Brief update...

haven't had much time to work on the car.

Forgot to check air gap; will do tomorrow

Installed new coil and have a much stronger spark at the plugs. No change in the root problem, though: no injector pulse. I wasn't expecting otherwise, to be honest.

Have done quite a bit of continuity testing on wires to the ECU. Nothing abnormal so far. More details on this later. I have some questions.

In noodling around I checked the TPS. Voltage range is about .43v to 4.5v. This is out of spec and will be addressed but I don't think it accounts for flat-out inoperative injectors. Does the group agree?

Removed injector harness, bench-tested continuity on all wires; nothing abnormal found. The PO had rebuilt the harness a few years ago. I wasn't hoping, but not really expecting to find a problem. Had to check it off the list, though

Will check the power resistor as well. Having a hard time imaging all four resistors going on the blink at once. Perhaps a poor connection at the plug or some such? We'll see.

Also wondering about a dead ECU but it's low on my list. I'm still suspecting a wiring issue related to the transplant of the entire harness.

Cheers
DD

 

Doug,

That TPS reading MAY just be at the fuel cut off area of the ECU, I simply dont remember the numbers, but it is NOT far from idle in crank mode. Thats why people that habitually "touch" the throttle whilst carnking report hard to start engines.

I am also thinking that Pin#26 of the ECU has a wire FROM one of the C1/C4 terminals of the starter relay. This is to "by-pass" the shielded wire ONLY during cranking, and wakes the ECU up and activates the Injector Pulse needed for starting. Once running, and the key returned to the Ign position, the shielded wire pulse to Pin#18 takes over.

They will start, EVENTUALLY, without that Pin #26 boost, but it is tough on the starter motor.

 

Been busy.

Update....

Installed a used ECM and now have injector pulse ! Noid light blinks happily when cranking

However.....

All is not well. Engine still refuses to start. Interestingly, with the key 'on' the injectors do not respond to opening the throttle. I will revisit the TPS situation.

For the heck of it I dribbled some gasoline into the intake manifolds and the engine fired right up and sounded smooth and great. I needed that

More later

Cheers
DD

 

Does the fuel pump do the 3 second prime when you turn the key to on (not crank)?

 

Yup!

Speaking of fuel pumps, mine decided to gush fuel via the crimped end of the case. Gah, what a mess. But that's incidental to the issue at hand. I have a new one coming.

I remain perplexed but feel that I'm getting closer. As mentioned I'll do more checking of the TPS-end of things. Hopefully something will be revealed.



Cheers
DD

 

Interestingly the owner's manual suggests doing just that---slightly opening the throttle on start-up. It's contrary to usual practice with F.I.


Continuity is good from the relay to pin 26 but I didn't check the signal itself. Something distracted me (paying work, I reckon). I don't suspect a problem, though. The wire to pin 26 shares the same terminal as the white/red starter wire.....and the starter always engages. Still, I'll go back a check just to satisfy myself.

Cheers
DD

 

Also, I will check fuel pressure, on principle, after the new pump is installed.

Cheers
DD

 

Doug,

I know you know most of this, but I found this document interesting reading, and there are a number of tests for various conditions. Lots of specs given too and step by step instructions for setting up the V12. Hopefully some of it will be of use. It's publication S58:
http://www.jagrepair.com/images/Elec...ance%20S58.pdf

 

I've had a no start when a pressure regulator failed, so the pump pressure bled off and the fuel went right back to the tank.

 

I have it, thanks

Cheers
DD

 

For kicks I bypassed the inlet regulator, no change.

The rail is holding at least 'some' pressure....as I get a fair spray when cracking the fitting. A pressure test will reveal meaningful info.

Still, though, I'm left with the issue of no injector activity when the throttle is actuated with the key 'on'. The injectors should click.

Cheers
DD

 

I didn't think the injector actuated until there was a signal from the ignition?

Maybe just to eliminate the possibility of a bad harness, try stringing an external wire from the amp to the ECU pin 18?? Cable TV wire would work well if you wanted to go shielded.

You said you have spark, you have fuel pressure, so all that is left is the ECU communicating with the injectors.

Is the vac line to the ECU in good shape? I don't think a no vacuum signal will cause a no start, but not sure.

 

Another wild thought - is the ignition switch good? Does the amp get power in both crank and run?

 

Pin 26 is cranking enrichment. I have good continuity on that wire


I have good continuity in the wire to pin 18 and have confirmed it isn't grounded. However, apparently I can't check the actual signal since I don't have an o-scope.

However, I do have injector pulse while *cranking*...which suggests #18 is getting a signal.



Spark yes. Fuel pressure exists, yes, but....unknown amount. To be determined.



I'm still hung up on lack of pulse when actuating the throttle. I can't help but think that's a clue.



Yes, the line in brand new and intact and secure. I think a disconnected line would give rich running

Sooner or later I'll narrow things down

Thanks for the input !

Cheers
DD

 

Hmmmm.

Haven't checked that, specifically.

If I give several good squirts of raw fuel into the manifolds the engine will run for a few seconds with the key released, so I'm thinking I'm OK.....

But it merits investigation


Thanks
DD

 

What about the main relay? Is it closing as it should? I'm thinking that since it ran when you poured fuel into the intake it must be on the fuel delivery side, only one of three things:
-ground to the injectors through the ECU and power resistors,
-power to the injectors,
-lack of fuel/fuel pressure.

I can't see it being anything else, the ignition side must be good if it ran when fuel was added.

 

Further thought: Noid light shows injector pulse now. So in theory the injectors are firing, and the plugs are sparking? I wonder if the coolant temp sensor is bad, and the ECU isn't enriching enough to start?

 

Main relay good, it powers up the ECU and provides supply voltage to the injectors, all confirmed.



Coolant temp sensor is new (replaced on GP as part of the swap) but I haven't actually checked it. However, continuity to ECU is good.

Injector ballast OK as well. Exactly 5.6 ohms on each resistor and good connections. (I don't know what spec is, but since all four came in at exactly 5.6 ohms I figured that's OK)

All wires to ECU have been checked for continuity and are Ok as far as *that* goes. I haven't checked all of them for signal or output. Not sure how I would check "Injector on" pins and "injector hold pins".

All pins pertaining to ECU power and ground have been confirmed

Haven't done any checking WRT oxygen sensors as they're 'disabled' when gearshift is in "P"

Thanks for hanging in there with me

Cheers
DD

 

Sounds ok to me 5.6R + the Injectors about 3R would give the injectors 1.3amps to keep them open.

O2 sensors are disabled in ECU program until they are warmed up. So unlikely suspect.


Are the injectors clean? You can test them with a 9v battery a large syringe and carby cleaner. Don't leave them energised too long or they will get hot.

Next for me would be fuel pressure.

 

You've helped me lots over the years over on J-L, so it's the least I can do. Another look at things never hurts.