View Full Version : TR6 Newbie with a TR6 engine problem

06-07-2006, 07:42 AM
I have a mystery going on in my TR6, and I would appreciate some advice.

I have a 74 with 70000 miles. I've never had any engine problems. The other day I put about 100 miles on it, I was going 70 on the freeway, got off at an exit and when I started again the engine was fine up to 2000 RPM and then would sputter and fight going over 2000. I couldn't go more than 15 MPH.

I replaced the spark plugs. I checked the vacuum hoses and they all look attached and ok.
The contacts on the distributor cap look a bit worn, and I plan on replacing it. The distributor points look ok.

A previous owner put a booster fuel pump on the line from the tank to the primary fuel pump. This pump comes on when the key is in the auxilliary position. I'm not sure why this was added. I checked the filter in the primary fuel pump and it looks ok. I haven't checked the fuel filter yet.

The carb damper oil pots seemed ok, there was oil and pressure when pushing the needles back in. I have never tuned the carbs in 6 years (15000 miles). The air filters are a little dirty, not clogged.

I am running out of ideas. Any advice on what to check next?

Thanks in advance.

06-07-2006, 07:45 AM
I would replace the fuel filter 1st. /ubbthreads/images/graemlins/laugh.gif

06-07-2006, 09:09 AM
Hey tr6ster...I've never been able to tell a lot from looking at a distributer cap or rotor. Points are the first things I check when there's a misfire, then replace the rotor, and if necessary the cap. I also try and fix or replace one thing at a time, so I know what cured the problem.(It also gets the engine good and hot, so it's a "joy" to work on).
I think electronic ignition will eventually solve a lot of ignition woes, but I'm "scared" to try'em.
Take care Bob

Andrew Mace
06-07-2006, 12:16 PM
AND, if you've not touched the carbs in that long, it's worth taking a look at the diaphragms. One pinhole or tear can easily cause the symptoms you describe.

But making sure that the ignition system is as it should be, changing the fuel filter, and possibly checking and resetting valve clearances are all good things to do FIRST. As many folks have noted, 95% of carburetor problems are electrical. /ubbthreads/images/graemlins/grin.gif

06-07-2006, 12:41 PM
I had something very similar happen on one of the first drives I took this year. Ended up having my car hauled home. The condenser failed. I had installed a new one and did not get 100 miles out of it. Replaced it and everything has been fine.

06-07-2006, 03:36 PM
Some great suggestions. I'm going to try a new distributor cap, rotor and condensor, as well as fuel filter. $25 at VB.

Is it a big deal to pop the top off the carbs and check the diaphrams? Do I need to replace washers?

06-08-2006, 09:51 AM
Hey tr6ster... be sure and get back to everybody with the resolution...adds to the pool of knowledge.
Take care Bob

06-08-2006, 10:05 AM
Bob its not hard at all to take off the top of the carbs. Just be careful with the screws. They may look like phillips head but in reality they are something called posidriv. You can use a phillips xcrewdriver as a last resort but just be careful.

06-08-2006, 01:35 PM
Bob its not hard at all to take off the top of the carbs. Just be careful with the screws. They may look like phillips head but in reality they are something called posidriv. You can use a phillips xcrewdriver as a last resort but just be careful.

[/ QUOTE ]

Dem Brits always have to be a bit different don't they?
This forum is great, but it has just cost me around $500 in new ideas such as looking at Miata seats, fixing a smelly fuel tank, refinishing my dash etc. Thanks!

06-13-2006, 08:18 PM
Well I replaced the condenser, rotor and distributor cap, and now the engine will turn but won't fire at all. At least before it would start, just wouldn't run past 2000 RPM. The ignition spark plug sequence seems to be right, I guess I'll put the old parts back on and see if it'll run.

The condeser was simple, a holding screw and a contact screw (with a rubber washer). The rotor went right on and the cap seems to fit well. ???????????????

Andrew Mace
06-13-2006, 08:33 PM
Did you possibly isolate the wire from the condensor where it and the low-tension leads attach to the points? Easily made mistake, and we've all done it (haven't we, folks? c'mon now, ADMIT IT). /ubbthreads/images/graemlins/hammer.gif

06-13-2006, 08:48 PM
The order from top to bottom:

Nut, Rubber washer, Condenser lead, Black wire lead (is this the low tension lead you refer to?

Andrew Mace
06-14-2006, 09:01 AM
Yes, and that sounds right.

06-14-2006, 09:31 AM
OK...darkest before dawn! Check for spark at the coil wire. Place the wire within 1/8th inch, and try and start the car (DO NOT HOLD ON TO THIS WIRE...and don't ask how I know). No spark- check coil. there is spark, remove a sparkplug wire and try the same thing. If there is spark at the coil, but not at the sparkplug, the problem is inside the distributor ie. rotor,points, or condensor.
If there is spark at the plug, the issue IS probably fuel related.
There is a Lucas Troublshooting guide available, for less than 20 bucks...integral part of my travelin' toolbox.
Take care Bob

06-14-2006, 10:04 AM
At 70k the motor might have jumped timing. Put the motor at TDC and see where the rotor is pointing. If its not pointing to #1 or #6 it might have jumped timing due to over stretched chain. Its not to common on motors with a chain tensioner, but its something to look at.

06-14-2006, 03:21 PM
At 70k the motor might have jumped timing. Put the motor at TDC and see where the rotor is pointing. If its not pointing to #1 or #6 it might have jumped timing due to over stretched chain. Its not to common on motors with a chain tensioner, but its something to look at.

[/ QUOTE ]

Here is a dumb question- how do you put the motor at TDC?
Another dumb one- is 1 at the front or rear of the engine?

Andrew Mace
06-14-2006, 05:43 PM
TDC for the #1 cylinder is when that piston (closest to the front of the car, btw) reaches the top of its stroke while the exhaust valve is closing and the intake valve is opening on the #6 cylinder.

06-14-2006, 08:46 PM
I would start with getting spark to the plugs first. Once you have that, we can move to the basic timing. Then we can spray starter fluid into the carbs. to see if it will start. With each step we eliminate potenial problems. Then we start getting into the uncommon problems, like the timing chain. Confirm all the steps you've taken so we can move you in the right direction. It's important that you have a manual for your car and that you're familiar with how things work. We're here to help.


06-14-2006, 09:31 PM
any luck with the "spark test"?
79 MGB

06-15-2006, 07:27 AM
I pulled the wire to the ignition coil and checked it with a voltmeter. When I put the key in Aux 5 volts showed up. When I tried to start the car it stayed around 5 volts (jumped around between 4 and 6). Shouldn't the voltage be higher? I then connected the ignition wire and pulled a spark plug wire and checked it on the voltmeter. No voltage when I tried to start the car.

06-15-2006, 08:10 AM
Don't use a volt meter on the spark plug wires. These wires cary very high voltage, 15,000 to 40,000 volts. If any voltage was out there you may not have a working volt meter any more.

06-15-2006, 08:56 AM
Your coil has three wires. One to ingnition, one to the distributor and one large one to the distributor cap (center). With the ignition on, put your voltmeter from a ground source to the ignition wire and give us your reading.

06-15-2006, 09:54 AM
I still think the condenser. You may have re wired it wrong or the condenser is bad. Pull the condenser and put an Ohm meter across it. If the meter (has a needle) the resistance should be low then go high. Reverse the leads and the resistance will go low to high again. If the resistance stays low then the condenser is shorted. If the resistance stays high then it is open. Think of it as the ohm meter filling a can with air, as the air first goes in there is low pressure as the can gets full the pressure goes high until the pressure equallizes to the applied pressure. A short is like a hole in the can so the pressure stays low, an open is like the can being full of water, the pressure is high to start. It is not uncommon to get a new bad condensor.

06-15-2006, 11:28 AM

A diagram for your tr6 is available for free download at:
Although a Haynes manual or some other comprehensive manual will (though they are not perfect!) be a helpful reference.
Either should help you nagivate your way around the coil.

Good luck, & keep us posted!
79 MGB

06-22-2006, 01:52 PM
Hey tr6ster... How did it turn out? I sorta felt like we must have led you astray. Was the problem carb based or electrical, or some of both?
Take care Bob

06-23-2006, 02:41 AM
Hello TR6ster,

"Another dumb one- is 1 at the front or rear of the engine?

In the case of most cars, yes but it is a convention. Jaguar Cars, for many years, used the opposite and number one was the rear cylinder.


09-05-2006, 07:53 AM
Well- after changing the points, condenser, dist cap, spark wires, ignition coil, spark plugs and battery it still won't start.

In fact, it is digressing. 1 week ago the starter would turn the engine, it just wouldn't fire.

Now I get nothing, no click, no engine turn.

Question to throw out there- where is the starter relay. I need to start there and work my way through powering the starter.

Any suggestions would be greatly appreciated.

09-05-2006, 10:47 AM
Did you get the wiring diagram yet? You will need it. Is the battery up to a full charge and will it take a load test and still hold voltage? You need to start with a known good source of power before you try to determine the problem with the "no turn over".

09-05-2006, 01:51 PM

I have been trying to follow the diagram. If someone could explain the sequence I would appreciate it- Ignition switch to starter relay to starter solenoid to ign coil, etc.

And where is that bloody starter relay?

I have a brand new battery, plenty of amps.

09-06-2006, 09:28 AM
There is no starter relay; the high current supplied to the starter is done with the solenoid, which is mounted, directly to the starter.

I suspect you have a more fundamental problem (and much less expensive) like bad connections, possibly at the ignition switch? I don't have any schematics at hand, so I cannot give you a step by step list to check; however, I would check the physical connections on the starter to be sure they are secure.

09-06-2006, 11:46 AM
There is no starter relay; the high current supplied to the starter is done with the solenoid, which is mounted, directly to the starter.

[/ QUOTE ]

This wiring diagram (scroll down to '74) (https://www.advanceautowire.com/tr2506.pdf) shows a starter relay seperate and distinct from the starter. It first shows up in '74. It also has a solenoid relay for the high current mounted on the starter.

I don't know where that other starter relay is located.

09-06-2006, 03:47 PM
Mines a 74.

So when the key is turned, a current path opens for high current to the starter solenoid, and then a secondary current goes through the starter relay to the ignition coil?

I have been reading 5 volts across the ignition coil terminals, it never gets to 12. I'm not sure that means anything.

09-06-2006, 04:44 PM
Just looking at the wiring diagram, it appears as if the current goes from the ignition switch to the starter relay, then down to the starter solenoid. The starter relay (at the "C4") connection also supplies the 12V to the ignition coil for starting. The best that I can see here is that the the "start" circuit from the ignition switch leaves on the WR (white/red) wire to some connector where it exits as a WO (white/orange) wire, and that runs up to the coil in the starter relay (NOT the ignition coil)as "W1" connector. The coil then grounds at "W2" and activates the starter relay. The contacts close and send current to terminals "C1" to the starter solenoid and "C4" to the ignition coil.

I've got a gut feeling that you are losing it in that connector where the WR and WO wires meet. Either way, you are going to have to find this starter relay to take some voltage readings and find out where you are losing it. After looking at this diagram for awhile, I'm pretty sure how everything works, so once you find this relay, diagnosis shouldn't be too difficult. I'm sure me or someone else can walk you through it.

09-06-2006, 06:39 PM
My'75 has the starter relay on the driver's side inner wing, to the rear of the fusebox and below the horn relay (assuming you have two relays there, the one with most wires is the starter relay).

Hope that helps

09-06-2006, 07:05 PM
You are correct, there is a starter relay. Guess I was thinking of the '76. Since my TR6 is a '74, it will be worth knowing where this device is located. /ubbthreads/images/graemlins/confused.gif

09-07-2006, 07:30 AM
Found it! It appears that a previous owner has done a bit of rewiring.

The wire from the starter relay to the ign coil appears to be cut, perhaps the relay went bad and is being bypassed and not used. The seat belt stuff (also connected to the relay) has never worked and this might explain it.

The smaller wire from the starter solenoid goes into the dashboard, as well as an insulated wire from the positive terminal of the ignition coil. I guess I need to track those wires down inside the dash.

The previous owner also repainted the car, whomever painted it dusted the engine compartment and covered most of the wires, so tracking wire colors has been very difficult.

Thanks for the help so far.

09-16-2006, 08:45 AM
Did you ever resolve the "dead starter" problem and figure out what the relay does?

09-17-2006, 08:13 PM
I still think the starter relay and seat belt module has been jumpered, and it has been wired like an older TR6. I still can't trace the starter solenoid "trigger" wire back into the dash. I imagine it's wired directly to the ignition switch. That's where I am going to look next.

There are a lot of new splices, and the person who repainted the car painted the engine compartment and sprayed the wires. So the color wires are all painted over, making it even more difficult.

I am getting no click at all when I turn the ignition. Can someone explain how the numbers on the wire diagram correspond to the 1,2,3, start positions on the switch?


05-23-2007, 09:49 AM
Going back to an old post...

I was coming off a freeway last year and when I tried to accelerate I couldn't get it to go over 10-15 MPH. The engine wouldn't get over 1800 RPM.

Turns out it was a couple of torn diaphrams in the Strombergs.

Also a previous owner had put the choke assembly back together backwards so it wasn't choking correctly.

Getting it fixed also led to a new master brake cylinder, clutch cylinder. Oh the horror.

05-23-2007, 01:10 PM
I'm with the others suspecting a loose connection or bad ign. component because you stated it was running great and you had not previously been experiencing engine problems. That's your biggest clue right there. I can see how you may suspect that the engine has jumped time but you need to get spark out of you distributor for the thing to run. Now i wonder if your starter not turning over is from the normal drain from working this problem out or a loose starter connection...these big wires need to be tight and secure. Have you checked the point gap? (if you are running point, that is). Be sure to review the posts you've recieved on this thread as I don't think you could get better advice.

Keep us posted!