1985 Nissan King Cab

[pafizz]

Ive been having a heck of a time.  Got this truck..already had new alternator, battery.  started just dying going along, pull over an wait a minute fires right back up.  took it to shop..they said coil was bad..replaced that..same problem..they replaced fuel pump and filter...same problem. then it decided it wouldnt run at all.  tired of giving them money.  read this forum and replaced relay.   fired right up.  fuel pump runs all the time now when key is on.  Could get 35mph an then starts coughing an sputtering, let off gas an smooths out.  Now wont start again.  Replaced spark plugs and wires, still only 35mph maybe.  now wont start again. will start if i put gas in carb.  fuel pump runs all the time when key is on.  Havent found anywhere that the gas is going.  What now???

[elmerfudpucker]

We need some pictures, and a full description of your setup. Could be upper fuel filter (if it has one), or needs a carb rebuild or replacement. Also I replace coils in pairs not just one. and take a peek at your fusible links and grounds.

[pafizz]

now this am fired right up, but runs a little rough.  havent tried to take it anywhere.  pictures of what?  

[elmerfudpucker]

For us, we want them all!!! You will learn we are picture whores here. this is how you do it:

http://community.ratsun.net/topic/691-how-to-post-pictures-and-keep-online-photo-albums/

 

but a few good shots of the motor so we see what you are dealing with, and everywhere else to show off the truck! 

[datzenmike]

A shot of the carb with air filter off when motor is hot from running.

[pafizz]

i cleaned the filter in the carb seems to do better but still cutting out at 40

[Tinman]

Have the 2 fuel filters in the back ever been changed?  If you have the original pump, it'll have one in the bottom, but the one that clogs is the big one between the fuel tank and the pump.

This will usually give that exact symptom, as well as overwork your pump.

[pafizz]

another

[pafizz]

when the shop replaced the pump and filter....i will have to go look...not sure though if they replaced that one.

[pafizz]

yes, that one was replaced also.

[Tinman]

Hmm..... I'd eliminate fuel by pulling the hose off the carb and extending it so you can reach a bucket.  Then turn on the ignition and see just how much is actually being pumped to the carb. 

It's entirely possible you have rust or crap in the tank that just fouls up another filter. 

 

But if you are getting a good stream of fuel at the carb, then I'd look there.  The 720 can get VERY temperamental when vacuum hoses leak or are disconnected.

 

Try this:  There should be a check connector behind the carb on the fire wall near the wiper motor.  It's a single wire, yellow with a stripe I think.  Dis-connect it and see how it runs.

If it runs fine, the trouble is in the electric feedback.  If it still runs like crap, possible blockage in the carb itself.  They do need a rebuild.

 

Looks like you have a California model 720, it looks exactly like mine under the hood.  These truck only run good and get good mileage IF that lambda feedback system is working correctly.  With the check connector pulled, there will be more pep, but mileage drops a lot.

[pafizz]

found that wire...started up...runs fine as before..no change...will take it for short drive prettty quick an see if any change.  It just may be the filter...i have a feeling this sat for awhile so may be stuff in tank.  ill get another filter tomarrow an replace that also.  Thank you

[pafizz]

Nope...still runs like crap at 30mph...will start looking at rebuild or replace carb

[Z-train]

Something in my memory says there was a problem in this truck with the fuel pump relay.A re-soldering cured my issues.

[pafizz]

i did replace that relay...at least it runs now....if only in the driveway.  Thank you guys for all your help!!  This thing is driving me back to smoking!!

[Tinman]

Looks like the carb needs a rebuild.  When I first got my 4WD I has problems like that.  Ran like crap.  In the end, rebuilding the carb finally cured it.  But always check everything around it first.

You probably have crud in the jets.

[datzenmike]

The feedback carb was also known for broken wires in the round connector behind the carb. There are 6 wires including the air fuel ratio solenoid and a throttle position switch, idle cut and choke heater. If there is a failure in the air ratio system the ECU reverts to a 'limp home' mode with an over rich condition and loss of power.

 

The wires in the the harness or on the carb side are too short and repeated movements or unplugging can cause them to break internally and are an intermittent bitch to trouble shoot.

 

 

As Tinman said probably dirt in the primary jet.