engine dies when i pull out dipstick

[saridout]

is it normal for the engine to die when the oil dipstick is removed? cause that's the problem i'm having.

[Z Tyler Z]

Removing the dipstick allows air into the engine that isn't being "counted" by the AFM and that's why it's dieing.

I'm almost positive that my 76 doesn't die when I remove the dipstick while the engine is running. The RPMs will drop a bit but it stays running. What does your car idle at? Does it stall then die or just die right when you remove it?

[Zs-ondabrain]

Better question, Why would you pull the dipstick WHILE the engine is runnig?? You can't get a proper measurement unless the engine has sat, not running, for at least 5 minutes.

Or am I confused?

Dave

[IdahoKidd]

Funny this is brought up. I just had lunch with an old datsun mechanic who was looking my Z over. He mentioned a couple of things to watch for when it runs rough. One is that the dipstick has to have a tight seal and the other is that the oil fill cap gasket can go bad and cause idle problems. He said the vacuum on these old cars was so sensitive that any loss would cause issues that seem nearly impossible to find.

Just this weekend, I started my turbo motor in my 280Z and it wouldn't hardly run. I had taken the power steering pump bracket off, leaving the open fuel pump boss without a cover. Covered it up and it runs! Not particularly well just yet, but it runs.

[GreenZZZ]

I was hoping this thread was sick off color joke... Instead I found a legitimate technical discussion. Prurient dipstick references obviously does not belong on this thread. Go here instead...

http://www.google.com/search?hl=en&source=hp&q=dipstick+joke&btnG=Google+Search

[saridout]

What does your car idle at? Does it stall then die or just die right when you remove it?

i idle at about 650, and it sputters and stalls about 10 seconds after i pull the dipstick. i've just rebuilt it, and it's been running a little rough ever since.

Zs-ondabrain: i pulled it on a lark, and i hadn't even moved it an inch out of the block when it started sounding dramatically different. i pulled it out the rest of the way and it died seconds later. my dad had never seen this behavior before in a car, and he flipped out, so i flipped out, cause i've spent the last 6 months rebuilding it. and here i am.

IdahoKidd: thanks, that's helpful. it seemed like someone had once told me to check the dipstick for vacuum leaks when trying to fix a rough idle, but i haven't been able to find anything on the forum that mentioned that.

does anyone else's die under these conditions?

[WingZr0]

Totaly normal. Both my 78 Z and `83 BMW 320i do it. Some newer cars it simply runs rough or struggles. All your doing is creating a disturbence in the engine vacum, simple as that.

[saridout]

Totaly normal. Both my 78 Z and `83 BMW 320i do it. Some newer cars it simply runs rough or struggles. All your doing is creating a disturbence in the engine vacum, simple as that.

ok thank you i think i'll stop having a heart attack now, then.

also, does anyone know what kind of seal is on the dipstick, and if it's available anywhere?

Edited January 13, 2010 by saridout

[Bonzi Lon]

From all the Datsun dip sticks I have, they appear to be hot molded rubber, probably around barbs on the shaft to keep it in place. Never cut one open. There will be a certin distance between the end of the stick and the top seal of the dip stick plug. If the rubber plug is defective, either by air leakage or not firmly attached to the metal stick, I would replace.

Bonzi Lon

[saridout]

well shoot, i can get a brand new dipstick for under 12 bucks. i'll just do that. thanks everybody, this was really helpful.

[conedodger]

I agree with the several who have called this normal. You create a big vacuum leak when you do that and it kills the motor.

You mention that you rebuilt and that it is running rough. Did you stick an aftermarket cam in? The stock injection on the late '75 on with LJet does not respond well to loss of vacuum signal. Most of the aftermarket cams I have seen will give you very little vacuum.

[saridout]

Did you stick an aftermarket cam in?

nope. aside from a 20 over rebore and a replacement identical head, i haven't changed anything. it ran much rougher before the rebuild, in a different way. now it kind of misses and lopes a little, but never dies like it did before. i keep finding vacuum leaks and fixing them, such as the injector seals, and it improves incrementally with every leak i find. this could be just another one.

my dad has worked mostly on german cars in the past. is the engine dying when the dipstick removed something that doesn't occur in german cars?