my friend has a 86 GXL...and it's having 2 sperate problems right now.


1:car starts, but seems to kill spark or fuel right afterwards.


so, i know that the car has 2 maps basically...a starting system, and a running system. the car starts, and will run for maybe 2-3 seconds, backfire if you try to give it gas, and then die. there simply is no way to keep it running.

....fuel pump is going, afm flapper is not stuck- so maybe the afm is shot?







2: the car has problems with blowing the engine fuse, and the car will suddenly have no fuel or spark?? fuel pump has been rewired to direct power until the source of the short causing the engine fuse to blow, is found.

thanks for any help i get!

 

Ouch. Find that short before it develops into an engine fire

It sounds like you car is running excessively rich. This suggests the ECU is being 'fooled', possibly by a bad sensor, failed wire to a sensor, or?

I had a very similar problem in my 86 last year; it turned out to be a broken wire to the oxygen sensor.

1. Are there any codes?
2. connect an LED in series with a 510 ohm resistor to the top and bottom center pins in your test connector. It should flash 8x in 10 sec during steady rpm operations (above idle). If it is flashing, the ECU is going back and forth between rich and lean, as it should. If not, it is not controlling the mixture. Look for bad O2 sensor or bad wiring to the sensor.
3. If that doesn't work, pull up the passenger side carpet and floor, get to the ECU connector (52 pins over 3 connectors). Back probe each pin in the ignition on but not running state, and compare with the voltages in the FSM. If all ok, start the car, do it again in the running/idle state. If you have a sensor problem, it should show up as a voltage not per the specs in the FSM.

In my case, the car acted very similar to how you describe this one, but only when the ECU failed to note the not-present O2 sensor, and tried to adjust mixture using the dead wire. It saw 0v, and interpreted that as a lean condition, and ran the mixture full rich to 'correct' the (non-existent) lean condition. The problem developed over some time, and I surmise the driveability was due to plug fouling. In those cases where it correctly judged the 02 sensor missing, it ran fine. Very puzzling, until I realized it was throwing a code 5 when it ran well, and no code when it did not. What really allowed me to understand it was the closed loop test; there were no flashes of the LED at constant rpm.

May not be the same problem, but certainly worth a check.

By the way, the short in the engine system may turn out to be related to--or even the reason for--the ECU not adjusting the mixture correctly...

 

thanks for the help..now i have a few things to look over- and even more possibilities as to whats actually wrong..

really have to find why it blew that engine fuse..may just be age? this car has a bunch of bogus wireing..its hard to tell what is what.

 

afm

 

Age will not cause the car to blow fuses. Short or grounded circuits cause fuses to blow. You will have to systematically isolate the circuit that is causing the short.

The wiring diagram in the online FSM (see the links in the FAQ section) will be essential. I am not sure which fuse you are calling the 'engine' fuse.

With the power off and the fuse removed, check the resistance from the fuse connector to ground. It should be high (on the order of a hundred of ohms or higher). If it is not, try disconnecting things tied to that circuit, one at a time, and checking the resistance to ground each time. If the short is in an electrical device connected to that harness, you will see the resistance go high when the offending device is disconnected. If you get to the point where everything is disconnected, and the resistance is still low, then the problem is in the harness, i.e. a short (one wire touching another) or ground (one wire touching ground). Look for places where the wiring appears to have been tampered with, wrapped with electrical tape, melted insulation, etc. You can also hook up the ohmmeter and then go around and jostle the wiring harness in multiple places, and see if there is one where the movement causes the resistance to go intermittent.