85 Nissan ECU

[Kennyt]

I have this truck. When it heats up it will stall and not start until it cools off. Then runs fine again until it decides to stop. Was thinking maybe an ECU issue? ECU controls carb so what would i need to do to ECU if u swap to a weber?

 

All ideans and info greatly appreciated

[Dolomite]

Issues like that are often, in my experience, ignition based. Igniters and ignition modules love to pull shit like that. Like gato says, if it seems like a fuel issue think ignition.

[datzenmike]

If you have an O₂ sender and one wing nut holding the carb on then yes you can just remove it and put a weber on. Make sure first that the weber adapter will fit the intake holes. This is important.

 

If you have two wing nuts then forget it as you have a  throttle body EFI (and not a carb)and there is no distributor but a CAS. 

[Kennyt]

Thanks. What does the ECU control on the carb? Also what else does it control other than the carb?

[Lockleaf]

It controls nothing but the carb. I've been running a Weber on my 85 for years and the ecu isn't even in there.

[datzenmike]

The primary jet is adjustable by an electrical solenoid. The ECU computes how long to open and close the jet with feedback from the O₂ sensor to keep it near perfect stoichiometric. This only applies to a warmed up engine not at full throttle and not idling. It's a sort of cross over between a carb and EFI. (sort of) 

[Kennyt]

Thanks all. So the ECU has nothing to do with ignition? The truck stalls from time to time and when it does There is no fire from the coils. Any suggestions?

[Lockleaf]

If wiring is stock, the two coils are fed power from different circuits. The exhaust coil gets power from a fuse. The intake coil is powered from the ignition switch.

 

It would be odd for both to lose power and no other circuit lose power. Does anything else fail when the truck stalls?

 

Shot in the dark, how are your fusible links at the battery post?

[datzenmike]

Info that would have pointed to the module being the problem. Much easier to get another and replace, than to put a weber on. Easier to just put a wrecker distributor in. 

 

Look at it this way... if it is the module in the distributor, putting a weber on won't fix the problem, right?

[Kennyt]

Yes it is. Can the module be replaced separately? Ill try to find a replacement distributor in the meantime

[datzenmike]

Yes it's under the rotor.

 

Understand, this is advice given in respect to you saying the spark was missing when it quit and refused to start. It would seem to indicate that the module is at fault.

[Kennyt]

I answered my own question. If there is no fire from the coil this would not be the module in the distributor correct? Either the coil is defective or something else. As lockleaf said one coil is powered from switch and another from fuse. Ill have to trace it out when it fails again.

 

Nothing else fails that i know of. The fuel gauge and temp gauge have never worked since i had the truck. I have a 83 and a 85. 85 has been "tinkered" with previously. It has run fine til recently. I have replaced the cluster with a known good cluster with no changes. Heat index been about 110° the past few days. Not sure if that is a cause or not. Thanks for all the input

[Lockleaf]

Fuel gauge and temp gauge both get power from the same source. How they ground is what makes them move. If you get under the hood and manually ground the temp sender wire (with the key in the ON position), the temp gauge should max out.

 

If the gauge maxes out, you likely need a new sender, but you know power is getting to the gauges.

 

If the gauge doesn't move, you have a power supply issue.

[datzenmike]

Swap your '83 dizzy in to confirm.

 

You have two coils so impossible that both coils heat up and faill at the same time. If one quit it would still run. Both is likely the module in the dizzy.

 

Gauges...

Forth fuse over from the left hand side powers the gauges but it also powers the turn signals and the reverse lamps. You would have noticed them not working. If another gauge cluster was substituted and the same then have to assume bothe the gas and temp sender are bad. Ground the temp sender wide (Yellow/Black stripe), located just under the thermostat housing on the intake. Temp meter should slowly climb to HOT. If it does the sender is bad.If nothing them suspect some wiring issue in the dash or gauge cluster.

[Kennyt]

Thanks again. No fire at dizzy end of coil wire when stalls. After cool down truck starts and runs fine

 

Will do on temp gauge.

 

When Lights are on fuel gauge registers full. When lights off goes to Empty

 

I sure appreciate all the info. U folks are great

[datzenmike]

Make sure the dash gauge cluster is well grounded.

[Kennyt]

Got the temp gauge working. Thanks. Got power to fuel gauge. Imma pull the tank and check that. I think there is an issue with sending unit in tank. Thanks again

[datzenmike]

Fuel gauge.

 

Not working....

 

Tank empty

Wire to sender off or broken.

Black ground wire off or broken on tank.

 

1/ With key on, ground the Yellow/White wire at the tank. If gauge works the problem in the sender or the ground. Go to 2/

If gauge still does not work there is a problem with the gauge or the wire to the tank.

 

2/ With key on, ground the Black wire. If gauge now works the ground wire is bad. Make a new ground for the Black wire. If gauge still does not work the tank sender has a problem.

 

As the wire connections for the tank sender are on top of the tank, and the top of the tank is a collection point for dirt and wetness the wire may be corroded.