Engine runs only when choked...

[kenz240z]

Don't give up yet, there's something else you might want to check. I had similar problems with my '73 when I first bought it. The car had been sitting for seven years. I replaced plugs, installed a new battery, a new fuel filter, changed the oil, put in new points, rotor & distributor cap, new belts, new hoses, etc... I even took it to a local Z mechanic to adjust the valves and balance the carbs.

Even so, my car was hard to start. I would have to tap the gas pedal while turning the key to get the engine to catch. Even then it would only run for a few moments. After repeating this several times the car would either start to run (poorly, though!), or the battery would be dead from the many attempts to start the car.

I was having similar problems with fuel delivery to the rear carb. I could cover the carb throat and it wouldn't have any effect on the way the engine ran (which was poorly!). I pulled the coil wire and pulled the fuel hose to the front carb and when I cranked the engine over it would pump gas. When I pulled the fuel hose to the rear carb and repeated the test it would pump fuel, but not as much. This was all very perplexing... I ended up replacing all the fuel lines in the engine bay to no avail.

When I was lucky enough to get the car running it wouldn't accelerate very quick, and the engine would die after driving for 5-10 minutes. I checked and re-checked everything, to no avail. I finally "discovered" that the electric fuel pump mounted back by the fuel tank has a filter in it. I removed it (got covered with a bit of gas, be careful!) and found it to be clogged up with a brownish powdery substance. Never figured out exactly what it was, but probably related to the car sitting for 7 years.

Any way, that helped a lot, but the car still didn't run like it should. Acceleration still wasn't that quick and the car wouldn't go faster than about 55 mph without losing power. On a whim I replaced the fuel filter on the right inner fender again and the car has run great ever since. I guess the filter I put in there originally must have gotten clogged up, too. So, in my case, even though I verified that fuel was getting to the carbs, the two fuel filters were clogged up enough to make the engine hard to start and prevent the car from accelerating or going very fast.

You might want to check out the fuel filter in the electric pump and also the one in the engine bay.

Hope this helps...

Kenny P.

[240Zdragon72]

I got some carb rebuild kits from Auto Zone and replaced everything the kit came with. Set the carb needles to 2 1/2 turns down from the top. Started the engine and what do you know.... it runs like a champ. I have also replaced the fuel filter and fuel regulator in the engine bay. (have the regulator set at 3psi) Ran the car almost for a full hour without a backfire or hesatation in power. I still have dark exhaust during acceleration. When I crank the engine to start, it feels like the battery may be on its last leg. Still having the problem with the headlights not coming on at times. Thank you everybody who has picked their brain to help me figure out what the problem was. Now the test....driving it to work. :eek:

[240Zdragon72]

I was driving to work lastnight when the car started to act funny...again. I was in 4th gear and my speed was around 40-45mph. The engine did not want to go any faster..like it hit an invisable limiter. It was making a loud buzzing sound around/ in the header area vibrating the whole car. When I backed off there was a really loud backfire, giving it more gas did nothing. As I creeped it home in 2nd gear, all it did was backfire (but not as loud as the first one) and had loss of power. A guy I work with said that my valves might need to be adjusted, another says something is wrong with the exhaust. I hope it is something simple. Woundering if you guys might have had some experience with this. Thanks again.

"She's my baby...she needs to be driven!"

[thehelix112]

I have only briefly scanned this thread so I apologise if this has already been asked, but are you using the flat top `SU's or the genuine round tops? If you are using the flat tops, don't. Bin them.

Dave

[240Zdragon72]

I have the round, 3 bolt tops. I just installed repair kits on both of them. I have no idea. My timing is set at +10 deg. TDC. I checked it again early this morning and it is still good. New plugs, fuel pump, filter, and regulator. I will have to try and set it higher (3.5 or 4psi) to see if it will make a difference. (crosses fingers)

[240Zdragon72]

As I read over kenz240's reply, I was also thinking that the prefilter (right before the pump) might have something to do with the problem. He was right. Remember back in the thread when I said that I turned the pump on and "coffie colored fuel started to come out."? I should have remembered that a long time ago. When I pulled off the filter a huge pile of SAND came out. ( a brownish powdery substance.) I installed a jumper line to fill the gap from the old filter. Kicked the pump back on and now the filter in the engine bay is covered with sand. FUEL STARVATION!

I have atleast 1/4 of fuel left in the tank. The car will run, but I will have to shift at low RPM to keep the carb bowl from running empty. Then I will have to drop the tank and clean it out really good. Run some compressed air through the lines also to get whatever is left out. I will post pic's as soon as I figure out how to make them appear in the thread.

Thank you so much to all of you for racking your brains to figure it out. Who would have thought it was SAND!?

[kenz240z]

Hi Brian,

There should be a drain plug on the bottom of the tank. Just be sure to have a suitable container underneath to catch the gas. You could probably strain the gas and pour it into the gascan you use for fueling up your lawnmower.

Once drained, the tank isn't too hard to get out. It seems like one of the screws that holds the gas filler neck retainer (the one accessable from under the car) is kind of hard to get to. When everything is disconnected, put a jack under it. Use a block of wood, like a 1 foot section of 2X4 to support the tank. Disconnect the straps and slowly lower the tank. There are a couple of vapor recovery hoses on the top that you'll have to reach up and disconnect before the tank can be removed.

I'm glad to hear you found the problem.

p.s. You can't post pictures when you use the Quick Reply. Select Go Advanced or Post Reply. There should be a button called Manage Attachments. Use that for adding a photo to your post.