gronkX

Coming up on the end of the 2nd year of having a car that simply dies at random.

Though I had it figured out when my mechanic discovered a bad connector to one of the fuel injectors. He said that when the wires were shorted out, the car died; when they were separated again it would then start normally.

He replaced the bad connector, and the car worked fine for a couple of weeks. Until this weekend, when the old behaviour came back: driving home, and it simply stopped. Started cranked, all electronics worked, but the engine would not run.

So my questions for today:

1) Would shorting across the two wires going to a fuel injector kill the car?

2) If not, is there anything that might explain what he was seeing?

The car is an '86.5 5-speed, 135k miles. What I've done so far:

- tune up: new distributors, plugs and wires
- checked & cleaned all the grounding points
- replaced the crank position sensor
- replaced all of the '53 relays. And when the car won't start, jumping the fuel pump relay doesn't help

There doesn't appear to be a spark when the car won't run.

Any other suggestions, wild guesses, etc welcome.

worf928

No spark means:
Bad crank sensor
Both spark amps bad.
Wiring harness issues.
And a few other things too.
Since you've replaced the crank sensor, my bet would be a break in the harness to the crank sensor.
Shorted injector will kill the car, but you will still have spark.

joejoe

Absolutly. I just found a loose ground on my '86.5 and was problem. The offending ground (driver side injector harness) needed about 1/2 turn to be tight.

worf928

Yup. The two ground points at the back of the block also ground the computers. Having one loose is a Gremlin generator.

Mrmerlin

I would suggest you install a new engine harness.
Yes its expensive, but your car will never have any more running issues from bad wires or connectors.

Posting some pictures of the 14 pin connector and the MAF connector would help

76FJ55

I fought with an intermittent stalling issue on my 85 for quite a while. The others have all given good advice, and I would suggest you test those avenues as well. My problem turned out to be my EZF computer, which is apparently rather a rare issue, whereas the EZK on the 87 and newer cars is a little more prone to failure. In my EZF the 25 pin plug had several weak solder joints where it was attached to the PC board. One or more of these solder joints failed and would sporadically loose connection with the board and cause the car to stall. When you have the car running try grabbing the EZF connector and shaking it. If you have a bad solder like I did, this will most likely cause the car to stall. Not the most probably scenario, but a quick easy test.

Mrmerlin

as an add on to my suggestion ,
my 86 had harness failure and the PO had repaired it many times with many different repair procedures and most of them only created more issues.

Fitting a good used harness had the car running 5 hours after the swap began.

NOTE connector condition is a good indication of harness condition thus the request for pictures of the 14 pin and MAF connectors and wires.
Shorting injector connectors is also a good guide to the failing harness

worf928

It's the LH 2.3 computers ('87+) that fail with certainty. LH 2.2, EZF, and EZK failures are rare.

I agree with Stan, but add obvious caution: if the harness is not the problem, a new or used harness won't cure the problem. Loose grounds are not a harness problem. A harness with N patches/splices etc., is very likely a problem.

gronkX

I took apart the top end, and did fix one of the connections which looked loose - that's probably not the problem. (Before picture attached).

gronkX

Does the crank position sensor go through the 14 pin connector? That shouldn't be too difficult to check.

mark kibort

I remember one time at sears point, I was using the tap on the injector wire with my old 84 5 liter. it shorted or grounded or something and turned on the injector full bore!!! I was a flame thrower down the beginning of the main straight before they waved me to the infield with the fire truck 5 foot flames coming out the back! never do that rig job again! (for the little 02 sensor meter that had injector duration on it as well)

worf928

No.

The CPS circuit is part of the LH/EZF engine harness. That's the same harness that carries the grounds you pictured above. That branch is also shielded so it is not totally trivial to repair correctly. Also, unless damage is obvious you will not be able to see it by eye.

Get a piece of safety wire (or coat hanger) and use it as a remote to vibrate, manipulate or otherwise gently disturb, serially, the lead on the sender-side of the connector and then harness-side of the connector. With the car running, if you give your coat hanger a wiggle and the engine dies you've found a harness short.

Seems like your first step will be to locate the harness connector for the CPS...