Engine won't stay running!

[RB_eater]

Hi guys I'm new here. I recently bought my first Z, a clean 1971 240Z, but I'm having some trouble with her.

I have an electrical leak somewhere and untill I could get some time to find it I installed a battery guard. Now when I started the car I heard a spark of some sort but the engine started normally. A few blocks away when I pressed the clutch the engine started redlinning so I shut it off as fast as I could. While it was still hot the engine would start but I had to keep it at full throttle. Now that the engine is cold it won't start at all, almost does but it keeps stalling.

I didn't have time to do a compression check yet but it doesn't seem blown, the engine was still smooth but it kind of looked like it wasn't getting enough fuel.

I tried looking at the carburator but everything looked fine (although I can't say I'm particularly at ease with carburators). The filter was clean and there seamed to be enough fuel comming out. I also checked the choke.

Is it possible it could be an electrical issue? The engine had barely 66000 miles on it some I'm hoping everything is still fine. If anyone could help it would be greatly appreciated. Thanks.

[RB_eater]

So I just did a quick compression check. All cylinders showed a reading of around 90-105 psi except one at 60 or so psi. I guess this isn't looking too good?

I noticed all sparkplugs smelled gasoline and were pretty dirty, all the tips were black. I didn't have time to clean them up but could it be they are the problem?

I also checked the oil, it's missing some and the engine is well overdue for an oil change. I suppose I should have checked that when I bought the car last week...

So does anyone have an idea what the problem could be?

Edit: I just checked a spark plug and there IS a spark so I guess the coil is fine, could still be one of the other 5 plugs though.

Edited October 24, 2009 by RB_eater

[Z Tyler Z]

I'm not an expert on Zs yet but here's some advice I've learned reading this forum.

I think each cylinder should be reading in the 160 range.

If I were you I'd do a round of basic maintenance before you start trying to trouble shoot the larger problems. Go and change all the spark plugs, cap/rotor (points if you have em), engine oil, and wires if they look old/worn.

Also check the timing and make sure that's accurate. Are you using the choke when you try and start it?

Btw it could easily be barely 166,000 miles on it and not 66k miles.

Also to clarify dose it do the redline thing when your just idling in neutral before you use the clutch or just when you use the clutch?

Welcome to the forum, there's tons of information to be had here. Have fun.

Edited October 25, 2009 by Z Tyler Z

[beandip]

First off don't just start throwing parts at your engine. Go to the parts store and buy a set of NGK BPRES spark plugs. No champions or AC. NGK . Plugs and Points will not act like what you are describing.

Check the linkage to the Carburetors something is sticking or not returning to idle. There should be two return springs attached to the linkage and connecting to the heat shield below the manifolds.

If when you do remove the Distributer cap and check the points , yes if they are pitted or burned they need to be replaced and replace the condenser also. But find out what is causing the drastic changes in RPM first. The engine still runs , only is erratic . Fix this first.

The problem with changing a bunch of things at one time, is that you will then not know what could be causing what problem. Fix one thing at a time. Once you figure out what is causing the RPM difficulty and you fix that . Then look to the ignition. So often people will go right to the ignition , do a bunch of things . That didn't work so they start ''adjusting the Carbs'' still have the problem , lets adjust the valves ! Now you have carbs that are out of adjustment and the same with the ignition and so on.

[Weasel73240Z]

I agree with everything beandip said about logically approaching repairs. But I think you should be concerned if those compression figures are accurate. 60 psi is bad, and 90 - 105 isn't great either. Could indicate a warped head, or failed head gasket (best case). But that wouldn't cause the car to run at max rpm, i think that's probably carb/linkage related.

[RB_eater]

Sorry if I wasn't clear enough, the car started redlinning when I pressed the clutch and released the accelerator. I already fixed that problem, it was a spring problem like beandip mentionned. However I'm woried the engine might have been damaged.

Also the engine isn't starting. Just after the incident, while it was still hot, it would start but I had to go full throttle to keep an idle. Now that the engine is could it will not start anymore.

I'll try a second compression check, I've got a cheapo tester and I'm pretty sure I forgot to open the throttle. Since I didn't know how high the numbers should be I was mainly trying to check if the compression was even between cylinders.

[IdahoKidd]

It sounds less like iginition and more like fuel delivery to me. Ignition isn't going to make the motor rev when you step on the clutch. A stuck slide in the carb will though. The load against the engine will keep the rpms down but when allowed to rotate freely will take off. I don't trust your readings on the compression test at all-no offense, but carefully take them again. I don't think that is the problem. It may be A problem, but it isn't THE problem here. You mentioned 'carburetor' and not 'carburetors' (plural). Does it have the dual carbs or is it a single carb? If dual, are they SU's? (opposed to webers', etc) If they are SU's, check the oil in the carbs (little black knobs on top of the carbs that unscrew). If the factory air cleaner is in place, remove the cover and stick your finger in each carb and see if the slides move up and down-push them up, they should return on their own. Check to see if the linkage moves freely and equally on each carb.

What is the history of the car? ie, setting a long time, modified, etc. How old is the fuel? There are a lot of folks here that can help and have way more knowledge than I do but it is my experience from when I started asking questions, the more exact information I could provided yeilded more exact answers and less "guessing". Many of the 'old heads' won't even answer questions that are too general. From the description in the first post, the engine racing and the battery drain are two completely different problems. As for the battery drain, charge the battery and remove a single fuse over night until your battery stays charged. The removed fuse will then point to the circuit in need and you can isolate the exact cause from there. Start with a known good battery (manditory)

Good luck, it can be over the top frustrating. As cumbersome as the 'search' is here, you can find a lot information on getting the carbs adjusted, oil level correct, linkage adjustments, spark plug color, etc.

Leonard

[RB_eater]

I only have a single, 4 barrel carburator. Holley if my memory serves me right. As for the history of the car, it has been slightly modified and yes it has been sitting for extended periods of time. The last owner had it in storage for most of the year. I've had quite a lot of minor problems appearing because of that but most of them have been taken care of.

Is there a good way to check if enough fuel is indeed making it to the engine? I know there is a decent amount flowing through but is it possible there is not enough? Sorry if I sound like a newbie but my other car has a turbocharged rotary engine in it so I've got a long way to go haha.

And I'll try your idea for the battery drain, thanks.

[IdahoKidd]

This is an "aha" moment. All conventional Z information concerning the carbs is off.

With the aircleaner off, look down the throats and rotate the linkage to open the butterflies. Be sure when you let off, they close completely. Do so with the help of someone actually using the gas pedal in the car as it is possible to have a bind of sorts on the linkage. Be sure the carb is securely fastened to the air cleaner. A vacuum leak at the base can cause wide open throttle symptoms even though the trottle isn't actually moved. Again, looking down the throats, rotate the linkage and you should see squirts of fuel from the accelerator pump. This will confirm fuel delivery to the carb, it still may have junk in the jetting. If the plugs were black and smelled of fuel when you pulled them, they are getting fuel.

An almost start accompanied by a wide open throttle run is, in my experience, a substantial vacuum leak. IF and only IF you are comfortable, after checking the mounting flanges and the manifold to the head bolts to see if they are loose, and checking to see if it starts, and if not, spray (or pour) a small amount of fuel into the carb with the butterfly open. Close the butteryfly, (no foot on the accelerator) start the engine. If it starts and runs wide open, shut it down. Vacuum leak. If it starts and runs, then dies, fuel delivery. If it doesn't start at all and you didn't put in so much that it flooded it, (if no start, open throttle and start) then there are other issues. The fact that it will run wide open throttle tells me that the timing is adequate to run, it is getting fuel, it has spark, and there is enough compression. While none of these may be perfect, the combination says it will indeed run.

BE VERY CAUTIOUS when putting fuel into the carb. Incorrect timing (to advanced) can cause a backfire and a brief ball of fire. Don't look into the carbs to see what is going on when cranking. Also, not a bad idea to have a fire extinguisher near by. You didn't say, but does this have an electric or a manual fuel pump?

Let us know

Leonard

[RB_eater]

I went and double checked the carb. It's indeed a Holley but I couldn't see any model number or name. Mechanical fuel pump. There is some fuel squirting out when I press the accelerator so I pump the pedal a few times and tried starting the engine. It didn't start so I tried again while keeping my foot on the pedal and I had a backfire. So I guess timing is also off? But from what the owner told me (and guessing by the 1k rpm idle) there is supposed to be an aftermarket cam in there which in turn could explain the advanced timing.

Another thing I noticed is that there is quite a few capped hoses, making a vaccum leak very plausible.

[IdahoKidd]

Hey RB, I missed in your post about the spring and went on about how to trouble shoot something you already fixed. Apparently I really do need glasses.

Too much fuel (pumping the throttle too much for example) can cause a backfire too. The aftermarket cam, without having the details, can throw off diagnosing the timing. Does the motor want to kick back on the starter in the crank cycle or try to diesel when it does fire. (I am trying to determine if it is too far advanced). With a hand held remote start button or an assistant, I'd start with rotating the distributor by hand as it is being cranked and see what I get for results. If it starts to crank hard, rotate it back a bit until you get it to at least run and maintain itself. Then get a timing light on it and see what your working with. If it ran before, it will run again. It may indeed need some ignition stuff done. Pull the cap off the dizzy and spay the inside of it and the top of the open dizzy with WD 40. Even though the WD is wet, it will clean up and dry out the components. Check to be sure there are good connections to wires at the cap and then at the plugs. I personally still think it is carb issues. I hate holleys. Just a personal thing. I never saw one out of the box that worked as well as a quadra jet out of a junk yard. Depending on the holley, one of things to check is the power valve. A backfire wipes them out as I recall.

Leonard

[RB_eater]

Alright time for an update. Sorry if I don't post so much but I can only work on my car during the week-ends as I'm in the military and currently undergoing infantry training.

So I changed all the spark plugs and now the engine WILL start but will only idle if I keep it at full throttle. Anything less and it stalls. Right now I'm thinking one of two options;

1. The spark is weak and since the engine only idles (draws little fuel) and the throttle is wide open (alot of air) is creates a lean mixture that the weaker spark can ignite. Therefore is would be an electrical issue. Makes a lot of sense since everything started after I installed that battery guard device.

2. There is some other problem (most probably carburator related) that kept the engine from running correctly and somehow created enough dirt on the spark plugs to keep the engine from starting at all. Since I changed the plugs the engine will start but the root problem is somewhere else.

I'll have more time tomorrow to work on the car. In the mean time if anybody has any ideas let me know. Thanks to everyone for the help so far.