View Full Version : Backfires + Stalling Problems

12-01-2006, 08:13 PM
I have 1972 Series III and it is my first car. I have been working on it for almost a year replacing many parts. I finally got it on the road beginning of the week and the first big problem has occured and I need some help.
It starts and idles fine but when i try to go to 4th gear the car starts to buck rapidly and I am unable to accelerate. Even when I down shift it continues to buck. When I pull over and stop, I stall and have trouble starting again. When I do get started the same thing happens again and sometimes it back fires. I called Rovers North and they said it sounds like the Carb but I just intalled a new Zenith Carb. Does anyone have an answer or have any ideas of what the matter is? I would greatly appreciate the help. Thanx

Dan Dixon
12-02-2006, 02:33 PM
Hey Cody,

No idea what is wrong, but try isolating components when experiencing the problem. Does it run OK when it starts "bucking" and you push the clutch in? That would indicate something wrong from the clutch rearward. Things like that. Do you have any air leaks in the manifold/exhaust system? could be backfire material as maybe ignition timing. Make sure also your ignition system is working fine. particularly under the distributer cap. If when you stall, try this; leave the key in the on/run position open the hood and pull off the distributer cap. Put the moving side of the point on the flat of the distributor cam (points closed) if it is not already there. With a small insulated screwdriver, so you don't get shocked or ground the points, open and close them. You should see a strong consistent spark arc across the points gap. It should be present and not going to ground elsewhere. That being the case, and your fuel delivery and mixture is OK, then it should start right back up. These are just some ideas if your quest proves fruitless. But under no circumstances give up. I have a '72 series III as well and love it. There is no problem that cannot be figured out. Hopefully others will have suggestions that may be more useful.

12-02-2006, 02:44 PM
At least a couple of things worth checking:

1. The carburettor - I got a brand new Zenith carb a year ago to replace an aging leaking Weber and it caused horrendous bucking. Tried adjusting the float and clearing the jets/tubes, made sure the pump was clear, diaphram etc all to no avail. Ran fine with the old Weber. Eventually junked the Zenith (I heard they are now made by another company?) and bought a new Weber and it now runs great.

2. Check the point very closely. Given the low cost, install new ones if you have not already...or go electronic with something like Petronix and you can walk away from one regular source of frustration! If you have even a little build up on one side of the points it can make a mess of running at speed, at least in my experience. I would start here before delving into the carb.

12-02-2006, 05:57 PM
Are you using the original fuel tank, etc. If so, there may be rust and gunk accumulation blocking the pickup tube, etc or the pickup tube could have a small hole and it's just sucking air. Pull the pickup tube and put it in a can of clean gas and see if it will run. Then trouble shoot from there. In any case, put an inline filter in the system. The glass bowl filter really only screens out rocks.

Peter O.

12-02-2006, 08:12 PM
First thing to check is that the carb is actualy getting fuel. Take the fuel line off the carb and put it in a cup/bucket. Disconnect the coil and crank it. How much fuel (if any) is coming out. Another option is to put in a clear inline fuel filter so you can quickly see if fuel is actually getting to the carb.

If you are not sure if there is enough fuel being pumped, take off the fuel tank pickup pipes and blow them out with an air compressor. I had one that was partially plugged and gave me fits like you describe. Worked great at low rpm's but once they started getting up there, it would buck and spit like a bad clutch.

Next, if you want to test for the fuel line sucking air, start the car but disconnect the fuel pickup line simulating you running out of gas (on mine, I have a shut off valve). Once it cuts off, hook the line back up. Now try to crank it. If you cannot get an fuel back to the carb, you have an air leak. Not enough "suction" to pull the fuel back to the carb. Again, been there, done that.

If all of these pass with flying colors, I would still say it is fuel related. Check that carb again. Something is out of whack (floats, etc). Since you have a new carb, I would guess that it is one of the other areas feeding the carb.

The only thing left is the fuel pump itself. You would need to test it by either having a pressure meter or time it by filling up the cup while cranking it for a specific length of time and see how much fuel there is. I can't remeber the specifics on this one. I think the pressue is 4psi. As for how much should pump out / min, just can't remember.

12-03-2006, 03:56 PM
Thanx for all of the replies!
Today I checked the fuel pump bowl and there was about a 1/2 inch of rust and gunk. I also checked the Carb and it was fine, but the filter between the line connecting from the feule pump and the carb was all filled, on the fuel pump side, with gas that looked like... well diareha. Also I drained the gas tank and when i unscrewed the drain screw gas was dribbling out so i punched a screwdriver up and a whole bunch of gunk (same in fuel pump bowl) came out.
Is it worth trying to clean out the old tank and use it again or should I just buy a new one? If I should keep the old where is usually the best place to clean it, see as how I can't just clean it in the street or in my driveway? Thanx for the help

12-04-2006, 01:34 PM
If the tank hasn't rusted through and is in good condition other than the crud inside, you might want to consider reusing it. Many radiator shops have a tank relining service that cleans and lines the tank with a coating that will keep it from getting cruddy again.
There are two major suppliers of Do I Yourself tank liners. POR-15 and Creem. Both require quite a lot of labor and use harsh chemicals to strip and derust the tank. Their advantage is that they're inexpensive. I've done it both ways and it's by far easier to take it to a shop and have them do it.

12-04-2006, 04:49 PM
I used the POR-15 product and they are quite good. To save time, I would take the tank to a radiator shop and have them clean it out. That will save you a ton of time and work. Then use the POR-15 relining product. I had one tank that had gas in it for approx. 3 years. I cleaned it out and lined it with the POR-15 product and it is working great. These products will also fix small leaks as well.

12-05-2006, 11:56 AM
por -15 good product and it works well.marc

12-12-2006, 08:51 AM
You could just try and keep replacing the fuel filters frequently...and see if that works enough of the rust out of the system. My 73 Series III sat for awhile before I got it, and I've been switching out the fuel filters every few months, because I had the same clogged filter problem...then again, I don't think mine looked like diarrhea..ewwww. Hehehe.


Jeff Aronson
12-18-2006, 06:16 PM
When the fuel bowl shows crud, there's plenty more in the tiny orifices of the carb - even a new one. You'll see my story on this problem in the January issue of The Rovers North News. My fuel bowl looked like a parfait jar. Every so often I still get a stalling after filling the tank, so I know there's more stuff in there.

Do check that your intake manifold nuts, particularly the hard to find one under the manifold, are tight. If you're sucking in too much air, you'l lean out the mixture so much the car will run very poorly under load.

Also, make certain the points are gapped correctly and are clean on both sides. With the engine running, take a spray bottle of water and spritz the spark plug wires and the coil to distributor wire. If anything starts to run poorly, there's another culprit. Replace the set.

Good luck,