electrical problem needs solving

[kergiva]

Hi, I have a 1989 auto GQ. 4.2 petrol (70 lts) and gas

(100 lts) petrol. 380k klms. Reco trannny 60k. 5k ago new high tension spark leads, points, condensor, rotor button, dissy cap, bosch coil with resistor, gas plugs . Set correct timing at 10.. Duel batteries both new. New Earths. Showing 13.9 v give or take. Alternator charging at 14.2 give or take. Alternator is 3 years old and replaced regulator 1 year ago. Had bench test and ok. My carby reconditioned(in good condition) 6 months ago. Bosch coil giving 10.9v give or take.When I start car alternator lights stay on until I rev car. Didnt do this previously but auto sparkys and a couple of good mechanics says thats ok as some alternators do this. Plugs giving approx 1.2 when should be higher. I have run power straight to coil and lifted spark to plug approx upto 1.5 and slightly higher. When I start car and drive its smooth. 5 minutes down road it runs rough(missing) Fine when it kicks down but once cruising it starts to miss. I am occasionaly getting a pop as in mild backfire. Not from rear of car but front to middle. It is not consistent but when up to approx 100klms per hour it starts to stutter. Kicks down and goes through gears and when it reaches end of gear and goes into cruising it stutters. It is the same symptoms on both fuels.

My gas mechanic would like to see a stronger spark. I have a Bosch coil made for a resistor and another mechanic suggesyed running a straight 12 v coil. I am uncertain if the the resistor is related to my problem but today I put a new replacement coil on and same symptoms happened. I believe its electrical but not sure where to go from here. I suppose I am only looking at electrical but it may have a mechanical aspect also. If anyone has any knowledge or ideas I would love to hear. Thanks Ian.

[patch697]

G/day mate & welcome to our merry band of Patrol nuts...lol We are a pretty happy bunch here so I hope you enjoy the forum.

Mate nice detailed post BTW.

Ok I know you only changed them 5k ago but go put a new set of points in it. The TB42s have a real bad history of short points life ( A well documented fact) around 4 to 5000k & thay are pretty much shagged so for the sake of $10 get a new set & let us know how that go's

Set them at 16 to 17 thou (38 to 40 degrease dwell angle) trust me on this.
& adjust your timing to 12 degrease.

also check & clean the pins inside of your distributor cap & the tip on the rotor button as I suspect thay will be in need of it.

Post back here & tell us how you get on.

Cheers
Paul

[kergiva]

G'day Ian. Sounds like a fuel issue to me (OK when the pedal's down but rough when you back off and cruise).

Is your carby balanced properly?

Are the carby fuel jets adjusted properly (not running rich or lean)?

Good to have you on the forum mate. Post up an intro and tell us about yourself and vehicle in the "Introductions" section.

Cheers mate.

Gday. First time been on a forum and thanks for getting back so quick with info. Carby recon 6 months ago and problem was not there when carby recond. This would lead me steer away from the carby but may need to considered. Problem on petrol and gas. I have checked the vacum advance with my gas guy and its good. I have a small amount of slack in dissy. I have looked at getting rebuilt but my mechanic and his auto electrician dont think this is the cause of the rough running. (These guys are really on the ball) It is something that could be done but I am hesitant to keep putting money where its not needed first. Thats why I need to find GQ enthusists like your self who have more knowledge about the Patrol. Its not a lifted and customed off roader but its close to original. It gets used up in Fraser Island and other camping areas around SE Qld and basicly its the family car so Im keen to keep it running well and reliable. Had it for nearly ten years and its the best car Ive owned.
I have replaced all carby vacumes and fuel lines, even fuel filler pipe(bowser to fuel tank) and all heater hoses, new radiator 12months. Its a car I want to keep so its the next learning curve Im on.
Strange that it drives beautiful until 5-10 mins when its warmed up. Then its occasionally pop fire (Ill call it that) and it runs rough on low cruising revs and high cruissing revs but not always. This symptom is where I need to start. Valve springs worn??Something in the motor?? Any ideas Id be grateful, Cheers Ian.

[kergiva]

Hi Paul,
Great advise and thanks. I am thinking, instead of new points that I put some money into reco dissy and put electronic points. So If I do one or the other it will be one less item to cross off the "maybe the problem list".
Ive got a new set of Nissan points in the spares box i keep and that would be a smart move to try them first. Gratefull for your knowledge, Thanks Ian.

[patch697]

Gday. First time been on a forum and thanks for getting back so quick with info. Carby recon 6 months ago and problem was not there when carby recond. This would lead me steer away from the carby but may need to considered. Problem on petrol and gas. I have checked the vacum advance with my gas guy and its good. I have a small amount of slack in dissy. I have looked at getting rebuilt but my mechanic and his auto electrician dont think this is the cause of the rough running. (These guys are really on the ball) It is something that could be done but I am hesitant to keep putting money where its not needed first. Thats why I need to find GQ enthusists like your self who have more knowledge about the Patrol. Its not a lifted and customed off roader but its close to original. It gets used up in Fraser Island and other camping areas around SE Qld and basicly its the family car so Im keen to keep it running well and reliable. Had it for nearly ten years and its the best car Ive owned.
I have replaced all carby vacumes and fuel lines, even fuel filler pipe(bowser to fuel tank) and all heater hoses, new radiator 12months. Its a car I want to keep so its the next learning curve Im on.
Strange that it drives beautiful until 5-10 mins when its warmed up. Then its occasionally pop fire (Ill call it that) and it runs rough on low cruising revs and high cruissing revs but not always. This symptom is where I need to start. Valve springs worn??Something in the motor?? Any ideas Id be grateful, Cheers Ian.

The TB42s have a bad habit of going tight in the tappet clearance on LPG & should be checked around every 15000k. Its also a good practice to set the tappet clearance 1 to 2 thou bigger than STD when running on LPG as well.

RE my last post check the points? if thay are 5000k old I bet thay will be burned. This is one of the most common problems in these models.

another thing it sounds like it could be is a bad wire in the ignition system. As all wire ages it deteriorates & builds up resistance which will course signal loss (voltage dop) the resistance builds as the wire gets hotter.
It may pay to have it checked for this as well.

As for your distributor? Contact these ppl thay specialize in TB42 distributors & also have an HEI option available which will give you a cracker spark & no more points.

Performance Ignition Services. 03 98723644

Thay ship anywhere in Australia

Cheers
Paul

[Bernard]

Hi,

The is a contact on the ignition switch which holds in the voltage in run mode to the resistor through which the coil is powered. A simple test would be to put a voltmeter on the ignition side of the resistor supplyinmg the coil. If the voltage progressively drops as the engine runs, than the problem may lay in the contacts in the ignition switch. If the relevant contact was poor, it could heat and progressively drop the available voltage to the coil until there was insufficient power for the coil to operate. Check the ignition switch and connections to it. With the car batteries disconnected, place an ohm meter across the closed contacts in the various switch positions - these should be effectively zero. (Ensure meter is zeroed first). Note: If you do not disconnect the battery(s) before making this test with an ohm meter you could destroy your meter.

[lostmav]

contact LPgas1 in the yarra valley i think, they make a modified rotor button for LPG motors with a smaller air gap works well, it,s no good fitting new cap points and coil if u have a stock factory rotor button
cheers Lostmav
p.s vl commodore cap fits GQ tb 42 i'm looking into the rotor button!

[YNOT]

contact LPgas1 in the yarra valley i think, they make a modified rotor button for LPG motors with a smaller air gap works well, it,s no good fitting new cap points and coil if u have a stock factory rotor button
cheers Lostmav
p.s vl commodore cap fits GQ tb 42 i'm looking into the rotor button!

I think lostmav has the right idea.

Tony

[patch697]

Performance Ignition Services do extended rotors as well thats why I gave him the advice to speak to them.

Check out this thread I've put up some pics to show there work.

http://www.nissanpatrol.com.au/forums/showthread.php?299-Information-on-TB42s-extended-roto


Cheers
Paul

[kablea]

Dont kno if this is solved or not, but my car did this,
It was cause there was a crack in my radiator, very fine, used to mist out, and run down chassi
it looked like aircon water till i moved her one day and realised it was a bit green. Just a thought.,

Aaron.

[Bigcol]

I had a similar problem with my son's car
did the old school way to find it

wait untill very dark, run motor, and run a long handle screwdriver over ALL leads & coil lead

found a small spark jump from front of the coil to the screwdriver - hairline crack on coil, as it got hot, crack expand, loosing power as it arced elsewhere


cheers

[ablast]

As rare as it may be I had a very similar problem a few years ago. After much deliberation and the replacement of many parts it was an intermitent falt with the resistor in the distributor. In almost all cases they either work or they don't. Just a thought and not likley to be the problem but worth checking. Hope it helps.

[-ET 4wd-]

A man after my own heart Bigcol!!...geez that brings back memorys!...and it works a treat as well!

Steve.

[-ET 4wd-]

I would be lookin in the direction of the coil!!
I put a aftermarket GT40r on my Gq ( when t was still a 4.2) and found it ran a bit worse when cold, and missed at higher RPM when hot.
I went back to a newer secondhand stock one and never had a prob again.
And all of this was with a petronix kit in the dizzy as well.

Steve.

[ablast]

It sounds like a timing/electrical problem to me. If your dizzy-cap has no cracks or corrosion and your coil is not breaking down under load then I'd be looking at the distributor itself. Just a thought- (It is very rare but condensers can break down under load too and they are cheap to replace to discount it as a problem.

If all else is new and good, the dwell angle is correct then I would be looking at a possible worn cam on the distributor. I have had this problem and it was frustrating to diagnose as the distributor concerned had only been rebuilt eight months earlier (obviously not properly). It certainly sounds like a timing problem. Check that there are no leaks on your vacuum advance although I doubt this would cause the severity of the problem you describe.

Hope this helps.