my xj6 will not start

Started By: Sharon Sidoti on 2014-07-08 11:10:21

Hello, this is me again.......Ok!, did all voltage & omh testing, this time the amplifier box was bolted on, now I got a reading of 12V....the car starts, run's great....for about 5 min. until it warms up. it then dies, will not start. I once again check the voltage coming out of the amp. box, now it reads 2V, car will not restart.I unbolted the amp from its ground., voltage now reads 12V but the car still doesn't start......I'm thinkin now, new module.

Comments

Edited on 2014-07-06 23:53:57

The car has fuel to the rail, has spark to the plugs, has new fuel relay.....it seems to be lacking injector power...It starts only when the starter first engages, I'M assuming this happens because of the cold start burst of fuel. but shuts down quickly. "Why would there be no fire (power) to the injectors...? or is this not the issue at all?

What year is the car?

This has been a hat trick of mine for years.....check the ignition ballast resistor. Just about guarantee it. The reason it starts when the starter circuit is engaged is that there is a direct jump between the ignition switch , in the "crank" position, and the distributor primary feed. As soon as you release the starter function, the starter switch goes to "run" mode and runs the current for the distributor primary feed through a resistor that is designed to protect the ignition circuit in case of stall or other engine shut down. Also curious what year it is....

Try jumping the start solenoid while leaving the ignition switch on "run" if you still have a strong spark, then disregard everything I said!! Good luck!

Sorry, 1987 XJ6 4.2

If you're sure that the injectors are not operating......

Supply for the injectors comes from injector resistor pack on the RH inner fenderwell...roughly across from the p/steering pump. Check the connector, and check for 12v on the brown/slate wires at the connector with the key 'on'. If no voltage then check the 'main relay' on the firewall...as the main relay supplies the injector resistor pack.

Or....

Simply check for voltage at the injectors themselves.

If the injectors have voltage but are not operating then the ECU isn't grounding them. There are several possible reasons. First, check the white/black wire that runs along the water rail and connects to the coil "-" post. This is a trigger wire to the ECU. Also check the bundle of ground wires at the rear of the water rail, as the entire F.I. system grounds there. There are other possibilities but we can get to them later, if needed.

Your idea about the engine running briefly on the cold start injector has merit as the CSI will operate only when the key is turned to 'start'...but it will 'time out' after just a couple attempts until the Thermotime Switch has fully cooled, which can take quite some time.

Another possibility is that the fuel pump circuit is faulty. The circuit has two branches---starting and running. The pump circuit is activated from the starter circuit when the key is turned to 'start' but as soon as the key is released the 'run' circuit (from a switch inside the air flow meter) takes over.

Lastly, the ignition switch itself might be faulty....fairly common. Run a jumper wire from the battery "+" post to the coil "+" post and see if the engine now stays running.

Post back if you need more details

Cheers
DD

Colin, your advice regarding the ignition ballast resistor would be appropriate for many cars but does not apply in this particular case. On a Ser III 4.2 the ignition ballast resistor at the coil is not wired as a bypass resistor as you've described. It is in-line at all times; turning the key to 'start' does not bypass it.

Cheers
DD

Sharon, if you want to explore the possibility of a problem in the fuel pump circuit, here's some info:

http://www.jag-lovers.org/xjlovers/xjfaq/fuelpumpcheck.htm

Or click on 'Fuel Pump Checklist' below

Cheers
DD

Doug, thank you for your very patient correction of my hasty assumptions. I was not aware that the Jags ignition system was set up like that. Thanks for filling me in. Best of luck Sharon. Interested to find out how it comes out.

Doug, thank you for this priceless infor. I will get right on this and let you know the results.

Doug, The issue was the relay on the firewall, thank you....solved that issue, I now have power to the injectors......"BUT".....the car still will not start, almost, but not quite. ....I continued to trouble shoot, fuel...,check, fire at the coil...., check, fire at the plugs..., slight, not strong, a slight orange color. I followed the wiring down to the distributor, found the two wire lead from the ignition amp. to the dist. plug in a little frayed, thou I checked power at this plugin, With ignition on it shows very little power 2V maybe. with the ignition box unbolted, not grounded the power at the wires are 10V....is this normal, in my head, " Amplifier " means, increase....louder, bigger... this amplifier, (grounded) decreases voltage.????????????

I never understood why it's called an 'amplifier'.

Here's the CEI test procedure lifted virtually verbatim out of the service manual. It might help

If you have a ballast resistor at the coil you'll want to remove it for this test and attach (or jumper) the white wires directly to the coil "+" post

The test assumes a fully charged battery

1) Measure voltage at coil "+" terminal with key "on". It should be within
one volt of battery voltage. If not suspect a problem with the wiring to the
ignition switch, or the switch itself.

2) Measure voltage at the coil "-" terminal. Result should be the same as at
the "+" terminal. If Ok, go to step 3. If not....
Disconnect the wire from the amplifier from the "-" post of the coil and
measure voltage again. Less than 2 volts means the coil is faulty. More than
2 volts means the amplifier is faulty.

3) Disconnect distributor pickup coil from the amplifier (this is the
harness from the distributor that plugs into the amp). Measure resistance
across the terminals. It should be 2.2k to 4.8k ohms. If Ok, go to step 4.
If not, replace the pickup.

4) Reconnect the pickup to the amplifier. Measure voltage at coil "-" post
while cranking engine. The voltage should drop. If OK, go to step 5. If
not, the amplifier is faulty.

5) Check distributor cap and wires, distributor rotor arm, spark plugs, coil
wire

Sharon, if the amplifier is original, it is amazing, most burnt out LOOOONG ago. The remanufactured units ran an A/C delco diode instead of the original lucas. They rarely burn out once replaced.
There is also a pickup inside the distributor base as well. sometime they crap out as well. 9 OU OF 10 is the amplifier. Good luck.
The series 3 xj6 , one of the most beautiful cars ever made was one of the worst in terms of reliability.We had them all new, not for long but all new . Good luck.

The GM ignition module (not diode) inside the Lucas amplifier was used all along and not supplied or manufactuered by Lucas. It is one of those parts that is virtually guaranteed to fail. From 1974 to early 80s GM used literally millions of 'em in all of their HEI ignition system. We used to sell 'em all day long back in the day. The original part number, 1875990, is permanently etched into my brain :-)

The AC Delco number is D1906 and the most recent GM number that I can remember is 10482820. As bad as they are, the AC Delco units are still considered better than most of the other brands.

Cheers
DD

Wow! Doug, seems you know your delco/GM systems.....
Another question, power to and from the coil stands at 11/12V. Power to the Module 12V, power from the Module, 12V, except when I have it bolted/ touching ground, then the power drops to 2V. is this normal or is the power suppose to be 12V all the time, grounded or not?

It should be plug and play, don't get cute and extend the wires and box to the firewall to make things look neat, there will be an ohms and voltage drop throwing off the current, We tried years ago with etypes. Just plug and play. Good luck.

It should be plug and play, don't get cute and extend the wires and box to the firewall to make things look neat, there will be an ohms and voltage drop throwing off the current, We tried years ago with etypes. Just plug and play. Good luck.

Hello, I'm back on it... tested everything...Now, with the pick up disconnected from the amp. it tested on the plug in 00.00 0hms tested the amp at the plug in, with key off, wires disconnected from the coil it tested 0.10 across terminals....tested 0.09 from white wire to small terminal...white wire to big terminal reads 0.02ohms...white wire with black stripe doesn't measure anything on either terminal......would I be correct to lay blame on the pick-up?. Oh! I do have 11.9 v at the coil, -and+.

Hello, Ok I did all test's. just as Doug said. all my readings seem good except for one. The pick-up...with the pick-up disconnected from the amp , testing at the pick-up plug, I receive no readings, going in or comin out, I haven't a reading one. "PICK-UP"?......

Also my readings at the amp.itself reads from white wire disconnected from coil and testing at both terminals where pick-up plugs in, no readings. white wire with black stripe I read 2.95 or so...

tested resistence at the two wires coming from the pick-up....nothing. while cranking engine I tested power from both of the wires coming from the pick-up..nothing.
I pulled the coil, tested on both wires, I powered the wires, then tested ground..nothing ........... ..I think its the pick-up coil....

tested resistence at the two wires coming from the pick-up....nothing. while cranking engine I tested power from both of the wires coming from the pick-up..nothing.
I pulled the coil, tested on both wires, I powered the wires, then tested ground..nothing ........... ..I think its the pick-up coil....