Was driving the girl yesterday and she backfired once then drove fine 10 miles later she just quit. checked all the wires jiggled them and started up drove about a mile quit again started back up and drove fine all the way home about 20 miles. gonna repace all wires plugs cap rotor and coil. wondering if any of you can give me some insight as to what else to look at. Thanks
Billy Epthimiatos
G'day Billy,
My advice would be, don't just replace everything you've suggested straight away.
Try to go through each item on its own and try to decipher and diagnose the problem if you can.
Its an old drag racers tip, one change at a time.
If you change everything and fix it, you won't know what the hell was wrong in the first place.
If you change everything and make it worse, you won't know what the hell was wrong in the first place.
I'd be looking for something loose.
Right, some good old diagnostic work might bring up the problem without using the "shotgun" approach and save you some money. Don't forget to check the condenser while you are looking for the problem and also look for a broken wire making intermittent contact.
74 could be points? Or the new electronic ignition?
As already mentioned, I would check for lose connections at coil. Check for clean internal ground strap on ignition coil (electronic) . If the tune up items are questionable and old...I would simply replace it all post haste.
Ooops, oh yeah, HEI. No condenser to check.
Quote from: ithaca1230
Was driving the girl yesterday and she backfired once then drove fine 10 miles later she just quit. checked all the wires jiggled them and started up drove about a mile quit again started back up and drove fine all the way home about 20 miles. gonna repace all wires plugs cap rotor and coil. wondering if any of you can give me some insight as to what else to look at. Thanks Billy Epthimiatos
It does sound like ignition. But make sure the timing chain is OK; it should
have been replaced by now. Bruce Roe
In addition to the suggestions made, consider whether your fuel pump is working properly--when was it last replaced? Just another consideration.
Back fire is a symptom of lean fuel. One possibility is restricted fuel flow. It is OK when idling but when driving the fuel in the carb is diminished until the engine dies. Restarting refills the carb.
1974 Cadillac the HEI was optional, points standard. My friends 1974 Cadillac did the exact same thing, and it turned out to be the coil had to be replaced in the optional HEI. There are also two wires that are inside the ignition that can break and cause this problem too. The problem is likely confined to ignition, not fuel or unlikely been a backfire.
That same type of problem has happened to my 76 deville. The wire connection from the HEI kept slipping out as I drove a few miles when again I had to stop and push it in. I was on the highway and didn't have any tape to hold it attached so I had to keep stopping and push it together for another few miles until I got home and repaired the attachment. Just make sure all the electrical connections are securely attached first of all. EAM
Thanks for the response! I changed the coil coil wire cap rotor and little round thing on top of coil. I was told I need a dwell meter to set points so I didnt do that yet and ran out of daylight last night so didnt change plugs, wires or fuel filter. It ran fine after that with no backfire. I have not changed timing chain yet or the fuel pump. They are on the to do list. Was hoping to do one thing at a time and still drive it around. Will let you guys know if it happens again.
Thanks again
Billy Epthimiatos
It sounds like your 74 fleetwood is an early production as electronic became standard fare soon after.
Point ignition get 'pits' on them...and likely the problem. I would abandon that system and swap out the whole distributor to the electronic version. You 'might' need the air pump tube that encompasses the larger assembly?
It's a world of difference in performance, reliability, economy and starting.
I will have to look into this thanks!!
Billy Epthimiatos
Billy,
Changing the "little round thing on top of the coil" will net you zero results with your problem. All that is is a capacitor to help reduce radio static. If it is bad all you will notice is more static on your radio, especially on the AM dial. What you should be concerned with is "the little round thing" (the condenser) inside the distributor next to the points. When this component fails it can cause some different ignition symptoms, one of which could be similar to what you are experiencing. Sometimes the failure will cause the engine hardly to run at all, other times it will let the engine run fine at lower RPMs but will cause misfiring and backfiring when higher RPMs are attempted, etc., etc.
GMs HEI ignition is great, but a much easier and probably less expensive route would be to convert to a Pertronix II system with their coil. http://www.pertronix.com/ I haven't taken notice lately but there has been a vendor in the Self-Starter advertising Pertronix systems at a discount for CLC members for quite some time. I have done several of these conversions and they have always been trouble free for me.
I have used pertronix...and its 'ok' but no comparison to the OEM electronic system introduced as standard fare in 1974.
It's fairly easy to 'swap' systems. The whole distributor is replaced, wires and plugs. A heavy gauge wire is required to supply the power.
Even a novice should accomplish in an afternoon. An expert in 1.5 hours.
Most important to research exchanging distributor and maintaining the timing....that will cause you the most grief.
Thanks for the recommendations. I am going to look into this stuff. A buddy gear head was saying something similar. For now just gonna change all the existing stuff. Next big repair is the timing chain and fuel pump. Oh and get the radio to work on more than one speaker so kids will ride with me.
Thanks
Billy Epthimiatos
Well figure out the problem. As I drove the car to my buddies house to finish the tune up she backfired so hard it blew the muffler open at the seam. Scare the crap out of me. Started pulling wires and plugs and there was a couple real bad ones. I cant believe I didnt start with that when I first got the car but it was running fine. Having a new muffler put on her now. If I figure out how to get pics on here I will show you the muffler it is impressive.
In my earlier post I assumed the backfire was through the carb. Obviously, I was wrong.
What you have is unburned fuel getting into the exhaust. My father had a Buick that exploded the muffler in the same way several times. Usually when starting the engine. He finally figured out what was wrong. It was a burned valve. We never figured out the mechanism as to how that worked, but the older parts guy at the NAPA store told him it was common.
It's possible you also have a sticking valve which would be similar to the burnt valve mentioned above.
Everyone has there own idea on freeing them up but some good old fashioned Marvel's in the oil mite help....... Can't hurt.
Jeff
The carburetor could be 'overflowing' causing raw fuel to accumulate in the exhaust system. Are your spark plugs or tail pipe coated in heavy black soot?
FYI Did the fuel go fuel 'stale'? .a very common occurrence after 4 months with alcohol blended fuel. Very first thing I check on any old car...is I remove the fuel cap and sniff for stale fuel. People do not realize stale varnish gas it is like having sugar in the gas. It WILL stick your engine valves open or cause them delayed action. Dilution is not the answer...REMOVE it! Needless to say it also causes havoc in the carburetor and everywhere else. Typical of a stuck valve, in this varnish gas scenario , is the car will still run when it's warm...and your compression test would be ok. Once the engine cools the valve guide seizing is in place. The next morning the engine has a dead miss (minimumly) or won't start at all.
Drove her around a bit this weekend and she runs fine now. The only thing to change is the points. Going to drop it off with a mechanic that is up to speed on these cars and appreciates them and have him change the points adjust timing and the idle if needed. Thanks for all the help gives me stuff to look at.
Quote from: ithaca1230 on June 12, 2017, 09:12:47 AM
Going to drop it off with a mechanic that is up to speed on these cars and appreciates them and have him change the points adjust timing and the idle if needed.
Welcome to the world of old cars. Something that is VERY DIFFERENT between old and new cars is that old cars CAN be fixed by yourself in your own driveway. Once you learn how . . . .
2017 Benz or Tesla? Drop it off and get it fixed.
1974 Cad with a points type ignition? Dont just drop it off. Instead hang around and try to get the mechanic to show you how the ignition works. Watch him swap and adjust the points. It is so simple and basic that it will surprise you.
Back in the old days everyone knew how to repair and troubleshoot their cars, you went to a mechanic only if you did not have the time to fix it yourself.
LEARN, learn, learn about how your car works!! Mechanics are great but I think the #1 reason (younger?) people want to modify their car to 'maintenance free' components is because they dont want to be embarrassed to admit that they dont know the basics.
Any club members in your area? I would love to teach an interested (entry level) person how their old car works!
The more you learn, the more confident you become, and the more attached you will be to your car.
Thanks m-mman. I am not familiar with these points. I was told you would need a dwell meter to set them correctly. I also think she is idling a little high. I was gonna hang around and have him show me how to set the points. I figured he can set them check the timing and the carb and get her set. I love to play with the old cars but not very experienced. I dont want to do something and then have to ask someone else to fix my mistake. I am located in Ithaca NY. I will let you know how it turns out. Thanks!!
Billy Epthimiatos
So you need about $20 of new tools.
The downside, of course, is you only end up with $20 of new tools . . .
One of these https://www.harborfreight.com/fuel-pump-and-vacuum-tester-62637.html (https://www.harborfreight.com/fuel-pump-and-vacuum-tester-62637.html) for $15 and one of these and a tachometer/dwell-meter, and you're good to go.
OK, $15 for the first, and more like $40 for the second.