On the way to work this afternoon my 235 started dogging about 100 yards from my house. And in the 8 miles to work I pulled over 4 times, because I kept losing power. Last night when I came home I had no problems, in fact the motor has ran good for years. I checked to see if the choke flap was closed, it wasn't. The gas filter was getting gas. Now the thing is when I rev the motor its fine its just when I have to give it a little more gas as I'm driving that it that it wants to die. but not all the time. It was worse when I first started it up and as I got on the Fwy too. Another thing I noticed that it just started doing is popping and such both when I was revving the engine and while I took my foot off the gas as I was going down the fwy (the Fwy is flat). And while this sounds cool as hell it just started to do this today. Does it sound like its running rich? and why would it start doing that all of a sudden? The only thing I did yesterday is get gas 15 miles before I got home. I'll try your ideas here at work and hopefully something will insure I get it home tonight Thanks for your help
1,,bad gas,,,,points,dist.,,,fuel filterif pluged on a long run it dont get the gas it needs.,,,,,,,,,,,,,,alleyoop
I had an old 55 chev that did that an i found that the resistor wiring going to the coil would break down as i drove it finally went completely out and the car would start but not run when youlet off of the key. what is the 235 in some of the older cars had an ignition resistor from the battery to the coil
Plugged exhaust? Late cam timing (i.e., slipped chain - or, do the 235's use gears?)? If so, you're probably getting a "roar" from the intake that wasn't there before. C'ya - RAY
I had a similar problem with my 48 pick up and it ended up being the resistor....my options were to replace the resistor, but an HEI distributor put an end to that problem for good, so I'd look more at either a bad resistor (if that's the way your car is set up), or the gas situation (either bad gas, or parially blocked filter.......OR a pump starting to **** air instead of gas). Again these are where I'd start the search
Mechanical fuel pumps can work/not work for a long time before going out completely. Had one going out on my '70 GTO when I was a kid. I would have to prime it with gas down the carb to start it in the morning, then run all day fine. The next day do it all over again. Your description of popping, sounds more like ignition though. Bad vacuum advance can give backfires when trompted on at highway speeds. Tony
It's gotta' be air, fuel, or spark. Sometimes a combination, but if it happens all-of-a-sudden, probably just one. Try a compression test. That should find broken stuff (timing chain, broken piston, etc). Hook up a vacuum gage. If it has idle vacuum, then there's no problem with leaking manifold, torn hose, bad intake valve, etc. Then the 'air' part of the equation is ruled out (unless someone else comes up with something I missed... which is likely. But oh well). Checking for 'air' (air leaks in intake, or broken motor) usually isn't too hard to do, doesn't take much time, and keeps me from chasing a problem when the basic engine is ****ed up. Try hooking up a propane kit and try driving the car w/ a buddy manning the propane. If extra fuel fixes the problem, or makes it a lot worse quickly, that'd indicate mixture malfunction. I'm a big fan of the propane test; quick and easy. I like quick and easy. Re-reading post; check carb bowl for ****/water. Another possibility. Quick and easy to get lid off carb (unless you screw the lid gasket up). Or just check the filter if it's gl***. Bad condensor on distributor? Had one on a slant 6... wouldn't cruise. Idle okay, WFO okay - anything else: no dice. Old guy at the NAPA figured it out in 30 sec. from my description of symptoms. We need more old guys at NAPAs today... I don't know quick/easy ways of diagnosing poor ignition performance without a scope. Pretty expensive stuff for DIY backyard guy. And I never really got that fast at using 'em. I generally just did visual inspection of secondary ign components and pitched any wasted plugs, caps, rotors, wires. Or any plugs that said autolite... Bad vac advance can? Just plug the line off and run the car. Should lose some power at the conditions where it isn't getting the advance, but probably run 'okay'. That one should come up on a vacuum test if you're running manifold vac, but not if running venturi ported. Hope this helps. I find frequent coffee breaks and stuff like that helpful when diagnosing things... -bill
just had the same scenario happen with my buick. my gas tank had rust & debris in it. it was just enough **** in it to clog my line so my car would idle but as soon as i tried to go it would die out. maybe check your tank? _T
Thanks you guys for all the great suggestions! This is where I stand as of right now. SInce I posted this I tried to get as much gas out of the tank as I could before I filled up the tank with new gas. The fuel filter is always full of gas and was cleaned. I replaced dist. cap and rotor. The points are kinda bad but I haven't change them yet. No change in performance. I rebuilt the carb and while doing that I found about a 1/32 to 1/16th of an inch of this off white powder in the float bowls. After cleaning an putting the carb back together the car ran great... for 25 miles I drove last night. Freeway side streets no problems. This morning it all started again same distance from my house it started to sputter and stall. Then after revving the **** out of it, it started to idle again and five miles later it got me on the freeway where at some point I noticed that it was backfiring again when I let off the gas. After letting it sit all day while we were doing body work on it, I started it up and it was doing pretty good for a while, and then the same ol story. I barely got it home tonight, but once there I let it sit running for a while and then it would idle again. I took it out and it ****ped out again lol. ok so when I got it home this last time, I noticed that now when I pull the battery cable off the motor dies right away; this didn't happen before. ( I have a short so i take my cable off whenever i stop the car) So besides the new information, I'm wondering if the resister/resister wire can be the cause of both problems? (note that my battery doesn't seem to be running down)
i had the same problem on my 57 chev pickup. i swapped a bronco II gas tank in and i have no bottom in my box. there is a breather on top of the tank and it would let moisture in. it only did this in the mornings and when it rains. since then i've sealed the top of the tank and put a tarp over it.
Yeah I did replace it. Just out of curieosity, that is what would spray gas in the carb when when I push the linkage right? And why would it work great the first day after the rebuild?
Hmmm - lots of info, and yet - not so much to go on (i.e. detils about the truck). Lots of leads, lots of things to check. Pardon me if I get long winded. I'll go a little deeper than most guys need, because you're not the only one, just the only one who asked (or at least the only one who asked recently and didn't go from 0 to page 60 in 4.5 seonds). This is tech week, after all. Muffler baffles have been known to come loose and cause restricted exhaust, and this symptom. Unhook at the collectors to test. Obviously, look for crushed pipes. Restricted exhaust that looks good means time for a new muffler. Bakelite (or something like that) gears, gear-to-gear. They generally either work or not. Cam timing problems don't often come and go. Do you do drywall, or park near a construction site? Do you do bodywork on or near the truck? You cleaned the carb out - check to see if the contamination's back. White powder in the carb again = contaminated fuel system. Bondo/ primer dust, drywall dust, concrete dust, maybe grinder dust - all suspects. Something is in your tank, and fine enough to get past the filters, and clog up the carb. Cleaning the carb worked for a while, now the problem's back. If you see more white powder in the carb, clean it some more. Then REPLACE (not clean) all of the the fuel filter(s). Check the carb inlet fitting (prolly not if the carb is as old as the truck), all along the fuel lines (some previous owner may have thought an extra one or 2 would be better), inside the fuel pump (if the inlet fitting unscrews, there is probably a filter behind it) and inside the tank (pickup screen?) for additional filters. Replace them all. Then pull the tank and flush it. Now flush it again. Now take it to the radiator shop to be boiled out. If you didn't have a pickup screen before, add one (89-92 Chevy Truck TBI inlet sock works good on most 3/8 lines, under $20 at the dealer, and can save lots of h***les). While we're on the fuel system, pull the dipstick and sniff. If you smell gas, the fuel pump diaphragm is leaking fuel into the oilpan. Replace the pump that is about to go out. The first sign of a weak pump (besides the vehicle starving for gas) is a bad diaphragm will often leak gas into the oilpan. If the pump is bad, change the oil too (even if the oil doesn't smell like gas). Gasoline eats engine bearings fast. Maintenance first. Change them. Change or check the plugs and wires, too. Testing wires: Ohm them. There is a spec for resistance per foot, should be in your shop manual. If not, google it - I'm lazy, and just warranty my wires if they are suspect. Test for leaks. A plug wire leak tester is big $$ off the tool truck. The Harbor Freight ones ... you get what you pay for. The secret: Aside from the tip design, and the automotive testers having adjustable sensitivity, they are the same thing as an inductive 110V AC circuit tester (the kind you stick in one prong-hole of a wall outlet to see if it's live). They are generally $10-$15 at your local big box home store. Shove an old insulated plug wire boot over the end to make it directional and cut back on the sensitivity. Practice on a known good car to get a feel for the sensitivity and what to expect. If it lights up and goes nuts to where you can't see where the leakage is, it's either a whole set of REALLY old wires, or the coil. Check out the coil. Old coils can get a partial short through the case. If it shocks you, it's bad. They are supposed to be oil filled. Unbolt it and heft it. If you've picked up very many, and this one feels light, it's bad. Should be test procedures for your ohm meter in the service manual. Most traditional points type coils should have low resistance (not 100k ohms) across the two wire connections (primary wires - + and -), and no continuity from the wire connections to the coil wire (secondary wire) terminal. Check voltage at the coil. Should be +12V cranking and +8V or so running. If not, you have a power supply problem. If the coil is weak, using a jumper wire to supply a full 12V+ all the time will often make it work better for a little while. 12V all the time will burn out a coil quick (unless it's late model stuff or aftermarket marked as 12V constant duty). It will also wipe out points quick. Temporary testing only. FYI, hitting the coil with +12V is an old racer's trick for getting high compression engines to run with stock ignition. Makes a hotter spark, until it burns up the coil and/ or points. Hmmm. You have a charging system problem. May or may not be related. Hard to diagnose without knowing what kind of charging system you have. I'll ***ume it's 12V negative ground. Could be the proper alt/ gen energizing circuit is dead or weak, and it only charges because it self energizes with help from backfeed though the charging wire to the alternator. Could definitely be related. May also be related to the short that makes you disconnect the battery. Alternately, it could be a bad engine block ground. Most charging systems ground the alternator/ generator throuh the bracket through the engine ground. Do a voltage drop test - hook one volt meter lead to the engine block and the other to the battery NEGATIVE. Should be less than .1 volt. If not, you have a bad ground. Check from engine block to dizzy case, coil housing, alt/ gen housing, and dash frame. Bad grounds can cause all sorts of issues. Last, but not least, check the charging system dummy light or meter for proper functionality. That can also cause not charging and/ or ignition problems. On a vintage car with little or no modern electrical upgrades, a dead charging system can leave the car drivable for days or more. Especially if you never drive at night or in the rain. There are a ton of other things it could be - burnt valves, bad carb, ******, no lube in the diff... Sometimes drivability diagnosis is like a scavenger hunt. You may find 10 things 'wrong' before you find the one that is currently bad enough to cause the symptoms. Errmmm - you did check the air filter, right? Not being a smarta$$, just trying to be thorough.
When you yank the battery cable it should keep running IF the alternator is charging and there are no shorts. Put a volts guage on the battery, it should be almost 14 volts. If its not ,,you either have a weak battery that won't hold a charge or the alternator isn't putting out the voltage needed. You said it died when you pulled the battery cable right? I'd say you have a charging system problem. I'd change points , condensor and gas filter while yur in the hunt too .
The backfiring when you let off is a symptom of unburned fuel in the exhaust. Which is why it does it when the car runs bad. This can be from poor spark, which can be related to a failing alternator or battery, both of which can intermittently short out and do what you describe. Do you have a volt gauge that would offer any evidence of this? It's also evidence that something could be wrong in your distributor. Working great after the carb rebuild could be total mojo alignment and pure coincidence, or maybe you bumped a wire. Good Luck.
My guesses are: A crusty gas tank (bumps in the road will knock rust and junk loose) A vacuum leak (spray starting fluid on the intake with it running and listen for RPM changes) A dirty/restricted/collapsing air cleaner. Well, those were my problems, so I thought they might help. Thanks, Kurt
Sounds a lot like an intermittent fuel starvation. Do you run one of those little chrome and gl*** fuel filters? The nylon mesh inside can become blocked with debris so fine that you can't see it. Try blowing through to check. The other thing is that there are tiny internal filters in many carbs - these can become blocked so check them too. What can happen with all this is that debris is held in suspension and then when you go on a run it starts to aggregate, fuel flow is restricted and you loose power. After you've stopped a while the debris goes back into suspension and you can't find any blockage. Check also the vent on the petrol tank. If this was blocked then you would get fuel flow problems. Also check the rubbber hose - is it collapsing or (and this is a wierd one) where it pushes on to hard line you can get a little shaving of rubber that acts like a flap valve and can block the flow of fuel.
BTW - the off white powder is due to water in the fuel. This is a pain in the **** because fuel sits on the water in the carb and in the tank. As most tanks pick up from near the bottom and engines run on petrol not water this is a problem. We get this over here with supermarket fuel - I've drained my trike tank and found half a gallon of water in it. Wynn's do a petrol dryer that also the petrol and the water to mix.
It's been a long time since I worked on a Chevy straight 6 but... one of the problems that I ran into more than once with the same symptoms as yours was the "bearings" starting to go in the distributor. Check the shaft for any sign of a problem - the shaft will wobble and cause the point gap to change under certain, odd, and intermittent times.
This is a new one on me - but it makes sense. Easy to test, too; I'll try to remember it. After reading thru the thread again to see what the problem turned out to be (and it looks like it wasn't solved yet), I'd guess this car may have 2 sets of problems: the electrical problem (dies when battery disconnected; short in wiring somewhere), and the poor running under load. They may or may not be related. Perhaps it'd be a good idea to chase the electrical problem. The short can start a fire (having lost a car to this, I'm rather sensitive on the subject), and should be fixed for both safety and not-having-a-piece-of-****-for-a-car's sake. Since it's something running down the battery while the car sits, should be straightforward: turn the car off, take off one battery cable, stick a DMM set on 10A scale between the disconnected cable. Read the amperage. Start pulling fuses until the amperage drops way off. That's your circuit. Look for damaged/bare/rubbing wires, bad connections, etc. Now, see if the car still stalls when you pull a battery cable. Like Caddaddy said, it shouldn't. If it does, follow what he put on his post and you should knock that problem out. If you still have a problem with power under load, I'd look for fuel delivery/carburetion problems (okay, I'd check the distributor for wobble first ). I guess tech week is over, but I went ahead and posted how to make and use a propane tester here. Other guys have other methods, I suppose, but this one's always worked for me. Cheap and easy. Zombilly, be sure to post what the fix turns out to be; I'm always curious if I even ended up in the ballpark! Hope all this helps...
Well still no luck on the car, kinda. The battery issue has disappeared but the engine is still there. I have replaced plugs, wires, points, coil, rebuilt the carb, found that the upper sprayer from the accelerator pump was blocked and fixed that. Checked the dwell and I'm ok there. It work well after the rebuild, after the points changed, after the accelerator pump problem. But it only works for a day or so at this point. Up until tonight the car ran great, no flat spots, the best its ever ran. Now it won't idil yet everything that I changed is still working. Any other ideas?
First rule of a tune up is check for air leaks under the carb,,i.e base gasket and manifold gaskets. Run the engine and squirt a little gas around the gaskets .be careful not to get it on the exhaust, alternator or dissy...sparks and gas = fire. If there is a leak, the engine will speed up when you spray gas on the leak. Next once the engine is hot ...compression check. If no air leaks and compressions are good. I suspect 1/ You have run the tank low right at the beginning of this problem and have **** in the fuel system...pump, lines ,filter etc which keeps coming back into the carb after a bit of driving.This stops the needle and seat from closing and makes the car run rich. Second choice would be a bad condensor...do the points keep burning after a few miles? Remember order of tune up Air leaks, Compression test. air and fuel filters Ignition Carb last.
You mentioned doing bodywork on the car,is this when this started? Is something plugging tank vent or air filter? If there is moisture in the fuel try a bottle of methalhydrate with a tank of fuel.Those of us from wet,cold areas have much more of these problems than so Cal rodders.
Isn't there something less flammable to use? I've used starting fluid. It must be flammable, but as much as gasoline? Couldn't you use something non-flammable, and it'll displace the air/fuel mixture if there's a leak? Thanks, Kurt
Have you checked the vacuum advance on the dizzy? It should have both mechanical and vacuum advance. Both need to work properly for the engine to run under all conditions. The advance mechanism can become stiff when the grease hardens. Do you have a screw in grease cup in the side of the dizzy? If this happens you will not get the proper advance in timing. Check to see that both are working and that the points plate moves freely. This can cause an problem that can come and go depending on conditions. Make sure that the vacuum system is working properly. Many of the cars and trucks that had the 235 engines also had vacuum wipers. Make sure there are no leaks in that system as it can affect the engine timing. Joe
I use brake parts cleaner. Less mess, less dangerous. Still flamable (more flamable than gas), but evaporates quick (usually in seconds if you don't make a big puddle) and doesn't burn very hot. It's also not as strong as far as eating paint goes, compared to gas, starting fluid, carb cleaner, etc.
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