77 dies while running

[n2deep]

OK thanks. I'll time it in the morning and then replace the coil. Then report back.

[nractiv]

How odd - I just experienced this very same thing, last week. Mine cost me a trip on the flat bed. I had a nice person come by and jumped me while I was out on the highway. I left it running for a few min. with the booster cables attached between the vehicles and immediately headed back to home. On the way back it dies again. Fortunately I wasn't extremely far from homeso the tow didn't cost to much. After parking it for the week, I decided to do a little reading and basic troubleshooting and have decided to change the alternator and did a quick check on the battery as well as the battery terminals.

One of the terminals was very loose (cable connection only - not on the battery post.)

Before heading down this route I traded out the ignition coil for one that was a bit newer however off of a different z project. Still same - dying, so have decided to go for the alternator.

I replaced the alternator and battery but in the process also decided to make sure that the previous electrical work that I've performed is also correct.

Like the aftermarket radio and amp that I had installed a few months back.

Something to keep in mind, if you have added something new to an older vehicle, things such as a weak (older) alternator and or a battery that doesn't charge quickly have a hard time keeping up.

Good Luck!

[n2deep]

Update. Test 1. I started it up and put it in the driveway idling. It ran for 11 minutes and the temp got to 225 so I tapped the thermostat housing to unstick the thermostat and it died. It died the second I tapped it. Weird? Coincidence? What do you think?

[n2deep]

It was running hot because it was low on coolant. Somehow the heat at 225 shut the engine off. I added coolant and the temp stays normal and the car did not die for 15+ minutes idling. Go figure.

[IdahoKidd]

Hmmmmm, I am betting you still have the problem and it will resurface shortly.

[FastWoman]

Hmmmmm... Tapping the thermo housing killed the motor?

Maybe you've got a coolant temp sensor problem -- the one with the Bosch two-terminal connector that's part of the EFI system, not the one-terminal sender for the gauge. Maybe when it gets really hot, it goes open-circuit, and then your ECU dumps huge amounts of fuel, killing your engine. Just before the engine dies, does it gag and choke? Does it blow any black smoke?

You obviously need to replace that thermostat and fix a coolant leak somewhere too!

[n2deep]

Hmmmmm... Tapping the thermo housing killed the motor?

Maybe you've got a coolant temp sensor problem -- the one with the Bosch two-terminal connector that's part of the EFI system, not the one-terminal sender for the gauge. Maybe when it gets really hot, it goes open-circuit, and then your ECU dumps huge amounts of fuel, killing your engine. Just before the engine dies, does it gag and choke? Does it blow any black smoke?

You obviously need to replace that thermostat and fix a coolant leak somewhere too!

The engine simply quits suddenly without choking and no smoke. It has been a while since I drove the car on a regular basis and I honestly cant remember the last time I checked the coolant. When I opened it up yesterday it looked like just water, no anti freeze. Maybe it slowly evaporated overtime? Do you have any suggestions for test 2?

[IdahoKidd]

I'm confused. You opened the radiator cap and saw water? I am going to associate water with coolant for the moment and leave "anti-freeze" out of the equation. In general terms, they do the same thing, conduct heat away from the engine. There is no correlation between anti freeze or water not making the car run. Now if the "coolant" level was low enough to make the temp gauge rise, you wouldn't be seeing it in the radiator. If the radiator were so low that there wasn't water moving over the temp sensor, it would think the engine was cold and would enrichen the mix, resulting in the flood symptoms FastWoman describes. I can't recall if the engine dies on my 77 when I disconnect the temp sending unit to the computer or not. (buried in my 240 build and very different systems). As I recall however, there are two senders in that water neck area, one goes to the gauge, the other to the computer. Tapping the housing and the engine dieing makes me think a bad connection or faulty sender. Your problem is now just hiding, it hasn't gone away and you are looking to have an alternative ride home at some point. Check the factory service manual and locate and check the sensors and the wiring. Mine has a bullet type connector that was very corroded when I got the car.

[n2deep]

Sorry about the confusion. After it died when I tapped the thermo housing, I felt the radiator and it was cool. When I opened the cap there was some pressure and the moisture under the cap was clear. No color of coolant. That's all I'm saying. I could not see the coolant level. I added about a gallon of coolant. I will check the sensor connections and report back.

[FastWoman]

Well, despite the lack of choking and gagging, I'm still betting on either a bad coolant temp sensor (the one with two terminals) or the connection to that sensor. When that circuit opens, the ECU dumps enormous quantities of fuel. I bet it's related to thermal expansion; when your engine heats up to a certain point, connectivity is broken. The tap on the thermo housing is otherwise too much coincidence. A new sensor is maybe $15 from the nearest auto parts store, and you can clean out the connector with WD-40. Fold up some grocery bag paper into a little spade about the right size and thickness to slip into the contact. Soak it with WD-40, and push it in and out of each contact to clean the corrosion.

I don't know what you mean about test #2. You mean testing the 2-conductor sensor? I think I'd just replace it because of its being suspect.

[n2deep]

Well, despite the lack of choking and gagging, I'm still betting on either a bad coolant temp sensor (the one with two terminals) or the connection to that sensor. When that circuit opens, the ECU dumps enormous quantities of fuel. I bet it's related to thermal expansion; when your engine heats up to a certain point, connectivity is broken. The tap on the thermo housing is otherwise too much coincidence. A new sensor is maybe $15 from the nearest auto parts store, and you can clean out the connector with WD-40. Fold up some grocery bag paper into a little spade about the right size and thickness to slip into the contact. Soak it with WD-40, and push it in and out of each contact to clean the corrosion.

I don't know what you mean about test #2. You mean testing the 2-conductor sensor? I think I'd just replace it because of its being suspect.

Yes that makes perfect sense. Thanks for the cleaning tips. Test# 2 was referring to the "more controlled test" you mentioned to help the diagnosis in your earlier post. (running at a higher rpm)

[FastWoman]

Right now the ignition isn't nearly as good a theory as the coolant temp sensor. The fact that the engine died immediately when you tapped the thermo housing strongly suggests something in the vicinity of the thermo housing. Your ignition module is in the passenger firewall, and your coil is mounted on the driver fender. Neither of those would have felt your tap. So for now, I'd forget Test #2.