We continue to enjoy driving the car and attending to the mostly minor issues that are left.
Today I noticed that if I flick the switch to change the display from imperial to metric, mph to km/h then the 2-3 digit speed display appears, but in mph there are no figures.
Any suggestions?
Thinking I might need to remove the dashboard and reflow some solder?

In other news, the brakes are still good after changing the master cylinder, I had to change the other rear wheel hub due to rotating wheel studs, the hifi upgrade continues with new 3.5" Kicker speakers. Next projects include the leaky gas tank, the leak hydraulic fluid, and door seals. Heating is not up to modern standards, but after a while the temp in the car is okay. I need to look into the vacuum system there, I know there is a summer issue where the hot water valve does not close and impacts the AC, but that is not a worry right now.

 

Hi John,

Your missing digits do sound like they could be caused by the very common cold solder joint issue the vacuum fluorescent displays suffered from.

Regarding your heat, if your water control valve does not close all the way, it's quite possible that it also does not open all the way - it may be corroded and stuck in one position. If I recall correctly, on the '88 the valve is in the heater hoses and not difficult to replace. While you have the valve out, it might be worth flushing your heater core by disconnecting the heater hoses at their ends farthest from the heater core. Tie their ends up to the hood so you can then fill the heater core with CLR (Calcium Lime Rust) and allow it to soak for 30 minutes without the CLR leaking out. After 30 minutes, flush thoroughly with tap water followed by distilled water then compressed air. CLR is not recommended for use on aluminum or brass, so limit soak times to no more than 30 minutes and use at your own risk.

If you don't have a diagram of the vacuum solenoid system let me know and I'll see if I can find it.

Cheers,

Don

 

Thanks Don,
Any advice on getting the dashboard out?
I had the valve out when the AC was not working well, the valve seemed to work, but that is no guarantee that it is in the correct position now. I think I have diagrams of the vacuum system, I just need to locate it all in the real world, under the hood. The red pipe from the heater valve just seems to sneak off into the bulkhead somewhere, I just need to trace it further back - too many projects, too little time. Certainly no harm in giving the whole coolant system and good clean out, no way of knowing what all is in there right now, rust, limescale etc.

I had a look at changing the fan belts, does the radiator fan need to come off? It looks like one of the belts is too small to stretch over it? Or am I missing something?
Thanks again,
John

 

Hi John,

Removing the instrument cluster is not too difficult:

Remove the driver's knee bolster/underscuttle (apologies again that the large images are not currently available):

XJ40 Knee Bolster & Air Duct - Driver Side

I can't recall if the '88 has a steel plate behind the plastic knee bolster, but if so it will be obvious where the screws are that secure it.

Your steering wheel probably telescopes rather than tilting, so you will probably need to remove the steering column cowl, which has just a few screws on the underside and a few integral clips that hold the top and bottom halves together.

XJ40 Steering Column Cowl

The instrument cluster is held in place by two screws at each end, left and right. The screws have 8mm hex heads. One of the right hand screws passes through a metal brace inside the left edge of the center console and a nut on the screw holds the brace in place. See the tips in these photo albums for reducing the risk of losing the nut when you remove it from the end of the screw:

XJ40 Instrument Cluster / Binnacle - Part 1 of 2
XJ40 Instrument Cluster / Binnacle - Part 2 of 2

Regarding the belt, I can't recall whether the fan has to be removed, but before removing the fan you could remove the belt from the pulleys, then try slipping it over the fan a few blades at a time. If you have to remove the fan and thermostatic viscous clutch ("Torquatrol"), they are secured by just four bolts & nuts.

Cheers,

Don

 

Thanks Don,
That doesn't sound too bad for the dashboard. Pretty sure the belt is too short to go over even one blade at a time (I have used that technique before :-) ).

These tasks might have slipped down the priority list a little as for the second time in a month, she stalled on the drive home last night, while driving. This time it was going up a small hill, full tank of gas, 15 minutes into the drive. Started again on the first turn of the key, but wanted to idle too fast. I drove home cautiously (about 2 minutes) as that sure was not a safe place to leave her. Last time it was downhill approaching a stop line, so foot off the gas, easing to a stop. Took a few tries to restart that time, but had been fine ever since. I will get researching online today and under the hood tonight (in the dark looking for plug lead issues) and tomorrow.

In hindsight, the idle has always been tiny bit rough, but nothing too severe. Fuel pump always seems to be running appropriately too.

 

From those symptoms (and the fact it seems like an intermittent fault) first order of business in my book would be to check and tighten/clean the MAF connector.

Larry

 

Developments. I removed connectors, MAF and others around there, sprayed contact cleaner, put connectors back, did visual check for problems, saw nothing, added injector cleaner to the fuel tank and went for a drive.
All seemed fine for a couple of miles, so I slowed to do a u-turn and noticed it was idling a little high. Edged round when the lights changed and it was reluctant to accelerate, but eventually did. I drove to the next side street and pulled in to see if releasing the fuel cap would ease the problem. It did not and she was idling aorund 1500 rpm. Switched off to see if that would change it and then found she would not start. Foot off the gas gives endless churning on the starter but she will not fire-up. Foot to the floor and she fires, but only for seconds, will not go above 1000 rpm then dies. Worried about low battery voltage, I got a jump start from a little old lady that pulled in. Not much better, churned away, no firing. Left it for a few minutes charging and she started up fine, I think she even idled nicely. Waved away the little old lady and she died (the car, not the good Samaritan).
Frustrated I tried a few more times with foot to the floor churning and lo and behold she finally fired, revved and idled high. Limped home and into garage. Checked trans fluid (half the reason for the run to warm it up) and it was low. Added more, checked more plugs, connectors, cables and fluids. Nothing noticed. Battery was disconnected and put on charge, was reported as 12.4V, 70% charged.
This morning, she started fine and I reversed out of the garage and left her outside while running errands in another car, where I could not afford to be stranded! Returned later and took her out again. sweet as a nut, no issues driving local streets. Headed over to Autozone, bought some HEET. Drove on the freeway to gas station to top her off and add HEET. Would not restart this time.
Same again, churns, fires if foot to floor, but will not hold it. Eventually she starts and idles high. Limp home, struggling at stop lines to hold her back, hesitant when pressing the gas pedal to get going again. Home and she is still idling high, does not start after turning off.
I will go out again after she has cooled down and see if that cures it, however temporarily.
I will go read up on the fueling system. I did buy MAF cleaner and throttle body cleaner, so will read up on how to dismantle all that gubbins too.
Car did arrive with blocked drain hose on the fuel filler, a year ago, but has done a few thousand miles since then and been run pretty low on gas, so cannot imagine water in the tank is a big issue now, and surely would not cause these symptoms.

 

Hi John,

One thing you can try is to check for any stored Diagnostic Trouble Codes (DTCs). Turn the key to position II (ON) but do not crank or start the engine. Press and release the VCM button on the trip computer to the right of the steering wheel. Watch the odometer display window below the speedometer for a message to be displayed. DTCs appear in the form of "Fuel Fail" or "FF" and a one-digit numeral (two digits on 1990 and later models). Write down any message exactly as it appears and look up the definition on pdf page 113 of the Haynes Manual. You can download the U.K. edition (missing a couple of chapters) here:

Jaguar XJ40 Haynes Repair Manual

Cheers,

Don

 

Thanks Don, I will remember to check for codes next time it is doing this (big rain storm coming this week, no wish to get stranded somewhere in that, so the car might sit for a week).
Confirmed she still would not start easily after sitting for an hour last night, but did start first turn this morning. Reading up, I am leaning towards coolant temp sensor, a $20 part, so maybe I will swap that out, or just wait for the next failure then bridge the contacts on the connector with a paperclip to send the "fully warmed up" signal.

I also see discussions of fuel pressure regulator membrane rupture problems, making the mixture too rich, which is fine when cold, but flooding when hot. Not quite such a cheap part, but the car does not owe me too much as yet.

 

A simple check of the FPR is to pull off the vacuum hose and check for the presence of wet fuel, which indicates failure of the diaphragm. If you don't see any fuel, crank the engine briefly then check again.

 

Should I start a new thread, or get the title of this one modified?

Tested the FPR, no signs of gas. Water temp sensor gets 5V when running and resistance changes with temp (I think it was ~2500 Ohm cold and 280 hot).
No sign of VCM codes at any point, just runs through the available nagging/warning messages.

Today, she started after sitting for a few days, but felt like she was only running on cylinders and there was some blue smoke (not noticed that since the first day we fired her up after getting her towed home) nudged her into the garage and took the air intake apart. MAF screen was a little dirty, the solid elbow with two hoses and air temp sensor was wet with oil as was the throttle body. Cleaned everything up and reassembled. She fired up, a bit rough at first, the cleared, but wanted to run at 1500 rpm, hesitant at first to rev higher, but that seemed to improve. Switched her off, then tried to start, no go.
Took plugs out, they were black (Champion 344/RC9YC 1500 miles old) cleaned and replaced, still no go. Same old cranks and almost fires if foot pressed to floor on gas pedal, a little black smoke out hte back when she does appear to run for a second or two. Connected one plug lead to a spark plug and rested it on battery negative - cranked and got regular spark, yellow in colour.

I am going to let her cool down and hope she starts then to get her out of the garage before my wife wants her slot back.

any suggestions?

 

Hi John,

I took a stab at re-titling your thread, but if you have a better idea let me know.

My first question is whether you ever checked for Diagnostic Trouble Codes as I described in post #8? If so, did you find any? If you find one, there may be more stored, but only one will display at a time.

You mentioned that the spark plugs were black. Was it carbon or oil? Was there any oil in the spark plug wells?

Regarding the Coolant Temperature Sensor, did you measure the one with two terminals or the one with just one terminal? The former provides the fueling signal to the ECM (so it's the important one), the latter provides the signal to the temp gauge in the Instrument Cluster.

A failing Crankshaft Position Sensor (CPS) can contribute to symptoms like yours, sometimes acting up when hot. It might be worth checking its electrical connector for oil contamination and removing and cleaning the sensor itself. It's mounted on the lower front right corner of the engine (as viewed from the driver seat) and mounts with just one screw (8mm hex head?) If it becomes contaminated with grease and rust particles, its magnetic performance can be adversely affected. However, these sensors all fail with age, so replacing it preemptively is not a bad idea, since the symptoms of failure can be so difficult to diagnose. My typical recommendation to any new XJ40 owner is to install a new CPS preemptively and put the old one in the trunk as an emergency spare.

The blue puff of smoke is typical on XJ40s and probably normal. The valve stem seals leak a little oil down into the cylinders when the car sits and then burns at startup. Rarely anything to worry about.

Let us know about any DTCs, which may help narrow down your diagnosis.

Cheers,

Don

 

Don, title works for me.
When I press the VCM button, ignition at II, then the odomoeter reading stays on "Total 104001" and the Warning displays to the right cycle through all possible messages, graphics above, text below. Am I doing something wrong? I was assuming that meant no recorded problems?
I think it was carbon, dry, not wet. No oil in the wells, all looks dry and normal there.
The one with two terminals was the one I checked. front left of cylinder head, where the top hose connects. The one terminal one is there too.
I will look into the CPS next.

 

Hmmm, final update of the night. I can see what looks like it is the CPS, just below the pump for the brake booster/rear suspension hydraulic system, sort of central on the engine, above the the teeth of the crank pulley.
The connector for it is up top, big black round one, three wires, red/blue/black. Sensor is held on by 5mm allen key bolt.
Not got it out yet, access and visibility are poor and my allen key only wants to fit just before it would bump into a fan belt.

Car did eventually start again, foot to the floor, rough then running too fast, got it out of the garage and left it running for five minutes, 1600 rpm, still lumpy, almost wanting to pop and bang out of the exhaust. Tried to drive it forward and it died and would not restart. Gave up for the night.

Off to research a source for CPS and look into O2 sensors.

 

I think the '88 works just like the later cars: turn the key to position II (ON) but do not crank the engine. Press and release the VCM button and watch for a message in the odometer window.

Your symptoms are baffling, but you can rule out a few possible causes by checking for spark and fuel delivery. You can pull a spark plug, reconnect it to its wire, and ground the threaded sleeve of the plug with a jumper cable to a good ground such as one of the ground posts along the inner fenders or the battery negative post. Crank the engine and watch for strong spark.

Testing for fuel pressure is a bit inconvenient on an XJ40 because there is no Schrader valve on the fuel rail. But it's fairly easy to disconnect the fuel line from the inlet (firewall) end of the fuel rail. IIRC, it requires two open-end or flare-nut wrenches of slightly different size (21 mm & 19 mm or 19 mm & 17 mm?). Aim the hose into a catch container and have an assistant crank the engine. There should be a steady stream of fuel ejected from the hose. If you have a fuel pressure gauge set, it may contain an adapter that can fit the fuel hose so you can test the pressure from the pump. Intermittent fuel pump operation can be caused by a failing fuel pump relay, or, on some models, a failing oxygen sensor relay.

Sorry for all the info - I'm not trying to send you on wild goose chases. Hopefully you'll find at least one code stored in the VCM.

Cheers,

Don

 

I guess what I need then is confirmation of what happens when you press the VCM button and there are no stored codes, does it present a message, or just leave the mileage displayed? Maybe there is another dry solder joint on the dash (see lack of 2 digit MPH figure above) that hinders the VCM codes?
See above, I did the spark plug test, spark seemed regular, but a little yellow in colour. Should I be replacing the coil?

I guess I can test the fuel flow as detailed, but I do note that I can hear the pump run for 1-2 secs when the ignition turns to II and that there is enough fuel to keep the engine running at 1600 rpm once it does start.

All info is good info, rarely is there too much, so keep it coming.
Thanks,
John

 

I see Haynes says you need JDS/oscilloscope to test the CPS, do we think this would work/give meaningful results?

Testing a Three-Wire Sensor:

• Once you identify the power, ground, and signal wires using your vehicle repair manual, test the sensor’s circuit by setting your multimeter to “DC volts.”
• Have your helper turn the ignition key on, but don’t start the engine.
• Touch the black probe on your meter to ground (a metal bracket, bolt, or metal surface on the engine itself) and the other probe to the power wire. Compare your reading to the specification in your manual.
• Have your helper crank or start the engine.
• Touch the signal wire with the red probe from your meter and the ground wire with the black probe. Compare your reading to the specification in your vehicle repair manual. If the voltage signal is lower than the specification, or no signal comes out of the sensor, most likely the sensor is bad.
• Remove the sensor and inspect it for signs of physical damage or contamination.

 

If you press the VCM and see the mileage re-display without any codes, then you have no codes stored.

HTH

Larry

 

If this were my car, I'd swap the coolant sensor and unplug/replug the ecu plus check coolant sensor harness and connections. Make sure there is no dielectric grease in any sensor connectors. Look again for vacuum leaks.

The coolant sensor is very affordable and can cause re-starting issues like this.

Larry

 

Thanks Larry, that does indeed help.
Just for 100% clarity, I would not say it re-displayed (suggesting some flicker or change) the mileage, just that the display never changed? Agree or disagree?
Cheers,
John

PS Autozone only want $487.99 for a new CPS - I think I will clean and check mine, I can see some dirt build up and maybe hydraulic fluid leaking from the pump above. Suggestion is the hex bolt is 5/32, I will look for a socket mounted allen key and use lots of extension to be able to wrench it from above the engine.