1972 240z 3rd gear+ violent loss of power

[Cutlass372]

Hey everyone, over the past few weeks my car has been running progressively worse. I just replaced the spark plugs with new NGK BP6ES plugs and it took away the problems I was having in 1st and 2nd gear (at 5k rpms it would hit almost like a rev limiter, but keep revving sporadically). It was doing this before, but it seems like in 3rd gear or higher it get this violent loss of power and the tach jumps all around. It kind of surges, as if you let off the gas and stomped on it again over and over until you shift or slow down. I think the timing is set around 15 degrees and I am running the pertronix unit and their coil. This isn't something that has been happening for a long time and I don't recall changing anything or making any adjustments prior to this happening. What are your suggestions, Where should I look. Thanks in advance for any help. Any information you can provide would be greatly appreciated.

 

Thanks, Elliot

[Cutlass372]

I took a couple of videos of whats going on. I just replaced the fuel pump and the problem is still there. I also blew out the fuel lines and that didn't help either. I will add captions to the videos so it's easier to tell whats going on. In video 27 I was in 2nd gear I think and around 5k you can hear the limiter type situation. It does it in second gear now too and I am limited to about 55-60mph now, which is really becoming a problem for driving on the highway.

 

Here is the link: http://www.youtube.com/user/Cutlass372

 

Clogged fuel tank or electical problem? Float bowls to low? The strange thing is that it came out of the blue. Does it seem like its missing or running out of gas. Let me know what you think.

 

Thanks, Elliot

[srgunz]

Well when it starts to missfire you can see the tach jump around.

That tells me ignition. IMO.

Photos of coil, inside of dist. cap, inside of distributer, wire from coil to cap,

points, condenser, etc will all help.

[Cutlass372]

http://good-times.webshots.com/photo/2688601330063370706saFUXY

 

These are the pictures I have at the moment, just hit next to see the rest. I have since removed the condensers and the other unwanted grounds. Also, I removed the wire I had connecting the green/white and black/white together and just attached them. I am running the pertronix ignitor and their coil without the ballast. Let me know what other information will help figure it out the problem. I still cant seem to figure this out..

 

Thanks, Elliot

[srgunz]

Get ahold of pertronix tech help online or call.

The magnetic wheels are known to go bad. They may send you a new one.

Also check for shaft play and make sure the wheel is not hitting

the pick-up coil. Also the wheel and the pick-up have to be kept clean.

[Cutlass372]

There doesn't seem to be much shaft play, but the dizzy does seem to wobble a little if I start to push on it. Maybe the o-ring is bad at the base of the dizzy? Could this cause a problem like this? All of the magnets still seem to be in place and the tape is still tight. The wheel and pickup are still clean and there is minimal shaft play. Is anyone local that might be able to help me out? I need to figure this out because this car is my DD and I have to go over 55 mph some times. Any other ideas may help so please keep them coming.

 

Thanks, Elliot

[Ineptitude01]

Ah, crazy tach... my favorite!

 

I just had a very similar problem on my 82 Turbo with the Z31 ECU swap. I realize this probably doesn't apply since it doesn't sound like you have an electronic distributor, but on my car, it was the CAS that was bad. It was failing intermittently and dropping spark under load. That was what was causing my tach to jump around like that. Incidentally, I was using a Flamethrower coil at the time. I've since upgraded to the Z31 coil and I'm much happier with it. Never gonna use another Flamethrower on anything.

 

I would double check all your grounds, and try a different coil. Doesn't sound like a fueling problem from your video.

[Cutlass372]

I will check all the grounds again, but I did clean them up not too long ago. I wish that someone was close enough that I could try a few of these parts without buying them all and not needing them. I don't have the money to keep throwing parts at this and having it drive like **** still.

[Tony D]

Buy a multimeter instead of parts, and start checking things out instead of replacing them. When something else happens down the road, at least you will still be able to use the multimeter.

 

What's the gap on the plugs? What is the resistance of the plug wires? What is the power to the coil and pick doing when this happens?

 

I had an intermittent heat problem which caused a water injection unit in the car to make the electronic ignition in my car do strange things like that---tach went crazy, backfired and popped like a points car with a bad condenser.

 

Don't know where Doylestown was, but I was in Export and Jeanette a couple weeks ago...

[Cutlass372]

I have a multimeter. With the red lead connected to the + on the coil and the black lead to a ground I get around 14-15 when idling. I think the gap is set at 30 or 32 (leaning towards 30). How would I check the resistance at the plugs? It seems like the problem happens under load so I don't know how I could test it when the problem occurs.

 

Thanks, Elliot

[Cutlass372]

Anyone else? Still having this problem after multiple attempts at fixing it. I am going to pick up a set of spark plug wires tomorrow and see if that helps anything. I cleaned up some more wires with no help and the problem only seems to get a little worse.. I'm going to clean the grounds again tomorrow as well. Let me know where else I should check.

 

Thanks, Elliot

[hoov100]

Tighten down the bolt that holds the dizzy on and try and wiggle the dizzy shaft with your fingers. If it wiggles alot, the bearings in the dizzy are gone. Secondly, check for shotty wiring and corrosion, have the coil tested, and check the magnetic pickup for damage/cracks.

[Tony D]

Does it happen when the car is stone-cold?

[Ineptitude01]

Just had a thought, does a BP6ES seem a touch cold for a plug on that engine? (I'm assuming non-turbo). It's the same plug I'm using, but I switched down to that because the 7 plug was too hot for my comfort under boost. If memory serves, shouldn't an NA L-series use a BPR7ES-11?

 

I'm new to carbs myself (just got a '67 roadster ), but it seems like they should use plugs in the same heat range as a fuel injected motor of the same specification. Come to think of it, the BP6ES is going to have a relatively close gap (I think .026"?).

 

Probably getting a lot of the NGK nomenclature wrong - but I've definitely had some funky spark plug related issues in the past.

[Cutlass372]

I think the NGK BP6ES is supposed to be gapped around .030-32ish. Maybe I should try to go a little tighter?

[Tony D]

No, the larger the gap you run the smoother the car will idle.

Your gap is NOT based on the PLUGS, it is based on your ignition systems capabilities.

 

Small gaps were for points-style ignitions. When they went to HEI (transistor standard in 1975 on) then the gaps got bigger.

 

A turbo car may run gaps as tight at 0.018" due to spark blow-out issues, but an NA should be in the 35-45thou range with a decent ignition system. If you still ran points, then 25-30 would likely be the biggest you could go and get reliable fire from them.

 

My 73 240 with a pertronix setup and flame thrower coil runs 0.045" without any problem whatsoever.

I have another with a crane xr700 and it's gapped similarly.

Even my VW has large gaps, and it's got one of the first per-lux ignitors in it!

[Lazeum]

I had a similar issue no later than last week: no power in 3rd gear and higher gear, tach bumping with low rev.

Engine setup is L28 with custom head, 3x40DCOE, NGK BP7ES all gapped at 0.035", Mallory Unilite ignition with Mallory HyFire 6AL (MSD 6AL equivalent), 5sp + R200 3..9

 

I found out the connection to the resistor was almost cut, one or two wires out of 10/15 holding the connector remained ok. I fixed it, rev is now steady.

 

Regarding the loss of power, I found out I was running out of gas. It does not happen in lower gear since there's enough gas in the bowl for the quick accelerations that does not last long.

I then connected an electrical pump to support the mech one, problem is now solved as far as I'm concerned (I will removed the mech one since it could be a restriction now in my case)

So I believe in your case, it could be the pump (elec or mech) that starts to go bad or which is not sufficient. To try that I would suggest releasing the gas pedal for some seconds when you got the issue you've described and try to accelerate again afterwards since bowls should now be full again.

Edited July 5, 2010 by Lazeum