The Stovebolt Site Forums The Shop Area Engine Shop HELP!!! First time Posting! Backfire, engine died

Hello all,

This is my first time posting but I have been using this site constantly since I purchased my 53 3/4 ton Chevy truck in August (a 235, 3 on tree) and have been trying to get it to run properly since I got it to stop now. I am a 25 year old in North Carolina (Go Heels) and this is my first time doing major mechanical work.


I have been working on getting my 235 to run dependably, but have been running into some issues. I have changed the head gasket, intake/exhaust gaskets, oil, new plugs, wires, coil. I have everything back together and she will idle great and run good. Last night when I was messing with it (drove it around the front driveway, mostly in first gear, so I wasnt going fast since the drive is bumpy, then I returned it to garage and kept it running) then there was a loud backfire through the tailpipe and shortly thereafter the engine died when I had it running at a higher idle after i had returned it to the garage. It had been running fine the previous times I had cranked it and let it run in the garage at a normal idle and a higher idle. This is similar to the problem I had before I changed the above mentioned parts. Sometimes i could drive around the neighborhood for two hours and it would run great then the next time I would drive it for two minutes or twenty minutes and I would hear a pinging noise (usually when foot was off the gas and I was decelerating) and it would stall and would not crank back up untill after it sat for a while or I could get it started on full choke. It does not appear that the engine is getting too hot but I do think I need to flush out the radiator. My windshield wipers will also come on and move to one side but I have to turn them off, then back on, for them to go back to the starting position and it alomst chokes the engine out when they are on. I know this isnt right but when they are off the engine seems fine so I dont think its leaking then when they are off (but could be, would love input here as well). I am beginning to think that it may be timing related but I do not know anything about timing other than the things I have read on here or that there still is vaccum leak somewhere where I havent checked that starts when engine up to temp. Could this be timing? Or would it not even be able to run for a while if timing was off? I have also taken apart carb some and it looked very clean so I put it back together.

It baffles me how the engine will idle great and run fine for a while then all of the sudden die. Could that be timing or distibutor? Also, it is still 6 volt system but has an 8 volt battery in it right now but regulator hasnt been adjusted so I charge the battery when needed.

Any direction/discussion would be very much appreciated and I have absolutely loved this website even though this is my first time posting and have really enjoyed working on this truck but ready to get back to driving it and not pushing it home! I will gladly answer any more questions that you have to help me head in the right direction, because I am in need of some assistance.

-Jim

You can reliably get the engine to backfire if you are running down the road, cut off the ignition, and cut it back on.

So it is possible that you have a loose connection at the distributor or coil that is causing an intermittent spark. Your coil could also be going bad.

I don't know why you are running an 8V battery, it should not be necessary if your connections are good n tite.

Other things to look at would be your vacuum advance at the distributor. Does it move when you rev the engine? If the diaphram is busted in the advance, you will have a vacuum leak, and of course it won't run right either. You also might want to check out the centrifical advance in the distributor, and the health of the distributor in general.

Hope you are not running the truck in a closed garage.

I too am from NC and "GO State"
NCSU grad, 1977

Kurt

What Kurt said!

Check out the timing.


Check out the heat riser valve on the manifold. A valve stuck on "heat" can cause problems like this.

Even a liberal arts graduate of UNC 08 knows dangers of a car in garage, but the garage doesnt even have doors on it at all and tailpipe sits outside. haha

Only reason I have 8 volt battery is the old man at Napa sugguested it over 6 volt, but it had no problem starting with the old worn out 6 volt I did have in it. After reading this site wish I would have never bought 8 volt but for now Im going to use it until I can get this problem solved first, then I'll purchase correct 6 volt.

I do not fully understand the "vacuum advance" and I do not really know how to tell if distributor is good or bad and I do have a new coil (no difference in new and old). Should you be able to turn distributor body (part right below cap) when the engine is off? Or should the distrubutor body be fixed?

I do hear a pretty loud suction noise right when I hit the gas that seems to come from the Distributor area/vaccum advance area, so I will check this out and also the wiring. If someone could explain vaccumm advance (like its function and how to fix it) to me or point me in right direction I would be much appreciative.

Thanks Kurt, and glad to hear from a fellow NC native even though your a Wolfpacker.

yes the distributor should move, that's what the vacuum advance can does to adjust the ignition timing depending on vacuum .... sounds as if you may have a defective one, replacing it doesn't cost much or take long, should be able to get one from NAPA

Bill

Jim,

If you grab the top of the distributor, you should be able to rotate it maybe 10 or 15 degrees. It will spring back to position. If you look on the right hand side of the distributor at the block, you will see a silver (depending upon how clean your engine is) looking thingy with an arm that connects to the distributor. You will see this arm move when you rotate the distributor. If you start the engine and reach over and goose the throttle at the carb, you will see the distributor instantly jump. Thats your vacuum advance working. If you hold the throttle open you will see the distributor rotate and steady out. That's your centrifiugal advance.

The whole idea here is that the engine needs to have the spark happen at different times depending upon if you are accelerating or at what RPM the engine is turning. "Advancing" the spark means it is happening sooner relative to TDC.

I'm certainly not an expert on this, and others can give you a more detailed explanation, but that's the basic idea.

If you are in doubt about the vacuum advance, you can remove it, and suck on a tube attached to the vacuum port. If you have no resistance, it is shot. If you can create enough of a vacuum, it will move.

Hey,

Hope you will consider coming to the upcoming Southern Bolter Gathering. Might even be some Duke fans there. (my wife)

Kurt

I am pretty sure the vacuum advance is bad and just ordered the correct one, since Napa didnt seem to have exact one I have. I goosed the throttle and did not see any movement of the distributor and also confirmed that the loud suction noise was coming from this area. But did push the distributor by hand and it would spring back. To get the vacuum advance out I had to remove the distributor and I am not sure the proper steps to properly re-install distributor to get the engine to run properly.

Kurt would be interested in attending the Southern Bolter Gathering and would love to hear details of the event.

Thanks again

Jim

Jim,

Its been a while since I have done this, but it's pretty simple. The end of the distributor is only going to fit in two ways, so you immediately have a 50% chance of being right. Put number one cylinder at TDC by lining up the ball on the flywheel with the needle, and then see if the rotor is pointing to the number one wire on the distributor cap. If it's 180 out, pull the distributor rotate the shaft 180 and put it back in. Then time the engine.

Achipmonk has been arranging the Southern Bolter get together.

See this thread:

Kurt

The only thing I can add to Kurt's post is to remember that the number one wire on the distributor cap needs to be perpendicular to the engine block, or that the tabs that hold the cap on need to be parallel to the block.

it doesn't actually matter which one you use for #1 you just have to have the rotor line up with one of the terminals inside the cap and the rest just go in order,(you would of course have to move the wires to the correct relative position) the important part is getting the little tang on the bottom of the distributor lined up with the slot in the oil pump.If you haven't turned the engine at all with the distributor out you should be able to just put it back in, but if you move the engine with the distributor out, the oil pump gets out of sync. It will be much more entertaining. You can put the distributor in as many ways as there is teeth on the gear but unless it lines up with the oil pump it won't go in all the way. Every other tooth it seems like could be fine as long as the rotor lines up with one of the terminals. The reason I mention getting the oil pump lined up properly is there was a post fairly recently the fella didn't have the distributor down far enough to engage the oil pump. But down far enough to engage the gears, it would run but had no oil pressure.

Brokenhead,

That fella was ME! You saved me the trouble of outing myself. ;-)

Jim, everyone's got you headed in the right direction. If you HAVE turned the engine over with the distributor out, then you'll need to find Top Dead Center, which sounds more intimidating than it is. Let us know when you get to that point, and we'll get you going.

Otherwise, as stated, you've got a 50-50 chance. If you remember which direction the rotor was pointing when you removed it, replace it facing the same direction, and you oughta be ok. FWIW, the shaft usually turns a tiny bit as it engages the camshaft gear, so start a little off of where you plan on ending up. (can't remember which way, I think start counter-clockwise a few degrees). And yeah, be sure it's all the way down! If it's got oil pressure when it starts, you got it right!

One other thing - you'll hear of several different methods of checking for vacuum leaks. Most common is spraying WD-40 or some such around potential leak areas. Personally, I like an open but not lit propane torch bottle - it's a little cleaner. Obviously, be careful, but holding the tip around leaking areas will reveal by an increase in rpms. Of course, this pre-supposes the engine is running to begin with . . .

Report back on your progress. Sounds like you're on the right track.

-Michael

thats funny

Thanks for all the help guys,

I have got the engine back runing and went for a quick 10 minute drive. At first, I put the distributor back in place ( i had not rotated engine) and tried to crank for a second. I could tell my oil pump wasnt engaging, so I took it back off and somehow it fell right into place then and cranked up thankfully.

Engine ran good but not perfect and I definitely noticed a little drop in power. And I am sure this is due to it not being timed perfectly. I still havent been able to find the timing hole (of course lot of dirt in the area) and I have never "timed" engine before. I know its pretty close for it to run as good as it did and didnt know if I could just adjust distributor a little bit with engine warm at idle until it is running better, if i make a mark of where I am right now on distributor.

Any thoughts or advice is extremely welcomed.

No reason not to adjust it in place. You'll be happiest if you go the timing light route, but yes, you can turn it a little as it idles, after loosening the hold-down bolt, and you will hear the engine change. Move it one way or the other, see how it sounds, and use your hand to push the throttle linkage and rev the engine. When you find a spot where it seems happy, both idling and reving, tighen it down and go for a drive.

If it seems better, great! If not, you can keep tinkering until you're happy.

Common wisdom is for the timing to be advanced to the point where you get a light "pinging" on hard acceleration. Pinging is hard to define - I'll let others jump in. But when you find it, some people leave it there, others back it off just a smidge. Then you're at optimum timing.

Good luck! Sounds like you're making great progress.

-Michael