Carb problem... I think. Ideas?

L

Los

Low Mileage
Greetings,

This is my first post to the forums. I appreciate any help!

Several months ago I bought a 1979 X from a local driveway. First things were first- I replaced all the hoses, clamps, changed oil, trans oil, etc etc... I bought a new carburetor and the install, and operation have gone beautifully.

All was good in X land for about two months. Then the problem started. Let me explain the symptoms best I can...

I turned off the highway, and slowed to a stop at the first stoplight. When I went to go I felt the engine uncharacteristically start to hesitate, and sputter. Acceleration was underpowered, and the rpms ran high, but I was a half mile from home so I limped in. When I clutched the engine stalled immediately. Trying to start the engine again it wouldn't unless I laid heavy on the gas, and even then it would hunt between 3.5k and 5k. As soon as I let off gas it stalls.

Since then I idiot checked all the lines and clamps thinking I may have bumped and jostled something loose, but it appears that all is tight and the same as before the problem started.

Start the car, it will turn over to about 4k then stall out immediately.

Two interesting points. I was about to give it a rest for the night, but before I did I tried to turn the engine over (hoping in vain) that the problem would evaporate. The engine started, and help exactly as it did when it worked for the previous two months. I went ahead and test drove it. Made it a mile. Then the problem started again. Go figure...

Things I have learned. If I manually hold the butterfly valves closed on the carb the engine will start and keep going. In other words, if air is constricted the engine won't stall... As soon as I let more air in it stalls.

I have adjusted the mixture to see if it has an impact, but the nature of it stopping, then starting to work again leads me to believe the problem is different. I changed the fuel filter, and looked for fuel blocks. I sprayed the carb down with carb cleaner, too.

Any thoughts? Heres a picture of the setup. Not sure how to frame the problem- so any comments or suggestions are welcome!
 
Sticking E.G.R. valve perhaps.

Exhaust recirculating valve. It sounds like what mine was doing many years ago. It's been so long however, that I don't remember what the symtoms were. Others will chime in no doubt.
 
check the jets? one might have shook loose flooding the engine?

or you could be experiencing vapor lock
your choke might be set wrong
 
If it runs when you choke it it sounds like it is getting too little fuel. I think I had a similar problem. Mine went away after exchanging the accelerator pump diaphragm and cleaning the carb. If your carb is new I guess the diaphragm should be ok (pump housing looks dry on the photo). Perhaps some dirt entered when you connected up the new carb. There is a filter that should take care of that though...
If you haven´t already, taking out the jets and inspect for blockages sounds like one thing you could try.
 
When I had this issue on my 79

I first took out my jets and cleaned them thoroughly. Make sure you don't mix them up, they have to go back in the same order they were removed, and be careful not to drop any tiny screws into the carb! I poured some Seafoam brand carb cleaner down the carb and it cleaned it up pretty good. I also cleaned out the little filter screen that is on the back drivers side of the carb. Poured a can of the same cleaner into the gas tank each time I filled the tank for about three weeks. It drove much better after all of this. I had the opportunity to move up to a single DCNF carb shortly thereafter and liked the performance much better.
 
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Carburettor hose set up

Did anyone notice that the Gas tank has no vent lines from it the two lines that go to the vapor separator are linked together with one hose so the gas tank is not getting any air in it. I have the same Carb. on my x will take pic. and post it later tonight at work now. Did you replace all of your fuel lines also?

Here is how I have mine set up and plumb.






As you can make out in the pic that I have removed all smog equipment and Glup valve with the exception of the Carbon trap that is used to vent the gas tank. Yes I still pass the smog test here in Portland Oregon with a hc of .001. If you have the Haynes book look on pg 61 for venting your tank, and pg 171 for vacuum controls. I hope this helps :2c:
 
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jlpatton said:
Did anyone notice that the Gas tank has no vent lines from it the two lines that go to the vapor separator are linked together with one hose so the gas tank is not getting any air in it. I have the same Carb. on my x will take pic. and post it later tonight at work now. Did you replace all of your fuel lines also?
Click to expand...


Thanks for the input. I am not sure they are the same carb- Mine doesn't have the shutoff solenoid, it has two butterfly valves for the choke, it doesn't have the line going on the top to vent, etc...

My carb is the DAT34 from Bruce. ( http://www.fiatparts.com/carbs.htm -- -- Number 4)

Given the carb worked for two months of driving it is curious that it would just stop. The setup worked for a bit even though it is obviously amateur. Could vapor lock all of the sudden become a problem if the weather changes from moderate to a lot warmer during the day? I had figured that the engine gets way warmer than the outside air even on colder days- so how could not venting my gas tank (as shown in picture) cause vapor lock all of the sudden?

How should I vent the gas tank effectively?

More later.

--Glenn
 
Hi Los

Let me ask

On your car you have air pump and EGR valve? (gulp valve) my X1/9 has same simptoms also I replace the carb for an other and same problem, I checked the (gulp valve) and that was my problem, I replace and my car runs smooth again.

To check this valve is easy just you need a couple minutes just disconect the hose from the intake and blown like to inflate a ballon, if you feel the air pass freely your valve is broken and this is your problem.

Hope it helps.

extrasmallrbrbadgezv7.jpg

Ricardo
X19/79
 
Fixed it!

Removed the gulp & egr valve. Plugged the hole on the air intake. Cleaned the carb.

Between doing those two things I'm back on the road!

Thanks everyone!

Glenn
 
Hey Glenn... welcome... and sorry for your trouble...

... but I betcha a dollar to a donut it happens again.

My bet is there is something fouling a port or emulson tube/metering rods in your carb.

If and when it does reoccur... pull the four rods/tubes first and place them in ORDER on a clean white rag. Carefully blow them out and also the ports they came from. If it clears the problem but you don't find any SPECKS of dirt... then its probably still in there and only a carb boil-out will fix it.

You might wanna pull the pickup tube and sending ubnit outta the tank also and see if the sock is still intact and that there is not any crap or varnish accumulated. Same would then go for the fuel filter. I uses cheap clear ones (two in parallel, mounted horizonatally, one above the other) so I can actually SEE whats going on. (More details if wanted...)

Anyway... good luck and I hope I'm wrong and your problems are clear for some time...
 
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