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The alternator cranks out a high 14 volts, but the volt needle does go below 11 V sometimes on startup.
You are on the edge of badness voltage wise .
Below 11.5 volts on starter rotation is too low to run the ECU to start . Don B advised me as I was looking right at the gauge in the heat of battle . You can put a digital meter on the battery feeder cables in the engine compartment . Record accurately both the voltage at the battery and the engine compartment as some people have a large voltage drop caused by loose fuse hardware at the battery or under the rear seat pan . Then rotate the starter and record the total drop .
Could be a under capacity battery or the starter motor is shorting out .
I removed my starter and no obvious worn out brushes inside or carbon residue in the area and will be cleaning and hand polishing the carbon buildup on the commuter contacts in the morning .
The top starter bolt is hung from the factory ceiling and they build the rest of the car around this one %&*#* bolt .
Last edited by Lady Penelope; 05-29-2018 at 10:03 PM.
Yes, "Auxiliary Positive Relay" in trunk, near fuel pump relay.
You're right, the ECM Controlled Relay is the same as the 12 cylinder Fuel Injector Relay. I only replaced 5 relays so I double counted that.
Ignition Coil Relay is listed in RH Engine Bay (next to windshield wash relay)...but only for V-12. So who knows what the 5th one was now. I'll check tomorrow...I wasn't that careful, as you can see.
I removed, sprayed with contact cleaner, and reseated as many relays as I could easily do...next time I'm adding an anti-oxidation grease to all.
i got my A/C compressor to not work by not re-seating a relay properly...maybe a flaky relay connector. These things could cause tons of issues.
Next time I'll measure voltages around the car to see if I find a ground or short issue, Lady P. I have tried running 2 fresh batteries in parallel and the gremlin has appeared, so it's not the battery, but yes a failing starter or something could be upsetting the ECU with a large drain on startup.
Last edited by madijag; 05-29-2018 at 10:23 PM.
Reason: correction
Below 11.5 volts on starter rotation is too low to run the ECU to start. Don B advised me as I was looking right at the gauge in the heat of battle.
Just for clarity, I think generally tell everyone that if the voltage falls "much below 11 volts" while cranking the ECM will not fire the ignition. Technically, I believe the real programmed value is closer to 10.5 or 10.4 volts (per one of the the EMS manuals), but since most volt meters, including the instrument cluster gauges, cannot react quickly enough to display true cranking voltage sag, a meter reading below 11 volts or even 11.5 volts is suspect.
In removing my starter found the output side of the starter solenoid a direct short to case / car frame , this after removing the wire to the motor brushes .
My voltage during starter rotation was 9.5 from the starter cable voltage of 12.7 volts before starter engagement / rotation .
To test the solenoid without removing the starter requires removing the bottom large terminal nut ( 13 mm and a 3 inch extension ) removing the flexible short white lead to the motor brushes .Test for resistance to any ground point on the car . Wear cheap googles ( Harbor Freight ) for the stuff falling down in your eyes . May need to remove engine oil dipstick .
Solenoid mounting screws are stuck so letting them wick in some penetrate buy having it upturned with a pool of oil in the screw " well " .
Now for solenoid search . From Dallas .
Bosch original starter unit # 0 001 110 011 ( 110 series )
UPDATE: I replaced all 6 injectors with remanufactured/tested/cleaned ones. I've yet to have a no-start issue in a week. I can't say 100% certain that it was the injectors (it's possible that it was one of the relays swapped a few days earlier) but the car now starts very strong and the RPMs don't drop to 500 after startup like it used to often (randomly).
I didn't change fuel pressure regulator (got wrong part) or check valve...but might not have to anyways. The regulator was not leaking fuel.
Mileage is up to 22mpg on highway, 12mpg around town so that is also an improvement. But it'd be nice to get that to 17mpg around town as XJ6 is advertised...
I'm guessing the 12mpg is because of frequent 5-10 minute cold-engine drives.
Anyways, I'm very curious to see if this "dependable-starting" lasts for a while. The gremlin has sometimes returned after a few months (sometimes I wonder if it's the ECU "adapting" and then messing up some other balance).
I still plan to investigate voltages (from a fresh 12.6V battery, my instrument panel measures 11.5 volts on key ON, then drops to 10V on starter crank for a second before returning to 14 when alternator is running)
With the momentary drop to 10 volts may be enough time for the ECU to lose it's mind and be out of step in the starting sequence to allow a successful start . This is only theory .
My voltage would never recover , but that my be my new alternator installation .
To test specifically what I found on mine with Don B pointing the voltage drop out to me you can loop a wire on the solenoid large terminal post closest to the starter motor body . This allows easier placing the meter probe on without blindly stabbing the terminal post up in there . No need to engage the starter . But you must remove the pigtail that provides a ground path through the brushes .
UPDATE: well the car didn't have a single hiccup for 6 weeks then out of the blue, on a hot day after driving for 15 minutes, it would not restart 10 minutes later.
It took about 20 tries. The usual crank/start/die gremlin. Then after a few more tries: crank / push pedal down / runs VERY ROUGH for 20 seconds if I pump the pedal / then dies.
"Draining/resetting" the circuits by touching the positive and negative together for 10 seconds (cables to battery) is what seemed to fix the problem this time...after about 15 minutes of fiddling.
Then it ran fine for a week until today. Same problem when restarting with a hot engine. I tried "draining/resetting" again the circuits but that didn't work. I reseated a bunch of relays and fiddled with fuel pump wiring, then reset circuits again and then it started up perfectly about 15 minutes later.
When it starts after a reset, it runs as good as new right away.
POSSIBLE CAUSES:
ECU bug (but this happens with 3 different ECU's).
Electrical bug elsewhere (but I've changed coils/plugs/fuel pump/relays).
Short in starter or elsewhere causing low-voltage ECU fault.
Well, at least I know that I can get the car going again in about 15 minutes after enough fiddling with relays and battery resets
argh!
I don't think it's heat related because this happens in very cold weather too, on cold starts and in the morning - first start.
My best guess is some sensor or faulty wire gets the ECU in a weird state (crankshaft position and camshaft position sensors have been replaced. maybe cam-timing chain is slipping...would that cause ECU to stop engine?)
So once again, the mystery continues. It is not the fuel injectors. Could still be "vapor lock" or just some intermittent electrical fault.
last things I haven't replaced yet: fuel pressure regulator (I had ordered wrong part when doing injectors). But the regulator seemed OK (not leaking gas).
Have you looked at the CKPS as this sees the engine rotate giving the fuel pump the command to turn back on after the initial on - off priming of the fuel rail .That my explain your initial start then dying . You may or may not have noticed if you have the tachometer reading during the starting cycle . The CKPS can fail partially without fully failing and giving a CEL code . The full use of this sensor includes ignition and injector timing . Some have found metallic debris on the face of the sensor clouding out the air gap inductance signal and others have found a dirty connector of bad wiring after the connector .
Someone had purposely pinched the fuel return line after the FPR to bias the fuel pressure up to where it should be . I was able to return my FPR after I tried swapping the part out , depending on your relationship with the parts store .
You can swap the fuel pump relay if It's intermittent . Or you can bypass the relay control and just hotwire across the relay socket . One thing about the command signal wire to close the fuel pump relay is that it goes through the Papa Indy 61 connector position 7 as the Pink / Brown wire . This wire gives both the initial prime and the after engine rotation back on for the duration of the drive command .
Last edited by Lady Penelope; 07-09-2018 at 10:49 PM.
Tachometer always is on OK. And swapping CKPS's never fixes the problem.
car cranks at 500 RPMs, startup up to between 1400 and 1500, then idles at around 800-900 RPM.
When the car starts to intermittently fail, RPMs only get up to 1200 on startup then back down to 600RPM and usually dies. Then it becomes "always dies" in a second.
I do wonder about the connector of the fuel pump relay and its control circuit from the ECU... hard wiring the fuel pump is another future project, i guess...running out of things to try.
Talking strictly fuel pump relay command , you seem to be getting the initial fuel rail priming that is commanded by the key in the on position . This is the first 2 clicks of the relay , 0n 4 seconds then off . the 3rd click back on can be felt for as this comes from the CKPS through the ECU by same wire through the Papa Indy 61 connector position 7 as the Pink / Brown wire . This is the same wire that provides the first 2 clicks . If you get the first 2 clicks from this common wire run you should get the 3rd unless it is intermittent and throws off your troubleshooting logic .
Feel for that 3rd click if you have someone with you during a failure episode . And if not do the hotwire trick . You can use a terminal end blade connector to insert into the 2 opposite from each other sockets in the relay holder .
Their is a fuse # 10 / 5 amp RH heelboard fuse box that provides the power to control / close the fuel pump relay , the ECU provides the command ground with the Pink / Brown wire . This fuse # 10 is not provided power unless the RH heelboard fuse box king relay is closed . You can swap this relay with the LH engine fuse box king relay as this one only control the horn .
The main fuel pump power fuse is hot at all tines off the battery .
Last edited by Lady Penelope; 07-10-2018 at 12:58 PM.
11 days without a hiccup. Then this morning, after a long drive the night before and now a rainy day, no start. Cranks & cranks but doesn't ignite at all (which is different from the crank, start, die).
Tried bumping relays, resetting computer. Around 10th attempt I fiddled with wires near fuel tank (fuel pump?) and it started back up, no problem. When I stick my ear next to fuel tank i do hear some faint slushing sound... i wonder if fuel pump hose is loose again. although it runs so great most of the time I can't imagine it's mechanical...
It's late so I can't go back in the thread to see if you've discussed this, but I recall tracing the X300 fuel pump circuit through an electrical connector behind the front right headlamp. Part of the fuel pump control passes through one of two connectors in that area, which are vulnerable to water ingress and sometimes arc and burn. I wonder if the rainy conditions may have affected that connector. Parker - do you know which connector that is? I once had to repair the wiring at one of those connectors on a '96 in order to restore fuel pump operation.
Which reminds me, madijag, you could help us by adding your year, model and engine to your signature line so we don't have to guess or scroll back through the thread.
The # 1 fuel pump relay command by a ECU ground is the Pink / Brown wire on the Papa Indy 61 connector in position 7 . Have a specific pic somewhere but I think my dog ate it , really
The white connector in the 2 pics and the one being numbered is the Papa Indy 1 connector . later years production or replaced are both black . The White / Pink wire in postion 4 of the Papa Indy 1 connector is the 1st power to the ECU before the ECU can command the 2nd power source by the large ECU controlled relay.as that black ( mine white ) relay you see just fwd in the pic .
Last edited by Lady Penelope; 07-21-2018 at 08:02 PM.
That's exactly what I recall, and repairing a few burned wires at that connector restored starting and running on a '95 I repaired a couple of years ago. A few of the connector terminals were so badly burned that I just bypassed the connector and hardwired those few wires. I don't know if it's that those connectors are vulnerable to road splash or that over time owner's spill windshield washer fluid on them...
They are right behind the open gap headlight design and there was a TSB to relocate them so there must have been a early history with them . They are the same connector under the car's 4 corners that the turn signals and others go though and mine where corroded in their undercar environment . One of those undercar 4 corner connectors was cut out and tossed on mine and they twisted the wires together with some black electrical tape .
I think I solved the problem! At least for 2 weeks now. It wasn't the fuel injectors...that "fix" lasted for just 3 weeks. It started happening again and the car was to the point of not starting 25% of the time.
I detached all connectors near the fuel tank from the trunk to clean and looked at all the wires more carefully. The red wire in this photo was maybe melting from touching a hot gas tank (near fuel pump?) or just arching over 20 years.
I wrapped it up in electrical tape and no problems so far. Assuming it is the Red/Yellow powering the Fuel Pump and it would short-out on fuel tank sometimes. Maybe I'm wrong about the wire.
I wonder why the car wouldn't stop mid-drive... the only sympton was the crank-no-start or crank, start, die within 1 second.
thanks again Lady P & Don B for your suggestions. insulator melted by gas tank? shorted sometimes and caused crank-no-start sporadically.
Not able to recognize the connector in hand , I do recognize the bottom of the tank pic with the tank mounting strap . The specific fuel pump connector is only 4 wires ( for the 2nd fuel pump option on the SC engine ) and is on the very top of the tank with the large beefy flange .
Your connector in hand may be related to other items in the rank related to weither you have a 2 square charcoal canister system or a 1 canister system . Mine is a single system and you can tell what you have by looking under the car just fwd of the right rear wheel and looking for a second canister .
The connector in my hand goes up to the fuel pump on top of the tank, so that's why I'm assuming the bad wire was powering the fuel pump but sometimes enough electricity was leaking that it wouldn't turn the pump.
That top connector is different then mine as it only has positions for 4 wires . The 2 large blacks are pump grounds . The red is power for # 1 and the blue is power for # 2 if equipped on the SC engine and the # 2 does not run at all times .
A note on the connector is as the fuel pump fails the connector sockets can get burnt affecting the operation of a new pump installed . Same can be said of the fuel pump relay . This comes from the experience of Motorcarman
05-29-2018, 09:36 PM
