TR4/4A Weird starting issue with my TR-4

[tr4boy]

Folks,

My TR-4 has developed a weird starting problem. When I turn the key to start, then engine cranks but won't fire. However as soon as I let up on the key and it's returning from the start position, the engine fires right up. I happens just about every time but is especially bad when the engine is hot. In fact, when hot, it's harder to start and when it does it runs pretty rough for about 30 seconds. Also, when hot i notice that the fuel filter is not filled up like it is when the car is colder. Not sure if that's related to the issue or separate issue. I thought maybe the coil was breaking down so I swapped in a new one but no significant change. It seems to crank okay, so I don't think it's starter related. Maybe the ignition switch is wearing out?

thanks for any help!

Greg

 

[TR3driver]

Do you have a Pertronix ignition by any chance?

Could be the ignition switch; I'd check by putting a meter or test light on the hot terminal to the coil and watching what it does while cranking.

 

[TomMull]

When the ignition switch breaks the starter circuit, it makes more current available to the ignition, and it starts. Of course, the switch might still be the culprit but I'd also check the battery terminals, ground strap and other ignition wiring.
Tom

 

[Geo Hahn]

I agree with Tom - this often means that the starter circuit is drawing too much current but when you release the key that draw is gone and your last compression stroke fires up the engine.

Could be in the wiring as he suggests or could be the starter itself. You might measure how much voltage drop you see when the starter is cranking - I'm thinking you should still see 10+ volts as it cranks.

 

[tomshobby]

Replace the starter solenoid.

 

[tr4boy]

Do you have a Pertronix ignition by any chance?

Could be the ignition switch; I'd check by putting a meter or test light on the hot terminal to the coil and watching what it does while cranking.

thanks for responding!, yes I have the the pertronix distributor and the pertronix coil that I just swapped in. Was having the same issue prior to the installing the pair though....

 

[tr4boy]

When the ignition switch breaks the starter circuit, it makes more current available to the ignition, and it starts. Of course, the switch might still be the culprit but I'd also check the battery terminals, ground strap and other ignition wiring.
Tom

Thanks, Tom. I just cleaned the terminals and the ground strap is about 6 months old and tight. I will look at the rest of the wiring though as you suggest since its the original harness...

 

[tr4boy]

Replace the starter solenoid.

Thanks, Tomshobby...I was thinking the same thing since it's pretty ancient. Have one coming next week.

 

[tr4boy]

I agree with Tom - this often means that the starter circuit is drawing too much current but when you release the key that draw is gone and your last compression stroke fires up the engine.

Could be in the wiring as he suggests or could be the starter itself. You might measure how much voltage drop you see when the starter is cranking - I'm thinking you should still see 10+ volts as it cranks.

Thanks, Geo Hahn. Where should I measure for voltage drop?

 

[tomshobby]

Thanks, Tomshobby...I was thinking the same thing since it's pretty ancient. Have one coming next week.

I should have explained; it sounds like the plunger isn't making good contact to activate the starting circuit. Then when the key is released it activates the circuit to the coil.

 

[Sarastro]

You can resolve this in five minutes with a voltmeter. Attach it to the coil, supply voltage side. Crank the starter and observe the voltage. If it's low, that means that the battery is weak or there is a bad connection, which causes the system voltage to droop when cranking. Work your way back to the battery (while cranking, of course) and see where you are losing voltage. If you find a change of a volt or more on either side of a connection, that's your bad connection. If it's still low when you get to the battery post, you probably need a new battery.

If it's zero at the coil, it means that either the ignition switch is bad, or maybe there is a bad or loose connection at the ignition switch. Or, maybe something wrong in the wiring between the switch and coil. Some cars have a ballast resistor and some circuitry to bypass it for starting. If your car has that, that's a place to look too. (Sorry, it's been a while since I dealt with TRs, and I just don't remember the setup.)

I suggest doing this before buying any new parts. The worst way to fix electrical problems is random parts replacement.

 

[Geo Hahn]

You can resolve this in five minutes with a voltmeter. Attach it to the coil, supply voltage side. Crank the starter and observe the voltage. If it's low, that means that the battery is weak or there is a bad connection, which causes the system voltage to droop when cranking...

I'm thinking some voltage drop during cranking is normal - say down to about 10.5 volts? A drop into single digits would suggest a bad battery or poor connection.

 

[Sarastro]

Yes, a certain amount of voltage droop is normal. Your suggestion of around 10V sounds reasonable to me. What you don't want is 10V at the battery and downstream from it you have, say, 8V--that means there is some resistance in a contact or joint somewhere. Now, if the voltage to the coil comes off at that 8V point, you have an ignition problem. All this is easy to measure with a voltmeter, and then you know exactly what is happening.

 

[thechileman]

Mine does this as well, (doesn't fire till I release the key.) It started happening for me after I rebuilt my dash. I assumed that in my case I got a wire plugged into the wrong spot on the back of the ignition switch. Since It always starts, I hadn't really bothered to figure it out. I have a new battery, starter solenoid, etc.. Anywho, I thought I would throw that out there.

 

[TR3driver]

Another way to check for voltage drop in the wiring is to connect one meter lead to the battery hot post, and the other to the post on the starter. When you hit the solenoid, the voltage should drop to less than 1 volt. You can do the same thing between the battery ground post and the starter housing.

But with points, you should get enough spark to start the engine all the way down to 6 or 7 volts at the coil. With a Pertronix, it takes about 8 volts. I asked about that because I had the same symptoms on my TR3 when the battery was going bad. The starter would crank, but the Pertronix wouldn't fire. Putting points back in let it start normally, until the battery got worse and wouldn't crank at all.

The test I suggested (voltage to coil while cranking) would also point up the problem that thechileman has.

 

[tomshobby]

My 1st TR and still my favorite car I have ever owned. Traded it for a new GT6 the following spring.