XJ6 & XJ12 Series I, II & III 1968-1992

1985 XJ6 4.2 Series 3 Cranks, but No Start

 
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Old 07-13-2014, 08:04 PM
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Default 1985 XJ6 4.2 Series 3 Cranks, but No Start

Hello all,

I have a XJ6 4.2 series 3 that turns over great, however will not start. It was running fine, I parked it, and then in the morning it cranked without starting.
During the period that it has been running I replaced the plugs, plug wires, distributor cap/rotor, all belts, fuel pressure regulator, changed oil/filter, drained fuel from both tanks and installed new fuel filter. Ran great for weeks after this series of maintenance.
While troubleshooting the no start condition I cleaned all ground wire connections to body, determined that I do have spark, and that there is fuel spraying out of the injectors. I jumped the fuel pump relay and the pump turned on and fuel reached the injectors and sprays out. The cold start injector operates properly as well (12v~ to the cold start injector and fuel sprays out of it).
I checked for compression and all 6 cylinders were within specification.

I am properly stumped!

Thanks for any help!
 
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Old 07-13-2014, 08:49 PM
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Originally Posted by twocross View Post
determined that I do have spark,

A nice, fat, blue spark? Or a puny, pathetic orange spark?



and that there is fuel spraying out of the injectors.

How did you check this?



I am properly stumped!

Yeah with fuel, spark, and compression it really should be running. A hiccup, at least!


Cheers
DD
 
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Old 07-13-2014, 09:09 PM
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The spark was checked two ways; first way was with an inline spark plug wire light, it was illuminated intermittently just like it should have when the rotor came around to the point in the distributor cap. Second way was to remove the spark plug and observe it arc while turning it over. The spark when it was arc'ing appeared strong and bluish.

I check for fuel spraying out of the injectors by removing the pair of injectors nearest the firewall at the rear of the engine. I pointed them up and as I turned the engine over I saw them squirt fuel.

It has a sound while it turns over almost like its not in time, but I have never had a car run well one day and be out of time the next. I have not yet checked for fuel pressure.

Thanks for the quick responses.
 
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Old 07-19-2014, 04:41 PM
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Default UPDATE to NO START

Upon further inspection:
I turned it over in an effort to verify fuel reaching the cylinders. After turning it over a few cranks I removed each spark plug and each of the 6 plugs was dry as a bone, and with a light I looked down into the cylinders and the tops of the pistons are also dry.
There is 12v reaching each injector.

Not sure if this is related, but worth a mention. When I first got the '85 XJ6 I changed the oil and when I went to start the car it didnt start. I double checked oil level and topped it off. It started up just fine. I noticed today that the "oil light" on the dashboard is illuminated.
Could the no start problem I am having be related to the oil pressure switch that is near the oil filter?

Turns over, strong spark, and 12v to the injectors, but the plugs are dry after turning engine over.

Must be something simple that I am over looking!
 
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Old 07-19-2014, 04:52 PM
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Sounds like the injectors are not being grounded by the ECU. A few EZ checks to begin with:

1) At the end of the water rail is a bundle of ground wires under a bolt head. Are they all clean and tight?

2) From the coil "-" post is the white/black wire that runs along the water rail. Is it in good shape? This is a 'trigger wire' to the ECU

3) Remove the plug from the coolant temp sensor. Use a paper clip to jump the two terminals inside the connector. Try starting. Does anything change?

Cheers
DD
 

Last edited by Doug; 07-19-2014 at 07:05 PM. Reason: sp
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Old 07-20-2014, 03:10 PM
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Followed the 3 step process of cleaning the ground wires on the water rail, checking the "-" connection of the white/black wire from the coil, and removing the plug from the coolant temp. switch and jumping the connector.

Did all of the above and still no start. I double checked the white/black wire for ground by using the "+" terminal of the battery and with a multimeter grounded it out on the "-" coil post, and I got 12.5v. I disconnected the bullet style connector for the white/black wire and cleaned it. Also using the battery I grounded out the battery on the female and male ends of the bullet connector and got 11.3v. I then followed the wire back to the firewall, and disconnected the multi-wire connector and grounded the battery to both female and male ends of the connector and got 11.3v. If I go across the "+" and "-" terminals of the battery I get 12.5v.

I cleaned all ground wires and ground straps that I could find and cleaned them with a wire brush or sandpaper, and put a thin coat of di-electric grease on all connections.

Fun fun fun
 
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Old 08-04-2014, 10:54 PM
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Quick update to the non starting '85 XJ6.
New fuel injectors installed a few days ago.
While doing some under the hood cleaning I noticed that the ignition coil was leaking it's oil out. I have a new one on order, and it'll be here this week. In an effort to solve the riddle of the no start condition I have found an XJ6 at a local junk yard that I will go to and get as many of the components of the fuel injection system that I can.
Still no start after further cleaning and new injectors (thought the old ones may have been clogged).
 
 
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