Engine revs up then dies upon starting within seconds

[old521]

1972 Datsun 1600cc engine with Weber two barrel carb. for some reason all of a sudden when you start it up, it revs high and dies within seconds. You can manually almost choke it to death and it will actually keep running for a little while longer....thermostat housing for automatic electric choke gets extremely hot. I can not find any air leaks in hoses.....replaced fuel pump. I presume it is a vacuum leak somewhere, but am unable to locate it. Any ideas?

[H5WAGON]

Did this problem just start, or Is this a car that has been sitting......:o

 

More details. What part of Portland?

[old521]

Did this problem just start, or Is this a car that has been sitting......:o

 

More details. What part of Portland?

 

 

Been driving it nearly every day for a week. It is a 'daily driver'. The most it sits is maybe a week at a time. We rotate vehicles. Problem just started. Runs for maybe 3 - 5 seconds at high rpm. New carb about a year and a half or so. Replaced plugs, cap, rotor, points, fuel filter and fuel pump the other day. No change. Ballast resistor ok. Coil getting voltage continuously. Just seems like it is getting too danged much air. Carb appears to still be mounted tight. Been using 76; 92 octane consistently. Wife said it started acting up on way to gas station; then went totally bad after being filled up with only about 4 gallons. Not sure if I can get it to run long enough to see if spraying WD40 will indicate anything. Have another one, (1971) and no problems with it.

[dryheat]

I had a similar problem on my Weber. Inside the fuel inlet barb I found a small filter screen stuffed in there that was plugged beyond belief. Once it was removed the problem went away.

 

Also maybe check your idle air screw next to the accelerator pump ... take it out and stuff some carb cleaner through there. The smallest piece of debris can really make your carb mad.

[old521]

I will have next Tuesday off from work and will try the suggestions. I do not have a garage, and it will probably be raining and of course will be dark when I get off work. In the meantime, will drive a big 1977 LTD with horrible gas mileage! Will let you know results. Thanks.

[datzenmike]

It's getting to that time of year, cool and damp. Water is in everything. Go to Wall Mart paint dept. and buy a $4 quart of methyl hydrate. (wood alcohol) This is the same stuff you pay a buck for in small bottles for gas line anti-freeze. Throw a cup full in your tank. Water and gas won't mix but alcohol will mix with both and absorb the water allowing the water/alcohol/gas to be run through the carb and burnt instead of collecting in the tank, lines or bottom of the carb bowl.

 

Sounds like a filter blockage or perhaps water blocking a jet.

[H5WAGON]

Does this car have a electric choke?

 

Are the screws tight on the choke adjustment.

[H5WAGON]

I had a similar problem on my Weber. Inside the fuel inlet barb I found a small filter screen stuffed in there that was plugged beyond belief. Once it was removed the problem went away.

 

Also maybe check your idle air screw next to the accelerator pump ... take it out and stuff some carb cleaner through there. The smallest piece of debris can really make your carb mad.

 

 

Check float level and valve...... while you are inside the carb....:cool:

[banzai510(hainz)]

whats your voltage? ck that. hopefully it isnt over 15volts.

 

now does this motor stay running if you feather the gas?

 

I would open up the idle jet ans see if its plugged.

 

also as Mike stated, if the fuel hose in the wheel well is loose water can run down in there. If its been rainey a whole lot. makew sure the clamps are tite. also dirt gets in there also. so change out the gas filter more oftne in the 521s

 

make sure the distributor cap is dry under neath

[old521]

Thanks for all the ideas people....I tried every single one of them....tore the carb apart; including the jets...blew every passage with carb cleaner....everything seemed clear...checked voltages....seemed to be ok everywhere...put antifreeze into tank....after burning up nearly a quarter of a tank, it seems to be getting a little bit better....I can now 'feather' the pedal to keep it running, and it does not seem to be revving up so high....still dies though....almost tempted to think that there are a couple gallons of water in the tank.....I dunno....never had an engine rev up when there was water in the tank though....sprayed WD40 everywhere and nothing changed....been raining all day and only 12 degrees above freezing....could it be that a valve got stuck or something? Hate to drain the tank at over $3 a gallon.....we could only find HEET antifreeze stuff; and put one container into the tank....should I try a second one? Walmart does not carry what was recommended....guess Home Depot does though...At the very beginning; I thought it was a problem with the gasoline, and at this point; am thinking it is again...I can not remember an engine speeding up then dropping down in RPM because of bad gas though....every frickin' filter was clean on this critter....maybe a head gasket problem?! Although the water is not dropping down in the radiator and the oil shows no water...uggghhhh!

[SRSANDS]

Sounds like a vacuum leak does it stay running at high idle choked fully

[Roger]

I'd say check the return spring in your vacuum advance. Check your timing. check to see if the carb is fastened on the intake securely. tighten the inteke bolts to the engine.

[old521]

I don't anymore...it used to stay running if it was almost fully choked....It definitely was not the fuel......just before I was going to drain the last couple gallons; a new neighbor called the cops; complaining about me 'revving' the engine repeatedly....at 7:30 at night...(it has a good muffler system on it)....I did spray WD40 all over the place and could not detect any vacuum leaks....next week I will try tightening up the nuts on the intake manifold...kinda hard to check the timing when the engine will not keep running...dwell seems to be fine...it does seem to be a vacuum leak from what I can tell...but ....it stops firing after intitial starting....ignition switch seems to be providing the voltage to the coil though....and likewise to the distributor...50 years and over 30 vehicles; this is the first one I can not get running again! I am at a loss and all suggestions are appreciated! I did disconnect the line from the tank and pump and blew out the line.....replaced all hose connections....replaced the pump; replaced the points; the plugs; the cap; the rotor; tore the carb apart and blew out all passages; have to think about how you would check the spring you are talking about...thanks guys...my gut feeling is that it is electrical....I hate working out in the rain! Oh...put new fuel in.....same results...

[wayno]

Hi there old521, Check the PCV valve on the intake manifold. When mine went bad it had the long hose still connected to it and I could not hear the major vacuum leak created because of the hose muffling effect. To this day I have no idea where the guts of that valve went, they were not in the hose. The truck was undrivable without it. wayno

[Sealik]

Vacuum gauge is a must....under 10 bucks.

Very handy tool.....takes the guess work out of any possible leaks.

Also good for other diagnostics

[old521]

I can 'feather' it to keep it running for awhile....closing the choke makes it rev way up now....I replaced the PCV valve...re-checked everything I could think of...even changed the timing a little bit....cranked the nuts down on the carb to manifold....cranked on the ones on the top side of intake manifold....checked spring in distributor....am thinking the carb is flooding..

[old521]

I put gas stabilizer in the gas tank 7 months ago and waited until JUNE 8, 2011... ..I had taken the carb off a couple times before and cleaned it out and nothing changed....took it off today, and started taking the spacer's off....the bottom one had a loose bolt....I have been working on cars for over 30 years....I could do nothing but hope that was where the leak was....sure enough....put some sorta mild thread locker on all the screws when putting it back together....blew out tons of white smoke upon starting the engine....(water)....even with the stabilizer there obviously was a lot of water in the fuel...the house next door disappeared in the cloud that lasted for maybe 3 minutes....the spacers I am referring to are added when you put the

Weber carb on....I thank all of you for the help offered....this simply was a screw-up on my part evidently....

[Skib]

even with the stabilizer there obviously was a lot of water in the fuel...

 

 

so put fresh gas in it :blink:

[banzai510(hainz)]

mack sure the intake is tight as thats where the water can come in from. the intake manifold has water passages

[old521]

Everything is tighter than a drum....had sprayed so much wd40 on the whole thing it took a while for it to burn off.....still surprised I could not detect the leak when spraying over and over.....the carb sits on two spacers that you add; so maybe I did not go low enough....it had almost a full a tank of gasoline in it.....dumped a full container of stabilizer in it last November.....my wife almost fainted because of the huge cloud....just love the ethanol they force us to pay for....drove it ten miles and it runs great again...it took a year an a half for that bolt to loosen....there are four of them that hold the second spacer to the first one...one other one I was able to tighten a little....the other two were ok....have an identical carb on the other PU and have had it on for umpteen years and no problem.....sooooo; everything on wheels runs again over here....

[Skib]

lolzwut? :huh:

[Uncle Laulau]

Thanks for this informative post. I learned a ton reading it. I just got done putting new gaskets on my weber. I have only one spacer or adapter plate, and I made a new gasket for it and put a little gasket sealant on it. I will be sure to check the bolts from time to time. Hope your neighbor and you two are happy that the truck is up and running again. Wow to call the cops on a guy working on his truck in the rain, golly. People sure are afraid to talk to each other these days, calling the cops for that crap. Man geesh.

[old521]

Been here for over 32 years....they moved in just a few months ago....whatever....

 

Yes...this carb has an adapter plus the spacer....the bolts that gave the problem were between the spacer and the adapter...you use an Allen wrench to tighten them up, and I was totally surprised that I had not tightened a couple of them enough....Having had nearly 40 cars over the years and working on all of them, I was very surprised that I messed up....I have not used any gasket sealant on the gaskets...hate making new gaskets when removing things!...I guess if the bolts come loose, the gasket sealant might save your butt though....

 

Have another 'neighbor' with a 'classic' car that claimed he 'loved' carburetor problems....after an hour or so; he gave up trying to find the problem....

 

Again....I will say I appreciate the fact that many people on this web site tried to help me with this situation...I did not know where else to ask for help....I tried everything suggested that I could do....but the moral support was what really kept me going on this danged thing! We now have two 71/72 521's back on the road!

[ggzilla]

Good to hear, two more datsuns on the road!