So I’ve had this old beauty for a month now, odometer says I’ve already put 300 miles on it and this morning as usual I go out for a drive.


Now, she started like usual, a few pumps of gas and then started right up, let sit idle to warm for 5 minutes and then drove off. But only about 5 minutes on the interstate I hear a thud-like sound, like a single deep tone pop, maybe a backfire, maybe a rock hitting my undercarriage, and the engine begins losing power. I try to give some throttle and she won’t pick back up. Luckily I can get to the side of the road and stop safely where I try to trouble shoot my engine.
The starter turns strong and with enough gas the engine makes the rumble of a start for that first .25-.5 seconds but won’t actually run.
Needless to say, I now have a problem I was not prepared to tackle just yet.

Online I’ve seen that it could be a fuel line clog, someone else said the got a backfire and the engine died too, replacing the carb fixed it. I’ve seen MAF sensors being dirty, vacuum leaks, etc.

My first thought goes to the work I did yesterday, removing the speedometer to replace the bulbs, and maybe a sensor in there told the engine to quit?

I also started sealing off many hoses for the headlight vacuum system since I replaced it with an electric motor and wanted to clean up extra lines. I did thorough research and followed every line by hand from their source to their destination and removed only the ones relating to the headlights.

But I also think back and remember that I’ve been running with high oil pressure that drops down to normal PSI after a few miles of driving.

Anyway, they say two heads are better than one, so a whole forum has got to lead me to a solution, right?


This was during the eclipse. Had to give the baby a photo shoot, because of course, right?

 

Have you tested fuel pressure?
Have you tested spark?

 

Your profile says this is a 78, correct?
Manual/auto?
Tell us about the engine.
Original carb setup or converted to FI?
Stock engine?
Headers?
Cat still in place?
HEI Distributor with original components?
A couple of pictures under the hood wouldn’t hurt.

 

Module in the Distributor.

 

I’ve only had a small block Chevy straight up die on me twice.
first was the HEI module failed without warning. Testable by checking for spark.

the second time was, long story short, ground caused fusable link to blow, interrupting power to distributor. Again no spark.

if you can verify the three necessary parts for combustion, spark fuel and compression, you should be able to narrow it down rather quickly.

 

I am thinking the same as Randallsteel and Blue1972, but then I read where he talked about MAF sensors and possibly sensors in the dash.
That is why I am asking now about maybe a conversion to fuel injection or some other modification.
Was not aware straight carb/mechanical fuel pump systems had MAF and Speed sensors?

 

It's 100% the MAF. At least, according to a Google search of the symptoms.

 

why would that car even have a MAF?
it's a 1978 with a carburetor.

 

Did I forget to add the sarcasm tag again?



OP: Thanks for the photos (including the eclipse photo!). Please post some photos of your engine from all sides with the air cleaner removed. Sometimes, the problem is pretty obvious. If you have a MAF, that will be obvious, too.

 

I've had small block Chevy engines die for numerous reasons. Once I threw a rod right through the block! That actually kept running long enough to make it to the freeway off ramp.
once, a fuel pump, once a ignition coil.
Lots of different things over the years in different Chevys. Never, not once a ignition module. Even if it is the most popular answer on here.
Bottom line. You need to do some basic testing first before anyone can help.
Way to many possibilities.
Is it getting fuel?
Is the fuel making its way through the Carburetor?
Does it have spark? Is it getting it at the right time?