Hi I have a 5.3 xjsc 1987. I took out the injectors and to get them cleaned and also manifolds off to spray them.
After getting the injectors back it fired up roughly then would conk out. So figured the injectors need a tap as they stick after a sonic clean. I done that and also put a pulse box on them and fired compressed air through. They all are now firing.
But the car won't start at all.
Below is what has been checked.
I know I have spark.
I have tested back to pin 18 and all OK and not touching outer cable or earth.
Fuel pressure can't test but restricted the flow on the return bank and no change.
Also put vac tester to both fuel vacs and no change.
The injectors click when tdc turned and when turning over nod light flashing.
However weird bit now.
I removed the amp from manifold and injectors stopped firing but I have 10v going back to 18.
I found the amp has a ground issue by placing an earth onto the body of it. The injectors fire but still won't start.
I then noticed my tacho is going mental, as the car tries to start it's erratic and can jump right round to the red.
Then I noticed my miles on the gauge are also going round as I am starting the car. I'm not sure how that bit is possible I thought it would have to be moving for that to turn??
I have a spare ogm amp just the bit inside so I undone the box took the wring off and plugged it into that one and no difference and thats not earthing.
Anyone one with any ideas???
I notice on drawing the tacho has feed from ballast resistor pack but not sure where that is.
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Doesn't it seem to align with the repair? There is a ground wire on top of the passenger's intake manifold close to the fire wall. Did you get that connected?

 

Your referring to the white coax wire I presume?


At some point you may have to actually check the pressure


Not sure what you mean


Lift the fuel rail and see if they actually spray fuel

I'll need more coffee to mull that


which suggests to me lack of fuel to the injectors or stuck injectors. After cleaning how long did the injectors sit on your workbench before installing?


Tach weirdness is likely a poor ground or lack of voltage somewhere along the line

The tach takes its signal from the amplifier. There's no ballast resistor pack in the Lucas CEI so I'm not sure what you mean. There is a resistor inside the amplifier, though

Cheers
DD

 

Thanks for your reply as I'm new to this not sure how to do the edit bit but will try to answer each question. 1) I shall have a look fir that ground on passenger side to make sure. 2) yes the white coax wire back to pin 18.3)im struggling to find attachments that will allow me to test pressure.
4) I mean the two fuel pressure valves on the end of each manifold that use vacuum pressure to open or close I belive.
5)yep lifted injector done that and all fired nicelly
6) I'm thinking (I may be wrong) now that the amp uses the shell as its earth return. As there is no other earth apart from its one to coil. So unless it is bolted down its not grounding.
7) they were replaced the next day. Run rough so took them back out pulsed them with proper pulser and fuel and then with compressed air through the injector rail. All firing nicely.
9) so it's the mileage going round that's bloody wierd. The mileage click takes it pulse from the gear box transducer which I havnt touched when doing anything since injectors came back. So I will have to get under and have a look. Maybe I have a grounded wire or something is grounding and coming back through that signal path.
9) yes so I read after I posted they no longer have ballast resistors.
I am going to check my grounds and add another from the engine to chassy. And disconnect the transducer and see if mileage stops going round and maybe trace from there.
It's so weird all I did was remove the injectors which I have done before with no problem and now won't start at all.
But if you think off anything let me know. The more I think about the more I think something is either grounding that shouldn't or I have bad grounds.

 

IF the Injectors are spraying Bang Juice, as you said, then the only other requirement is Spark.

Find an old spark plug, push it in the end of the easiest plug wire to access, lay that plug on something to create an earth, and crank it, FAT BLUE spark should be seen.

Inside that AB14 amp, tucked in one corner, is a round condensor looking "thing". Undo the single screw and remove it. It is an OLD noise suppressor, and they leak Ign Volts to earth. NOT needed, and the root cause of 85% of V12 NO start, as that leakage prevents the coils/s from firing.

Check the CTS (Coolant Temp Sensor), and I mean the wires, INSIDE the plug, the break.

ALSO, since they would have been disturbed, the ATS and CTS plugs are not mixed up??, it is so simple to mix them up, and you will not be alone if that has happened. It sounds like that answer is NO, but just saying.

Welcome to the Forums. When the beast is sorted, PLEASE do an Intro in the New Members Area.

 

The tacho is driven by the amplifier (assuming your car is Lucas ignition?). The thin white with blue spiral striped wire coming out of the amp. If the tacho is going mad it is likely an amplifier problem, or a short, or a duff signal to the amplifier from the dizzy pickup. As Grant says, a proper test for spark is the staring point. After that, if no proper spark, I would remove the dizzy cap and take a look inside it first, and check all the wiring to the coil, amp, and from the dizzy base to the amp. If and when you are certain that is ll good - which is unlikely if it is OEM and partially cooked, then start looking at which parts to replace.
The amp/amp loom has a dedicated earth wire by the way, it has a round connector and is a small open woven earth strap. Have you got that connected?

 

So definitely have spark I have done a test for each plug.
defiantly the two sensors are in correct way round

That was the bit of info I was missing I have seen posts in past saying disconnect something inside the amp they just said what it was but never described it and as there is the white blob (which now been told is resistors) and two other bits in there I didn't know which of the three it was so thanks for that.

I work on computer systems and all electrical systems on trains as a technician fault finding them. But a bloody jag is throwing me!! 😂 😂

​​​​​As I say the more I read and think about it I am either shorting somewhere or more likely I'm not grounding properly. Time to remove grounds and clean and add extra one to engine. But will try the amp bit.

​​​​​​Yep when I'm not banging my head against a brick wall I shall do an intro! 😁

 

So I went through the car again yesterday cleaned the grounds next to battery. The only one I havnt done yet it the one next to starter relay at the front. I have found a crack in the dizzy cap so ordered a new one but not sure if that would stop it starting.

Drained the fuel out and replaced with new. Disconnected the bit inside the amp that was mentioned. No change. What I did notice as I have a spare old amp wiring and new module. I left the white blob resistor off and the car seemed to want to start better so not sure what that means?

Cleaned the ballast resistor pack, although need to find something to get into the female side connector. Belled through all the wiring from that plug to injector loom and all appears OK.

If not cracked dizzy I am leaning more back to the injectors. They are firing with noid light and with pulser on them appear to be firing nice jet.
What I have noticed is with the inertia switch up the car sounds like it wants to fire much better until fuel runs out. But with down it hardly wants to fire at all. Can I read something from that like I am overfuelling or something?
Or does this mean poor spark? I have taken them out cleaned and gapped. Most were black. With a spark plug in the lead from coil nice blue spark. At plug I have spark but would say its a whitish blue. New coil pack replaced a few months ago. Put the old two coil system back in and no change.

Trying to figure out what the tries to start with inertia up can point to?

If I have 1a or b injector out but connected to fuel rail. If I crank the car how much fuel would you reckon I should see in beaker. If I run the pump continuously and put a pulser on there I get a lovely jet. If I do the same and crank or open the throttle I wouldnt say I get much out. But then I can't find any info or how much I should for that. Only info on 1 min flow tests.

 

Buga.

The enertia switch cuts the pump, so NO fuel pressure etc.

The fact its trying better withut the pump sniffs of flooding. The Black sparkers, same thoughts.

Cleaning that resistor pack plug and socket, Lemon Juice, the real stuff, rinsed off with WD40 type spray.

NEXT

Unplug the CTS, use a paper clip, bridge the terminals IN the plug, and lay it somewhere it wont short out. It only has 5volys, but I rest it on a rag just dropped mearby. That will :fool" the ECU into a HOT engine, and may be the answer.

I have never measured the coffee jar of spray, basically, if there is spray, and its consistent, that will start the thing.

Cracked cap, not helping in any way at all.

You have spark, you appear to have Bang Juice, it should run.

Only other thought:
\
The sparkers are fickle in these engines, and repeated attempts to start a stubborn engine kills them in short time. Cleaning rarely does anything but give you the warm and fuzzies.

I use NGK BPR6EF ONLY in the HE engines. That Projected Tip is the best thing for them. The original spec sparker has the spark almost up inside the cone, NOT good for stubborn engines.

 

Thanks. Yep done the cts bit it did crank a bit better with the paper clip in, bought a new one also still no good. 5 volts there and also at air intake sensor.
OK will try the lemon juice trick.
Will try cap first and then may have to look at plugs then.
I did wonder if by cleaning the injectors to what the paperwork came back saying full flow on all is flooding the engine. I tried the mixer switch on the side of ecu in each full turn direction and centered and no difference.
If I am getting all the signals required eg. Signal for injector pulse and injectors firing. Would that rule out ecu or as ever is it not that simple with a jag engine?! Don't suppose there is a reset you can do on them is there?

 

You left if off entirely? The trigger to the ECU comes from the resistor blob.

The plot is thickening





Cheers
DD

 

Alex,

I may have missed something but have you gone back and double-checked your firing order?

Cheers
DD

 

The bit to remove in the amp is not the white blob; but the condenser-like thing, part C in this photo:

 

Yes tried it on the new and old one, and whilst it didn't start, it sounded more like it was actually trying to catch. A few months ago, the amplifier did die, no spark at coil. So got another one which I fitted and also a GM spare module which have used the inerds from the original one to test with.
Originally I hadn't removed the plugs when removed injectors for cleaning so should have been in correct order then. But since then I have checked and rechecked and they are right. I even checked tdc just in case even though hadn't removed dizzy and was pointing to 1.

​​​​​Occasionally the car would just about start after the inertia switch was pushed back down and it would sound as rough as houses and then die. Most attempts though it wouldn't and sounded better with switch up.

​​​​​​​I'm sure this is going to end up a bugger me is that all it was moment? 🙄😁

 

I have replied to the other part but went to moderator as put in a naughty word!! (Shane on me)😂 so will probably come up after.

I should say I only removed the ground wire that goes to the amp module from the white blob resistor. I had left it off by accident and noted the change in sound.

The bit marked c yes I have removed that. It's just a spade connector on the module so that was easy.

I can't do anything now until next week as back in shift but will try the new cap and lemon juice on the resistor pack and see what occurs.

Thinking out loud here I am just wondering if the crack in cap is allowing a spark to go down one of the retaining screws to ground. Which could explain the odometer going round as it sending a pulse through ground as I had disconnected the transducer in gear box, cranked and it was still going round so I have disconnected the instrument cluster for now. I hadn't touched any of that just removed injectors and all was fine before so it's one possible explanation as to why I am having such a wierd fault like that. After just removing injector rail and inlet manifolds.

 

A cracked cap can certainly cause all sorts of things, including those you describe.
By the way the earth you describe as having disconnected; if you mean A in my pic above, then it must be connected as this gizmo is a zener diode that protects the chip in the amp module from damaging spikes in the current.

 

Yes I read that somewhere it's for protection. It was actually if you look at the photo the spade terminal on the right on the module itself. The bit c you said to remove is on the left side spade terminals. (two on each post)

Well fingers crossed then it's the cap. I got so caught up in other bits I didn't do my first idea which was to check what I am getting at the odometer clock In the way of pulses when cranking and trace that back.

I shall report back when cap arrives possibly after Christmas now the guy has just told me. I shall try the lemon juice bit also and if none of that works I shall have a face that looked like it sucked the lemon instead!! 😂

 

I have no idea what this means! Just as long as you put everything back as it was except for disconnecting C.