It was my understanding that you need to depress the pedal with the key on to pulse the injectors. If I dry start my car it takes several cranks to start. If I turn the key to on and put the pedal down 3/4 one cycle then release it the car starts one crank of the starter.

 

im not getting any pulse at injectors.
I have 12.45v at wire from ign amp to ecu.and intermittent v at tpsthis car needs a 100' cliff

 

im not getting any pulse at injectors.
I have 12.45v at wire from ign amp to ecu.and intermittent v at tpsthis car needs a 100' cliff

 

sometimes my tps has all normal voltage,with ign on.and sometimes if I turn ign off and back on again it doesnt.it will go to 0 volts on both y and r wires of tps.especially if I leave ign on without starting eng longer than than 3min.

 

We are here.

I am currently into a 6 day 12 hours a day stretch, so sleep is paramount for this OLD brain/body, trust me.

If you got squirts at ign ON, and NO pedal activity, you got short circuits, and they could be anywhere.

YES, if teh ECU is unplugged, and the resistor is unplugged, and you got an earth path that is NOT a designated earth wire, you got shorts in that loom, and it travels inside the car to the boot.

Does this car have an aftermarket alarm/imobiliser/whatever fitted. Something is timing out the ign signal, and that year Jag is simply NOT that clever.

OR, the electrical section of the ignition switch is having an age related hissy, and I believe that was touched on way back in page #2 or so, but dont quote me.

If that TPS voltage is NOT stable 100% of the time, you got short circuits somewhere.

Not trying to scare you, but my Red Devil had issues, and I unplugged the loom at the bulkhead connectors, hung it up in the shed roof, and started all over, making a new loom, and simplified the arrangement to MY liking waaaay back in 1995.

Then Sir Arthur (In my garage) starting getting hissy (jealous) so I did the same to him.

My loom/s INSIDE the car/s was 100%, so only the engine bay needed help.

NEVER touched a wire on either car since.

 

Ya this car is driving me bonkers! No aftermarket alarm that I know of..
Im just glad its not my daily driver..lol
I bypassed that wire from power resister to ecu,and nothibg is grounding now..car is starting but running ruff.and then dies.I think its only running on the A bank. Im going to check all connections and wires that associate with that bank.
Im getting some strange readings at ecu,when I check wires there.at different times.Ill do another cleanning of ecu plug and connector.
thanks for the info.

 

Ok,all grounds and connectors are cleaned in boot area.
I found a bunch of wire harnesses and three way bullet connectors inside car.
passenger side rht front kick panel under dash.there grouped with number tags.
29,28,31 is this part of wire harness to boot?

 

No. The ECU to engine harness is one continuous unbroken huge bunch of cables in an outer covering. <foget the cabin wiring, this is not your problem. Have you by any chance screwed any screws into the body in the rear of the front wheelarches? If so, unscrew them as they can pierce this ECU to engine bay harness.

Have you rebuilt the injector harness including all the wires yet? if not, you have to or you will never eliminate this as a problem. have you chnaged the resistor pack?

Greg

 

As Greg said, there are NO bullet connectors of your description anywhere in the Jag from the factory.

Someone has had issues with those wires and the corresponding ECU terminals prior to your ownership. The bulkhead connector is right there, as in adjacent to our GAS pedal, and the loom is a HUGE thing, that snakes through the car to the boot.

I am with Greg on the EFI loom, it is causing grief, maybe NOT the only grief, but certainly confusing a lot of other diagnosis for sure.

The car may not have an alarm type system NOW, but maybe it did once in a previous life, and the removal has left some ign wires partly exposed, as these installers are usually not the most fussy workers, and I have seen a LOT of shoddy installations, and even worse removals.

 

I will "THIRD" the statement, rebuild the FI Harness.

 

I have replaced the wire to power resistor that was grounding.and replced power risistor.
I have good v to all injectors.12.43v should both wires to inj have volts.I thought when ign is turned on,main relay is energised and supplies voltage to one side of injectors,on the K/b wire.then the other,wire gets the pulse from ecu and resistors.to open and close injectors on pulse.Unless im wrong?
I bought wire yesterday (16 gauge) to do inj harness. Ill be working on that today.

Ok,I know this was touched on before in earlier post,but on the igniton amp,the two white wires,one goes to tacho,other to ecu signal.on the one white wire,the tacho is connected to,it has only 5.4v the other white wire I have connected to the thin white coax wire to ecu,has 12.45v.Im wondering if they are mixed up?
should ecu signal only be 5v and tach 12v.??maybe the signal to ecu should be only 5v like all other signal wires.?

 

Here are some pics of my spare amplifier.




For the avoidance of doubt All the wires are as follows:

• Large double wire with double plug on exiting from unit RHS goes to the dizzy bottom
• On the white exit bung there are FOUR wires; L to R in the pic as follows: LH wire with spiral blue trace to tacho; second and third from left wire to coil, white one to coil + white with black trace wire goes to coil -; fourth wire (with non - standard plug in photo) white with grey trace, to ECU shielded wire.
• earth wire to bolt on unit top

NOTE: there are two extra wires to the coil from the auxiliary coil in front of the radiator. These also should be black trace to the coil negative, solid white to the coil positive. There is a third wire to the coil positive that brings in the 12V feed. Worth checking that the aux coil wires are fitted to the correct terminals on the auxiliary coil.

Greg

 

ok mine is hooked up exactly to those specs. but why is the one wht/blue to tach wire only has 5.4v with ign on and hooked up?? other wire to ecu has 12v.
ok,If you go back to post from grant on page 10 where he gives details of car he checked that was running.He checked voltage on the TPS with ign on.Basically: green wire on tps harness to,The two yellow/pink wires,chassis side,has 4.99volts.That checks good in mine,the yellow wire TPS harness to,yellow/blk wires,chassis side.0.00volts.checks good on mine.
The red wire TPS harness,to single yellow/wht spiral wire chassis side. I only have 1.45v not 4.95 like on grants car.I checked it back at ecu,and the same 1.45 volts.
not getting the required 4.99 v from ecu.Wire is good.since voltage is same both ends.
Also my volts on between red and yellow on tps with ign on is 0.0 v not .34v anymore.

 

Ok,I made new inj wire harness.Exactly patterned from old one.Made from 14 gauge wire,all white wire but marked each wire at injectors end with correct color code.K/b to each one from main relay.O/U to injs 1A 5A 3A.O/W to injs 6A 2A 4A.
O/S to injs 1B 5B,3B. O/G to injs 6B 2B 4B
now with ign on,I still have 12.45V to both sides of each inj.all the other wires are good.TPS wires all with correct voltage.At Idle .34 v at full throttle 4.85
Car now starts but only runs for 5 seconds.then dies.I dont understand what else I need to do.
I have fuel and spark and signal on coax wire to ecu.I have 3.46 v on one wire of cts 5v on ats wire. both coils are good.
SO WHY DOESNT IT STAY RUNNING! *...UGH..

 

Are you running a known good GM module? Suspect ones will sometimes allow the car to start then once warm they'll shut down.

 

.

Sorry just realized you said 5 seconds not 5 minuets.

 

No prob ,and yes both ecu's i have are the same the 6u type original,I still have no pulse to injectors.I checked voltage at inject multi plug rht side eng up frnt.Unpluged.With ign on,I have as follows:All K/B wires from main relay,have 12v at plug.The O/U,O/G,O/S and O/W.all have 4.6 V.Is that to be correct.?Because,with plug connected to inj harness, when I check voltage at inj plugs both sides have 12V with ign on not cranking.
Im asuming that the Orange wires with half the voltage should be the same at injectors.

 

ok, dont know why I didnt check this before.
At multi plug for inj harness (unpluged) ign on using volt meter chassis side of plug,like i said I have 12v on K/B wires from main relay.And all orange wires have 4.6v When I crank eng all orange wires pluse up voltage in cycles like they should. Now when I plug multi plug into to inj harness,(ign still on) all the orange wires, inj harness side of plug that go to other side of injs have 12vs dont know why..They should be 4.6v untill cranking eng,then they should pulse up to 12v in cycles.If thats how system works..
doesnt make sense..

 

Some progress me thinks.

The ECU on the P Digital very simply switches the earth of the injectors, in that 4 banks of 3 we discussed previously. I dont think that is where your issues are.

My suggestion, and yes I am clutching at straws and sleep, so here goes.

UNPLUG the 2 suspect wires at the amp, as in the tacho and the pulse wire. Noting which comes from which harness wire. FOGETthe tacho for now, it will run without that connected. Plug what is now the tacho wire into that pulse wire, and try it.

My reasons, that make sense to ME are.

The 5 seconds or so of running is classic "running on priming fuel" due to lack of pulse down that wire to the ECU. I know you have tested continuity on that wire front to back, so breakage is now eliminated, so incorrect pulse is the only other logic to me at this time.

I know its NOT the CTS, coz there would be ZIP if that was not connected correctly.

The ATS is only a trimmer, so out of teh thinking for me.

The TPS is all that is left, and that seems to be OK.

Those bullet terminals you found inside the car are a strange thing, and I presume (hate that word) the integrity of the connections, AND the correct wires connected has been checked out.

 

Ok ill try switching the signal coax wire in the am and see what happens.
Those wire inside car are for power windows door locks and other in cab stuff.