Hi,

I'm working on a 1985 XJ6 that is currently not starting. I've been reading through past posts on the forum but still have a couple of questions as far as what I've found from testing certain components in the fuel system. First off, I'm getting spark, fuel, and a pulse at the fuel injectors (confirmed by a noid light). When I started working on the car, the noid light would flash as the engine was cranked, but very dimly. I noticed the wires on the coolant temp sensor because they were frayed and in pretty bad shape. I removed the connection and jumped the two wires together. Upon cranking the engine the noid light would no longer flash at all with these wires jumped together. When I separated them and tried to start the car, the noid light flashed brightly but the engine still wouldn't start.

I've also connected in a fuel pressure gauge to the line going into the back of the fuel rail. So far, I've only been able to get a reading of no more than 20 psi, which seems low. From what I've read on here it should be more like 34 psi.

I also went and cleaned all of the grounds and most electrical connections in the engine compartment. The car will run on starting fluid so I guess my next question would be should I replace the fuel pump? It's obviously delivering fuel but there isn't enough pressure at the fuel rail.

Thanks in advance,
Dave

 

Welcome to the Forum, Dave.
I've moved your post to the XJ6 section where you'll get more help.
Please take a moment to visit
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Out of curiosity: have you replaced the fuel filter yet?

 

Hi,
Yes, the fuel filter is new. I replaced the pump as well but it was a cheap aftermarket one that I got off of ebay. I'm wondering if the pump just isn't any good.

 

was it running before you replaced the pump?

 

It hasn't run in a couple of years. I had both fuel tanks cleaned and sealed since the fuel was pretty nasty when I drained them.

 

you might have to do a thorough cleaning of the fuel lines too, they might be gummed / clogged as evidenced by the low pressure at the FPR. Also you might need to compare specs from old pump to new pump. Best to stay with the original spec pump.

is the new fuel filter correctly oriented?

 

The fuel filter is in correctly according to the arrow marking on the outside of it. Any thoughts on how to clean the fuel lines out? The place that I purchased the pump from told me to try reversing the polarity at the fuel pump and see if that helps. I doubt it since I'm getting some fuel pressure though.

 

you would flush the lines with air under high pressure from both ends, (from the tanks out, and from the engine out);

have you checked the Inertia Fuel Cutoff Switch? it's a black box located in the passenger side, behind the bottom edge of the dash, you'll need to remove the trim pieces on the side and below the dash to see it. Sometimes they tripp if you do not de-pressurize the fuel system before opening it up, for example when you removed the tanks and then tried to start the engine. There is a Reset button on top of the black box, push it down to see if it "clicks" when you push it, otherwise it should spring up when you stop pressing it. If it clicks when you press it, it had tripped and the engine will now start after a few tries.

 

I'll check the inertia switch. I had forgotton about that! I'm out of town this week but will see if my brother can go out to the garage and find that switch.
Thanks!

 

The car should still start with the coolant temp sensor disconnected right? My understanding is that it will now be set to a full rich condition with the sensor unplugged. That's the only way that I can get a good injector pulse.

 

I never tried that trick, sorry. Check the Cold Start Injector too, if you unscrew it from the intake, holding it face down, and then someone else cranks the engine, does fuel come out of it?

 

No.

In fact, if the engine was running and you unplugged the CTS the engine would die *instantly*.

Jumping the terminals inside the CTS plug, as you mentioned earlier, simulates an engine at normal operating temp....and the engine should run. No injector pulse with the CTS jumpered is weird. Not sure exactly what it means, but it ain't right.

Cheers
DD

 

"Getting fuel".....means the pump is working you have fuel pressure at the fuel rail, yes?

Just checking.

If so, the inertia switch isn't a problem as it cuts off the fuel pump circuit.

The injector pulse thing is strange. Has you checked the bundle of groud wires at the rear of the water rail? These are critical to the F. I. system

Cheers
DD

 

Hi Doug,
I unbolted the ground wires at the rear of the water rail and cleaned them. I can't figure out why the noid light flashes brightly with the coolant temp sensor completely unplugged. When I plug it back in the noid light gets really dim and when I jump the two wires I get no injector pulse at all.

Yes, it has fuel pressure at the rail. It seems like it would still start with lower fuel pressure, just not run very well.

Jose,
I'll check the cold start injector when I get back.

Thanks for the replies!

 

I surely don't have a snappy answer for you :-). I'll have to do some mulling. Just had 4 teeth pulled so my mulling skills are limited at the moment.

I suspect a wiring or ECU fault....but what exactly, I can't say. ECU problems seldom occur....but seldom isn't the same as "never"

I'd inspect as much of the CTS wiring as possible, and carefully.

Cheers
DD

 

I appreciate it Doug. I'll do some more checking on the wiring when I get back into town on Friday. I do have a spare ECU somewhere for this thing but will have to locate it.

 

Well I got the car started. I ended up repairing the connection at the coolant temp sensor and that got it going. The car would run for a second or two with the wires jumped together and with them totally disconnected. It wasn't until I repaired the connector and plugged the coolant temp sensor back in that it would run. The fuel pressure is also showing around 36 psi now. Thanks again to everyone for their help!

 

congratulations, something so simple and yet so puzzling. Amazing how much power that Coolant Temp Sensor has over the engine!

 

It sure surprised me. I repaired the connector for now but was looking at replacing the FI wiring harness eventually. I think britishwiring.com is selling them for a little over $400. The car runs surprisingly well though for having sat for so long.