North American 1992

[HPMotors]

Hey everyone. I'm in the USA and the car is also American, so please keep that in mind for any tips or advice you might have, I appreciate any thoughts.

I'm helping a friend try and get to the bottom of why their Elan will not start. He was driving the car and it shut off on him. Before bringing me into the situation he tried a new fuel filter, and verifying the fuel pump is working, verifying function of the inertial switch, checking for blown fuses, and a few other things. Since that time I have also re-verified those areas.

At the end of my testing, it appears that the ignition and mechanical aspects of the car are both as they should be. The car will crank up and run pretty much indefinitely when given an outside source of fuel (something like starting ether), and I've verified that the pump is working, and fuel pressure is making it to the fuel rail. However, when I checked with noid lights at the fuel injectors, they were not pulsing.

I've seen this behavior from malfunctioning immobilizer systems, except I'm not familiar with an immobilizer system that would allow a car to shut-off WHILE driving. So I'm currently unsure as to whether I'm looking at an immobilizer circuit issue or perhaps an injector driver issue failure in the ECU, or possibly a wiring continuity issue.

I'm looking for the following information on the immobilizer circuit; component location, testing methods if there are any, and a way to bypass it at least for testing. Also some better circuit information on the ECU system wiring diagram and component locations.

I'm looking for similar information for the ECU and it's wiring too. I'd like to verify continuity in the circuit for fuel injector 12v source and grounding/pulsing signals from the ECU as well.

Once again, this is for a North American version of the car. So I know components are located in different locations and wiring colors may be different. Thanks for any and all help.

[TorqueHorse]

Hi, sorry to hear you are having injector problems.

Now that you are a member of the forum, when logged in, you should be able to see a link to the Manuals section in the main navigation bar for the site.
There, you'll find the Service manual, Electrical manual, and Engine management manual (you'll want the "Closed Loop" version for the American/FED car) for starters, which have trouble shooting tips for the things you are describing.

Quick notes based on what you've observed so far. First, I don't think any FED versions were supplied with alarm immobilizers as stock, so if there is one, it would be an aftermarket thing for which wiring diagrams wouldn't be available here (but the fuel-shut off during crash/roll-over is included in those manuals). Second, being a fiberglass bodied car, folks complain about bad earths/grounding all the time. There are some ground points/rings for the electrical harness with the injectors that might be a place to start looking, if it is an intermittent issue that could arise while the person is driving and hits a bump, etc.

Others that have more experience with signals not getting to the injectors might chime in too. Welcome

[FunElan]

Maybe worth swapping in new injectors just to rule them out? Weird that it all shut off though...as those injectors fail in pairs.

[peteoddcar]

I think the loose plenum ground wires have given problems in the past.
Check the two inline connectors carefully between the body harness and engine dress harness.
By carefully I mean give them a tug test initially- they can make connection without being latched and then work out completely - this is especially likely if the car has had work done in that area above the transmission. It’s rare but terminals can snap inside the connector again a tug test on individual wires will find it
Also check there’s a 12v hot at the injectors when cranking.
Hope that helps

[HPMotors]

Thr me possibility that thr car doesn’t even have an immobilizer was considered. I’ll take a look at the section you recommended on the site here, and link the owner to this thread since he can look at those grounds and connectors mentioned. I honestly don’t recall what we saw when simply checking for 12v at rhr F.I. injector plugs. I know there’s some cars that are power switched, but that’s unusual. I’m assuming this have 12v at all times (with car in on or run) and are ground switched through the ECU. Thanks.

[HPMotors]

Hello, I'm back again. This will probably be a longer post. Sorry, and thank you to anyone who reads through it in an attempt to help. I tried to attach a picture of the wiring diagram I'm working with along with some explanations of what I'm seeing, but it's too large. If I make it smaller, it's too small to be useable. Its the diagram available on this site for the LHD non-japanese turbo version.

Quick recap, the vehicle shut off while driving. Currently, the vehicle will crank strongly but will not fire up and run on its own. The moment you give it an alternate fuel source (starting ether), it cranks up and runs smoothly. It will run indefinitely as long as you keep feeding it an alternate fuel source. That should verify the car has compression good enough to run, mechanical timing should be correct, and that the ignition system is operational. Other tests have been done to these systems to verify that out of a mixture of boredom and desperation, but all signs currently point to an issue in the fueling/engine management.

Testing so far:

Power supply to ECM?:
There was a concern about the roll-over switch still being activated/ECM relay being bad, but 12v at the ECU from that circuit has been verified. That should rule out the switch, relay, and fuses in that circuit. Fuses were verified good, and the relay was switched out with another known good relay just to be thorough.

Fuel Pressure?:
The fuel filter was replaced by the owner. During that part of the diagnosis, it was verified that the fuel pump is also operational. We can feel/hear fuel running through the fuel lines at the rail. I can pull the fuel line to absolutely verify we have pressure in the injector rail, but it's difficult access. So we haven't bothered because we're focused on the next section. It seems to be the smoking gun so far.

Fuel Injectors/Injector Circuit?:
The fuel injectors were tested with noid lights, and it was observed that they were NOT flashing while cranking or while the car was running on ether. It was then verified that we have 12v at the fuel injectors. We retested the fuel injector circuit with a graphing meter and could not observe a signal pattern. Wiring continuity for both sets of injectors was tested. Good continuity was verified from all four injectors back to the two signal wires at the ECM. The injectors were given 12v and then grounded externally to ensure they functioned. Clicking could be heard. It's possible all four injectors are operating electronically, but all four got clogged at the same time, but this is also unlikely. Since we do not have an injector signal, I doubt is is the injectors being stuck that is the cause.

ECM or CAS?:
Perhaps the ECM was not getting the signal it needed to know when to fire the fuel injectors. The CAS was tested to ensure it had good power, ground, and was outputting a signal pattern. These were all verified. The signal wire was checked for continuity. We then checked for signal production. We could see a 5v pattern along the signal wire from the CAS that was being tested right at the ECM. This makes sense, as I don't find it likely that the CAS would partially fail. I.E., that it would put at a good signal for the coil packs, but not also for the fuel injectors. Possible, but unlikely.

So ECM!
1) The engine will run with an alternate fuel source.
2) We have fuel at the rail.
3) The ECU is getting power.
4) The fuel injectors are getting power.
4) The CAS and its associated wiring appear to be functional. Its sending a signal to the ECM.
5) The signal wires FROM the ECM to the injectors are good.
6) However, no signal can be found on the injector wires.
7) So with what appears to be all other factors outside the ECM functioning, and all needed ingredients going into the ECM but not all needed ingredients coming out of the ECM, it must be the ECM that's bad.

A new ECM from Lotus was installed yesterday, and the car did not fire up and run. The previous steps were repeated, but nothing different appears to have shown up. Ideas?

[esprit888]

Excellent progression however I wouldn't assume the CAS is good based on the components replaced. As you know the Injectors fail in pairs, as do the coils. When it runs on ether does it sounds as if all 4 cylinders are firing? or rough running (on 2) Based on what you have diagnosed so far it appears as though you are saying all 4 fire on ether, so two out of the three required elements are there (Air & Spark) Ruling out any kind of intake blockage forward of where you are spraying the ether, and assuming the pump is running and you have checked the fuel pressure at the rail, my money would be on the CAS, or more specifically the HES. It failed suddenly while driving normally (just read the other post, possible a ground strap broke?) I would remove the CAS, make sure the drive and sensor wheel are in good shape and replace the inexpensive HES.

[Tuga2112]

when you say it doesnt start... what do you mean exactly ?
is there any sign of explosions happening ?

all the help i can offer is based on the UK car. however, when it comes to the engine. i think they are mostly the same (potentially FED cars have a O2 sensor instead of a CO pot because of emissions in california, similarly to the S2)

what happens when you have the ignition on, not cranking. and just pull the throtle by hand ? do you hear the clicking noises from the injectors ?

is there any CEL codes ?

have you confirmed that after turning the key to ignition (without starting the car) the injector plugs register 12v on 1 of the terminals (red green wire) when checking against a known ground ?

your description sounds like a total failure from all the injectors operation. and since you replaced the ECU already. i would be particularly suspisious of the Red/Green wire that feeds 12 volts to them... you mentioned the ECU has power. was that 12v feed checked between a known ground and the A6 pin ?
if both a6 pin and injectors dont have 12v when the key is turned. them fuse A10 or the ECM relay looks more likely... (since you mentioned all fuses have been checked, id look at the relay)

if you check the electrical manual v6 page 66 you can see the wiring diagram

[Tuga2112]

Excellent progression however I wouldn't assume the CAS is good based on the components replaced. As you know the Injectors fail in pairs, as do the coils. When it runs on ether does it sounds as if all 4 cylinders are firing? or rough running (on 2) Based on what you have diagnosed so far it appears as though you are saying all 4 fire on ether, so two out of the three required elements are there (Air & Spark) Ruling out any kind of intake blockage forward of where you are spraying the ether, and assuming the pump is running and you have checked the fuel pressure at the rail, my money would be on the CAS, or more specifically the HES. It failed suddenly while driving normally (just read the other post, possible a ground strap broke?) I would remove the CAS, make sure the drive and sensor wheel are in good shape and replace the inexpensive HES.

we seem to agree the issue is fuel, HOWEVER
the CAS controls the sparks. (if you read the wiring diagrams, its connected to the coil packs control unit)
unless there is something i'm missing ?

[esprit888]

Excellent progression however I wouldn't assume the CAS is good based on the components replaced. As you know the Injectors fail in pairs, as do the coils. When it runs on ether does it sounds as if all 4 cylinders are firing? or rough running (on 2) Based on what you have diagnosed so far it appears as though you are saying all 4 fire on ether, so two out of the three required elements are there (Air & Spark) Ruling out any kind of intake blockage forward of where you are spraying the ether, and assuming the pump is running and you have checked the fuel pressure at the rail, my money would be on the CAS, or more specifically the HES. It failed suddenly while driving normally (just read the other post, possible a ground strap broke?) I would remove the CAS, make sure the drive and sensor wheel are in good shape and replace the inexpensive HES.

we seem to agree the issue is fuel, HOWEVER
the CAS controls the sparks. (if you read the wiring diagrams, its connected to the coil packs control unit)
unless there is something i'm missing ?

True enough, but the CAS sends a signal to the ECU via the HES, who knows if it is getting the correct signal at the correct time? I recall reading a while back where someone has a defective CAS wheel, which sent an intermittent/inconsistent signal. My thought process is that the CAS is easy to get to and the HES is easy and cheap to replace< just another item to check off the list.

[peteoddcar]

Look at the manuals section find Engine Management Manual look up page
EMK.2-Q
This explains the CAS and HES operation and notes that the the ignition will function without ECU inpu up to 800 rpm. Until I refreshed my memory on the system like you I’d have thought “well we must have a signal from the CAS or it wouldn’t run at all even on ether” .

Did you check the red feed 12v at the CAS and it’s ground at the plenum Earth point and the signal line back to the ECU

This failure feels like a disconnection somewhere or a complete HES inside the CAS as TUGA
Has said already

[HPMotors]

Thanks for the thoughts and replies. I have several irons in the fire right now, sorry I'm just getting back. I info-dumped quite a bit, so I'll reiterate information for the two most common questions.

CAS:
The CAS was tested for its 12v source, ground, and signal. Testing indicated that it had 12v, a good ground, and that the yellow/blue signal wire from the CAS to the ECM had good continuity. Monitoring the behavior of the signal wire with a graphing meter showed a regularly spaced, square signal pattern at close to an even 5v. I don't know if that is the correct pattern for this system, but it was steady and evenly shaped.

Fuel Injectors: Fuel Injectors themselves were given external power and ground, and they could be heard clicking or activating. A fuel pressure gauge wasn't hooked up to the rail at that time, so I could not verify fuel pressure was actually dropping (indicating they're not clogged), but I find that unlikely. I've seen that scenario only once before. The fuel injectors have 12v to them from the red/green wire with the key on and while cranking. The fuel injector signal wires (blue/yellow and blue/white) both had good continuity from the ECM to the injectors. However I was not observing an signal getting to the injectors.

Look at the manuals section find Engine Management Manual look up page
EMK.2-Q
This explains the CAS and HES operation and notes that the the ignition will function without ECU input up to 800 rpm. Until I refreshed my memory on the system like you I’d have thought “well we must have a signal from the CAS or it wouldn’t run at all even on ether” .

This failure feels like a disconnection somewhere or a complete HES inside the CAS as TUGA has said already

I'll read that section when I have a moment. I'm not 100% confident the CAS is sending a good signal to the ECM, but based off the description of what I saw (read above), it looks like something I'd expect to see.

I'll answer these in bold within the quote.

when you say it doesnt start... what do you mean exactly ?
is there any sign of explosions happening ? Without an alternate fuel source the vehicle with steadily crank, but there are no signs of attempted combustion.

what happens when you have the ignition on, not cranking. and just pull the throtle by hand ? do you hear the clicking noises from the injectors ? From what I recall, no.

is there any CEL codes ? Not on the dash, but I don't have a way of actually interfacing with the ECM.

have you confirmed that after turning the key to ignition (without starting the car) the injector plugs register 12v on 1 of the terminals (red green wire) when checking against a known ground ? Yes

your description sounds like a total failure from all the injectors operation. and since you replaced the ECU already. i would be particularly suspisious of the Red/Green wire that feeds 12 volts to them... you mentioned the ECU has power. was that 12v feed checked between a known ground and the A6 pin ? Yes
if both a6 pin and injectors dont have 12v when the key is turned. them fuse A10 or the ECM relay looks more likely... (since you mentioned all fuses have been checked, id look at the relay) Relay and fuses were checked

if you check the electrical manual v6 page 66 you can see the wiring diagram

I'll probably need to go back and re-re-re-test all this for the fourth/fifth time just to be even more certain. Part of the problem with a car being down for this long is during the testing process things get unplugged that don't get plugged back it, and things like that. The last big post I made was in regards to everything that I looked at the last time I looked at the car after the new ECM did not make a difference. I'll also have to read that section of the manual on CAS operation that was mentioned.

Thanks to everyone for the help.