Hello Good People.

I have another open thread that's very broad concerning the possible restoration of a 1990 V12 XJS. I figured I'd begin a second focused on this ONE problem I'm really struggling with. I have power to my injectors (both leads) but no pulse while cranking. The injectors don't seem to activate or fire. I have spark.

1. I've "bridged" the coolant temp sensor CTS for a hot start, and have a new one on the way.
2. I've cleaned the connections (to the best of my ability) on each FI plug.
3. Thanks to Mr. Grant - I will do the TPS test by fully engaging/opening the throttle to see if the ECU is electrically triggering
the Injectors.
4. I have (to the best of my ability) cleaned the plugs on the Lucas ECU. Is there anyway to "test" a Lucas ECU?
5. I've tested a few of the injectors with an alternative power source. Some fire some seem stuck.

Its Marelli/Lucas ignition and injection...

I'd be very grateful for suggestions in troubleshooting this issue.

 

It is what we call a Marelli car.

There is a resistor pack, size of a cigarette packet, sort of, I dont smoke, so guessing, on the inner panel INSIDE the engine bay, RHF corner, low down. It has a multi pin plug in its base. Remove that plug, remove the resistor pack (2 screws), clean the male and female connector THOROUGHLY, then clean them again. Refit the pack, and replug.

You will have a "signal wire" that communicates engine spark pulse TO the ECU. I dont know where it is on a Marelli cars, but Warren will slide in when he wakes up and give you the good oil on that sucker.

On the Lucas cars it is referred to as "The dreaded shielded wire" and is the reason they die, and the same goes for yours. NO pulse down this wire, NO go the beast.

Stuck injectors is NOT a good sign, and will need to be sorted, or other things can and will go AWOL.

You will still have an EFI loom in Death Valley (bottom of the V), and at 27 years old is probably toast, and reeking havoc. If any of the EFI loom pigtails are the slightest bit brittle, or crispy, that will need to be rebuilt FIRST.

Before starting it, or even trying, the fuel hoses should be addressed. If the injectors need removing for cleaning, the hoses will be damaged. If the Injectors stay in the car, those hose will leak, and fire is certain. They may "look" fine, HAHA, I have had 4 trips to Vegas paid for by V12 engine fire rebuilds, where the owners claimed the hoses "looked" fine.

 

Thank you Grant!

Tonight I'll get connection cleaner for resistor pack and the many other connections... I had the RPack off the other day. I also need to get bulk small vacuum tubing and start replacing all the vacuum lines I can.

Looking forward to Warren jumping in to to give marching orders. I've decided I'm going to take this car and project no matter what....

Q: Even if temporarily, to see if that dreaded wire IS the problem, is it possible to just run a wire - outside of the car from bonnet to trunk ECU - to TEST possibilities of a bum wire? Testing purposes only? And, do you by any chance have a 'pin-out' chart for the Lucas ECU on a Marelli car? Is it 18 for EFI, like the Lucas car?

I'll be able to get to "CrabApple" tonight for a little bit. My full days working are Mon and Tues. Sat and Sun - half days.

Cheers!

 

The ECU needs to see a tach signal to time the injectors, on Marelli cars this signal comes from the Marelli ECU, located in the side kick panel LHS on a RHD car, so I would guess RHS on a LHD car.

On my car this signal wire goes from the Marelli into the engine bay and connects to the terminal that would have connected to the Lucas ignition module, the connector is in the middle LHS of the V just in front of the throttle capstan. Check this connection and make sure the wire is not broken or damaged.

Also measure the voltage on BOTH terminals of an injector, you should have 12volts to ground on BOTH sides.

Let us know how you go,

 

Hello...

Thanks for that Warrjon! This will be the first thing I start chasing down when I get can get into it again. Have some family members in town, so maybe not tomorrow - official NYC family tour guide, dude - is me :/ - Monday might be my next dive. Is it possible to be a little more specific about the connector, the capstan (new word for me) and what I'm looking for? How do I ID the wire at the ECU?

I do have 12v to ground on both pins at the plug... How good a sign is that?

I've located my Marelli ECU and you are correct. It is on the passenger side "kick panel" (great new words) on the passenger (RH) side of my LH driver. I actually even have a spare if there is a prob with this one. Fingers crossed.

I was with C.A. today and found that a hose coming into the boot that was to connect to the Lucas ECU was not connected (see photo). I don't know if it ever was connected when turning her over, working to to start he up. I never knew it was there and don't know what the hell it is or for, lol...? See pics. Im sure you already know what Im talking about. I'd like to know where it ends up in the engine bay as well, so I can check, if you can share that?

Also.... Is the THIS the correct ECU for the car. The guy who gave the car to me created some doubt in my mind today. (see pic)

This evening was an evening of cleaning connectors. Any and every I came across including the Lucas and Marelli ECU's and "power resistor" wiring... Maybe you will cringe at this but, I opened the Lucas,,, it was clean as a whistle inside. Held the board up to the sun and saw nothing out of place. No burn or fried circuits, ribbons, boards or... A very very little crust on one or two resistors - like on a battery terminal. I should have taken some pictures and will next time. With modern tech and high resolution you would have been able to see exactly what I was seeing, perhaps better than me in the moment.

Anyways - good night gentlemen... again - much much appreciation...


hose connect on ECU



IS THIS THE RIGHT UNIT?



ecu hose and little canister? in boot area

 

That hose leads from the balance pipe between the two intake manifolds. It supplies the vacuum reference for the ECU to base all fueling calculations on.

Disconnected, the ECU thinks your at full throttle, CTS says cold engine and TPS says closed throttle.

Failure to start is guaranteed.

check the tube running to the engine is clear by blowing through it and if you're adventurous reattach it to the ECU and test that it holds vacuum from the engine end. It hard to see or reach and don't drop it down into the depths for gods sake.

 

Thank you Thank you Thank you ---- now, where IS IT in the engine compartment/bay?

 

Have a beer or 2, steady the nerves first.

Look at the BIG 1" steel pipe running across the rear of the engine. In the centre of it, on the under face, is a 10mm spigot. The other end of the hose in the boot attaches here. It is NOT a rubber hose all the way, just a hose at each end, with a metal pipe under the car.

This is the Pin out I use for engine fire cars, and they are generally 6CU or 16CU units, so would be the same basically.

XJ-S ECU Pinout table.doc

V12 EFI Schematics USA cars.pdf

The EFI schematics is for USA cars.

 

Ahhhh,,, you guys are amazing!

@Grant, thank you for the descriptions and diagrams. The MS-Word write up is brilliant! I've been wondering what the 1" piping that surrounds the bank sides and wraps around the back of the engine is all about. To be clear (and this is from memory as I am not at C.A. right now), is it the piping that begins/terminates in two short rubber hose sections bound to the 1" "rail" with what appear to be hose clamps? Then, a 1" down running tube at the "T"? If so, I think I understand. Beggars cannot be choosers and aught be careful about wishing for 'more' but I wish that V12 EFI schematic (although great) were a little clearer and offered a little more info.... BUT I am starting to get an idea of the FI grouping and sub grouping idea. I guess I just wish some of the large 3 digit numbers in the diagram had a "key", so I could know which each component is/was. Also - what does the "CU" in in 6CU and 16CU represent? In 6.0's it seems like I have seen numbers 24CU or something.

@JigJag --- "Balance Pipe" Got it. Am I right in guessing that it balances the vacuum and pressure between the two intakes? Is that the reason it needs to be an inch in diameter? Much of this is new language and idea for me. Although I think I'm slowly catching on. and NO,,,, no dropping anything, lol

Grant - someday,,,, me and YOU are gunna have a convo about ME and beer, lol...

Sadly, I don't think I'll be able to get back to "CrabApple" until Monday. By that time I'll have a fully charged or new battery and a bit of a plan O attack.

Again, deeeep bow of appreciation! And, for those it applies to - happy holidays and w/e...

Jay

 

OH! and All...

Is it possible to by bulk fuel line/FI hose? I believe I can fab my own hose connects. If so, what specs do you recommend - are required? Any special instructions?

One thing I could (want to do) do over these next days is disassemble the fuel rail, paint, clean and inspect injectors and have them ready for when I receive the "O-rings" and can put things back together... Hopefully Monday or Tuesday. I also have new injector plugs coming. I will solder connections.

 

(pls see previous posts ^^^^)

Hi again, also,,, and I hate to ask.

What is this plug... Found it in the boot floating free (see photo).

And, how important is the Air Temp Sensor (ATS) in all of this? Is it like an MAF Sensor and will seriously affect what I need now in starting? If so, I will order. If not, I will hold off a while...


Dont know where these wires go... They were free in the boot. For a trailer hookup?

 

Can I make a suggestion - get the car running before you attempt any other repairs, this way you start with a car you know is running so if you repair something and the does not run then you have only what you have done to fault find.

I'll take a picture of the connector I was referring to.

 

The red plug thingy is the feedback monitor socket. You can use a voltmeter here to monitor what the oxygen sensors are doing. You *might* also have a similar two-pin socket floating around. It has a jumper connecting the two pins. Remving the jumper allows "closed loop" operation in "P" and "N".

But, you might not have it at all. I'm not sure if all cars had it. The '88 and older models did, at least.

Not sure about the single stray wire in your pic. It looks like it might go to the interface unit for the trip computer. Not 100% sure. What is the wire color? Is it black with green? I can't tell for sure


Air temp is monitored for "trimming" the fuel mixture a bit. A fault here would not prevent the car from starting.

Cheers
DD

 

This is the dreaded shielded wire. It is joined just in front of the 5B injector

 

Here ya go. Parts drawing of he balance pipe. It does NOT show the spigot, but the area that the #1 is pointing at is close to where it is on the underside.



I will sort a legend when I get time, maybe later tonight?

I agree with Warren, slow down, HEAPS, get it running on 12 cylinders, then venture on from there, ONE thing at a time. The random, many items, will have you stir crazy, and frustrated.

The ATS is only a trimmer, and will NOT stop a V12 starting or sunning. Mark the plug, as it is the same as the CTS, and will fit, and that will kill the engine in less than a heartbeat.

You will drop things, it is a passage of V12 initiation, and worry not about them, find a replacement. It will NOT drop out the bottom, trust us, and will be gathered up when the engine comes out.

My tool box gets topped up every time a V12 comes out, all sorts of weird stuff in there.

 

Here ya go. Knew I had a legend somewhere.

For some bizzare reason I use the Australian Schematics,haha, but sent you the USA one coz you guys have some weird shiit on your cars for emissions.

If there is a legend number that does not compute, let me know, I will refer to the master scribblings in the shed, and come back with an answer.

V12 EFI schematics Australian cars.pdf

 

Understood as to slowing down, Grant and Warrjon... Here's the thing. When I began working - I realized that both long hose FI's at the end of the rail were not activating under the cars power, so I pulled and tested them with 9volt alternative source. They were the only I could get to... One fired/activated one did not. Even the one that did,,, it was a "chunky" dribble-ish stream. Not a "spray", def not atomized spray. I decided to remove the fuel rail to check and clean all injectors OFF the car at that point. Some of the hoses were/are cracked and falling apart. Heeding Grants earlier post, and looking at proximity to spark, hearing stories of fires etc - I was and am very apprehensive about turning the car over even to test, IF and WHEN I get pulse in the FI system in the condition the lines are in.

All that to say - I kind of have to replace hoses (at least) now. Your point about one thing at a time makes perfect sense, but.... Perhaps I jumped the gun but I thought there was NO way around dealing with these injectors and removing the rail to get to them. Hose size and type would be great - I'm sure I can dig around and find the specs if you dont feel comfortable or dont have.

________

Grant - Thanks for the Legend and all the Docs! HELPS lots for work and the learning curve! Looking, for the untrained eye, the engine does resemble a big bowl of BaSketty, lol. I heard that said about these cars somewhere in a thread. BUT,,, its becoming clearer . Im sure I'll find that VAC hose. Good to know about the AIR Temp Sensor. The air filters are not in, the ATS is not screwed down to its filter, does that matter? That its not grounded? Oh and,,,, let the "dropping" begin, lol

Warren - Ill be looking for the shielded wire next time I'm in there. Will it be the same color at the Marelli ECU,,, and if leads from there to the Lucas - will color scheme remain the same?

And Doug - I do have another floater in the boot. It looks like 2 wires they are capped in a small but good sized ball of electric tape in the boot. Might that be the socket under that tape I wonder AND, what do you mean "closed loop" in P and N??? I have no idea what that means.

Cheers guy! I think I need to figure out some short hand, lol... Sorry for the BOOKS I'm writing.

 

Short version:

"Closed loop" operation is when the oxygen sensors are sending information to the fuel injection computer and the information is actually being used by the computer.

"Open loop" is when the information from the oxygen sensors is not being sent and/or not being used

For the purposes of making the car start and run you don't really need to worry about it.

Cheers
DD

 

Fuel hose:

I use 7.5, EFI rated hose, which I buy by the metre, or if the price i right, by the 20mtr roll, and Gates, Goss, or other KNOWN brand hose only. NO elcheapo hose here ever, and ALWAYS have it on the 5 year plan to redo.

The hoses "appear" crimped to the injectors and rail, they are not, They are push on with very sharp barbs on the spigots, and the tin cups are an aid to compressing the end of the hose just a tad.

When you remove the hoses, be careful, as damage to those barbs is sooooooo easy to do, and then Plan B must be used. I will NOT confuse with Plan B at this time.

The Inlet hose, RH side must also be replaced. Most cars are 10mm, some are a combination of 7.5 and 10 with a reducer/valve in that hose.

The crimped hose on the LH side of the rail that runs to the LH FPR MUST be replaced,. as it is also under rail pressure. Remove the tin crimped tin caps CAREFUL, and this will expose barbs on the ends of the metal pipes/fittings, and EFI rated hose can be used with EFI clamps.

The return hose itself, LH FPR to the chassis spigot, via the a/c cooler (if it still has one), is usually 10mm, and I use EFI hose here also, but it is NOT a requirement, as there is next to no pressure in this line.

There are many very detailed write ups in this section about replacing the fuel hoses, so a quick search will easily find them.

 

Great Grant! I spend a lot of time reading past threads here, learning what I can, so I'll do some learning for FI line replacement and repair... That and, for the FI wiring harness replacement as well... Not YET, in the future - I promise, lol

Since you're the coordinator, let me ask. Should I go ahead and make a second JagForums account for the XJS OR, is posting under my XK8 account enough?

This is the hose I ordered. It wasn't too expensive so, if this ISN'T the *proper* line, I'm ok with going back and getting the right thing. Let me know. I'll have to figure out how to go from the 5/16 or 7.9mm (I think it said 5/16's was 7.9mm) to the 10mm as you've described.

5/16" FUEL LINE HOSE 25 FT ROLL THERMOID 24078 GAS E-85 BIO DIESEL USA MADE NEW | eBay

Thanks for your attention!