OK, the engine will turn over but not start. Here's the results of my crude diagnostic tests.:

1) I disconnected the gas line in front of the battery, cranked the engine and a healthy flow of gas came squirting out.
2) I disconnected one end of the fuel regulator (? The small barrel looking thing at the far right end of the fuel rail) cranked and fuel squirted out3) reconnected the fuel regulator , disconnected the other end, cranked and fuel squirted out.
4) I DIDN'T disconnect any of the short, rubber hoses to each injector as I believe they are pushing gas to each injector
5) I removed each spark plug, cranked and observed a good spark. I did this after attempting to start the engine for 15 minutes or so and each spark plug was bone dry
as a side note, in the past when I have gotten the engine to run, it has very good acceleration and idle. I can shut it off and restart it on demand throughout the day, even letting it sit for hours. However after sitting overnight, the crank/no start problem returns in full force. It has been several days since I got it to run. And yes I am aware of putting it in gear, running the fuel pump then returning it to park/neutral to engage the starter

Any suggestions for another diagnostic test? I have been told to go to harbor freight and purchase a current clamp to verify if the injectors are receiving voltage at crank?

I would greatly appreciate any suggestions.

PS: full disclosure, I have replaced all the sensors screwed into the coolant rail next to the fuel rail with several sensors salvaged from several xj6s. I have also swapped out a couple of cold injector sensors.

 

Well, we know you have spark---good.

And we know you have fuel supply--good.

We don't know if you have correct fuel pressure. But we'll set that aside for the moment.

We don't know if the fuel injectors are operating. I would verify yes/no on this and go from there.

A noid light.....




.....will tell you if you injectors are getting the power/ground they need to operate. You can buy these inexpensively or many auto part stores will rent/loan them. Alternatively, use a mechanic's stethoscope to listen for the injectors clicking while trying to start the engine. Or even a long screwdriver held to your ear.

If your injectors are not clicking......

Use a test light or meter to check for voltage to the injector wires. Both wires to each injector will show voltage with key on, engine off. If no voltage suspect a problem with the main relay, the injector ballast, or the wiring and connectors.

If you have voltage but no click check the bundle of black ground wires at the rear of the water rail, under a bolt head. You'll see 'em...about a half dozen wires. Make sure the grounding point is clean and tight. Also, at the coil "-" post is a white/black trigger wire running rearward. Make sure the wire and connection is OK. Without this "trigger" from the coil the fuel injector will not operate.

On general principle check/repair the ducting from the Air Flow Meter to the throttle body. In your pic one of the clamps is missing at the black accordian bellows. Air leaks along this tract will cause problems....although perhaps nothing to do with your no start situation

There may be more to this journey but the above is a good stepping-off point

Cheers
DD

 

Thanks Doug. This is the "next step" information I was hoping to get.

I'm assuming fuel pressure is not the issue judging from the healthy volume of gas that poured from the disconnected fuel line in front of the battery and the solid flow at both ends of the barrel shaped fuel regulator (?)

 

Not a correct assumption :-)

A healthy volume of fuel flow doesn't prove that the pressure is correct.

Correct fuel pressure is important but in diagnosing a no-start checking that the injectors actually operate comes first.

Cheers
DD

Cheers
DD

 

Assume? No. check and verify.

I will not restate the old axom that goes wit assume..

 

I stand corrected once again. I figure out how to check the fuel pressure at the rail

 

Remove the hose to the cold start injector. The now-vacant nipple on the fuel rail is where you attach your pressure gauge. Spec is 36psi while cranking. Running pressure varies +/- 2-3psi according to vacuum.

Cheers
DD

 

Thanks Doug. I will go buy a fuel pressure gauge.

I just finished swapping out a salvaged air flow meter making sure all bands were snug. Same result, crank no start.

I'm on my way to secure a feul pressure guages and the noid lights.

I will report back with results. Probably not today as my patience is wearing thin

 

And it just started with a cold rain and the car is outside of course. Gonna have to push it inside before it snows in Michigan

 

Those 'noid' lights are really useful. The injectors are fired all together twice per engine revolution. There is a constant 12v supply to the injectors and the ECU grounds them to make them fire. The resistor pack is to protect the transistors in the ECU. A single white wire off the coil goes to the ECU and provides a pulse. Without this pulse the ECU will just sit there and not fire the injectors

 

Thanks Fraser for the explanation. I borrowed the noid kit and a fuel pressure gauge from oriellys. Hopefully it stops raining tomorrow so I can run these tests and report the results.

 

Fraser, great explanation. My understanding is that the resistor pack also prevents injector coil burnout, as it takes a belt to get them to open, but after that they need far less current to keep them open.

 

You may well be right on this. I'm going on what Roger Bywater wrote on the L-Jetronic EFI system on the XJ engine.
Fuel injection and the Jaguar XJ6 4.2 Series 3 / AJ6 Engineering