77 dies while running

[n2deep]

Hi Guys,

Cold and snow pulled me off for a while but I'm back trying to fix this problem. I stopped by my local shop to describe the problem. They said the sensors could not kill the engine as I described. They said the coil could. Well, a new coil did not fix it. The sensor connections look good. Any other thoughts?

[sblake01]

Have you checked the fusible links? Fuel pump/EFI main Relay?

[FastWoman]

Really? They said a bad coolant temp sensor (or connector) couldn't kill the engine? Well, that might be true with a modern EFI that would go into "limp" mode, however there is no limp mode on an L-Jetronic EFI.

A useful experiment: Unplug your temp sensor and try starting your car. It might run, and it might not. If it does run, it will be barely, and it will be billowing great clouds of back smoke.

I'm still fixated on the single tap to the thermo housing instantly killing your engine. I doubt that was just dumb luck.

Edited April 3, 2011 by FastWoman

[Willoughby Z]

Hi Guys,

The sensor connections look good. Any other thoughts?

Just 2 cents:

My opinion regarding anything that 'looks good'...

If you have a problem, then something is NOT good.

Clean and protect (anti-corrosion) all electrical connections.

Grounds.

Terminals.

Connectors.

Period.

Off topic slightly, trying to illustrate my point:

If a spec calls for a torque setting on hardware, do it (experience might support some exceptions).

My point is, I have a friend who lost a wheel right off the hub. He was puzzled because the lug nuts 'looked OK' after performing a brake pad replacement.

[IdahoKidd]

Hmmmmmmmm,,,,, thought we'd hear from you again.....

Have you checked fuel pressure as Zed Head suggested?

Does every thing else electrical work the moment it shuts off? Radio, lights, anything else drop off too? (looking for a electrical feed or ground issue here).

Did you ever replace the fuel filter?

Does you local shop know anything about Z's or are they generalizing. New systems work very differently than the old ones.

When it dies, is it like the coil wire is pulled or does it wind down and fade away?

Next time it dies in the driveway, pull the wire from the starter (I think it is yellow) that has the single spade on it. This is the starter excite wire. With that wire unhooked, the motor will not turn over but you should be able to hear the fuel pump working with the key in the start position (fuel pump works in the crank cycle).

I'm still thinking fuel

Leonard

[turbo 260]

First thing we need to find out, is it fuel or spark. Next time it dies, take an extra spark plug and connect it to one of the plug wires. ground it out on the strut tower and try to start the car. Does it spark? If not, the problem is on the spark side. If it does, then we can rule that out and move to fuel. we really need to know the fuel pressure. Buy an underhood gauge. make sure it's mounted between the underhood filter and the fuel rail (not the return line). If the pressure is good, then you'll need a noid light. This plugs into one of the injector leads, and flashes when a pulse is sent from the ECU. No pluse can mean a few things ECU related. I would also check the voltage at the battery while the car is running. It should be between 13-14.8 volts. Less then 9 and the car may not run. One of these tests should lead us to the problem, or least in the right direction.

Jim

[sblake01]

Next time it dies, take an extra spark plug and connect it to one of the plug wires. ground it out on the strut tower and try to start the car.

I would caution against doing that. It could send a spike through the system possibly damaging your ignition module. I suggest you use an inline spark checker instead.

[n2deep]

Thanks for all of the responses. I have not checked the fusible links. I do believe the problem is electrical. My truck did a very similar thing and it turned out the the relay distribution block was lose. I have an inline spark tester and will tset for fire next time it dies. The last 2 times it died, it did start again after only a minute so my down time for testing is brief. Is there an easy way to meter the output of the fuel pump/efi relays?

[sblake01]

In the 1977 factory service manual, there is a description of the functionality test of the electronic fuel inection relay which is one relay housing that consists of both the main relay and the fuel pump relay. Pages EF-55 through EF-57 outline the test.

[IdahoKidd]

Does this thing die every time it is started or does it sometimes go for a while first? Is it still running for five minutes then dying and is this also consistant? From your narrative, it sounds (to me) like it sometimes runs for a while and dies unexpectedly.

Not to be rude, but this ain't your truck. With 2/3 the folks helping you here saying to check vairious fuel delivery issues, that's probably what I would do, just to rule out that issue. A fuel filter is much cheaper than a coil for example.

[n2deep]

In the 1977 factory service manual, there is a description of the functionality test of the electronic fuel inection relay which is one relay housing that consists of both the main relay and the fuel pump relay. Pages EF-55 through EF-57 outline the test.

I have the Clymer shop manual and I have not located that test in this edition yet. I can see the diagram where the fuel relay is located.

IdahoKidd- Don't worry about being rude. I'm a grown up and I know I'm on here trying to get some help. I'm just trying to give you guys any info that can help. It very well may fuel related. I'm just thinking electrical as cause of failure vs mechanical or blockage.

Yes it does run for a while and dies unexpectedly. It dies after 4-5 minutes of driving or about 10 minutes of idle in the driveway.

[sblake01]

Here's a link to a pdf copy of the 77 FSM: