86 305 won't start. Ideas?

[MWS1994]

Hope I put this in the right forum.

*UPDATE*
*So I got the car running now (not really sure what I did), though now the carb is backfiring pretty bad and it seems sluggish. Any ideas?*


I recently got an 86 Pontiac Grand Prix, 305 v8 auto (Qjet carb). It ran fine when I got it, but had no muffler (or cat). I got a muffler on and when I tried to start it it ran really rough, sputtered, and then died. It took a little while to get it going again but it finally did and sounded ok.

About a week later I tried to start it and it ran really rough. A couple days later it wouldn't even start, just crank and crank. Timing is good as far as I can tell, (at TDC, distributor rotor is at #1), put new plugs in, it's getting fuel (won't even start with starting fluid), and I checked compression.

Cyl 1 - 150
Cyl 2 - 150
Cyl 3 - 140
Cyl 4 - 150
Cyl 5 - 160
Cyl 6 - 180
Cyl 7 - 140
Cyl 8 - 90

Cyl 8 isn't looking good but it still should start.

So after all the testing, I tried flooring it while cranking. It sputtered after a bit and then fired up. It ran ok, except the carb would backfire once in awhile while idling and whenever I would blip the throttle. I took #8 plug out to test compression again and after I got it all back together, it went back to just cranking and not starting.

Any ideas?

 

[Matthew Goeke]

you got the spark wires on the wrong cylinders, now im not 100% sure on this but i was told if you put them on wrong your car could catch fire.

 

[MWS1994]

you got the spark wires on the wrong cylinders, now im not 100% sure on this but i was told if you put them on wrong your car could catch fire.

I'm 100% sure I have the plugs on the right way. I also put new ones on and rechecked those.

So there is an update. The car is running now but it seems sluggish and backfires out the carb.

 

[Matthew Goeke]

I'm 100% sure I have the plugs on the right way. I also put new ones on and rechecked those.

So there is an update. The car is running now but it seems sluggish and backfires out the carb.

you must have the distributor on wrong, its something with the firing order so its either your distributor, or the engine timing

 

[MWS1994]

you must have the distributor on wrong, its something with the firing order so its either your distributor, or the engine timing

Yeah, I'm going to take the valve covers off tomorrow and see if there is anything weird.

 

[UNGN]

what did the #8 plug look like? Oily, carbony, clean or white?

Does the accelerator pump jets spray when you open up the throttle?

 

[MWS1994]

what did the #8 plug look like? Oily, carbony, clean or white?

Does the accelerator pump jets spray when you open up the throttle?

I'm not sure what #8 plug looked like, but as far as I remember all of them looked the same.

 

[pontiacgp]

are there no engine trouble codes ?

 

[airboatgreg]

You could have a burnt intake valve or a worn exhaust camshaft lobe on #8 cylinder

 

[Jeff L]

You could have a burnt intake valve or a worn exhaust camshaft lobe on #8 cylinder

I am thinking the same thing because of that low compression reading in #8 has me thinking something is just not right. When I have seen cars that had backfire in the carb, most of the time something with the timing or distributor was messed up.

Good luck with it. Playing detective can be frustrating at times.