So today i collected a set of NOID lights and i have found a problem, when the light is plugged into each injector you can barely see a flicker, it's so faint.. however there is 12V on both sides of the injector plug with the ignition on.

I double checked to see how bright the lights were supposed to be and just hooked them up to a 12v battery and they are good and bright, i am getting nothing like the voltage/current i am supposed to at the injector.

I have once again re-checked the validity of the ground wires at the back of the intake manifold, no change, i have pushed and pulled the injector harness whilst performing the test with no change, i have checked the plug going into the power resistor and all seems well. I am betting there is a bad earth somewhere in the system, i will have to go over each of them in turn to see if something seem obvious and re-test as i go.

 

OK, fine
What about the engine-body ground ? However, if the starter motor turns the engine over well, this is just a shot in the dark.

The way the ECU makes the injectors fire is to earth them so your comment about bad earth could be the answer. I have a NOID light in my toolbox from my time with a Series 3 and it lit up lovely when I put it into one of the fuel injector sockets, so clearly you are getting close to the problem. Basically, it's a matter of tracing through with an AVO meter to see where the unwanted resistance is.

Have a read here: -

http://www.jagweb.com/aj6eng/42efi/index.php

 

Hello again Russell . . . Sorry for delay here but been doing Easter things. Fraser is spot on . . . you sound close. Noid light should be bright and clearly indicate each signal. Yes; you should clearly hear the clicking of injectors.

With every one of the current crop in Ken's Kattery all being EFI based Jaguars, I have adopted a 3-step checking process. Apart from the bench battery (many will say unnecessary, but I check a lot of injectors), the suggested "kit" is simple, cheap and unambiguously foolproof.

First step; at the bench - but can be done with injectors in situ provided car battery and injector wiring are all disconnected - uses an independent fully charged bench battery; NEG lead wired in black from crock clamp to a black "earthy" probe; POS lead wired in red from crock clamp thru a 10A fuse to a red "hot" probe. By touching the 2 probes briefly on the injector pins, you are applying the 12-13V directly across the injector and should be rewarded by a sharp, unmistakable "click". Replace any that do not respond; send for service any and all that sound different. I emphasize powering "briefly" . . . have no idea of burnout threshold time, but leaving to answer phone should kill it nicely!

Second step; using a DVM (some may include "hold" function) and with all injectors fitted to engine . . .

• battery connected; measure and record standing battery voltage;
• IGN ON; measure and record all 14 injector pins (2x7) to earth;
• look to do so quickly and accurately, looking for any variances to the battery standing voltage; then, evaluate or report findings.

Final step 3; uses the Noid light you have now acquired and I agree with Fraser that you should see clear, unambiguous signal activity at each and every injector. Weakness of your Noid light signalling sounds like you aren't. Why?

OK . . . good logic that starter enjoys a solid earth, but take care in interpreting that. Does your starter have separate earth strap to body? If so, then starter function does not guarantee solid grounding at the control module. I think it was Fraser who pointed out that all the injector functions are "ground seeking". He's right.

Note the following in blood . . . while the "hot" side of all injectors is fed from a common fused power lead, each and every injector has its separate "ground seeking" side return to the control module for programmed switching. When one of the latter leads is briefly clamped to earth, that injector opens, squirts, then clamps shut again. That grounding, IIRC, is applied nowhere near the injector, probably not even at or on the engine . . . look instead (either electrical section of manual or wiring diags) for location and grounding of control module. There is sufficient variability between models, overlaid by RHD vs LHD, I rely on you to check location of module and its earth/ground point.

One final suggestion . . . never trust a resistance measurement to check grounding . . . remove it; use emery paper on ALL faces and fixings and refix with smear of conductive paste . . . even better than petroleum jelly.

Cheers,

Ken

 

XLNT DESCRIPTIONS OF THE ISSUE AND THE DIAGNOSTC PATHS.


My compliments.


I can draw a conclusion. The intake manifold ground path is non existant or poor.


Trial. Ground the intake back to the point on the wing wall where the battery - cable is attached. Try the noid again.


Good luck with the "Electrickery". At times, I think I get it, at others, I realize I don't!!!


Carl

 

Good idea. And take only a minutes and costs nothing.

I'll note that the bundle of ground wires is (or should be) attached under one of the rear mounting bolts of the water rail, not intake manifold. And Jaguar, anticipating an problem, perhaps, installed a small braid ground strap from the water rail to the engine itself.

Cheers
DD

 

You guys are so helpful. i cannot thank you for your comments and advice, talk about a wealth of information....

If i remember i think the ECU grounds through the ignition switch, i will verify with the wiring diagram later.

The comment concerning the "extra" braided ground wire is certainly true, i think i have it located at the front of the intake, i will remove, clean and re-install.

Thank you Ken for the list of things to try, i recently built a small 120vac to 0-32vdc power supply with a max of 1A (if i remember correctly) so will break that out and try actuating the injectors themselves to see if they are happy to do some work on a Sunday (If the rain holds, looks pretty grey out there this morning)...

Russell

 

That bundle of ground wires at the water rail are the ECU grounds.

Cheers
DD

 

Doug, you're jogging my memory here very well. I did a major engine strip down and rebuild in the very late 80s, and I remember having the water rail and a load of other engine parts powder coated quite thickly and the car just would not start when it was all assembled. Once I had got the coating scraped off where these leads went, and also made sure there was good continuity between the leads and the car body, the engine started.

Had plenty of other trouble later, of course !!

 

Smelling imminent success.

Ken

 

stop raining, stop raining, stop raining

PLEASE stop raining......

 

California . . . non-stop rain?
Who wrote this script?
LOL

Best wishes,

Ken

 

Russell is just a few miles up the pike from here. It wasn't supposed to rain today!!!!


Looks like we have moved in to "flood or drought" mode. Akin to "feast or famine".


I think Russell is just about on to blinking noids. !!!


I see a bit of light out, just mebbe our promised sunshine is back.


Carl

 

how old is the fuel pump?
Walter

I am going over everything again and in the manual it states that the internal resistance of the Auxiliary Air Valve needs to be 33ohms, i am getting just under 21ohms.

i have seen on other posts similar lower than normal results.

Without knowing exactly what this air vale does and how a low resistance would affect it i am running blind..

Can someone please interject some sanity for me. (Starting to clutch at straws)

thanks

Russell[/QUOTE]

 

Carl

I can only hope it holds until i get home later tonight, yesterday was agony with the drizzle outside and not able to keep moving forward with the project....

russell

 

[QUOTE=new mexico;1662388]how old is the fuel pump?
Walter

No idea!!!, however the pump is able to give me the required pressure at the fuel rail.

 

Yesterday and today i managed to get a little time with the car and spent a good deal of time cleaning and securing all of the grounds for the engine and body, i checked with the noid light again and no change, i also installed a jumper from the - terminal of the battery directly to the grounding wires for the ECU on the manifold/water rail, no change. Verified 12v on both terminals of the injector harness.

So right now my thoughts are as follows (In no particular order)

- There is a break in the ground wires from the ECU
- If the ground side is good then it must be power so there might be a dirty connection that allows 12v with the ignition on but this drops when cranking
- Bad ECU

I will look at the wiring diagram again later to see where the ECU derives it's power and what is in the chain before it gets to the ECU to see where there might be a bad connection.

Not sure if the power comes off one of the 3 relays on the firewall so i might have a bad relay.

I'm going to win dammit!!!!!!

 

The "main relay" on the firewall supplies voltage to the ECU, the injector ballast pack, and (indirectly) the fuel pump circuit. Since you have 12v at the injectors the relay must be operational....but you could still have a wiring problem after the relay

Just for giggles, and since your checking things....

One of the black/white wires coming off the coil "-" post runs aft along the water rail. This is a "trigger" signal to the ECU. Make sure this wire is in good shape.

Cheers
DD

 

Worth checking, for sure. These FI systems really like full voltage. A voltage drop could be a problem.

Cheers
DD

 

Today i went through a number of checks and i also re-soldered the main 4 wire ground connector on the back of the water rail as it felt a little loose where the wires were soldered....

I pulled the power resistor pack and cleaned all of the terminals, i unplugged the 2 10 wire block connectors where the injectors plug into and cleaned everything so to ensure a good connection, the white wire that feeds from the - of the coil i cleaned and re-landed.

I also took the time to pull the ECU and check continuity between the ECU plug and also the grounds for each injector along with the main power supply to the ECU and all seems well there...

The last thing that i noted was if the Air Flow meter plug is disconnected the noid light flashes a great deal brighter, also the injector plug (non switching side) keeps about 11.3 volts when cranking so the power is still getting there.

So i am trying to determine why the AFM has an effect on the ground switching of the injectors through the ECU.

Any ideas?

Oh and 1 injector is stuck fast so need to send them back to be done again

thanks

Russell

 

Hmmmm. I'm not sure what to make of that

I'll do some mulling. An epiphany might hit. Or not.

Cheers
DD