an issue (if the issue occurred while testing, such as the light flickering?).
I was thinking of keeping it simple for test purposes while testing thingd. Maybe it wouldnāt be āthat simpleā?
Your thinking is absolutely correctā¦keep it simple.
Just remember to use incandescent test lamps as LEDās donāt load the circuit so will still illuminate even if only a very low current is allowed to pass.
You canāt sense electricity, so convert it into something you can.
Hello To All that Responded
Appreciate all the advice and same very original ideas ,here is where I am up to at this stage
After replacing Throttle Pot ,engine stutter and no Throttle response ,appears sorted
The other issue of not been able to re start after running engine a while ,I think may have found culprit part ,with the various areas I have under test
(1) Fuel pressure gauge ,found pressure on initial KOEO ,goes up to 39psi and interestingly slowly drops down to 4psi ,and KOER ,steady at healthy ,36psi and have power at fuel pump.
(2) Have Noid light on 1A injector and a healthy pulse evident when engine wont start
(3) The most interesting I have found to date is that testing coil;spark into a coil test unit when the fault occurs ,is that the spark is a very light blue and very weak ?
(Note) The vehicle has been converted from the original 2 coil type to a single Ducellior transformer coil at same stage as the original front coil; was still in place but not wired up
As I did not have the same coli available for my testing I set up a Bosch Coil suited for D.jetronic system
The engine was started and ran ,(in workshop only ) until fan come on and engine switched off and fuel pressure allowed to drop to 4 psi and then Ignition key turned to on and fuel pressure rose immediately to 39 psi and engine started up OK .
This I repeated several times and each time after the same steps as outlined the engine would re start ok
Now will order in correct type transformer coil or equivalent before I attempt longer test drive on my Simulator (I am told that the wrong coil type can damage the Ignition Amplifier)
Will let you all know the outcome
Cheers to all
Something else I discovered whilst looking at a wiring diagram was the location of the two relays in the fuel pump circuit (in the boot)
The relay marked with a Red line (Diode) was fitted to the fuel pump black connector and the normal relay was in the Red plug ,(main relay) ,not sure of what that may have done or can do ,?
I have swapped them around for now and am awaiting replacement Diode type relay in case of damage
Also whilst looking around in the boot area ,I noticed the ECU has an old type string /paper tag with the car dealers name (from Canberra Australia) hand written on it, interesting?
The vehicleās history is a little unknown as it was bought at an Auction in Canberra Australia ,but am told it was in a shed for many years on the NSW South Coast in a little seaside village only 1/2 hour from where I actually live !
Cheers
The diode is to stop starter signal back Emf from the relay triggering the Ecu start recognition. Not your issue.
I have known a coil wired back to front cause an issue of cutting out after a short drive. The coil was overheating so failed to deliver spark, after it cooled down it worked again.
Afaik, there should be a non return valve in the fuel supply, so pressure shouldnāt drop after switch off, to stop vapour locking causing hard starting, but as long as you have full pressure when the pump is running the engine should stay running.