[Guest]

Hi folks,

Thank you all for your responses. The ongoing saga of my newly acquired 77 continues. Since the last time I posted, I have replaced all the vacuum lines, all the sensors in the thermostat housing, cleaned all the F.I. connectors including the one that connects to the ECU sealing them with the infamous dielectric grease. It has a new distributor, rotor, cap, wires and plugs. All the injectors are new as is the F.I. harness. Keep in mind this car sat for two years but it is a fresh rebuild. The above mentioned items are recent except for the injectors and F.I. harness.

It still does the same thing. When I cold start it it runs fine. It starts with just the turn of the key. I let it idle (warm up) for about 5 minutes and it is like someone shut the key off. If I then try to start it, it will not start and if I keep cranking it then all you smell is gas coming out the exhaust and it is clearly flooded. If I walk away from it and let it cool down it fires right up and does the same thing. Sometimes if I start driving it right away it does not stall, it gets to operating temperature and runs like a bat out of ****. Once it is warm you can shut it off and immediately restart it with no problems.

Thanks again and I look forward to your responses. John.

 

[Zedric]

Sounds like its your fuel pump overflowing the engine. just a guess could be wrong, pull the pump and check it.

 

[greydog]

The symptoms you describe are typical of a failing electronic ignition. I'm not familiar with '77's so perhaps others can be more specific. Is there a "black box" attached to the distributor?
Another possiblity is the ballast resistor or coil. A certain sign of ignition failure is that, when the engines dies, the tack will instantly drop to zero, it will not "bounce" or move at all when the engine is turned over until, as if by magic the car will start and run as though nothing had happened.
Dan

 

[ZXKoyote]

I just slew a similar problem, by replacing the Distrib. cap, and rotor. Starts like a charm every time.

 

[ConorP]

Here's a crazy idea that I've never tried but should help track this problem down. I just tried it and it should work for your 77.

With the engine cold pull both connectors off the EFI relay. (Is it just above the hood pull as in a '76?) Now get in and turn the key (it may start and stall because of left over fuel pressure but that's not the point), check the tachometer, it should clearly bounce while "START"ing. Now pull a plug wire and check how "hot" the spark is while cranking. This gives you a baseline to compare to.

Now plug the relay back in and run the car until it's failing. Again unplug it and do the previous tests again. If you have no tach bounce and no spark then that's a complete failure of Transistor Ignition Unit ("black box"). If you have tach bounce but not spark then look elsewhere like the coil or ballast resistor.

Other tools like a timing light or dwell meter would be a helpful addition to this test.

ConorP

Another option would be to remove the 10gauge wire off the battery positive, this is the main power feed for the EFI ECU and Injectors.

 

[aren77z]

Few things to try:

1. Pull the connector from the cold start valve and start it up and see if it still does it.

2. Check and if necessary clean the bullet connectors on the FI harness these connections go to the thermotime sensor/coolant temp sensor.

3. Check fuel pressure.

I had the same problem, and it was the coolant temp sensor. just make sure ALL corrosion is off the connectors. It might even be worthwhile to splice in new connectors. (Search archives for p/n, Pepboys and bosch both have the kits.)

 

[joeytekno]

please solder them though.. no crimpstyle junk.. i think its the ignition module. under the glove by the pass. feet.. or the fuel filter.. and i donthink youre supposed to use dielectric grease on anything but sparkplug boots and ignition connections like inside the cap on the points or on the module wires

 

[dark-horse70]

The fact that it cuts out and in so suddenly really points to a thermal-related electrical problem. Something is breaking contact when hot and re-making contact as it cools. For this to occur, it must be something that either is heated by the engine or self-heats due to electric current flow through it. This is a typical symptom of a bad ignition coil, so I'd replace it first. If that doesn't do it, you can buy a non-conductive aerosol made just for the purpose of cooling electric components to troubleshoot this type of problem. It's typically called 'circuit-freeze' or something similar and can be found at most electronic part stores (probably available at Radio Shack). Just run the engine till it fails, and then try spraying one suspected component at a time and see if it fixes the problem. If spraying a particular part consistently makes it work, you've isolated the problem. Good luck.

 

[Duff5000]

that doesnt explain why the car can be driven if you dont let it warm up first. Wouldnt it die when driving if this is the problem?

"Sometimes if I start driving it right away it does not stall, it gets to operating temperature and runs like a bat out of ****. Once it is warm you can shut it off and immediately restart it with no problems. "