So my injector harness was all brittle and broken and engine fiery waiting to happen and I decided to build a new one. Plenty of posts floating about on how to do that and it seemed pretty straight forward. Got that all done and plugged in aaaaaand it wont start. I have double and triple checked that I matched up the wires for each injector bank properly. Sometimes it sounds like one cylinder might want to fire but the moment is fleeting. I know that i have spark. I put a meter on the injector plug and one side has 12 volts with the key turned which i am assuming its meant to. I am kinda out of ideas as to what it is that i broke lol. As far as I can tell everything is plugged in that is meant to be. getting the old harness out was a bit of a pain so i suppose its possible that something got messed with down in there when i did that. I dont know what it would be though. Car cranks just fine, fuel pump comes on just like its suppose to and turns off again just like its suppose to when it builds pressure.

 

With key on, engine off both sides should show 12v



Very possible, and you wouldn't be the first, believe me.

Just take some time and carefully retrace all your steps. Might find a broke or unplugged wire. There's stuff in there that's so old and brittle it'll break of you look at it the wrong way.

Cheers
DD

 

Are any of your wires shielded wires? For the AJ16, there were a couple of wires that were required to be shielded. Not sure if your harness requires any.

 

none of the old wires were shielded, and none of the posts i read about building a harness mentioned it. i just used 16 gauge cross-link sxl wire from del-city for all of them

 

I have noticed something new in the process of troubleshooting. If I cycle the key several times before making the engine turn over, it will try to run for a second or two, but then it dies again. Not sure what thats trying to tell me.

 

Did you think I meant one side of the engine or one side of the plug? Should both wires in the plug show 12v with the key on?

 

Sardonicus,

That sounds like you have a fuel issue either with the pump not running when cranking (is it supposed to?) or else a fuel pressure control problem. By cycling the key, you're enabling the fuel pump to run for a few seconds each time, building up pressure. It then feels like the engine nearly catches with this residual pressure but there is no further fuel pressure to maintain the engine running.

As the pump runs, it doesn't seem like its a pump problem per se. It seems like its possibly the ecu not signalling the pump to subsequently run, or else the fuel rail is not holding sufficient fuel pressure?

Paul

 

Hi Sardonicus

As your Car is a 1987, it sounds as if you have a Lucas V12 rather than a 6cyl so please could you confirm what Engine you have

When Doug was saying you should have 12 Volts on each side, what he was referring to was that you should have 12 Volts on each side of all the individual Injectors, since it was the Injectors that you were talking to Doug about

As such this has nothing to do with the Spark Plugs but all of the Injectors on both Banks 'A' Bank and 'B' Bank

As Paul (ptjs) mentioned it certainly sounds like you 'May' have a Fuel Pump problem or even a Fuel Pump Relay Problem or a Main Relay Problem

The Relays are in the Boot/Trunk and the Fuel Pump Relay sits in the Black Holder and the Main Relay sits in the Red Holder but BOTH the Main Relay and the Fuel Pump Relay have to be Working or the Fuel Pump Relay won't work

The way to test the Fuel Pump Relay is to Ground the Orange Wire that goes to the Fuel Pump, which should then have the Fuel Pump running Continuously

This is only to Test it and see if She will Start and should not be left wired up like that, during normal use for obvious reasons

If the Fuel Pump Runs Continuously with the Orange Wire Grounded, then it 'Could' point to a Faulty Fuel Pump Relay and or Main Relay or even a faulty connection to the Ignition Switch

In any event I'm sure Doug will know as from what I remember Doug very kindly helped me to fix a very similar problem on my own Car

 

The engine in this car is the V12. I actually suspected the relays and replaced the main, I would have replaced them both but the parts store only had one. I can say that both relays do click, of course that doesnt necessarily mean they're making connection. When I turn the key, the fuel pump does come on, and it runs for a short time and then turns off. I assume it turns off because its reached the pressure its looking for. I will do more troubleshooting tomorrow, the battery is on charge now. If anything interesting happens I will update.

 

Hi Sardonicus

Nope!

The Fuel Pump doesn't turn off when Fuel Pressure is reached and so its sounding very much like a Fuel Pump Relay Problem that the Orange Wire Grounding Hack could well confirm

Could also be the Coolant Temperature Sensor on 'B' Bank in which case you could take the Plug off and then Bridge the Wires with a Paper Clip or any piece of Wire to 'Trick' the Ecu into delivering the right amount of Fuel

Here is a Pic of 'The Coolant Temperature' Paper Clip Trick on my AJ16 Engine but you can do the same on your V12

Testing The Coolant Temperature Sensor on the Car with 'The Paper Clip Trick'

 

The fuel pump turns off after 3 seconds unless the car is cranking, this is controlled by the ECU. I suspect the car is firing after repeated key turns because the injectors are getting a bit if fuel into the cylinders, but this is not being replenished by the injectors as it would if they were functioning properly.
This is what I suggest:

1. As OB suggested, find the orange wire that connects the fuel pump relay to the ECU, and run an earth (ground) from it - still goes to the ECU but also an earth. This will make the pump run continuously while the ignition is on.
2. see if the car will start and run.
3. if not, remove one of the frontmost (A1 or B1) injectors from the manifold but leave it attached to the fuel rail. Point the end into a jamjar. Then remove the HT lead from the coil to the dizzy cap, and repeat stage 1 and 2; except you need a helper to do the key while you look at the spray pattern from the injector. See if fuel is spraying out strongly.
4. Also check that the injector is clicking while the car is cranking - which you should be able to feel.
5. If not, replace the injector in the manifold and undo the fuel hose that goes INTO the fuel rail from the pump (A bank side) and repeat the test in 3 except that you are looking for a STRONG jet of fuel. It should be at least 4 or five feet long.
6. if all good, then the fuel pressure regulator on B bank is the likely problem.

If it fails any of these tests, report back with what happened. If no injector click and spray this would tend to point to a loom problem. Additionally, have you cleaned the power resistor plug and socket?

 

Hi Sardonicus

Here is a Pic of the Resistor Pack (aka Silver Box) that Greg was referring to, where the Plug and Socket of this need to be Squeaky Clean, where Lemon Juice as recommended by 'Grant' is the Tool for the Job

There is also a Pic of the FPR on 'B' Bank (Fuel Pressure Relay) as distinct from the (Fuel Pump Relay) that 'Greg' mentioned

Though never discount a Blocked Fuel Filter, if you are not getting the massive Jet of Fuel from the Fuel Pipe outlet, that would otherwise go into the Fuel Rail, again as mentioned by 'Greg'

Also very important to disconnect the HT Lead from the Distributor to the Coil, as just one Spark would be enough to send your Car up in Flames! and cause a Fire that you could never put out

The Resistor Pack (Silver Box) Plug and Socket Need to be Squeaky Clean! Or it can play Havoc with the Firing of the Injectors, a PIA to get to although its held in place by just one bolt down by the Headlight Nacelle

Another way to Test the Fuel Pump Relay is with a Test Light which may also be of help to others, so have a look at my Video that shows you how to do this

Testing the Fuel Pump Relay with a Test Light (see video) halfway down Page 46

 

As always thank you all for your responses, I really appreciate all the help. So, I got right after it this morning, got the fuel pump to run continuously and in the process pretty well confirmed that relay is bad, but moved forward and with the pump running continuously tried to start the car. No joy. I had read about the power resistor plug causing troubles for people so I had already gone ahead and checked that connection was clean and it is. Now at this point in the day the person that would be my helper to test the injector spray is busy with farm work so I skipped ahead to step 6. Undid the hose as it goes into the fuel rail from the pump, secured it in a safe direction and did that test solo by leaving the key turned and hooking back up the negative battery cable. I most certainly did not see a 4 to 5 foot jet of fuel, more like a 1 to 2 foot gush of fuel and now its break time while the fuel soaked engine compartment airs out a bit.

My next trip to town will include picking up a new fuel filter. Whether that is a problem or not it is super cheap to get a new one just to be sure.

 

Hi Sardonicus

Spraying Petrol all over the engine, is something that should be avoided even with the 'Dizzy Lead' disconnected as that's the way to turn your Car into a Fireball and if your Car is in the Garage, also take your House down at the same time

So if you ever try that Test again, push that tube into a bigger Tube and then hang it over the Fender/Wing outside of the Car and put the other end into a can to catch whatever comes out although the one or two foot petrol gush, sounds more than enough to me and I would be happy with that

As if the Car should catch on fire with the Pump continuously running, there is no way you'd ever put the Fire out so now you have identified that the Fuel Pump Relay could be the problem I would put the Fuel Pump back into normal running mode as it was before

Then be accepting of the Fact that the Fuel Pump is working as it should and try a new relay and if you replace the Fuel Filter make sure that you fit it the right way round, as its easier than you think to go and get that wrong as some of us have found out

So get back when you've fitted the New Relay and hopefully that should have fixed the problem

 

Sardonicus,

Maybe I missed something but as the pump always ran on the ignition key energising, what had made you think the relay is bad? Particularly as with the fuel pump now running continuously, the car still doesn't start.

As I said, apols if I missed something in the last few posts!

Cheers

Paul

 

I know you say you double triple checked the wiring harness, but the car ran before you changed the harness and not after. So I would look there. You got the banks lined up, but are the sets of injectors correct? It fires three injectors at once, every other cylinder. Please, go check it one more time thoroughly and make sure that its all correct.

 

Hi Paul (ptjs)

Very good point!

Which now has me thinking that the Coolant Temperature Sensor is more likely to be the problem

Sardonicus

Did you try the 'Paper Clip Trick' on the 'Coolant Temperature Sensor' ?

 

The whole engine didn't get doused, a couple bits of intake on the right and a few other things, but i hear you - gas everywhere is bad.

No joy on the paperclip coolant temp sensor thing.

I decided the relay was bad because I took it apart and it was scorchy in there. Im surprised the pump came on at all but not particularly surprised that it didnt want to again.

So I got my helper and popped an injector out and they aren't firing but I can't for the life of me figure out why. Everything has 12 volts. I built this harness as essentially 4 individual harnesses that I combined into 2 four prong plugs. I built the even cylinder harness separate from the odd cylinder harnesses for each side and I color coded them so that I could not mix them up. I have a wiring diagram from the book and I matched up the books wires to the appropriate cylinder harnesses wires. I know they are right. This diagram shows orange/white for 2,4,6A, orange/green 2,4,6B, orange/blue 1,3,5A, organge/gray 1,3,5B. along with the pink/black.

I replaced the other relay, both are functioning normally.

On a side note, apparently in amongst working on everything else the very loose fitting plug on the coolant temp sensor had popped off. So that is plugged in again now, Im glad this troubleshooting led me there or who knows when i'd have found it.

And discovered the reason it acts like it wants to run for a second. When the fuel rail is first pressurized there is a momentary spray from the injector. Not a lot, just a little misting not even enough to gather at the bottom of the container it was point into. But cycle it enough times and im sure it would add up to enough to make a cylinder fire once

 

Clean the contacts on the EFI resistor thingy. Silver box on the inside of the right fender at the front. May not fix the problem, but needs doing anyway.

Your wiring sounds correct, but if the injectors aren't firing I still suspect something electrical is the issue.

 

that would be the power resistor thingy and that connection is clean. pins are clean and shiny, i took a little brush i use for cleaning carb jets to the plug, its all clean. And i really just did that for the sake of doing it because it was pretty clean looking when i unplugged it