Need help... roadster only idles... something went wrong

[deisenba]

I'm new to the world of Datsun Roadsters. I have a 1969 2000 that recelntly died on me. I was driving down the freeway at about 65mph when I came to my exit. I took my foot off the gas and it backfired about 3 times. I came to a stop and all the car would do is idle. I checked the fuel filter, it was good, but I replaced it anyway. The fuel line is not plugged. I checked the compression. 123 psi on all 4 cylinders. I checked the diaphrams on the fuel pump, and they seemed ok. I'm not sure where to go from here. Anyone have ideas as to what I should check next. I've had the car about 3 years and have never had a problem with it.

thanks

[S Allen]

So what you are saying is your car backfires when you now give it some gas? Sounds like you checked the fuel delivery and all is well. Try doing a tune-up i.e. cap, rotor, points and plugs. They do wear out after a while. Also while you have the cap off of the distributor check to see if there is any play in the rotor mount. It should be solid and not move much. If you can wiggle it you either need to rebuild your distributor or buy a rebuilt. A dizzy can go bad while driving along. Could be a bad coil as well. A bad coil will get very hot. Good luck and welcome to the forum.

Steve.

[deisenba]

You are right that I should move to the cap, rotor, plugs, coil... The car does not back fire now. It only did it when the problem started. Now I have to hold the gas pedal to the floor to keep the car idling.

Thanks for the advice

[SLOroadster]

First, did you check to see if your throttle cable slipped? Did you check to see if both dashpots move freely in the carbs? Did you pull your valve cover and check for broken valve springs? The fact that your car only shows 123 in th compression check raises red flags right there. A new U20 should show 166, (bored .040 mine shows 188 on three and 185 on one, the low one is probably related to bad vave ajustment and I should fix it soon.) Do check your wiring carefully, hopefully it is something simple. Also check to see if pulling the choke on changes anything. Also your carb balace could be way off. Just take your time and eliminate potential problems one by one.
Good luck,
Will

[kt]

Sounds like you checked the fuel lines pretty well, but
did you check the filters located IN each carb?
If these get clogged(and they could easily, as each fuel
pipe there is only about 2mm) it could lower the fuel
pressure on your float valves, delivering minimal fuel
to the floats.
This mite explain why you have to have the pedal down
to the floor to idle.
You should also have problems starting if this is the case.

You should also make sure the butterflys in each carb is
indeed moving when the accel cable is pulled on.

[DatsunBucky]

Might want to check the float levels, too. Just because you're getting fuel TO the carbs doesn't mean there's fuel getting INTO the carbs.

For what it's worth...

Bucky

[bedwyrbannog]

Make sure to check the choke.....everything moving freely. Air/Fuel Mix could be too rich....

[DatsunBucky]

"Make sure to check the choke.....everything moving freely. Air/Fuel Mix could be too rich...."

True. Have someone check the exhaust while you're running, and if it's belching black smoke, you have a very good clue as to what's wrong.

Bucky

[deisenba]

i have not yet gotten a chance to check all the stuff that people have advised about. I will for sure this weekend. I had been thinking it is a carb problem, but now it seems several people agree. I think that is what I'll tackle next. I did check the movement of the choke and throttle cables. They were all moving good. The fact that the problem started the second I took my foot off the throttle, makes me think it is the carbs. Keep the suggestions coming though. The more I tear apart, the more I'll learn... or screw up.

[SLOroadster]

Thats how you learn, or at least that is how I learned. I have pulled almost everything apart on my car and put it back together. I have done all the mechanical stuff, having a good idea about how to do it, but never having done any of it before. The engine rebuild was a BIG step, but now I think I can do one pretty quick. Just go slow and take notes. Nissan was (for the most part) very carefull about making repairs quick, easy and straight-forward.
Will

[bedwyrbannog]

Let me get more in to detail...take off the air filter housing...and check that the jet moves freely...while the air filter is off check the float for free movement and check the oil level. From what you described... it sounds like something in the carbs has gotten stuck.

[SLOroadster]

Yes I think you have a carb issue. You also might have a distributor issue.
To check the main float jet you must pull the top off the float bowl. Make sure the floats do not have any fuel in them (check for cracks). From there check the dash pots for obstruction. When you lift them to the top make sure they move with a fluid smoothness, and return with an audible "clunk". Also check to make sure the needles are both in place and secure. The screens in the carbs (located with the bolts that hold the fuel inlets onto the carbs) could be plugged. Pull them, blow them off with compressed air and reasseble) When in doubt and frustrated, hose the carbs down with Carb cleaner both inside and out. If nothing else, you end up with cleaner carbs.
As for the electrical, check your points. They might be out of ajustment.

Will