Spark plug question

[nimak5]

So my truck had been running fine, but I was bored and decided to replace my spark plugs. I went with what the autoparts store recommended (r44t) since I didn't research on here in advance and gapped the plugs at .035. Now my truck is misfiring... (and actually backfired once).

Should I switch to the r45ts? or gap the same plugs to .045? I threw away the old plugs before checking which they were, but they were all gapped right at .035.

 

[ryoken]

sounds like a bad plug, not a gap issue.. maybe a cracked insulator out of the box, pull em and see which one is burning different.. plug gaps aren't a crazy critical thing one way or the other usually... but most carbed sb's are 35.. EFI's tend to run wider gaps due to better ignitions, etc...

 

[nimak5]

Well I pulled all the plugs and came to realize they gave me the wrong plugs.... R44LTSM6's... Another PepBoys success story... Rookie mistake by me not to double check. Not to mention I must have been in a rush because I pulled out two plugs with the tips jammed down onto the electrode. Or the threads were longer so must have hit something while tightening. Thankfully I went ahead and picked up some R45TS's just to be safe. Swapped everything out, but its too late in the evening to crank the truck as it is parked right next to my neighbor's bedroom. Will post an update in the morning when I crank it. Thanks again for your help ryoken.

 

[nimak5]

So I cranked it and it ran very well while it warmed up. Came across another problem now.... I drove it out of the drive way and it just shut off at the front of my neighborhood and wouldn't start back up. Any thoughts on why this would happen? I did notice I forgot to plug this small wire back up (pic below) which I think is connected to the oil pressure sensor, but would this shut the engine off? I plugged it back up and I got it started again after several cranks, but I'm afraid to get it on the road without knowing what the cause was. Thank fully the front of my neighborhood was the top of a slight incline and I put it in neutral to roll the truck back to my house. I also checked the distributor power line and it seems to be fine.

I'm a total noob when it comes to engine work. I've got the suspension part down, just trying to get a grasp of the engine stuff with this 350 before I swap the engine. But hopefully this will teach somebody else in the future too.

 

[ryoken]

that's just the water temp sender wire...

fuel, air and spark... start with that...

 

[nimak5]

After digging around the forums, the new symptom leads me to believe I may need to replace the ignition module. I'll get that tested tomorrow and hopefully get the truck running good again.

 

[ryoken]

if you replace it, make sure to get an AC Delco.. aftermarkets have been known to be chit...

 

[nimak5]

Are these any good?

http://www.summitracing.com/parts/sum-850030/overview/year/1974/make/chevrolet/model/blazer

I'll be swapping the motor in the next 12 months, so not trying to spend too much on this one.

 

[nimak5]

Took your advice and went with the AC Delco

 

[ryoken]

and for the record.. I wont run anything other than AC Delco for plugs in a cheby either.. NGK ain't bad, but I run AC's whenever possible...

some will try to say AC stuff has gone done hill because it's made in mexico, etc.. but I install hundreds of AC Delco plugs in boats annually, and have yet to have an issue with quality..

certain components, your better off... need a turn signal actuator for your GM column? make sure to ask for the Delco one too...

 

[80' 427]

Wires are awful close to the headers you should correct that.

 

[nimak5]

So I put the AC Delco ignition module on and the engine won't start. I noticed that the AC Delco ignition modules are for 1975+ models and mine is a 1974, but has an HEI. Could this be the problem since mine is a 1974?

 

[ryoken]

shouldn't....

what troubleshooting did you do to determine it was that?

I take it you checked for spark at the plugs? power to coil?

 

[nimak5]

No spark at the plugs and power to coil is connected.

 

[ryoken]

connected, or verified with a meter/light?

 

[nimak5]

Well I finally figured it out and the truck is up and running strong. Drove it around all day today to make up for the lost time.

Problem #1: SOMEHOW, I managed to not connect the module correctly. I guess I rushed when I got the new module and when I connected it, it didn't quite go into the female end. Rather went above it and rested on it.

Problem #2: Found out the power wire that goes thru the fire wall was starting to ground out randomly. Had power to the distributor most times, but noticed sometimes I didn't. Luckily caught this because it would have driven me crazy if the truck shut off again in the middle of the road and probably would have taken it to the shop because of frustration.

The power wire fray seems to be the apparent cause of my original stall. I must have bumped it while pulling the plug wires and caused it to hit it's worn spot and ground out, thus killing the spark. I put electric wire around the worn area until I replace the entire wire from distributor to the fuse.

FINALLY up and running though. Thanks for your help ryoken. Really appreciate it. Next step is swapping the gas tank, sending unit, and fuel pump, which I bet I'll manage to make some mistakes on too...

 

[82355]

The fuel pump is not in the tank on a 1974.

Martin