Only Runs While Throttle Is Wide Open..

[dylan.andrus11]

I have a 1971 240z, when I bought it it ran well and was good all summer and come winter time I had some minor things to fix. Decided to pull the engine and rebuild it. Everything was cleaned and put back together, everything seemed fine but now it won't start. At first there were electrical issues, no power to the ignition. That was fixed and we tried to start the car. With the throttle fully open it will turn over really rough but it runs, barely.. it sits at 1000rpm and after a couple minutes it dies (that is worth the throttle fully open the whole time). We checked compression it's good, checked for leaks at all flanges and there are none, replaced spark plugs as 3 were shot, firing order is all correct, it's a twin carb set up and we checked both float pots on the carbs both are getting/have gas so It is getting fuel, if you release the pedal it dies instantly. I have no idea what could be wrong.. has anyone had the same issue? Or any ideas on how to fix it?

[Zed Head]

You say "throttle wide open" but later it looks like you mean "throttle pedal pushed to the floor".  What's really happening at the carburetors?  And what type are they?  That might be the key.

 

Also, what do you mean by "shot" with reference to the three plugs?  And "turn over" is what the starter does.  "Fire" would be descriptive of the engine trying to start.  And, although it probably doesn't matter, one person's "good" is another's "maybe bad".  If you got numbers, you might as well throw them out there.  If you're checking compression with your thumb though, that's a problem.  Numbers are always good to look at.

 

Full disclosure -  I haven't had a carbureted car since 1995.

[dylan.andrus11]

By shot I mean they are fouled. Yes sorry for the confusion, it fires. Yes you are right, I could have missed a few things. You're right it is probably the carbs, I personally don't like carbureted engines and I will swap the engine as soon as I can to one I know more about as I have two rb26's. They are twin SU carbs. The throttle body/ butterfly valve is opening fully but is seems like the "needle/plunger" (sorry if terminology is wrong) doesn't move at all. Compression was 130 on all cylinders. I got a friend to manually open the needle/plunger and it shut off

[Zed Head]

 I personally don't like carbureted engines and I will swap the engine as soon as I can to one I know more about as I have two rb26's. They are twin SU carbs. The throttle body/ butterfly valve is opening fully but is seems like the "needle/plunger" (sorry if terminology is wrong) doesn't move at all.

Don't wizz off the carb guys!  They have the answers!

 

These carbs are not like many, in that they have pistons inside, with damping oil to control their movement, and require exquisite tuning to work correctly.  `Seriously, they are different from a USA-type Rochester (for example) carb.  If you don;t have the right oil inside you might have problems.  Post a new thread with "Problems with SU's " in the title and you'll get some pros to take a look.  If you've covered all of the basics, carb problems are likely.

[dylan.andrus11]

Nothing against carbureted engines I am just not as good with them as I never deal with them.. just need to work with them a little more. Thanks for the help though!

[beermanpete]

Two things come to mind: First, it could be too rich. Are the plugs wet with fuel? Do you smell a lot if fuel while trying to get it running? Second, check the ingnition timing. It could be very late. If you still have points you can dead time it. Double check the timing mark on the damper as well to be sure it is actually correct. They can slip and drive you crazy.

[240260280z]

Ditto for Beermanpete!

[gnosez]

Not to be too much of a jerk, but when I looked at the title of the thread my first thought was - and that's a bad thing?

 

Carbs need to be tuned, linkages checked and timing set. Then get a new set of plugs.

[rossiz]

while you're checking linkage and basic carb functionality be sure the choke is working properly...